Modeling and Analysis of A Feedforward Current Based Active Common-Mode EMI Filter For Modular Multilevel Converters

Abstract

Modular Multilevel Converter (MMC) is becoming more and more popular in High Voltage Direct Current (HVDC) system recently since it can achieve high efficiency power conversion. However, numerous switching devices in MMC system generate severe Electromagnetic Interference (EMI) during its operation. Common-Mode (CM) EMI is generated by the high frequency fluctuation of voltage on the power devices and the parasitic capacitance in the system which may threaten the reliable operation of the system. EMI filters are commonly used for EMI suppression. To suppress the DC side CM EMI in MMC system, this paper proposed a feedforward current based active EMI filter. A 5-level MMC simulation platform is built in MATLAB/SIMULINK. The feasibility of this method is verified by simulation results and the CM EMI reduction could approach 20dB within several MHz with the proposed active EMI filter.