A Nonlinear Control of Energy Storage System-PV-Based Stand-Alone DC-Microgrid

In this paper, a nonlinear integral sliding mode control (ISMC) for Hybrid Energy Storage System (HESS)-based stand-alone DC-microgrid has been proposed. This hybrid system consists of a PV system, supercapacitor, and battery. A classical PI-based linear control strategy has been considered to control battery and supercapacitor systems, based on the decoupling of high- and low-frequency component to estimate reference current. Due to frequent discharge during operation, supercapacitor power can reach the lowest value, which affects controller performances and even makes the system unstable. Thereby, a nonlinear ISMC is performed as an inner loop controller to regulate the battery and supercapacitor powers. Also, the PI controller is implemented as an outer loop controller to regulate the DC-link voltage. As a result, the proposed control strategy has achieved high dynamic system performances.