Dynamic Analysis And Backstepping Sliding Mode Regulator Design Of Pump Turbine Governing System

As the core of pumped storage power station,the pump turbine governing system(PTGS)is a nonlinear time-varying and non-minimum phase complex control system.Due to the strong coupling nonlinear characteristics among hydraulic,mechanical and electrical devices in PTGS,and frequently changes of pump turbine working status,the safe and stable operation of hydropower unit is seriously threatened.It is necessary to study the dynamic characteristics of PTGS,and establish a mathematical model that meets the requirements of different operating conditions while controlling the unstable factors in the system.This paper establishes a more realistic nonlinear mathematical model by in-depth analysis of the operational characteristics of PTGS from the measured data of a pumped storage power station in China,and then the backstepping sliding mode control strategy is adopted to improve the robustness of the regulation system and ensure the reliable and efficient operation of pumped storage power station.Summarize the whole research process of the paper,the main contents are as follows:(1)Firstly,a seventh-order nonlinear mathematical model of PTGS is established,it is divided into four subsystems,namely the water diversion pipeline subsystem(considering the surge tank effect and elastic water hammer effect),the pump turbine subsystem,the motor generator subsystem and the governor subsystem.It gives a basis for the following study of this paper.(2)Secondly,in order to study and analyze the dynamic response characteristics of the power grid-connected process,some nonlinear dynamic behavior indicators of the system,such as bifurcation plot,time domain diagram and phase track orbits are presented.The adjustment range of elastic water hammer time constant and guide vane opening is obtained,and then the sliding mode controller is designed according to the unstable running problem in the system.The results show that compared with the PID controller commonly used in PTGS,the sliding mode controller has a shorter rising time,smaller steady-state error and better tracking performance.(3)Finally,in order to further improve the response speed of the controller,the backstepping sliding mode controller is designed based on the idea of backstepping control method while ensuring the strong robustness of regulating system under grid-connected condition.In order to avoid the expansion of the number of backstepping terms,the dynamic surface control technique is introduced,and the adaptive control rate is designed to eliminate the real-time disturbance of uncertainties on the system.The simulation results show that the backstepping sliding mode regulator has better performance in response speed,anti-interference,robustness and convergence of errors.