Navigating Uncertainty. Active Power Curtailment Approaches for Planning of Medium Voltage Distribution Grids

With the acceleration of the energy transition, the installed capacity of renewable energy sources (RES) is increasing faster than ever. Most of the newly installed RES plants are installed in the distribution grids. This welcomed development poses a challenge to distribution grid planners. While investment decisions for new RES plants can be made fast, procedures for grid reinforcement are relatively slow. This leads to the requirement of predictive planning for multiple years ahead to be able to integrate all new RES plants. However, there is a high uncertainty about actual RES investment decisions. This uncertainty concerns the size, timing, and location of new RES installations. Even if realistic RES scenarios are considered - based on a detailed regionalization of national RES targets, already established wind power potential areas, and rooftop potential – the uncertainty remains. This uncertainty can be tackled by considering active power curtailment (APC) in grid planning. APC can serve as an interim solution and defer or avoid grid reinforcement. To this end, a curtailment of 3 % of the annual generation of a RES plant is allowed in the planning process in Germany. This planning option was designed to bring more renewable energy plants into the existing grid in a shorter time. Current research proposes various approaches for grid planning with APC. Promising time-series-based approaches can find economically efficient trade-offs between reinforcement and curtailment. However, time-series-based calculations usually result in high computational efforts. Therefore, this thesis takes a deep dive into planning approaches with APC and suggests a new framework for planning with APC that combines the benefits of existing approaches. This framework is extended and adapted to address the aspects of multi-year grid planning and planning under uncertainty. The application of the developed framework is tested on several target grid planning case studies, as well as multi-scenario and multi-year planning case studies. A further key contribution of this thesis is the definition of key performance indicators for robustness and robust optimality in target grid planning with APC under uncertainty. They are integrated into a cross-checking procedure for grid planning to identify robust transformation paths with APC. The resulting framework is suitable for performing risk analysis for planning decisions with respect to APC. In a case study on a real grid model of EAM Netz GmbH, it is shown that the curtailment restriction scheme (e.g., 3 % per generator), the reactive power operation, and the curtailment price are analyzed have a high impact on the optimal trade-off between reinforcement and curtailment. In the past years of extensive redispatch, the introduction of the 3 % criterion in 2016 provided relief for the grid reinforcement need. This thesis suggests a shift toward the economic efficiency of grid expansion versus the costs of curtailment as a primary design principle, which may enable a more economically efficient expansion of the distribution grids.