TY - CHAP A1 - Raab, Alexander A1 - Frauenknecht, Dominik A1 - Wellhöfer, Anatoli A1 - Luther, Matthias A1 - Kuri, Ananya T1 - Hybrid EMT and Phasor based MMC-HVDC Model for Advanced Power System Simulation N2 - The objective of this paper is the implementation and comparison of a hybrid phasor-based (RMS) and electromagnetic transient (EMT) modular multilevel converter high voltage direct current (MMC-HVDC) model for advanced and detailed studies of large power systems. The general modeling approach for hybrid simulation of modular multilevel converters for HVDC applications with the corresponding control concepts is described. The HVDC model can be divided into AC and DC components with different simulation time steps and representation using network partitioning. The connected AC grids and converter models are considered in the phasor-based time domain, while the DC connection is simulated in the electromagnetic-transient time domain. The coupling of the models is established by the total energy control of the MMC. The hybrid approach is evaluated in comparison to an average MMC HVDC model in an EMT simulation. The results show the advantages of the hybrid model. The model can be simulated with comparatively low computational effort, while the DC transients can be represented in detail during disturbances. Y1 - 2022 UR - 10.1109/PESGM48719.2022.9917109 PB - IEEE ER - TY - CHAP A1 - Raab, Alexander A1 - Scheibe, Christian A1 - Wellhöfer, Anatoli A1 - Nguyen, T.T.-T. A1 - Frauenknecht, Dominik A1 - Mehlmann, Gert T1 - Converter-based Control using Co-Simulation with a Power System Simulation Tool T2 - NEIS 2021 - 9th Conference on Sustainable Energy Supply and Energy Storage Systems N2 - The objective of this contribution is to implement a Co-simulation approach for control systems within RMS-based stability analyses of power systems. Inter-process communication via shared memory connects the specialized and focused software environments and enables the data exchange between them. A model of a point-to-point VSC-HVDC system with main controls is presented as the test system to be investigated. Simulations with the model in a fault case show that the results generated with the new approach are similar to those of a single-instance simulation with converted models. Simultaneously, in contrast to the existing alternatives the presented approach exhibits the benefits of Co-simulation related to efforts, costs, efficiency and model continuity, while the models remain within specialized best-in-class tools. Y1 - 2021 SN - 978-3-8007-5651-3 SP - 25 EP - 30 PB - VDE Verlag ER - TY - CHAP A1 - Semerow, Anatoli A1 - Wolf, Thomas A1 - Wellhöfer, Sabine A1 - Luther, Matthias T1 - Power system model order reduction based on dominant modes in modal analysis T2 - 2017 IEEE Power & Energy Society General Meeting N2 - Investigations of small-signal stability of electrical power systems are usually performed by modal and time-domain analysis using descriptive differential equations of machines. Thereby, the modal analysis enables the identification of all dominant states of the linearized power system model, which are associated with electromechanical interactions and power oscillations. For reasons of simplification and due to computation capabilities, a reduction of the model order is often advantageous. This can be done by neglecting different physical effects within the machines, retaining the topology and the modal characteristics of the power system regarding its electromechanical behavior. This paper presents a modal analysis based approach for power system model order reduction. In order to reproduce the small-signal behavior of power systems accurately, damping and synchronizing parameters are introduced within the reduced-order model. Subsequently, each coefficient is determined analytically for a single machine infinite bus system and using the particle swarm optimization method for a multi-machine system. The deviation to the electromechanical reference modes of the higherorder power system model constitutes the objective function to be minimized. The results confirm that the approach is suitable for the aspired goals and fulfills the accuracy requirements. Y1 - 2018 U6 - https://doi.org/10.1109/pesgm.2017.8274669 SN - 1944-9933 SP - 1 EP - 5 PB - IEEE Computer Society Press ER - TY - THES A1 - Wellhöfer, Anatoli T1 - Ein Beitrag zur Beschreibung elektromechanischer Ausgleichsvorgänge in elektrischen Energiesystemen und Ursachenidentifikation mittels Weitbereichsmessungen