Vehicle-to-Grid for Road-to-Rail Energy Exchange: Using aggregated electric vehicles to provide large-scale energy storage support for electric rail systems

Abstract

Vehicle-to-Grid (V2G) describes an energy storage concept in which the built-in battery packs of parked electric vehicles (EVs) are aggregated and connected to bi-directional chargers to provide various services to the electric power grid (such as frequency regulation or load balancing). Applications of this type of energy storage can vary widely in scale and purpose. This project explores a novel application for V2G in which the aggregated storage potential of parked EVs is used to support nearby electric rail infrastructure. Connected battery packs can be discharged, thereby providing traction power to accelerating electric trains, or charged to accept power from the regenerative braking of arriving trains. The latter is of particular value for low voltage, direct current (DC) rail systems which typically do not support regeneration into the grid.

This novel concept is referred to as Road-to-Rail Energy Exchange (R2REE). It represents a large-scale energy storage application in which power demands can change rapidly by several megawatts, thus requiring fast and dynamic aggrega- tor control, capable of managing hundreds of connected EVs. This is achieved by separating aggregator control into several smaller, independently operational tasks and by exploiting the predictable and repetitive power demand patterns of timetabled rail traffic. A novel modular high-level aggregator control structure is presented that addresses these challenges of R2REE through dynamic, real-time aggregator operation along with suitable communications and data management strategies.

Furthermore, a novel method of event-based V2G scheduling is proposed that is applicable in deterministic systems where the network provides or receives electricity in reoccurring and predictable patterns or ’events’. Within the scope of this project, an event represents either the arrival of an electric train at a station (a train of known type provides power from regenerative braking to be dissipated over EV population) or a train’s departure (where power is drawn from parked EVs to support train acceleration).

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ORCID for Andrew Cruden: orcid.org/0000-0003-3236-2535

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