Single-Phase Half-Bridge Three-Level AC-DC-AC Converter In CO-Phase Power Supply System

The traditional railway power supply system exists for reactive power and negative sequence, harmonics, unbalance problem, and the problem of neutral sections, these seriously restricts the efficient operation of the train. As a new type of traction power supply system, co-phase power supply system has successfully solved power quality problems, at the same time, the problem of neutral sections is eliminated. In this paper, single-phase half-bridge three-level AC-DC-AC converter in the co-phase traction power supply system is studied, theoretical analysis, simulation, experiment verify the feasibility of the system.This paper introduces the selection of traction transformer, through a variety of transformer structure, working principle, power analysis, the YNvd balance transformer is selected; the topology and principle of single-phase half-bridge AC-DC-AC converter is studied, inverter should control the input current is equal to half of the load active current, the output current is equal to half of the load active current, all the reactive current, so as to achieve the purpose of co-phase power supply; mathematical model and the principle of the transient current control strategy is studied, I use the transient current control strategy to control DC voltage stability, and the input power factor is one in the converter input side; mathematical model and the principle of the control strategy based on single-phase d-q coordinate is studied, I use the control strategy based on single-phase d-q coordinate control the output current is equal to the value of the test in the converter output side.Based on these studies, I use Matlab/Simulink simulation platform to build the transient current control of single-phase half-bridge three-level rectifier simulation, the control strategy based on single-phase d-q coordinate of single-phase half-bridge three-level rectifier simulation, and finally set up overall system simulation. The DC side voltage, input side and output side current are analyzed under the condition of starting, no load and load. The simulation results show that the transient current control strategy can achieve the power factor is one, and the DC voltage stability in the input side; the control strategy based on single-phase d-q coordinate can achieve any power factor control in the output side, when the output current is equal to half of the load active current, all the reactive current, you can achieve the purpose of co-phase power supply.Finally, I build a low-power FPGA based experimental platform to complete the transient current control of single-phase half-bridge three-level rectifier experiment, the control strategy based on single-phase d-q coordinate of single-phase half-bridge three-level rectifier experiment, and experiment of system. The experimental results further verify the correctness of system converter structure, the control strategy, the modulation strategy, and the feasibility of the implementation of the co-phase power supply system.