A bidirectional converter control design to improve the performance of isolated microgrid

Abstract

The microgrids have been applied satisfactorily for the supply of energy to isolated places. In isolated microgrids, energy storage systems and dispatchable energy sources are fundamental for continuous operation, and for power balance. The dispatchable sources are useful as backup, for maintenance operations, and for battery bank equalization charges. Practical experiences in isolated microgrids that uses synchronous generator (driven by a prime mover) have a potential operation problem when working with rectifiers to charge the battery bank whenever the available renewable resources are not sufficient. This is due the generator reactance that causes voltage distortions at the generator terminals, power quality problems for the microgrid and, eventually, inhibition of rectifier operation whenever there is a thyristor switching. This paper proposes the design of a bidirectional DC-AC converter control loops for application in isolated microgrids, improving the power quality, efficiency and operation. In addition, the use of a bidirectional converter reduces energy conversion losses and reduces the costs of implementing the microgrid by replacing two pieces of equipment (AC-DC and DC-AC converters) for just a single one. The contributions of the paper are the design methodology of the control loops of a bidirectional converter, whose development and application in real environment allows it to perform as grid-forming converter in isolated microgrids.