In a multihop cellular network, mobile terminals have the capability to transmit directly to other mobile terminals enabling them to use other terminals as relays to forward traffic towards the base station. Previous studies of networks consisting of a single cell found that the SINR in a multihop cellular network is slightly lower than in a traditional cellular network. However, multihop cellular networks may have a higher capacity than traditional cellular networks due to their potential for lower intercell interference. For this reason, the effects of intercell interference are investigated in this thesis. Our simulations of a network with many cells show that multihop cellular networks have a higher SINR than traditional cellular networks due to the near elimination of intercell interference. However, multihop cellular networks still suffer from large amounts of interference surrounding the base station because all traffic either emanates or is destined to the base station making it the capacity bottleneck. To resolve this problem, we propose a novel architecture called the autonomous infrastructure multihop cellular network where users can connect their mobile terminals to the backbone network giving them the functionality of an access point. Access points receive traffic from other terminals and send it directly onto the backbone, as would a base station. This reduces the traffic handled by the base station and increases network capacity. Our analysis and simulations show that in autonomous infrastructure multihop cellular networks, the SINR at the base station is higher, the power consumption is lower and the coverage is better than in normal multihop cellular networks. Access points require parameters like their transmission range to be adjusted autonomously to optimal levels. In this thesis, we propose an autonomous pilot power protocol. Our results show that by adjusting a parameter within the protocol, a required coverage level of terminals can be specified and achieved without knowledge of the location or density of mobile terminals. Furthermore, we show that the protocol determines the transmission range that is optimal in terms of SINR and power consumption that achieves the required coverage while effectively eliminating the bottleneck that existed at the base station.

Relés de distância são muito utilizados para proteger linhas de transmissão. Porém, há baixa precisão dos limites de sua zona de proteção devido a fenômenos de subalcance e sobrealcance. Assim, nesta dissertação de mestrado é proposto um algoritmo com compensação da resistência de falta, baseado em coordenadas de fase, objetivando aumentar a precisão dos limites da zona de proteção. A formulação proposta utiliza uma estimativa da corrente de falta para estimar a resistência de falta e compensar a impedância aparente calculada. Foram realizados o equacionamento e desenvolvimento do algoritmo para faltas tipo fase. Simulações e testes numéricos comparativos com formulações estado-da-arte verificaram a eficiência do método proposto. / Distance Relays are widely used to protect transmission lines. However, due to underreaching and overreaching phenomena, there is a low precision in protection zone limits of distance relays. Thus, in this dissertation, a new algorithm based in phase coordinates is proposed to increase the precision in zone protection limits. The proposed method uses the fault corrent to estimate the fault resistance and compensate the apparent impedance calculated. The equation development was done for phase type faults. Comparative tests with state-of-the-art formulations verified the efficiency of the proposed method.

Dispositivos baseados em eletrônica de potência, conhecidos na literatura como Dispositivos FACTS (Flexible AC Transmission Systems) permitem aumentar a capacidade de transmissão diminuindo a margem de segurança necessária para uma operação segura do sistema elétrico de potência (SEP) sem construir novas linhas, permitindo controlar os fluxos nas linhas e assim permitindo que os contratos entre as empresas de transmissão sejam respeitados. Entre os dispositivos FACTS, o de maior versatilidade é o Unified Power Flow Controller (UPFC), capaz de controlar três variáveis do sistema. No entanto, a inclusão desses dispositivos traz outros problemas ao SEP, um deles, a proteção das linhas. Este trabalho apresenta uma contribuição para uma nova formulação matemática, adaptativa e compensada para a proteção de distância baseada na impedância aparente para a proteção de linhas compensadas com dispositivos UPFC. A formulação proposta se baseia em uma modelagem trifásica do sistema e na compensação da impedância aparente calculada através dos parâmetros controlados do UPFC e da estimação da impedância da falta. Resultados obtidos através da simulação exaustiva de faltas, mostram que esta formulação apresenta um excelente desempenho para a proteção de distância de linhas compensadas por dispositivos UPFC. / Power electronics-based devices, known as FACTS devices (Flexible Alternating current Transmission Systems) allow to increase transmission capacity by decreasing the safety margin required for a secure operation of the Electric Power System (EPS). It is possible without need to build new lines, allowing to control the flows in lines and thus allowing contracts between the transmission companies are respected. Among the FACTS devices, the most versatile is the Unified Power Flow Controller (UPFC) capable of controlling three variables of the system. However, the inclusion of these devices brings other problems to the EPS, one of them, the transmission lines protection. This Thesis presents a contribution to a new mathematical formulation, adaptive and compensated for the distance protection based on the apparent impedance to protect transmission lines compensated by UPFC devices. The proposed formulation is based on a three-phase frame reference and the compensation of apparent impedance by the UPFC controlled parameters and the estimation of the fault impedance. Results obtained, through the comprehensive simulation of faults, show that it formulation present excellent performance for distance protection of transmission lines compensated by UPFC devices.

