Integral Model And Stability Of Hydraulic Turbine Governing System Coupling Shaft System

Hydraulic turbine governing system is the typically nonlinear water-mechanical-electrical coupling system,which consists of the pressure diversion system,hydro-turbine,generator,and governor.Compared with other intermittent energy sources(wind,solar and tidal energy,etc.),the system not only converts hydroenergy into electrical energy,but also regulates grid load fluctuations and ensures power quality and safety.Efficiency characteristics and stability issues are the two main reasons affecting the operating characteristics of hydropower stations.Among them,the efficiency characteristics can reflect the water energy utilization rate,and the stability of the system to some extent.The vibration problem is a direct reflection of the stability of the hydropower station,which is closelyrelated to the working life of the unit and the safety of the hydropower station.In recent years,with the units of large capacity and high-head are put into operation,the highi-efficiency operation and the transient stability of hydropower systems are becoming more and more prominent.It is necessary to explore the stochastic dynamics modeling theory and efficiency characteristics of hydroelectric generator systems from the perspective of energy flow.Moreover,a transient model of hydraulic turbine governing system coupling with the shafting system is established,and the vibration characteristics and influencing factors of the unit during transient process is investigated.Summarizing the entire research process,the main content of this paper is:(1)Dynamic modeling and energy distribution analysis in a hydroelectric generating system considering the stochastic turbine flow.From the perspective of energy flow,considering the stochastic characteristics of turbine flow under the action of hydraulic hammer,a stochastic dynamic model model reflecting the energy characteristics of hydro-generator system is established.The Chebyshev polynomial approximation theory is used to simplify the stochastic system into an equivalent deterministic system.The validity of the model is ver ified through the comparative analysis of the actual operation data of a domestic power station,In addition,the time domain and bifurcation diagrams of system flow,vane opening and efficiency under the influence of random flow are obtained by numerical simulation based on the stochastic dynamics theory.Finally,the energy loss distribution and efficiency characteristics of hydro-generator system under random disturbance are analyzed,and the variation law of energy flow is summarized.(2)Transient modeling of coupled shaft system of hydro-turbine regulation system.A transient model of the water diversion system is established based on the characteristic line method.From the perspective of the force of the unit shaft system,the shafting model of the hydroelectric generating set is obtained.The coupling relationship between the hydraulic turbine governing system and the unit shafting system is analyzed in detail.Through the coupling relationship between the pressure diversion system and the shafting system,the nonlinear coupling between the hydraulic turbine governing system and the unit shafting is realized,and an overall model of coupled shafting system for hydraulic turbine governing system for transient analysis is established.Finally,the rationality of the coupled transient model is verified based on the actual variable load vibration test of hydropower station,(3)Vibration characteristics of a hydroelectric generating system during the load rejection process.The theoretical analysis and numerical simulation method are used to analyze the vibration characteristics and influencing factors of the unit shafting during the load-shedding transition process based on the above model,and the influence of multi-vibration coupling on the system stability is discussed.Next,the effects of several typical vibration source parameters(e.g.bearing stiffness,blade displacement coefficient,mass and mass eccentricity)on the transient vibration response of the unit are analyzed,and proposes measures to improve the abnormal vibration of the unit,and provides a theoretical reference for the design and operation of the shafting.