Common-Mode EMI Analysis With Active CMV Cancellation in Neutral-Point-Less H-Type Inverter

Pulse width modulated inverters utilizing wide bandgap devices enhance motor drive efficiency by enabling higher dc-link voltages and switching frequencies. However, these advantages also lead to increased common-mode electromagnetic interference (CM EMI) noise. Conventional two-level six-phase inverters aim to reduce CM EMI by canceling common-mode voltage (CMV), ideally achieving zero CMV. The effectiveness of this approach is, however, limited by CMV mismatch issues, such as desynchronization and variations in CMV rise times, under two-level operations. This article analytically and experimentally investigates the active CMV cancellation capability under three-level operation in a neutral-point-less H-type (NPL.H) nverter. Despite the challenges associated with CMV mismatches, the three-level operation of the NPL.H inverter enhances CMV cancellation capability across the entire frequency spectrum, as it reduces the maximum CMV level by 33% compared to the conventional inverter. Experimental results show a 21% reduction in CMV magnitude within the 300 kHz to 30 MHz range and a 50% decrease in peak-to-peak ground current for the NPL.H inverter compared to the conventional inverter. Furthermore, the NPL.H inverter achieves a 62% reduction in the increase of CM EMI noise when both the dc-link voltage and switching frequency are doubled, in comparison to the conventional inverter.