Battery Sizing and Placement in the Low Voltage Grid including Photovoltaics
Abstract: Installations of photovoltaic power production increases each year. This can have a negative consequence on the distribution grid where the voltage can increase. The electric distribution companies in Sweden have a responsibility in keeping the grid at certain voltages, and have to reinforce the grid if these voltages are outside these levels. This Master's Thesis investigates the difference in strengthening the grid with help of cables or with help of batteries, especially the economic differences between the two and in which cases they might be viable, both today and in the future. A real case in a low distribution grid, where photovoltaic production was too large will be used as basis of the thesis. In this case, the problematic part of the grid with most production was moved to a network station close by which lead to a significant drop in voltages on the first grid. To evaluate the different solutions a simulation tool developed previously is further built upon, to be able to create simulations of the grid investigated. It is also possible to test replacing or strengthening cables with this tool. An optimisation tool is then created, that is used to test where batteries can be placed and how large they have to be to keep the voltages and currents within set ranges. From the results, the most significant conclusion is that batteries are not yet viable as a replacement for grid reinforcements in the base case evaluated. Today this is mostly due to the steep prices of batteries, and long life-lengths of cables where they can be used for significantly longer than batteries as grid reinforcements. However, in the future, there are situations where batteries may be economically more viable. There is also a portability aspect in batteries, where batteries could be used as a temporary solution where it may not be possible to install cable reinforcements immediately. Lastly, the optimal placement of batteries was established to be as close to the problem zone, i.e. the photovoltaic power production as possible. This means that with growing popularity of stationary batteries at home and electric vehicles, these types of solutions could possibly be used in the future.
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