04 Fakultät Energie-, Verfahrens- und Biotechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/5

Browse

Institute: search.filters.UBSInstitut.Institut für Feuerungs- und KraftwerkstechnikPublication Type: search.filters.UBSTyp.Konferenzbeitrag

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    Abschaltung von dezentralen Erzeugungsanlagen infolge von Unterspannungen im Kontext von LFSM-O
    (2022) Schöll, Christian; Lehner, Joachim; Weidner, Johannes; Lens, Hendrik
    Bei einer Überfrequenz jenseits von 50,2 Hz müssen sämtliche Erzeugungsanlagen ihre in das Netz eingespeiste Wirkleistung reduzieren. In den zumeist resistiv geprägten Verteilungsnetzen der Mittel- und Niederspannung führt diese überfrequenzbedingte Leistungsreduktion zu einer lokalen Absenkung des Spannungsprofils. Unterschreiten die Spannungen die Vorgaben aus den Netzanschlussbedingungen, unter denen dezentrale Erzeugungsanlagen die Verbindung zum Netz aufrechterhalten müssen, kann es zu unterspannungsbedingten Schutzabschaltungen kommen. Theoretisch könnten diese bei großflächigem Auftreten zu einer Umkehr des ursprünglichen Überfrequenzereignisses in ein Unterfrequenzereignis führen. Anhand von simulationsbasierten Untersuchungen wird in diesem Beitrag jedoch aufgezeigt, dass unter realitätsnahen Annahmen und unter Berücksichtigung der nationalen Richtlinien sowie der zugehörigen netzplanerischen Leitplanken kein besonderes Risiko hinsichtlich der Anregung der beschriebenen Wirkungskette vorliegt.
  • Thumbnail Image
    ItemOpen Access
    Design- and simulation-based comparison of grid-forming converter control concepts
    (2021) Schöll, Christian; Lens, Hendrik
    Until now, the textbook example of voltage source behavior along with the provision of inertia is the behavior of the synchronous generator (SG). This can be explained by the historical success of large scale electrification with AC power systems, which is closely linked to the SG. Therefore, previously SG-based electrical power systems face significant challenges due to the shift towards renewable energy sources (RES). Being generally converter-based, these do not provide essential stabilizing properties as SG do. Consequently, beyond a certain share of this kind of generation, interconnected power system stability is at stake. If, on the other hand, the previous paradigm of converter control is changed, then system operation without any SG is possible. To this end, the converters have to exhibit essential voltage source properties as SG do. Such converters are then referred to as grid-forming converters (GFC). However, the dynamic behavior of GFC is not defined by physical properties as in the case of SG. It is defined by the grid-forming control concept only, providing a high degree of freedom for possible implementations. Taking advantage of this freedom, a wide range of different, but partly also similar or even equivalent grid-forming control concepts have been developed in recent years. Therefore, in this paper, ten of today's most discussed control concepts are compared. In this comparison, unique features, similarities and equivalences of the control concepts are shown. The focus is on the instantaneous and stationary behavior of the control concepts, which is analysed by means of a system-theoretical and simulative analysis. The insights gained from this comparison can be helpful for the functional specification, development and improvement of GFC, as the variety of control concepts can be better understood.
  • Thumbnail Image
    ItemOpen Access
  • Thumbnail Image
    ItemOpen Access
    Analysis of transient stability of generator groups in the future power system
    (2022) Scheifele, Daniel; Lens, Hendrik
    Transient stability is an essential property of electrical power systems. It describes the ability of the system to maintain synchronous operation of all generators. Classically, transient stability of individual generators is analyzed based on possible loss of synchronism after near short-circuit faults. In contrast, this paper considers transient stability of generator groups as a potential instability phenomenon in future grid scenarios. We investigate and analyze relevant factors of influence and countermeasures and modeling aspects to consider when studying the phenomenon. Based thereon we discuss the effectiveness of possible countermeasures. The main focus of this paper is to provide a better understanding of the underlying dependencies within the power system and their impact on the stability itself.
  • Thumbnail Image
    ItemOpen Access
    Instability phenomena in interconnected power systems caused by current limitation of grid-forming converters
    (2020) Schöll, Christian; Lens, Hendrik
    Inertia and voltage source behavior are essential for power system stability. At present, these essential features are provided by synchronous generators (SG). Grid-forming voltage source converters (VSC) can emulate these essential properties of SG and make interconnected power systems with up to 100% converter based generation possible. However, VSC lack an important property of SG: overcurrent capability. Up to now, current limiting has not been considered holistically in most grid-forming control concepts of VSC, although it has a massive impact on their dynamic behavior when active. In this paper, it is shown that this becomes particularly evident in the analysis of transient stability. By means of simulations, the stability behavior of current-limited VSC is compared to the unlimited case. By a synthetic study case and subsequent EMT simulations of a simple transmission system model, we show that there are significant differences and that the transient stability reserve is reduced due to current limitation. If current limiting is not considered in the grid-forming control concept, faults that are easy to cope with in a SG dominated system may lead to instability in power systems with a large share of such grid-forming VSC.