Research on a High Frequency Active EMI Filter for Power Converters

本研究是关于一种由电晶体等有源元件与高频共模电流Transformer（CT）所组成的高频电磁干扰有源噪声滤波器，其优点及研究结果如下：1.体积和重量的1 / 10以下的小尺寸.与正常操作相比，实现了共模电流的2%以下。这意味着共模噪声和漏电流的降低.在3 MHz的工作频率下，共模EMI噪声降低了35 dB。该有源滤波器适用于1 MHz以下的低频EMI滤波器。因此，结合高频无源EMI滤波器的5 MHz以上的面积，小尺寸和高品质的EMI滤波器可以实现.该滤波器由一个小型铁氧体CT、两个互补晶体管和一个直流截止电容组成。因此，它可以产生非常经济的价格低于1.5美元。它不需要单独的电源，从逆变器的直流环节供电.在2kW PWM驱动系统中实现了1 W以下的低损耗.分析了变频电机驱动系统漏电流的产生机理和等效电路。利用仿真结果，可以对逆变器的dv/dt和电机杂散电容进行仿真设计.研制的EMI有源滤波器已应用于工业逆变器和家用空调驱动系统。

This research is concerned to a high frequency active noise filter of electromagnetic interference (EMI) composed of active devices as transistors and a high frequency common mode current transformer(CT).The merits of this filter and the results obtained in this research are as follows ;1. Small size under 1 / 10 of volume and weight is obtained.2. Under 2% of the common mode current compared to the normal operation is realized. The result means the reduction of the common mode noise and leakage current.3. The common mode EMI noise can be reduced 35dB under the area of 3MHz. The active filter fits for low frequency area EMI filter under 1MHz. So combining a high frequency passive EMI filter upper 5MHz area, small size and high quality EMI filters can be realized.4. The filter is composed of a small ferrite CT and two complimentary transistors and a DC cut capacitor. Therefore, it can produce very economical price as under 1$.5. It needs no separate power source by feeding the power from DC link of the inverter.6. Low loss under 1W in 2kW PWM drive system is realized.7. The mechanism and the equivalent circuit of the leakage current of the inverter motor drive systems are cleared. Using the results, dv/dt of the inverrers and motor stray capacitance can be designed by simulation.8. The developed EMI active filter is already applied to industrial inverters and home air conditioner drive systems.