Investigation of Common-Mode EMI in Three-Phase Split-Phase Inverter

Compared with the traditional two-level (2L) inverter, two-level Split-Phase topology (2L-SP) provides better cross-talk immunity without deadtime between the top and bottom devices. From the Common Mode (CM) EMI perspective, split inductors in 2L-SP tend to increase the CM noise path impedance and decrease the dV/dt across the device during the switching transition due to the interaction between split inductors and the semiconductor device’s parasitic capacitance. This phenomenon, in turn, reduces the dV/dt of the CM voltage, making 2L-SP topology a promising candidate with lower CM emission for Wide Band Gap (WBG) devices-based 2L inverters, switching at high frequency. However, the CM EMI of 2L-SP and its comparison with 2L have yet to be analyzed comprehensively. This paper investigates conducted CM EMI emission of a SiC-based 2L-SP three-phase inverter with SPWM. At first, the derivation of the CM equivalent circuit model through frequency domain analysis is presented. This is followed by a comparative study of CM emission of 2L-SP three-phase inverter on a hardware prototype for different values of split inductance. The results show that increasing split-inductance significantly lowers the CM magnitude with a maximum reduction of 17.85 dB.