Decentralized Voltage Regulation in Islanded DC Microgrids Based on a Modified Droop Control using Superimposed AC Voltage

The conventional droop control is a widely-used technique in load sharing among Distributed Generator (DG) units in islanded DC Microgrids (MGs). This method provides Plug-and-Play (PnP) capability for DG units; however, poor load sharing accuracy and unregulated voltage are two shortcomings of that. This article proposes a novel control system in islanded DC MGs to provide simultaneous regulated voltage and accurate load sharing. The method utilizes a modified droop control technique in a decentralized manner. The proposed control system injects a superimposed AC voltage to the network that carries a frequency proportional to the master DG unit output current. The injected voltage adjusts an added a term to the conventional droop control named as the voltage compensation term in order to cancel voltage changes. This term adjusts terminal voltage of DG units proportional to the frequency of the superimposed AC voltage. The performance of the proposed control system is validated via a set of simulation studies using PLECS, and the experimental results confirm the viability and feasibility of the proposed control system.