Method to minimize the low-frequency neutral-point voltage oscillations with time-offset injection for neutral-point-clamped inverters

This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time-offset to the three phase turn-on times. The proper time-offset is simply calculated considering the phase currents and dwell time of small and medium voltage vectors. The proposed method does not affect the outputs and there is no increase in the switching frequency. Further, it does not require additional hardware or complex calculations. Simulation and experimental results verify the validity and feasibility of the proposed strategy.