Lithium Battery State Estimation And Balance Control For FSEC Racing Car

With the rapid progress of the country’s new energy industry,the participation of Formula Student Electric China(FSEC) has increasing day by day.The overall performance requirements to electric car are also rising.Battery management system(BMS) is the bottleneck to the improvements of the electic car for its’ lagging development.Under the reseach of Lithium cobalt oxide batteries’,which equipped by CSG-HRT15 E racing car, overall performance, a BMS which suitable lithium cobalt oxide battery was designed. Battery status can be monitored by the system in real-time and barrey cells in one battery pack can be balanced timely where necessarily. So that the reliability of the battery pack in the actual working conditions can be echanced effectively.In this paper, Lithium cobalt oxide batteriy was considerd as the research object. Some researches were carried out around the battery external characteristics.Open circurt voltage characteristic was acquired by several experiments. Rebound voltage was studied at different SOC(State of charge) stage, with which help,the parameters of the second order Thevenin model at different SOC stage were identified. Fitting parameters’ reliability were verificated by simulated the batteries’ actual working conditions voltage changement situation on MATLAB simulation platform.SOC was estimated thourge the combination of Unscented Kalman filter and battery second oder Thevenin model. And Square root unscented Kalman filter was introducd to increased the rubost of the filter for the covariance may became non-positive between the Unscented Kalman filter working process. Estimated the battery SOC in complex working condition and the result showed the square root unscented Kalman filter’s fitting accuracy was accuate. The estimation accuracy error was less than 1.5%.Considered the flyback transformer as the core structure of the banlance topology. Debugged and verified the balance circuit through Or CAD. Regarded battery SOC as banlance criterion and according to the battery’s real working condition, the balance strategy on battery pack charging or discharging last stage were layed down. Debugged and simulated the balance system and balance strategy by using MATLAB/Simulink platform. For various balance environments, the balance structure based on flyback transformer can prevent the battery charge or discharge Excessively and improve the battery’s working efficiency obviously when combine the specific equalization criterion.Software and hardware was designed HRT14YL01 boarf was choosen as the BMS’s main control module. The module was responsed to the battery pack’s total voltage and total current measurement, estimated the battary SOC and communicated between modules by CAN. Distributed board module was designed to meaure battery pack’s temperature, battery cell’s voltage and do the balance control between battery cells. The Distributed board module’s software.