Efficient energy management and robust power control of a stand-alone wind-photovoltaic hybrid system with battery storage

This paper reports a novel efficient output power control strategy of an electric generation hybrid system (EGHS). The investigated hybrid system consists of two renewable energy sources associated to wind energy conversion (WEC) and photovoltaic (PV) subsystems, a battery bank and a variable load. The main control objectives are, on the one hand to regulate the hybrid system output power so that the total demand is satisfied, and on the other hand to extend the battery life cycle by maintaining its state of charge within limited values in order to avoid the blackout. For that reason, an energy management strategy is developed by determining the different operating modes of both subsystems. Accordingly, the dynamic model of the considered hybrid system is presented using the established switched parameters for different environmental conditions, which may include not only the atmospheric variations but also the load changes. Moreover, the proposed control law is designed by combining the features of both sliding mode control (SMC) as a robust controller and the integral action to reduce if not eliminate the reaching phase. The stability of the controlled hybrid system is demonstrated using the Lyapunov function. Furthermore, several simulations are investigated, and compared to those of the standard SMC, for two different cases of dynamic environmental conditions including not only random data but also a real climatic data of Errachidia city situated in south eastern of Morocco. Consequently, simulation results prove that the proposed strategy shows more robustness against the environmental conditions changes and fast response, compared to SMC controller, for switching from power regulation to maximum power conversion depending on the activated operating mode.