Research On Algorithm Of Estimation Of Soc For Mh-ni Batteries Used On Hev

SOC of batteries used in HEV is the important data of battery management system.SOC of batteries used in HEV require to be estimated real-time, on-line, accurately. This is the premise of energy control strategy of HEV too, the guarantee which prevent batteries damage from overcharging or over-discharging. Battery Group of HEV has its own characteristics when they work:large interval of the temperature, the interval of temperature can reach 60 degrees Celsius; charge and discharge frequently and the large variation of current. However, many estimation algorithm of SOC which people often used in HEV does not take into account a lot or as a constant when they deal with temperature factor; In addition, the relationship between SOC and the terminal voltage of batteries is non-linear, but many algorithms deal with them directly as a linear relationship, resulting in large estimation error of SOC.This article describes the development trend of automobile and the key technology which should be resolved in hybrid electric vehicle, working mechanism of MH-Ni battery, study of the factors which affect the estimate of SOC and battery model used presently, the SOC algorithm which base on Extended Kalman algorithm, the implementation of the SOC estimation and the resulu of test.This is the three key factors for estimating SOC real-time, on-line, accurately:the establishment of a suitable cell model; SOC estimation algorithm; the design of battery management system. According the analysis to predecessor's research result, the paper mainly does three aspects things. First, the establishment of improved RC battery model, an improved RC battery model focus on taking into account the impact of temperature to the SOC, to model the battery model in this article is based on the experimental method, so many experiment have been designed and many data have been attended before the model of battery is established; Second, Extended Kalman filter algorithm is used to estimate the SOC, using Taylor series expansion method to battery state equations for linear processing; third,design the battery's hardware and software systems, The part of sampling the battery voltage is designed used the bus structure which not only simplifies the circuit and also enhance the reliability of the circuit.Experimental results have showed that the accuracy may meet the requirements of HEV and the accuracy can be improved by using the improved battery model which based on Extended Kalman algorithm to estimate the battery SOC, the temperature characteristics is clearly superior to the traditional, the temperature change has a good adaptability.