新型PWM逆变器输出无源滤波器的研究

Research on a novel PWM inverter output passive filter

研究了变频器在长线传输时产生的过电压问题,理论分析表明,电动机端过电压与PWM变 频器采用的开关器件上升时间和PWM变频器与电动机之间的电缆长度密切相关:上升时间越短, 电缆长度越长,电压反射现象越显著,过电压也越高。为消除PWM变频器长线传输时在电动机端产 生的过电压等负面效应,提出了一种逆变器输出无源滤波器。实验研究验证了该滤波器能够将变频 器输出的PWM电压滤成近似正弦波,从而有效地抑制电动机端的过电压。这种滤波器还可以有效 降低共模电压。文中分析了这种滤波器的共模结构及其可以降低共模电压的原因,实验验证了设计 思想的正确性。同一种结构的滤波器能够同时消除差模dv／dt和共模电压,减小了滤波器的体积和成 本,结构简单,是一种消除逆变器输出负面效应的有效手段。

Over-voltage at motor terminals when long cables are connected between the PWM (Pulse-Width Modulation) inverter and the motor is investigated. Analysis shows that the over-voltage is dependent on the PWM rise-time of switching devices and cable length: shorter rise-time, longer cable, and higher over-voltage. For reducing over-voltage at motor terminals, an inverter output passive filter is proposed. Experiments show its validity. The common-mode configuration of the proposed filter is also analyzed and identified through experiments. A filter, which can not only eliminate over-voltage but also suppress common-mode voltage, is achieved, the differential-mode dv/dt and common-mode voltage can be solved synchronously, thus reducing the bulk and cost of the filter, and so it is an effective method for reducing adverse effects of the inverter.