Abstract
On the basis of the state–space method (SSM), a novel linear mathematical model of the unsteady flow for the tailrace system with an open channel is proposed. This novel model is an elastic linearized model of water hammer. The validity of the model has been verified by several examples of numerical simulation, which are based on a finite difference technique. Then, the complete mathematical model for the hydro-turbine governing system of hydropower station with an open tailrace channel, which is used for simulating the transient process of the hydro-turbine governing system under load disturbance, is established by combining the models of hydro-turbine, generator, governor and open tailrace channel. Finally, according to the complete model, the regulation quality for hydro-turbine governing system with an open tailrace channel under load disturbance is studied, and the effects of open tailrace channel and tailrace surge tank on regulation quality are analyzed. The results indicate that: The open tailrace channel has a strong influence on the regulation quality by observing the water level fluctuations in tailrace surge tank. The surge shows a piecewise periodical change along with the variation in the length of an open channel. The open tailrace channel can be used to improve the regulation quality of hydro-turbine governing system.
Highlights
In the case of a hydropower station either along a long tailrace tunnel or at a low downstream water level, an open channel often follows the tailrace tunnel [1,2]
To verify the accuracy of the space–state equation that describes the unsteady flow in an open channel and a pressurized conduit, comparisons have been made between the results of the three different flow modes by the state–space method (SSM) and the numerical results by the finite difference method (FDM)
These observations further conclude that the SSM applied for onward computation of pipe flow in the case of load disturbances by the boundary conditions is accurate; and it can be reliably applied for the computation and analysis for the regulation quality of hydro-turbine governing system with an open tailrace channel under of load fluctuation
Summary
In the case of a hydropower station either along a long tailrace tunnel or at a low downstream water level, an open channel often follows the tailrace tunnel [1,2]. To evaluate the dynamic performance of the regulation of hydro-turbine governing system in a hydropower station under load disturbance, the whole water and power generation system contain several mathematical sub-models, i.e., the pipeline, the generator, the turbine, and the governor system [15,16,17]. These mathematical models can be combined in the form of a transfer function to develop an integral governing system along with block diagram for transient numerical simulation and/or for system stability analysis. Mathematical Models for the Open Channel and the Pressurized Flow System on the
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