Ce travail est lié au système de protection des réseaux de distribution. Les réseaux radiaux dedistribution peuvent être protégés simplement par une protection placée en tête du départ. Maisl'exploitation future des réseaux de distribution, qui se transforment en réseaux intelligents,flexibles et adaptatifs, va sûrement nécessiter une protégeabilité plus complexe. Parconséquent, un nouveau plan de protection pourrait être nécessaire afin d’augmenter la fiabilitédu réseau de distribution et le taux de productions décentralisées. Il pourrait inclure plusieursprotections déployées sur un départ. Le but principal de ce travail est d'étudier comment lesprotections pourraient agir (sur quel genre de grandeurs les protections reposeront, quellecoordination faut-il choisir) et d'analyser les limites de ces nouvelles protections. En déployantplusieurs protections qui divisent le départ en des zones plus petites, le plan de protectionproposé, reposant sur une formulation modifié et optimisée, proche de celle des protections dedistance classiques, déconnectera ainsi moins de consommateurs et de producteurs lors del’apparition de défauts. Cela devrait réduire le temps de coupures brèves et de diminuerl'énergie non fournie. Ce manuscrit présente une solution pour les réseaux HTA radiaux faceaux défauts monophasés. / This work is related to the protection system of distribution networks. Radial MV distributiongrids can be protected by a single protection relay located at the beginning of the feeder. Butthe future operation mode of distribution grids turning into Smart Grids should impose morecomplex operations. Therefore a more advanced protection scheme could be needed, in orderto improve the reliability of the distribution network and to enhance the DG interconnection. Itcould include several protection relays in series on a same MV feeder. The main purpose of thiswork is to investigate how the protection relays could work (on which measurements should theprotection decisions be based, how to coordinate the relays without communication) andanalyze the limits of such new protection schemes. Since the goal is to insert severalprotections that divide the grid into smaller sections, the proposed protection system, based onan adapted and optimized formula, inspired by distance relays algorithm, would thereforedisconnect fewer loads and producers when faults occur in the MV network. This should reducethe clearing operation time and Energy Not Supplied criteria. This paper presents a solution fora radial MV grid facing single-phased faults.

Relés de distância são muito utilizados para proteger linhas de transmissão. Porém, há baixa precisão dos limites de sua zona de proteção devido a fenômenos de subalcance e sobrealcance. Assim, nesta dissertação de mestrado é proposto um algoritmo com compensação da resistência de falta, baseado em coordenadas de fase, objetivando aumentar a precisão dos limites da zona de proteção. A formulação proposta utiliza uma estimativa da corrente de falta para estimar a resistência de falta e compensar a impedância aparente calculada. Foram realizados o equacionamento e desenvolvimento do algoritmo para faltas tipo fase. Simulações e testes numéricos comparativos com formulações estado-da-arte verificaram a eficiência do método proposto. / Distance Relays are widely used to protect transmission lines. However, due to underreaching and overreaching phenomena, there is a low precision in protection zone limits of distance relays. Thus, in this dissertation, a new algorithm based in phase coordinates is proposed to increase the precision in zone protection limits. The proposed method uses the fault corrent to estimate the fault resistance and compensate the apparent impedance calculated. The equation development was done for phase type faults. Comparative tests with state-of-the-art formulations verified the efficiency of the proposed method.

