In an effort to combat climate change, society is moving towards greater electrification while increasing the share of intermittent power generation. As a result, the power balance in the grid is becoming harder to keep up at all times. One proposed way to increase power system reliability is through the implementation of Microgrids (MGs). MGs have the ability to disconnect from the main grid, which both can decrease the stress on the grid, and increases the reliability in the MG. However, having the MG disconnect from the main grid and transition to island operation is a challenging task from a control theory perspective. Solving the issue of how to transition to island operation without any disturbances occurring, will contribute to MGs potentially being used on a larger scale in the main grid, effectively contributing to increased reliability. The aim of the degree project was to build a model of the MG on Arholma using MATLAB Simulink, with a special focus on the design of the control system for the intentional island transition process. The Arholma MG consists of two Battery Energy Storage Systems (BESSs), a Photovoltaic (PV) system and 199 loads. Building the model, an existing Simulink model of Arholma MG was used as a reference. The focus while building the model was the load behavior as well as the MG controller. The controller was designed to have its functions split up on three components, at the two BESSs and the Point of Common Coupling (PCC). At the PCC, the controller was implemented to make the MG being able to intentionally transition to island operation. At one of the BESSs, the controller was redesigned to make it do grid forming control like the other BESS. Lastly the Proportional Integral (Pl) parameters in the BESSs controllers were tuned and the model was tested on various load dynamics. It could be concluded that the control system could not manage to keep the frequency- and voltage deviations within the required limits of ±0.1 Hz respectively ±0.05 Per Unit (p.u.), as has been achieved in the real Arholma MG. The control system was able to handle load changes up to 5.04 kW per second and still intentionally transition to island operation. The fastest the control system was able to make the MG transition to island operation was in 3.66 seconds, counting from when the first step of the intentional island transition was initiated, to the time when the MG's breaker opened.

I ett forsok att motverka klimatforandringarna, gar samhallet mot att elektrifie­ra i en hogre grad, samtidigt som andelen intermittent produktion tilltas. Detta resulterar i att effektbalansen i natet blir svarare att hfillas vid varje tidpunkt. Ett forslag for att oka tillforlitligheten i elnatet ar genom implementeringen av mikronat. Mikronat har formagan att frankopplas fran det stora elnatet, vilket bade kan minska stressen i elnatet, och oka tillforlitligheten inom mikronatet. Daremot ar att frankoppla mikronatet fran det stora natet och overga till odriftslage en utmanande uppgift utifran ett reglertekniskt perspektiv. Att losa fragestallningen hur overgangen till odriftslage utan nagra storningar kan goras, skulle bidra till att mikronat potentiellt implementeras i en storre skala i det stora natet, vilket skulle bidra till okad tillforlitlighet. Syftet med detta examensarbete var att bygga en modell av mikronatet pa Arholma genom att anvanda MATLAB Simulink, med ett sarskillt fokus pa utformningen av kontrollsystemet for den planerade odriftsattningen. Arholma mikronat bestar av tva Batterilagringssystem (BLS), ett solcellssystem och 199 laster. Modellen byggdes med en existerande Simulinkmodell av Arholma mikronat som referens. Fokuset nar modellen byggdes lag pa lasternas beteende samt mikronatets kontrollsystem. Kontrollsystemet var konstruerat sa att dess funktioner delades upp pa tre komponenter, vid de tva BLSen och vid den gemensamma anslutningspunkten. Kontrollsystemet vid den gemensamma anslutningspunkten implementerades for att mojliggora for mikronatet att utfora en planerad odriftsattning. Kontrollsystemet vid ett av BLSen var omkonstruerat for att fa det att utfora natbildande styrning som det andra BLSet. Till sist justerades de Proportionell Integral (Pl) parametrarna och modellen testades pa flertalet lastdynamiker. Slutsatsen kunde dras att kontrollsystemet inte kunde halla frekvens- och spanningsavvikelserna inom de kravda granserna pa ±0,1 Hz respektive ±0,05 per enhet, som det riktiga mikronatet pa Arholma har lyckats med. Kontrollsystemet kunde hantera lastforandringar pa upp till 5,04 kW per sekund och fortfarande kunna genomfora en planerad odriftsattning. Kontrollsystemet kunde som snabbast fa mikronatet att odriftsattas pa 3.66 sekunder, raknat fran nar det forsta steget i den planerade odriftsattningen paborjades, till da brytaren oppnades.