带飞跨电容的三电平全桥直流变换器输入中点电压的自平衡分析  

Self-Balance Mechanism Analysis of the Neutral Point Voltage in Three-Level Full Bridge DC-DC Converter with Flying Capacitors

作　　者：刘朋 陈昌松 段善旭 Liu Peng;Chen Changsong;Duan Shanxu(State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 China)

机构地区：[1]华中科技大学电气与电子工程学院强电磁工程与新技术国家重点实验室,武汉430074

出　　处：《电工技术学报》2018年第18期4335-4344,共10页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金(51477067);光宝电力电子技术科研基金(PRC20161047)资助项目

摘　　要：输入中点电压平衡问题通常是三电平拓扑的研究重点,但是在现有的文献中针对三电平全桥(TLFB)直流变换器的输入中点电压平衡问题还没有深入分析。针对TLFB直流变换器,给出其详细的模态分析,进而揭示其中点电压偏移的原因,并说明飞跨电容能带来中点电压自平衡的功能。首先通过对比无飞跨电容的三电平半桥(TLHB)和TLFB变换器的供电模态,指出在对管关断不一致的情况下,TLFB电路也会出现单个分压电容提供负载电流的模态,从而导致输入中点电压偏移;之后针对带飞跨电容的TLFB电路进行模态分析,证明即使在对管关断不一致的情况下,飞跨电容的引入能极大缓解中点电压的偏移,从而实现自平衡;最后分析稳态情况下偏移电压的影响因素,推导带飞跨电容的TLFB电路中点电压稳态误差的数学表达式,该表达式能够对TLFB变换器中飞跨电容的设计提供理论指导。通过仿真和实验验证了所提方法的有效性。The balance of the neutral point voltage is always an important issue for the three-level topologies,but the deep analysis about the neutral point voltage balance in the three-level full bridge(TLFB)DC-DC converter has not been provided in publications.Focusing on the TLFB converter,this paper provides the detailed mode operation analysis of the converter and reveals the cause of the unbalanced neutral point voltage.Moreover,the mechanism of the self-balance ability brought by the flying capacitors is explained in detail.First,the supply modes of three-level half bridge(TLHB)and TLFB converters without flying capacitors are compared.It is pointed out that in the case of inconsistent turn-off of the diagonal switches,an individual input capacitor will have to provide the load current,resulting in an offset of the neutral point voltage.Then the detailed mode operation of TLFB with flying capacitor has been provided when the diagonal switches turn off inconsistently,which proves that flying capacitors can relieve the drift of the neutral point voltage and further achieve the self-balance of the neutral point voltage.At last,the influence factor of the voltage drift in steady state has been analyzed.The specific expression has also been derived,which is another important design guidance for the TLFB converter.The feasibility of the proposed method is verified by the simulation and experimental results.

关 键 词：三电平全桥 直流变换器 中点电压平衡 飞跨电容 

分 类 号：TM46[电气工程—电器]