Stochastic assessment of electric car charging on the LV distribution grid

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Dr. Farkas Csaba
Department of Electric Power Engineering

Due to the spread of electric cars new kind of problems are appearing in connection with the power grids. In order to use our vehicles every day and be able to take the required distances we have to charge the batteries of the cars every night. However, single phase household charging has an asymmetric impact on the elements of the distribution grid therefore these elements could become overloaded and there could be a significant voltage drop at the connection points of the household and concentrated consumers. For this reason, models demonstrating the use of these vehicles are necessary and we should examine the existing elements of the power grid for future usage.

In my thesis I present a modelling process for the network impacts of electric cars. Based on the information provided by an electricity supplier company and my university consultant I created 10 circuits which differed in the number of household and concentrated consumers and chargers for vehicles. Considering 0%, 20% and 100% penetration of electric cars and taking into account the earthing of the neutral conductor I assigned 3+3 models to the circuits. Using DIgSILENT PowerFactory software I carried out 50 stochastic load-flow calculations per model in order to determine the load of the transformers in the given areas as well as the voltages of the various busbars. After the stochastic load-flow calculations I examined the negative and the zero sequence voltage asymmetries of the line with the most consumers in order to get a general idea of the behaviour of the distribution grid elements. Finally, I present the impressibility of the network impacts with the help of the electric car charging control.


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