Two layer control strategy for voltage stability of renewable energy based direct current microgrid

Power system stability of an island direct current (DC) microgrid is crucial when it is equipped with renewable energy sources which are intermittent in nature. It requires a robust control mechanism which promises the constant power delivery to the user specially during extreme events. For this purpose an advance nonlinear controller i.e. double integral sliding mode control (DISMC) has been proposed for a three source DC microgrid which include photovoltaic (PV), battery and ultracapacitor (UC) connected to DC-DC converters. Energy management among the sources is accomplished by the state of charge (SoC) based mechanism which is responsible to generate the reference values for energy storage system (ESS) encompass battery and UC. The proposed controller is simulated in MATLAB/Simulink along with other comparison controllers including Lypunov redesign (LRD) and sliding mode control (SMC). It outperforms the LRD and SMC in terms of minimal overshoot and undershoot. The settling time and steadystate error are 0.025 seconds and 0.35 V respectively, highlighting the tight voltage regulation of the DC bus, which translates to enhanced power system stability.