Droop Based Secondary Controller for Islanded DC Microgrid with Line Loss Minimization

Conventional droop controllers achieve proportional current sharing with high droop gain, and low-voltage regulation with low droop gain. To obtain both the objectives, centralized, decentralized and distributed controllers are proposed in the existing literature. While minimizing voltage regulation and improving current sharing, the aspect of line loss has not been considered. This paper presents a distributed secondary controller (DSC) for droop-controlled standalone dc microgrid (DCMG) which optimizes the voltage regulation, current sharing and line losses in the system. Each distributed energy resource (DER) in the DCMG locally optimizes a cost function based on its voltage regulation, current sharing error and line loss by setting the droop gain. The proposed scheme is an online algorithm which finds an optimal droop gain for individual DER under an all-to-all communication topology. Each DER receives information of the droop gains, output current and bus voltage of other DERs. This information is used to update its droop gain. MATLAB simulations are performed for an 400V DCMG to demonstrate the effectiveness of the proposed controller.