Master's Thesis Paul Kessler


Development of an assessment model for DSOs to determine the technical and economic potential of local energy systems

Design and simulation process of the integrated assessment model Copyright: EBC Design and simulation process of the integrated assessment model

As multiple European countries promote the expansion and development of local renewable energy sources, new challenges arise for the stable and secure operation of existing distribution grids. In consequence, distribution system operators (DSOs) are compelled to face these challenges and create new opportunities to extend the number of renewable energy sources (RESs) in distribution grids.

For this purpose, the present work develops an integrated assessment model to evaluate the techno-economic potential of grid expansion strategies for local energy systems (LESs) that are exposed to a rising share of RESs. The model further comprises the fields of energy and power system modeling to determine the optimal design and utilization of local energy resources whereas electric grid constraints are taken into account. Therefore, this model aims to support DSOs at an early stage of the grid planning process.

The implemented model includes 4 modules that examine the optimal configuration of the LES regarding the techno-economic performance of different grid reinforcement options. Therefore, the superior module determines possible grid reinforcement options based on the economic performance and assigns these to the subordinate modules, in which the technical impact is assessed. These modules automatically process the input data of the grid operator and subsequently determine the optimal utilization of local energy resources by balancing distributed generation and consumption in accordance to the assigned grid reinforcement options. Based on the output of this module, worst-case scenarios are identified that may endanger the power quality and stability limits of the LES. Moreover, these scenarios are examined using AC power-flow calculations to assess the impacts on power quality and the stability thresholds of the observed grid.

The developed assessment model is applied to two Hungarian case studies that currently face various challenges induced by a rising share of renewables, most notably photovoltaic generators. The results show that innovative grid reinforcement options have a significant impact on the constraints of the grid and the DSO's economic efficiency for this application. Active network management options are found to serve as a cost-effective alternative to substitute or postpone conventional grid expansion strategies in times of high shares of RESs connecting to the distribution grid. In particular, alternative grid reinforcement options are capable to increase the share of renewables from 3.24% to 9.72% while investment costs are reduced in comparison to the conventional grid reinforcement approach by up to 50% for one of the observed use cases.