Finite-time Synchronous Control Of Wind Turbine Nacelle Suspension Syste

In this paper,the wind cabin suspension system with multi-suspension converter is taken as the research object,and the research on multi-terminal suspension air gap synchronization and current synchronization control of each end converter of wind turbine is mainly carried out.The two-degree-of-freedom suspension model of the wind nacelle is constructed,and the floating converter model under multiple interferences such as line impedance mismatch between multiple converters,differences in device structural parameters,load uncertainty caused by load switching and actuator faults are constructed.The combination of fractional order adaptation,finite-time interference observer,finite-time terminal sliding mode control and multi-agent synchronous control technology comprehensively improves the transient performance of wind nacelle suspension and pitch suppression.From the interference characteristic analysis,mechanism modeling,control strategy design,stability proof and simulation verification,etc.the comprehensive research is carried out,and finally based on the built experimental platform,the current sharing performance of multiple converters and the experimental performance of cabin levitation under different control strategies under multiple working conditions are compared,which verifies the effectiveness of the control strategy proposed in this paper.Firstly,the time-varying wind disturbance characteristics of the wind nacelle in harsh environments are analyzed,and the dynamic model of axial moment and pitch moment subjected to the nacelle is constructed based on the leaf theory.In view of the fact that time-varying pitch torque is very easy to cause nacelle pitch and axial oscillation,the suspension windings of the cabin blade side and tail side are reasonably divided,and the dynamic model of wind nacelle magnetic levitation system with axial and pitch two degrees of freedom is constructed,and the two-degree-of-freedom cabin suspension model with severe coupling and nonlinearity is linearized,and a linearized suspension control model for the study of suspension control strategy at both ends of the nacelle is formed.Then,based on the power flow analysis theory of the power closed system,the in-depth analysis of various factors such as line impedance mismatch,device structure parameter difference and actuator aging difference of parallel suspension converter is analyzed,and a parallel system model of nacelle suspension converter that comprehensively considers various uncertainties is constructed.Aiming at the current synchronous control problem of nacelle suspension converter,a fractional integral finite time terminal sliding mode control method is proposed to improve the tracking speed and control accuracy of the suspension current loop.For the uncertain interference such as mismatched line impedance,device structure parameter difference,load uncertainty and actuator aging between multiple converters,a mismatched line impedance differentiator,a finite time load observer,and a fractional integral finite time terminal sliding mode controller for current synchronization and tracking are designed.The Lyapunov function is constructed to verify that both the current tracking error and the synchronization error can converge to the stable domain in a finite time,and the convergence domain size can be optimized and adjusted by the controller parameters.Finally,a double buck parallel circuit experimental platform was built,and the performance of other control strategies was compared with other control strategies under the experimental conditions of load switching,line impedance mismatch and actuator aging,and it was found that the control strategy proposed in this paper realized current synchronization(synchronization error 0.02 A and convergence time 0.002s)under load switching,and the performance of the two was improved by 80%/83%,respectively.Under the experimental conditions of increasing bad line impedance mismatch and aging actuator,current synchronization can still be achieved within 0.006 s,and the synchronization error is 0.2A and 0.1A,respectively,and the synchronization error and convergence speed are increased by more than 80% compared with other control algorithms.It is effectively verified that the proposed algorithm has obvious control effect in terms of current synchronization performance and transient performance improvement.Aiming at the problem of synchronous control of suspended air gap in wind cabin suspension system,a cabin finite time adaptive terminal sliding mode control method with singularity elimination is proposed,which weakens sliding mode jitter and greatly improves the cabin suspension tracking and pitch suppression performance.The adaptive uncertainty term control law based on the fractional order terminal sliding mode surface is designed,and the axial and pitch interference and uncertain parameters are obtained online.A finite time state observer is designed to observe the pitch speed and suspension velocity online that are difficult to obtain.Based on the constructed Lyapunov function with axial and pitch sliding surface and uncertainty term approximation,it is verified that the tracking error,approximation error and uncertainty term approximation error can converge to the set convergence domain in a limited time,and the convergence domain size can be optimized and adjusted by controller parameters.Finally,the experimental platform of wind cabin suspension system is built,and the experimental performance of other control strategies is compared with other control strategies under the experimental working conditions of variable reference air gap tracking,pitch interference and axial interference,and it is found that the control strategy proposed in this paper has obvious advantages in suspension tracking,synchronous control and interference suppression,and the synchronization error and convergence time of cabin suspension start when variable reference air gap tracking is only0.05mm/1.5s,and the performance is improved by 75%/95% respectively.When pitch interference is applied,the maximum air gap drop is only 0.25 mm,the performance is increased by 75%,and0.25 mm is maintained,and the synchronization error performance is increased by 92%,which effectively solves the problem of floating air gap synchronous control of wind cabin suspension system,and verifies the effectiveness of the cabin suspension synchronous control strategy proposed in this paper.