The ongoing electrification of public bus traffic in cities improves the local air quality and can help to reduce CO 2 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.
In this paper, the impact of EV uncontrolled charging with four levels of EV penetration in overall 21 real low voltage distribution grids in two seasons are analyzed. The employed real grid data is provided by distribution system operators from three European countries: Austria, Germany and the Netherlands. At least six grids in each country were considered and they are categorised into three types, namely rural grids, suburban grids and urban grids. The EV charging data used in this study is based on real measurements or surveys. The seasonal and the weekday-weekend factors are also considered in the EV charging impact research. Three key congestion indicators, the transformer loading, line loading and node voltage as well as several other evaluation indexes are studied. The results reveal that the majority of the simulated grids had no or minor moments of mild overloading while a few rest grids have critical issues. Among all the grids, suburban grids are most vulnerable to massive EV integration. Out of the evaluated grids, those who are located in Germany have the highest redundancy for high EV penetration accommodation. Overall, the impact of uncontrolled EV charging depends on the combination of EV charging demand as well as the grid inherent features.
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