Dispositivos baseados em eletrônica de potência, conhecidos na literatura como Dispositivos FACTS (Flexible AC Transmission Systems) permitem aumentar a capacidade de transmissão diminuindo a margem de segurança necessária para uma operação segura do sistema elétrico de potência (SEP) sem construir novas linhas, permitindo controlar os fluxos nas linhas e assim permitindo que os contratos entre as empresas de transmissão sejam respeitados. Entre os dispositivos FACTS, o de maior versatilidade é o Unified Power Flow Controller (UPFC), capaz de controlar três variáveis do sistema. No entanto, a inclusão desses dispositivos traz outros problemas ao SEP, um deles, a proteção das linhas. Este trabalho apresenta uma contribuição para uma nova formulação matemática, adaptativa e compensada para a proteção de distância baseada na impedância aparente para a proteção de linhas compensadas com dispositivos UPFC. A formulação proposta se baseia em uma modelagem trifásica do sistema e na compensação da impedância aparente calculada através dos parâmetros controlados do UPFC e da estimação da impedância da falta. Resultados obtidos através da simulação exaustiva de faltas, mostram que esta formulação apresenta um excelente desempenho para a proteção de distância de linhas compensadas por dispositivos UPFC. / Power electronics-based devices, known as FACTS devices (Flexible Alternating current Transmission Systems) allow to increase transmission capacity by decreasing the safety margin required for a secure operation of the Electric Power System (EPS). It is possible without need to build new lines, allowing to control the flows in lines and thus allowing contracts between the transmission companies are respected. Among the FACTS devices, the most versatile is the Unified Power Flow Controller (UPFC) capable of controlling three variables of the system. However, the inclusion of these devices brings other problems to the EPS, one of them, the transmission lines protection. This Thesis presents a contribution to a new mathematical formulation, adaptive and compensated for the distance protection based on the apparent impedance to protect transmission lines compensated by UPFC devices. The proposed formulation is based on a three-phase frame reference and the compensation of apparent impedance by the UPFC controlled parameters and the estimation of the fault impedance. Results obtained, through the comprehensive simulation of faults, show that it formulation present excellent performance for distance protection of transmission lines compensated by UPFC devices.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Em comunicaÃÃes cooperativas, dois ou mais terminais de transmissÃo sÃo combinados para aumentar a diversidade e/ou a potencia dos sinais que chegam a um determinado receptor. Portanto, mesmo que os dispositivos nÃo disponham de mais de uma antena, ou que entÃo haja uma grande perda por propagaÃÃo entre dois pontos comunicantes, os diversos elementos transmissores podem atuar como um arranjo virtual de antenas, obtendo-se assim vantagens dos sistemas de mÃltiplas antenas (MIMO), sobretudo o aumento da capacidade de transmissÃo. Recentemente, a chamada analise tensorial tem se mostrado uma abordagem eficiente entÃo para a estimaÃÃo de canais em sistemas com diversidade cooperativa. Contudo, nos poucos trabalhos dedicados a essa tarefa, a utilizaÃÃo da decomposiÃÃo tensorial PARAFAC para a modelagem dos sinais recebidos nÃo possibilitou o desenvolvimento de tÃcnicas de estimaÃÃo conjunta de canais e sÃmbolos. Com a idÃia de se evitar o uso de sequencias de treinamento, que limita a eficiÃncia espectral da transmissÃo por dedicar uma parte da largura de banda apenas para a tarefa de estimaÃÃo dos canais, o objetivo desta tese à prover novas estratÃgias de comunicaÃÃo, em termos de sistemas de transmissÃo e receptores semi-cegos, baseados em tensores adaptados a sistemas cooperativos MIMO unidirecionais de dois saltos. Dois sistemas de transmissÃo sÃo propostos utilizando uma codificaÃÃo espaÃo-temporal do tipo Khatri-Rao na fonte e duas estrategias de processamento Amplify-and-Forward (AF) no relay. Para estes sistemas, nomeados PT2-AF e NP-AF, os sinais recebidos no chamado nà de destino satisfazem os modelos tensoriais do tipo PARATUCK2 e Nested PARAFAC. Explorando as propriedades de unicidade destes modelos tensoriais estabelecidas nesta tese, vÃrios receptores semi-cegos sÃo derivados. Alguns destes receptores sÃo do tipo ALS, enquanto outros sÃo de soluÃÃes baseadas na factorizaÃÃo de produtos de Khatri-Rao. Resultados de simulaÃÃo sÃo apresentados para ilustrar os desempenhos dos receptores propostos em comparaÃÃo a alguns estimadores supervisionados. / In cooperative communication systems, two or more transmitting terminals are combined to increase the diversity and/or the power of the signals arriving at a particular receiver. Therefore, even if the devices do not have more than one antenna, or if a significant propaga- tion loss is present between the two communicating nodes, the various transmitting elements can act as a virtual antenna array, thus obtaining the benefits of the multiple antenna (MIMO) systems, especially the increase in the capacity. Recently, tensor decompositions have been introduced as an efficient approach for channel estimation in cooperative com- munication systems. However, among the few works devoted to this task, the utilization of the PARAFAC tensor decomposition for modeling the received signals did not allow the development of techniques for joint symbol and channel estimation. Aiming to avoid the use of pilot sequences, which limits the overall spectral efficiency by dedicating a portion of the bandwidth only for the channel estimation task, the objective of this thesis is to provide new tensor-based strategies, including transmission systems and semi-blind receivers, for one-way two-hop MIMO relaying systems. Based on a Khatri-Rao space-time coding at the source and two different Amplify-and-Forward (AF) relaying strategies, two transmission schemes are proposed. For these systems, named PT2-AF and NP-AF, the received signals at the destination node follow respectively a PARATUCK2 and a nested PARAFAC tensor model. Exploiting uniqueness properties of these tensor models which are established in the thesis, several semi-blind receivers are derived. Some of these receivers are of iterative form us- ing an ALS algorithm, whereas some other ones have closed-form solutions associated with Khatri-Rao factorizations. Some simulation results are finally presented to illustrate the per- formance of the proposed receivers which are compared to some state-of-the-art supervised techniques.

