三相四桥臂下抑制共模干扰的SPWM策略

传统的三相三桥臂逆变器因电路不对称而产生了很大的共模电压和电流。本文介绍了三相四桥臂结构对逆变器共模干扰抑制的原理和为了达到平衡采用的载波移相SPWM控制策略，指出了该方法存在的调制指数被限定的缺陷。为了弥补该缺陷，本文提出了SPWM跳变后移的改进策略，阐述了该控制策略的理论依据及其实际效果。改进后的策略突破了原策略调制指数的限制，扩大了三相四桥臂逆变器载波移相SPWM控制策略的应用前景。

The Study of SPWM Control Strategy to Reduce Common-Mode Interferences in Three-Phase Four-Leg Inverters

Due to the asymmetry of the structure, the traditional three-phase three-leg inverters produce huge amount of common-mode(CM) voltage and CM current. This paper introduces the theory of reducing CM interferences by using the three-phase four-leg structure and the SPWM control strategy of carrier phase shifting which is applied on the purpose of balance in inverters. The modulation index limitation in this method is also pointed out. In order to solve the problem, the measure for improvement is put forward, in which trip point of SPWM is delayed when zero-state appears. The theoretical basis and simulation result of the control strategy is analyzed. The improved method breaks through the modulation index limitation and widens the application of the SPWM control strategy in three-phase four-leg inverter.