CONTACT : SENTHIL-9500090804
TECHNOLOGY:POWERELECTRONICS,MATLAB
| S. No. | IEEE TITLE | ABSTRACT | IEEE YEAR |
| 1. | A Boundary-Mode Forward-Flyback Converter With an Efficient Active LC Snubber Circuit | Abstract—This paper describes a boundary-mode forwardflyback converter (BMFFC)with zero-voltage switching that is able to process power efficiently. The theoretical analysis and operating principle of the BMFFC are presented in detail. A nondissipative LC snubber that recycles energy to the input source is employed in order to suppress the voltage spike caused by the leakage inductance of the transformer. The relatively large snubber capacitor also significantly reduces turn-off loss. Following a detailed design procedure, a 200 W prototype with a 25—50 V dc input and 230 V dc output was constructed and tested in order to evaluate the performance of the BMFFC. | 2014 |
| 2. | A Cascaded Multilevel Inverter Based on Switched-Capacitor for High-Frequency AC Power Distribution System | Abstract—The increase of transmission frequency reveals more merits than low- or medium-frequency distribution among different kinds of power applications. High-frequency inverter serves as source side in high-frequency ac (HFAC) power distribution system (PDS). However, it is complicated to obtain a high-frequency inverter with both simple circuit topology and straightforward modulation strategy. A novel switched-capacitor-based cascaded multilevel inverter is proposed in this paper, which is constructed by a switched-capacitor frontend and H-Bridge backend. Through the conversion of series and parallel connections, the switchedcapacitor frontend increases the number of voltage levels. The output harmonics and the component counter can be significantly reduced by the increasing number of voltage levels. A symmetrical triangular waveform modulation is proposed with a simple analog implementation and low modulation frequency comparing with traditional multicarrier modulation. The circuit topology, symmetrical modulation, operation cycles, Fourier analysis, parameterdetermination, and topology enhancement are examined. An experimental prototype with a rated output frequency of 25 kHz is implemented to compare with simulation results. The experimental results agreed very well with the simulation that confirms the feasibility of proposed multilevel inverter. | 2014 |
| 3. | A Center Point Iteration MPPT Method With Application on the Frequency Modulated LLC Microinverter | Abstract—Maximum power point tracking (MPPT) is an essential technique to harvest PV power under varying environments. Perturb and observe (P&O) algorithms are the most broadly used MPPT due to their effectiveness and simplicity. However, it is difficult to balance the tracking speed and oscillation requirements in the conventional P&O with fixed perturb. Adaptive P&O techniques have been proposed as a solution to these problems. However, they are based on duty cycle modulation for conventional pulse width modulation converters. None of them deal with the variable frequencymodulation for resonant converters. In this paper, a center point iteration MPPT is proposed, with its variable perturb in frequency. The proposed scheme overcomes the drawbacks of conventional P&O with a simple calculation. Moreover, it is suitable for various power curves, especially the LLC microinverter power curves, which may confuse conventional MPPT algorithms. The effectiveness of the proposed MPPT method was verified in theory. A 300 W prototype was constructed, and the experimental results verified the effectiveness of the proposed center point iteration MPPT. An advanced version was also introduced in order to accelerate the tracking speed. | 2014 |
| 4. | A Critical Review of Recent Progress in Mid RangeWireless Power Transfer | Abstract—Starting from Tesla’s principles of wireless power transfer a century ago, this critical review outlines recent magneto inductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into 1) the maximum power transfer and 2) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the two-coil systems, the four-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the two-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the four-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (<50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay. | 2014 |
| 5. | A Current Balancing Scheme With High Luminous Efficacy for High-Power LED Lighting | Abstract—The imbalance in the currents of strings of LEDs will cause fast degradation or even failure in some LEDs. Such current imbalance should be avoided. To balance the common average current, a small duty cycle may necessitate a large LED turn-on current amplitude, which may cause temporal overheat and low luminous efficacy of the LEDs. This paper presents a current balancing method based on pulse-width modulation of a common bus voltage to each LED string to achieve the intended average current. An optimal feedback control scheme is proposed to maximize the duty cycles and minimize the bus voltage. As a result, at least one of the LED strings is operating at unity duty cycle. The analysis, implementation, and verification are detailed in this paper. | 2014 |
| 6. | A Four-level Hybrid-Clamped Converter With Natural Capacitor Voltage Balancing Ability | Abstract—This paper presents a novel four-level hybrid-clamped converter topology which is composed of eight switches and one flying capacitor per phase. The operating principle is introduced and phase-shifted pulse width modulation is used to control this converter. Adetailed analysis of the average currents through the flying capacitor and neutral points of the dc-link is presented. Based on the analysis, it can be concluded that the voltages across the flying capacitor and dc-link capacitors can be naturally balanced under ideal and steady-state condition. A low-power three-phase prototype is built up and experimental results are presented to validate the proposed topology and modulation method. | 2014 |
| 7. | A High Voltage Gain DC–DC Converter Integrating Coupled-Inductor and Diode–Capacitor Techniques | Abstract—The high-voltage gain converter is widely employed in many industry applications, such as photovoltaic systems, fuel cell systems, electric vehicles, and high-intensity discharge lamps. This paper presents a novel single-switch high step-up non isolated dc–dc converter integrating coupled inductor with extended voltage doubler cell and diode–capacitor techniques. The proposed converter achieves extremely large voltage conversion ratio with appropriate duty cycle and reduction of voltage stress on the power devices. Moreover, the energy stored in leakage inductance of coupled inductor is efficiently recycled to the output, and the voltage doubler cell also operates as a regenerative clamping circuit, alleviating the problem of potential resonance between the leakage inductance and the junction capacitor of output diode. These characteristics make it possible to design a compact circuit with high static gain and high efficiency for industry applications. In addition, the unexpected high-pulsed input current in the converter with coupled inductor is decreased. The operating principles and the steady state analyses of the proposed converter are discussed in detail. Finally, a prototype circuit is implemented in the laboratory to verify the performance of the proposed converter. | 2014 |
| 8. | A Hybrid Symmetrical Voltage Multiplier | Abstract—Voltage multiplier circuits are widely used in many high-voltage/low-current applications. A conventional symmetrical voltage multiplier (SVM) has much better performance, when compared with its half-wave counterpart. However, it requires a high-voltage transformer (HVT) with center-tapped secondary to perform its push–pull kind of operation. The design of an HVT with center-tapped secondary is relatively complex. This paper proposes a hybrid SVM (HSVM) for dc high-voltage applications. The multiplier is formed by cascading a diode-bridge rectifier and an SVM with diode-bridge rectifier as the first stage of multiplier. The proposed topology saves two high-voltage capacitors and requires only one secondary winding of HVT. Besides, it has lesser voltage drop and faster transient response at start-up, when compared with conventional SVM. The feasibility of the proposed HSVM is validated both by simulation and experimental results of a laboratory scaled-down prototype. | 2014 |
| 9. | A Low Complexity Control System for a Hybrid DC Power Source Based on Ultracapacitor Lead–Acid Battery Configuration | Abstract—A dc hybrid power source based on the combination of ultra capacitor and lead–acid battery is considered in this paper. The various control systems for such hybrid power source reported in the technical literature thus far are rather complex. A low complexity control system for such hybrid power source is proposed in this paper. The key feature of the proposed control system is its capability to maintain operation of the hybrid power source within all important operational limits. The proposed control system allows one to allocate the high-frequency current demands to the ultra capacitor and specify the current limits for both the battery and the ultra capacitor. It also maintains operation of the battery within its state of charge limits and the ultra capacitor voltage at a predefined value while charging the ultra capacitor from the battery rather than from the common dc bus. Presented experimental results verify the satisfactory operation of the power source utilizing the proposed control system. | 2014 |
| 10. | A Novel Transformer-less Adaptable Voltage Quadrupler DC Converter with Low Switch Voltage Stress | Abstract—In this paper, a novel transformer-less adjustable voltage quadrupler dc–dc converter with high-voltage transfer gain and reduced semiconductor voltage stress is proposed. The proposed topology utilizes input-parallel output-series configuration for providing a much higher voltage gain without adopting an extreme large duty cycle. The proposed converter cannot only achieve high step-up voltage gain with reduced component count but also reduce the voltage stress of both active switches and diodes. This will allow one to choose lower voltage rating MOSFETs and diodes to reduce both switching and conduction losses. In addition, due to the charge balance of the blocking capacitor, the converter features automatic uniform current sharing characteristic of the two interleaved phases for voltage boosting mode without adding extra circuitry or complex control methods. The operation principle and steady analysis as well as a comparison with other recent existing high step-up topologies are presented. Finally, some simulation and experimental results are also presented to demonstrate the effectiveness of the proposed converter. | 2014 |
| 11. | A Novel ZVT-ZCT-PWM Boost Converter | Abstract—In this study, a new boost converter with an active snubber cell is proposed. The active snubber cell provides main switch to turn ON with zero-voltage transition (ZVT) and to turn OFF with zero-current transition (ZCT). The proposed converter incorporating this snubber cell can operate with soft switching at high frequencies. Also, in this converter all semiconductor devices operate with soft switching. There is no additional voltage stress across the main and auxiliary components. The converter has a simple structure, minimum number of components, and ease of control as well. The operation principle and detailed steady-state analysis of the novel ZVT-ZCT-PWM boost converter are given. The presented theoretical analysis is verified exactly by a prototype of 100 kHz and 1 kW converter. Also, the overall efficiency of the new converter has reached a value of 97.8% at nominal output power. | 2014 |
