Fostering flexibility in distribution networks through empirical studies, regulatory analyses, and mathematical programs

The rise of congestion issues in European distribution grids due to the rapid uptake of distributed energy resources highlights the need for advancements in distribution network operation and planning. Recognizing this need, the Clean Energy Package introduced several provisions to support distribution system operators in leveraging the potential of the flexibility that is increasingly present in their networks. In this context, the main objective of this dissertation is to gain scientific knowledge and empirical information to foster the use of flexibility in distribution networks through empirical studies, regulatory analyses and mathematical programs. More specifically, the following three topics are covered: developments in distribution network planning, practical experiences with flexibility tools, and open issues when designing flexibility markets. The first part of this dissertation examines developments in distribution network planning and finds that currently, no single approach exists across European distribution system operators. Furthermore, the level of transparency and developing a robust methodology for flexibility remain open issues in distribution network planning. The second part explores the regulatory toolbox for flexibility and examines practical implementations of dynamic distribution network tariffs and flexible connection agreements. While incentives for efficient network usage are being integrated into both flexibility tools, open questions remain regarding the optimal design and compatibility of these tools. In this context, regulatory sandboxes can be an important regulatory instrument. The outcomes of existing sandbox projects reinforce the idea that regulatory sandboxes can be an effective instrument for examine innovations, such as flexibility, in a real environment. However, this potential can only be achieved when effectively implementing the administration, derogations, application process and reporting within sandbox frameworks. The third part qualitatively discusses open issues regarding the use cases, incentives, operational timeframes, rules and products, and roles and responsibilities in flexibility markets. Furthermore, a bilevel model was developed to evaluate strategic behavior in these markets. The derived characteristics of the price-setter and inc-dec games using flexibility and redispatch markets can be used to support regulators and system operators in detecting these games. Finally, a comparison of wind curtailment and imbalance data revealed that the counterbalancing costs associated with flexibility procurement can be significant, depending on the system's imbalance position. The influence of these counterbalancing costs on the use of flexibility in network planning was illustrated using a bilevel model and a stylized test case