Operational flexibility of active distribution networks: Definition, quantified calculation and application

With a high penetration of intermittent distributed generators (DGs), the uncertainties in active distribution networks (ADNs) are exacerbated and further coupled in the networks. It brings enormous challenges on system operation and puts forward a higher requirement for the operational flexibility of ADNs. However, due to the secure constraints and diverse operational requirements, the controllability of controllable resources (CRs) cannot fully facilitate the flexible operation of ADNs. Operational flexibility is seen as a link between diverse operational requirements and flexible adjustment capabilities of CRs, which also represents the ability of the network to deploy its CRs to respond to the change of operation states. Under the framework of operational flexibility, multiple types of operational optimization problems can be reinterpreted, which provides a new perspective for the operation of ADNs. In this paper, the definition and region-based mathematical formulation of operational flexibility for ADNs are proposed firstly. Then the quantified calculation method of operational flexibility is proposed to represent flexibility provision (FP) and flexibility availability (FA). The application of operational flexibility is analyzed from the perspective of diverse operation and improvement of flexibility. Finally, case studies are performed on the modified IEEE 33-node system to show the effectiveness of the proposed method.