Individual Pitch Control Design And Simulation Of Mega-watt Wind Turbine

Nowadays, wind technology has been developed rapidly in last ten years. However, there are still many unsolved challenges such as fatigue load reduction. Fatigue load is caused by many factors like turbulence, wind shear, tower shadow, yaw misalignment and unbalance blades installation. The fatigue load causes adverse effects on structures, mechanical components, and power production. At present, almost wind turbines are collective pitch control, namely three individual actuators active the same. Thus, it can not reduce the fatigue load during operation. This thesis deals with the problem of fatigue load reduction by means of individual pitch control (IPC), which is tested in simulation and experiments. The IPC is further improved by using optimal multivariable controllers LQG.An individual pitch control approach pitching to reduce fatigue load according to the real load of each blade is stated in this thesis. In other words, three actuators of blades receive different pitch commands. However, the IPC need to measure additional measurements like blade flapwise bending moment real time, which are invariants of rotating coordinate. These cause time-varying periodic system problems. Coleman transformation that maps the rotating reference frame quantities to the fixed reference frame is used to deal with these problems. In this thesis, Coleman transformation is used to transform the variants of rotating coordinate to variants of fixed coordinate. Therefore, the periodic terms of the aeroelastic equations of motion are eliminated. Thus, well developed time invariant control theory can be used in the IPC to compute pitch signals. And then these outputs are transformed back to the individual pitch signals of rotating coordinate. By using Coleman transformation, the collective pitch control design can be decoupled from individual pitch control design.This individual pitch control is simulated with real wind farm simulator TurbSim and aero-elastic load simulator FAST, which can be connected to the interface of Simulink. After that, the IPC is tested on physical platform established by the X.J. Electric CO. LTD. The simulation and test results turn out that fatigue load is reduced significantly. At the end of this thesis, optimal control algorithm LQG which consists of Kalman filter and LQR controller is used to optimize the individual pitch control. The simulation shows that optimization of individual pitch control can further reduce the fatigue load.