Bidirectional Synchronous H6 Inverter for Hybrid AC/DC Distribution System With Improved Light Load Efficiency

The overall efficiency of DC distribution systems may be impacted by the operation of the bidirectional inverter connected to the grid; one of its most critical components. When compared to high-demand industries, the typical load profile of such system in residential buildings is highly variable, including several periods of light-load. Therefore, this paper presents a method to overcome the reduced efficiency at light-load of bidirectional inverters integrated into a DC distribution system powered by renewable energy. Existing topologies are evaluated for obtaining optimal efficiency as well as an investigation of loss breakdown at light-load using analytic models and PSIM simulation. A novel synchronous H6 transformer-less topology is proposed. Simulation results show that the proposed topology can achieve an efficiency of 96.5% under full load and 98.3% under light-load. Efficiency improvements over a standard H6 topology are 4.5% under light-load and 1.5 % at full load. This is mostly due to reduced conduction and switching ON loss of MOSFETs used to replace diodes. When using the rectifier mode, similar levels of improvement are observed, with a 4% increase under light-load and a 1.2% improvement under full load conditions, respectively. Experimental results confirm the effectiveness of the proposed topology, showing nearly the same trend in improvement vs. the standard H6.