Research On The Optimized Control Strategy For The Synergic Electric Power System On HEV

Energy crisis, environmental pollution caused a worldwide revolution in the automotive power systems. In order to protect the natural environment, conserve the non-renewable energy sources, improve the energy structure, developing new energy vehicles is imperative. Under the research climax of the EV and HEV, the global automotive industry is moving towards "energy saving, emission reduction" of the era. In view of the current development status of vehicle power energy storage device, the EV's practical application still has a long way to go, In a future time, the hybrid power will be an important alternative way to substitute the pure fuel power, no matter which program wins, the power source system of vehicle is very essential, whether HEV or EV, which all require an advanced, compact, high energy density electric energy storage systems to provide big energy and high power, and the present, the characteristics of batteries and ultracapacitors are unable alone to satisfy those requirements under the economy conditions; And then we consider using high power density ultracapacitor and great energy battery combined, Through rational combination of structure and energy management strategies, to play two different characteristics of the complex energy storage devices, to break through the single storage device's technological bottlenecks, so it can reduce costs, improve the performance of the automotive energy system, which is the starting point of this paper.This paper firstly analyzed the performance and characteristics of current dynamic energy storage devices who are widely used, according to the specific energy, power density and high ratio current fast charge and discharge characteristics, analyzed and compared the performance of their respective advantages and disadvantages, combined with the special requirements of automotive power and economy, chosen lithium battery and ultracapacitor for energy components. The discharge and capacity's characteristics of lithium battery as well as the ultracapacitor's properties of charge and discharge, resistance are analyzed in detail. On this basis, Discussed three kinds of typical Complex power structure and the properties of the compound power system, Selected the Vehicle complex power structure using ultracapacitors and DC/DC in series and parallel with the lithium battery; two working state who are charge and discharge are generalized from a deep research on four working mode of the compound power system. Then the power distribution model of the composite power system was analyzed, in order to ascertain the power distribution factor and the physical constraints of the composite power system; the power distribution factor which is as a control object, energy management strategy of complex power system is established which based on fuzzy logic, due to the control of discharge and charge state's emphasis are different, designed two fuzzy logic controllers for the discharge and charge state. Two fuzzy logic controllers and the model of complex power system are completed, then simulated in the ADVISOR, the simulation results of fuzzy logic control strategy are analyzed.Based on the analysis and research previously, combining global optimization thought, the membership function's parameters of the power distribution factor act optimized object, the optimization mathematical model of energy management is established, using the fuel consumption ratio of the vehicle and Regenerative braking energy recovery ratio as optimal target function of composite power system. Then the target function of the composite power system's energy management of the whole optimization mathematical model are used as evaluation index, constraint conditions made using of the power distribution factor's fuzzy subsets division, the energy storage devices' SOC state, power and energy limited, the genetic algorithm toolbox with the ADVISOR are used for solving the optimization model of power allocation factor, and completed parameters optimization of membership function who are the power distributor's.Simulation results show that Optimized fuzzy energy management strategy can more effectively reduce the large current impact on lithium batteries, and improve the regenerative braking energy recovery ratio, while reducing the fuel consumption ratio of hybrid electrical vehicles, extending the life of lithium battery, compared with fuzzy energy management strategy who is Not optimized.