Avoiding Voltage Rise in Distribution Grids Using Energy Storage Systems
Master thesis
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http://hdl.handle.net/11250/2420207Utgivelsesdato
2016Metadata
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- Institutt for elkraftteknikk [2474]
Sammendrag
As a consequence of the combination of increased worldwide energy consumption and rising concerns regarding environment, the amount of renewable electric power plants are rapidly increasing. These are often connected directly to the electric power grid at lower voltage levels than traditional power plants are, causing severe problems regarding power quality and security of supply, in addition to challenges such as voltage rise. Among others, voltage rise is an obstacle for wind farms also in Norway, as such power plants often are connected in weak grids. One solution to avoid voltage rise, is integration of energy storage systems. A range of storage systems are available, and also in this field technology is improving.
In addition to investigate the theory behind voltage rise and possible support provided by storage systems, a simulation model has been in Matlab Simulink build to analyse this. The model consist of a \SI{11}{kV} medium voltage grid with a wind farm connected at it's far end and a storage system possible to connect at several locations. Initial tests only having the wind farm connected, clearly show increase in voltage, the highest impact on buses closest to the wind farm.
The storage system was connected at two different locations, providing the grid with active and reactive power according to it's voltage reference, set equal to nominal voltage. Depending on initial state of the grid and amount of wind farm generation, active power was consumed or delivered by the storage system, lowering or rising voltage. A more even voltage profile was also obtained, proofing the ability of the storage system to both lower a too high voltage but also increase it if initially low.
The storage system was able to best support the grid close to it at both locations tested. However, for improving the overall grid state with the aim of mitigate voltage rise, a location close to the wind farm is the most beneficial. At high voltage levels, change in voltage is most dependent on change in reactive power. To better understand the impact of the storage system, after analysing results it was clear that for lower voltage levels, also active power plays an important role regarding change in voltage.