Fast-switching GaN HEMTs in a 3L-ANPC topology can result in high transient voltage overshoot due to high parasitic inductances. In cases where further design optimization is not possible, effective use of the different possible switching sequences can achieve lower peak voltage transients. A modified full mode switching sequence formed by an additional high-frequency operation of the clamping switch is presented as an overvoltage mitigation strategy at high voltage and high current. A turn-on and turn-off transient severity analysis is presented based on experimental three-level double pulse test results of a GaN HEMT equipped three-level ANPC phase leg operating at 700 V DC. Based on the analysis, a current-dependent switching sequence selection is proposed to minimize the resulting peak voltage transients for continuous inverter operation.
