Power Flow Management of Interconnected AC Microgrids Using Back-to-Back Converters

Abstract

Microgrids have limited renewable energy source (RES) capacity, which can only supply a limited amount of load. Multiple microgrids can be interconnected to enhance power system availability, stability, reserve capacity, and control flexibility. This paper proposes a novel structure and control scheme for interconnecting multiple standalone microgrids to a common alternating current (AC) bus using back-to-back converters. The paper presents a high-level global droop controller that exchanges power between interconnected microgrids. Each microgrid considered in this paper comprises RES, battery, auxiliary unit, and load. The battery maintains the AC bus voltage and frequency and balances the difference in power generated by the RES and that consumed by the load. Each microgrid battery’s charge/discharge is maintained within the safest operating limit to maximize the RES power utilization. To achieve balance and continuity of supply, renewable power curtailment and auxiliary power supplement mechanism is designed based on the bus frequency signalling technique. Performance evaluation shows that the proposed controller maximizes renewable power utilization and minimizes auxiliary power usage while providing better load support. The performance validation of the proposed structure and control strategy has been tested using MATLAB/Simulink.