An analysis of the three-level neutral-point clamped (NPC) inverter with two independent DC sources

In addition to its other merits, the three-level neutral-point clamped (NPC) inverter allows two dc sources, which may be an advantage in photovoltaic systems for enhanced maximum power-point tracking capability and higher energy yield. This paper takes a look at the impact of power mismatch between the two dc sources on the performance of the inverter. The paper develops a mathematical model for the calculation of the inverter mid-point current (and its harmonic components), for three different pulse-width modulation (PWM) strategies.