多电平电压源逆变器降低共模电压的脉宽调制策略的研究

PWM algorithm for multi-level voltage source inverter with reduced common mode voltage

多电平逆变器因为存在的开关状态多,因此其调制方法也较为复杂。通过选择适当的开关状态,部分共模电压降低调制方法(PCMVPWM)能将共模电压降低到直流侧电源的1/3,而完全共模电压消除调制方法(FCMVPWM)能够完全消除共模电压。本文主要揭示了这两种调制方法与基于载波的脉宽调制的关系并进行仿真比较。最后,在实验室建立的NPC三电平逆变器的原型机上对算法进行了实验验证,结果表明该调制方法能够有效地降低共模电压。

A pulse-width modulation scheme for a multi-level voltage inverter with reduced common-mode voltage is proposed in this paper. Multi-level inverter modulation is relatively more complicated because of the increased number of DC voltage levels and redundant switching states available. By choosing proper voltage vector, the common mode voltage can be reduced to one third of the voltage of one de cell by using partial common mode voltage reduce PWM （PCMVPWM）, and can be eliminated entirely by WM）. Among the all switching states in the multi-level using full common mode voltage reduce PWM （FCMVP- inverter, the two PWM strategies use only part switching states. The relationship between the two PWM strategies and carrier based PWM strategy is investigated. The harmonic characteristics and common mode voltage are given and compared in detail between the three modulation mode. The strategies have been confirmed by both simulation and experimental results obtained using neutral point clamped three-level inverter.