Study On Active Common-Mode EMI Filter For PWM Inverter

As the development of power electronics and control technology, the performance of inverters using pulse width modulation (PWM) has been gradually improved. and it has been applied in much more fields, such as PWM drives, UPS etc. Using high-frequency switching power semiconductor devices can significantly accelerate the process of dynamic response of the inverters, thus improve the performance of the system. However, high-frequency pulse produced by these switchers contains a lot of dv/dt, di/dt,which generate intensively EMI. In practical equipment, common mode EMI is the main component of the conducted EMI and the radiated EMI. Therefore, common mode EMI has become the major subject that should be solved.This paper introduces a original active common mode EMI filter which can compensate common mode current produced by inverters, thus achieve the purpose of restraining the interfere of common mode EMI. The main advantage of this simulation compensation circuit is that it is drived directly by the detected common mode current signal, which is amplified to compensate the common mode current.This paper firstly collects the signal of common mode current, through the coupling of the common mode transformer, we can obtain common mode current at the sub-side of the transformer as drive signal. Secondly, to design compensate circuit. This paper adopts a couple of high frequency complementary transistors as the working transistor. The DC-bus voltage provide the bias voltage for them. Adjusting working parameters to ensure that compensation circuit works in appropriate region directly determines the effect of compensation. The debug of the compensation circuit can be divided into two parts, including the debug of driving part and the debug of the compensation circuit.In the end, a platform of simulation is built to restrain the common mode current on the basis of topological configuration of the compensation circuit. The results of the testing and the experiments shows that interfere of common mode is greatly restrained when the PWM inverters is compensated by simulation compensation circuit. The result demonstrates the validity of this method presented by the paper.