The Geographical Aspect of Flexibility in Distribution Grids

In the Smart Grid context, one of the most broadly investigated areas is the matter of flexibility. This term is still not defined in a unified way. As such, it is frequently encountered in both transmission and distribution system studies, nonetheless, with various perspectives. To some extent, the reason for this is that flexibility is a multidimensional commodity. It can be associated with a unit or a system, a time-frame and a time-horizon of measuring it, its power magnitude and ramp rate, its energy shifting capability, its location and several other features. In this paper, the locational issue of flexibility is investigated in low-voltage distribution grids. Due to the low potential and the high uncertainty linked to a single consumer's flexibility, a common practice is to aggregate the flexibility of several consumers. By formulating an optimisation problem, this paper investigates aggregation taking into account the distribution grid's radial structure. By aggregating the flexibility in this manner, different geographical points for offering it are defined. Through an illustrative market scenario, it is demonstrated how utilities might profit from their local flexibility by assisting the distribution system operator in alleviating upcoming grid limit violations.