Research On The Variable Speed Variable Pitch Control Of The Large Scale Wind Turbine

With the increasing wind turbine unit capacity, the size and quality rotor continueto increase. Due to the great moment of inertia of the rotor, the wind turbine is relativelyslow dynamic response of the turbulence, which may cause impeller speed greaterfluctuation in the output power higher than the rated power, the conventional PI controlis difficult to suppress the fluctuation of output power, the result of a wide range ofpower fluctuations will impact grid. The same time, under the influence of wind shearand tower shadow, the non-individual pitch control will cause the unevenly distributedload on the blade are and alternating load, can easily lead to fatigue failure thatseriously affect the life of the wind turbine. The improvement of wind turbine variablespeed variable pitch control strategies and individual pitch control has played animportant role to enhance the reliability of large-scale wind turbine and theimprovement of its service life.Variable speed and variable pitch control technology of wind turbine is studied inthis paper. Through the establishment of a wind turbine system model, variable-speedand variable pitch control strategies and load optimization are studied, A optimize pitchcontrol strategies and a individual pitch control are proposed in high wind speedcondition based on the linear quadratic Gaussian control theory (LQG), the two controlstrategies are simulated.The main contents are as follows:⑴The large-scale wind turbines employ variable torque control in low wind speedand pitch control in high wind speed, the pitch controller PI parameters are designed bywind turbine linear model, and the pitch gain scheduling coefficient is introduced toincrease from the effectiveness of the pitch, create a PI pitch controller. Three groups ofturbulent wind are selected for simulation. The simulation results demonstrate theexcellent control effect of variable speed and variable pitch controller.⑵Based on LQG optimal control theory, optimization pitch control strategy highwind speed is proposed to optimize the traditional PI pitch control for improving loadsof blades and hub and stabilize output power and rotor speed fluctuations. Simulationresults show that: compared to the PI variable pitch control, LQG pitch control cansuppress fluctuations in rotor speed and power; also reduce the blade flapping load.⑶For uneven distribution loads on blades and tower caused by wind shear and tower shadow, through analysis of wind turbine linear time-invariant model, theindividual pitch control is proposed based on the linear quadratic Gaussian controlalgorithm, the LQG individual pitch control model is simulated. By comparingsimulation results of LQG individual pitch control and collective pitch control, the LQGindividual pitch control can effectively reduce the blades and hub loads and optimizewind turbine load.