| 12. | A Pulse Igniting Circuit for Electronic Ballast With the ZVS-QSW Converter | Abstract—In the paper, a novel pulse ignition circuit is proposed for electronic ballast with the zero-voltage-switching quasi-square wave (ZVS-QSW) converter; the voltage pulse of the proposed igniting circuit contains both a high frequency part and a low frequency part; the high frequency part made it easy to exit the gas in the ionization conduction state in the high-intensity discharge lamp, and the low frequency part makes it easy to lower the igniting potential and provides the continuous pulse energy. The circuit is with few components, low costs, high reliability, and easy to control. The circuit model is analyzed in detail and the influence of the circuit parameters on the pulse amplitude and width is given in this paper. The peak current is limited and the amplitude variation caused by the deviation of the parasitic capacitor for the transformer is restricted by the auxiliary inductor. The auxiliary inductor and the transformer parasitic capacitor form another resonant circuit. As a result, an igniting pulse sequence with two different frequencies is applied to the lamp and both pulse amplitude and width are guaranteed. In the laboratory, the circuit is used in a 70-W metal halide lamp electronic ballast with the ZVS-QSW converter, and the lamp can be ignited reliably. | 2014 |
| 13. | A Solar Power Generation System With a Seven-Level Inverter | Abstract—This paper proposes a new solar power generation system, which is composed of a dc/dc power converter and a new seven-level inverter. The dc/dc power converter integrates a dc–dc boost converter and a transformer to convert the output voltage of the solar cell array into two independent voltage sources with multiple relationships. This new seven-level inverter is configured using a capacitor selection circuit and a full-bridge power converter, connected in cascade. The capacitor selection circuit converts the two output voltage sources of dc–dc power converter into a three-level dc voltage, and the full-bridge power converter further converts this three-level dc voltage into a seven-level ac voltage. In this way, the proposed solar power generation system generates a sinusoidal output current that is in phase with the utility voltage and is fed into the utility. The salient features of the proposed seven-level inverter are that only six power electronic switches are used, and only one power electronic switch is switched at high frequency at any time. A prototype is developed and tested to verify the performance of this proposed solar power generation system. | 2014 |
| 14. | A Space-Vector Modulation Method for Common-Mode Voltage Reduction in Current-Source Converters | Abstract—The common-mode voltage (CMV) produced from a converter system is a source of many problems, e.g., in the motor drive system, CMV might appear at the neutral point of the motor stator windings with respect to the ground and induce destructive bearing current. Reduced CMV space-vector modulation (RCMV SVM) methods have been proposed in both voltage-source converter (VSC) and current-source converter (CSC) systems. The available RCMV SVMs reduce the CMV by avoiding using zero state vectors. However, this will lead to some negative effects, such as shrink of modulation index range, increase of switching frequencies, bipolar line-to-line voltage pulse patterns in VSCs, and power quality performance deterioration. In this paper, a RCMV SVM method for CSCs is proposed. By allowing the use of zero state vectors, the proposed RCMV SVM still produces much lower CMV. However, its other performance indices, such as switching frequency and harmonic performance, are unaffected and comparable to the conventional SVMs. The effectiveness of the proposed RCMV SVM for CSCs is verified in the simulations and experiments. | 2014 |
| 15. | A Switched Capacitor-Based Active-Network Converter With High Voltage Gain | Abstract—The voltage gain of traditional boost converter is limited due to the high current ripple, high voltage stress across active switch and diode, and low efficiency associated with large duty ratio operation. High voltage gain is required in applications, such as the renewable energy power systems with low input voltage. A high step-up voltage gain active-network converter with switched capacitor technique is proposed in this paper. The proposed converter can achieve high voltage gain without extremely high duty ratio. In addition, the voltage stress of the active switches and output diodes is low. Therefore, low voltage components can be adopted to reduce the conduction loss and cost. The operating principle and steady-state analysis are discussed in detail. A prototype with 20–40-V input voltage, 200-V output voltage, and 200-W output power has been established in the laboratory. Experimental results are given to verify the analysis and advantages of the proposed converter. | 2014 |
| 16. | A Three-Level Integrated AC–DC Converter | Abstract—In this paper, a new integrated three-level ac–dc converter is presented. The proposed converter integrates the operation of the boost power factor correction and the three-level dc–dc converter. The converter is made to operate with two independent controllers—an input controller that performs power factor correction and regulates the dc bus and an output controller that regulates the output voltage. The input controller prevents the dc-bus voltage from becoming excessive while still allowing a single-stage converter topology to be used. The paper explains the operation of the new converter in detail and discusses its features and a procedure for its proper design. Experimental results obtained from a prototype are presented to confirm the feasibility of the new converter. | 2014 |
| 17. | A Transformerless Grid-Connected Photovoltaic System Based on the Coupled Inductor Single-Stage Boost Three-Phase Inverter | Abstract—This letter presents a modulation technique for the modified coupled-inductor single-stage boost inverter (CL-SSBI)-based grid-connected photovoltaic (PV) system. This technique can reduce the system leakage current in a great deal and can meet the VDE0126-1-1 standard. To maintain the advantages of the impedance network, only a diode is added in the front of the original topology, to block the leakage current loop during the active vectors and open-zero vectors. On the other hand, the near state pulse width modulation (NSPWM) technique is applied with one-leg shoot-through zero vectors in order to reduce the leakage current through the conduction path in the duration of changing from and to open-zero vectors. Simultaneously, the leakage current caused by other transitions can also be reduced due to the fact that the magnitude of common-mode voltages is reduced. Simulation results of the transformer less PV system are presented in two cases: modified CL-SSBI modulated by maximum constant boost (MCB) control method and NSPWM. Experimental results for both CLSSBI topology modulated by the MCB control method and modified CL-SSBI topology modulated by NSPWM are also obtained to verify the accurateness of theoretical and simulation models. | 2014 |
| 18. | A Two-Mode Control Scheme With Input Voltage Feed-Forward for the Two-Switch Buck-Boost DC–DC Converter | Abstract—The two-switch buck-boost (TSBB) converter is suitable for wide input voltage applications. In order to achieve high efficiency over the entire input voltage range, the TSBB converter is operated in buck mode at high input voltage and boost mode at low input voltage. Such operation is called the two-mode control scheme. The objective of this paper is to propose an input voltage feed-forward (IVFF) method to reduce the influence of the input voltage disturbance on the output voltage. The small-signal models of the TSBB converter are built, and based on which, the IVFF functions under different operating modes of the TSBB converter are derived. The IVFF function in boost mode is simplified for easy implementation. The two-mode control scheme with IVFF compensation is then proposed for the TSBB converter, which realizes automatic selections of operating modes and the corresponding IVFF functions. Besides, nearly smooth switching between buck and boost modes is also guaranteed. For exhibiting the advantages of the proposed control scheme clearly, comparisons between the two-mode control with and without IVFF compensation have been presented in this paper, including the output signal of the voltage regulator and input-to-output voltage transfer function. Finally, a 250−500-V input, 360-V output, and 6-kW-rated power prototype is fabricated to validate the effectiveness of the proposed control scheme in the laboratory, and the experimental results show that the TSBB converter has an improved input transient response and high efficiency over the entire input voltage range with this proposed control scheme. | 2014 |
| 19. | A Two-Phase Interleaved Power Factor Correction Boost Converter With a Variation-Tolerant Phase Shifting Technique | Abstract—This paper presents a two-phase interleaved critical conduction mode (CRM) power factor correction boost converter with a variation-tolerant phase shifter (VTPS), which ensures accurate 180◦ phase shift between the two interleaved converters. A feedback loop similar to a phase-locked loop controls the amount of the phase shifting of the VTPS. The proposed VTPS has better immunity of process, supply, and temperature variations than the conventional phase shifter. A 320-W two-phase interleaved CRM boost converter prototype has been implemented, while the proposed VTPS and conventional interleaving phase shifter can be selectively applied to compare the performance of the proposed technique with the conventional one. Experimental results show that the two-phase interleaved CRM boost converter has better performance with the proposed VTPS. The proposed VTPS circuit can be applied to any type of interleaved switching power converter. | 2014 |
| 20. | A Unified Control Strategy for Three-Phase Inverter in Distributed Generation | Abstract—This paper presents a unified control strategy that enables both islanded and grid-tied operations of three-phase inverter in distributed generation, with no need for switching between two corresponding controllers or critical islanding detection. The proposed control strategy composes of an inner inductor current loop, and a novel voltage loop in the synchronous reference frame. The inverter is regulated as a current source just by the inner inductor current loop in grid-tied operation, and the voltage controller is automatically activated to regulate the load voltage upon the occurrence of islanding. Furthermore, the waveforms of the grid current in the grid-tied mode and the load voltage in the islanding mode are distorted under nonlinear local load with the conventional strategy. And this issue is addressed by proposing a unified load current feed forward in this paper. Additionally, this paper presents the detailed analysis and the parameter design of the control strategy. Finally, the effectiveness of the proposed control strategy is validated by the simulation and experimental results. | 2014 |
