A Hybrid EMI Filter Design for Motor Drive System Based on Common-Mode Impedance Optimization

The motor drive system is a widely studied power electronics application, with significant attention given to its electromagnetic interference (EMI) issues. Passive EMI filters (PEFs), composed of inductors and capacitors, are commonly employed to mitigate EMI. However, the size and weight of conventional common mode inductors with high inductance tend to cause heating and power loss problems. An alternative solution is the implementation of active EMI filters (AEFs), which significantly reduce the inductance value of common mode inductors, resulting in a smaller filter size and improved power density and efficiency for the electric drive system. In this study, a hybrid EMI filter is designed for motor drive systems featuring certain ground parasitic common-mode (CM) capacitance. By optimizing the impedance relationship, the proposed filter effectively suppresses CM noise in the frequency range of 150 kHz to 1 MHz, achieving noise reduction of 20–30 dB.