Increasing the Integration Potential of EV Chargers in DC Trolleygrids: A Bilateral Substation-Voltage Tuning Approach

Light rail networks such as trolleybus grids have the potential to become multi-functional smart grids by using the excess capacity of the grid to implement PV systems, EV chargers, and storage. This paper offers a solution to increasing the potential for integration of EV chargers in the trolleygrid, without additional infrastructure costs, by simply tuning the nominal (no-load) voltages of bilaterally connected substations. This method shifts the load share between the two substations, creating more room for the integration of other utilities in a desired zone of the bus route. A mathematical derivation is presented, followed by a verifying case study using detailed and verified bus and trolleygrid simulation models for the city of Arnhem, the Netherlands. It is shown that by setting a substation nominal voltage from +10V compared to its bilateral substation to -10V, the substation can take, on average, as much as 7.5 percentage points less of the load share (from 45.9% to 38.4%) and see as much as 5 percentage points more of complete zero-load time (84.3% to 89.2%).