In this paper, a Fractional Order Power System controller (FOPSS) is designed, and its performance and robustness are experimentally evaluated by tests in a 10 kVA laboratory scale power system. The FOPSS design methodology is based on the tuning of an additional design variable, namely the fractional order of the controller transfer function. This design variable is tuned aiming to obtain a tradeoff between satisfactory damping of dominant oscillating mode and improved closed-loop system robustness. For controller synthesis, transfer function models were estimated from data collected at selected operating points and subsequently applied for the controller design and for obtaining upper bounds estimates on the operating-point depends on plant uncertainties. The experimental results show that the FOPPS was able to obtain a robust performance for the considered set of the power system operating conditions.

Currently, energy is seen as an essential product, which is quantified through its characteristics, such as quality, price and accessibility. To this end, research involving power quality and in particular the fault detection in the power grid and especially in the presence of distributed generation, has become more intensive for mapping and correcting its operation. In this view this work presents a novel study of a method for detecting short-circuit faults in electricity distribution networks with the presence of renewable distributed generation sources via converters such as solar photovoltaic. The methodology for fault detection and classification proposed in this work is based on the analysis of parametric ARX (autoregressive with external inputs) models obtained by online parametric estimation via recursive least squares. Additionally, a classification system based on fuzzy logic, in view of the continuous change of these parameters values, classifies short-circuit faults in terms of their severity between line to ground fault, line to line fault, three-phase fault and line two line to ground fault. In order to verify the effectiveness of this proposed methodology, exhaustive tests were carried out in computer simulation applied to a typical electrical distribution network of 3 buses, two feeders and a 250 kW photovoltaic (PV) generator. Finally, the results obtained proved the effectiveness of the proposed method, being a fuzzy classification system that was designed capable of proper determining percentage for classification of the detected fault in terms of its severity. Atualmente, a energia é vista como um produto essencial, o qual é quantificada através de suas características, tais como, qualidade, preço e acessibilidade. Para tal, as pesquisas envolvendo a qualidade de energia e em particular a detecção de faltas na rede elétrica, e principalmente na presença de geração distribuída, se tornaram mais intensivas para um mapeamento e correta de sua operação. Em vista disso, este trabalho apresenta o estudo de um método de detecção de faltas do tipo curto-circuito em redes de distribuição de energia elétrica com a presença de fontes de geração distribuída renováveis do tipo solar fotovoltaica. A metodologia para detecção e classificação de faltas proposta neste trabalho é baseada em análise de modelos paramétricos do tipo ARX (auto-regressivo com entradas externas) obtidos através de estimação de parâmetros via mínimos quadrados recursivo. Adicionalmente um sistema baseado em lógica fuzzy em vista da mudança online destes parâmetros classifica as faltas de curto-circuito com relação a sua gravidade entre monofásica, bifásica, trifásica e bifásica à terra. De modo a verificar a efetividade desta metodologia proposta procedeu-se à realização de exaustivos testes em simulação computacional aplicados a uma típica rede de distribuição elétrica de 3 barras, dois alimentadores e um gerador fotovoltaico (PV) de 250 kW. Por fim, os resultados obtidos comprovaram a efetividade do método proposto, sendo sistema de classificação fuzzy que foi projetado capaz de determinar o percentual adequado para classificação da falta detectada quanto a severidade da mesma.

In protection systems, directional relays are usually applied when the electrical system operates in closed loop, acting for faults only in a one direction, in order to optimize protection coordination. This study presents a modeling of a directional relay in Simulink/MatLab™. In the proposed electrical system, two directional relays are located in a 60 km transmission line and interconnected through a remote system. Three case studies are analyzed, in function of the location of the three-phase faults and the activation of the permissive signal for tripping the relays. The results of the actuation times obtained in the simulations showed differences between 0.5 and 5.4% in relation to the calculated values, representing a good approximation of the proposed model in relation to the analytical values.