Secondary Control Method for Standalone DC Microgrid with Improved Voltage Regulation, Load Sharing, and Line Loss

Abstract

Conventional droop control in DC Microgrid with secondary control strategies are proposed in the existing literature. If droop is the only control variable, a trade-off between voltage regulation and proportional current sharing exists. To overcome this, a voltage shift is also introduced to achieve low voltage regulation and proportional current sharing simultaneously. However, line losses need to be reduced along with these. We propose an online algorithm which finds an optimal voltage shift while keeping the droops constant. The cost function used for this optimization accounts for voltage regulation, ideal current based proportional current sharing error and line losses. It is assumed that each distributed energy resource receives information of droop gains, output current of other distributed energy resources and DC bus voltage to compute the optimal voltage shift. Detailed analysis and design procedures are explained, and MATLAB simulations are performed for 400 V DC microgrid system to justify the effectiveness of the proposed control method.