Study On The Regulating Control Of Hydraulic Transients In Pumped Storage Plants

The construction of pumped storage plants began as early as about 100 years ago, and with the development of society and economy and the higher life standard, the difference between the peak and valley daily load of electric system has been become larger and larger. It seems to become more and more clear that pumped storage plants have many roles and advantages in electric system, such as peak-clipping, frequency and phase modulation, improving quality, flexibility and reliability. So far, the development of pumped storage plants has entered a new stage: the total installed capacity of the plants has increased by 10% annually, with the trend of great unit capacity and high head. It is very necessary to have the study on the characteristics of the transients in pumped storage plants and to find the ways to control the transients reliably for improving design, reducing investment and ensuring the plants working safely and efficiently. Due to the study on the regulating control of the transients in hydraulic pressure system is on primary stage so far, especially the study on it in the whole uncontrollable complex system is just beginning, it is very important to solve the problems for the safeness, reliability and flexibility of pumped storage plants.In this thesis, the regulating control of the hydraulic transients in pumped storage plants is studied, and the models of the converse problem for regulating control in specified time and with pressure constraint are given. The theory of valve stroking is applied to the hydraulic pipe-turbine system first time, and based on considering systematically for the two inverse problems of the regulating control the mathematical models and the numerical methods for valve stroking in specified time and with pressure constraint are raised foe the complex system in pumped storage plants. To counter the whole uncontrollable system with well in pumped storage plants, the mathematical models and their numerical method for hydraulic transients are put forward by the new method based on the fundamental tenet of valve stroking. At the same time, practical examples are studied with the results been discussed. The main contents are as follows:1. The development of pumped storage plants home & abroad and the study on the characteristics of hydraulic transients in reversible turbine system and the models of regulating control are summarized, with the mathematical models of the inverse problems of regulating control in specified time and with pressure constraint being obtained and the methods to solve these problems being analyzed. The theory of valve stroking and its apply and the optimization of the moving of guide vanes for the hydraulic transient in hydraulic turbine systems as well as the transformation methods for the complete characteristic curves of reversible pump turbines are discussed.2. Based on the theory of valve stroking, the mathematical models and their numerical methods of valve stroking in specified time and with pressure constraint are proposed for the hydraulic pipe-turbine system in pumped storage plants and the models and their solving methods are also posed for the complex hydraulic pipe-turbine systems with the practical programmes in the conditions of hydraulic transients been proposed. At the same time, the methods of regulating control for the transients of hydraulic turbines are set up under the conditions of the whole uncontrollable systems, and the mathematical models and their numerical methods are established for the pumped storage plants. Therefore, the key problem to use the method of valve stroking for the whole uncontrollable system is solved, and an efficient numerical methods is provided for the regulating control of the transients in pumped storage plants.3. It is very important to deal with the complete characteristic curves of reversible pump turbines in the study of the hydraulic transients in pumped storage plants. Because there are some disadvantages and the expects to be perfected in the existing methods now, based on the Suter curves, the complete characteristic curves of reversible pump turbine are transformed to the functions of the relative flow angle x and the opening of guide vanes, and the curve surface equations describing the complete characteristic curves are obtained by using the mathematical model of least square surface fitting and computer simulation technology. The method of describing the curve surface by layer is also raised for imitating the completing characteristic curves with the practical case been calculated.4. Taking the turbine-pipe system in YiXing Pumped Storage Plant as a practical case and using the method raised by this paper for the whole uncontrollable complex hydraulic pipe-turbine systems, the numerical calculations of regulating control in specified time and with pressure constraint are taken place for the transients of normal load changing and load losing in turbine working state and power losing in pump working state ,and with the changing laws of discharge and head in the turbines are obtained, the moving laws of guide vanes are gotten. Finally the results are analyzed and discussed.5. Because the regulating control of transients in hydraulic pipe- turbine systems relates to many problems both of theory and practical use, especially for the inverse problem of whole uncontrollable systems, the study is in primary stage now and the theory system and the mathematic model are need to be filled up and perfected, and the scope of use has to be enlarged. In this paper, it is forecasted to study fully and systematically on the models of regulating control of the hydraulic transients inpumped storage plants.