Research On Control Strategy Of Cophase Traction Power Supply System Device

Considering the problems existed in the electric traction power supply system of electrified railway, such as abundant negative sequence,harmonics and reactive power, and the lost of traction speed and power which are restricted by the neutral section insulator between adjacent power supply sections, a new type of cophase traction power supply system is built by combining YN,vd connection transformer with IPFC(Integrated Power Flow Controller). The system can comb-out three-phase unbalance basically, and provides minimum harmonic content, thereby, the inconsistency between railway department and electric power department will be solved radically. The remove of the neutral section insulator conform to the trend of the High-Speed Passenger Service and the Heavy Cargo Service.In this paper, the structure of cophase traction power supply system and the performance of the YN,vd balance transformer are discussed, the structure of the IPFC,the principle of balanced transformation and the control strategy general framework are analyzed.In terms of hierarchical structure, the paper specified base layer converter control strategy, middle layer compensation power flow control strategy and top layer coordination control strategy respectively. The feasibility of the scheme is verified by the simulation result. The precondition of power quality compensation are detection and decomposition of the locomotive current. And through the power flow analysis, solving for compensating instruction currents. The middle layer proposed complete compensation strategy and complete compensation strategy, and comparison analysis had been made from steady-state to dynamic performance. While the instruction currents are given, it needs the base layer to control power electronic components tracking them fast and accurately. This paper introduced five control strategys including triangle-wave modulation, carrier phase shifted SPWM tecnology, hysteresis current tracking control, instantaneous value comparison control and one-cycle control, which have their strong point. In the transfixion power supply model, traction substations communicated with each other to distribute capacity responsibly for suppling power to locomotives. The primary and standby control of the optimal combination of traction transformer and IPFC. The optimal capacity investment under the needed power quality parameters. These are all functions of the top layer. The paper gives corresponding control strategys, and seeks the optimum scheme adapting to practical engineering.In the end, the paper put up the cophase traction power supply system simulation platform based on LabVIEW, which established the foundation to the following theoretical research.