Research On Energy Management And Nonlinear Control Strategy Of Hybrid Energy Storage System For Electric Vehicle

Considering the randomness and fluctuation of load power of electric vehicles during the driving process,a new hybrid energy storage system is proposed,which is composed of supercapacitor with high power density,long cycle charging and discharging life,fast response speed and battery with high energy density,but not easily charged and discharged frequently.The energy storage characteristics of the two energy sources are brought into full play to realize their complementary advantages and make up the shortcomings for the traditional single energy storage system.In this paper,the energy management of hybrid energy storage system and the non-linear control strategies of interface circuit for electric vehicles are studied.In order to realize the reasonable distribution of load power between battery and supercapacitor,the energy management strategy(EMS)of the energy storage system of electric vehicle is studied.For protecting the battery,improve its service life and reduce the fluctuation of battery charging and discharging power,when dealing with frequent and violent fluctuation of load power,the supercapacitor provides the high frequency component of load power fluctuation,which makes the battery provide the low frequency component of load power fluctuation.In this paper,6 kinds typical vehicle driving conditions commonly used in the world are selected.Three power allocation strategies:low-pass filtering,moving average filtering and wavelet decomposition method are used to decompose the load power required for electric vehicles under different driving conditions.The spectrum of the decomposed battery power is analyzed,and the decomposition effect under the three power allocation strategies is compared.The non-linear control strategy of interface circuit of electric vehicle energy storage system is studied.For the active control hybrid energy storage system composed of two bidirectional DC-DC converters,which parallel the battery and supercapacitor energy storage to the DC bus,the global mathematical model of the whole hybrid energy storage system is established firstly.On this basis,the target controller is designed:a current controller based on synergetic control theory is designed to track the battery current and supercapacitor current.The voltage controller based on Lyapunov function is designed to realize the stable control of DC bus voltage.Two typical vehicle cycle driving conditions IM240 and ECE-15 are selected to simulate the effectiveness of the current controller and the voltage controller on the Matlab/Simulink software platform.The simulation results show that non-linear controllers have strong robustness and good adaptability to different driving conditions.The experimental platform of a small-capacity hybrid energy storage system is built,and the relevant experimental verification of the nonlinear control strategy is carried out under this platform.The experimental results are consistent with the simulation results,indicating that the current controller based on synergetic control and the voltage controller based on Lyapunov function have practical feasibility.