Single phase ZVS PWM NPC inverter

This paper presents a zero-voltage, pulse width modulated, NPC inverter, with active voltage clamping using only two auxiliary switches. The structure is particularly simple and robust. It is very attractive for high-power applications, single or multiple phases, due to neutral point accessible at the NPC topology. Switching losses are reduced due to implementation of the simple active snubber circuit that provides zero-voltage-switching conditions for all switches, which includes the snubber auxiliary ones. When applied to NPC, the soft commutation allows high frequency commutation even for high voltage input, which reduces output filter size and improve the pass-band frequency. Its main features are simple modulation strategy, robustness, low weight and volume, low harmonic distortion of the output current and high efficiency. The principle of operation for steady-state conditions, mathematical analysis, and experimental results from a 1.5kVA laboratory prototype are presented.