Decentralized Energy Management and Voltage Regulation in Islanded DC Microgrids

Abstract

Battery energy storage systems (BESSs) are essential units in islanded dc microgrids (MGs) with tangible penetration of distributed renewable energy sources. These units play a crucial role in energy management and preferably should be controlled in a decentralized manner. In this regard, the conventional droop control is a well-known technique to implement a decentralized control for load sharing in the presence of various-sized distributed generator (DG) units and variable state-of-charge (SoC) level of BESS units. This method provides plug-and-play (PnP) feature for DG units; however, load sharing accuracy is poor, and voltage is unregulated. This article proposes a novel control system for energy management in islanded dc MGs while providing regulated voltage and highly accurate load sharing simultaneously in a decentralized way. The method uses the SoC level of BESS units in a modified droop control technique. A superimposed ac voltage on the nominal dc voltage of the network is used by the control system, bearing a frequency representing the network's load state. This frequency defines the operation mode of BESS units. Conducting simulation studies using piecewise linear electrical circuit simulation (PLECS) validates the effectiveness of the proposed control system. The experimental results confirm the viability and feasibility of the proposed control system.