Study On Predictive Method Of Hydro-turbine Gorverning System

Hydraulic power is the most important power supply source,which offers the one fifth of the global source of energy as electricity for mankind.Not only does it play important roles in the peak and frequency regulations,but also it can help to keep the security and stability of the frequency and voltage and keep the loads demands balanced of the power grid system.Moreover,hydropower units are the main equipments of the hydropower plants,and they are a complex nonlinear system combining the hydraulic power,the machine and the electric power,which matters a safe,efficient,stable running sate of the hydropower plants and the power grid system.Considering the complex characteristics,varieties of the disturbances and uncertainties of the system,the conventional PID control method can't obtain satisfactory control performance because it neglects the nonlinear characteristics of the hydro-turbine governing system(HTGS).The predictive control strategies can solve the nonlinear control problems,for they have the advantages of low requirements of the model,the strong inclusiveness and good applicability for linear or strong nonlinear systems.Based on this,the model predictive control theory is introduced into the control method of the HTGS to design the HTGS predictive controller.Also,the stability of the overall system is proved with the discrete Lyapunov function.Moreover,the effects of the system variables on the control performances are discussed in detail.In addition,to show the control performance of the nonlinear predictive control,the abnormal operating states are considered,such as disturbances and the model mismatch problems and so on.Finally,the great control performance is showed comparing with the conventional PID control method.AS for the same HTGS,a nonlinear model predictive control strategy based on the Takagi-Sugeno(T-S)fuzzy model of the HTGS.First,the HTGS is represented by a generalized T-S fuzzy model,which has very high fuzzy approximation accuracy and the system parameters of the fuzzy model are also given.Furthermore,the model predictive control for the T-S fuzzy model is presented,where the stability of the overall system is proved with the discrete Lyapunov function.Moreover,another nonlinear PID control based on the T-S fuzzy model of the HTGS is presented.Finally,the proof of efficiency of the proposed nonlinear fuzzy model predictive control and the numerical experiments are finally presented including a comparison with the existed model predictive control and the nonlinear fuzzy PID control.Considering the large online calculation,the complex control theory and the bad real-time performance of the model predictive control,a new control approach on a nonlinear HTGS combining the predictive functional control(PFC)and the T-S fuzzy model is proposed combining the nonlinear fuzzy modeling and predictive functional control method.To validate the robustness of the controller,the performances in terms of tracking,disturbances,model mismatches and output constraints are studied in detail.Finally,the better control performance is showed comparing with the conventional PID control method.Based on the proposed control strategies,the better control performance of the HTGS is studied by analyzing the transient process performance(the overshoot,adjusting time and the number of oscillations)and the requirements of the computer performance.