Betriebliche Spannungshaltung im Übertragungsnetz unter Berücksichtigung von Unsicherheit

Knittel, Markus; Moser, Albert (Thesis advisor); Rehtanz, Christian (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

The progressive integration of renewable energies in power systems leads to an increase in uncertainty of power generation due to their intermittent nature and thus has a significant impact on the operational voltage control in transmission grids. Consequently, operational concepts have to be developed that allow controlling the increasing uncertainty utilizing the future reactive power compensation portfolio. Two different approaches exist for this purpose. On the one hand, the scheduling of the reactive power dispatch during the operational planning phase can prioritize the provision of flexible reactive power potentials and create additional security margins for the operational voltage limits. On the other hand, automation concepts can be used to enable fast adaptions of the reactive power dispatch in real-time operation. From these approaches, three different concepts are developed in this thesis. Two of these concepts are based on a centralized optimal reactive power flow (ORPF). In the first concept, it is applied in a time-coupled ORPF (TC-ORPF) for the predictive determination of pareto-optimal reactive power schedules during operational planning. In the second concept, the optimization is operated in a closed-loop (CL-ORPF). To this end, new setpoints are sent to all optimized devices in real-time operation based on the optimization results without manual validation. Switching automatics for mechanically switched shunt compensators are applied as the third concept. The corresponding parameters have to be designed for the forecasted grid situations during operational planning. Switching actions of reactors or capacitor banks are then triggered in real-time operation depending on the local voltage measurements.To validate the developed concepts, they were simulated exemplarily for generation time series subject to uncertainty. Compared to constant operating points of reactive power compensators and their corresponding local controls, the risk of voltage band violations could be significantly reduced in all concepts. The most robust results were obtained by the TC-ORPF, whereas the robustness of the CL-ORPF and the switching automatics showed a clear dependence on the considered grid situations. The robustness of the CL-ORPF increases with the increasing availability of reactive power potentials of decentral generation units. For switching automatics, a decreasing share of voltage-controlled reactive power compensation in the transmission grid leads to additional restrictions for the parameter layout, since lower and upper voltage thresholds with a higher distance to the reference voltage have to be selected. A combination of the concepts is possible in theory since the schedules derived in the TC-ORPF during operational planning can be adjusted during real-time operation by using the CL-ORPF or switching automatics.

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