Anti-EMI Noise Digital Filter Design for a 60-kW Five-Level SiC Inverter Without Fiber Isolation

Silicon carbide (SiC) power devices are beneficial to the converters in terms of size reduction and efficiency increase. Nevertheless, the fast switching of SiC devices results in more serious electromagnetic interference (EMI) noise issue. Optical fibers based isolation provides a reliable solution to block the EMI noises from the power circuit to the control circuit but with additional cost and size penalty, especially for multilevel converters. This letter aims at the digital filters based solution to suppress the sampling noise caused by EMI without any extra hardware cost. An improved median filter and a novel magnitude bandpass filter are proposed. The design tradeoffs among noises filter capability, delay effect and the computation time have been discussed for proposed filters. The anti-EMI noise function of proposed filters has been experimentally verified in a 60-kW five-level SiC inverter.