改进的新型Ⅱ型不对称CHB逆变器调制策略

Modified New Modulation Strategy of Type Ⅱ Asymmetric Hybrid CHB Inverter

级联H桥多电平逆变器具有高质量的输出特性及实用性,然而传统的不对称级联H桥多电平逆变器的调制策略会产生电流倒灌及能量反馈的问题。针对该问题,提出了一种单极倍频的Ⅱ型不对称级联H桥逆变器的调制策略,对该调制频率下所得脉冲进行分区间的逻辑运算与组合,不仅可以解决传统调制策略中电流倒灌和能量反馈问题,而且最大开关频率比传统调制策略降低了1/2,同时改善了逆变器输出电压波形的谐波特性,保证了输出电能质量和效率。所搭建的仿真模型和实验结果均证实了该调制策略的可行性和有效性。

Cascade H-bridge multilevel inverter has high-quality output characteristics and practicability, whereas, the traditional modulation strategy of asymmetric cascade H-bridge multilevel inverter can cause problems of current inversion and energy feedback. To solve these problems, we proposed an unipolarly double-frequency modulation strategy of type-Ⅱ asymmetric hybrid cascaded H-bridge inverter, in which the sub-regional logic operation and combination were conducted at the modulation frequency. As a result, not only the problems of current flow backward and energy feedback can be solved in traditional modulation strategies, but also the maximum switching frequency can be reduced by 50%. Moreover, the harmonic characteristics of output voltage waveform can be improved, and the quality and efficiency of the output power can be ensured. The simulation models and experimental results show that the modulation strategy is feasible and effective.