| Li-ion battery pack is often used as the power source of autonomous underwater vehicle(AUV),because of its high energy density,long cycle life,low pollution and resistance to overcharge and overdischarge,etc.It is often integrated into battery packs by series-parallel connection to provide power for large equipment,and is also often used as the power source of autonomous underwater vehicle(AUV).The long-term high temperature operation of the battery will affect the performance of the battery,affect the efficiency of the AUV,and even cause damage to the equipment,so the effective control of the temperature of the power battery pack has an important role in the actual use of the AUV.In this paper,we take 18650 type lithium-ion battery as an example,analyze its internal reaction,heat production and heat exchange performance,and establish the electrochemical-thermal coupling model of single cell battery by using COMSOL software,coupling the heat generated by the onedimensional electrochemical model during operation as a heat source in the three-dimensional model,exploring the temperature change and distribution of the battery during discharge,analyzing the effect of different discharge rates,The effect of different discharge rates,operating temperatures on the rate of temperature change and temperature difference of the battery.Then the single cells are arranged and combined in groups to form a battery pack available for AUV.Since the battery pack described in this thesis uses liquid cooling cycle for cooling during operation,the convective heat transfer coefficient is used to simulate the heat transfer between the outer wall of the battery pack and the cooling liquid,and then COMSOL is used for finite element modeling.Through comparative analysis,the temperature change and distribution of closely arranged battery pack and decentralized parallel battery pack under the same discharge current condition are derived,and through comparison,the design scheme of decentralized parallel battery pack is proposed.Finally,to address the problems of large computation and time consuming of the finite element model,a temperature field model based on the intrinsic orthogonal decomposition method is proposed,and its order is reduced by the Galerkin projection method,so as to obtain a reduced-order temperature computation model,based on which,combining the basic ideas of dynamic planning and iterative dynamic planning,a decentralized parallel battery pack with coolant flow rate as the control variable and battery temperature The temperature control scheme of distributed parallel battery pack with coolant flow as the control variable and cell temperature as the state variable is proposed.The proposed temperature control scheme is validated by establishing a joint MATLAB-COMSOL simulation system. |
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