WATER-LEVEL CONTROL IN HYDROPOWER PLANTS

The stability of a controller used to control the water level in the forebay or afterbay of a hydroelectric power plant is investigated by using the Routh-Hurwitz stability criterion. It is shown how the characteristics of the controller influences the required size of the forebay in a plant with a surge tank, while there are no restrictions regarding stability for a plant without a surge tank. Computer simulations of the water-level oscillations in a hydropower plant including all major nonlinearities verify these conclusions and show that the operation with small flows is critical as far as the stability is concerned. Guidelines are given to select the dimensions of the forebay for preliminary design. A practical example illustrates the application of this type of control system.