电容箝位型非对称H桥五电平逆变器 正弦脉宽调制控制

为简化多电平逆变器拓扑结构、提高性能，构建了电容箝位型非对称H桥五电平逆变器。提出一种新型的锯齿载波交错正弦脉宽调制(sine pulse width modulation，SPWM)策略，通过在每个载波周期内控制电容充、放电时间相等，保证电容电压平衡。采用锯齿载波，在扩展的三相系统中，控制任意两相电压相对应的脉宽调制(pulse width modulation，PWM)脉冲对始终位于对应锯齿载波的起始(末尾)侧，消除了线电压中部分相邻“电平层”交叠的现象。对3种同类五电平逆变器及其对应的调制策略进行对比分析，构建的拓扑所用功率器件最少，等效开关频率为载波频率的2倍，电容电压平衡且波动幅度较小，线电压谐波含量最少。实验结果验证了该拓扑及其调制策略的正确性与有效性。

SPWM Control of Capacitor-clamped Five Level Inverter Comprised of Asymmetric H Bridge

In order to simplify the topology of the multilevel inverter and improve its performance, a capacitor-clamped five level inverter comprised of an asymmetric H bridge was established. A novel corresponding SPWM modulation strategy with staggered sawtooth carriers was proposed. The capacitor voltage should be balanced because the time durations of charging and discharging are controlled making them equally in every carrier cycle. In addition, in the extended three-phase system, sawtooth carriers were applied to make the corresponding PWM pulse pairs from two arbitrary phase voltages commencing at the beginning or ending of the respective carriers. Therefore, the overlapping phenomenon of the neighbor pulse layers from line to line voltages is eliminated. Three types of the homogeneous five level inverters and their respective modulation strategies were analyzed contrastively. It is obtained that the number of power devices in the presented topology is in the least, and its equivalent switch frequency is twice of that of carriers’. The capacitor voltage could be balanced, and its ripple is smaller, and the line to line voltage harmonic is in the least. Finally, the experimental results prove the validity of the topology and its modulation strategy.