Dispositivos baseados em eletrônica de potência, conhecidos na literatura como Dispositivos FACTS (Flexible AC Transmission Systems) permitem aumentar a capacidade de transmissão diminuindo a margem de segurança necessária para uma operação segura do sistema elétrico de potência (SEP) sem construir novas linhas, permitindo controlar os fluxos nas linhas e assim permitindo que os contratos entre as empresas de transmissão sejam respeitados. Entre os dispositivos FACTS, o de maior versatilidade é o Unified Power Flow Controller (UPFC), capaz de controlar três variáveis do sistema. No entanto, a inclusão desses dispositivos traz outros problemas ao SEP, um deles, a proteção das linhas. Este trabalho apresenta uma contribuição para uma nova formulação matemática, adaptativa e compensada para a proteção de distância baseada na impedância aparente para a proteção de linhas compensadas com dispositivos UPFC. A formulação proposta se baseia em uma modelagem trifásica do sistema e na compensação da impedância aparente calculada através dos parâmetros controlados do UPFC e da estimação da impedância da falta. Resultados obtidos através da simulação exaustiva de faltas, mostram que esta formulação apresenta um excelente desempenho para a proteção de distância de linhas compensadas por dispositivos UPFC. / Power electronics-based devices, known as FACTS devices (Flexible Alternating current Transmission Systems) allow to increase transmission capacity by decreasing the safety margin required for a secure operation of the Electric Power System (EPS). It is possible without need to build new lines, allowing to control the flows in lines and thus allowing contracts between the transmission companies are respected. Among the FACTS devices, the most versatile is the Unified Power Flow Controller (UPFC) capable of controlling three variables of the system. However, the inclusion of these devices brings other problems to the EPS, one of them, the transmission lines protection. This Thesis presents a contribution to a new mathematical formulation, adaptive and compensated for the distance protection based on the apparent impedance to protect transmission lines compensated by UPFC devices. The proposed formulation is based on a three-phase frame reference and the compensation of apparent impedance by the UPFC controlled parameters and the estimation of the fault impedance. Results obtained, through the comprehensive simulation of faults, show that it formulation present excellent performance for distance protection of transmission lines compensated by UPFC devices.

Relés de distância são muito utilizados para proteger linhas de transmissão. Porém, há baixa precisão dos limites de sua zona de proteção devido a fenômenos de subalcance e sobrealcance. Assim, nesta dissertação de mestrado é proposto um algoritmo com compensação da resistência de falta, baseado em coordenadas de fase, objetivando aumentar a precisão dos limites da zona de proteção. A formulação proposta utiliza uma estimativa da corrente de falta para estimar a resistência de falta e compensar a impedância aparente calculada. Foram realizados o equacionamento e desenvolvimento do algoritmo para faltas tipo fase. Simulações e testes numéricos comparativos com formulações estado-da-arte verificaram a eficiência do método proposto. / Distance Relays are widely used to protect transmission lines. However, due to underreaching and overreaching phenomena, there is a low precision in protection zone limits of distance relays. Thus, in this dissertation, a new algorithm based in phase coordinates is proposed to increase the precision in zone protection limits. The proposed method uses the fault corrent to estimate the fault resistance and compensate the apparent impedance calculated. The equation development was done for phase type faults. Comparative tests with state-of-the-art formulations verified the efficiency of the proposed method.

Nowadays two main types of protection schemes widely used in protection of transmission lines are: distance protection and differential protection schemes. However, it has been noticed from industrial practice that the distance protection scheme used today generally is limited in tripping speed and selectivity. Also differential protection scheme is influenced by the time synchronization of samples in both relays installed at transmission line terminals. On the other hand, among various pilot protection schemes for protection of Extra High Voltage (EHV) / Ultra High Voltage (UHV) transmission lines, the schemes which use communication link only for exchange of local decision making about faults’ status are not affected by time synchronization. This master thesis is dealing with the issue of developing reliable and fast fault detection scheme for protection of EHV/UHV transmission lines which is a requirement in modern power systems. The protection algorithm proposed in this thesis is based on the detection and analysis of traveling waves on transmission lines at inception of the faults. This algorithm relies on directional comparison between initial arrivals of traveling waves at each end of the protected line. This will determine whether or not a fault is inside the protected zone. In addition to, based on high voltage transmission network protection requirements proper phase selection algorithm is developed to handle single- phase tripping. Finally, by simulations carried out in PSCAD environment practical design considerations for implementing the new developed protection algorithm in a numerical relay unit is investigated. The results of simulation show that the proposed pilot protection scheme solves several issues encountered by using the conventional schemes and provide reliable and high speed protection for transmission lines.