This thesis investigates the use of real-time phasor measurements for voltage and transient stability monitoring and control. Taking advantage of the ability of a Phasor Measurement Unit (PMU) placed at a bus to sample at a fast rate the voltage and current phasors of that bus) various schemes for placing PMU's are considered and evaluated. These schemes include coherency based methods and pilot point placement techniques for system controllability. A novel scheme is proposed which places a minimal set of PMU's so as to make the system measurement model observable, and thereby linear. This placement scheme is derived from the topological observability theory. It concerns the building of a spanning measurement sub-graph across the system with actual or pseudo-measurement assigned to each of its branches. The minimal PMU set is found through a dual search algorithm which uses both a modified bisecting search and a simulated annealing-based method. The former fixes the number of PMU's while the latter look for a placement set that leads to an observable network. In order to accelerate the procedure, an initial PMU placement is provided by a graph-theoretic procedure which builds a spanning measurement sub-graph according to a depth-first search. From computer simulation results performed on various test systems, it appears that only one fourth of the system buses need to be provided with PMU's in order to make the system observable. In an effort to reduce the computing time of transient stability assessment, a dynamic equivalent is presented, which results from the elimination of the load buses provided with voltage--dependent loads. The elimination is performed through a new version of the Ward equivalencing method. In this approach, the equivalent current injections are expressed in terms of the retained bus angles and a sensitivity matrix. The non-linearity of the load flow model is accounted for through piecewise linear approximations by updating the sensitivity matrix whenever the operating point moves beyond the validity of the linearization. The expressions of the incremental changes in the generator electric power is derived. The study also investigates the possibility of using the telemetered data provided by the PMU's during pre-fault and post-fault operating conditions in conjunction with a. new version of the Extended Equal Area Criterion (EEAC) method. The latter is able to handle complex loads through the dynamic Ward equivalencing method. The performance of the approach is illustrated on three test systems which have been reduced to the internal generator nodes. / Ph. D.

CAPES / Este trabalho tem por objetivo o desenvolvimento de uma arquitetura de baixo custo para construção de unidades de medição fasorial sincronizada (PMU). O dispositivo prevê conexão com a baixa tensão da rede elétrica, de forma que, instalada neste ponto do sistema permita o monitoramento da rede de transmissão e distribuição. Os desenvolvimentos deste projeto contemplam uma arquitetura completa, com módulo de instrumentação para uso na baixa tens˜ao da rede, módulo GPS para fornecer o sinal de sincronismo e etiqueta de tempo das medidas, unidade de processamento com sistema de aquisição, estimação de fasores e formatação dos dados de acordo com a norma e, por fim, módulo de comunicação para transmissão dos dados. Para o desenvolvimento e avaliação do desempenho da arquitetura, desenvolveu-se um conjunto de aplicativos em ambiente LabVIEW com funcionalidades específicas que permitem analisar o comportamento das medidas e identificar as fontes de erro da PMU, além de aplicar todos os testes previstos pela norma IEEE C37.118.1. O primeiro aplicativo, útil para o desenvolvimento da instrumentação, consiste em um gerador de funções integrado com osciloscópio, que permite a geração e aquisição de sinais de forma sincronizada, além da manipulação das amostras. O segundo e principal deles, é a plataforma de testes capaz de gerar todos os ensaios previstos pela norma, permitindo também armazenar os dados ou fazer a análise das medidas em tempo real. Por fim, um terceiro aplicativo foi desenvolvido para avaliar os resultados dos testes e gerar curvas de ajuste para calibração da PMU. Os resultados contemplam todos os testes previstos pela norma e um teste adicional que avalia o impacto de ruído. Além disso, através de dois protótipos conectados à instalação elétrica de consumidores de um mesmo circuito de distribuição, obteve-se registros de monitoramento que permitiram a identificação das cargas no consumidor, análise de qualidade de energia, além da detecção de eventos a nível de distribuição e transmissão. / This work presents a low cost architecture for development of synchronized phasor measurement units (PMU). The device is intended to be connected in the low voltage grid, which allows the monitoring of transmission and distribution networks. Developments of this project include a complete PMU, with instrumentation module for use in low voltage network, GPS module to provide the sync signal and time stamp for the measures, processing unit with the acquisition system, phasor estimation and formatting data according to the standard and finally, communication module for data transmission. For the development and evaluation of the performance of this PMU, it was developed a set of applications in LabVIEW environment with specific features that let analyze the behavior of the measures and identify the sources of error of the PMU, as well as to apply all the tests proposed by the standard. The first application, useful for the development of instrumentation, consists of a function generator integrated with an oscilloscope, which allows the generation and acquisition of signals synchronously, in addition to the handling of samples. The second and main, is the test platform, with capabality of generating all tests provided by the synchronized phasor measurement standard IEEE C37.118.1, allowing store data or make the analysis of the measurements in real time. Finally, a third application was developed to evaluate the results of the tests and generate calibration curves to adjust the PMU. The results include all the tests proposed by synchrophasors standard and an additional test that evaluates the impact of noise. Moreover, through two prototypes connected to the electrical installation of consumers in same distribution circuit, it was obtained monitoring records that allowed the identification of loads in consumer and power quality analysis, beyond the event detection at the distribution and transmission levels.