基于双变压器的复合式谐振三电平零电流开关变换器

Dual Transformer Based Hybrid Resonant Three-level Converter with Zero-current Switching

针对分布式光伏发电接入中压直流配电网的应用场合,提出了一种基于双变压器的复合式谐振三电平变换器。新型变换器是在传统中性点钳位型三电平电路的基础上,通过添加一个辅助电路实现了基础三电平电路的固定占空比运行,变换器工作于电流断续模式。其中,基础三电平电路传输大部分功率,而辅助电路采用脉宽调制方式,可以实现基础三电平电路在全负载范围内的零电流开关,从而显著降低变换器的开关损耗。重点讨论了辅助变压器变比和谐振电容对开关管电流、谐振电压峰值、谐振电感值大小的影响,提出了相应的参数设计指导原则。最后,制作了一套300~1500V/2kW原理样机对所提变换器的性能进行了验证。

A hybrid resonant three-level converter based on dual transformers is proposed,which is suitable for the access of distributed photovoltaic power to the medium voltage DC distribution network.The proposed converter can be obtained by adding an auxiliary circuit into the traditional neutral point clamped three-level circuit,achieving the basic three-level circuit operation with fixed duty cycle.The converter operates in a disc on tinuous current mode.The basic three-level circuit transits most of the power,and zero-current switching for the basic three-level circuit is realized in the full load range by pulse width modulation of the auxiliary circuit.As a result,the switching loss of the converter can be significantly reduced.This paper also discusses the effects of the ratio of auxiliary transformer and the resonant capacitance on the switch current,the peak value of resonant voltage and the value of resonant inductance.Then the parameter design principles are put forward.Finally,a prototype of 300?1 500 V/2 kW is built to verify the performance of the proposed converter.