Research On State Of Charge-aware Pulse Preheating Strategy Of Lithium-ion Battery At Low Temperatures

Lithium-ion batteries are widely used in electric vehicles due to their high specific capacity,long life,and environmental friendliness.However,the impedance of lithium-ion batteries increases sharply in low temperature environments,and the performance and capacity loss is significant.Preheating the battery before use is an effective method to recover its performance quickly.This paper proposes a low temperature pulse preheating strategy for lithium-ion batteries based on state of charge-aware to solve the problems of the inaccurate state of charge estimation,long heating time,and high power consumption existing in the existing internal preheating strategies.The contents are as follows:Firstly,an extended Kalman filter state of charge estimation method based on temperature compensation is proposed to solve the problem that it is difficult to accurately estimate the actual usable state of charge of lithiumion batteries at low temperatures.The electro-thermal coupling model of the battery is analyzed and established.And the parameters of the coupling model are identified based on the experimental data of the hybrid pulse power characteristic tests.In order to accurately estimate the state of charge of the battery under low temperature conditions and provide essential chargedischarge control information for the subsequent preheating strategy,the state space equation of the battery is constructed,and the extended Kalman filter is used to estimate the state of charge of the battery to eliminate the influence of measurement noise and process noise on the estimation results.At the same time,in order to eliminate the estimation error caused by the temperature,a compensation factor is added to the estimation process to correct the result,and the accurate estimation of the state of charge of the lithium-ion battery under low temperature conditions is realized.Secondly,an optimal pulse preheating strategy based on the genetic algorithm and fuzzy logic control is proposed to solve the problems of long heating time and high power consumption of lithium-ion batteries at low temperatures.In order to consider the change of battery state during the preheating process,an online pulse preheating strategy based on fuzzy logic control is designed.According to the battery temperature and the accurately estimated state of charge,the pulse current is adjusted in real-time to ensure the heating effect.In order to further shorten the heating time and power consumption,with the goal of minimizing the heating time and power consumption,the fuzzy logic control rules are optimized by using the genetic algorithm,and the optimal pulse preheating strategy is obtained,which realizes fast and energy-saving preheating of lithium-ion battery under low temperature conditions.Finally,the accuracy of the proposed state of charge estimation method is verified by simulations under constant temperature and variable temperature conditions,an experimental platform for low-temperature preheating of lithium-ion batteries is built and the effectiveness of the proposed pulse preheating strategy is verified.