A Research On The Plug-in Hybrid Vehicle Control Strategy

The automobile industry plays an important role in the development of our country.While bringing convenience to life and stimulating economy increase,automobiles,indispensable products of our daily life,are more and more wildly used,which results in the rise of deteriorating pollution and serious energy shortage issues.How to effectively relieve the pressure from environment pollution and energy shortage,while promoting the development,upgrading and reforming of the automobile industry is the focus of this industry.However,the emergence of new energy vehicles has offered a glimmer of hope for the automobile industry.This research is helpful for enterprises to carry on the development of hybrid powertrain and to accumulate key technology,which will be crucial in the development of future product and in the process of realizing upgrading and reforming.This thesis is based on a project,in which the conventional vehicle was converted into plug-in hybrid vehicle.Taking the control strategy of plug-in hybrid system as the main research content,the following work has been completed:The different structure of hybrid power system was introduced in this thesis.Considering the cost,complexity,reliability and other factors,the parallel hybrid system was selected as the research object of the thesis.The parallel hybrid power system has good comprehensive performance.Combined with the parameters of the traditional vehicle,market positioning and road driving conditions,the selection and calculation of the engine,motor and power battery were completed.The static and dynamic characteristics of each component were analyzed.According to the working characteristics of plug-in hybrid electric vehicle,the start-up strategy for charging and start-up strategy for driving were designed.Under the rule based control strategy,the CD-CS control strategy that is wildly used in the plug-in hybrid electric vehicle was designed.The disadvantage of the CD-CS strategy is that when the driving distance is more than the maximum pure electric driving range,vehicle enters prematurely into the charge-sustaining mode,resulting in the battery in a low SOC state for a long time.An improved Four-state control strategy was proposed.By analyzing the working characteristics of CS stage,the CS control strategy based on demand power was proposed.The backward simulation method was adopted in modeling the hybrid system on the basis of GT-drive.By building the vehicle dynamic model and economic model,simulation was conducted to verify parameters of components according to different indexes and to test the validity of control strategy designed.The analysis results show that the vehicle performance is in line with the design requirements,and the setting of parameters is reasonable.The Four-state control strategy is more fuel-saving than the CS-CD control strategy for it allowing SOC keep in the high efficient area.The fuel consumption per 100 km is 7.9% lower under 20 NEDC cycles.Fuel economy of engine under the CS control strategy based on power demand improved compared to engine under the control strategy based on upper and lower limits of SOC.The fuel consumption per 100 km is 11% lower under 20 NEDC cycles.