Energy Management Strategy For Electric Buses With Air-Conditioning Included

With the widespread use of automotive air conditioning,while cooling or heating air conditioning system consumes about 30% energy of vehicle total consumption,and becomes the most energy-consuming accessory of the whole vehicle.Therefore,when controlling the power of air conditioning system,it is necessary to consider the efficiency of the whole vehicle,rather than adjust the power of air conditioning system in isolation.For this purpose,the thesis takes electric city bus as the research object,studies the vehicle energy management strategy including air conditioning system,so as to reduce vehicle energy consumption and battery capacity loss.Firstly,based on the principle of air conditioning system,the simulation model of heat pump air conditioning system for 12 m city bus is designed,and the type and structure parameters of components are determined.After building the model of air conditioning system in AMESim simulation environment,the refrigerant charge is optimized,then the simulation under different environmental factors is carried out,and the optimal air flow of two heat exchangers under various environmental factors is optimized.The dynamic adjustment process of the air conditioning system is studied.The functional relationship between the input variables,the input electric power,the inlet temperature of the internal and external heat exchangers,and output cooling and heating power of the air conditioning system under steady state are obtained based on the neural network.The relationship is analyzed and illustrated by comparing with the experimental results in the existing literature.Secondly,the power system model and thermal model of passenger cabin of electric city bus are established.The mathematical model of energy management problem including air conditioning is put forward while minimizing the total electricity consumption of the bus.An off-line optimization algorithm based on the idea of dynamic programming algorithm is designed to solve the two-dimensional optimization problem.The off-line optimal solutions for cooling are obtained by using the above-mentioned function between the cooling power of air conditioning and other factors,then the following rules are found: 1)When the power of driving motor is high,the electric power of air conditioning should be reduced,but should not be zero;2)When the braking energy is recovered,the electric power of air conditioning should be increased;3)Before the bus arrives at stations and opens the door,the temperature in cabin should be adjusted to a higher level,for reducing the energy loss caused by air influx;4)The temperature in cabin should not be too low,because the energy efficiency ratio of air conditioning is lower at this time.Finally,based on the rules learnt from off-line optimal solutions for cooling,the thesis designs an on-line energy management strategy including air conditioning,which controls the temperature of cabin in stages according to the characteristic of parking and door opening of city buses.Compared with the off-line optimal solution under the same initial conditions,it is found that the energy saved is close to the off-line optimal solution,and the battery capacity loss reduced is higher than the off-line optimal solution.The online strategy is applied to more than 40 kilometers cycles.Compared with the Bang-Bang control with the same average cabin temperature,it is found that the percentage of optimization is small when the air conditioning power is high at noon,and the percentage of optimization is maximum at morning and evening,which is the range of reducing energy consumption is about 4-8%,and the range of reducing battery capacity loss is about 4-7%.