混合级联 H 桥逆变器的改进型调制策略

针对混合级联 H 桥逆变器,在采用混合载波层叠调制策略时,虽可以解决电流倒灌的问题且逆变器输出电 压的波形质量良好,但逆变器的低压单元会出现功率不均问题,提出了一种改进型混合调制策略;以混合级联九电 平逆变器为例,策略的高压单元采用调制波为正弦波的阶梯波调制;将两个低压单元的调制波分别进行调整再对 其进行脉宽调制(PWM),通过 PWM 调制可以得到两个低压单元各自开关元件的脉冲信号,利用该脉冲信号的对 称性对其进行逻辑运算,重新分配低压单元脉冲信号;首先进行仿真分析,对两种调制策略在同一条件下搭建仿真 模型并运行可得出相应的结果,接着进一步对改进型混合调制策略进行实验验证;通过仿真分析和实验验证可以 证明改进型混合调制策略在保留混合载波层叠调制策略优势的基础上,可减少载波,简化了调制过程,使输出电压 达到倍频效果,还可以在 1 / 2 个调制波周期内解决低压单元功率不均问题。

An Improved Modulation Strategy for Hybrid Cascaded H-bridge Inverter

For the hybrid cascaded H-bridge inverter, when using the hybrid carrier cascade modulation strategy, although the problem of current backfilling can be solved and the waveform quality of the inverter output voltage is good, the lowvoltage unit of the inverter will have the problem of uneven power. Based on this, an improved hybrid modulation strategy was proposed. Taking the hybrid cascaded nine-level inverter as an example, the high-voltage unit of this strategy adopted step-wave modulation whose modulation wave was a sine wave. The modulation waves of the two low voltage units were adjusted respectively and then the pulse width modulation ( PWM) was carried out. The pulse signals of the switching components of the two low voltage units were obtained through PWM modulation. The logic operation was carried out by using the symmetry of the pulse signals and the pulse signals of the low voltage units were redistributed. Firstly, the simulation analysis was carried out, and the corresponding results were obtained by building simulation models and running the two modulation strategies under the same condition. Then, the experimental verification of the improved hybrid modulation strategy was carried out. Through simulation analysis and experimental verification, it is proved that the improved hybrid modulation strategy can reduce the carrier, simplify the modulation process, make the output voltage achieve frequency doubling effect, and solve the problem of power imbalance of the low voltage unit within 1 / 2 modulation wave period while retaining the advantages of the hybrid carrier cascade modulation strategy.