Research On Independent Pitch Control Of Permanent Magnet Synchronous Wind Turbine

Unified pitch control of wind turbines is based on uniform wind speed acting on the rotating surface of wind turbines.The main control objective is to maintain the constant output power of the fan by changing the pitch angle of the blade when the wind speed exceeds the rated speed and the speed of the unit rises to the rated speed.However,due to the existence of wind shear and tower shadow effect the wind speed of blade rotating to different directions is different This will lead to different aerodynamic forces on the blades,which will lead to the oscillation and waving of the blades.Ultimately,it will cause the vibration of the unit and even resonance with the tower,which is not conducive to the stable operation of the unit.Independent pitch control can effectively solve the above problems.Firstly,the mathematical model of permanent magnet synchronous wind turbine is established,the principle of pitch control is introduced,and the control objectives of unified pitch and independent pitch are defined.Secondly,the blade element-momentum theory is used to model the unbalanced load acting on the fan blade,and the blade load is simulated when considering wind shear and tower shadow effect.Two common independent pitch control strategies,blade root load feedback method and azimuth weight coefficient distribution method,are described in detail.The independent pitch control strategy based on load feedback is improved.Aiming at the problem that the parameters of traditional PI control are difficult to tune,RBF is proposed to tune PI parameters online,and the proposed control method is verified by simulation.The results show that the proposed control strategy has better adaptability than the traditional PI control,and can further reduce the unbalanced load on the rotating plane of the wind turbine.Aiming at the problem of randomness of wind speed,ADRC control is adopted for independent pitch control.The aim of independent pitch control is to reduce the offset of blades and the fluctuation of the offset rate.By designing an independent ADRC controller,the unbalanced load of the unit can be balanced,and the yaw and pitch vibration of the fan can be reduced.In this paper,considering the influence of wind shear and tower shadow effect,the relationship between the fluctuation frequency of torque and the fluctuation frequency of unbalanced load on blade is analyzed by simulation.In order to balance the unbalanced load of the unit and reduce the fluctuation of the aerodynamic torque of the wind machine,a control ring based on swing load is added to the existing swing load control ring,and the weight distribution of the pitch angles of the two types of independent propellers is carried.