| 21. | A Zero-Voltage Switching Three-Phase Inverter | Abstract—A new modulation scheme for the active clamping zero-voltage switching (ZVS) inverter is proposed. With the proposed modulation scheme, the inverter can realize ZVS operation in all switching devices and can remarkably suppress the reverse recovery current in insulated-gate bipolar transistor’s anti parallel diodes as well. All the switches can operate at a fixed frequency in the new modulation scheme. Also, with the new modulation scheme, the ZVS inverter has some voltage boost capability, which is suitable for renewable energy generation. The inverter can achieve ZVS in all the switches under the grid current power factor angle from zero to ±π/6. The soft-switching condition of this inverter is analyzed. The operation principal and design guideline are described in detail. The previous theory is verified in a 30-kW inverter prototype. | 2014 |
| 22. | Active Islanding Detection for Multiple Parallel-Connected Inverter-Based Distributed Generators Using High-Frequency Signal Injection | Abstract—This paper proposes a method for islanding detection in micro grids with multiple parallel-connected inverters using high-frequency signal injection. In the proposed method, a master inverter injects the high-frequency signal which is used by the rest of inverters for islanding detection, with two distinguishing features: 1) The slave inverters work in a high-frequency current cancellation mode, what prevents interference and 2) in case of master failure or significant changes in the grid, the remaining inverters will dynamically reassign roles, the new master inverter being self-selected, based on a deterministic performance criteria and without the need of communications. | 2014 |
| 23. | An FPGA-Based Gain-Scheduled Controller for Resonant Converters Applied to Induction Cooktops | Abstract—Domestic induction heating appliances have become popular due to their advantages such as efficiency, fast heating, cleanliness, and safety. In order to achieve high efficiency, induction cook tops usually features resonant converters in which the inductor-vessel system is a part of the resonant tank. Thus, the inductor-vessel system impedance sets the point of operation of the power converter. Due to the variability of the load with multiple parameters such as temperature, geometry, and material, the resonant converter has to work with highly varying operating conditions. When designing a classical controller, the controller gain is selected to assure the system stability in the whole range of operation and for a large amount of vessels. This study proposes an FPGA-based gain scheduled controller which makes use of the information of the modulation parameters and an online impedance identification system. As a result, the proposed controller significantly improves the converter dynamic response, improving the performance and safety operation of the power converter. The proposed control algorithm has been experimentally verified using a domestic induction heating prototype, proving the feasibility of this proposal. | 2014 |
| 24. | An Improved Droop Control Method for DC Microgrids Based on Low Bandwidth Communication With DC Bus Voltage Restoration and Enhanced Current Sharing Accuracy | Abstract—Droop control is the basic control method for load current sharing in dc microgrid applications. The conventional dc droop control method is realized by linearly reducing the dc output voltage as the output current increases. This method has two limitations. First, with the consideration of line resistance in a droop controlled dc microgrid, since the output voltage of each converter cannot be exactly the same, the output current sharing accuracy is degraded. Second, the dc-bus voltage deviation increases with the load due to the droop action. In this paper, in order to improve the performance of the dc microgrid operation, a low-bandwidth communication (LBC)-based improved droop control method is proposed. In contrast with the conventional approach, the control system does not require a centralized secondary controller. Instead, it uses local controllers and the LBC network to exchange information between converter units. The droop controller is employed to achieve independent operation, and the average voltage and current controllers are used in each converter to simultaneously enhance the current sharing accuracy and restore the dc bus voltage. All of the controllers are realized locally, and the LBC system is only used for changing the values of the dc voltage and current. Hence, a decentralized control scheme is accomplished. The simulation test based on MATLAB/Simulink and the experimental validation based on a 2 × 2.2 kW prototype were implemented to demonstrate the proposed approach. | 2014 |
| 25. | An Improved ZVT–ZCT PWM DC–DC Boost Converter With Increased Efficiency | Abstract—A new active snubber cell is proposed for a dc–dc boost converter. Zero voltage transition (ZVT) turn on and zero current transition (ZCT) turn off are provided by this active snubber cell. There is no extra current or voltage stresses on the main switch. Also, zero current switching (ZCS) turn on and ZCT turn off are provided for the auxiliary switch. Although there is no extra voltage stress on the auxiliary switch, a current stress is present. However, auxiliary switch current stress is decreased by coupling inductance. The coupling inductance transfers the part of the current stress to the output load according to the transform ratio. In this paper, the ZVT–ZCT PWM dc–dc boost converter’s steadystate analysis is proposed for one switching cycle. Experimental application and theoretical analysis are proved by 300 W prototype with 100 kHz switching frequency. As a result, an improved ZVT–ZCT PWMboost converter reaches 98.7% total efficiency at full load with lowered current stress. | 2014 |
| 26. | Analysis and Implementation of an Improved Flyback Inverter for Photovoltaic AC Module Applications | Abstract—Flyback inverter has the advantages such as compact conformation, simple control loop, electric isolation, high step-up ratio, high efficiency, etc., therefore is an attractive solution for photovoltaic ac module applications. In this topology, BCM is more preferred compared to DCM and CCM, because of its higher power level, higher efficiency and wider switching frequency bandwidth. However, the control of BCM is more complicated due to its variable switching frequency. This also leads to the difficulty to get the accurate mathematical model between the output current iout and the reference current iref , which has a great influence on the THD of iout . This paper analyzes and proposes a mathematical model between iout and iref in BCM through theoretical derivation, and proposes a novel control strategy to generate the reference current that can decrease THD of output current. Meanwhile the realization of MPPT based on the mathematical model is also investigated. Finally, simulation and experiment results based on an improved fly back-inverter prototype are presented, which validates the proposed mathematical model and the control strategy. | 2014 |
| 27. | Analysis of Unified Output MPPT Control in Subpanel PV Converter System | Abstract—Photovoltaic (PV) systems frequently suffer disproportionate impacts on energy production due to mismatch cases. To remedy this, academia proposed a distributed max power point tracking (MPPT) solution and has been implemented commercially. Taking the trend of the “distributed MPPT” concept a step further, this paper discusses and analyzes an MPPT converter that connects to each PV cell string, called a subpanel MPPT converter (SPMC), to better address the real-world mismatch issues. The SPMC system with a unified output MPPT control structure is also proposed in order to reduce the cost and simplify the distributed MPPT system. The proposal saves A/D units, current sensors, and MPPT controllers on the premise of guaranteeing that the SPMC is working on its optimal maximum power point regardless of th mismatch case. This is favorable for the further integration and makes the whole SPMC system less expensive and easier to realize. Finally, the effectiveness of the proposal is confirmed experimentally. | 2014 |
| 28. | Asymmetrical Grid Fault Ride-Through Strategy of Three-Phase Grid-Connected Inverter Considering Network ImpedanceImpact in Low-Voltage Grid | Abstract—This letter presents a new control strategy of three phase grid-connected inverter for the positive sequence voltage recovery and negative sequence voltage reduction under asymmetrical grid faults. Unlike the conventional control strategy based on an assumption that the network impedance is mainly inductive, the proposed control strategy is more flexible and effective by considering the network impedance impact, which is of great importance for the high penetration of grid-connected renewable energy systems into low-voltage grids. The experimental tests are carried out to validate the effectiveness of the proposed solution for the flexible voltage support in a low-voltage grid, where the network impedance is mainly resistive. | 2014 |
| 29. | Class-D Zero-Current-Switching Rectifier as Power-Factor Corrector for Lighting Applications | Abstract—An analysis and design of a zero-current-switching (ZCS) Class-D current-source driven rectifier for the lighting applications is presented, which is one of the resonant rectifiers as a power-factor corrector to improve a poor power-factor and high line current harmonic of a single-stage converter. A high power factor is achieved by the utilization of output characteristics of a Class-D ZCS rectifier, which is inserted between the front-end bridge rectifier and the bulk-filter capacitor. The conduction angle of the bridge rectifier diode current was increased and a low-line current harmonic and a power-factor near unity can be obtained. The design procedure is based on the principle of the Class-D ZCS rectifier, which also ensures more accurate results and the proposed scheme provides a high efficiency and amore systematic and feasible analysis methodology. The active switches can be operated under the soft-switching condition. The validity of this approach was confirmed by simulation and experimental results. | 2014 |
| 30. | Classification and Comparative Evaluation of PV Panel-Integrated DC–DC Converter Concepts | Abstract—The strings of photovoltaic panels have a significantly reduced power output when mismatch between the panels occurs, as, e.g., caused by partial shading. With mismatch, either the panel integrated diodes are bypassing the shaded panels if the string is operated at the current level of the un shaded panels, or some power of the un shaded panels is lost if the string current is reduced to the level of the shaded panels. With the implementation of dc–dc converters on panel level, the maximum available power can be extracted from each panel regardless of any mismatch. In this paper, different concepts of PV panel-integrated dc–dc converters are presented and their suitability for panel integration is evaluated. The buck–boost converter is identified as the most promising concept and an efficiency/power density (η-ρ) Pareto optimization of this topology is shown. Based on the optimization results, two 275W converter prototypes with either Silicon MOSFETs with a switching frequency of 100 kHz or gallium nitride FETs with a switching frequency of 400 kHz are designed for an input voltage range of 15 to 45 V and an output voltage range of 10 to 100 V. The theoretical considerations are verified by efficiency measurements which are compared to the characteristics of a commercial panel-integrated converter. | 2014 |
