Frequency control improvement of two adjacent microgrids in autonomous mode using back to back Voltage-Sourced Converters

Typically microgrid is composed of Distributed Generators (DGs), storage devices and loads which can be operated in grid-connected or islanding mode. Microgrid brings merits to both suppliers and consumers; hence, there would be a lot of microgrids at the distribution level with different load curves and DG types in near future interchanging their surplus/shortage of supply with each other or the utility grid. Upon inception of a fault in an individual macrogrid, it would be disconnected from the utility grid and operates in an autonomous mode. For the microgrids with all inverter-based DGs, the frequency maybe considerably deviated from the nominal value upon disconnection from the utility-grid; that is impermissible for consumers. In this paper, the interconnection of two adjacent inverter-based microgrids with different frequencies is proposed, using Back to Back Voltage-Sourced Converters (BTB VSCs) with local controllers in order to maintain the frequency in emergencies. By application of the proposed algorithm, two microgrids could play the role of an auxiliary supply/demand for each other without the necessity of implementing a communication link between the two microgrids. Simulation results show that the BTB VSCs with the proposed control strategy can effectively improve the frequency control task of the two microgrids simultaneously.