Research On Cophase Power Supply System Of Electrified Railway

Facing the construction of high-speed railway, strengthen the high-speed rail technologyis urgently demanded. Problems such as the special structure of the electrified railway powersupply system and crossing neutral sections in electric railway are in the way of developmentof speedy, heavy railway. Cophase power supply technology could eliminate unbalance of thethree-phase, filter out a part of harmonic and compensate reactive, improve the power quality.Thus, crucial conflicts between railway sector and power sector can be resolvedfundamentally, and neutral section insulator at traction substation exports can be avoidedessentially in order to achieve the development of the high cargo service and high-speedpassenger requirements.Starting from the important part of the cophase power supply system-the structure oftraction transformers and integrated power flow controller, this thesis focus on the analysis ofnegative sequence current characteristics, capacity utilization, advantages and disadvantagesabout four transformer which could be used in cophase power supply system, as well ascapacity utilization and balance performance about integrated power flow controller of twostructure. After the author’s analyses and comparisions, YN,d11transformers combining withthe form of three-phase three-leg integrated power flow controller and YNvd transformerscombining with the form of back-to-back integrated power flow controller constituting thecophase power supply system were selected to conduct this research.Combining traction transformers with integrated power flow controller, two types ofstructure of the cophase power supply system were worked out. Two cophase power supplysystem program were analyzed, including individual balance transform conditions andnegative sequence, reactive, harmonic compensation degree. At the same time, two cophasepower supply system instruction current generating method and relevant control strategy wereanalyzed as well.These two different schemes of the cophase power supply system are simulated underMATLAB/Simulink. A simulation comparison were made relating power system sidewaveform of before and after integrated power flow controller put into cophase power supplysystem, whose results verified the effectiveness of the cophase power supply technology.Meanwhile, feasibility of the two cophase power supply system is testified, including systemstructure, balance transformation, comprehensive compensation current detection method, thecontrol strategy.