Broadband Active Common Mode EMI Suppression of a GaN Motor Inverter With Adaptive FIR Filters Using Delay-Compensated Gate Control Signals

Due to advances in power transistor technologies, higher switching frequencies and steeper switching slopes are used in motor inverters to achieve higher efficiency and power density. However, this leads to increased electromagnetic interference (EMI). Conventional passive filter topologies can use a considerable amount of space and contain heavy components, reducing overall power density. To minimize volume and weight of passive filters, active EMI filters can be used. In this work, a novel EMI cancellation method for pulsewidth modulation controlled three-phase motor inverters is presented in a feasibility study. This method injects a cancellation signal by applying a filter to the digital transistor control signals of the motor inverter. By slightly delaying the control signals before they reach the transistor gates, the time required to synthesize and inject the cancellation signal can be compensated. The digital filter parameters are adapted continuously based on the measured noise signal to achieve maximum filter performance. First, the new method is described in general. After that, the applicability to power electronics is discussed. For demonstration, the system is applied to a motor inverter with GaN transistors to reduce the conducted common mode EMI at the input side of the inverter. The results are shown and discussed for different operation modes.