Nonlinear Control Of Multi-terminal Suspension Of Wind Turbine Nacell

The control objectives of this paper are stable suspension and pitch suppression,and the stability of the nacelle is seriously influenced by the severe working conditions,time-varying interference,multi-terminal magnetic circuit coupling and the structural parameter difference of the multiple actuators.The suspension stability,pitch suppression and anti-disturbance capability of the wind nacelle were fully improved by prescribed performance control(PPC)using model reference adaptive,fuzzy state observer,sliding mode control,finite time control,fuzzy intelligent approximation and prescribed performance control(PPC).Research was carried out from the aspects of system mechanism modeling,control strategy design,stability proof,simulation analysis and experimental verification.The effectiveness of proposed control strategy in this paper was verified by comparing the experimental and simulation performance of multiple control strategies under various operating conditions.In view of the magnetic force distortion between the fixed rotor of the suspension system of the wind nacelle,which is easy to cause the electromagnetic suction to change with the position,a two-degree-of-freedom suspension system model of the wind nacelle with single winding was constructed considering the non-uniform magnetic force line,and a finite time model reference adaptive suspension control strategy based on the fuzzy state observer was proposed.An adaptive reference model of finite time model with fractional power function is constructed for the first time.In view of the suspension velocity and the unknown nonlinear uncertain term in the model,an observer of air gap velocity and uncertain term based on fuzzy intelligent approximation is designed.The model reference adaptive tracking control law is derived by using Lyapunov function stability theory and model matching principle.A Lyapunov function containing model approximation error,observation error and uncertain parameter approximation error is constructed.It is verified that the above variables can achieve finite time convergence,and the convergence domain can be adjusted by controller parameter optimization.Based on MATLAB platform and magnetic levitation ball experiment platform,the multi-reference signal tracking test and anti-disturbance test were carried out respectively.By comparing the performance with traditional PID,sliding mode control and sliding mode control based on neural network intelligent approximation,the results show that the strategy proposed in this paper has obvious advantages in tracking performance and anti-disturbance.The tracking performance and convergence rate are increased by 75%,and the air-gap drop and recovery time in anti-disturbance experiment are increased by 80%.In view of the severe operating conditions,time-varying pitching moment and different control structure of multiple actuators of the suspension system of the wind nacelle,it is easy to destroy the synchronization of the two ends of the nacelle,resulting in the loss of the suspension stability of the nacelle in pitch.Firstly,a two-degree-of-freedom operation model of the nacelle in axial direction and pitch was constructed.By introducing the dummy variable of pitch Angle,the two-degree-of-freedom model is transformed into a dynamic model containing the dummy variable U,and then the PPC constraint control of synchronization error transformation variable is designed.In view of the non-singular problem of constraint overstepping easily occurred in traditional PPC control,the fractional order of synchronization error was innovatively introduced into the constrained track,and the range of exponential convergence K in the constrained track was derived by considering the changing speed of the converter current.In addition,in order to improve the tracking strategy accuracy and convergence speed of suspension control,sliding mode adaptive control is introduced into the system to replace discontinuity and weaken system buffeting.Aiming at the interference of uncertain term in the system,the intelligent approximation ability of fuzzy control is used to observe it online.The Lyapunov function containing synchronous sliding mode surface,tracking sliding mode surface and adaptive coefficient is constructed to verify that the above variables can achieve bounded convergence,and then based on the proof of the tracking sliding mode surface,synchronous sliding mode surface bounded convergence characteristics,theoretical analysis,tracking error,reconstruction error and synchronization error bounded convergence.Finally,the simulation results show that the proposed algorithm improves the tracking performance and anti-disturbance performance by 85%/75% respectively.The multi-terminal suspension test platform of wind nacelle was built,and the multi-reference air-gap tracking,pitch interference suppression and axial interference application were studied respectively.The experimental performance was compared with PID control and adaptive compensation control,and the experimental results showed that the strategy proposed in this paper has obvious advantages in tracking performance and anti-disturbance performance.The reference tracking convergence rate is increased by 75% and overshoot is reduced by 90%.When axial interference is applied,the maximum drop of air gap,synchronization error and drop recovery time are reduced by 59%,42%,92%.When pitching interference is applied,the maximum drop of air gap,synchronization error and drop recovery time are reduced by 64%,46%,and 91%.