André Morelato França

Análise comparativa entre geradores síncronos e geradores de indução com rotor tipo gaiola de esquilo para aplicação em geração distribuída

This paper presents a detailed comparative analysis between synchronous and induction machines for distributed generation applications. The impacts of these generators on the performance of distribution networks are determined and compared by using different computational simulation tools and models.The technical factors analyzed are steady state voltage profile, electrical losses, voltage stability, transient stability, voltage sags due to unbalanced faults and short-circuit currents. The results show that the most suitable choice depends on the network technical characteristics, i.e. what are the main operating restrictions related to distributed generation.

Modelagem e análise dinâmica de dispositivos DSTATCOM usando o SimPowerSystems para Matlab/Simulink

This work presents a study about dynamic modeling and analysis of DSTATCOM (Distribution Static Synchronous Compensator) devices. The objectives are to analyze the dynamic performance of these devices and mainly present simplified and detailed models. Such study is carried out utilizing the SimPowerSystems for use with Matlab/Simulink. The paper is written as a tutorial, thus, all necessary information to implement the models is explicitly presented. Two application examples of the models developed are discussed. In the first one, the detailed model model is employed to evaluate the influence of the capacitor size on the harmonic generation, whereas a study about the influence of a DSTATCOM on the stability performance of induction generators connected to distribution systems is carried out using the simplified model.

Análise comparativa sobre a eficácia de relés baseados em medidas de freqüência para detecção de ilhamento de geradores distribuídos

Frequency-based relays are usually employed in anti-islanding protection of synchronous generators connected to distribution systems. Since the relays performances are strongly dependent on the amount of active power imbalance in the islanded system, a set of detection time versus power imbalance curves is employed to evaluate the performance of these relays. Such curves are obtained by non-linear dynamical simulation. The concept of critical active power imbalance is also presented by using these curves. This methodology is applied to analyze under and over-frequency relays, rate of change of frequency relays (ROCOF relays) and vector surge or vector jump relays (VS relays).

Fuzzy rule-based methodology for residential load behaviour forecasting during power systems restoration

Inadequate load pickup during power system restoration can lead to overload and underfrequency conditions, and even restart the blackout process, due to thermal energy losses. Thus, load behaviour estimation during restoration is desirable to avoid inadequate pickups. This work describes an artificial intelligence method to aid the operator in taking decisions during system restoration by estimating residential load behaviour parameters such as overload in buses and the necessary time to recover steady-state power consumption. This method uses a fuzzy rule-based system to forecast the residential load, obtaining correct estimates with low computational cost. Test results using actual substation data are presented.

Modelagem de planos de recomposição de sistemas elétricos como grafos CPM/PERT

This work proposes a computational model based on PERT/CPM graphs to represent power system restoration plans. This model can be automatically derived using the precedence list represented by the restoration actions. This method was successfully applied to a restoration plan developed for a South-Brazilian power network, generating satisfactory results.

Um ano sem Alcir Monticelli (1946-2001)

On August 5th, one year passed since Alcir Monticelli left us. His legacy is very present in power system applications, which was his speciality. Significant improvements in power systems have undergone in the last decades and Alcir Monticelli has importantly taken part of the transformation process with his amazing capacity to interact with the academic area as a professor and also as a researcher working toward practical solutions to the most challenging problems in power systems. In this article, which is an invitation from Revista Controle & Automacao (SBA) to honor the Alcirs memory, we will remember some of his major contributions to the power systems area and also register the recognition of his work worldwide.