Distributed Control Strategy of DC Microgrid with CPL Based on Convex Relaxation Method

For the direct current(DC) microgrid contanining constant power loads(CPLs), this paper proposes a novel distributed control strategy employing the convex relaxation approach, which enables the system to stabilize at the position of the optimal power flow(OPF) solution. For the non-convex OPF problem, the first step is to convexify it using an appropriate convex relaxation method and verify the accuracy of the proposed convex relaxation method at the same time. Secondly, the Karush- Kuhn-Tucker(KKT) optimality conditions of the relaxation problem are solved, and the results are equivalently transformed to identify the synchronization term that can be utilized in the control strategy, so as to achieve distributed control under optimal power flow. Finally, the proposed control strategy is verified using simulation examples and numerical analysis.