Design Of Grid Simulator Based On The Three-Phase Four-leg Inverter

As one of the renewable energy in the rapid development in recent years,wind energy resources are widely distributed,huge reserves.With more and more wind power in power grid system,its stable operation of power grid and the grid power quality has a direct influence.National power supply company for the power grid wind power generation system is put forward strict requirements,namely fault crossing ability.Because it is difficult to control power grid failure,and high cost of retrieval failure conditions,therefore,an urgent need to develop a perfect performance of grid simulation grid fault.This paper introduces the structure,a variety of traditional grid simulator puts forward selecting three phase four inverter bridge arm as the inverter part of grid simulator,the modulation mode and control strategy are studied,to improve the voltage loop controller.The concrete research content is as follows:1?The analysis of the dynamic failure of power grid and the harm of static fault and its corresponding.Introduce the main functions of the grid simulator,including simulation grid voltage,normal amplitude and frequency change,unbalanced three-phase voltage,waveform distortion,etc.The main circuit structure of the grid simulator are analyzed,including the converter unit,input unit,output unit and test control unit.2?Topological structure of the traditional grid simulator and the analysis of existing problems.In view of traditional topology switching devices and the poor with unbalanced load capacity problem,put forward with threephase four-wire inverter as the grid simulator inverter topology,contrast variety of three-phase four-wire inverter,selected three phase four inverter bridge arm as the topology of the network simulator used in this paper.Analyzed the working principle of three phase four bridge arm,and the modulation scheme is studied,using three harmonic injection PWM modulation,improve utilization rate of dc voltage system.Given the same conditions,the simulation sine wave modulation and harmonic injected three times two kinds of modulation mode.3?The Central Line with inductance inverter circuit structure of three phase four bridge arm,analysis of three phase four inverter bridge arm its performance characteristics and then to design the control system.ABC in three-phase static coordinate system and static alpha beta respectively 0 coordinates to establish its mathematical model and construction of the average model for the control model.For traditional PR control belt width,the grid frequency deviation of sensitive problem,put forward the improvement of PR control,and to improve the PR controller of multiple values in detail the control parameters of the simulation analysis.For specific harmonics caused by nonlinear load,the parallel multiple improved PR controller for astatic tracking control.Finally,by Simulink simulation,the results show that the improved PR controller has very good astatic tracking ability,reduce the THD of output voltage,ensure system access various load cases can also output three-phase voltage harmonic content is small.4 ? On the basis of above research,build grid simulator based on Simulink simulation model,the corresponding simulation results are given.According to dSPACE hardware system and software system design methods,design grid simulator experiment platform based on dSPACE,further verification in this paper,we study the effectiveness of the grid simulator.