Research On Energy-saving Speed Tracking Control Of High-speed Train Based On Power Unit Switching

The operating efficiency of high-speed train is related to its traction load rate.When the train runs in low traction load rate scenarios(low speed limit,curves,gentle slopes,etc.),the operating efficiency of the train is low,and it has a space for improvement.Existing automatic driving control rarely considers the improvement of train operation efficiency and the reduction of energy consumption.With the overall development of automatic train driving technology,it is necessary to design energy-saving driving controllers which considering the improvement of train operation efficiency.Therefore,from the perspective of changing the traction load rate to improve train operation efficiency,this paper studies a high-speed train efficiency improvement strategy based on power unit switching,and designs an energy-saving speed tracking controller based on power unit switching which considering power unit switching frequency,aiming to improve train operation efficiency and reduce train operation energy consumption.Firstly,in order to accurately describe the train operation process and accurately calculate the train operation efficiency and energy consumption,the high-speed train kinematics model is established based on the train force analysis.According to the energy conversion relationship during train operation and the electrical characteristics of the power devices of the traction drive system,a wheel traction energy consumption model and a traction converter and traction motor power loss model are established.Secondly,establish the mathematical relationship between the operating efficiency of high-speed train and the number of power units in operation.With the goal of improving the real-time operation efficiency of trains,the efficiency improvement strategy based on power unit switching is studied under the constraints of vehicle control and power unit control.And the effectiveness of the strategy is verified by combining with the PID speed tracking controller.The results show that when combined with the application of the PID controller,the efficiency improvement strategy based on power unit switching have a good efficiency improvement effect when the train is running in the low traction load section.However,in the scene of undulating ramps,the train will have the problem of frequent switching of power units.Then,combined with the efficiency improvement strategy,an energy-saving speed tracking controller based on the power unit switching considering the power unit switching frequency is designed.The efficiency improvement strategy is designed in the speed tracking controller.The train running speed error and the power unit switching frequency are considered when the strategy is executed,and a multi-objective optimization model with the minimum speed error and switching frequency is constructed.The model predictive control theory is introduced to design a controller with predictive function and control feedback;The dynamic programming algorithm is selected as the solver for multi-objective problems,and make reasonable simplifications when establishing the state space.Finally,the controller proposed in this paper is compared with the speed tracking controller without power unit switching strategy,and the speed tracking controller based on power unit switching without considering the switching frequency,and perform simulation tests on the proposed controllers with different target weights.The simulation results show that the proposed controller with proper weight selection has good speed tracking performance and good energy-saving effect,while reducing the switching frequency of the power unit,and the control effect meets the design requirements.