Flexibility Aggregation Perimeter for Ancillary Services in Radial Distribution Systems

Abstract

The flexibility provided by prosumers is recognized as a key element for the management of the electrical grids, in particular distribution grids, in the changing scenario of electricity generation and consumption. The flexibility useful to Distribution System Operators (DSOs) is strongly local, and it is necessary to identify the busses of the grid where the flexibility can be usefully provided for a service requested by the DSO. For this purpose, the concept of flexibility perimeter is adopted; it is defined as a set of busses such that flexibility can be provided by any set of prosumers within it while the grid operation remains secure. The flexibility perimeter is a relevant concept for flexibility markets; in particular, for aggregators, since the flexibility provided by the prosumers within the perimeter can be offered as a single product to participants to electricity markets requiring grid services. The identification of flexibility aggregation perimeters for congestion-relief services in a radial grid is straightforward; for flexibility services intended to solve voltage profile problems, the identification of perimeters is not easy, even in radial grids. The paper proposes a method for the identification and evaluation of flexibility perimeters for grid services in radial distribution grids, based on the concept of Load Area; it can help decision-makers choose a compromise between technical and market efficiency of the aggregation perimeter dimension. For voltage This article has been accepted for publication in IEEE Access.