Single-stage ZVS PWM full-bridge converter

A new soft-switched ac-dc single-stage pulse width modulation (PWM) full-bridge converter is proposed. The converter operates with zero-voltage switching (ZVS), fixed switching frequency, and with a continuous input current that is sinusoidal and in phase with the input voltage. This is in contrast with other ac-dc single-stage PWM full-bridge converters that are either resonant converters operating with variable switching frequency control and high conduction losses, converters whose switches cannot operate with ZVS, or converters that cannot perform power factor correction (PFC) unless the input current is discontinuous. All converter switches operate with soft-switching due to a simple auxiliary circuit that is used for only a small fraction of the switching cycle. The operation of the converter is explained and analyzed, guidelines for the design of the converter are given, and its feasibility is shown with results obtained from an experimental prototype.     

New ZVT-PWM DC/DC converters using active snubber

A novel active snubber soft switching method is proposed. The unique location of the resonant inductor and capacitor ensures low current and voltage stresses in the converter. An analytical study of a boost dc-dc converter with the proposed active snubber method is presented in detail to illustrate its operation principles and design considerations. By simple modification, this soft switching method is also suitable for ac-dc boost topology, especially for high power-factor-correction (PFC) universal interface applications. A 500 W prototype system has been made to simulatively and experimentally verify the performance of the soft switching.     

Soft-switching single-stage AC-to-DC converter with low harmonic distortion

A 1 /spl phi/ high-frequency (HF) transformer isolated, soft-switching single-stage ac-dc converter with low line-current harmonic distortion is presented. Its operation is explained with equivalent circuits for the various intervals. The converter is analyzed and design curves are obtained. An optimization parameter is introduced and a systematic design procedure is illustrated with a design example. Detailed SPICE simulation and experimental results of a 500 W converter with load as well as line voltage variation are given to verify theory. The proposed converter employs a zero-voltage transition (ZVT) network to ensure zero-voltage switching (ZVS) at all loads, and natural power factor correction is ensured using a simple control circuit.     

Single-phase grid-connected PV system using three-arm rectifier-inverter

A grid-connected photovoltaic (PV) power supply system with on-line voltage regulation capability is presented. It employs the three-arm rectifier-inverter topology with PV modules connected directly on the dc-link. The common-arm is with line-frequency switching and synchronous to the input voltage, aiming for a lower switching loss and decoupling the control of rectifier and inverter portions. As a result, the rectifier and inverter portions can be controlled independently with the rectifier-arm and inverter-arm, respectively. For maximum power point tracking (MPFF) of the PV modules and balancing the power among utility, PV, and the load, a variable dc-link voltage is adopted and controlled by the rectifier-arm based on the MPPT control algorithm. The inverter-arm then regulates the load voltage with good regulation and low distortion. Due to large variation of the dc-link voltage, a feedforward plus feedback control technique with variable gain is developed to keep constant bandwidth of the current loop at any operation condition. Therefore, the performance of the rectifier and inverter portions can be ensured. A system containing a 2 kVA converter and a 1.2 kW PV module is set up, and some experimental results are provided for demonstrating the effectiveness of the proposed method.     

Fault-tolerance wide voltage conversion gain DC/DC converter for more electric aircraft

In this paper, a fault-tolerance wide voltage conversion gain DC/DC converter for More Electric Aircraft (MEA) is proposed. The proposed converter consists of a basic Cuk converter module and n expandable units. By adjusting the operation state of the expandable units, the voltage conversion gain of the proposed converter could be regulated, which makes it available for wide voltage conversion applications. Especially, since mutual redundancy can be realized between the basic Cuk converter module and the expandable units, the converter can continuously work when an unpredictable fault occurs to the fault-tolerant parts of the proposed converter, which reflects the fault tolerance of the converter and significantly improves the reliability of the system. Moreover, the advantages of small input current ripple, automatic current sharing and low voltage stress are also integrated in this converter. The working principle and features of the proposed converter are mainly introduced, and an experimental prototype with 800 W output power has been manufactured to verify the practicability and availability of the proposed converter.     

Series of radiation-hardened, high efficiency converters for high voltage bus

A review of common switching techniques for dc/dc power conversion is presented. The evolution of the forward converter is discussed, leading naturally to the introduction of the double forward converter. Technical details for a series of radiation-hardened converters are then provided. This series was designed for space power management and distribution (PMAD) applications. The successful development of the PMAD converter demonstrated the viability of high voltage bus.     

