Researchon Optimal Power Control Of Double-fed Wind Turbine

With the rapid development of wind power in the world，the reliable and stableoperation control has been out of question.The research of optimization technology onvariable speed constant frequency wind turbine became the key and hot topic all over theworld. How to bring in advanced control theory and efficiently control the wind turbinehave been the concern for many scholars，which have significant research value.In thisdissertation，based on the major project“The developing of double-fed variable speedconstant frequency wind turbine adapt to sea and land environment”supported by nationalscience and technology，the3MW double-fed variable speed constant frequency windturbine was taken as the research object，control strategy below rated wind speed，thetransition stage and above rated wind speed control strategy had been carried out in-depthresearch. Its control objectives from a single to multi-target development，which aims tofurther optimize the output power of3MW doubly-fed wind turbine.This dissertationstudies the following issue：Firstly，Iulian Munteanu，a famous scholar，divided the wind speed into transient windspeed and steady-state wind speed，according to the multi-time multi-scale characteristicsof wind speed. Considering the low wind speed conditions and high wind speed conditionsgenerator torque control strategy，steady-state controller and transient controller aredesigned at low wind speeds，it’s purpose is obtaining the largest wind energy as well asreducing the electromagnetic oscillation.One design is based on the control of LQGoptimization and compared with the PI controller，and simulation results show that theproposed control method is effective. The other design of pitch steady-state controller andtransient controller at high wind control，which is to maintain a constant power output andto introduce multi-target hybrid control to disturbance decoupling ring control instead ofthe original single target control，can achieve compensation between the multi-objectivecontrol strategy and farthermore，achieve a goal of getting the simulation analysis of3MWwind turbine. Secondly，many problems are acitived near switch point，such as the frequencywitching between pitch control and torque control，system oscillating，wind power unitefficiency reduced and so on，a new kind of feedforward compensation power optimizationcontrol strategy based on the wind speed estimation is put forward.The purpose is transientprocess of different operation states rapidly goes and thus can effectively reduce thesystem dynamic load，and then verify the feasibility and effectiveness of this strategythrough simulation and experiment.The experimental results show that the new method，which can effectively reduce the generator output power fluctuation，has a good controleffect.Finally，the3MW wind turbine half physical test platform had been built throughwind farm wind conditions simulation. LQG optimization through the analog wind farmwind conditions the disturbance decoupling loop control optimization based on wind speedestimates feedforward compensation power control strategies are studied.In the testplatform，the rotor，generators，towers and controller are simulated with GH Bladed，drivesystem，variable pitch propellers are actual deivce. The entire semi-physical experimentsstage equivalent to complete wind power systems.The experimental results shows that thedesign of the control strategy meet the demand of wind turbine control，simulation resultsand theoretical studies are both correct and effective.