Research On Energy Feedback Type DC Electronic Load For The 400kW Locomotive Power Supply Test

With the progress of computer control technology and power electronic technology,the rapid development of railway transport industry in China has become an important support for the national economy.At the same time,with the increasing awareness of environmental protection,how to save energy has become an important research direction of relevant researchers.In this paper,aiming at the electricity waste caused by the traditional factory aging test method of railway locomotive power supply,a 400 kW AC energy feedback DC power electronic load is designed,which is specially used for the aging test of locomotive power supply.Firstly,based on the comparative study of the topology structure and control strategy of the energy feedback DC electronic load in relevant domestic and foreign literatures,and combined with the technical indexes of locomotive power supply,it is determined that the 400 KW energy feedback DC electronic load developed in this paper adopts the multi-module parallel scheme.A single module is composed of front and rear cascade,the front stage load simulation part adopts LC filter circuit and phase-shifting full-bridge converter,and the rear stage energy feedback part adopts single-phase inverter and LCL filter.Secondly,the key technical problems in the design of the energy feedback DC electronic load front and rear cell circuit and the cascade of the entire power electronic load are analyzed and the solutions are given.Aiming at the fourth-order circuit formed by the introduction of LC filter circuit in the front stage load simulation part,based on the Buck circuit small signal modeling method,the transfer function of the duty cycle ratio of the input load simulation current in the front stage load simulation part is derived,and the controller of the input current is designed on this basis.Aiming at the problem of high and low frequency harmonics in the grid-connected current of the rear stage grid-connected inverter,the mathematical model of the rear stage grid-connected inverter is established,and the harmonic generation mechanism is analyzed.Based on the comparison of the existing grid-connected current control strategies,a new multi-loop control strategy based on quasi-proportional multi-resonance current inner loop control and applied full feedforward of grid voltage is proposed to eliminate the low frequency harmonics in grid-connected current.In order to improve the grid-connected power factor,an improved software phase locked loop is proposed based on DFT algorithm,and its working principle and DSP digital implementation are described.Finally,the main circuit topology and control strategy of the energy feedback DC electronic load designed in this paper were simulated by MATLAB 2016 a simulation software,and a single 70 kW module experimental platform was built for experimental verification based on theoretical design and simulation.Simulation and experimental results show that the proposed scheme is feasible and robust.