Multilevel conversion techniques, power factor correction (PFC) techniques and soft switching techniques are the three research hot points of power electronics. The paper proposes a single phase three-level PFC circuit with passive lossless snubbers which embodies these trends. Firstly, the three-level buck and boost topologies are derived from one bridge leg of the traditional diode clamped three-level inverters. Then, a single phase three-level PFC circuit is presented based on the three-level boost topology, and the principle and implementation approaches of the three-level PFC circuit are described. To realize the soft switching of the main switches and freewheeling diodes, two passive lossless snubber cells are added to the circuit. The operating principle and design considerations of the new circuit are discussed in detail. Finally, a 2 KW prototype of the single phase three-level PFC with the passive lossless snubber is built and tested. The simulated and experimental results indicate that the proposed circuit can realize the function of three-level PFC, increase system efficiency and have no over-voltage stresses on main power switches. Moreover, the power factor of the proposed circuit with the passive lossless snubber is higher than that of the circuit without the snubber.

PSpice models for power semiconductor switching devices, which include the gate turn-off thyristor, the insulated gate bipolar transistor and the mos-controlled thyristor, are presented. These models are suitable for time domain circuit simulation packages which incorporate bipolar transistor and metal oxide semiconductor field effect transistor models. The models presented are composite models, being built-up from these two basic switching components. Simulation, experimentation results and parametric sensitivity analysis validate the in-circlrit performance of the proposed composite models. The presented model:; are meant for applications where circuit level :simulated performance is of primary importance, rather than accurate prediction of device microscopic electrical haracteristics.

A corona surface treatment based on a pulse density modulation (PDM) and pulse frequency modulation (PFM) hybrid control scheme is presented. The PDM scheme is used to regulate the output power of the inverter and the PFM scheme is used to compensate for temperature and other environmental influences on the discharge. Experimental results show that the PDM and PFM hybrid control series-resonant nverter (SRI) makes the corona discharge treatment simple and compact, thus leading to higher efficiency. The hybrid control SRI is able to realise constant frequency control and linear power adjustment and is thus becoming an ideal choice for corona discharge treatment.

本文就电力电子技术中功率器件变换枝术领域的最新发展进行综述，特别对DC DC变流器蕊功率因敷校正技术的当前最新发展动向作了详细的介绍和分析。

讨论了在PSPICE中建立电力电子器件模型的特点，提出用多瞬态分析功能获碍新型电力半导体器件模型特性的方法 以绝缘栅晶体管(IGBT)为例，将仿真结果与实际器件进行了比较。

A novel passive lossless turn-on snubber with a softclamped turn-off snubber circuit for voltage source inverters is proposed. The energy trapped in the snubber is recovered into the dc supply and load without any active devices, associated control circuitry, or resistors. The overshoot voltage on the switches is clamped, and the peak switch current is low, making this snubber suitable for use in high-power insulated gate bipolar transistor (IGBT) inverters.

he paper presents a composite gate turn-off thyristor model, which is based on the combination of the p-n-p and n-p-n transistor models. PSpice simulations and parametric sensitive analysis are performed with the composite model and calculated results are given, which show that it corresponds statically and dynamically with the practical device, and in particular, at turn-off. Furthermore, the model, together with Controlled Thyristor. The simulated results for this model are also presented.

e paper proposes a new passive circuit for partial snubber-energy recovery in GTO thyristor high-power voltage-source inverters. The analysis and simulations sh,ow that the proposed bridge-leg snubber circuit can recover greater than sixty five per cenl of the total snubber energy, as well as the freewheel diode reverse recovery energy. This energy is recovered back to the DC supply through a closely coupled transformer, without any active devices or associated control circuitry. This snubber circuit, being simple, is particularly suitable for use in GTO thyristor high-power inverters. Design equations, simulations and experimental results are given.

This paper presents a new composite soft-switching configuration for single-phase inverters where power bridge leg modules are used. The presented configuration consists of only one inductor and one capacitor as well as two low-power-rated switches/diodes for full-bridge circuits. It can realize snubber functions and/or resonant zero-current switching at any load current for switches in power inverters with unipolar sinusoid pulsewidth modulation control. The idea presented here is that soft-switching processes at turn-on and -off for each active switch in inverters can be different. The detailed circuit operational processes, simulation waveforms, and experimental results are included.

车文对高功率多电平变换器的主电路拓扑结构，控制策略．研究应用现状厦发展前景进行了较为详细的讨论，并据此对多电平变换器今后的研究方向提出了建议。