Analysis of load capacity in the low voltage network for different electricity load scenarios in Hammarby Sjöstad, Stockholm.

Abstract: Sweden’s population is growing rapidly, especially in the southern areas like Stockholm, where the electricity consumption is higher. Therefore, more electricity will need to be transported from north to south, from where it is produced to where it is consumed. The current electric infrastructure, i.e. the transmission and distribution networks, will need to be able to handle this consumption increase. Moreover, transition through a more sustainable cities, notably in the transport sector with the increase in electric vehicle use and electrification of public transport sector, would rise even more the electricity needs. Increase in Stockholm’s electricity consumption is not possible due to capacity limitations and grid restrictions. The situation is already strained for the city and further electricity consumption would cause several contingences. The aim of this project is to analyze the impact of the increase in electricity demand due to population growth and the integration of electric vehicles on the low voltage network in one of Stockholm’s districts, Hammarby Sjöstad. In order to analyze it, six scenarios have been simulated, one base scenario representing today’s situation, four short-term scenarios for 2025 and one long-term scenario for 2040. Different EVs penetration levels are considered, as well as two different charging schedules, following an uncontrolled charging strategy. The results show that if today’s EV sales trend remains, the low voltage grid would be able to operate properly. However, if a massive increase of EV occurred, several problems would appear. For evening charging, at peak hour the load would increase around 20%, transformers of two of the four analyzed substations would be overloaded. Problems of power quality and line overloading would appear as well. For night charging, the peak gets displaced to night hours but the network situation is similar to the previous case. Even though a 100% of EV integration is not likely to happen by 2025, it could occur by 2040. Thus, actions on the grid would need to be done if the charging remains uncontrolled. By controlling the charging schedule or introducing load management, for instance by being able to manage the energy on the battery, the problem may be reduced.