The objective of this bachelor's thesis was to get knowledge concerning the trend of small scale hydropower plants and the possibility according the present legislation to use small scale hydropower as energy source in Sweden. The result aims also to conclude if it is possible to get permission for small scale hydropower stations at the river Lyckebyån.   To achieve this, ten legal cases where five of them have been permitted and five of them has been denied license have been examined. These cases were dated between 2010-2016. These have been analyzed from given questions. They may describe the trend of small scale hydropower in Sweden. To examine the cases at Lyckebyån different sources were used, such as literature studies, interviews and by using information from different databases.   The results shows that it is possible to get permission for small scale hydropower production in Sweden today, but it is a complicated process and the result of the probation depends on many factors. The legislation sets high standards and there exist conflicting interests which are against small scale hydropower stations due to their effects on biodiversity. There are both positive and negative environmental consequences of hydropower production at Lyckebyån. However, there are no evident obstacles for permission in Lyckebyån. / Uppsatsens mål var att få en inblick i hur trenden ser ut avseende småskalig vattenkraft och om det med dagens lagstiftning är möjligt att använda småskalig vattenkraft som energikälla i Sverige. Resultatet förväntades också ge en bild av huruvida det är möjligt att få tillstånd eller inte för ett småskaligt vattenkraftverk i Lyckebyån.   För att komma fram till resultatet har tio domstolsbeslut som är daterade mellan 2010 och 2016 använts varav fem har erhållit tillstånd och fem har fått avslag. Dessa har analyserats utifrån bestämda frågeställningar. Domarna ger en beskrivning av trenden avseende småskalig vattenkraft i Sverige. För att undersöka fallet i Lyckebyån har annat material i form av litteratur, muntliga källor och databaser använts.   Resultatet visar att det är möjligt att få tillstånd för småskalig vattenkraft idag men att det är en krävande process som beror på flera faktorer. Lagstiftningen ställer höga krav och det finns andra intressen som är emot den småskaliga vattenkraften på grund av dess påverkan på den biologiska mångfalden. Det finns både positiva och negativa miljökonsekvenser till följd av ett vattenkraftverk i Lyckebyån. Det finns inga självklara hinder för att ett tillstånd ska beviljas i Lyckebyån.

This master thesis examines technical requirements for small hydro power plants (HPP) to operate proximate parts of the power grid in island mode. The work examines how small hydropower can be modified and complemented with additional technologies to achieve sufficient frequency control capabilities. A case study was performed within the concession area of power grid operator Ålem Energy. One of the HPPs, located in Skälleryd, is owned by Ålem Energy and became the focal point of the study. Relevant parts of the concession area were surveyed for properties such as system inertia, electric load and available power. Furthermore, a model of Kaplan turbine 1 in Skälleryd HPP was created with the purpose of studying the benefits of bypassing regulation control from the wicket gates directly to the runner. The method was tested in an off-grid islanding test. Frequency control of the turbine was tested powering electric heaters and, using a new method, controlling a virtual power grid. Finally, a theory was developed to estimate the transient disturbance resilience (TDR) of a power grid. The theory was applied to the HPP in Skälleryd to suggest modifications for the plant to achieve sufficient islanding capabilities. The survey of the power system revealed a promising potential for the HPPs to operate in island mode, especially at later stages when the grid spans several HPPs for more system inertia. The available power from the HPPs was however strongly seasonal which imposes flexibility on a future plan of action for engaging the grid in island mode. The method of controlling the turbine power from the runner proved to have several difficulties. Firstly, the current hydraulics system was not able to freely control the runner as the hydrodynamic forces on the runner blades were too large. Secondly, the method was found to be unstable due to inherent amplification of speed deviations. Furthermore, the low inertia at Skälleryd is likely detrimental to the lone frequency control of the turbine. Therefore other methods for improving frequency control were suggested. The developed theory for TDR was used to create charts describing the TDR for various combinations of system inertia and regulation speed. By studying the proprieties of Skälleryd HPP in the charts the necessary modifications could be rationally chosen. A frequency regulating dummy load was found to be the simplest option. A control scheme was suggested with the dummy load performing primary frequency control and the turbines at Skälleryd performing secondary control, restoring the dummy load to its nominal state.