Transformerless Bidirectional Inverter for Residential Battery Storage Systems

A bidirectional inverter is proposed based on a two phase Neutral Point Clamping type 2 (NPC2) topology combined with a grounded buck boost inverter. The proposed system can work without the need of a transformer thanks to the combination of the topology, switching pattern and inductive filter that prevents the discharge of parasitic stray capacitance to ground. The inverter has the ability to operate as a back-up system as well as a grid-tied system. The structure of the NPC2 supports independent loads in each phase, enabling transformerless operation in split phase power systems such as 240V/120V, the default residential system in the US.