Research On Battery State Of Charge Estimation And Balancing Technology For Micro-nano Satellite

Lithium batteries have the advantages of high energy density,large charge and discharge current,long cycle life,and low price.They have now become the first choice for Micro-nano Satellite energy storage batteries.However,due to the non-linearity,temperature sensitivity,and inconsistency of lithium batteries,it is more likely to experience overcharge,overdischarge and rapid performance degradation during operation in harsh space environments.Therefore,it has important application value to ensure the performance and safety of lithium batteries in orbit operation through accurate state-of-charge(SOC)estimation and reliable battery balance.The main work of this paper is as follows:First,a SOC estimation algorithm based on modified parameter unscented Kalman filter(MPUKF)is proposed.The algorithm corrects the battery capacity according to the temperature and the number of cycles of the lithium battery,uses the recursive least squares method with the forgetting factor to identify the remaining parameters of the model online,and uses the corrected capacity and identification results for the next unscented Kalman filter iteration Process to ensure the accuracy of SOC estimation.The simulation results show that the MPUKF algorithm designed in this paper is better than the UKF algorithm in terms of convergence and accuracy.Second,a scheme is designed to use solar battery charge balance in the illuminated area and discharge balance in the shaded area.The balance circuit of this scheme is based on a switch array,with an analog switch as the control core,with simple structure and control and high reliability.On the basis of the equalization circuit,with SOC as the equalization variable,an equalization strategy combining threshold control and extreme value selection is proposed.At the same time,a MPPT circuit is designed to increase the charge equalization current.The simulation results show that the proposed balancing scheme has fewer switching times,and the SOC difference of the single cells after balancing is less than 0.5%.Third,developed a prototype of the lithium battery management system.First,the hardware circuit and software of the system were designed,and then a test platform was built to test the principle prototype.The test results show that the developed prototype has high sampling accuracy and small SOC estimation error.The equalization circuit can achieve rapid equalization of lithium battery packs in the illuminated area,and battery temperature control in equalization in the shadow area.