DC–AC Bidirectional Converters for Application in Isolated Microgrids

This article sets out the design for control loops and the development of a 40-kW bidirectional converter for applications in isolated microgrids. This is the grid-forming converter, responsible for controlling the voltage and frequency of the microgrid. It is connected to an energy storage system and must have a bidirectional power flow. There is also a description of the topology and respective design of the control loops. Experimental results demonstrated the efficiency of the converter in controlling the charging and discharging current of the battery bank, the DC bus voltage of the converter, and the voltage and frequency of the AC microgrid system. Two units of this converter were installed in a real-time isolated microgrid at Ilha Grande (Grande Island), located in the northeast of Brazil. The purpose of this project was to replace the inverter/rectifier devices previously used to provide a bidirectional power flow. Tests conducted with the new converter showed a significant improvement in power quality, in the efficiency of the electric power system, and reduced installation costs.