A Current Protection Strategy for NPC-TL Half-Bridge Inverters

The output side of inverters connected with a transformer is an inevitable and severe work condition. This paper studies a novel cycle-by-cycle (CBC) current limiting technology for Neutral Point Clamped (NPC) Three-level (TL) Half-bridge inverter connected with a transformer. This current limiting technology can protect the inverter from the surge magnetizing current of the transformer at the time of the output relay turned ON. The novel CBC strategy is analyzed and compared with the traditional solution in details. Finally, simulation and experimental results are presented to verify the proposed control and analysis.