Determination of the Time-Dependent Flexibility of Active Distribution Networks to Control Their TSO-DSO Interconnection Power Flow

This paper describes an approach to estimate the flexibility of an Active Distribution Network (ADN) to provide ancillary services across voltage levels by the regulation of the power flow over the transmission-distribution interface. Therefore, a modelling framework is introduced to describe and discuss the impact of time-variant and time-invariant influencing factors on the flexibility of an ADN. Building on this framework, two methodologies are suggested: The first can be used to determine the flexibility of an ADN under the premise of perfect information, i.e. when all modelled influencing factors are known. The second is meant to assess in advance the flexibility that an ADN will have in future time intervals using forecasts of time-variant influencing factors handling uncertainty by a probabilistic approach. The applicability of the proposed methods is demonstrated in a case-study. Central findings regarding properties and determinability of the flexibility of ADNs are discussed.