Simulation Research On Hybrid Electric Vehicle Energy Management Control Strategy Based On New Power System

Low engine efficiency is a limitation of improving hybrid vehicle efficiency.To solve this problem,this thesis doesn't take Atkinson cycle engine technology route,but another way,proposing a method that using hydrogen fuel characteristic to improve engine efficiency.By using on-board hydrogen production system,hydrogen direct injection system,lean-burn gasoline engine with local hydrogenous mixture,and combining the existing hybrid vehicle technology,which form an advanced,efficient and clean new vehicle power system.The whole system can provides the characters of higher compression ratio and leaner fuel mixture,which can be used to get fast combustion,and avoid engine misfire.What's more,during the heavy load work condition,the quality adjustment is used to reduce mechanical loss of the engine.The elements mentioned above brings gasoline engine with a higher efficiency.While improving the efficiency of engine,at the same time,research on integrated control strategy of on-board hydrogen production system and lean-burn gasoline engine with local hydrogenous mixture is studied.The on-board hydrogen production can avoid the current troubles,such as hydrogen storage and transportation.The electric power supply for on-board hydrogen production is coming from battery of hybrid vehicle.In order to make the battery SOC work in the appropriate range,the battery SOC management strategy need to be adjusted.In this paper,the research on the energy management control strategy of hybrid electric vehicle is studied by means of theoretical research,experimental research and simulation analysis.The contributions for this project are finding a higher efficiency power source,as well as providing a choice for hydrogen application based on on-board hydrogen production.This thesis based on the project of the National Natural Science Foundation “Study on Energy-saving Mechanism of HEV Equipped with Lean-burn Gasoline Engine with Hydrogen Direct Injection System and Local hydrogenous mixture” is taking the hybrid electric vehicle with new power system as research object,the main work contents and conclusions are as follow:(1)The characteristics of each system component of hybrid electric vehicle are analyzed,and the method of forward modeling is used.In the AVL Cruise software environment,the hybrid electric vehicle model is built including various system models.Then the model is tested and verified.The results show that the model is reliable and can reflect the real characteristic of the vehicle,which can use to verify the influence of control strategy on the vehicle.(2)The overall structure of the energy management control strategy is designed based on basic elements of hybrid electric vehicle control strategy,which is the guiding criterion in the design process.The control strategy is based on the logic threshold method,which main steps are respectively work mode analysis,engine work area division,torque distribution strategy.The control strategy is evaluated by AVL Cruise software and Matlab/Simulink software.Simulation results show that the work status of each system component meets the requirements of the control strategy,and the fuel economy is significantly improved.The equivalent fuel consumption per hundred kilometers is 5.92 L,which is 19.5% lower than which of the original traditional vehicle.Though analysis of the Energy-saving Mechanism of HEV,a method is proposed that can solved the bottleneck of the engine efficiency,which is limited to the overall energy saving effect of the HEV.The way is using the hydrogen fuel characteristics to assist the combustion and improve the engine efficiency.(3)The performance of the engine blending hydrogen is studied by ways of experimental study and theoretical analysis.The hydrogenation rate and hydrogen consumption rate were studied.Then the hydrogen blending strategy and hydrogen consumption rate are discussed.The problem of hydrogen source is solved by microwave low temperature plasma hydrogen production.The research on on-line hydrogen production system is developed from some aspects,such as principle,production rate,production strategy.By introducing the engine blending hydrogen and the on-line hydrogen production,a new power system of HEV is formed.After analyzing the system efficiency model of new power system is established,by which the hydrogen ratio of the engine and the input energy of the reformer are linked up.All of above,Coordinated control strategy of engine and reformer is worked up.(4)Coordinated simulation on HEV with new power system is carried out.The simulation results demonstrates that the HEV with new power system using coordinated control strategy of engine and reformer has different energy saving effect when the battery SOC is in an appropriate range.Under driving cycle of NEDC,the fuel saving rate is 3.4%.Under urban driving cycle,the fuel saving rate is about 13%,while in the case of US06 or HWY with large load and large speed,the fuel rate is slightly lower,reducing by 2.6% and 1.8% respectively.Through the analysis of the energy flow,it is found that the energy utilized efficiency increases from 20.4% to 25.4% under NEDC driving cycle,which obviously improves the energy utilized efficiency.It shows that the HEV based on the new power system and corresponding energy management control strategy has higher overall efficiency than the original HEV.Finally,the hydrogen blending ratio which is one of the main control parameters is optimized.With the increase of the ratio,the system efficiency increases first and then decreases.When the hydrogen blending ratio is 6%,the system efficiency is 27.3%.