Research On Optimization Design And Decision Evaluation Of Traction Power Supply System

Traction power supply system is an important foundation for electrified railway, especially high-speed railway (including passenger dedicated line) in China is still in its infancy with poor experience and series of problems. Previous broad-brush design methodology has been unable to meet the demands of project construction. In order to ensure the safety, reliability, high quality and economy, it is necessary to update the design idea and improve the design method and the design level. This dissertation analyses the defects in the design of the traction power supply system of high-speed railway, discusses new theories and methods and study on new power supply mode and equipment to meet the demands of future development. All the work is significant for improving the overall level of electrified railway in China, and will establish some foundation of independent technical innovation combined with national conditions.In the design of traction power supply system, there are many scheme optimization links, but comprehensive analysis and effective evaluation are lack. Therefore, an improved analytic hierarchy process combination decision making model is presented. Based on the analytic hierarchy process (AHP), the layer index system for scheme optimization is established. The index weight is calculated by the definition of the attribute significance based on the weighted sum of rough set theory. The authority and decision consistency of decision-makers are unified by group decision-making. The improved TOPSIS method by the definition of vertical distance is proposed for ranking of alternatives. So the new method satisfies the requirements of fuzzy multiple attribute decision making with uncertainty.The new method can be applied in scheme choice of traction power supply in electrified railway and traction transformer comprehensive choice. Taking under construction passenger dedicated lines for example, the analysis shows that the method features clear theory and better generality, and the scientificalness and feasibility of final scheme are enhanced. Therefore, the new method can be used to realize the flexibility design of traction power supply system.A new system reliability analysis method, called the GO methodology, is applied in the reliability assessment of traction substation of high speed railway, and the design content of traction power supply system is supplemented. Considering the maintainability and shutdown correlation of electrical equipments in substation, the simplified GO diagram is obtained taking the uninterrupted power supply as its target. Then, the quantitative and qualitative assessment of reliability is realized, the weakness of system is found and the sum of probabilities of minimal cut sets can be calculated as the upper limit of substation failure probability, which is suitable for the approximate computation in engineering design.The technical requirements of high-speed railway and the shortcomings of traction transformer are analyzed, and the YNvd transformer is proposed for traction power supply system of electric railway, which can meet the demands of existing power supply mode and is convenient for the cophase power supply transformation.Based on the strict mathematical model set up, system impedance is converted and the two-phase equivalent circuit is presented. The calculation equations of short-circuit currents and two-phase bus bars voltage loss on traction substation are derived, and the influence of the winding-impedance matching relationship and the operation mode of the primary neutral on the performance of transformer are discussed. The three-phase equivalent models of traction power supply system with comprehensive compensator and filter are given unified with power system, which can be used for interactive simulation. The digital simulation shows that the conclusions are correct.The existing traction power supply system has some defects, so new cophase traction power supply system is recommended for high-speed railway. The structures of cophase systems based on symmetrical compensation technology and active power flow controller (PFC). The functional relationship between compensation degrees of negative sequence, harmonics, reactive power and PFC capacity is given, and the design capacities of main equipments are calculated. The cophase direct and AT power supply modes of system are set up, and a new AT mode is presented, which can overcome the existing shortcomings. The control modes of PFC and the operation modes of cophase traction substation are discussed. The direct and indirect economic benefits obtained by cophase system are quantitatively evaluated and the calculation equation of investment returning year is derived. Finally, the basic functions of cophase system are proved by simulation and experiment.