With an ever growing demand for electricity, it is tough to know which challenges will be the most pressing and which solutions will be appropriate to implement in different cases. This thesis utilizes simulations of three low voltage grids to see which part of the grid is most vulnerable, to which extent grid reinforcement is needed to solve voltage and load problems, and what amount of demand flexibility services would be an adequate substitute to grid reinforcement. The three grids consists of a meshed grid in a suburban area, a radial grid in the city and a radial grid in the countryside. The grids are subjected to full penetration of electric vehicle chargers in a winter setting and full solar power penetration in a summer setting. The results indicate that the transformer is overloaded in both residential grids, although even more so in the meshed grid as opposed to radial grid wherein the cables are most overloaded. The countryside grid had some voltage problems in the summer, but were overall not affected notably. The conclusions were that the increase in electric vehicle chargers will be the most impending challenge and that grid reinforcement will be necessary in the long run but that demand flexibility services are a viable option in the meantime. The transformer would also need an upgrade in both residential grids.

In this thesis the effect of harmonics on the electrical grid from electric car chargers, specifically the effect on distribution transformers, is analyzed. The study was performed on the electrical grid of two areas provided by the electrical company Dala Energi. Electric car chargers are added to each customer connected to the electrical grid in both areas to examine the effects of harmonics on the distribution transformers. A model of the electrical grid of each area was recreated and simulated with the open source program OpenDSS. The effects of the added harmonic load on the electrical grid was evaluated in a range from 10% to a 100% of the consumers connected to the grid.  The results of this study show an increase in losses due to harmonic distortion. However, the losses are less significant when the added electric car charger load is distributed between all three phases of the grid compared to one phase. All the added harmonics, except the 9th harmonic, maintain acceptable levels set by The Swedish Energy Market Inspectorate. The impact of the 9th harmonic can be reduced by installing filters. The main conclusion of this thesis is that to reduce the effects of harmonic on the grid the harmonic load should be distributed on all three phases. Also scheduling the charging time of the cars can be implemented to further even out the load variations on the electrical grid.