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 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.

A Scalable Approach to Minimize Charging Costs for Electric Bus Fleets

“…This is completed by modifying P 1 in two ways. The first is that the demand, facilities, on-peak energy, and off-peak energy are removed from the objective and constrained to equal their values obtained in the solution to P 1 so that e on = ẽon e off = ẽoff p facilities = pfacilities p demand = pdemand , (13) where values on the right-hand side are constants extracted from the solution to P 1 . Next, we define an alternative objective that incentivizes continuity of charging between time steps.…”

“…High-power chargers offer an alternative to slow charge times, decreasing the charge times by using increased rates of charge. Unfortunately, fast charging also increases the demands on the underlying electrical infrastructure [13] and can make power networks unreliable [14]. Power providers must then apply expensive upgrades [15] to the infrastructure, which can make fast charging cost-prohibitive.…”

Route Scheduling for Centralized Electric Bus Depots

“…Another relevant aspect of the route-scheduling problem is the charging and discharging of the electric buses, defined in constraints ( 5)- (11). The discharging depends on the battery charge of the incoming node and the energy consumption of the bus, as shown in constraint (5).…”

“…Besides the route scheduling a further important aspect of the electric bus fleets is the charging scheduling. The scheduling of the charging events has a significant effect on the operational costs, design of charging infrastructure, the expected load peak and the grid connection point [7][8][9][10][11]. Therefore, a combined strategy of both route-and charging scheduling is necessary, especially for depots with limited capacity available from the power grid.…”

Heavy-duty electric vehicle charging profile generation method for grid impact analysis

“…Other literature focuses mainly on the impact of integrating charging of light-duty EVs or HDEVs with shorter driving range, such as urban electric buses. In [10], the impact of electric buses has been analysed. The mobility model is based on a bus network in Vienna, Austria.…”