Adaptive PWM for four-switch three-phase inverter

An adaptive pulse width modulation (PWM) strategy is proposed for four-switch three-phase inverter (FSTPI) to improve the performance and simplify the algorithm. The FSTPI has a split DC-link and one phase of the AC load is connected to the neutral point. The conventional space vector PWM has a limited performance in the low-frequency region since the phase currents are unbalanced due to the neutral-point voltage fluctuation caused by the phase current flowing through the capacitors. To solve this problem, an adaptive PWM considering the neutral-point voltage fluctuation is proposed. Moreover, sector identification is unnecessary thus the algorithm is simplified. Experimental results demonstrate the validity and feasibility of the proposed strategy.