| 31. | Common-Mode and Differential-Mode Active Damping for PWM Rectifiers | Abstract—Modern pulse-width-modulated (PWM) rectifiers use LCL filters that can be applied in both the common mode and differential mode to obtain high-performance filtering. Interaction between the passive L and C components in the filter leads to resonance oscillations. These oscillations need to be damped either by the passive damping or active damping. The passive damping increases power loss and can reduce the effectiveness of the filter. Methods of active damping, using control strategy, are lossless while maintaining the effectiveness of the filters. In this paper, an active damping strategy is proposed to damp the oscillations in both line-to-line and line-to-ground. An approach based on pole placement by the state feedback is used to actively damp both the differential- and common-mode filter oscillations. Analytical expressions for the state-feedback controller gains are derived for both continuous and discrete-time model of the filter. Tradeoff in selection of the active damping gain on the lower order power converter harmonics is analyzed using a weighted admittance function. Experimental results on a 10-kVAlaboratory prototype PWM rectifier are presented. The results validate the effectiveness of the active damping method, and the tradeoff in the settings of the damping gain. | 2014 |
| 32. | Comparative Performance Analysis of High Density and Efficiency PFC Topologies | Abstract—In this paper, the efficiency and power factor performance of improved power factor correction (PFC) topologies suitable for a high density and efficient design are compared. Several topologies, including a conventional average current mode control boost PFC, an interleaved boost PFC, a back-to-back bridgeless boost PFC, and a semi-bridgeless boost PFC, are assessed through loss analysis and simulation using whole height 1 U and 2 kW class prototypes. Based on this, an optimal topology is selected for which an additional comparative analysis involving input line measure improvement control is conducted. The results of these experiments can be adapted for use in the circuit selection of high performance converters with power factor improvement circuits. | 2014 |
| 33. | Control Strategy of Three-Phase Battery Energy Storage Systems for Frequency Support in Microgrids and with Uninterrupted Supply of Local Loads | Abstract—Frequency control in autonomous micro grids (MG) with high penetration of renewable energy sources represents a great concern to ensure the system stability. In this regard, this paper presents an enhanced control method for battery energy storage systems (BESS) to support the frequency of MG and with the ability of disconnecting from the MG to supplying in the island mode a local consumer. A frequency controller, combining a conventional droop control with an inertia emulation function, governs the BESS active power transfer during the primary frequency control level. The BESS may also provide voltage support in the point of common coupling with the MG. Moreover, the proposed BESS may compensate, partially or totally, the power absorbed by the local loads in order to improve the MG frequency response. When the MG power quality worsens below a certain level, in terms of voltage and frequency, the BESS detaches from the MG and continues to operate islanded. The reconnection is accomplished following a smoothly resynchronization of the local voltage with the MG, without disturbing the local loads supply. Additionally, this paper also discusses about the aspects related to the BESS management and its integration within the proposed system. The simulation and experimental results assess the feasibility of the proposed control solutions. | 2014 |
| 34. | Design and Implementation of a High-Efficiency Multiple-Output Resonant Converter for Induction Heating Applications Featuring Wide Bandgap Devices | Abstract—Efficiency is a key design parameter when designing the power converters for domestic induction heating applications, since it determines not only the environmental impact of the power converter but also its final performance and reliability. In this paper, he design of high-efficiency converters for induction heating applications is discussed, focusing on the advantages of using wide band gap devices. As a conclusion, a multiple-output boost resonant ac–ac converter is proposed, significantly improving current state of- the-art efficiency and achieving a reduced component-count solution for multiple-load systems. The proposed converter has been tested through a dual-output boost resonant inverter for domestic induction heating applications. The design procedure is detailed, including the design of an optimized gate drive circuit for this application. Experimental results show significant improvements in efficiency in the whole operating range, and an accurate output power control, proving the benefits and feasibility of the proposed SiC-based converter. | 2014 |
| 35. | Design and Implementation of a High-Power-Factor LED Driver With Zero-Voltage Switching-On Characteristics | Abstract—This paper proposes a novel light-emitting diode (LED) driver consisting of a buck-boost converter and a buck converter. Each converter adopts a power MOSFET as the active switch. With no need to use any auxiliary switches or snubber circuits, both active switches can operate at zero-voltage switching on (ZVS) by freewheeling the inductor current of the converters to flow through the intrinsic diodes of the MOSFETS. The buck-boost converter is operated at discontinuous-conduction mode (DCM) to perform the function of power-factor correction to ensure almost unity power factor at the input line. The buck converter steps down the output voltage of the buck-boost converter to drive LEDs. It could be designed to operate at either DCM or continuous conduction mode. The detailed circuit operations and analysis are provided. A prototype 60-W LED driver was built and tested. Experimental results show that the switching losses can be effectively reduced by operating the active switches at ZVS. The measured power factor and circuit efficiency are as high as 0.99% and 93%, respectively. | 2014 |
| 36. | Design and Implementation of Energy Management System With Fuzzy Control for DC Microgrid Systems | Abstract—This paper presents the design and implementation of an energy management system (EMS) with fuzzy control for adc microgrid system. Modeling, analysis, and control of distributed power sources and energy storage devices with MATLAB/Simulink are proposed, and the integrated monitoring EMS is implemented with Lab VIEW. To improve the life cycle of the battery, fuzzy control manages the desired state of charge. The RS-485/ZigBee network has been designed to control the operating mode and to monitor the values of all subsystems in the dc microgrid system. | 2014 |
| 37. | Determining the Value of DC-Link Capacitance to Ensure Stable Operation of a Three-Phase Photovoltaic Inverter | Abstract—Grid interfacing of photovoltaic generators using three-phase inverters offers the advantage of constant power flow allowing smaller capacitance values to be used in the dc-link compared to single-phase inverters. Electrolytic capacitors, used in the dc-link, are often considered to decrease reliability. Reliability could be improved by using film capacitors, but their usage is limited by high cost and low capacitance. Much research has been done to minimize the dc-link capacitance value, particularly, in the field of drives and wind turbines. It has been shown that motor drive in regenerative mode contains a right-half-plane (RHP) pole in its control dynamics having a significant effect on the required dc-link capacitance. The RHP pole can cause instability as has been observed in wind turbine applications. Photovoltaic inverters have been reported to suffer from instability of the dc-link-voltage control, but the origin of the observed problems is poorly understood. This paper shows explicitly that an RHP pole is present in the control dynamics also in photovoltaic inverters affecting the minimum required dc-link capacitance. The paper proposes a minimum value for the dc-link capacitance that is required for stable operation. Design rules are given for single- and two-stage inverters. Moreover, it is shown that a source having constant power output effectively removes the RHP pole from the dc-link-voltage control dynamics. | 2014 |
| 38. | Development of an FPGA-Based SPWM Generator for High Switching Frequency DC/AC Inverters | Abstract—The digital implementations of Sinusoidal Pulse Width Modulation (SPWM) generators have dominated over their counterparts based on analog circuits. In this paper, an FPGA based SPWM generator is presented, which is capable to operate at switching frequencies up to 1 MHz (requiring FPGA operation at 100–160 MHz), thus it is capable to support the high switching frequency requirements of modern single-phase dc/ac power converters. The proposed design occupies a small fraction of a medium-sized FPGA and, thus, can be incorporated in larger designs. Additionally, it has a flexible architecture that can be tuned to a variety of single-phase dc/ac inverter applications. The post layout simulation and experimental results confirm that compared to the past-proposed SPWM generation designs, the SPWM generator presented in this paper exhibits much faster switching frequency, lower power consumption, and higher accuracy of generating the desired SPWM waveform. | 2014 |
| 39. | Digital DCM Detection and Mixed Conduction Mode Control for Boost PFC Converters | Abstract—This paper presents a novel mixed conduction mode (MCM) digital controller with a digital signal processor (DSP)- based discontinuous conduction mode (DCM) detection technique to realize total harmonic distortion (THD) and power factor improvements in boost power factor correction (PFC) converters operating in both continuous conduction mode (CCM) and DCM during a single ac line half-cycle. By using the integrated comparators found on many DSPs, simplification and cost-reductions over existing DCM and zero-current detection methods are made possible. Additionally, performance improvements over a conventional CCM digital control technique are possible with simple software modification, and can be extended to existing boost PFC converter designs provided a compatible DSP is present. At an output power of 98 W, an experimental 650 W boost PFC converter operating in the MCM controlled by a TMS320F28035 provides a THD reduction of 40.2% and power factor improvement of 1.5% over a conventional digital controller. | 2014 |
| 40. | Direct AC–AC Resonant Boost Converter for Efficient Domestic Induction Heating Applications | Abstract—Domestic induction heating (IH) is currently the technology of choice in modern domestic applications due to its advantages regarding fast heating time, efficiency, and improved control. New design trends pursue the implementation of new cost-effective topologies with higher efficiency levels. In order to achieve this aim, a direct ac–ac boost resonant converter is proposed in this paper. The main features of this proposal are the improved efficiency, reduced component count, and proper output power control. A detailed analytical model leading to closed-form expressions of the main magnitudes is presented, and a converter design procedure is proposed. In addition, an experimental prototype has been designed and built to prove the expected converter performance and the accurateness of the analytical model. The experimental results are in good agreement with the analytical ones and prove the feasibility of the proposed converter for the IH application. | 2014 |
