Analysis of new control applications

This document reports the results of the activities performed during the first year of the CRUTIAL project, within the Work Package 1 "Identification and description of Control System Scenarios". It represents the outcome of the analysis of new control applications in the Power System and the identification of critical control system scenarios to be explored by the CRUTIAL project

Remedial action schemes for power system performance enhancement using protective relaying

Nowadays, according to the improvement of industries, and the growth of the population, the need for high-quality energy is felt more and more. One of the significant challenges in designing distributed power networks is providing reliable protection with the target of decreasing blackouts. This goal can be achieved by detecting faults in the power system and action to correct or remove the faults. In most cases, taking correct and quick remedial action to protect the power system is done by tripping. Generally, the protective relaying equipment is responsible for tripping in a power system. In this thesis, various types of remedial action schemes for power system performance enhancement using protective relaying are studied in detail. The concept of power system protection consists of protection components, and their functionality is illustrated. Furthermore, several types of protective relays, and their general operating and design considerations are briefly investigated. Several protective relays such as analog overcurrent relay, digital overcurrent relay, and digital under-over frequency relay are investigated, modeled, and simulated in this thesis. To study the power system frequency response, the System Frequency Response (SFR) model is derived and simulated in MATLAB Simulink environment, and the effect of some parameters of a generator on the system’s frequency response is examined. Additionally, a new method to model power system frequency response is proposed based on the factorial design method using the Design of Expert. The actual system and the final model are simulated, compared, and validated. The result shows that the model based on the proposed method can be used to estimate the system frequency response. The concept of load curtailment (load shedding) and its different methods are discussed. A conventional underfrequency load shedding relay is simulated in MATLAB software to show how load shedding relays can enhance power system performance. The significant factors which affect power system stability are identified. To show the effect of significant factors on power system stability, a standard IEEE 9-Bus and the IEEE 10-Generator 39-Bus New England Test System are simulated in the PowerWorld. Finally, the concept of autoreclosing is studied in detail. An autorecloser relay is designed, simulated, and examined in MATLAB Simulink, and the proposed relay’s units are explained. Optimal autoreclosing methods are also presented in this thesis

Design and Development of Protection Schemes for FREEDM Smart Grid Systems

abstract: This research work describes the design and validation of protection schemes developed to solve the problem of communication with an ability to detect and sectionalize the fault. Protection schemes have been designed according to the requirements of the Future Renewable Electric Energy Delivery and Management (FREEDM) system. Due to the presence of distributed generation (DG), power flow in the loop is bi-directional and conventional protection schemes may face the problem of unwanted tripping. Hence customized protection schemes have been developed specific to the FREEDM system. Former FREEDM students at ASU have developed ultrafast pilot differential protection using fast analog communication (Ethercat communication) and modified it in various ways to speed up the fault detecting capability of the algorithm. However, the National Science Foundation (NSF) criticized the use of Ethernet communication, as it is not compatible for long distances. FREEDM loop uses a fault current limiter (FCL) to limit the fault current and the substation solid state transformer (SST) reduces the system voltage to limit the fault current to 2 per unit. This allows the protection scheme to detect fault current in 2-3 cycles. However a much delayed fault detection is not encouraged as it will disrupt the power supply to healthy parts of the system for a longer duration. Time inverse directional overcurrent protection, pilot directional protection and PMU based protection are developed in this thesis work addressing the communication problem and at the same time with the ability to quickly detect the faults. Validation of the protection scheme is performed on the Real Time Digital Simulator (RTDS) at the Center for Advanced Power Systems (CAPS) using SEL relays and simulation models are developed in PSCAD.Dissertation/ThesisMasters Thesis Electrical Engineering 201

Enhancing transient performance of microgeneration-dense low voltage distribution networks

