Investigation On Critical Technology Of Doubly-Fed Wind-Power Induction Generation

In the past twenty years,especially as a result of the combined effects of environment, economy,society,and technology,many countries all over the world have made tremendous achievements in the field of wind power generation.The power of wind-power generator of cutting-in has exceeded megawatt.In the long run,wind field that be transfered from the land to the ocen will be found to be broad prospects opening.As a important part of a wind power system,the wind turbine is the convertible facility of wind energy,whose matching with wind energy of the wind farm has great influence upon the operating of the system.Based on the principle of power conversion of the wind turbin and vortex theory of aerodynamics,the relations among power coefficientC_p,tip speed ratioλand blade pitch angleβare deducted in order to trace optimum power point which can capture the maximal wind energy.The double-fed generator,who is superior to a general AC one in many aspects is the core of the wind power system.From the basic principles and the analysis of the essential operating characteristics,this paper offers the theoretical foundation which base on the power flow of the system so as to control the output power.States equations models in the m-t reference coordinate system are deducted in details,and the stator flux-oriented vector control system was depicted to decouple the stator active and reactive power regulating,so we complete the destination which the motor performances are controled simplily.In order to trace maximal wind energy,the discourse confirms the control scheme of variable-speed constant-frequency generator basing on power flow of the system and explains power control mechanism of the wind turbin in different speed scope with simulation results of the turbin charactristics. By analyzing the operation behavior of an A.C.excited variable-speed constantfrequency (VSCF)wind-power generator,the field-oriented vector control scheme was transplanted into the cutting-in control of the generator and the investigation of the no-load cutting-in control strategy for the A.C.exited generator was further made in this paper. Based on the theoretical study,a no-load cutting-in simulation model was then established and employed to make a comprehensive system simulation on the no-load operation before the cutting-in and the VSCF wind-power generation by tracing maximal wind-energy after the cutting-in.The simulation results offer a good review of the cutting-in control effects.