Neutral point voltage-balanced control method based on discontinuous pulse width modulation for a NPC 3-level inverter

A neutral point voltage-balancing control algorithm is proposed for a neutral-point-clamped (NPC) three-level photovoltaic (PV) grid-connected inverter. The mathematical model of the neutral point current was deduced. The influence on the neutral point voltage for discontinuous pulse width modulation(DPWM) methods was analyzed. Comparison of the error between feedback neutral point voltages and the hysteresis width was used to choose a DPWM method to control the neutral point voltage. Simulation and experimental results verify the correctness and validity of the proposed neutral point voltage-balancing control algorithm.