| The extended-range electric vehicle can effectively overcome the ‘mileage anxiety’ problem of the current pure electric vehicle during the travel process because of the range extender.At the same time,the complicated and varied city bus operation conditions are used to enhance the advantages and increase the efficiency of the extended-range electric bus.This dissertation focuses on an extended-range electric city bus,focusing on the matching of its power system,the matching and control of hybrid energy storage devices,the energy conversion efficiency of the range extender,and the economic analysis of the vehicle:Based on the analysis of the characteristics of the extended program structure,the mathematical model of the power system of the extended-range electric bus is established.The theoretical analysis of the vehicle dynamics,drive motor,energy storage device and range extender is carried out,which lays a foundation for the matching of the power system.And the characteristics of rectangular wave permanent magnet synchronous motor,sine wave permanent magnet synchronous motor and permanent magnet reluctance motor in high efficiency permanent magnet synchronous motor are discussed.The type of motor is determined according to the different working characteristics of the drive motor and the generator of Range extender.According to the power,economy and pure electric driving range indicators proposed by the Ministry of Transport on the technical requirements of city buses and hybrid buses,and the dynamic requirements required for vehicles to travel at typical Chinese city bus cycle speeds,The matching of the powertrain structure and subsystem parameters of the extended-range electric bus was carried out.According to the operating characteristics of city bus,the pure electric driving mileage index based on the actual bus line circulation distance is proposed.The "power-to-energy ratio" in the parameter matching of the extended-range electric bus energy storage device is analyzed,and the necessity and rationality of using the hybrid energy storage for the vehicle type are pointed out.The influence of some parameter changes on the dynamics and economy of the whole vehicle is analyzed.The parameters are optimized by the linearity-weighted optimization method with the aim of economy.Vehicle demand power fluctuates frequently under city conditions,while the capacity of the energy storage device carried by the extended-range electric bus is small,resulting in its power not meeting the requirements of vehicle acceleration and braking energy recovery.In order to solve this problem,this dissertation chooses the hybrid energy storage device composed of electric double layer ultra-capacitor and NCM-lithium battery as the energy storage component of the extended-range electric bus.A method for parameter matching of hybrid energy storage devices is proposed,and the matching is optimized by constraint condition method,linearity-weighted method and genetic algorithm method.In the energy management of hybrid energy storage devices,control strategies based on rules,fuzzy control and genetic algorithm optimization are used to compare and analyze the energy storage device control strategy.The control strategy of the extended-range electric bus’ s range extender is analyzed,and the MATLAB/Simulink simulation model is built.Under the typical city bus cycle conditions in China,the control of the fixed-point power generation,the power following along the maximum efficiency curve and the constant speed power following are analyzed.The effect of the strategy,in which the vehicle’s equivalent fuel consumption is the smallest under the fixed-point power generation control strategy.In order to improve the energy conversion efficiency of the range extender,compare and analyze various types of engine characteristics,and utilize the advantages of Miller cycle engine and Homogeneous Charge Compression Ignition(HCCI)to integrate the Miller cycle HCCI engine used as an engine for the range extender.The feasibility of the engine was analyzed by GT-power simulation software,and the comparison simulation of various types of engines was carried out.The results show that the Miller cycle HCCI engine has higher efficiency than other types of engines,which can effectively improve the energy conversion efficiency of the range extender.Through the optimization of vehicle control strategy and power system structure,the power structure layout scheme of parallel double-stroke is proposed,which can realize two extended-range modes of single-stroke operation and simultaneous operation of dual-stroke.At the same time,based on the traditional controller control strategy,a CD-Blended-CS control strategy is proposed.The strategy can be matched with the dual-stroke structure to further improve the energy efficiency of the vehicle.Through AVL_CRUISE and MATLAB/Simulink,the simulation model of the extended-power electric bus power system was built,and the power,economy and pure electric driving range of the designed power system were simulated and verified. |
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