Research on hydraulic–electric interference and optimisation of multi‐turbine hydropower system based on the dual control mode

Abstract

Aiming at the complex hydraulic and electrical interference, as well as the stability of the hydropower plant that one diversion tunnel supplies water to multiple turbines, a high-order coupling model based on the dual control mode of the speed and excitation regulation is developed. Some scenarios, involving the hydraulic interference law, the effect of partial load rejection on the stability and dynamic characteristics of the units, and the optimisation of the power system stabiliser (PSS), are investigated. It is found that the change of the guide vane opening (or power) of one of the units causes the water hammer in its spiral case and penstock, and the water level fluctuation in the surge chamber. Besides, hydraulic disturbances suffered by other units are mainly caused by water level fluctuation in the surge chamber, rather than directly from the water hammer. The results demonstrate that the unit wiring of the generator and transformer is better than the expansion unit wiring in terms of the dynamic characteristics. In addition, PSS not only can suppress low-frequency oscillations, but also affect the hydraulic transition process, and the improved PSS2B-proportional-integral-derivative can increase the positive damping, and more effective in suppressing system oscillations.