| 41. | Direct Grid Current Control of LCL-Filtered Grid-Connected Inverter Mitigating Grid Voltage Disturbance | Abstract—A direct grid current control strategy for LCL-filtered grid-connected inverters is proposed in this paper. The conventional current control strategies are analyzed and compared, and then the necessity of direct grid current control is presented to mitigate the grid voltage disturbance. In the proposed control strategy, the virtual resistance based on the capacitance current is used to realize active damping, zero compensation is brought in to enhance the stability, and the proportional resonant (PR) controller under two-phase static coordinate is designed to track the ac reference current as well as to avoid the strong coupling brought by the coordinate transformation. Under the distortion grid voltage, the PR plus harmonic compensator (PR+HC) structure is adopted to restrain the distortion of the grid current. Finally, the proposed control strategy is verified by the experimental results. | 2014 |
| 42. | Direct Voltage Control of DC–DC Boost Converters Using Enumeration-Based Model Predictive Control | Abstract—This paper presents a model predictive control (MPC) approach for dc–dc boost converters. A discrete-time switched nonlinear (hybrid) model of the converter is derived, which captures both the continuous and the discontinuous conduction mode. The controller synthesis is achieved by formulating an objective function that is to be minimized subject to the model dynamics. The proposed MPC strategy, utilized as a voltage-mode controller, achieves regulation of the output voltage to its reference, without requiring a subsequent current control loop. Furthermore, a state estimation scheme is implemented that addresses load uncertainties and model mismatches. Simulation and experimental results are provided to demonstrate the merits of the proposed control methodology, which include a fast transient response and a high degree of robustness. | 2014 |
| 43. | DTC of B4-Inverter-Fed BLDC Motor Drives With Reduced Torque Ripple During Sector-to-Sector Commutations | Abstract—The paper deals with the direct torque control (DTC) of brushless DC (BLDC) motor drives fed by four-switch inverters (also known as B4-inverters) rather than six-switch inverters (also known as B6-inverters) in conventional drives. The B4-inverter could be regarded as a reconfigured topology of the B6-inverter in case of a switch/leg failure which represents a crucial reliability benefit for many applications especially in electric and hybrid propulsion systems. The principle of operation of the BLDC motor is firstly recalled considering both cases of B6- and B4-inverters in the armature, with emphasis on the two- and three-phase conduction modes. Then, the DTC of B4-inverter-fed BLDC motor drives is treated considering three strategies, such as: 1) DTC-1: a strategy inspired from the one intended to B6-inverter-fed BLDC motor drives; 2) DTC-2: a strategy that considers a dedicated vector selection sub table in order to independently control the torques developed by the phases connected to the B4-inverter legs during their simultaneous conduction; and 3) DTC-3: a proposed strategy that eliminates the torque dips penalizing DTC-2 during sector-to sector commutations. Following the design of the corresponding vector selection tables and sub tables (if any), an experimentally based comparative study of the three DTC strategies is carried out considering, in the first step, the BLDC motor steady-state operation under DTC-1 and DTC-3. Then, the comparison is extended to the BLDC motor features during sector-to-sector commutations, underDTC-2 andDTC-3. The experimental results clearly validate the predicted performance of the proposed DTC strategy. | 2014 |
| 44. | Dual Angle Control for Line-Frequency-Switched Static Synchronous Compensators Under System Faults | Abstract—Voltage-sourced converter (VSC)-based static synchronous compensators (STATCOMs) are used for voltage regulation in transmission and distribution systems. Unlike PWM controlled STATCOMs, angle-controlled STATCOMs are switched at line frequency to limit the system losses. In recent years, angle controlled STATCOMs have been deployed by utilities for the purpose of transmission system voltage regulation, voltage stability improvement, and increasing operational functionality. Despite the superior feature on voltage waveform quality and efficiency, the practical angle-controlled STATCOMs suffer from the over current (and trips) and possible saturation of the interfacing transformers caused by negative sequence current during unbalanced conditions and faults in the utility. This paper specifically proposes a control structure to improve the angle-controlled STATCOMs performance under unbalanced conditions and faults. The main improvement is a substantial decrease in the negative sequence current and dc-link voltage oscillations under power system faults by the proposed control. This eliminates the need to redesign the STACOM power components to operate under fault current and dc link voltage oscillations. The proposed control structure is designed based on adding appropriate oscillations to the conventional angle controller output that is the control angle by which the VSC voltage vector leads/lags the line voltage vector. Since this control structure uses two angles for controlling the VSC output voltage, it is called dual angle control (DAC). PSCAD/EMTDC and experimental results verify the validity of the proposed control structure under unbalanced system conditions and faults. The experiments were conducted on a transient network analyzer, a unique hardware-based flexible ac transmission system simulator which was designed to study system faults and transients for a 2 × 100 MVA STATCOM field installation. | 2014 |
| 45. | Ga-Optimized Parameters of Sliding-Mode Controller Based on Both Output voltage and Input Current With an Application in the PFC of AC/DC Converters | Abstract—In this work, analysis and optimization of sliding mode controller parameters are treated, in order to govern a static power converter. In this case, an ac–dc boost power factor corrector is used; generally, these kinds of converters are applied to obtain a power factor near to unity. Advantage that the designed controller can give is the improvement of dynamic and static performances in cases of large disturbances. Simple sliding surface contains, in most cases, only one variable; in this study, analyzed surface includes two variables, which are continuous output voltage and rectified sinusoidal input current; the benefit of this surface is getting react against various disturbances, as be at the input power parameters, or the value of the load. The whole controller and converter is tested by simulation and experimentally for steady-state and transient responses. | 2014 |
| 46. | H6 Transformerless Full-Bridge PV Grid-Tied Inverters | Abstract—Transformer less inverters are widely used in grid-tied photovoltaic (PV) generation systems, due to the benefits of achieving high efficiency and low cost. Various transformer less inverter topologies have been proposed to meet the safety requirement of leakage currents, such as specified in the VDE-4105 standard. In this paper, a family of H6 transformer less inverter topologies with low leakage currents is proposed, and the intrinsic relationship between H5 topology, highly efficient and reliable inverter concept (HERIC) topology, and the proposed H6 topology has been discussed as well. One of the proposed H6 inverter topologies is taken as an example for detail analysis with operation modes and modulation strategy. The power losses and power device costs are compared among the H5, th HERIC, and the proposed H6 topologies. A universal prototype is built for these three topologies mentioned for evaluating their performances in terms of power efficiency and leakage currents characteristics. Experimental results show that the proposed H6 topology and the HERIC achieve similar performance in leakage currents, which is slightly worse than that of the H5 topology, but it features higher efficiency than that of H5 topology. | 2014 |
| 47. | High Efficiency Dual-Mode Current Modulation Method for Low-Power DC/AC Inverters | Abstract—Boundary conduction mode (BCM) zero voltage switching (ZVS) current control is a promising soft switching method for micro inverter applications. In this letter, different BCM ZVS current control modulation schemes are compared based on power losses breakdown, switching frequency range, and current quality. Compared to continuous conduction mode current control, BCM ZVS control decreases MOSFET switching losses and filter inductor conduction losses but increases MOSFET conduction losses and inductor core losses. Based on the loss analysis, a dual-mode current modulation method combining ZVS and zero current switching schemes is proposed to improve the efficiency of the micro inverter. The experimental results show that by using this proposed current modulation scheme, higher efficiency of 0.5% can be achieved with no additional cost for a 400-W three-phase micro inverter. | 2014 |
| 48. | High Gain Soft-Switching Bidirectional DC–DC Converter for Eco-Friendly Vehicles | Abstract—This paper proposes a non isolated soft-switching bidirectional dc–dc converter suitable for high step-up and step-down applications. The proposed converter can achieve zero voltage switching turn on of all switches and zero-current-switching turn off of some switches in continuous conduction mode in both forward and reverse modes. An optimized switching strategy is presented to minimize switch current rating and achieve soft switching in wider range. An intermediate switching pattern is introduced to carry out seamless mode change. Experimental results from a 5-kW prototype are provided to validate the proposed concept. | 2014 |
| 49. | High Power Density Series Resonant Inverter Using an Auxiliary Switched Capacitor Cell for Induction Heating Applications | Abstract—This paper proposes a unique topology of voltage-fed high-frequency series load resonant inverter with a lossless snubber capacitor and an auxiliary switched cell for induction heating appliances. The main objective of this paper is to demonstrate how high power density can be achieved by including a switched capacitor cell with the capacitor-clamped half-bridge zero voltage switching high-frequency inverter circuit using the PWM control scheme. The operation principle of the proposed inverter circuit is based upon an asymmetrical duty cycle pulse width modulated (PWM) control scheme. The operating performances of high-frequency ac regulation and power conversion efficiency characteristics are shown through experiments with their soft-switching operating ranges. | 2014 |
| 50. | High Step-Up Interleaved Converter With Built-In Transformer Voltage Multiplier Cells for Sustainable Energy Applications | Abstract—In this paper, the built-in transformer voltage multiplier cell is inserted into each phase of the conventional interleaved boost converter to provide additional control freedom for the voltage gain extension without extreme duty cycle. The voltage multiplier cell is only composed of the built-in transformer windings, diodes and small capacitors. And additional active switches are not required to simplify the circuit configuration. Furthermore, the switch voltage stress and the diode peak current are also minimized due to the built-in transformer voltage multiplier cells to improve the conversion efficiency. Moreover, there is no reverse-recovery problem for the clamp diodes and the reverse recovery current for the regenerative and output diodes are controlled by the leakage inductance of the built-in transformer to reduce the relative losses. In addition, the switch turn-off voltage spikes are suppressed effectively by the ingenious and inherent passive clamp scheme and zero current switch (ZCS) turn-on is realized for the switches, which can enhance the power device reliability. Finally, a 40 V-input 380 V-output 1 kW prototype is built to demonstrate the clear advantages of the proposed converter. | 2014 |