T1 - A Contribution to the Definition of Electromechanical Transients in Power Systems and Identification of Sources using Wide Area Measurements N2 - Die vorliegende Arbeit beschäftigt sich mit den physikalischen Phänomenen von elektromechanischen Ausgleichsvorgängen in elektrischen Energiesystemen sowie mit der Identifikation ihrer Ursachen mittels Weitbereichsmesssystemen (WAMS) im praktischen Netzbetrieb. Dabei besteht der Anspruch, einen Beitrag zum tiefergehenden Verständnis des natürlichen und erzwungenen, dynamischen Systemverhaltens zu leisten. Darüber hinaus werden innovative Methoden der Ursachenidentifikation vorgestellt und mittels Simulation validiert, um technologische Weiterentwicklungen auf diesem Gebiet zu unterstützen. Die Abhandlung fasst den aktuellen Stand der wissenschaftlichen Erkenntnisse zum elektromechanischen Verhalten von Verbundsystemen zusammen. Neben der Vorstellung einer geeigneten Modellierung dieser Systeme und bewährter Berechnungsmethoden im Frequenz- und Zeitbereich, befasst sich die Arbeit mit der Ausbreitung von Systemereignissen. Zunächst wird die Ausbreitung konzeptuell in zwei Komponenten -- elektromechanische Wellenausbreitung und simultane Beschleunigung -- zerlegt und anschließend werden deren Abhängigkeiten theoretisch fundiert aufgezeigt. Sie werden insbesondere durch das Spannungsniveau des Netzes, die Impedanzen und die Struktur der Netztopologie, die Trägheiten der Turbosätze in den Erzeugungseinheiten sowie durch den Arbeitspunkt des Systems charakterisiert. Weiterhin werden die Auswirkungen periodischer Anregungen mit verschiedenen Frequenzen im System betrachtet. Ihr Einfluss auf die Synchronmaschinen und deren gegenseitigen Leistungsaustausch stellt den Untersuchungsgegenstand dar. Es wird dabei deutlich, dass im Bereich schwach gedämpfter, niederfrequenter Moden eines elektrischen Energiesystems Resonanzerscheinungen auftreten können, die systemcharakteristische Amplituden- und Phasenverhältnisse zwischen Netzgebieten zur Folge haben. Davon unberührt bleibt die durch das System angenommene Frequenz der Ausgleichsvorgänge. Bei Anregefrequenzen oberhalb der natürlichen Moden des Systems ist die Ausbreitung der Anregung zunehmend eingeschränkt. Die Abhandlung fasst darüber hinaus den aktuellen wissenschaftlichen Stand zur Lokalisierung von Ursachen elektromechanischer Ausgleichsvorgänge mittels Weitbereichsmesssystemen zusammen, mit welchen systemweite Messungen synchronisiert durchgeführt werden. Eine besondere Aufmerksamkeit erhalten dabei die Methoden, die auf der elektromechanischen Ausbreitung und der Modalinformation aus Frequenzaufzeichnungen basieren. Ihr theoretisches Konstrukt wird in der Arbeit vertieft vorgestellt. Anschließend werden sie mit Hilfe eines dynamischen Modells des kontinentaleuropäischen Synchronverbunds (CESA) auf ihre Eignung für den praktischen Einsatz im Systembetrieb hin geprüft. Das Beurteilungskriterium besteht hierbei in der Erörterung, inwieweit ein von einem Fehler betroffener Teil eines Netzgebiets durch die verwendeten Methoden identifiziert werden kann. In den Fällen transienter Ausgleichsvorgänge zeigen sich teilweise deutliche Unterschiede in den Ergebnissen der verschiedenen Lokalisierungsmethoden auf Basis der Ausbreitung. Die nicht-parametrischen Methoden ermöglichen dabei im Durchschnitt eine bessere Zuordnung des betroffenen Netzgebiets. Unter diesen ist die eigens eingeführte Methode der Zeit-Distanz-Verhältnisse durch die Priorisierung der zuerst detektierenden Messstellen in der Regel der Ursache am nächsten. Bei der umfassenden Analyse zeigt sich jedoch auch, dass die den Methoden zugrundeliegenden Annahmen und die tatsächlichen Bedingungen eines realen Systems auseinanderliegen können und dadurch systematisch Abweichungen entstehen. Mögliche Wege zur Annäherung der Theorie an die Praxis werden im Rahmen der Abhandlung genannt. In den Fällen erzwungener Ausgleichsvorgänge kann bis auf die Spezialfälle stets eine eindeutige Zuordnung des betroffenen Netzgebiets mittels der Methoden auf Basis der Modalinformation erfolgen. Dabei wird, abhängig von den Phasenbeziehungen der beteiligten Schwingungspartner, die Entscheidung anhand der Amplituden und der voreilenden Kohärenzgruppe, die einen geringeren Dämpfungsbeitrag liefert, gefällt. Die Spezialfälle zeichnen sich durch die Bildung mehrerer kohärenter Schwingungsgruppen aus und damit durch eine mögliche Fehlinterpretation anhand der gewählten Kriterien. Grundsätzlich wird aufgezeigt, dass die vorgestellten Verfahren