Submitted by Patrícia Cerveira (pcerveira1@gmail.com) on 2017-06-12T18:19:03Z No. of bitstreams: 1 José Renato Cozzolino.pdf: 2923143 bytes, checksum: 2941736082bf50938fdb3dcfea03c36e (MD5) / Approved for entry into archive by Biblioteca da Escola de Engenharia (bee@ndc.uff.br) on 2017-07-03T13:30:54Z (GMT) No. of bitstreams: 1 José Renato Cozzolino.pdf: 2923143 bytes, checksum: 2941736082bf50938fdb3dcfea03c36e (MD5) / Made available in DSpace on 2017-07-03T13:30:54Z (GMT). No. of bitstreams: 1 José Renato Cozzolino.pdf: 2923143 bytes, checksum: 2941736082bf50938fdb3dcfea03c36e (MD5) / A estimação correta de frequência é essencial para a operação de diversos equipamentos de proteção, regulação e controle, os quais são necessários para operação adequada do Sistema Interligado Nacional A tecnologia de Sistemas de Medição Fasorial Sincronizada (Synchronized Phasor Measurement Systems - SPMS), baseia-se em uma rede de Unidades de Medição Fasorial (Phase Measurement Unit - PMU). Duas grandezas importantes medidas pela PMUs são a frequência e a taxa de variação da frequência. Este trabalho apresenta o resultado de estudo comparativo de algoritmos de estimação de frequência no âmbito de medição fasorial sincronizada. Foram avaliados os modelos propostos originalmente pela Norma IEEE C37.118, por seu documento de alteração ( IEEE Std. C37.118.1a-2014 Amendment), alem de três diferentes tipos de algoritmos baseados em PLLs (Phasor Locked Loop). As avaliações foram executadas com base nos testes descritos na Norma IEEE C37.118 e seus respectivos requisitos de conformidade. Verificou-se que as modificações apresentadas pelo documento Amendment foram necessárias para que o modelo de PMU proposto atendesse os requisto para todos os testes. Em relação aos modelos de PLL, verificou-se que uma versão do algoritmo (chamada aqui de PLL de Classe III) foi bem superior às demais e também melhor que o algoritmo sugerido pelo Amendment no que se refere ao teste de derivada da frequência e de modulação de fase. / An accurate frequency estimation is essential for the operation of Electric Power System regarding protection and control. Synchronized Phasor Measurement Systems - SPMS are based on a network composed by Phasor Measurement Units (Phase Measurement Unit - PMU). Two important parameters measured by the PMUs are the frequency and the frequency rate of change. This paper presents the results of a comparative study of frequency estimation algorithms within synchronized phasor measurement context. The reference model proposed in by IEEE C37.118 standard was compared with three different algorithms based on PLLs (Phasor Locked Loop). The evaluations were performed based on the compliance requirements described in IEEE C37.118. It was also found that the PLLs models have superior performance than model reference for P PMU suggested by Standard. Regarding the reference model for PMU M, there is a need to implement anti-aliasing filters for the standard inter-harmonics tests. After that, it was observed that the dynamic performances of PLLs studied at work are compatible with the algorithms suggested by the standard for the PMU M.