In addition to other measures such as energy saving, the adoption of microgeneration driven by renewable and low carbon energy resources is expected to have the potential to reduce losses associated with producing and delivering electricity, combat climate change and fuel poverty, and improve the overall system performance. However, incorporating a substantial volume of microgeneration within a system that is not designed for such a paradigm could lead to conflicts in the operating strategies of the new and existing centralised generation technologies. So it becomes vital for such substantial amount of microgeneration among other decentralised resources to be controlled in the way that local constraints are mitigated and their aggregated response supports the wider system. In addition, the characteristic behaviour of connected microgeneration requires to be understood under different system conditions to ascertain measures of risk and resilience, and to ensure the benefits of microgeneration to be delivered. Therefore, this thesis provides three main valuable contributions of future attainment of sustainable power systems. Firstly, a new conceptual control structure for a system incorporating a high penetration of microgeneration and dynamic load is developed. Secondly, the resilience level of the host distribution network as well as the resilience levels of microgeneration during large transient disturbances is evaluated and quantified. Thirdly, a technical solution that can support enhanced transient stability of a large penetration of LV connected microgeneration is introduced and demonstrated. A control system structure concept based on “a cell concept” is introduced to manage the spread of heavy volumes of distributed energy resources (DERs) including microgeneration such that the useful features of DER units in support of the wider system can be exploited, and the threats to system performance presented by significant connection of passive and unpredictable DERs can be mitigated. The structure also provides simpler and better coordinated communication with DERs by allowing the inputs from DERs and groups of cells to be transferred as collective actions when it moves from a local to a wider system level. The anticipated transient performance problems surrounding the integration of microgeneration on a large basis within a typical urban distribution network are addressed. Three areas of studies are tackled; the increased fault level due to the present of microgeneration, the collective impact of LV connected microgeneration on traditional LV protection performance, and the system fault ride through capabilities of LV connected microgeneration interfaced by different technologies. The possible local impacts of unnecessary disconnection of large amount of microgeneration on the performance of the host distribution network are also quantified. The thesis proposes a network solution based on using resistive-type superconducting fault current limiters (RSFCLs) to prevent the impact of local transient disturbances from expanding and enhance the fault ride through capabilities of a high penetration of microgeneration connected to low voltage distribution networks. A new mathematical approach is developed within the thesis to identify at which condition RSFCL can be used as a significant device to maintain the transient stability of large numbers of LV connected microgeneration. The approach is based on equation solution to determine the minimum required value of the resistive element of RSFCL to maintain microgeneration transient stability, and at the same time additional headroom against switchgear short-circuit ratings is provided. Remote disturbances or a failure to clear remote faults quickly are shown to no longer result in complete unnecessary disconnection of substantial amount of microgeneration

Portuguese transmission grid incidents risk assessment

Documento confidencial. Não pode ser disponibilizado para consultaTese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201

On power system automation: a Digital Twin-centric framework for the next generation of energy management systems

