Battery Management System Based on Vienna Rectifier

Ong, Le Yee (2022) Battery Management System Based on Vienna Rectifier. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Electric Vehicle’s charger is one of the vital equipment to supply electrical power to the Electric Vehicles (EV). In order to ensure the safety of EV, a high performance and reliable Battery Management System (BMS) is necessary to be developed. Today, EVs are categorized in a small distance range of 270 km. Therefore, the objectives of this project are included to design an on-board Level 2 EV charger and investigate its performance via MATLAB Simulink. For level 2 charging of EV’s battery, it requires 240 V and the power level at 19.2 kW which usually takes place in public and private facilities. Besides, the proposed project aims to develop a cell equalizer for the battery packs to balance the charge distribution for each cell in the battery pack. The proposed converter is known as a two-stage converter in which a three-phase Vienna rectifier is cascaded with a buck-boost converter. The gate signal of the Vienna rectifier is controlled by Hysteresis Current Control (HCC). The back-end buck-boost converter is controlled by a PI controller. The Constant Current Constant Voltage (CC/CV) technique will be applied to charge the EV batteries in order to prevent overcharging or discharging which in could bring damage to the EV batteries. One of the important parameters of the battery, i.e., State of Charge (SOC) provides critical information about its performance and lifetime. Consequently, SOC parameters are taken into account as the input for the BMS in order to perform the cell equalization. The switched shunt-resistor circuit is designed and integrated as a part of the system to perform cell equalization. The model of the proposed power circuit has been built, and the simulation results show the system able to maintain unity power factor at the source side. Besides, hysteresis current control technique gives the THD of the input current at 10.07%. The power generated for the on-board EV charger is 19.2 kW which fulfills the requirement of Level 2 charging. The CC/CV charging mode for EV batteries is also demonstrated for overcharging and overdischarging prevention by stopping charging process when any of the cells reaches the maximum SOC at 80%. On the other hand, the process of discharging will be terminated when any of the cells reaches its minimum value which set to 20% of SOC. The four cells with different SOCs which form a battery pack can be perfectly balanced during the process of cell equalization.