The Maximum Power Point Tracking Control Of Vscf Doubly-Fed Wind Turbine

In doubly-fed style variable speed constant frequency wind power generation system,the key of the wind turbine running normally is control system, the critical technology is control technology, and has the close affinity with the other units of wind turbine, whose perfect function and accurate controlling affect the efficiency and safety of the wind turbine. At the same time, the study of how to control wind turbine running at the optimal rotor speed, namely the maximal power point tracking control, turns gradually into an effective way which improves the operation efficiency of the variable speed constant frequency wind turbine, it can use wind energy ultimatly.Firstly, the paper analyzes the fundamental structure and generation principle of doubly-fed wind turbine, at the same time studies the power control methods at different wind speed, then studies the power control below the rated wind speed, according to the wind speed changes in running, the maximum tip speed ratio is kept and obtains the maximum power. Now, in many wind power systems, the rotor speed is adjusted depending on the wind speed which is measured by anemometer, the fluidity of air causes the wind speed of each point on the blade surface is different, some factors such as tower shadow and turbulence influence frequently the reliability of the system. In the paper, two fuzzy logic controllers are designed.The first one establishes the fuzzy control rulebase according to maximum power point tracking principle, obtains the reference rotational speed using the error of active power and high speed shaft speed. The second one regulates the generator electromagnetic torque according to the error of reference rotational speed and actual rotational speed as well as error variance ratio, then changes gradually rotational speed of wind rotor, it may ensure that the wind turbine is running at the optimal tip speed ratio below rated wind speed. At the same time, direct torque control of doubly-fed generator may regulate active power to ensure the grid maintains stability in operation, re-alizing maximum power control.At last, in order to verify the maximum power point tracking control method, the model of 1MW doubly-fed wind power generation system is built in MATLAB/SIMULINK, the control results are verified by simulation. As large wind turbine has the features of large timedelay, nonlinear and time-varying, system identification is introduced in the fuzzy control system, the simulation results show that improved controller gets better effect compared with ordinary controller.