A Distributed Current Sharing Strategy for Islanded AC Microgrids Based on Low-Bandwidth Communication

Abstract

Bus voltage regulation and current sharing are significant to ensure the normal operation of islanded microgrids. In this paper, a low-bandwidth communication (LBC)-based distributed current sharing strategy for islanded ac resistive microgrids is proposed, especially when the wire impedances of parallel-connected inverters are mismatched. In a general case, all the balanced, unbalanced and harmonic components of load current should be shared accurately. Therefore, in the local controller, those components of inverter output currents are extracted and regulated to follow the component average values generated based on LBC. To guarantee the bus voltage regulation, the influence of current sharing loops on voltage references is eliminated by subtracting the average voltage reference compensation from the current sharing controller outputs. A simplified inverter small-signal model is established, based on which the system stability is analyzed. Besides, the steady-state bus voltage regulation performance is discussed. The simulation in MatLab/Simulink is used to demonstrate the current sharing performance and bus voltage regulation ability. A hardware-in-loop platform of an ac microgrid prototype is built, where the power stage is in a real-time simulator and the controllers are implemented with DSPs. The results validate the effectiveness of the proposed strategy.