Design of a novel filter topology with active impedance regulator for three-phase motor drive system

This paper presents a novel hybrid output filter topology for inverter-motor system. It is composed of a conventional LC filter cascaded with an active motor CM impedance regulator. The active circuit, utilizing an integrated high-voltage op-amp, is very efficient in decreasing the motor CM equivalent capacitance as well as damping the high common voltage on the motor terminal. Therefore, the motor impedance is also used as part of the filter and the common voltage can be eliminated dynamically in the active impedance regulator by feedback control. Experimental verification of the filter topology is provided with a laboratory system consisting of a 380 V inverter and a 0.37kW induction motor.