A Graphical Measure of Aggregate Flexibility for Energy-Constrained Distributed Resources

TL;DR

This paper introduces a graphical measure of energy storage fleet flexibility that simplifies assessing whether a fleet can meet specific demand traces without recharging during the service period.

Contribution

It develops an analytical, graphical measure of fleet flexibility that enables quick feasibility checks and capability assessments for energy-constrained distributed resources.

Findings

The measure accurately summarizes feasible demand traces.

It facilitates fleet comparison and service feasibility analysis.

Applications include optimizing ancillary service provision.

Abstract

We consider the problem of dispatching a fleet of heterogeneous energy storage units to provide grid support. Under the restriction that recharging is not possible during the time frame of interest, we develop an aggregate measure of fleet flexibility with an intuitive graphical interpretation. This analytical expression summarises the full set of demand traces that the fleet can satisfy, and can be used for immediate and straightforward determination of the feasibility of any service request. This representation therefore facilitates a wide range of capability assessments, such as flexibility comparisons between fleets or the determination of a fleet's ability to deliver ancillary services. Examples are shown of applications to fleet flexibility comparisons, signal feasibility assessment and the optimisation of ancillary service provision.