Autonomous Voltage Regulation and Current Sharing in Islanded Multi-Inverter DC Microgrid

Abstract

This paper presents an autonomous voltage control solution in islanded dc microgrid in a decentralized fashion. The dc bus voltage is regulated cooperatively by multiple renewable energy sources (RES) and energy storage units (ESUs) in different operation modes, automatically without relying on underlying communication. Unlike the existing droop control-based solutions that deal with the trade-off between bus voltage regulation and current sharing, we present a state-of-charge (SoC)-based current sharing method through the incorporation of SoC and capacity information into the double closed-loop control for ESUs. This effectively eliminates the dc bus voltage deviation, and simultaneously guarantees the SoC balance among individual ESUs. In addition, an off-maximum power point tracking algorithm is proposed for RES to manage their output generation for cooperatively maintaining the bus voltage stability in the case that the generation-demand balance cannot be regulated by ESUs alone. The suggested solution is assessed through a set of simulation experiments for a range of operational scenarios and its effectiveness is confirmed by the numerical results.