PWM逆变器输出端共模与差模电压 dv/dt滤波器设计

PWM逆变器直接驱动电机时会产生较高dv/dt的共模电压,并由此产生轴承电流和共模漏电流以及严重的电磁干扰(EMI).特别是当逆变器通过长线电缆与电机连接时,由于电缆中分布参数的影响,会在电机端产生电压反射现象,从而在电机端会产生2倍以上的过电压,导致线圈绝缘失败.本文通过对PWM逆变器驱动电机系统产生的共模以及差模电压分析,提出了一种改进型的逆变器端无源滤波器,并给出了参数的设计方法.与传统的滤波器相比,该滤波器可对共模及差模电压dv/dt同时起到抑制作用,从而减小了由此产生的负面效应.实验结果验证了该滤波器的有效性.

Design of Common-Mode and Differential-Mode Voltage dv/dt Filter at PWM Inverter Output Terminals

When motor was directly connected with PWM inverter, the common-mode voltage with a high dv/dt value would be brought which was thought to have relations with the producing of bearing current, common-mode leakage current, and serious electromagnetic interfere (EMI) issues. Especially, when motor was connected with inverter through a long cable, because of the effects of distribution parameters existed in cable, voltage reflection would be occurred at motor terminals, hence resulting in the voltage at motor terminals be doubled and leading to the winding insulation failure. In this paper, an improved inverter side passive filter was proposed on the bases of analysis of common-mode and differential-mode voltage, and a detailed design procedure of parameters was given. Compared with the conventional filter, the proposed filter could mitigate dv/dt value of common-mode and differential-mode voltage simultaneously. Thus, the side-effects accompanied with them were reduced. The validity of proposed filter was supported by the experimental results.