| 51. | High-Voltage Gain Boost Converter Based on Three-State Commutation Cell for Battery Charging Using PV Panels in a Single Conversion Stage | Abstract—This paper presents a novel high-voltage gain boost converter topology based on the three-state commutation cell for battery charging using PV panels and a reduced number of conversion stages. The presented converter operates in zero-voltage switching (ZVS) mode for all switches. By using the new concept of single-stage approaches, the converter can generate a dc bus with a battery bank or a photovoltaic panel array, allowing the simultaneous charge of the batteries according to the radiation level. The operation principle, design specifications, and experimental results from a 500-W prototype are presented in order to validate the proposed structure. | 2014 |
| 52. | I2 Average Current Mode Control for Switching Converters | Abstract—Constant frequency average current mode (ACM) control is a widely used control scheme for converters requiring precise current control. However, its transient response is relatively slow, while the switching loss and driving loss significantly diminish the light load efficiency. To solve these issues, the I2 control ACM is proposed. By combining the fast direct current feedback and integral feedback, the I2 control achieves both wide bandwidth and accurate current control. As a particular embodiment of this concept, by adopting constant on-time modulation, constant on-time I2 control needs no artificial ramp, and has a fast dynamic response. Moreover, due to the decrease of the switching frequency, constant on-time I2 control improves the efficiency in discontinuous conduction mode. The concept of I2 control can be extended to other modulations. A small-signal model using the describing function- based equivalent circuit model is proposed. The model is accurate up to 1/2 switching frequency. Based on the model, the design guidelines are discussed. The proposed control is verified with simulation and hardware measurement results. | 2014 |
| 53. | Integrated Inverter/Converter Circuit and Control Technique of Motor Drives With Dual-Mode Control for EV/HEV Applications | Abstract—A new integrated circuit for motor drives with dual mode control for EV/HEV applications is proposed. The proposed integrated circuit allows the permanent magnet synchronous motor to operate in motor mode or acts as boost inductors of the boost converter, and thereby boosting the output torque coupled to the same transmission system or dc-link voltage of the inverter connected to the output of the integrated circuit. In motor mode, the proposed integrated circuit acts as an inverter and it becomes a boost-type boost converter, while using the motor windings as the boost inductors to boost the converter output voltage. Moreover, a new control technique for the proposed integrated circuit under boost converter mode is proposed to increase the efficiency. The proposed control technique is to use interleaved control to significantly reduce the current ripple and thereby reducing the losses and thermal stress under heavy-load condition. In contrast, single phase control is used for not invoking additional switching and conduction losses under light-load condition. Experimental results derived from digital-controlled 3-kW inverter/converter using digital signal processing show the voltage boost ratio can go up to 600Wto 3 kW. And the efficiency is 93.83% under full-load condition while keeping the motor temperature at the atmosphere level. These results fully confirm the claimed merits for the proposed integrated circuit. | 2014 |
| 54. | Isolated High Step-Up DC–DC Converter With Low Voltage Stress | Abstract—Fuel cell stacks and photovoltaic panels generate rather low dc voltages and these voltages need to be boosted before converted to ac voltage. Therefore, high step-up ratio dc– dc converters are preferred in renewable energy systems. A new Z-source-based topology that can boost the input voltage to desired levels with low duty ratios is proposed in this paper. The topology utilizes coupled inductor. The leakage inductance energy can efficiently be discharged. Since the device stresses are low in this topology, low-voltage MOSFETs with small RDS (on) values can be selected to reduce the conduction loss. These features improve the converter efficiency. Also, the converter has a galvanic steady-state analysis of continuous and discontinuous conduction modes are discussed in detail. Finally, experimental results are given for a prototype converter that converts 25 V dc to 400 V dc at various power levels with over 90% efficiency to verify the effectiveness of the theoretical analysis. | 2014 |
| 55. | Magnetic Integration of the LCL Filter in Grid-Connected Inverters | Abstract—This letter investigates the magnetic integration of the LCL filter in grid-connected inverters. By sharing an ungapped core and arranging the windings properly, the fundamental fluxes generated by the two inductors of an LCL filter cancel out mostly in the common core. Thus, the common core with low flux level can be dramatically reduced. Although the reluctance of the common core can hardly be zero, which implies an inevitable coupling between the integrated inductors, the proposed magnetic integration scheme is still attractive if the cross-section area and magnetic material of the common core are made reasonable. Experimental results from both single-phase and three-phase grid-connected inverters verify the effectiveness of the proposed method. | 2014 |
| 56. | Maximum Power Point Tracking Using Model Reference Adaptive Control | Abstract—This paper proposes an adaptive control architecture for maximum power point tracking (MPPT) in photovoltaic systems. MPPT technologies have been used in photovoltaic systems to deliver the maximum available power to the load under changes of the solar insolation and ambient temperature. To improve the performance of MPPT, this paper develops a two-level adaptive control architecture that can reduce complexity in system control and effectively handle the uncertainties and perturbations in the photovoltaic systems and the environment. The first level of control is ripple correlation control (RCC), and the second level is model reference adaptive control (MRAC). By decoupling these two control algorithms, the system achieves MPPT with overall system stability. This paper focuses mostly on the design of the MRAC algorithm, which compensates the under damped characteristics of the power conversion system. The original transfer function of the power conversion system has time-varying parameters, and its step response contains oscillatory transients that vanish slowly. Using the Lyapunov approach, an adaption law of the controller is derived for the MRAC system to eliminate the under damped modes in power conversion. It is shown that the proposed control algorithm enables the system to converge to the maximum power point in milliseconds. | 2014 |
| 57. | Mode-Adaptive Decentralized Control for Renewable DC Microgrid With Enhanced Reliability and Flexibility | Abstract—A mode-adaptive decentralized control strategy is proposed for the power management of a dc microgrid with multiple renewable distributed generators and energy storage systems. In the presented solution, the dc bus voltage signal is used not only to enable power sharing among different sources, but also to designate microgrid operation modes and facilitate seamless mode transitions. With this mode-adaptive operation mechanism, a greater control freedom can be achieved than the conventional dc voltage droop control scheme. More importantly, this approach features fully self-disciplined regulation of distributed converters without an extra control center or communication link. Therefore, both reliability and flexibility can be enhanced. Meanwhile, a novel mode definition criterion is also provided to highlight the special characteristics of the dc microgrid which is different from an ac one. Three typical operation conditions are summarized according to which type of sources are dominating the power balance. Finally, the effectiveness of the proposed technique is verified experimentally based on a composite dc microgrid test system. | 2014 |
| 58. | Model Reference Adaptive Control-Based Speed Control of Brushless DC Motors With Low-Resolution Hall-Effect Sensors | Abstract—A control system with a novel speed estimation approach based on model reference adaptive control (MRAC) is presented for low cost brushless dc motor drives with low-resolution hall sensors. The back EMF is usually used to estimate speed. But the estimation result is not accurate enough at low speeds because of the divided voltage of stator resistors and too small back EMF. Moreover, the stator resistor is always varying with the motor’s temperature. A speed estimation algorithm based on MRAC was proposed to correct the speed error estimated by using back EMF. The proposed algorithm’s most innovative feature is its adaptability to the entire speed range including low speeds and high speeds and temperature and different motors do not affect the accuracy of the estimation result. The effectiveness of the algorithm was verified through simulations and experiments. | 2014 |
| 59. | MPPT and Voltage Balancing Control With Sensing Only Inductor Current for Photovoltaic-Fed, Three-Level, Boost-TypeConverters | Abstract—In the literature, both photovoltaic voltage and PV current need to be sensed to perform maximum power point tracking (MPPT) control. For three-level boost converter, both capacitor voltages need to be sensed and an additional voltage balancing control loop is required to balance the capacitor voltages. In this paper, the MPPT control and the voltage balancing control with sensing only inductor current is proposed. The provided simulation and experimental results demonstrate the proposed method. | 2014 |
| 60. | New Extendable Single-Stage Multi-input DC–DC/AC Boost Converter | Abstract—This paper presents a new extendable single-stage multi-input dc–dc/ac boost converter. The proposed structure comprises of two bidirectional ports in the converter’s central part to interface output load and battery storage, and several unidirectional input ports to get powers from different input dc source. In fact, he proposed topology consists of two sets of parallel dc– dc boost converters, which are actively controlled to produce two independent output voltage components. Choosing two pure dc or two dc-biased sinusoidal values as the converter reference voltages, situations of the converter operating in two dc–dc and dc–ac modes are provided, respectively. The proposed converter utilizes minimum number of power switches and is able to step up the low-level input dc voltages into a high-level output dc or ac voltage without needing any output filter. The converter control system includes several current regulator loops for input dc sources and two voltage regulator loops for generating the desired output voltage components, resulting in autonomously charging/discharging the battery to balance the power flow. Due to the converter inherent multi-input multi output control system, the small signal model of the converter is extracted and then the pole-placement control strategy via integral state feedback is applied for achieving the converter control laws. The validity and effectiveness of the proposed converter and its control performance are verified by simulation and experimental results. | 2014 |
