| With the development of battery technology,the energy density of power battery is greatly improved.The accompanying problem is that the calorific value of battery increases and the temperature rises rapidly,which leads to the reduction of capacity and cycle life of power battery.Therefore,an effective battery thermal management system for electric vehicles is established to ensure that the power battery works in a suitable temperature range,so as to improve the performance of the power battery and the safety of electric vehicles.Based on the analysis of the electrothermal characteristics of lithium-ion batteries for electric vehicles,the thermal model and optimization strategy of the battery liquid cooling system are studied in this paper.The main research work of this paper is as followsFirst,the current situation of thermal model and cooling technology of lithium-ion battery at home and abroad was described.The lumped thermal model of lithium-ion battery was established,in which the change of internal resistance of lithium-ion battery with temperature and the change of heat transfer coefficient with coolant flow rate were considered.Based on AMESim(Advanced Modeling Environment for Performing Simulation of Engineering Systems),the liquid cooling system model of power battery was established,and the heat transfer relationship of each battery in the battery pack was studied.Then,according to the law of conservation of energy,the lumped thermal model of lithium-ion battery pack was established.At the same time,based on the hybrid pulse power characteristic(HPPC)experiment,the internal resistance and other parameters in the thermal model of lithium-ion battery are obtained,and the accuracy of the lumped thermal model of lithium-ion battery is verified.According to the control requirements,a power battery liquid cooling system model including power battery,electronic water pump and plate heat exchanger is established.Then,according to the characteristics of nonlinear model and time-varying parameters of the liquid cooling system,and the chattering problem in the sliding mode control strategy,the fuzzy sliding mode optimization strategy of the power battery cooling system is proposed by using the integral sliding mode surface.The reaching law of the sliding mode control is adjusted by the fuzzy logic method,so that the power battery cooling system has strong robustness,At the same time,the stability of the power battery cooling system is ensured.Finally,based on MATLAB platform,a fuzzy sliding mode controller is built.On AMESim platform,the liquid cooling system model of lithium-ion battery pack was built.Matlab-AMESim co-simulation is carried out.The effectiveness of the fuzzy sliding mode optimization strategy proposed in this paper is verified under constant current,NEDC(New Europe Driving Cycle)and US06(United States 06)conditions.Compared with PID(Proportional Integral Differential)method,the simulation results show that the fuzzy sliding mode optimization strategy ensures that the temperature of the battery pack is within the optimal target temperature range.The rapidity and stability of the cooling process is enhanced.The inconsistency of the battery pack temperature is reduced.The energy consumption of the liquid cooling system is also reduced. |
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