Study Of The New Control Strategies For Three-Phase To Single-Phase Power Conversion System On High-Speed Railway

Generally, sections of traction network power supply station were connected and neutral sections were deleted in order to implement the continuous co-phase power supply, and to solve the problem of excessive phase and voltage in traction power supply system. This strategy could offer consecutive and high quality electric power supply to the locomotive, and could significantly save the transformer voltage of power substations along the line. However, the "high voltage networking, low voltage extracting" requirement of the public grid system restricted the availability of continuous power supply. Accordingly, the three-phase to single-phase power conversion system strategy could overcome the above-mentioned problems.Firstly, a concise introduction and comparison about the topological structure of several multilevel converters, which applied in the high speed railway three-phase to single-phase power conversion system, was carried out. Subsequently, the H-bridge cascade strategy, and a co-phase continuous power supply strategy were based on H-bridge cascade. Secondly, the double closed-loop control strategy and carrier wave phase-shift PWM modulation method of this topological structure were analyzed, and the sub-modules capacitor voltage balance control method, which was suitable for this topology, was introduced.Thirdly, A simplified operation scheme of two parallel running three-phase to single-phase power conversion system was designed in order to increase its capacity. A circulation between converters under parallel condition was designed, which verified the working performance of these converters under parallel condition by simulation. By simulation in MATLAB/Simulink, the operating characteristics of this system under multiple working conditions were verified and the availability of this topological structure in high speed railway three-phase to single-phase power conversion system was confirmed, as well as the effectiveness of the double closed-loop control strategy and carrier wave phase-shift control strategy.Lastly, by the analysis for the economic and technical norms from one-time investment to later maintenance fees for a inter-city railway, which was under the condition of meeting the traction power supply ability, it showed the continuous co-phase power supply had comprehensive benefit advantage, comparing with one-way feeding scheme, which is provided necessary condition for the further engineering application.