混合逆变器改进调制算法的研究

Investigation of Advanced Control Strategies for Hybrid Multilevel Inverter

目前,在混合级联型逆变器的研究领域中,改变串联单元的母线电压比是一种比较典型的方法。但是,该类拓扑结构存在着不同电压比例母线之间的"能量回流"问题,在不同的调制比下运行,可能会出现导致母线电压不平衡的情况。针对该问题,本文在分析"能量回流"问题产生机理的基础上,提出了一种纯软件算法的解决方案,该方案针对不同的调制比,实时的改变主逆变器的导通比较电压,且同时动态的调整从逆变器的零序分量,从而实现了全调制比范围内克服"能量回流"的问题,并且改善了输出电压谐波性能等目标。最后,本文对所提出的控制算法进行了仿真和实验的验证。

Different DC voltage ratios can achieve multilevel voltage output for the hybrid cascaded inverter. But this scheme is suffered from the problems of the backward flowing energy and the unbalance capacitor voltage. This paper proposed a two-step control algorithm to solve these problems. First, different duration of the main inverter is chosen. Second, right zero-sequence voltage is injected to the conditioning inverter. As a result, the DC-bus capacitors＇ voltage can keep balanced, while the quality of the output voltage waveform can be improved. The simulation and experimental results verify the validity of the proposed control method.