Research On Design And Power Split Strategies Of Hybrid Energy Storage System In Vehicle

In recent years, the electrical energy storage systems for hybrid and electric vehicles are mainly comprised of batteries. Because that the banks of batteries are suffered from highpower shock frequently for the accelerating and breaking, the cycle life and the efficiency of the battery banks are reduced. So researchers propose that using different energy storage components with high specific power and high specific energy together as the hybrid energy storage systems(HESSs) to satisfy the demands of both power and capacity. This thesis studies on the parameter matching and power distribution strategy of the active parallel battery-ultracapacitor HESS, and proposes a new structure and power distribution strategy based on the active parallel HESS.Firstly, this thesis studies on the characteristics of the main components of HESS. The battery testing platform is set up. The parameters of the Li-ion battery equivalent circuit model are identified based on the HPPC experimental data. Based on Matlab/Simulink, the models of battery and ultracapacitor are established. The working principles of bidirectional dc/dc converter are described also.The optimization of parameter matching of HESS is proposed. Aiming at the vehicle with electro-mechanical transmission under military driving conditions, the mass, volume, loss, capacity and the average charge-discharge rate of the batteries are used as the optimal goals, the parallel number of battery cells and power limit of the battery bank are used as the optimal variables, the parameters of the active parallel HESS are optimized. The HESS model is built based on Matlab/Simulink.This thesis studies the power distribution strategy of active parallel HESS. Two power distribution strategies are proposed: logic threshold strategy and fuzzy logic strategy with stochastic prediction. The effectiveness of the two strategies is validated based on the Matlab/Simulink model. The experimental platform of active parallel HESS is set up to validate the feasibilities of the two strategies.To decrease the peak power of the bidirectional dc/dc converter in HESS, a new HESS structure and its control strategy are proposed in this thesis. On the basis of active parallel structure of HESS, two switches with parallel diodes are added. Different modes are adopted for different load power levels to reduce the peak power of the bi-directional dc/dc converter. The new HESS structure has three modes, and each mode has a strategy to distribute electrical power and switch modes. Both of the simulating model and experimental platform are built, and the feasibility and effectiveness are validated.