基于载波重构的级联逆变器功率均衡调制策略

摘要

In view of the shortcomings of the existing modulation strategy applied to cascaded H-bridge (CHB) inverter, a novel power balance modulation strategy was proposed in this paper. This strategy combines the advantages of the carrier phase shift (CPS) modulation strategy and carrier disposition (PD) modulation strategy. By reconstructing the triangular carriers in improved CPS modulation strategy, a new carriers arrangement still retaining the characteristics of carrier phase shift was obtained. Compared with PD modulation strategy, the proposed modulation strategy has the same output voltage harmonic characteristics. Therefore, under the novel power balance modulation strategy proposed in this paper, the output power of the cascaded cells can be self-balanced, and the harmonic characteristics of the inverter output line voltage can be improved effectively. Taken three-cell cascaded multilevel inverter as an example, the method of carriers reconstruction and the principle of proposed power balance modulation strategy were provided. The time required for power balance was also analyzed. Simulation and experimental results verified the validity of the proposed strategy.%针对已有调制策略应用于级联H桥型(CHB)逆变器中时存在的不足,结合载波移相(CPS)和载波同相层叠(PD)调制策略的优点,提出一种基于载波重构的新型功率均衡调制策略.所提调制策略通过对改进的CPS调制策略中三角载波进行重构,得到一种仍然保留载波移相特征的新型载波排列方式,且采用新型载波排列方式进行调制,逆变器输出电压谐波特性与PD调制策略下的完全一致.因此,在所提的新型功率均衡调制策略下,可以实现级联单元输出功率自均衡,同时可以有效改善逆变器输出线电压谐波特性.本文以三单元级联H桥型逆变器为例研究载波重构方法,分析新型功率均衡调制策略原理及功率均衡所需时间,并通过仿真和实验验证了理论分析的正确性和调制策略的可行性.