Study On Dynamic Model And Load Control For Wind Turbine

With the increase in the size and unit capacity of wind turbine, there is higher demandfor the whole design level in wind turbine industry. When wind turbines operate in extremeconditions, they can experience both fatigue and extreme loads. These loads affect eachcomponents of wind turbine. Wind turbine is a periodic and nonlinear-coupled system. Due tothe limitation of the filed measured data and the difficulty in establishing a complete dynamicwind turbine model, thus, an important research job is how to simplify the design model andthe use of the control strategy.The thesis firstly summarizes the current research status of dynamic model and loadcontrol in wind turbine currently. Based on the comparison of load calculation between thetraditional PI control and modern control, an aero-elastic coupling wind turbine systematicdynamic model including wind file data, aerodynamic load library of rotor and structuraldynamic model has been established, moreover, the simulation model of PI control andmodern control has also been established based on Matlab/Simulink. The major tasks aresummarized as follows:1) Based on current research status of dynamic characteristics and load control of windturbine, an aero-elastic coupling systematic dynamic model of wind turbine including windfile data, aerodynamic load library of rotor and structural dynamic model has been establishedwith structural dynamics software FAST.2) Based on the assumed mode theory, the state-space control equation based on differentdegrees of freedom has been established. This thesis establishes three state-space torquecontroller equation for a1.5MW wind turbine and analyzes the effects of control input oncontrol parameters of wind turbine. The result shows more state variables are considered,higher controllable accuracy in control model there is and wind turbine has more stableoperation.3) According to IEC standard, the wind turbine operational load conditions are determined. The load conditions of a1.5MW wind turbine have been simulated based on PIcontrol and analyzed its load law. The simulation results show that the components have themaximum loads when wind turbine operating at rated wind speed.4) Based on modern control theory, three state-space control simulation model of windturbine is established. Considering the effects of tower damping and comparing to traditionalPI control, the thesis analyzes the advantages of modern control algorithm. Compared to fieldmeasured data, the correctness of this method is verified.This thesis combines dynamic model with control strategy and lays the foundation forthe subsequent control strategy. The established linear state control equations of three-bladewind turbine can simultaneously control flexible components of wind turbine through limitedmeasured values. It is of great significance for reducing load, mitigating vibration andimproving operational stability and wind turbine life.