Hybrid DC Link Voltage Balancing For Two-Leg Five-Level Neutral Point Clamped Inverter

This paper proposes a Hybrid DC link voltage balancing of a 2-leg 5-level Neutral Point Clamped (NPC) inverter. The scheme uses a combination of active (hardware) based and software (modulation) based techniques to achieve a balancing solution with enhanced power quality performance. The active balancing scheme is implemented using a Fly-back auxiliary circuit that is coupled to the non-adjacent DC bus capacitors. The balancing circuit uses less power electronics components compared to alternative active balancing approaches. The complementary soft balancing is composed of three types of modulations to produce output waveform with improved total harmonic distortion performance. The applicability and proof of merits have been demonstrated by simulation of a Ladder transistor clamped NPC inverter under passive load.