| 61. | Novel Three-Port Converter With High-Voltage Gain | Abstract—In this paper, a novel three-port converter (TPC) with high-voltage gain for stand-alone renewable power system applications proposed. This converter uses only three switches to achieve the power flow control. Two input sources share only one inductor. Thus, the volume can be reduced. Besides, the conversion ratio of the converter is higher than other TPCs. Thus, the degree of freedom of duty cycle is large. The converter can have a higher voltage gain for both low-voltage ports with a lower turns ratio and a reasonable duty ratio. The voltage stress of switches is low; thus, conduction loss can be further improved by adopting low Rds(on) switches. Therefore, the converter can achieve a high conversion ratio and high efficiency at the same time. The operation principles, steady-state analysis, and control method of the converter are presented and discussed. A prototype of the proposed converter with a low input voltage 24 V for photovoltaic source, a battery port voltage 48 V, and an output voltage 400 V is implemented to verify the theoretical analysis. The power flow control of the converter is also built and tested with a digital signal processor. | 2014 |
| 62. | Optimal Trajectory Control of LLC Resonant Converters for LED PWM Dimming | Abstract—In this paper, a novel three-port converter (TPC) with high-voltage gain for stand-alone renewable power system applications is proposed. This converter uses only three switches to achieve the power flow control. Two input sources share only one inductor. Thus, the volume can be reduced. Besides, the conversion ratio of the converter is higher than other TPCs. Thus, the degree of freedom of duty cycle is large. The converter can have a higher voltage gain for both low-voltage ports with a lower turns ratio and a reasonable duty ratio. The voltage stress of switches is low; thus, conduction loss can be further improved by adopting low Rds(on) switches. Therefore, the converter can achieve a high conversion ratio and high efficiency at the same time. The operation principles, steady-state analysis, and control method of the converter are presented and discussed. A prototype of the proposed converter with a low input voltage 24 V for photovoltaic source, a battery port voltage 48 V, and an output voltage 400 V is implemented to verify the theoretical analysis. The power flow control of the converter is also built and tested with a digital signal processor. | 2014 |
| 63. | Parallel-Operation of Discrete SiC BJTs in a 6-kW/250-kHz DC/DC Boost Converter | Abstract—This paper describes issues related to parallel connection of SiC bipolar junction transistors (BJTs) in discrete packages. The devices are applied in a high-frequency dc/dc boost converter where the switching losses significantly exceed the conduction losses. The design and construction of the converter is discussed with special emphasis on successful parallel-operation of the discrete BJTs. All considerations are experimentally illustrated by a 6-kW, 250-kHz boost converter (300 V/600 V). A special solution for the base-drive unit, based on the dual-source driver concept, is also shown in this paper. The performance of this driver and the current sharing of the BJTs are both presented. The power losses and thermal performance of the parallel-connected transistors have been determined experimentally for different powers and switching frequencies. An efficiency of 8.23% (±0.02%)was measured using a calorimetric setup, while the maximum temperature difference among the four devices is 12 ◦C. | 2014 |
| 64. | Scalability of Quasi-Hysteretic FSM-Based Digitally Controlled Single-Inductor Dual-String Buck LED Driver to Multiple Strings | Abstract—There has been growing interest in single-inductor multiple-output (SIMO) dc–dc converters due to its reduced cost and smaller form factor in comparison with using multiple single output converters. An application for such a SIMO-based switching converter is to drive multiple LED strings in a multichannel LED display. This paper proposes a quasi-hysteretic finite-state machine-based digitally controlled single-inductor dual-output buck switching LED driver operating in discontinuous conduction mode (DCM) and extends it to drive multiple outputs. Based on he time -multiplexing control scheme in DCM, a theoretical upper limit of the total number of outputs in a SIMO buck switching LED driver for various backlight LED current values can be derived analytically. The advantages of the proposed SIMO LED driver include reducing the controller design complexity by eliminating loop compensation, driving more LED strings without limited by the maximum LED current rating, performing digital dimming with no additional switches required, and optimization of local bus voltage to compensate for variability of LED forward voltage VF in each individual LED string with smaller power loss. Loosely binned LEDs with arger VF variation can, therefore, be used for reduced LED costs. | 2014 |
| 65. | Self-Compensation of the Commutation Angle Based on DC-Link Current for High-Speed Brushless DC Motors With Low Inductance | Abstract—As low-resolution position sensors, a high placement accuracy of Hall-effect sensors is hard to achieve. Accordingly, a commutation angle error is generated. The commutation angle error will inevitably increase the loss of the low inductance motor and even cause serious consequence, which is the abnormal conduction of a freewheeling diode in the unexcited phase especially at high speed. In this paper, the influence of the commutation angle error on the power loss for the high-speed brushless dc motor with low inductance and non ideal back electromotive force in a magnetically suspended control moment gyro (MSCMG) is analyzed in detail. In order to achieve low steady-state loss of an MSCMG for space application, a raight forward method of self-compensation of commutation angle based on dc-link current is proposed. Both simulation and experimental results confirm the feasibility and effectiveness of the proposed method. | 2014 |
| 66. | Sensorless Control of BLDC Motor Drive for an Automotive Fuel Pump Using a Hysteresis Comparator | Abstract—This paper develops the brushless dc (BLDC) motor sensorless control system for an automotive fuel pump. The sensorless techniques that are based on a hysteresis comparator and a potential start-up method with a high starting torque are suggested. The hysteresis comparator is used to compensate for the phase delay of the back EMFs due to a low-pass filter (LPF) and also prevent multiple output transitions from noise or ripple in the terminal voltages. The rotor position is aligned at standstill for maximum starting torque without an additional sensor and any information of motor parameters. Also, the stator current can be easily adjusted by modulating the pulse width of the switching devices during alignment. Some experiments are implemented on a single chip DSP controller to demonstrate the feasibility of the suggested sensorless and start-up techniques. | 2014 |
| 67. | Single Power-Conversion AC–DC Converter With High Power Factor and High Efficiency | Abstract—This paper proposes a single power-conversion ac–dc converter with high power factor and high efficiency. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc–dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a novel control algorithm. The proposed converter provides single power-conversion by using the novel control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor 0.995 and maximum efficiency of 95.1% at the full load. The operation principle of the converter is analyzed and verified. Experimental results for a 400 W ac–dc converter at a constant switching frequency of 50 kHz are obtained to show the performance of the proposed converter. | 2014 |
| 68. | Single-Phase High Step-up Converter With Improved Multiplier Cell Suitable for Half-Bridge-Based PVInverter System | Abstract—In this paper, a single-phase high step-up converter is proposed, designed not only to boost the relatively low photovoltaic (PV) voltage to a high bus voltage with high efficiency, but also to offer a neutral point terminal for the half-bridge-based inverters. First and foremost, two symmetrical high step-up converters are combined and integrated to derive an improved converter with neutral point terminal, which is strongly expected for the half bridge-based inverters. Secondly, the voltage gain of the converter is extended and the narrow turn-off period is avoided by using the coupled inductor multiplier. Furthermore, the coupled inductor multiplier reduces the voltage stress of all the power devices. As a result, the low voltage-rated power devices can be employed to minimize the conduction losses. More importantly, all the active switches work in the zero-voltage-switching condition, which reduces the switching losses effectively. All these factors improve the circuit performance in the high step-up applications, especially for the half-bridge based PV inverter systems. Finally, the experimental results from a 500W, 48 –760 V prototype at 100 kHz switching frequency are provided to verify the effectiveness of the proposed converter. The highest efficiency of the prototype is 96.5% and the efficiency is over 94% in a wide load range. | 2014 |
| 69. | Soft-Switching Current-Fed Push–Pull Converter for 250-W AC Module Applications | Abstract—In this paper, a soft-switching single-inductor push–pull converter is proposed. A push–pull converter is suitable forlow-voltage photovoltaic ac module systems, because the step-up ratio of the high-frequency transformer is high, and the number of primary-side switches is relatively small. However, the conventional push–pull converter does not have high efficiency because of high-switching losses due to hard switching and transformer losses (copper and iron losses) as a result of the high turn ratio of the transformer. In the proposed converter, primary-side switches are turned ON at the zero-voltage switching condition and turned OFF at the zero-current switching condition through parallel resonance between the secondary leakage inductance of the transformer and a resonant capacitor. The proposed push–pull converter decreases the switching loss using soft switching of the primary switches. In addition, the turn ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results. | 2014 |
| 70. | Space Vector Pulsewidth Amplitude Modulation for a Buck–Boost Voltage/Current Source Inverter | Abstract—This paper proposes a space vector pulsewidth amplitude modulation (SVPWAM) method for a buck–boost voltage/current source inverter. For a voltage source inverter, the switching loss is reduced by 87%, compared to a conventional sinusoidal pulsewidth modulation (SPWM) method. For a current source inverter, the switching loss is reduced by 60%. In both cases, the power density is increased by a factor of 2 to 3. In addition, it is also verified that the output harmonic distortions of SVPWAM is lower than SPWM, by only using one-third switching frequency of the latter one. A 1-kW boost-converter-inverter prototype has been built and tested using this modulation method. The maximum overall system efficiency of 96.7% has been attained at full power rating. The whole system power density reaches 2.3 kW/L and 0.5 kW/lb. The numbers are remarkable at this power rating.As a result, it is feasible to use SVPWAM to make the buck–boost inverter suitable for applications that require high efficiency, high power density, high temperature, and low cost. Such applications include electric vehicle motor drive or engine starter/alternator. | 2014 |
