Decentralized Secondary Controller in Islanded DC Microgrids to Enhance Voltage Regulation and Load Sharing Accuracy

Abstract

The conventional droop control is a widely-used technique to share loads in islanded low voltage (LV) DC networks, known as autonomous DC Microgrids (MG), using a fully-decentralized control method. This method provides plug-and-play (PnP) capability for distributed generation (DG) units. However, it suffers from poor voltage regulation, and to get higher accuracy in load sharing (LS), more voltage drop would entail. While implementing centralized or distributed control is a solution to tackle this shortcoming, it sacrifices the PnP feature of DG units. Furthermore, due to the presence of communication links to a central controller or between DG unit controllers, less reliability occurs. Thus, more investigation to improve the performance of islanded DC MGs is needed. This paper studies simultaneous LS and voltage regulation through a decentralized control method. To verify feasibility of the proposed method, it is proved that by getting local feedback of the terminal voltages and adjusting the local controller parameters including droop control reference voltage, accurate LS and negligible voltage drop are concurrently achievable. In addition, an islanded DC Microgrid as a test system is simulated in MATLAB/Simulink to validate the proposed controlling system scheme.