级联式逆变器故障单元旁路下输出平衡的椭圆校正法

摘要

采用中点移位方法实现级联式逆变器故障旁路状态下的输出平衡已被广泛认可.然而,现有方法必须离线计算出全部故障旁路状态下的偏移角度,以便由控制器通过查表方式构建新的参考信号,实现中点移位.这样,不仅计算量繁重,而且灵活性较差.基于空间电压矢量特征,提出了以椭圆轨迹校正与非等量谐波注入方式相结合的在线控制方法.该方法物理概念清晰、算法简单、实时性强,只需已知故障单元数便可直接构造数学模型,实现三相线电压输出平衡且输出电压利用率可以达到理论最大值,仿真和实验结果证明该方法切实可行.%The neutral-point shift method used to realize the output balance of the cascaded inverter under failed-unit bypass has been widely recognized. However,the existing methods mostly deal with a lot of off-line angle calculation in all of the bypass states to meet the need of re-structure of the new reference signals by the controller. They involve in only heavy computations but less flexibility. Based on the characteristics of space voltage vector,a elliptical trajectory correction method with the non-equivalent harmonic injection was proposed. In this method,the mathematical model can be established by the failed-unit numbers,and the theoretical maximum of output voltage can be reached with balance three-phase line voltage outputs. It has clearer physical concept, simpler algorithm, and better real time. Simulation and experimental results show the approach is feasible.