Software Defined Networking (SDN) has gained popularity and attractiveness in the past years’ thanks to its dynamic and programmable nature. The possibility to decouple the data plane and control plane allows for the implementation of Internet networks in an innovative way. Thanks to its ease in changing flow rules in network switches, SDN allows network resources optimization. In the case of critical applications, an essential aspect is to ensure connectivity on the network even in case of link failures. Even when a failure causes an interruption of connectivity, the challenge also stays in recovering as fast as possible. Nonetheless, the SDN controller should have the policy to decide which pairs of end-hosts to disable connectivity when there is a shortage of resources to keep the most important connections active. In this thesis, we developed a proactive-reactive SDN controller coded in Python that copes with restoring end-hosts connectivity as fast as possible. The controller prioritizes the couples of end-hosts that need connectivity based on their importance. During a shortage of network resources, the connectivity of pairs of end-hosts with low importance is disabled, and the connectivity between the most important couples can be ensured. We tested our solution with a reactive-only SDN controller and a proactive-reactive SDN controller that does not consider any prioritization order between end-hosts connectivity. Both the benchmark SDN controllers were developed in the thesis. Experiments were run on the same network topology, with the same couple of endhosts involved. The comparison between the proactive-reactive and reactive-only controllers showed the first one to be faster in restoring the connectivity after a failure. It saves time restoring the connectivity and has fewer packets lost under certain conditions in the relationship between the switch-to-switch and the switchto-controller transmission delay. The comparison between the proactive-reactive iii controller and the controller with no prioritization confirms that without an ordered queue of priorities, it may be the most important couple of end-hosts to lose connectivity in case of shortages of network resources. To simulate a realistic scenario, the project considers the case study of electric power transmission networks using SDN. In particular, the focus is on reconnecting Phasor Measurement Unit (PMU)s to the power grid to ensure system observability. During our experiments, we adopted the typical measurement transmission frequency used by PMUs (50Hz). The SDN switches are deployed with P4, and the SDN controller is coded in Python. Furthermore, it exploits P4Runtime to communicate with the switches in run-time. / Software Defined Networking (SDN) har vunnit popularitet och attraktionskraft under de senaste åren tack vare sin dynamiska och programmerbara natur. Möjligheten att frikoppla dataplanet från kontrollplanet gör det möjligt att genomföra Internetnät på ett innovativt sätt. Tack vare att det är lätt att ändra flödesreglerna i nätverksväxlar gör SDN det möjligt att optimera nätverksresurserna. När det gäller kritiska tillämpningar är en viktig aspekt att säkerställa konnektiviteten i nätet även vid länkfel. Även när ett fel orsakar ett avbrott i konnektiviteten är utmaningen också att återhämta sig så snabbt som möjligt. Trots detta bör SDNstyrenheten ha en policy för att avgöra vilka par av slutvärdar som ska inaktivera anslutningen när det råder brist på resurser för att hålla de viktigaste anslutningarna aktiva. I den här avhandlingen har vi utvecklat en proaktiv-reaktiv SDN-styrenhet kodad i Python som klarar av att återställa slutvärdarnas anslutning så snabbt som möjligt. Styrenheten prioriterar paren av slutvärdar som behöver anslutning utifrån deras betydelse. Vid brist på nätverksresurser inaktiveras anslutningen för par av slutvärdar med låg betydelse, och anslutningen mellan de viktigaste paren kan säkerställas. Vi testade vår lösning med en enbart reaktiv SDN-styrenhet och en proaktiv-reaktiv SDN-styrenhet som inte tar hänsyn till någon prioriteringsordning mellan slutvärdarnas konnektivitet. Båda riktmärkeskontrollerna SDN utvecklades i avhandlingen. Experimenten genomfördes på samma nätverkstopologi med samma antal slutvärdar. Jämförelsen mellan den proaktivt-reaktiva och den enbart reaktiva kontrollören visade att den förstnämnda kontrollören var snabbare när det gäller att återställa anslutningen efter ett fel. Den sparar tid för att återställa anslutningen och har färre förlorade paket under vissa förhållanden i förhållandet mellan överföringsfördröjningen från switch till switch och från switch till styrenhet. Jämförelsen mellan den proaktiva-reaktiva styrenheten och v styrenheten utan prioritering bekräftar att utan en ordnad kö av prioriteringar kan det vara det viktigaste paret av slutvärdar som förlorar konnektiviteten vid brist på nätverksresurser. För att simulera ett realistiskt scenario används SDN i projektet som fallstudie för elöverföringsnät. Fokus ligger särskilt på att återansluta Phasor Measurement Unit (PMU)s till elnätet för att säkerställa systemets observerbarhet. Under våra experiment antog vi den typiska överföringsfrekvensen för mätningar som används av PMUs (50Hz). SDN-växlarna installeras med P4, och SDN-styrenheten är kodad i Python. Dessutom utnyttjas P4Runtime för att kommunicera med växlarna i körtid.

Recent large-scale blackouts revealed that power systems around the world are far from the stability and reliability requirement as they suppose to be. The post-event analysis clarifies that one major reason of the interconnection blackout is lack of wide area information. Frequency dynamics is one of the most important parameters of an electrical power system. In order to understand power system dynamics effectively, accurately measured wide-area frequency is needed. The idea of building an Internet based real-time GPS synchronized wide area Frequency Monitoring Network (FNET) was proposed to provide the imperative dynamic information for the large-scale power grids and the implementation of FNET has made the synchronized observations of the entire US power network possible for the first time. The FNET system consists of Frequency Disturbance Recorders (FDR), which work as the sensor devices to measure the real-time frequency at 110V single-phase power outlets, and an Information Management System (IMS) to work as a central server to process the frequency data. The device comparison between FDR and commercial PMU (Phasor Measurement Unit) demonstrate the advantage of FNET. The web visualization tools make the frequency data available for the authorized users to browse through Internet. The research work addresses some preliminary observations and analyses with the field-measured frequency information from FNET. The original algorithms based on the frequency response characteristic are designed to process event detection, localization and unbalanced power estimation during frequency disturbances. The analysis of historical cases illustrate that these algorithms can be employed in real-time level to provide early alarm of abnormal frequency change to the system operator. The further application is to develop an adaptive under frequency load shedding scheme with the processed information feed in to prevent further frequency decline in power systems after disturbances causing dangerous imbalance between the load and generation. / Ph. D.