zur Ursachenidentifikation zu den Maßnahmen gehören, die der zunehmenden Komplexität des dynamischen Verhaltens elektrischer Energiesysteme entgegengestellt werden können. Zukünftig gilt es, die festgestellten Einschränkungen der Methoden durch tiefergehende Untersuchungen und Weiterentwicklungen auszuräumen sowie für den praktischen Einsatz zu ertüchtigen. Hierfür bildet die vorliegende Arbeit mit der Behandlung der zugrundeliegenden physikalischen Phänomene sowie der Lokalisierungsmethoden eine fundierte Basis. N2 - This thesis addresses the physical phenomena of electromechanical transients in power systems and the localization of its sources using wide area measurement systems (WAMS). Thereby, it is intended to contribute to a deeper understanding of the natural and forced dynamic system behavior. Moreover, innovative disturbance source localization methods are presented and validated by simulation in order to support further technological developments in this area of research. The state of research in the field of electromechanical behavior of interconnected power systems is recapitulated in this work. Beside the theoretical foundation of appropriate modeling approaches and established calculation methods, natural propagation mechanisms of incidents are deeply investigated. Different effects -- i.e. electromechanical wave propagation and simultaneous acceleration -- as conceptual parts of the electromechanical propagation and their substantial dependencies are derived. Thereby, an impact on the propagation mechanisms is particularly exerted by the voltage level of the system, the impedances and the structure of the system topology, the inertia of rotating masses in power plants and the system operating point. Furthermore, the impact of periodical excitation on power systems is investigated. The main focus is on the effects on synchronous machines and their mutual interactions. The analysis shows that resonance phenomena may occur if the frequency of excitation reaches the range of dominant system modes. As a consequence, characteristic amplitude and phase ratios between the different system parts arise while the oscillation frequency is adapted from the excitation source. In contrast, the electromechanical propagation of an excitation at higher frequencies than the natural system modes is physically limited. Moreover, the state of research in the field of disturbance source localization methods using wide area measurement systems is presented. These systems provide system-wide synchronized measurements of electromechanical transients. Special attention is given to those localization methods which are based on the electromechanical propagation and the modal information from frequency measurements. Beside their theoretical explanations, a method validation is performed in a dynamic model of the Continental Europe Synchronous Area (CESA) proving their suitability for practical applications. As concerns the cases of transient system behavior, significant differences are determined in the results of the methods based on electromechanical propagation. The non-parametric methods attain better identification of the affected part of the power system than parametric ones. Thereby, the results of the developed method of Time-Distance-Ratios, which prioritizes the chronological order of the event detection, are located the closest to the examined propagation sources. The analysis also shows that the underlying assumptions of the methods diverge from real conditions of power systems. Hence, systematical deviations are inherently existent. Concerning this matter, technical opportunities to adapt the methods to the real conditions are depicted. In the cases of forced system behavior, a successful identification of the affected parts of the power system can be achieved by methods using the modal information. An exception to that are those cases which are characterized by different coherent oscillation groups so that misinterpretations are possible. A source is identified by amplitude and phase ratios at different measurement locations in the system. In general, this thesis shows that the presented source localization methods are a substantial part of those countermeasures which can be used to face the growing complexity of the dynamic behavior of power systems. The determined limits of the methods have to be solved by further analysis and research in future. For these purposes, this thesis provides a solid basis covering both the fundamental physical phenomena and the source identification methods. Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:29-opus4-99820 ER - TY - CHAP A1 - Volkova, Anna A1 - Schmidhuber, Julian A1 - de Meer, Hermann A1 - Hess, Robin A1 - Schilling, Klaus A1 - Wellhöfer, Anatoli A1 - Zink, Markus T1 - Design and Simulation of LEO Satellite Communication Networks for Reliable Monitoring and Control in Power Systems T2 - The 14th DACH+ Conference on Energy Informatics Y1 - 2025 UR - https://energy.acm.org/eir/design-and-simulation-of-leo-satellite-communication-networks-for-reliable-monitoring-and-control-in-power-systems/ ER - TY - CHAP A1 - Raab, Alexander A1 - Frauenknecht, Dominik A1 - Mehlmann, Gert A1 - Luther, Matthias A1 - Wellhöfer, Anatoli T1 - Hybrid Phasor- and EMT-based Multi-Terminal MMC-HVDC Model with Grid-Forming Control T2 - 2023 IEEE Power & Energy Society General Meeting (PESGM) N2 - The objective of this paper is to apply a hybrid phasor-(RMS) and electromagnetic transient-based (EMT) simulation approach to a multi-terminal modular multilevel converter high voltage direct current (MT MMC-HVDC) model. The MMC of the MT-HVDC are implemented with grid-following and grid-forming control. An overview of the MT MMC-HVDC is given and the grid-forming and voltage droop control are described. The AC and DC networks of the MMC are divided into an RMS and an EMT partition with different simulation time steps. The grid-forming and grid-following control with inner AC current control are assigned to the RMS partition. The total energy and inner converter control are assigned to the EMT partition. The model is initialized for a correct transition from power flow to time domain simulation. The approach is implemented in a meshed power system model, where grid-forming MMC provide voltage and frequency for an offshore wind farm and a synchronous grid. The simulations are performed with the AC networks in RMS and the DC networks in EMT. The results show that the interactions between the AC and DC grids can be studied in a hybrid simulation framework. The DC system response is detailed, while the AC system is reduced to machine and controller dynamics. Y1 - 2023 SN - 978-1-6654-6441-3 U6 - https://doi.org/10.1109/pesgm52003.2023.10253370 SN - 1944-9933 PB - IEEE ER - TY - CHAP A1 - Frauenknecht, Dominik A1 - Schweinshaut, Bernd A1 - Raab, Alexander A1 - Mehlmann, Gert A1 - Luther, Matthias A1 - Wiest, Pascal A1 - Heyde, Chris Oliver A1 - Wellhöfer, Anatoli ED - VDE ETG, T1 - Stability Analysis of Converter-Dominated Power Systems by Phasor-Based and Electromagnetic Transient Simulation T2 - 15. VDE ETG/VDI/VDE-GMA-Fachtagung „Netzregelung und Systemführung“ Y1 - 2024 SN - 978-3-8007-6292-7 ER - TY - JOUR A1 - Walle Biyazne, Likenesh A1 - Berhanu Tuka, Milkias A1 - Mekonnen Abebe, Yoseph A1 - Wellhöfer, Anatoli T1 - Enhancing MPPT performance of a grid-connected Doubly-Fed induction generator-based wind power plant using hybrid ANFIS-PI control strategy JF - Nature Scientific Reports N2 - This paper focuses on an effective control technique for enhancing the Maximum Power Point Tracking (MPPT) performance of a grid-connected DFIG-based wind power plant under continuously varying wind conditions. However, rapid fluctuations in wind speeds, uncertainties in parameters, and grid disturbances are key challenges to enhancing the MPPT performance capability. Considering these struggles, this study aims to model a modified dynamic DFIG-based wind turbine system and develop a hybrid Adaptive Neuro-Fuzzy Inference System (ANFIS) with a Proportional-Integral (PI) controller on the back-to-back converter at the rotor and grid sides. The actual limited ranges of wind speed and output power generation data of the Adama II wind power plant in Ethiopia are utilized as input and output variables for the ANFIS controller. The simulation results from the latest version of R2024a MATLAB-Simulink software show that the proposed ANFIS-PI reached an MPPT of 2.22 MW compared to the FLC-PI controller attained 2.2 MW using the benchmark as the reference value of 1.561 MW in the PI controller, by improving the maximum power coefficient of 0.5504 compared to 0.5473 using the baseline as the reference value of 0.4109, respectively, at a rated wind speed of 12.5 m/s and an optimal pitch angle of 0°. KW - Adaptive Neuro-Fuzzy inference system KW - Doubly-Fed induction generator KW - MATLAB-Simulink software KW - Maximum power point tracking KW - Proportional-Integral Y1 - 2026 UR - https://doi.org/10.1038/s41598-026-36021-3 VL - 16 ER -