Research On Nonlinear Fault-tolerant Control Of Time-delay Hydraulic Turbine Governing System

The hydraulic turbine governing system(HTGS)is an important part of the hydropower station system.It is responsible for adjusting the frequency and speed of the unit,adjusting the load distribution,smoothly starting and stopping,and synchronized grid connection.The stability and effective control of the HTGS affects the safe and stable operation of the entire hydropower station and even the power grid system.This paper applies the fault-tolerant control strategy to the HTGS.Combining fault detection theory,fault estimator design and finite time theory,the article studies the stability of the HTGS under dead zone or fault conditions and the characteristics of various state variables.The main research contents are summarized as follows:First,based on the fault detection,the observer is designed to study the stability and fault tolerance of the fault-tolerant control of the HTGS under the condition of actuator or sensor fault.Based on the six-dimensional model of the nonlinear HTGS,combined with the fault detection theorem,a fault-tolerant control algorithm for the HTGS is designed.An observer is proposed to effectively monitor system faults,a closed-loop system state feedback faulttolerant controller is designed,and integrity verification and stability analysis are performed.Numerical simulation results show that the system can reach stability within 2 s under the action of the controller,and exhibits good regulation performance after being impacted by faults.Secondly,a finite-time fault estimator is designed to monitor the fault in real time,and the control performance of the finite-time fault-tolerant control method of the fractional-order nonlinear HTGS is analyzed.From integer-order mathematical models and basic fault-tolerant control methods,transition to a fractional-order model that can more reflect actual working conditions and a fractional-order fault-tolerant control technology that can achieve finite time convergence.A sliding mode surface and a finite-time fault-tolerant controller with a smooth and bounded arctangent function are designed to ensure the rapid convergence and stable operation of the HTGS.Analyze common actuator faults and divide the faults into lock-inplace,constant-gain fault,constant-deviation fault,and multiple faults.To verify the feasibility of the control method for different fault models,and whether the system can still maintain acceptable performance indicators under fault conditions.Finally,on the basis of the above research,the delay effect of the hydraulic servo system is considered,and the system’s stability under the fractional-order finite-time fault-tolerant control algorithm is further explored for the disturbances,actuator faults and nonlinear dead zones existing in the fractional-order system.A fractional-order non-singular terminal sliding mode fault-tolerant controller is designed,the fault estimator is directly applied to the faulttolerant controller,and the control examples under the dead zone and different actuator fault models are realized.Numerical simulation analysis shows that the finite-time fault-tolerant control of the fractional-order HTGS has fast transient response and good fault-tolerant characteristics,which provides an effective fault-tolerant mechanism for the safe and stable operation of hydropower stations.