A New Model Predictive Current Control Strategy for Hybrid Energy Storage System Considering the SOC of the Supercapacitor

Abstract

Proportional-integral (PI) control and model predictive control (MPC) are mainly utilized in battery and supercapacitor (SC) hybrid energy storage system (HESS) of dc microgrid. Unfortunately, the regulation time of the PI controller is long, while large current ripples are introduced by MPC when the system frequency is low. This article proposes a new model predictive current control (new MPCC) strategy for HESS based on MPC and PI controllers. This method reduces current ripples, and meanwhile, enhances system stability and rapidity. MPC is adopted as the outer loop and it calculates reference values for the inner PI current loop. Furthermore, the state of charge (SOC) of the SC is considered based on fuzzy control to optimize the reference power of the SC inner controller. First, the topology and mathematical model of HESS in the dc microgrid are analyzed. Then based on PI control and MPC, the new MPCC is proposed, and compared with MPC and PI methods, respectively. Finally, the fuzzy control method takes SOC of SC into account to optimize the SC reference current. Simulation and experimental results show that the proposed new control strategy could effectively decrease current ripples and dynamic processes and entirely perform the high energy density characteristic of batteries and high power density characteristic of SC.