Modeling for Control of Run-of-River Power Plant Grnvollfoss

Abstract

Design of optimal operation and control of a run-of-river hydro power plant depends on good models for the elements of the plant. River reaches are often considered to be shallow channels with free surface flow. A typical model for such reaches thus use the Saint Venant model, which is a 1D model based on the mass and momentum balances. This combination of free surface and momentum balance makes the problem numerically challenging to solve. Here, the finite volume method with staggered grid is used to illustrate the dynamics of the river upstream from the Grønvollfoss run-of-river power plant in Telemark, Norway, operated by Skagerak Energi. A model of the same river in the Grønvollfoss power plant has been studied previously, but here the geometry of the river is changed due to new information from Skagerak Energi. The numerical scheme for solving the model has been further developed. In addition, the behavior of the dynamic model is compared to data from experiments, carried out on the Grønvollfoss run-of-river power plant. The essence of the experiments is to consider the time taken from an increase in the input volumetric flow, to a measured change in level in front of the dam at Grønvollfoss. The model is manually tuned by changing the Strickler friction factor, the river length and the type of river slope/width (constant/varying) in order to fit the water level ahead of the Grønvollfoss dam from experimental data. Least squares model fitting is also used for the model with the constant slope and width of the river and this model shows good fitting after the manual tuning. The results of the improved model (numerically, tuned to experiments), is a model that can be further used for control synthesis and analysis.

Model based control for run-of-river system. Part 1: Model implementation and tuning

“…As described in Vytvytskyi et al (2015); Vytvytskyi (2015), this type of hydropower plant has a high volumetric flow rate, which passes through the turbine and spins the rotor. The turbine transfers the kinetic energy from water to rotational mechanical power, which will then be transferred to electric power in the generator.…”

“…The following information about the system was provided by Skagerak Energi AS or was found from maps on the Internet (Vytvytskyi et al, 2015;Vytvytskyi, 2015). All of the provided parameters are approximations.…”

“…In this work, the finite volume method with staggered grid (Vytvytskyi et al, 2015;Vytvytskyi, 2015;LeVeque, 2002) is compared with the Kurganov-Petrova central upwind scheme (Sharma, 2015;Kurganov and Petrova, 2007), and the chosen scheme compared to experiments on the system with the model tuned by changing the river bed (slope), the friction factor, the width and the height drop of the river. The paper is structured as follows: Section 2 consists of a system description of the run-of-river power plant together with a description of the experiment on the power plant.…”

“…In previous work (Vytvytskyi et al, 2015;Vytvytskyi, 2015), a model for the Grønvollfoss power plant was developed using the Saint Venant equations, was discretized using the staggered grid scheme, and was tuned to experiments. A case study of the run-of-river power plant using the Kurganov-Petrova second order central upwind scheme is described in Sharma (2015), with more details about the development of this scheme in Kurganov and Petrova (2007).…”

“…Small hydropower plants is a generic term for plants that have small production capacity. There are in total operating over 1100 such smaller hydropower plants in Norway today and production from these accounts for about 7% of the total hydropower production (Vytvytskyi et al, 2015). Skagerak Energi is operating two run-of-river hydro power plants in river Tinnelva flowing out of lake Tinnsjøen in Eastern Telemark.…”