MODIFIED BI-DIRECTIONAL CUK CONVERTER FOR CELL BALANCING USING PI AND FUZZY LOGIC CONTROL METHOD

Abstract

In multi-cell battery packs, the Battery Management System (BMS) is the safety system of the battery and is responsible for keeping values such as voltage, current, and temperature within safe limits. One of its most important functions is to eliminate the imbalances caused by the voltage difference between the battery cells connected in series. Active and passive topologies are used to compensate for voltage differences between cells. In passive cell balancing, excess energy is dissipated as heat energy over a resistor, while in active cell balancing systems, excess energy is transferred between cells, thus increasing efficiency. In this study, a modular and converter-based active balancing topology is presented. In the design, there are insulated cuk converter modules that perform bidirectional energy transfer corresponding to each battery cell connected in series. Such a modular design has good flexibility and extensibility for balancing series-connected battery cells. By designing an isolated bi-directional cuk converter circuit and equalization controller, five battery cells connected in series were tested separately in charging, discharging, and idle states. The PI control and fuzzy logic control (FLC) methods have been applied to the proposed topology and verified with the Matlab/Simulink program.