Optimal and Robust Control in DC Microgrids

Abstract

This paper presents an optimal and robust nonlinear control scheme to achieve trajectory tracking for disturbed nonlinear systems, which is applied for the control of power converters in dc microgrids. The state-feedback optimal controller synthesis is based on the solution of the Hamilton–Jacobi–Bellman equation, which considers the minimization of a cost functional (performance index), resulting in an efficient control strategy. The proposed methodology is used to efficiently regulate the power flow from renewable resources into the utility grid, to supply energy to loads, and to storage energy. Simulation results are presented to assess the performance of the proposed controller for a case study dc microgrid, where its adequate operation depends on the dc bus voltage regulation; hence, for guaranteeing such voltage regulation through the converter (inverter) connected to the utility grid, the optimal control scheme is in addition combined with a super-twisting controller (a robust sliding mode-based control technique) to enhance the inverter control strategy robustness.