Tapped-inductor filter assisted soft-switching PWM DC-DC power converter

A novel high-frequency transformer linked full-bridge type soft-switching phase-shift pulsewidth modulated (PWM) controlled dc-dc power converter is presented, which can be used as a power conditioner for small-scale photovoltaic and fuel cell power generation systems as well as isolated boost dc-dc power converter for automotive ac power supply. In these applications with low-voltage large-current sources, the full-bridge circuit is the most attractive topology due to the possibility of using low-voltage high-performance metal-oxide-semiconductor field-effect transistor (MOSFET) and achieving high efficiency of the dc-dc power converter. A tapped-inductor filter including the freewheeling diode is newly implemented in the output stage of the full-bridge phase-shift PWM dc-dc converter to achieve soft-switching operation for the wide load variation range. Moreover, in the proposed converter circuit, the circulating current is effectively minimized without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching dc-dc power converter was verified in laboratory level experiment with 1 kW 100 kHz breadboard setup using power MOSFETs. Actual efficiency of 94-97% was obtained for the wide duty cycle and load variation ranges.     

Half-bridge neutral point diode clamped rectifier for power factor correction

A high power factor rectifier based on neutral point clamped scheme is proposed. The voltage stress of each power semiconductor of the adopted rectifier is equal to the half dc bus voltage instead of full dc link voltage in the conventional switching mode rectifier. The control signals of the power switches are derived from the dc link voltage balance compensator, line current controller, and dc link voltage regulator. The hysteresis current control scheme is employed to draw a clean sinusoidal line current, high input power factor, regulated dc link voltage, and balance capacitor voltages. Three voltage levels are generated on the ac terminal of the adopted rectifier. To verify the proposed operation scheme, performance characteristics are given by the experimental results.     

Boost变换器软开关技术的研究

提出一种新型有源软开关技术,在辅助开关和谐振电路的作用下,可以实现开关电源中开关管的零电压开通和零电压关断,而且可以减小开关管的电压应力和电流应力。对电路工作原理和参数设置进行了分析,给出了关键参数的选取原则。利用实际电路,验证了有源软开关技术的有效性。     

三相电压型脉宽调制整流器定频模型预测控制

针对三相电压型脉宽调制(PWM)整流器有限控制集模型预测控制采样频率高、开关频率不固定的缺点,提出了一种定频模型预测控制方法。通过求解价值函数得到PWM整流器交流侧下一采样时刻所要输出的电压值,利用空间矢量脉宽调制技术输出计算得到的电压值,实现定频模型预测控制。仿真与试验结果表明:所提出的控制算法开关频率恒定,稳态电流谐波含量低,实现了整流器高功率因数运行。     

ZCS-PWM boost rectifier with high power factor and low conduction losses

A new single-phase high power factor rectifier is proposed, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current-switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the switches and zero-voltage-switching (ZVS) in the diodes. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path and the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Seven transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM switch model is used to predict the system performance. A prototype rated at 1 kW, operating 60 kHz, with an input ac voltage of 220 V/sub rms/ and an output voltage 400 V/sub dc/ has been implemented in laboratory. An efficiency of 97.2% and power factor near 0.99 has been measured. The analysis and design of the control circuitry are also presented.     

单端正激ZVT功率变换器实现

介绍一种单端正激工作方式的零电压过渡（ＺＶＴ）软开关ＤＣ－ＤＣ变换器;描述该变换器的原理和特征;给出了应用ＺＶＴ软开关技术和集成控制块ＳＧ３５２５Ａ的２４Ｖ／９ＡＤＣ－ＤＣ变换器电路和实验结果。     

Implementation of nondeterministic pulsewidth modulation forinverter drives

A single-phase power factor preregulator to improve the power quality in the input side of an ac/dc/ac converter and a random pulsewidth modulation (PWM) to reduce the emitted noise energy and the mechanical vibration for an induction motor drive is proposed. The hysteresis current control (HCC) technique for a voltage source switching mode rectifier (SMR) is adopted. A control scheme is presented such that the line current is driven to follow the reference current which is derived from the dc bus voltage regulator and the output power estimator. A random pulse position technique for a three-phase voltage source inverter system to reduce the noise energy and resonant vibration from ac machine drive is described. By randomly varying the instantaneous pulse position in each switching frequency, the frequency distribution of harmonics is spread in a wide frequency range which results in reduction of torque pulsations in the ac motor drive systems. To investigate the proposed control scheme, experimental tests based on a laboratory prototype were implemented to show the nearly unity power factor at the SMR and reduce the noise energy concentrated at the specific tones     

