Battery Management System with Balance Circuit for Multiple Battery Module System

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The electrical vehicle and large scale energy storage system demands numerous battery modules in series. However, inevitable non-consistent manufacture makes battery module unequal internal resistance and capacity. The mismatch will be amplified as the increase of charge and discharge cycles. Ignore of this phenomenon will worsen the unbalance from cell to module level, resulting the problem of over charge or discharge. It has to correct this mismatch for ensuring the storage capacity. The objective of this thesis is to develop a battery management system (BMS) for a large battery system constituted with series battery modules. The BMS contains a Hierarchical Power Management System (HPMS) and a Hierarchical Energy Balance System (HEBS). HPMS is divided into the Cell Monitor Unit (CMU) and the Battery Management Unit (BMU). CMU is responsible for monitor of battery voltage and temperature and communication with BMU. BMU is responsible for calculation of state of charge (SOC), measurement of charge and discharge current and temperature protection of whole battery system. BMU also communicates with CMU to acquire all cell status. HEBS consists of cell balance circuit (CBC), module balance circuit (MBC) and battery group balance circuit (GBC). CBC, MBC and GBC are responsible for the balance of cell, module and group charge capacity, respectively. This thesis will draw up a 200kWh system and build a 40kWh system. The effectiveness of the proposed technology is confirmed with some simulation and experimental results.