Research On Sliding Mode Robust Control Of Hydro Turbine Governing System Based On Nonlinear Generalized Time-delay Model

The accurate modeling of hydro turbine governing system is the basis for the transient process research and controller optimization design,and it has very important theoretical significance and engineering value for the safe and efficient operation of hydropower stations and the improvement of power system stability.Many large and medium-sized hydropower stations which have been built or built in China at present,have the characteristics of large installed capacity and long water crossing pipeline,and their water turbine regulation system presents more obvious nonlinear characteristics and delay characteristics Comparing with conventional hydropower stations.However,the simplified linear constant model based on six transfer coefficient and elastic water hammer theory is widely used in the model of hydraulic turbine governing system for theoretical analysis and it can't well describe the precise characteristics of the actual system in the process of large wave transition and under different working conditions.Therefore,it is necessary to research the precise modeling method of the hydraulic turbine regulating system,so as to improve the accuracy of the calculation and the effectiveness of the research on the control strategy,and provide a guarantee for the safe and economic operation of the hydropower station and the power system.Aiming at the precise modeling of hydraulic turbine regulating system,the nonlinear spatial surface model of hydraulic turbine based on double three B spline and the time-delay model of water system based on basic water hammer equation are emphatically studied.The nonlinear generalized delay model of hydraulic turbine regulating system is built by combining the mathematical model of electrical and mechanical part.It laid the foundation for the accurate calculation of hydraulic turbine transient process and the research of control strategy.The nonlinear generalized delay model of hydraulic turbine regulation system is essentially is a set of differential algebraic equations containing water pressure delay term and flow delay term,since the boundary condition of time delay is usually known,we can convert the transition process calculation of the hydraulic turbine unit into the numerical solution of the dynamic differential algebraic equations.The numerical solution for the index-1 type differential algebraic equations problem of the single water pipe water turbine regulating system can be divided into the regularization method,the iterative method and Matlab ODE15 s toolbox.The calculation principle and the solution procedure of the three methods are elaborated in this paper.The simulation test is carried out in the typical working condition and the results show that the iterative method and the ODE15 s toolbox have very high calculation accuracy and they are accurate and effective method for solving the transition process of hydraulic turbine.The robust control method with sliding mode of hydro turbine governing system is proposed on the basis of constructing uncertain discrete generalized delay models satisfying matching conditions.In view of the parameter perturbation and delay characteristics of the system,an integral switching surface which includes the system uncertainty and the lag term is constructed.On this basis,the system convergence law is designed according to the convergence criterion of the sliding mode control system,the sliding mode controller is derived and designed by using the characteristic of uncertain estimation of discrete system.In order to further improve the robustness and dynamic performance of the sliding mode controller,the delay dependent robust stability condition of the system is derived based on the linear matrix inequality theory and the robust stability region of the turbine regulation system is obtained.The sliding mode control parameters satisfying the robust stability conditions are optimized by using the gravitational search algorithm.Then,the sliding mode robust optimal controller design method for hydro turbine governing system based on uncertain singular time delay model is established.The simulation test of a test unit shows that the sliding mode robust optimization control method proposed in this paper can make the system get good dynamic quality and have strong robustness for the change of system condition.