Research On Grid Connection Of Single Phase Voltage Source Inverter Based On Satellite Timing Strategy

Electrified railways,as an important national infrastructure,are closely related to the happy life of the people and are an efficient and environmentally friendly mode of transportation.The development of electrified railway occupies a key position in national strategies such as the "the Belt and Road","Going Global" and "Double Carbon",and has always maintained a high-speed trend.With the continuous improvement of train density and speed,China has higher requirements for various aspects of electrified railways.The existing electrified railways in China have a close coupling between the power grid system and the traction network,as well as between the traction network and locomotives,due to the structural defects of the system itself.If a certain part fails,it is easy to have an impact on other components of the system.In addition,due to the system being equipped with an electric phase separation device,there are many power supply dead zones throughout the entire section of the road,resulting in inconsistent traction for the locomotive and inability to reach higher operating speeds.The through type traction power supply system can effectively solve the problems existing in the existing system.Therefore,this thesis takes the through type traction power supply system as the object to conduct research on the grid connection of single-phase inverters,providing theoretical support for the engineering application of the through type traction power supply system.This thesis first analyzes the topology and working principle of power electronic converters in power supply hubs,including three-phase rectifiers and single-phase inverters.Emphasis was placed on the research and analysis of the control methods of voltage source inverters,and in-depth analysis was conducted on the dual closed-loop control.It was found that the general dual closed-loop control is not suitable for the system studied in this thesis,so an improved dual closed-loop control was adopted.And completed the simulation of three-phase rectification and single-phase inverter,verifying the applicability of the control method.As the connection impedance network of grid connected inverters,the traction network model was first analyzed and modeled before in-depth analysis of the circulating current characteristics of the inverter grid connected system.On this basis,the analysis of the circulating current characteristics of the inverter grid connected system was completed,and the impact of a single variable on the system circulating current was clarified,and simulation verification was conducted on it.The demand for time synchronization in the power system was elaborated,and the principle of satellite timing was emphasized.A grid connected control strategy for traction substation inverters based on satellite timing was designed.And considering that the use of satellite timing in the power system is not yet mature and its reliability needs to be verified,a backup grid connection scheme was designed and elaborated,and the proposed grid connection control strategy was simulated and verified.The simulation results demonstrate the feasibility of the control strategy,which can be used to construct the power supply network of the through type traction power supply system.Finally,a low-power experimental platform including detection circuit,control circuit,and main circuit was built,and the experimental program for grid connection control and backup grid connection strategy based on satellite timing was completed.On this platform,experiments were conducted on the grid connection control strategy and backup grid connection strategy based on satellite timing.The experiments were conducted on no-load,load added,load switching,and control switching,respectively,further verifying the various control performance and practical feasibility of the control algorithm proposed in this thesis.