| People are paying more and more attention on energy utilization because of the shortage of resources and serious environmental pollution.Energy consumption issues shall be taken seriously if we want to achieve sustainable development and better social and economic benefits of the railway transport system.Although compared with other transports,the railway has many merits,such as lower consumption,less pollution and larger capacity,new challenges of energy consumption have appeared in railway transport system with the rapid development of high-speed railway and the boost of speed,capacity and distance.Based on the train speed trajectory theory and the characteristics of high-speed rail operation,this paper focuses on optimizing the train speed trajectory in the acceptable range of inter station running time,such that the energy consumption of the railway transport system can be reduced.The model and algorithm for train speed trajectory optimization are discussed from two perspectives of single train’s and cooperative train’s regenerative energy.In detail,this paper does the following research works:(1)We firstly analyze the distribution of energy consumption in railway system as well as its influencing factors.The data show that the energy consumption of train operation accounts for 80%of the whole energy consumption in this system,which means that decreasing the energy consumption of train operation has the greatest potential.Based on that,how to optimize the train speed trajectory to achieve the purpose of energy saving comes to our minds.The method of applying this theory into practical energy saving speed trajectory of railway train is considered according to the ATO control principle.(2)There are many different control methods for the same type of trains in the limited time to run for the due distance,and different operating methods directly lead to different energy consumption.Therefore,with the design of different gears of the train,this paper analyzes the traction and deceleration process to design and optimize the train speed trajectory.On this basis,more sophisticated train driving strategy characterized by the gear sequence and the switching locations are specifically considered.(3)Because of the different physical environment(such as line grade,trajectory radius,etc.)in the running process,there inevitable exists different speed limit range over the whole line.Therefore,considering the line environment,the speed limit interval is discrited to meet the requirement of train speed trajectory.(4)To evaluate the effectiveness and efficiency of a railway transportation system,there are usually two kinds of the train operational performance metrics that need to be considered,(i.e.,the energy consumption and travel time).More specifically,the energy consumption is related to the benefit of railway operation companies,and travel time is referred to evaluate the service quality for passengers.Under this situation,we develop a bi-objective mathematical model for reducing energy consumption and travel time.For obtaining a non-dominated solution with balanced satisfaction degree on both objectives,we apply a fuzzy multi-objective optimization approach to turn the original model into single-objective optimization model by using the max-min operator.(5)A cooperative train trajectory model is proposed considering the energy efficient train trajectory and the regenerative braking.With different headways,the train speed trajectory was collaboratively optimized to achieve better utilization of regenerative braking kinetic energy.As a result,the satisfaction degree of the actual energy consumption and the actual operation time can be achieved.(6)Based on the above mathematical model,a genetic algorithm is designed to find the approrimate-optimal solution.According to the real operational data from the Beijing-Tianjin Intercity Railway,some numerical experiments are implemented to illustrate the effectiveness of the proposed model and solution methodology. |
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