In this paper, a suboptimal controller is proposed for a DC microgrid interfaced with constant power loads (CPLs). Towards this end, a nonlinear model of the DC microgrid is utilized to define an optimal tracking control problem based on a discounted quadratic infinite-horizon cost function. The problem is solved using a State-Dependent Riccati Equation (SDRE) technique. This feedback control technique can regulate the load voltage to its desired value while guaranteeing stability of the closed-loop system. The performance of the proposed SDRE tracking controller is valuated and compared with two other well-known nonlinear controllers, feedback linearization and backstepping, through some numerical simulations. The obtained results verify the effectiveness of the proposed SDRE controller.
