Managing Flexibility in Multi-Area Power Systems
  In this paper we present a framework to efficiently characterize the available operational flexibility in a multi-area power system. We focus on the available reserves and the tie-line flows. The proposed approach is an alternative to the current calculation of the Available Transfer Capacity (ATC), as it considers location and availability of reserves, transmission constraints, and interdependencies of tie-line flows between different areas, while it takes into account the N-1 security criterion. The method is based on computational geometry using polytopic projections. It requires only a limited amount of information exchange and does not need central coordination. The method has two versions: a passive and an active approach, where neighboring areas can share reserves. In that respect we also introduce the term "exported flexibility", which could form the basis for a new trading product in electricity markets. Case studies demonstrate the improved tie-line utilization, especially if reserves are shared, and the visualization benefits. 
Matthias Bucher, Spyros Chatzivasileiadis and G\"oran Andersson
cs.SY