Design Of Three-Phase To Single-Phase AC-dC-AC Converter In Cophase-Connected Power Supply System

Implementing the contiunous traction power supply can completely work the problem of phase and voltage break, and canceling the neural section, thus the locomotive can obtain contiunous power supply of higher quality during its operation period. Meanwhile, the transformer var can be strongly saved by averaging the power flow each substation giving out. However, the requirement of "networking high voltage, extracting low voltage" by grid system limited the feasibility of continuous power supply. According to this problem, a specific designed converter solution is proposed in this paper.In the first chapters, this paper compares the scheme of co-phase traction power supply and scheme of contiunous traction power supply and finds the differences. The rectifer side adopts three-phase PWM rectifer for making the converter a three phase balanced impedace to grid system, while enabling the power flow bidirectionally. Furthermore, multilevel switching technology is studied and applied in this solution.For achieving the new solution, two phasor analysis methodologies (Clarke and Park) widespreadly used in power system as well as the most regular controller (PI) research are technically stuied. Then the digital PLL-based phase synchronization and two modulation methods (SPWM and SVPWM) are stuided and implemented. Afterwards, the principles, controlling strategies and multilevel application are discussesd. Specifically, the drifting of DC voltages of capacitors in diode-clamped topology is studied while an auxiliary voltage sharing circuit is proposed.Eventually, MATLAB/Simulink is used to model and simulate the circuit of five-level AC-DC-AC converter and Xilinx ISE is used to develop of the FPGA-based controller platform. Validation of controller responses is performed in experimental environment before entering the online test where the IPMs are connected to the controller. The reusults show that the AC-DC-AC converter built with this solution can efficiently transform power between three-phase to single-phase network, and the inverter can connect and supply the grid correctly in laboratory field.