Research On Energy Management Strategy Of All Electric Ship Based On Lithium Battery Cycle Life

All electric ships have become the main trend of the development of new energy ships.However,due to the reduced cycle life of lithium battery packs that cannot meet the actual sailing needs of ships,the battery packs need to be replaced frequently,which limits the popularization and application of all electric ships.Therefore,improving the cycle life of lithium battery pack has become a hot research field.In this thesis,taking the experimental platform of all electric intelligent ship as the research object,the lithium battery aging problem is studied to improve the cycle life of lithium battery.The logic gate restriction algorithm is used to formulate the energy management strategy.With the help of MATLAB / Simulink software platform,the energy management system of ship power battery is developed and verified on the all electric intelligent ship.The results show that compared with the traditional discharge control strategy of the original ship,the aging rate of the battery pack of the whole ship control strategy is significantly reduced,and the average aging severity factor of the energy management strategy is lower than that of the traditional charge and discharge management system.The main contents of this thesis are as follows.(1)The aging severity factor model of Li Fe PO4 power battery pack was studied.Firstly,the working principle of Li Fe PO4 power battery and the influencing factors of its cycle life were analyzed,and the electrochemical performance experiments were carried out under different working conditions to study its cycle performance.Secondly,according to the experimental data,the prediction model of cell cycle life is established by using nonlinear least square parameter identification.On this basis,combined with the aging principle of battery pack,the cycle life of battery pack is predicted by using this model.Compared with the prediction model constructed by John et al,the accuracy of this model can be improved by 8.83%.Finally,according to the cycle life prediction model of battery pack,the aging severity factor model of battery pack is established.(2)Research and construction of energy management strategy.Firstly,in order to extend the cycle life of battery pack,the power and current models to meet the speed requirements of all electric ships are established under typical sailing conditions,and the energy management strategy of all electric ships is studied and constructed.Then,under the condition that the remaining capacity of the battery meets the voyage mileage,the integral of the severity factor model is used to represent the actual discharge aging effect of the battery,and the relationship between the charge sustainability,the discharge depth and the ship speed of the battery and the power and current of the battery is taken as the constraint conditions,and the nonlinear programming algorithm is used to optimize the minimization of battery aging,As the condition of battery pack switching and output power,the logic threshold algorithm is used to extend the cycle life of battery pack(3)Modeling and experiment of energy management system for all electric ships based on lithium battery cycle life.According to the research results,the simulation models of electric propulsion system and energy management system are built by using Matlab / Simulink.Finally,1514 cycles of charge and discharge tests were carried out in the simulation model,and compared with the traditional discharge management system,the results show that the proposed energy management strategy can reduce the capacity attenuation of lithium battery pack.(4)The control strategy is tested on board.In Xiamen Sino Australia Yacht Club,the all electric ships energy management and control strategy based on battery cycle life is tested on a real ship,and the influence of energy management strategy on Li Fe PO4 battery cycle life is analyzed.The feasibility of using the energy management system based on lithium battery cycle life in the all electric ships system is preliminarily verified,which provides help for the in-depth study of the optimization and intelligent control of the energy management system in the all electric ships.