Research And Design On DC Feedback Type AC Electronic Load

As an important part of power supply system on High-speed trains and Ordinarypassenger trains,locomotive inverter power directly affects the stability of the train and the passengers’ safety,therefore,its essential to have strict load test before these inverter power can be used in practice.Aiming at the problems of poor flexibility and high energy consumption in traditional energy consumption load,a kind of energy feedback type AC electronic load which can meet the various load test requirements and feed back energy to the DC power supply side is provided,the research contents are as follows:(1)By considering the test demand of inverter and the working environment of electronic load,a kind of DC feedback type AC electronic load is designed based on the traditional energy feedback type electronic load,which uses PWM rectifier as simulation unit and phase-shift full bridge converter as DC feedback unit.At the same time,the overall structure of the electronic load test system and the functions of each part of the system are analyzed.(2)The principle of PWM rectifier simulating linear loads is analyzed in detail,and the mathematical model is established by introducing the switching function.According to this model,the current loop control system based on PI controller of simulation unit is established and the controller parameters are calculated by different parameter tuning methods.In order to improve the system tracking ability,the proportional-resonance(PR)controller is used in current loop.Also,the demands of load simulation unit phase lock has been taking into consideration to design the software phase-locked loop which is based on DFT algorithm.The simulation results show that the phase-locked loop can obtain the phase of the input voltage quickly and accurately.(3)The condition of energy feedback unit to realize soft switch is analyzed,a double closed-loop controller is designed based on the mathematical model of the energy feedback unit which is already established by the state space averaging method.According to the course of the DC input voltage harmonics,a digital notch filter is designed which can effectively filter out the input voltage harmonic and improve the feedback current quality.(4)According to the electronic load technical indicators,the main components of the circuit are determined.Aiming at the requirement of electronic load function,the system control board based on DSP and CPLD is designed,and the working principle of key function circuit of control board is analyzed to complete DSP software program design.(5)By using the simulation software MATLAB to build the electronic load simulation model,the simulation results have verified the feasibility of the design.Further more,the low power experiment on the electronic-load-prototype-platform is carried out,which proves the correctness of the theoretical research and the feasibility of the scheme.