Voltage-based maximum power point tracking control of PV system

Photovoltaic (PV) generators exhibit nonlinear v-i characteristics and maximum power (MP) points that vary with solar insulation. An intermediate converter can therefore increase efficiency by matching the PV system to the load and by operating the solar cell arrays (SCAs) at their maximum power point. An MP point tracking algorithm is developed using only SCA voltage information thus leading to current sensorless tracking control. The inadequacy of a boost converter for array voltage based MP point control is experimentally verified and an improved converter system is proposed. The proposed converter system results in low ripple content, which improves the array performance and hence a lower value of capacitance is sufficient on the solar array side. Simplified mathematical expressions for a PV source are derived. A signal flow graph is employed for modeling the converter system. Current sensorless peak power tracking effectiveness is demonstrated through simulation results. Experimental results are presented to validate the proposed method     

Current-fed multiresonant isolated DC-DC converter

A novel topology, current-fed multiresonant dc-dc converter (CF-MRC) was studied theoretically and experimentally. The new topology differs from previously described current-fed push-pull parallel-resonant topologies in the fact that the output is coupled to the current of the resonant inductor and in the addition of a second capacitor across the transformer. The main features of the proposed converter are an inherent protection against a short and open circuit at the output, a high voltage gain and zero voltage switching (ZVS) over a large range of output voltage. These characteristics make it a viable choice for applications, such as a high voltage capacitor charger, that require controllable current sourcing over a wide output voltage swing.     

A fixed frequency LCL-Type series resonant converter

A fixed frequency LCL-type series resonant converter (SRC) which uses an inductive output filter is proposed. Steady-state analysis of the converter is presented using complex ac circuit analysis. Based on the analysis, a simple design procedure is given. Detailed space integrated control experiment (SPICE) simulation results are presented to evaluate the performance of the designed converter under varying load and supply voltage conditions. Also, detailed experimental results obtained from a metal-oxide-semiconductor field-effect transistor (MOSFET) based 500 W converter are presented to verify the analysis and SPICE simulation results. The results obtained from the analysis, SPICE simulation and the experimental converter are compared. The proposed converter requires a narrow variation in pulsewidth while maintaining lagging power factor mode of operation for a very wide variation in the load as well as supply voltage     

A resonant DC-DC transformer

The characteristics of a push-pull parallel resonant converter (PPRC) when operated as a DC-DC transformer were investigated theoretically and experimentally. In the DC-DC transformer region, the voltage transfer ratio of the PPRC was found to be practically constant and independent of the input voltage and load. In this mode, all the switching elements operate in the zero voltage switching (ZVS) condition. Another important feature of the proposed DC-DC transformer is the ability to drive it by an arbitrary switching frequency, provided that the latter is lower than the self-oscillating frequency. This permits the synchronization of the converter to a master clock. The analytical expressions for voltage and current stresses, as well as the other key parameters derived, are applied to develop design guidelines for the DC-DC transformer. The proposed topology was tested experimentally on a 100-W unit which was run in the 200-kHz frequency region     

并联H桥DC/DC变换器软开关技术研究

与传统的Buck电路相比,基于H桥并联的DC/DC变换器可以实现电压的双极性输出和故障时的冗余控制,非常适合用于大功率电动机正反转控制的场合。分析了并联H桥型DC/DC变换器的结构组成和双脉宽调制(PWM)模式。为了降低双脉宽调制下H桥型DC/DC变换器的开通和关断损耗,对无源软开关技术进行了分析,重点探讨了RCD缓冲电路和最小应力缓冲电路之间的性能差异,指出最小应力软开关技术可以获得更好的软开关性能,并就将其用于双脉宽调制下的并联H桥DC/DC变换器进行了仿真研究。仿真结果表明:最小应力软开关技术用于双脉宽调制下并联H桥DC/DC变换器时,可以实现开关管的零电压开通和零电流关断。     

不平衡电网三相四开关变换器预测功率控制

为了提高三相四开关变换器并网电能质量,提出一种适用于不平衡电网条件的有限控制集模型预测直接功率控制策略。分析三相四开关变换器的工作机制和电压矢量变化关系,并建立其功率预测模型。使用αβ静止坐标系下的电网电压以及其90°延迟信号计算功率补偿值,设计价值函数,选择最优电压矢量对应的开关状态。该控制策略无需传统的正负序分离控制及锁相环技术,易于实现。仿真和试验结果表明,在不平衡电网条件下,所提出的控制策略能够有效降低并网电流畸变,消除功率波动,提高并网电能质量。