Research On Energy Consumption Assessment And Optimization For Traction Power Supply System Of High-speed Railway

The electrified railways in China have the following features,a large scale of operation,multiple levels,sophisticated power supply methods,and abundant train types.Besides,the operation scale of the China Railway is continuously expanding,especially its high-speed railway(HSR).Moreover,the traction power supply system(TPSS)has various characteristics,such as frequent shocks,high power,high density,and networked.These characteristics resulted in more and more challenges for providing high-quality and efficient power to the TPSS.These challenges are mainly manifested in the following aspects.1)As the most significant single load of the utility power system,the energy consumption issue of the TPSS in HSR has become increasingly prominent.2)It is a trend to construct a hub traction substation with multiple feeders and multiple power supply sections.3)The scheduled train timetable is adjusted more and more frequently.All the challenges are also the areas that need to focus on in dynamic modeling,system-level energy consumption analysis,energy consumption optimization,and analysis method software in TPSS.Therefore,this thesis conducts theoretical research on the energy consumption of TPSS for HSRs.It mainly deals with related topics,such as dynamic traction load modeling,system modeling,and power flow calculation,systematic energy consumption analysis,energy consumption optimization,and functional software development,during the dynamic operation of TPSS.The research work of the thesis mainly includes the following five aspects:(1)Primarily,it studied a modeling method for the dynamic traction loads considering the train's motion and the scheduled train timetable.The dynamic load characteristics of a moving train were analyzed with the field measurement data,including the active power and dynamic power factor.Then,the dynamic apparent power model is established with traction calculation technology,power transmission performance in the traction drive system,and the fitted dynamic power factor.On this basis,it constructed the dynamic load models of the entire railway in 24 hours with the information,such as the train trips,train types,and operating hours,provided by the scheduled train timetable.(2)It studied a modeling method for dynamic TPSS and related power flow solutions.Based on the real-time load parameters,including the number and location of moving trains,the topology of the TPSS at any moment is determined.Then,it provided a general modeling method for the hub-TPSS,that power multiple feeders,based on the mathematical model of components.Consequently,it calculated the dynamic fundamental power flows of the TPSS.Case studies verified the modeling methods about the traction load and TPSS,as well as the dynamic fundamental power flow algorithm.Furthermore,the reactive power problem of the HSR was studied using the proposed methods.Moreover,it found that the train's quantity is the major issue that causes a low average power factor in the HSR.(3)It analyzed the energy consumption of the HSR systematically.The entire TPSS was divided into three subsystems,including the traction power supply network(TPSN),traction drive system(TDS),and wheel track motion system(WTMS),according to its operation mechanism.Moreover,it analyzed the energy dissipation characteristics of each subsystem in-depth.In which,the dynamic traction load model and the dynamic power flow calculation method of the TPSS were highly approved to calculate the dynamic energy consumption of each energy consumption cell throughout the day.Besides,the power flow direction was dependent on identifying the energy sources,which are the utility system energy and regenerative energy.Moreover,it calculated the corresponding energy consumption statistics.Consequently,it constructed a system-level energy consumption database.Furthermore,it proposed an evaluation system based on energy consumption and energy efficiency.Finally,it conducted a few case studies to verify the correctness and practicability of the system-level energy assessment method.(4)An integrated energy-saving strategy was proposed with a sensitivity analysis method for the TPSS of HSR.It established a simplified energy consumption analysis model for the TPSS.Then,it derived the key factors affecting the total energy consumption of the system,including the electrical parameters of the traction power supply system and the technique speed.Moreover,the degree of influence of various factors on the total energy consumption of the system was discussed through simulations.Furthermore,the sensitivity analysis method was used to identify the most influential factors,and it found that the operating speed shapes the total energy consumption of the TPSS.On this basis,it proposed an integrated energy-saving scheme,which includes two steps.Primarily,an optimal operation trajectory is proposed based on the infrastructures' condition to reduce the total energy consumption of single train operation.Besides,a regenerative energy recovery scheme based on the single-phase 4-quadrant converter and supercapacitor was applied to reuse the regenerative braking energy during multi-train operation.Consequently,the total energy consumption of the whole system was reduced.(5)Ultimately,it dedicated to make the dynamic analysis method of TPSS into useful software.It analyzed the requirements of the simulation platform,considering the dynamic characteristics of the TPSS.Moreover,the modular ideas were applied to simulate the major functional parts,including utility power system module,dynamic traction load modeling module,TPSS modeling,and load flow calculation module,and system-level energy consumption and power quality assessment module.Furthermore,it described the implementation process of the simulation platform,and simulation examples verified the practicality of the platform.This thesis has studied theoretical analysis methods about the energy consumption of TPSS.It consists of dynamic modeling,power flow calculation,energy consumption analysis and evaluation,and energy consumption optimization.Practically,a dynamic simulation analysis software for the TPSS is developed.The analysis methods in this paper can accurately analyze the dynamic characteristics of the electrical quantity of the TPSS.Ultimately,it can realize the energy-consumption as well as the power quality analyzing and evaluation in a whole HSR of 24-hour period scheduled with the train timetable.