Known vehicle systems include one or more propulsion-generating vehicles or units and, in certain cases, one or more non-propulsion-generating vehicles or units, connected with each other to travel along a route. The propulsion-generating vehicles supply tractive force to propel the propulsion-generating vehicles and non-propulsion-generating vehicles along the route.
The propulsion-generating vehicles may be powered by electric current supplied to the vehicles from an off-board source via one or more conductive pathways that extend along the route being traveled. For example, the route (or at least a section thereof) may include a conductive pathway that is part of the route or that extends along the route and that supplies electric current to the propulsion-generating vehicles to power these vehicles. Such a conductive pathway may include an electrified rail, an overhead catenary, and the like.
The tractive force required to propel the propulsion-generating vehicles and non-propulsion-generating vehicles along the route may vary during a trip due to various parameters that change with position and/or time during the trip. These changing parameters may include the curvature and/or grade of the route, speed limits and/or requirements of the vehicle system, and the like. For electric propulsion-generating vehicles that are powered from electrical energy (e.g., electric current) from a section of an electrical route powered by an electrical power grid, the amount of electric energy that is demanded (e.g., drawn) by the electric propulsion-generating vehicles changes as the required tractive effort changes.
Presently, the overall number of electric propulsion-generating vehicles that can be operated on a section of a route that supplies electric energy to these propulsion-generating vehicles is limited by the capacity of the source of the electric energy. Several electric propulsion-generating vehicles demanding electric energy from the same source or bank of sources at the same time, for example, may demand a combined amount of electric energy that exceeds or risks exceeding the capacity of the source. Exceeding this capacity can result in insufficient electric energy being supplied to one or more of the propulsion-generating vehicles and, as a result, stall one or more vehicles. Such stalls can cause transportation delays.
In addition, other loads external to the vehicles may demand electric energy from the same source that also powers the propulsion-generating vehicles. For example, cities, towns, and the like may have many electric loads that are powered by electric energy from the same source that also powers the propulsion-generating vehicles. If the capacity of the source is exceeded by energy draw from the propulsion-generating vehicles and the other loads, insufficient electrical energy may be available for the other loads, which can lead to power outages.
One potential solution to the above problems is to increase the capacity of the source, increase the capacity of the conductive pathways that supply the electric energy, and/or increase the number of sources of electric energy. These solutions, however, involve significant financial costs and may be prohibitively expensive.