The Research On The Low Voltage Ride Through Technology Of Grid-connected Wind Power Generation System

With the constant expansion of wind power, it has become increasingly moreimportant to research the impact of the wind power system. Variable speed generationsystems show better converting efficiency than the fixed speed systems. Thehigh-power direct drive wind power generation system is one of the most promisingwind power generation systems. The direct drive permanent magnet synchronousmotor provides low speed, high efficiency, high power factor, thus making it suitablefor variable speed generating system such as wind power. With the development ofwind power generation technology, the low voltage grid-connected wind powergeneration system has become the focus of one of the issues.In this paper, based on the grid direct-drive permanent magnet wind powergeneration system low voltage through the control technology to conduct research thecontrol technology which measured the DC voltage protection and network sidereactive control strategies and other related technologies as well as the DC side of thejoin uninstall circuit analysis. The model of wind turbine is constructed and simulated,which provides some part of theoretical support for the low voltage ride through.First of all, this thesis has introduced the current low voltage ride throughtechnologies of wind power around the world. Then introduce the direct drive windpower system topology and operating principle and establish a wind turbine model.Secondly researches the mathematical model of the PWM converter model andDC link mathematical model have been derived. Dual PWM converter control strategyhave been derived as well, the simulation models of the controller of grid-sideconverter using voltage-oriented vector control strategy and the controller ofmotor-side converter which uses the rotor flux-oriented vector control strategy arebuilt, and the results show that the model and the control strategy are corrected, whichprovides simulation platform support for the low voltage ride through.Thirdly analyses the aspect of the converter of directly-driven wind generationsystem when grid voltage dips in detail, and then proves the accuracy of the analysisbefore by using Matlab/Simulink to simulate the running state when grid voltage dips,then describes the possible damages of the system if we do not take effectivemeasures. After that, the power dissipative crowbar and the auxiliary convertercrowbar are analyzed amply, and the advantages and disadvantages of three different measures are compared through simulation. According to the demand of reactivepower when grid voltage dips, a reactive power control strategy in grid-side converteris proposed, and its correctness is confirmed.Finally, using Matlab/Simulink toolbox to simulate the proposed control strategy,which combined with the DC side of the energy discharge circuit to realize the directdrive permanent magnet synchronous wind turbine when asymmetrical faultsoccurred. Achieve direct drive permanent magnet synchronous wind turbines in a gridof asymmetric fault off the network. The simulation results show that the controlsystem of direct-drive permanent magnet synchronous wind power on low voltage ridethrough is applicability.