Current control for a supercapacitor-based battery equalization system

Abstract

This paper presents a novel supercapacitor-based energy equalization system and discusses a new equalization current control method. The proposed battery equalization system is composed of a bidirectional boost–buck circuit, a switch matrix, and a supercapacitor, which can realize stable electric current transmission between batteries and supercapacitors. The buck or boost mode of the circuit is triggered automatically based on the threshold of the voltage drop between the battery and the supercapacitor. A modified control logic of the metal-oxide-semiconductor field-effect transistor is proposed to improve the efficiency of the circuit, and a model predictive control (MPC) algorithm is designed to track the target current. Simulation results indicate that for a conventional electric current transmitting circuit, the current fluctuates violently under a fixed pulse width modulation duty. In contrast, the proposed supercapacitor-based energy equalization system tracks the target current well under the control of the MPC controller. In a wide operating range, the transmission efficiency of the new energy equalization system with the modified control logic is 13.0% higher than that of the conventional electric current transmitting circuit with the original control logic.