Impact Assessment of High Power Electric Bus Charging on Urban Distribution Grids

Abstract

The ongoing electrification of public bus traffic in cities improves the local air quality and can help to reduce CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emissions. Besides several operational challenges, an appropriate grid integration of battery electric buses (BEBs) is crucial to maintain a safe and stable operation of the distribution grid. Increasing charging powers of up to 600 kW may complicate the situation further. The objective of this study is to evaluate the grid impacts of three different bus charging methods - Every Station Charging, End Station Charging and Overnight Charging - on a typical urban European distribution grid. Therefore, the charging behavior of an electric bus line was modeled with a time resolution of one second and then connected to a large grid simulation. Multiple scenario modifications have been discussed, such as increasing the number of electrified bus lines, taking into account photovoltaics, and charging in the LV grid instead. Results show that the tested grid is capable of integrating BEBs in most situations, while Every Station Charging causes higher simultaneity of charging and larger voltage drops than the other scenarios. Moreover, LV charging shows to be unsuitable for high power charging. To conclude, the results of the simulations offer a solid basis for considerations regarding the electrification of public bus routes.