Modelling of Water Levels in a Reservoir using Modelica

Abstract

The regulation of hydro power plants is influenced by amongst others reservoir capacity and the knowledge about how it is influenced by changes in in-and outflow. The hydro power reservoir Aurdalsfjord has a small capacity compared to the inflow, a narrowing between inflow in the north and outflow in the south and has implemented strict governmental restriction. The paper will present a reservoir model that was developed in order to investigate the water flow and water level conditions in Aurdalsfjord. The water level in each cell is described with a mass balance, while the flow between two cells is described with a momentum balance. The balance equations are formulated as DAEs. The model is developed in Modelica which allows it to be used in connection with models of a wide variety of other components that are present in a hydro power system. The model will be integrated in the open-source hydro power library OpenHPL developed at USN. The Modelica model shows promising results. For Aurdalsfjord it needed to be adjusted with non-physical parameters. The reservoir model should be implemented for a less complex shaped reservoir in order to see if the challenges are related to the Modelica implementation or Aurdalsfjords shape.