Study Of Converter Base On Co-Phase Connected Power Supply System

Co-phase connected power supply system is one of the development direction if traction power supply system, which can solve the problem of power quality and phase separation of traditional traction power supply system effectively.Chinese scholars put forward the co-phase power supply system based on APC(Active Power Compensator) and balance transformer to solve the electrified railway power quality problem and meantime, reduce half number of the phase separation.But the two-phase output of APC connecting with traction transformer secondary side presents no impact to the phase of power supply arm. So if phase difference exists in adjacent substations, the continuous power supply will be hardly to accomplished.So, a new type of co-phase connected power supply system based on three-phase to single-phase converter is brought up.It uses power electronic technology to cancel the neutral-section passing device completely, achieve the symmetrical of three-phase load and flexible control of traction network side, improve the quality of power and raise the efficiency of the system. It is a new type smart traction network.The three-phase to single-phase converter of co-phase connected power supply system is mainly studied in this paper.The topology of the converter is analyzed and the control strategy based on PI double loop is introduced. The AC inductor of three-phase rectifier, DC capacitor and AC filter circuit of single-phase inverter are designed.To verify the control performance of three-phase to single-phase converter, the simulation models of three-phase rectifier and single-phase inverter are built in Matlab.Four quadrant operation simulation is made and the performances of the rectifier and invertei are analyzed,A low power three-phase to single-phase converter based on FPGA experiment platform is built.The FPGA control circuit and IGBT driving circuit board is made and debugged.The three-phase rectifier and single-phase inverter experiments are completed on the platform.Then, the three-phase PLL and single-phase PLL is studied.The structures and principles of three-phase and single-phase PLL are introduced, and the phase-locked performance is verified on the FPGA platform. EPLL,a new type single-phase PLL, is introduced and compared with the traditional power PLL by simulation and experiment.