Study On Tracking Of The Largest Wind Power In DFIG-based Wind Power System With Variable Speed Constant Frequency

With the deterioration of global ecological environment and shortage of energysources, various countries are increasing investment on the new green energy inaspects of capital, policy and technology. Among all the new energy, wind energy hasa large potential and also been favored in recent years. The current wind powersystem is increasingly going to large scale direction, VSCF doubly fed wind powersystem’s advantages become increasingly obvious, especially the feature of realizationof constant frequency and voltage of output power in wide wind speed range hasattracted people’s attention. This paper, by using VSCF doubly fed wind power systemas the main object of study, firstly in-depth analysis of the basic principle and theoperation mechanism of wind turbines and doubly fed generator, on this basis, usesthe vector control technology to power decoupling control of DFIG wind powersystem, and establishes the mathematical model of the wind power system body. Thenusing the maximum wind power captured by the wind machine as the control target,and from the point of view of the utilization rate of wind energy, the importantresearch is on maximum wind power tracking control.Doubly fed induction generator power decoupling control is the key to achievevariable-speed constant frequency state of wind power system, if the decoupling is notappropriate, it will make the system control becomes very difficult, serious situationwill make the electromagnetic motor interference or shock, so that the system can notrun normally. Based on the analysis of the doubly fed induction generator principle,equivalent circuit, power flow, this paper uses the vector coordinate transformation tochange mathematical model of DFIG from three phase static coordinates to thetwo-phase synchronous speed rotating coordinates, and do power decoupling controlon it by vector control of the stator flux oriented vector, and establishes the overallsimulation of wind power system model, and the simulation results shows theeffectiveness and feasibility of the control method.The running course of large wind turbine can generally be divided into threestages, namely the starting stage, less power and rated power holding stage, for thedifferent stages, the maximum wind energy tracking control strategy is different. Inthe start-up phase, the output power of wind turbine is zero, and the utilization rate ofwind energy is minimum, there is no wind energy tracking problems, and thegenerator and grid is detached; In less power stage, wind speed is below the rated wind speed, the output power of wind turbine is generally not exceed the rated power,so there would not exists security problem, more attention is putted to maximize theoutput power of wind machine; In keeping at rated power stage, because the windspeed is large, security issues should be even more concerned about the wind powersystem, generally relies on wind turbine pitch control and rotational speed control ofgenerator to limit the wind power system for wind energy absorption. Therefore,based on the maximum wind power tracking under stage as the research key, thispaper conducts a comprehensive analysis of the theory on the process of wind turbineto capture wind energy, posing the application of maximum wind power trackingbased on the ant colony algorithm of self-tuning PID, specifically designs ofself-tuning PID controller based on ant colony algorithm, and does correspondingsimulation analysis, the simulation results shows that the proposed control strategynot only makes the control system has good dynamic performance, but also improvesthe precision of control, in the aspects of wind energy utilization rate is superior to thetraditional PID control method.