The Research Of DSP-Based Battery Signal Monitoring And SOC Estimation For HEV

Power battery is the main energy source of HEV, and its quality directly affects the merits of the vehicle performance, in many power batteries, lithium battery has been widely regarded as a battery type with high development potential because of its high specific energy and high discharge rate. As the voltage of lithium battery is low, it is always in hundreds of series, so a battery management system is needed to eliminate the security risks and make sure that all the battery is working stably, efficiently, and safely. Battery management system can monitor the signal of every battery and manage the battery rationally, so it can increase the performance of battery and increase battery's life.SOC is an important parameter to describe the remain energy, SOC can provide a reference when BMS control the charge and discharge of battery and it's also a important parameter for energy manage strategy, so the accuracy of SOC estimation will directly influence the using time and cost of the battery. But because of the complex electrochemical reaction inside the battery and nonlinearity of batteries, it is difficult to test accurately, it has become a bottleneck restricting the development of electric vehicles. Therefore, the study of the PHEV battery SOC estimation is essential for the development of HEV. In this paper, SOC estimation of PHEV is researched, and the main contents are described as follows:Firstly, this paper gives the development backgrounds and classification of HEV and the improve situation and characteristics of HEV. Then the key technologies of BMS and the main methods, present problem, improvement of SOC estimation are analyzed emphatically.Battery signal monitoring module of battery manage system was designed based on TMS320F2812. Voltage, current and temperature signals of single battery can be detected by the monitoring module. The hardware and software design of the module was introduced in the paper, and then verified the accuracy of the detection devices by experiment. After analysising the shortcoming of the traditional SOC estimation method and the exsisting method, the method based on ampere-hour method and kalman method was researched. Ampere-hour method was been used to estimate the SOC of battery as the accurate value at first, and then Thevenin model and RC model was applied for the KF to estimate the SOC. Finally, a constant current discharge and pulse discharge experiment was done, and compare the result of KF based on different modle with the result of ampere-hour, the experiments show that the KF can overcome the accumulated error of AH and the KF based on RC can achieve higher accuracy.