Research On Compensation Strategy Of Main Substation For Advanced Co-phase Traction Power Supply System

There are some problems in the existing traction power supply system,such as neutral section and power quality,etc.The advanced co-phase traction power supply system with output-transformer-less(OTL)can accurately control the output voltage amplitude,frequency and phase of the substation through the output voltage of the cascade converter to the traction network,so as to effectively sol ve the power quality problem and fully connect the traction power supply system.However,a large number of power electronic converters are required to be cascaded to meet the existing capacity requirements of the traction substation,which make the system control complexity increase and the reliability decrease.Therefore,a new advanced co-phase traction power supply system was proposed in this paper in order to solve the problem of insufficient capacity of traction power supply system.The new system was taken as the research object,the compensation strategy of the general compensator was deeply studied and the feasibility of the general compensator was verified by theory,simulation and experiment.Firstly,the topology of the main substation and other substations in the new advanced co-phase traction power supply system was designed in this paper.On this basis,the causes and current characteristics of the negative sequence and harmonic current of the fixed phase loss were analyzed and the mathematical model and modulation strategy of the general compensator were studied.Secondly,the frequency-selection characteristics of the integrator were studied.It is found that the complex vector filter of the integrator structure can be used to separate the positive and negative sequence current components when there is an orthogonal relationship between the two input current signals.On this basis,the fundamental wave positive sequence current detection method based on the second order decoupling complex filter(SO-DCF)of the general compensator was proposed,the validity of which was verified by simulation.Thirdly,dq decoupling control strategy and predictive current control were studied in order to make the general compensator maintain the stability of DC s ide voltage while compensating the negative sequence and harmonic current of the fixed phase loss.In addition,the feasibility of the general compensator control system was verified by simulation.Finally,the experimental system of the general compensator was designed and a low power experimental platform based on FPGA was built.The experimental results show that the general compensator can effectively compensate the negative sequence and harmonic current of the fixed phase loss,thus laying a solid foundation for the engineering practice of the new advanced co-phase traction power supply system.