Hydraulic transients in hydropower plant impact on power system dynamic stability

Abstract

Futaleufú hydropower plant has 4 Francis turbines rated 118 MW and it is connected to the power system by 2x330 kV lines. Studies carried out in the past did not predict the instable operation of Futaleufú after a 330 kV line fault, when some Futaleufú turbines are automatically disconnected as a consequence of the faulted line tripping. Load rejection caused by disconnected turbines generate large transients in the remaining turbines due to hydraulic coupling through the common conduits. Then, to improve related models and, therefore, to improve studies results of such a line fault it was necessary to make several tests in Futaleufú power plant. Finally, these models were used to conduct studies to design a new automatism, like the gate partial closing of the remaining turbines, to obtain a dynamically stable operation of Futaleufú after the disconnection by fault of a line of 330 kilovolts.

Dynamics Analysis for Hydroturbine Regulating System Based on Matrix Model

“…It can only obtain opening and unit speed and × corresponding points of unit flow rate and unit torque as the input of the arithmetic. In order to improve the flexibility of access points, the method is improved by taking formula (2) directly into formula (1). A matrix equation of ( × ) × ( × ) is needed to obtain all the coefficients.…”

“…As an important part of power system operation, the accuracy of the model is of great significance to the stability analysis of power system [1,2]. In the simulation of power system, the mathematical model of hydraulic turbine and governing system is often simplified to improve the calculation speed [3,4], such as the use of linear model.…”

A review on electromechanical equipment applicable to small hydropower plants

“…To assess the power system stability, Agüero et al . emphasized on the importance of using more accurate models as a necessary condition to obtain more accurate results. Presented models were used to conduct system studies for redefining automatic actions used to obtain a dynamically stable operation of the power system after a fault in the 330 kV transmission systems.…”

Improved nonlinear turbine-governor model and parameter assessment for a large hydropower plant

“…Turbine‐governor system is an important part of the hydropower unit. The accuracy of the mathematical model and its parameters is one of the main influencing factors in power system operation and power grid security . However, issues still must be resolved, for the static characteristic of Francis turbine mechanical power and the characteristic of the guide vane opening are obvious nonlinear under a certain water head, which has a great influence on the simulation precision .…”

“…The accuracy of the mathematical model and its parameters is one of the main influencing factors in power system operation and power grid security. 1,2 However, issues still must be resolved, for the static characteristic of Francis turbine mechanical power and the characteristic of the guide vane opening are obvious List of symbols and abbreviations: K p , K i , and K d , proportional, integral, and differential gain; f s and f g , system frequency and unit frequency; P GV and y nld , given load opening and no-load vane opening; b p , difference coefficient; V ELopen and V ELclose , rapid opening and closing limits; P max and P min , maximum and minimum guide vane opening; T y , main servomotor time constant; V ELclose1 and V ELclose2 , different rapid opening and closing limits; T 1 , delay link time constant; T 2 , time constant of vane opening feedback loop; y 1 , guide vane section closing point; T w , inertia time constant for water diversion system; T r , pipeline reflection time; A t , proportionality coefficient; q NL , no-load water flow; a 0 , a 1 , …, and a n , fitting coefficients; H 0 , static head; P ref , P e , and P m , given power value, turbine power, and mechanical power; y ref and y, given vane opening and guide vane opening; y PID , output of PID microcomputer regulator; h and q, turbine working head and turbine discharge nonlinear under a certain water head, 3 which has a great influence on the simulation precision. 4 The Hamiltonian modeling was established to describe dynamic behaviors of the hydro-turbine governing system.…”