Power Management and Control Strategy Based on Model-Free Control for Hybrid Energy Storage System

The hybrid energy storage system (HESS) integrating supercapacitor and batterie capitalizes on their respective merits of high power density and high energy density, enabling the smoothing of DC bus fluctuations and power balancing, hence has been widely applied in DC microgrids. Energy management and control stand as the central issues in HESS. This paper comprehensively considers the control at both system and device levels, proposing a power allocation strategy based on virtual impedance droop (VID) and a power control strategy based on the ultralocal model. A SoC (State of Charge) recovery strategy with frequency constraints is devised, building upon the traditional supercapacitor control based on virtual capacitance droop. Furthermore, the applied converter control method based on the ultralocal model significantly mitigates dependency on physical parameters, which enhances the robustness of the control. Ultimately, the efficacy of the proposed two-level energy management and control strategy is substantiated through simulations conducted in Matlab/Simulink.