The ubiquitous digital transformation also influences power system operation. Emerging real-time applications in information (IT) and operational technology (OT) provide new opportunities to address the increasingly demanding power system operation imposed by the progressing energy transition. This IT/OT convergence is epitomised by the novel Digital Twin (DT) concept. By integrating sensor data into analytical models and aligning the model states with the observed system, a power system DT can be created. As a result, a validated high-fidelity model is derived, which can be applied within the next generation of energy management systems (EMS) to support power system operation. By providing a consistent and maintainable data model, the modular DT-centric EMS proposed in this work addresses several key requirements of modern EMS architectures. It increases the situation awareness in the control room, enables the implementation of model maintenance routines, and facilitates automation approaches, while raising the confidence into operational decisions deduced from the validated model. This gain in trust contributes to the digital transformation and enables a higher degree of power system automation. By considering operational planning and power system operation processes, a direct link to practice is ensured. The feasibility of the concept is examined by numerical case studies.The electrical power system is in the process of an extensive transformation. Driven by the energy transition towards renewable energy resources, many conventional power plants in Germany have already been decommissioned or will be decommissioned within the next decade. Among other things, these changes lead to an increased utilisation of power transmission equipment, and an increasing number of complex dynamic phenomena. The resulting system operation closer to physical boundaries leads to an increased susceptibility to disturbances, and to a reduced time span to react to critical contingencies and perturbations. In consequence, the task to operate the power system will become increasingly demanding. As some reactions to disturbances may be required within timeframes that exceed human capabilities, these developments are intrinsic drivers to enable a higher degree of automation in power system operation. This thesis proposes a framework to create a modular Digital Twin-centric energy management system. It enables the provision of validated and trustworthy models built from knowledge about the power system derived from physical laws, and process data. As the interaction of information and operational technologies is combined in the concept of the Digital Twin, it can serve as a framework for future energy management systems including novel applications for power system monitoring and control, which consider power system dynamics. To provide a validated high-fidelity dynamic power system model, time-synchronised phasor measurements of high-resolution are applied for validation and parameter estimation. This increases the trust into the underlying power system model as well as the confidence into operational decisions derived from advanced analytic applications such as online dynamic security assessment. By providing an appropriate, consistent, and maintainable data model, the framework addresses several key requirements of modern energy management system architectures, while enabling the implementation of advanced automation routines and control approaches. Future energy management systems can provide an increased observability based on the proposed architecture, whereby the situational awareness of human operators in the control room can be improved. In further development stages, cognitive systems can be applied that are able to learn from the data provided, e.g., machine learning based analytical functions. Thus, the framework enables a higher degree of power system automation, as well as the deployment of assistance and decision support functions for power system operation pointing towards a higher degree of automation in power system operation. The framework represents a contribution to the digital transformation of power system operation and facilitates a successful energy transition. The feasibility of the concept is examined by case studies in form of numerical simulations to provide a proof of concept.Das elektrische Energiesystem befindet sich in einem umfangreichen Transformations-prozess. Durch die voranschreitende Energiewende und den zunehmenden Einsatz erneuerbarer Energieträger sind in Deutschland viele konventionelle Kraftwerke bereits stillgelegt worden oder werden in den nächsten Jahren stillgelegt. Diese Veränderungen führen unter anderem zu einer erhöhten Betriebsmittelauslastung sowie zu einer verringerten Systemträgheit und somit zu einer zunehmenden Anzahl komplexer dynamischer Phänomene im elektrischen Energiesystem. Der Betrieb des Systems näher an den physikalischen Grenzen führt des Weiteren zu einer erhöhten Störanfälligkeit und zu einer verkürzten Zeitspanne, um auf kritische Ereignisse und Störungen zu reagieren. Infolgedessen wird die Aufgabe, das Stromnetz zu betreiben anspruchsvoller. Insbesondere dort wo Reaktionszeiten erforderlich sind, welche die menschlichen Fähigkeiten übersteigen sind die zuvor genannten Veränderungen intrinsische Treiber hin zu einem höheren Automatisierungsgrad in der Netzbetriebs- und Systemführung. Aufkommende Echtzeitanwendungen in den Informations- und Betriebstechnologien und eine zunehmende Menge an hochauflösenden Sensordaten ermöglichen neue Ansätze für den Entwurf und den Betrieb von cyber-physikalischen Systemen. Ein vielversprechender Ansatz, der in jüngster Zeit in diesem Zusammenhang diskutiert wurde, ist das Konzept des so genannten Digitalen Zwillings. Da das Zusammenspiel von Informations- und Betriebstechnologien im Konzept des Digitalen Zwillings vereint wird, kann es als Grundlage für eine zukünftige Leitsystemarchitektur und neuartige Anwendungen der Leittechnik herangezogen werden. In der vorliegenden Arbeit wird ein Framework entwickelt, welches einen Digitalen Zwilling in einer neuartigen modularen Leitsystemarchitektur für die Aufgabe der Überwachung und Steuerung zukünftiger Energiesysteme zweckdienlich einsetzbar macht. In Ergänzung zu den bereits vorhandenen Funktionen moderner Netzführungssysteme unterstützt das Konzept die Abbildung der Netzdynamik auf Basis eines dynamischen Netzmodells. Um eine realitätsgetreue Abbildung der Netzdynamik zu ermöglichen, werden zeitsynchrone Raumzeigermessungen für die Modellvalidierung und Modellparameterschätzung herangezogen. Dies erhöht die Aussagekraft von Sicherheitsanalysen, sowie das Vertrauen in die Modelle mit denen operative Entscheidungen generiert werden. Durch die Bereitstellung eines validierten, konsistenten und wartbaren Datenmodells auf der Grundlage von physikalischen Gesetzmäßigkeiten und während des Betriebs gewonnener Prozessdaten, adressiert der vorgestellte Architekturentwurf mehrere Schlüsselan-forderungen an moderne Netzleitsysteme. So ermöglicht das Framework einen höheren Automatisierungsgrad des Stromnetzbetriebs sowie den Einsatz von Entscheidungs-unterstützungsfunktionen bis hin zu vertrauenswürdigen Assistenzsystemen auf Basis kognitiver Systeme. Diese Funktionen können die Betriebssicherheit erhöhen und stellen einen wichtigen Beitrag zur Umsetzung der digitalen Transformation des Stromnetzbetriebs, sowie zur erfolgreichen Umsetzung der Energiewende dar. Das vorgestellte Konzept wird auf der Grundlage numerischer Simulationen untersucht, wobei die grundsätzliche Machbarkeit anhand von Fallstudien nachgewiesen wird