An Integrated EMI Filter Scheme for Paralleled Inverter with Zero-CM PWM Algorithm

Motor drive system generates harmful differential mode (DM) and common mode (CM) electromagnetic interference (EMI) when it is working. To solve this problem, the integrated EMI filter scheme for paralleled inverter using zero-CM pulsewidth modulation (PWM) algorithm is proposed in this article. The zero-CM PWM algorithm and the coupled inductor constitute a holistic solution for the ac side EMI suppression. By using the zero-CM PWM algorithm, the CM leakage current of the system can be suppressed without adding additional CM EMI filter and only DM EMI needs to be considered. In addition, the DM inductor is naturally integrated in the coupled inductor, leakage inductance of the coupled inductor instead of the discrete DM inductor is used as the DM inductor which has less restrictions on the inductor material. The DM EMI filter can be constructed by just adding DM capacitors. Thus, using the integrated EMI filter scheme has advantageous over traditional scheme since the CM EMI filter is omitted and only DM capacitor is added which can simplify and reduce the size of EMI filter in the ac side and has the potential to increase the power density of the system since other solutions require both the DM and CM EMI filter.