基于电容电压平衡的五电平堆叠多单元变流器空间矢量调制策略*

文中提出一种基于电容电压平衡的五电平堆叠多单元(SM,Stacked Multicell)变流器的空间矢量控制策略,使空间矢量调制(SVM)算法能应用于堆叠多单元变流器(SMC,Stacked Multicell Converters)这种新型拓扑结构的变流器中。通过对五电平SM变流器拓扑的研究,得出单相电路所有可能的开关状态及其对应的电流通路,并由此分析各个开关状态对电容电压的影响。在不改变空间矢量调制算法计算得出的冗余矢量和占空比的前提下,控制策略仅仅通过开关状态的选择达到同时调整悬浮电容和母线电容电压的效果。因此该控制策略能将任何空间矢量调制算法应用于SM变流器,抑制变流器的悬浮电容与母线电容的中点电位偏移。在Matlab/Simulink中构建SM变流器并进行仿真,仿真的结果证明了该控制策略的有效性。

A five-level-space-vector modulation strategy for stacked multicell converters based on balancing of capacitors' voltage

A space-vector-control strategy for SMC, based on balancing the voltage of capacitors, is proposed in this paper.The strategy applies space-vector-modulation(SVM) algorithm to SMC(stacked multicell converters), which is a novel topology structure of convertors.Through research on the topology of five-level SMC, every available switching state of a single phase is found and the effect of each switching state on capacitors' voltage is analyzed.The strategy adjusts the voltage of flying capacitors and dc-link capacitors only by selecting switching states, without changing the redundant space-vectors and their duty cycles, which are calculated by the SVM algorithm.Therefore, this control strategy is able to apply any SVM algorithm to five-level SMC, inhibiting the flying capacitors and neutral-points shifts of dc-link capacitors.A model of SMC is built in Matlab/Simulink for simulation.The result of the simulation confirms the validity of the proposed strategy.