This study takes advantage of wide area measurements to propose a centralized nonlinear controller that acts on power system stabilizers, to cooperatively increase the damping of problematic small signal oscillations all over the system. The structure based on decision trees results in a simple, efficient, and dependable methodology that imposes much less computational burden than other nonlinear design approaches, making it a promising candidate for actual implementation by utilities and system operators. Details are given to utilize existing stabilizers while causing minimum changes to the equipment, and warranting improvement or at least no detriment of current system behavior. This enables power system stabilizers to overcome their inherent limitation to act only on the basis of local measurements to damp a single target frequency. This study demonstrates the implications of this new input on mathematical models, and the control functionality that is made available by its incorporation to conventional stabilizers. In preparation of the case of study, a heuristic dynamic reduction methodology is introduced that preserves a physical equivalent model, and that can be interpreted by any commercial software package. The steps of this method are general, versatile, and of easy adaptation to any particular power system model, with the aggregated value of producing a physical model as final result, that makes the approach appealing for industry. The accuracy of the resulting reduced network has been demonstrated with the model of the Central American System. / Ph. D.

The future power grid will effectively utilize renewable energy resources and distributed generation to respond to energy demand while incorporating information technology and communication infrastructure for their optimum operation. This dissertation contributes to the development of real-time techniques, for wide-area monitoring and secure real-time control and operation of hybrid power systems. To handle the increased level of real-time data exchange, this dissertation develops a supervisory control and data acquisition (SCADA) system that is equipped with a state estimation scheme from the real-time data. This system is verified on a specially developed laboratory-based test bed facility, as a hardware and software platform, to emulate the actual scenarios of a real hybrid power system with the highest level of similarities and capabilities to practical utility systems. It includes phasor measurements at hundreds of measurement points on the system. These measurements were obtained from especially developed laboratory based Phasor Measurement Unit (PMU) that is utilized in addition to existing commercially based PMU’s. The developed PMU was used in conjunction with the interconnected system along with the commercial PMU’s. The tested studies included a new technique for detecting the partially islanded micro grids in addition to several real-time techniques for synchronization and parameter identifications of hybrid systems. Moreover, due to numerous integration of renewable energy resources through DC microgrids, this dissertation performs several practical cases for improvement of interoperability of such systems. Moreover, increased number of small and dispersed generating stations and their need to connect fast and properly into the AC grids, urged this work to explore the challenges that arise in synchronization of generators to the grid and through introduction of a Dynamic Brake system to improve the process of connecting distributed generators to the power grid. Real time operation and control requires data communication security. A research effort in this dissertation was developed based on Trusted Sensing Base (TSB) process for data communication security. The innovative TSB approach improves the security aspect of the power grid as a cyber-physical system. It is based on available GPS synchronization technology and provides protection against confidentiality attacks in critical power system infrastructures.

The modern day power system is witnessing a tremendous change. There has been a rapid rise in the distributed generation, along with this the deregulation has resulted in a more complex system. The power demand is on a rise, the generation and trans-mission infrastructure hasn't yet adapted to this growing demand. The economic and operational constraints have forced the system to be operated close to its design limits, making the system vulnerable to disturbances and possible grid failure. This makes the study of voltage stability of the system important more than ever. Generally, voltage stability studies are carried on a single phase equivalent system assuming that the system is perfectly balanced. However, the three phase power system is not always in balanced state. There are a number of untransposed lines, single phase and double phase lines. This thesis deals with three phase voltage stability analysis, in particular the voltage stability index known as L-Index. The equivalent single phase analysis for voltage stability fails to work in case of any unbalance in the system or in presence of asymmetrical contingency. Moreover, as the system operators are giving importance to synchrophasor measurements, PMUs are being installed throughout the system. Hence, the three phase voltages can be obtained, making three phase analysis easier. To study the effect of unbalanced system on voltage stability a three phase L-Index based on traditional L-Index has been proposed. The proposed index takes into consideration the unbalance resulting due to untransposed transmission lines and unbalanced loads in the system. This index can handle any unbalance in the system and is much more realistic. To obtain bus voltages during unbalanced operation of the system a three phase decoupled Newton Raphson load ow was used. Reactive power distribution in a system can be altered using generators voltage set-ting, transformers OLTC settings and SVC settings. All these settings are usually in balanced mode i.e. all the phases have the same setting. Based on this reactive power optimization using LP technique on an equivalent single phase system is proposed. This method takes into account generator voltage settings, OLTC settings of transformers and SVC settings. The optimal settings so obtained are applied to corresponding three phase system. The effectiveness of the optimal settings during unbalanced scenario is studied. This method ensures better voltage pro les and decrease in power loss. Case studies of the proposed methods are carried on 12 bus and 24 bus EHV systems of southern Indian grid and a modified IEEE 30 bus system. Both balanced and unbalanced systems are studied and the results are compared.