阶梯波合成级联型多电平逆变器功率均衡策略

首先指出在波形质量要求相同的条件下，III型级联多电平逆变器所需级联单元个数最少。接着讨论了3种级联多电平逆变器功率均衡问题，指出I型级联单元数低于7时，宜采用循环脉冲实现功率均衡，高于7时，宜采用调整开关角的方式实现功率均衡；II型级联多电平逆变器只能通过调整开关角实现功率均衡，由于开关组合方式冗余，II型存在多组功率均衡方程组，而通过计算发现，2单元III型级联多电平逆变器无法实现功率均衡。最后通过一台单相容量为2 kVA的原理样机对3单元II型级联多电平逆变器的均衡策略进行了实验验证。

Power Balance Strategy for Staircase Waveform Synthesis of the Cascaded Multilevel Inverter

Firstly, it points out that the III-type cascaded multilevel (ML) inverter is the best topology, when outputs the same quality voltage. Secondly, the swapping pulse power balance strategy is proved to be better for the I-type cascaded ML inverter if the number of cascaded cells is lower than seven, or adjusting firing angles is better. After detailed analysis, it points out that the II-type can realize power balance by adjusting firing angles in one output cycle, whereas the III-type cascaded multilevel inverter can not ensure power balance. Since the switching mode is redundant for the II-type, it has several kinds of power balance equations. Finally, a one phase 2 kVA prototype is designed to verify the validity of the power balance strategy for II-type.