Minwu Chen

Optimized Design and Performance Evaluation of New Cophase Traction Power Supply System

The traction power supply system of electric railway has the disadvantages of heavy unbalanced three phase, large harmonics and reactive power, needing neutral section insulator in every supply sector, which conditions the improvement of high speed and heavy-haul railway. New cophase traction power supply system can solve these problems radically. In this paper, connection type of traction transformer and the optimum matching topology of comprehensive power flow controller (CPFC) are discussed based on the mathematic model. The cophase direct and AT power supply models are set up, and the properties are analyzed. The control modes and operating performance of system are demonstrated, and the modes can be switched according to system status. Compared with the existing system, the economy of new cophase traction power supply system is evaluated. These studies have great significance on the design and application of new cophase traction power supply system. Keywords-cophase traction power supply system; mathematical model; design; evaluation

Mathematic Model and Operating Performance of YNvd Transformer

The YNvd transformer, which is one kind of three- phase three-winding balance transformer, has several properties and can be used in traction power system of electric railway. Based on the magnetomotive force balance equations, winding connection equations, output-port equations and voltage transfer equations, the mathematical model of the YNvd transformer is set up. The performance of transformer in different grounding mode is discussed. The two-phase equivalent circuit in secondary side is obtained with the source impedance of the power system taken into account. The short-circuit current calculation formulae are deduced when variety kinds of short-circuit failure appear in the traction power substation, and the voltage losses of bus bars are calculated. These studies have great significance on the application of YNvd transformer.