Design And Verification Of Back-Toback Converter For PV/ES Connected To Electrified Railway Traction Power Supply System

At present,with the rapid development of Chinese railways,high energy consumption of traction power supply follows.Photovoltaic power generation is a form of new energy generation that is pollution-free,noise-free and simple to maintain.Connecting it to the traction power supply system through a reasonable topology and control strategy will not only help alleviate the energy consumption problem of the railway system,but also help relieve the problem.Photovoltaic consumption problem.The Sichuan-Tibet Railway is a national key project.If photovoltaic power generation can be applied to the Sichuan-Tibet Railway,it will help alleviate the power supply pressure on the Sichuan-Tibet Railway and alleviate the serious abandonment of light in Tibet.In view of this,based on an electrified railway back-to-back photovoltaic power generation system,this paper conducts the following research on the topological structure and control strategy of the back-to-back converter.First,based on the full-bridge structure,the topological structure of the back-to-back photovoltaic power generation system of the electrified railway is introduced,and the 12 working conditions of the back-to-back converter are analyzed in consideration of the energy storage system.The basic control strategy of the back-to-back converter is introduced,the limiting control strategy of the energy storage system is considered,and the simulation verification is carried out.The results prove the correctness of the topological structure and control strategy of the back-to-back photovoltaic power generation system of the electrified railway,and show that the utilization rate of photovoltaic power is greatly improved after the energy storage system and the limiting control are considered,and the problem of active power return can be effectively solved.Secondly,the reactive power compensation and negative sequence compensation strategies of the back-to-back photovoltaic power generation system,the calculation method of the compensation current and the implementation method of the compensation strategy based on the H-bridge type back-to-back converter are proposed,and the simulation verification is carried out.The results show that the compensation strategy can greatly improve the reactive power and negative sequence problems on the grid side.A control strategy for back-to-back photovoltaic power generation systems considering the recovery of regenerative braking energy is proposed.The working conditions of the power supply arm with regenerative braking energy are analyzed and corresponding control strategies are formulated.Finally,simulation verification is carried out.The results show that the back-to-back converter can perform power transfer and distribution in any direction under the control of the proposed control strategy,and play a certain role in power quality compensation.A scale-down experiment platform for back-to-back photovoltaic power generation systems for electrified railways was built,and some working conditions were selected for experimental verification.Finally,the SEPIC-type back-to-back inverter and the MMC-type back-to-back inverter are successively proposed,and their topology,working principle and control strategy are introduced,and a simulation model is built for verification.The three topology simulation results were compared to analyze the performance advantages and disadvantages and applicable occasions.Among them,the SEPIC type has the highest efficiency;the harmonic problem full-bridge structure is the lightest;the dynamic performance of the SEPIC type is the best;the full-bridge type is the lowest in cost;The difficulty of the full bridge is the lowest.At the current stage,for the construction of the low-power experimental platform and the continued in-depth research work,the full-bridge structure is the best choice;the SEPIC-type back-to-back inverter can achieve buck-boost output,which is more adaptable than other topology junctions Lower DC bus level;MMC type back-to-back inverter is suitable for high-power applications.