An Active EMI Filter Based on Midpoint Current Detection Used in Motor Drive System

This paper analyzes and designs a common-mode (CM) active filter (CM-AEF) based on neutral point current detection for suppressing electromagnetic interference (EMI) in motor drive systems. It takes the neutral point of the DC side of the tested equipment as the reference point and uses a shunt resistor circuit to detect the CM current. An operational amplifier is used to form a current source circuit to generate compensating current. Compared with traditional current detection active filters, this filter does not require the use of a transformer and does not need noise separation, thus further reducing the volume of the active filter. The working principle of the filter is first analyzed, and then experimental verification is conducted. The experimental results show that the designed AEF has good attenuation capability for CM EMI in the frequency band of 150 kHz to 30 MHz.