Research On Control Strategy Of DFIG And Wind Farm Modeling

As an effective way to develop and utilize of wind energy, both at home and abroad inrecent years the wind power generation has been rapidly developed, in which, the doubly fedinduction generator (DFIG) has become the mainstream wind turbine with its outstandingadvantages. The ability of low voltage ride-through is the key problem to realize the operationfor the wind power generation.The reserch about wind farm modeling is also important as theincreasing of the capacity of wind farms. So in this paper, the author made some researchabout modeling, simulation, control strategy of DFIG and the modeling method of wind farm.The main contents of this paper can be summarized as follows:1.This paper introduced the structure and operating principle of double fed windgenerator, a detailed mathematical model of the DFIG is derived based on the vector controltechnology, then the control strategies of the the rotor side and grid side power converter areestablished, finally build a simulation model on the PSCAD/EMTDC platform, the simulationshow the common method’s validity, under the conditions of wind speed fluctuations andfaults, this paper analyzes the system steady and transient response characteristics in detail.2.To address the issue that the common control method can’t meet the requirements oflow voltage ride through for DFIG, on the base of analyzing the transient characteristics of thewind turbine under fault conditions, a series of improved control strategies are proposed, suchas stator flux compensation, rotor negative sequence current compensation, etal. Finally, thevalidity of the methods are verified on the simulation platform.3.Based on the control strategies and operational characteristics of DFIG, a simplifiedequivalent modeling method using controled current source is presented, to avoid thecomplexity and erros from common equivalent modeling method. Through the comparison ofoutput characteristics of the detailed model and equivalent model of wind farm at thegrid-connected point under wind speed fluctuation and fault condition, the effect of thedescribed equivalent is verified, lastly, the reasons which lead to the errors of equivalent windfarm models are analyzed.