Research On Energy Management Strategy Of Hybrid Energy Storage Systems And HIL Test For Electric Vehicles

Electric car has been one of the most important parts to develop the low-carbon society transportation system due to its advantage of energy conservation and environmental protection.And power battery as the main energy storage unit of the electric car,its performance will directly have great influence on the electric car energy efficiency.For the present power battery,including lithium ion battery remains low power density,short life cycle and poor environmental adaptability.So,the vehicle depends on power battery alone will have many problems,such as short driving distance,long charging time and poor startup performance at low temperature.In recent years,super-capacitor,a new energy storage system,provides a new solution to overcome the shortage of power battery.Super-capacitor has high power density,long cycle life and strong adaptability to environment,but its energy density is very low.So it can't be used to drive electric vehicle alone.The hybrid power system combined power battery with super-capacitor will have the both advantage of them,and it has huge practical significance.Power allocation is the key technology of hybrid power energy management system,and the power demand is the important basis of power distribution.Due to the complexity and dynamics of urban traffic environment,the power demand of power system often contains all kinds of peak and the high frequency components,the traditional power allocation method based on single fuzzy logic controller or high and low pass filter can't decompose the different components of power demand efficiently.So it can't satisfy the dynamic characteristics of power battery and super-capacitor.In order to overcome this problem,a novel power allocation method called adaptive wavelet control is proposed in this paper,the method is divided into two layers: first layer using the wavelet transform algorithm decomposes the power demand of system into two parts: high frequency component and low frequency component;second layer using a fuzzy logic controller adjusts the layer number of wavelet decomposition reasonably according to the energy condition of power system.Then assign the high frequency and high amplitude component to super-capacitor and assign the low frequency and low amplitude component to power battery.This method can allocate the power demand according to the dynamic characteristics of power battery and super-capacitor;balance the energy condition of battery and super-capacitor efficiently at the same time.Compared with the traditional methods,it could greatly improve the performance of the power system.In this paper,the main works include the following things:Firstly,analyze the dynamic characteristics of hybrid power system.Accomplish the test of battery and super capacitor respectively based on standard test conditions.For the battery,including constant current charge and discharge characteristics test,resistance test,the variable power characteristic test;and for super-capacitor,including characteristics of constant current charge and discharge test,resistance test.Then the voltage characteristic curve of power battery and super-capacitor were completed.Finally,build the efficiency model of the bidirectional DC/DC and the equivalent circuit models of power battery and super-capacitor,and achieved the verification of the models based on the test data.Secondly,propose a novel allocation method,this method is divided into two layers: first layer using the wavelet transform algorithm decomposes the power demand of system into two parts: high frequency component and low frequency component;second layer using a fuzzy logic controller adjusts the layer number of wavelet decomposition reasonably according to the energy condition of power system.Then assign the high frequency and high amplitude component to super-capacitor and the low frequency and low amplitude component to power battery.Compared with the traditional methods,this method can allocate the power demand according to the dynamic characteristics of power battery and super-capacitor;balance the energy condition of battery and super-capacitor efficiently at the same time,improve the performance of the power system greatly.Thirdly,the construction of the hybrid power experimental platform for the real vehicle power grade was carried on.The platform used the dSPACE Auto-box as the controller for running the algorithm,used the AVL battery simulation equipment as the load power,used the lithium battery of Zhejiang Wanhaowanjia as the main power supply,chose the Maxwell super-capacitor produced by Liaoning Baina as auxiliary power supply,chose bi-directional DC/DC converter produced by Beijing Haoruichang as the energy storage cell voltage transformation equipment.Finally,based on the platform of the hybrid,finished the experimental study and verification of hybrid power system advantage.