Research On EV-HESS Energy Control Strategy Considering Battery Internal Resistance Loss

Lithium-ion batteries are the main energy storage components of electric vehicles.Due to the limitation of their internal energy storage structure,the power adaptability is poor when the electric vehicle is frequently accelerated and braked at high power.Super capacitors have the advantages of fast charge and discharge speed,high power density,and long cycle life.Taking into account the load characteristics of electric vehicles,this paper combines a super capacitor and a lithium-ion battery in parallel to form a hybrid energy storage system.The power characteristics of the super capacitor are used to make up for the short-term power performance of the lithium-ion battery.Electric vehicle hybrid energy storage system.Research and design efficient and optimized energy control strategies,so that hybrid energy storage systems can not only meet the power needs of electric vehicles,but also reduce the power loss of lithium-ion batteries.Firstly,in order to make full use of the respective working advantages of lithium-ion batteries and supercapacitors,they are tested and analyzed for their characteristics.The open-circuit voltage characteristics and discharge of lithium-ion batteries and supercapacitors are respectively measured under different cycle times,SOC cycle intervals and discharge rates.Test the internal resistance and capacity characteristics.At the same time,in order to facilitate the calculation of battery internal resistance loss later,the test method of battery internal resistance was studied and an internal resistance test method suitable for the research requirements of this paper was selected.Secondly,according to the test results of the operating characteristics of lithium-ion batteries and supercapacitors,the modeling and parameter identification of lithium-ion batteries and supercapacitors are carried out through Matlab / simulink simulation software.The design and calculation of the parameters of its components are convenient for further calculation and analysis of the voltage and current simulation results later.In order to provide a smooth power supply for lithium-ion batteries,the principle of DC / DC converters required for parallel connection was analyzed,and a suitable hybrid energy storage system topology was selected.Thirdly,according to the mathematical model of the hybrid energy storage system,the energy control process is analyzed,and a fuzzy PID energy control strategy is designed.An optimal control scheme considering the internal resistance loss of the battery is proposed in the control strategy without considering the loss caused by battery aging.Based on the relationship between battery internal resistance loss and driving power,the required power and current are decomposed,and fuzzy rules in 9 modes are formulated.Based on the threshold parameters of SOC and required power,a fuzzy PID optimized energy control strategy is designed.The feasibility of this strategy is analyzed.Finally,the fuzzy PID optimized energy control strategy is simulated and verified in ADVISOR software.In order to further verify the efficiency of the strategy,compared with the traditional fuzzy PID controlled hybrid energy storage system,the peak current,SOC change and battery internal resistance loss are compared respectively.The analysis shows that the proposed control strategy can effectively reduce the peak current of the lithium-ion battery and increase the utilization rate of the super capacitor,thereby reducing the loss caused by the internal resistance of the battery,improving the energy utilization rate,and ensuring the efficient and stable operation of the hybrid energy storage system.