Voltage control in a DC islanded microgrid based on nonlinear disturbance observer with CPLs

Abstract

Abstract In this paper, a nonlinear voltage control for a DC islanded microgrid (MG) is proposed. This control method is a new nonlinear decentralized backstepping based strategy for voltage control of DC MG based on Sepic converter with nonlinear loads such as constant power loads (CPLs). The effect of CPL is to realize a load with negative resistance for DC MG that impacts the power quality of the power system and causes negative damping. The major purpose of the proposed controller is to improve the transient performance of MG with the Plug and Play (PnP) feature in the presence of load change and CPL. To consider the effects of such loads on the proposed control method, a nonlinear disturbance observer (NDO) along with backstepping controller is introduced to estimate the uncertain terms such as CPL and load currents as well as the current transferred between DGUs. The proposed method only measures the local voltage and current quantities without any need for additional information about the grid topology and its parameters. This method successfully regulates the point of common coupling (PCC) voltage. The stability of the method is proved via Lyapunov theory and its features are verified with simulation and some experiment tests.