| The conventional vehicles with internal combustion engines cause serious environmental pollution due to fossil fuel consumption.Electric vehicle has become increasingly popular in recent years because of its advantages in energy security,environmental protection and sustainable development.With the rapid development of electric bus,the air conditioning system,which is the second largest electric energy consumption unit after driving system,has become a constraint to dynamic,economy and driving ranges of electric bus.Therefore,an energy-efficient and widely used air conditioning system is very important to promote the application of electric bus.In this paper,an air conditioning system solution for electric buses has been presented.Moreover,this system has been optimized by means of theoretical analysis and experimental study.The main contents and results are as follows:An air conditioning system solution which adapt to different regional conditions throughout the year has been presented after comparing various projects.The system is integrated advanced technologies,such as the inverter technology,two-stage cycle technology and additional waste heat source heat pump technology.The system can meet passenger demands for the temperature under general conditions as well as very low outdoor temperature,and it can run efficiently and steadily at the same time.A mathematical model about air conditioning system for fully electric bus has been established.It includes compressor models,heat exchanger models,electronic expansion valve models and so on.And then all components models are connected to form a system model which can predict the performance of the air conditioning system according to the coupling relation among these components.Moreover,the waste heat discharged from electric devices in electric bus is first introduced into the system model,which can benefit the performance of heat pump system.An experimental sample of variable frequency heat pump air conditioning system for fully electric buses has been assembled and tested.Effects of compressor and fans speeds on system performance have been analyzed according to the experimental results under the nominal working conditions.The experimental results compare very well the simulation ones,which show the simulation model is valid and accurate.The regulating directions for improving system performance have been given after analyzing the effects of various factors.Effects of disturbance factors and regulation factors on system performance in the cooling mode and the heating mode are provided.Consequently,the changing rules of cooling/heating capacity,power consumption and EER are drawn.In addition,the temperatures switched point between single-stage cycle and two-stage cycle in the heating mode are presented.Furthermore,the heating capacity and EER in the dual source heat pump,which uses both air and waste heat,are increased by 10.7% and 9.73%,respectively,compared to those of the air source-only heat pump system.The optimal control strategy for variable frequency heat pump air conditioning system for fully electric bus has been produced.First,the optimization model is introduced.Second,the objective function,control parameters and constraint conditions are given.Third,a hybrid adaptive genetic algorithm is developed.This is followed by the optimization of the given system using the algorithm.Lastly,the optimization control is performed for the system with dynamic load based on the optimal results,which can ensure the optimal operating state all through. |
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