Research On Energy Management Strategy For Hybrid Electric Vehicles With Multi-Energy Sources

Hybrid Electric Vehicles(HEV)are one of the main directions in automotive industry.However,lithium ion batteries have issues such as energy density and power density being unable to balance,and short cycle life.As a new type of energy storage device,supercapacitors have the advantages of high-power density and fast charge and discharge rates.Therefore,supercapacitors are introduced into HEV as auxiliary energy storage devices to form a composite power supply with lithium batteries.The composite power can satisfy the dual requirements of energy and power usage.This dissertation focuses on the research of power distribution and regenerative braking energy management in the HEV with a composite power source,which is divided into three parts as follows:(1)In order to establish a hybrid power source HEV simulation model,the power structure of the HEV with the composite power source is firstly determined.Secondly,determine the energy storge structure of the hybrid power HEV.Then,the parameters of the composite power source are determined according to the energy and power requirements under typical cycling conditions.Finally,the simulation model of the whole vehicle of the HEV with the composite power source is established.(2)In order to solve the problem of poor adaptability of energy management strategies to driving conditions,a hierarchical energy management strategy based on driving cycle and driver style recognition is proposed.The strategy is divided into highlevel engine and low-level hybrid power energy management.In the engine energy management strategy,the introduction of condition recognition technology is used to reasonably allocate the required power of the engine and composite power supply,in order to ensure the engine operate at the optimal condition and improve the energy utilization efficiency.In the hybrid power energy management strategy,a fuzzy controller is designed based on driver style and hybrid power information to adjust the low-pass filter coefficient.And to reduce the current impact on the lithium-ion battery and its aging.(3)A multi-objective decision-making method based on variable weight sensitivity ratio is proposed to coordinate the stability and economy of the regenerative braking process.Firstly,the grid method is used to obtain the multi-objective solution of the front and rear wheel braking force allocation coefficients under each braking intensity,and the Pareto solution set is obtained through non-dominated sorting.Then,the nonlinear variable weighting sensitivity ratio decision-making method is used offline to obtain the braking force allocation coefficients with the best coordination under each braking intensity.Finally,a one-dimensional mapping table of braking intensity and braking force allocation coefficients is established and embedded into the braking energy recovery strategy to coordinate the stability and economy of the vehicle braking.