Research On Setting Condition Of Surge Chamber And Operation Control Of The Hydropower Station

With the development of hydropower resources in our state, some huge or large hydropower stations are programming, designing or constructing. These hydropower stations play an important role in the grid system because they are backbone power supplies of the grid system, and also the main governor of dynamic load in the grid system. With the increase of the proportion of hydropower, the peak modulation and frequency modulation task becomes heavier, and this makes the requirement of operation stability and governing quality of the hydropower projects stricter. So operation stability and governing quality are being paid more and more attentions. The setting of surge chamber, the transient process of different operation conditions and control strategy are all important factors affecting the safety operation of hydropower stations. Based on previous research, this dissertation deeply discusses some new problems in actual engineering and theory. The following achievements have been represented in the dissertation.1. Research on setting condition of surge chamber in hydropower stations(1) Research on setting condition of tailrace surge chamber based on regulation guaranteed parametersTaking draft tube vacuum and rising ratio of unit speed into consideration, the setting condition of tailrace surge chamber in conventional hydropower stations is derived, which is also called as the critical length of tailrace conduit. Further more, the calculation formula of allowable [Tw] of pressure tailrace conduit is derived. The setting condition of downstream surge chamber of pumped storage power stations is derived. First, some assumptions which are in accordance with unit characteristics are got by numerical simulation; second, the calculation formula of discharge diversification time Ts in the period of rapid decreasing which affects the minimum pressure of draft tube is derived; at last, the calculation formula of the critical length of tailrace conduit in pumped storage power stations is derived. Finally, through engineering projects, the analysis is carried out to contrast with other setting conditions, and the Japan Empirical Formula is amended. (2) Research on setting condition of surge chamber based on operation stability.With the assumption of ideal turbine model, the stability boundary lines of rigid water hammer model and elastic one are simulated, then the discriminant for setting condition of surge chamber based on rigid water hammer model is obtained. Then this discriminant is comparatively analyzed against the discriminant proposed by XingLin Dong (1980) and the discriminant graph in specifications for design of surge chamber of hydropower stations, and the function expressions of the two curves in the discriminant graph are derived. The affects of governor parameters to stability and stability margin of the system are also analyzed.(3) Research on setting condition of surge chamber based on governing quality of hydropower station.With the assumption of the rigid water hammer, the equation of unit speed fluctuation based on optimal governing quality and formulas for calculating the characteristic parameters of speed fluctuation are derived, and then the discriminant for setting condition of surge chamber based on the governing quality is obtained. The affects of elastic water hammer and the characteristics of hydraulic turbine to governing quality are analyzed, and corresponding revise for setting condition of surge chamber after taking the elasticity of water into account is made against those hydropower stations in which Tr/Tw<1.0. Finally, with example of engineering projects, the conclusion is got that:for high head power stations or middle ones, the allowable Tw is determined by regulation guaranteed parameters, while it is determined by operation stability for low head hydropower station.2. Research on the transient process of hydropower stationsTaking nonlinear characteristics of hydraulic turbine and elastic water hammer of pressure water supply conduit into account, a whole nonlinear dynamical model of condition conversion process of hydropower station is developed, the model is accurate enough to represent and simulate each transient process of the hydropower stations. In addition, the dissertation takes a hydropower station as an engineering case to simulate the transient processes of hydro-generator units'start-up, load variation, full load rejection and emergency stop.3. Research on nonlinear control strategy of hydropower stations based on differential geometry theoryOn the basis of the nonlinear mathematic models with the assumption of the non-elastic water hammer for small disturbance and hydraulic interference transient process in hydropower station, a design principle of output regulation function is suggested by nonlinear differential geometric control theory, which can make the non-minimum phase systems be linearized accurately to avoid the stability problem of zero-dynamics. From this design principle, nonlinear control strategies of transient process in hydropower station are constructed, and then comparative analysis of the nonlinear strategies against the conventional control laws is carried out through the example of engineering projects.