| 71. | Supervisory Control of an Adaptive-Droop Regulated DC Microgrid With Battery Management Capability | Abstract—DC power systems are gaining an increasing interest in renewable energy applications because of the good matching with dc output type sources such as photovoltaic (PV) systems and secondary batteries. In this paper, several distributed generators (DGs) have been merged together with a pair of batteries and loads to form an autonomous dc microgrid (MG). To overcome the control challenge associated with coordination of multiple batteries within one stand-alone MG, a double-layer hierarchical control strategy was proposed. 1) The unit-level primary control layer was established by an adaptive voltage-droop method aimed to regulate the common bus voltage and to sustain the states of charge (SOCs) of batteries close to each other during moderate replenishment. The control of every unit was expanded with unit-specific algorithm,i.e., finish-of-charging for batteries and maximum powerpoint tracking (MPPT) for renewable energy sources, with which a smooth online overlap was designed and 2) the supervisory control layer was designed to use the low-bandwidth communication interface between the central controller and sources in order to collect data needed for adaptive calculation of virtual resistances (VRs) as well as transit criteria for changing unit-level operating modes. A small-signal stability for the whole range of VRs. The performance of developed control was assessed through experimental results. | 2014 |
| 72. | Switching Frequency Derivation for the Cascaded Multilevel Inverter Operating in Current Control Mode Using Multiband Hysteresis Modulation | Abstract—In this paper, a generalized expression of the switching frequency is obtained for the cascaded H-bridge multilevel inverter tracking a reference current. The inverter is considered connected to the grid and operates in current control mode using the generalized algorithm of multiband hysteresis modulation. The results are derived based on the time-domain current error dynamics which is applicable for any levels of the cascaded multilevel inverter. The generalized expression explicitly shows the relationship between the instantaneous switching frequency with the net hysteresis band, system parameters, and number of levels. The expression can be used for the determination of the net hysteresis band required for a given desired effective maximum switching frequency for the multiband hysteresis modulation. The value of maximum, minimum, and average switching frequencies can be obtained from the instantaneous switching frequency expression. The results are useful for the design of the multiband hysteresis controller for tracking of the desired reference current and can be used to evaluate the performance characteristics of the multilevel inverter. The simulation and experimental verification of the results are obtained through single-phase, three- and five-level cascaded H-bridge inverters. | 2014 |
| 73. | Switching Strategy Based on Model Predictive Control of VSI to Obtain High Efficiency and Balanced Loss Distribution | Abstract—This paper proposes the switching strategy based on finite control set model predictive control (FCS-MPC) method, to reduce switching losses and obtain balanced loss distribution of the voltage-source inverters (VSIs). Unlike the conventional FCSMPC method with no explicit information of the reference voltage, the developed voltage-based FCS-MPC scheme produces the future reference voltage vector with the Lyapunov function every sampling period. With information of both the future reference voltage and the future load current vectors, the proposed switching strategy instantaneously determines one optimum clamped phase among the three legs in the VSI every sampling period. By optimally determining the clamping phase and its duration on the basis of every sampling period, the proposed switching strategy can successfully reduce the VSI switching losses. In addition, the proposed switching method can yield a balanced loss distribution among the switches in the VSI, contrary to the conventional FCSMPC. The balanced loss generation as well as the switching loss reduction by the proposed method, which is optimal at the sampling period scale, is directly incorporated with the platform of the FCS-MPC algorithm, since the FCS-MPC operates on the basis of the sampling period. Thus, the proposed switching operation based on the voltage-based FCS-MPC algorithm enables the future VSI output currents to track the future reference current vector, as well as results in the reduced switching losses and the balanced loss performance. | 2014 |
| 74. | Synthesis of Canonical Elements for Power Processing in DC Distribution Systems Using Cascaded Converters and Sliding-Mode Control | Abstract—Switched power converters are used to interface the dc output in modern distributed power generation systems, which are usually aggregated to the main grid to yield the necessary power using interconnected modules. Synthesis, modeling, and stability analysis of interconnected systems using cascaded converters working under sliding-mode control are considered in this paper. A systematic procedure to synthesize cascaded connection of dc–dc boost converters is introduced. The approach is based on making each module to behave as a suitable canonical element for power processing. Three different elements are considered, which are the dc power gyrator, the dc transformer, and the dc loss-free resistor. These canonical elements are designed by means of a sliding-mode control theory and then their dynamic behavior is studied in detail.The sliding-mode conditions for each case are derived in closed form to obtain design-oriented criteria for selecting the parameters of the system. The aforementioned canonical elements are compared to select the most suitable one for a distributed power system. Simulation results ensure the correctness of the proposed approach. Experimental measurements corroborate the theoretical predictions and the numerical simulations. | 2014 |
| 75. | The Transformerless Single-Phase Universal Active Power Filter for Harmonic and Reactive Power Compensation | Abstract—This paper presents a universal active filter for harmonic and reactive power compensation for single-phase systems applications. The proposed system is a combination of parallel and series active filters without transformer. It is suitable for applications where size and weight are critical factors. The model of the system is derived and it is shown that the circulating current observedin the proposed active filter is an important quantity that must be controlled. A complete control system, including pulsewidth modulation (PWM) techniques, is developed. Comparisons between the structures are made from weighted total harmonic distortion (WTHD). The steady-state analysis is also presented in order to demonstrate the possibility to obtain an optimum voltage angle reducing the current amplitude of both series and parallel converters and, consequently, the total losses of the system. Simulated and experimental results validate the theoretical considerations. | 2014 |
| 76. | Two- and Three-Dimensional Omnidirectional Wireless Power Transfer | Abstract—Non identical current control methods for 2- and 3-D omnidirectional wireless power systems are described. The omnidirectional power transmitter enables acmagnetic flux to flowing all directions and coil receivers to pick up energy in any position in the proximity of the transmitter. It can be applied to wireless charging systems for low-power devices such as radio-frequency identification devices and sensors. Practical results on 2-D and 3-D systems have confirmed the omnidirectional power transfer capability. | 2014 |
| 77. | Universal Digital Controller for Boost CCM Power Factor Correction Stages Based on Current Rebuilding Concept | Abstract—Continuous conduction mode power factor correction (PFC) without input current measurement is a step forward with respect to previously proposed PFC digital controllers. Inductor volt-second (vsL) measurement in each switching period enables digital estimation of the input current; however, an accurate compensation of the small errors in the measured vsL is required for the estimation to match the actual current. Otherwise, they are accumulated every switching period over the half-line cycle, leading to an appreciable current distortion. A vsL estimation method isproposed, measuring the input (vg ) and output voltage (vo). Discontinuous conduction mode (DCM) occurs near input line zero crossings and is detected by measuring the drain-to-source MOSFET voltage vds. Parasitic elements cause a small difference between the estimated voltage across the inductor based on input and output voltage measurements and the actual one, which must be taken into account to estimate the input current in the proposed sensorless PFC digital controller. This paper analyzes the current estimation error caused by errors in the ON-time estimation, voltage measurements, and the parasitic elements. A new digital feedback control with high resolution is also proposed. It cancels the difference between DCM operation time of the real input current, (T g DCM) and the estimated DCM time (T reb DCM). Therefore, the current estimation is calibrated using digital signals during operation in DCM. A fast feed forward coarse time error compensation is carried out with the measured delay of the drive signal, and a fine compensation is achieved with a feedback loop that matches the estimated and real DCM time. The digital controller can be used in universal applications due to the ability of the DCM time feedback loop to autotune based on the operation conditions (power level, input voltage, output voltage. . .), which improves the operation range in comparison with previous solutions. Experimental results are shown for a 1-kW boost PFC converter over a wide power and voltage range. | 2014 |
| 78. | Virtual Impedance-Based Selective Harmonic Compensation (VI-SHC) PWM for Current Source Rectifiers | Abstract—To mitigate the line current harmonics of a highpower current source rectifier (CSR) system, the selective harmonic elimination (SHE) scheme is frequently used due to its low switching frequency and superior harmonic performance. However, the SHE scheme only focuses on the harmonics generated by the converter itself. It cannot cope with the line current harmonics caused by the background grid voltage harmonics. In this paper, a selective harmonic compensation scheme using the virtual impedance concept (VI-SHC) is presented. This method compensates for the preexisting grid background harmonics using only the line current measurement, and provides superior line current harmonic performance. The proposed method does not require measuring the grid voltage harmonics (which are typically low), does not rely on an accurate CSR system model, and therefore is very robust for practical implementation. This PWM control scheme has been verified by real-time experiments on a CSR prototype. | 2014 |