Master's thesis and Internship : Coordinating Transmission And Distribution System Operators Through Secure Operating Envelopes.

Abstract

This thesis presents a coordination method between operators that ensures static network security when grid operation is distributed across interconnected subnetworks operated by independent entities that follow a hierarchy. The hierarchy consists of a parent network (typically the transmission network) connected to child networks (typically the distribution networks). The coordination of these hierarchical networks is based on power and voltage magnitude ranges at their interface. The voltage magnitude ranges, called voltage operating envelopes (VOEs), are first agreed upon, and the power limits, called power operating envelopes (POEs), are then computed to ensure local security for all operating conditions on the children's networks. In this thesis, this coordination approach is detailed and particularized to TSO/DSO coordination, where the TSO computes POEs at the interface with DSOs, based on agreed VOEs. An optimization problem is proposed to compute POEs at TSO/DSO interfaces, defining admissible operating regions that DSOs must respect during operation. As long as DSOs respect the POEs, there exists a set of control actions in the TSO's network such that its network remains secure. In the proposed optimization problem, phase-shifters' set-point modifications and the generators' re-dispatch are considered as control actions. The power flows are modeled through a quadratic convex approximation of the AC power flow equations. At the end, POEs and VOEs enable coordination among operating entities while maintaining a low level of data exchange among them.