Study On HESS Energy Management Strategy Of Electric Vehicle Based On GA

The traditional electric vehicle uses a single battery as an energy storage device,and it is difficult to satisfy the energy and power requirements of the electric vehicle under different working conditions at the same time.In this paper,a hybrid energy storage system(HESS)composed of a lithium-ion battery and a supercapacitor is designed,and an optimal allocation strategy for the energy power of a hybrid energy storage system based on a genetic algorithm(GA)is proposed.Classify and manage the different working modes of the energy storage system,and establish the objective function with the smallest error between the output power and demand power of the energy management system.A genetic algorithm is used to solve the objective function to obtain the output coefficients of the lithium-ion battery and the super capacitor,thereby optimizing the power distribution and improving the overall performance of the energy storage of the electric vehicle.Firstly,the current status of research on the energy management of the hybrid energy storage system for electric vehicles at home and abroad,and the difficulties in energy management are analyzed.Then the solution to improve the composition and control methods of the energy storage unit is proposed.On the basis of comparing the topologies of several energy storage systems,the lithium-ion battery and the supercapacitor were individually controlled and then connected in parallel.This structure can give full play to the respective performance advantages of lithium-ion batteries and super-capacitors.Then the working principle of the bidirectional DC/DC converter and its application in the hybrid energy storage system are analyzed,and the soft-switching technology is used to reduce the energy transfer loss of the bidirectional DC/DC converter.It was analyzed that the working principle,charge-discharge characteristics and internal resistance characteristics of lithium-ion batteries and supercapacitor.An appropriate equivalent model was established based on the characteristics of lithium-ion batteries and super capacitors.On this basis,the extended Kalman algorithm and the open circuit voltage method were used respectively.Estimate the SOC of lithium ion battery and super capacitor.Consider the energy ratio of lithium ion battery and super capacitor in the hybrid energy storage system,determine their respective SOC weight coefficients,and weight the overall SOC value of the system.The process of implementing the HESS energy management strategy was proposed.Subsequently,the relational expression of the car's driving speed and power demand was derived,and based on the SOC of each energy storage unit,the objective function between the power demand of the electric vehicle and the output power of each energy storage unit of the HESS was established and improved.The GA solves this objective function and obtains the output coefficient of each energy storage unit,and then proposes a control strategy that takes into account both power allocation and energy scheduling,and optimizes the power distribution of lithium ion batteries and super capacitors.Finally,an electric vehicle structure with HESS is built on ADVISOR platform.The urban road cycling condition in America and the city driving cycling condition in Europe are chosen for simulation respectively.The particle swarm algorithm and the optimized GA are utilized for the comparative simulation.The simulation results are analyzed to verify the feasibility of the GA-based HESS energy management strategy.Then simulation experiments were conducted on the present laboratory platform to verify that the proposed energy management strategy can coordinate the output power allocation of lithium battery and the super capacitor.It has practical application value.