José César de Souza Almeida Neto

Ensuring the safety and reliability of photovoltaic (PV) installations requires accurate electrical arc fault detection. This work presents a computational arc fault detection framework that combines fixed-length windowing, Fast Fourier Transform (FFT)-based features, and supervised machine learning classifiers. Data were acquired using an Arc Fault Circuit Interrupter (AFCI) test bench developed based on IEC 63027. Current and voltage signals were partitioned into 200-sample windows, DC-offset corrected, and Hann-windowed signals. Each window generated 204 statistical and spectral attributes used to train and evaluate Random Forest (RF), K-Nearest Neighbors (KNN), Multilayer Perceptron (MLP), and Convolutional Neural Network (CNN) models. Hyperparameters were tuned by grid search with TimeSeriesSplit cross-validation, comparing min–max normalization and Z–Score standardization. On a 15% hold-out test set, CNN with Z–Score achieved F1 = 0.9982 and recall = 0.9975, followed by MLP (F1 = 0.9957) and RF (F1 = 0.9821). Amortized per-window inference latencies were ≈0.0035 ms for RF, ≈0.0016 ms for MLP with Z–Score, and ≈0.032 ms for CNN. These classifier-stage timings indicate computational compatibility with edge-oriented implementation but do not constitute an end-to-end IEC 63027 AFCI compliance assessment. The framework targets integration into PV inverters at Mackenzie Presbyterian University’s solar plant.

Transmission flexibility is a key component of current power systems and demands a reconfiguration of alternatives to expand transmission infrastructure. This paper addresses the use of a Battery Energy Storage System (BESS) as an asset of the transmission system that provides increased transmission capacity. Furthermore, the BESS also supports operational procedures of the transmission system in the course of the re-establishment of normal operation during transients, which helps maintain the power quality requirements. A case study is presented to assess the additional capabilities that an operational 30 MW/60 MWh BESS primarily used to provide congestion relief in the state of São Paulo, Brazil, could provide to the power system. Based on a 5-year horizon transmission and generation expansion plans by local governing bodies, a set of four alternative applications for this BESS was proposed and studied, as follows: (1) increased operational flexibility under contingencies and maintenance, (2) islanded operation for increased reliability, (3) grid support during system restoration, and (4) increased hosting capacity for variable renewables. The results show that the BESS improves performance and power quality indexes while aiding the operation during contingencies.

Many remote, isolated communities rely on diesel generators to meet their electrical demands because connecting to conventional electrical grids is either too expensive or technically impractical. In such situations, microgrids made up of diesel gensets and renewable energy sources are most appropriate. However, when diesel generators operate with reduced operating reserve margins, these isolated systems do not have sufficient capacity to withstand large electrical transients, which can lead to instability. As a result, a more detailed evaluation of acceptable levels of renewable energy penetration is required. Hence, the focus of this work is to develop a high-fidelity model for small three-phase diesel generators (SDG), incorporating adaptations to the traditional IEEE Exciter and the Woodward Diesel Engine-Governor Model, with the goal of enhancing the accuracy of dynamic frequency and voltage responses. The effectiveness of the proposed SDG model is validated using field test data of a three-phase genset of 40 kVA–220 V that is part of an operational microgrid. The results show that the accuracy of the proposed model is satisfactory, presenting Normalized Mean Squared Error (NMSE) values around 16% and 10% for speed and voltage responses, respectively.

In cases of severe injuries or burns, skin grafts (scaffolds) are often required as skin substitutes. In order not to harm the patient or the donor, biodegradable and biocompatible materials are used, which validates the search for heterografts such as poly (L-lactic acid)—PLA. However, natural polymers applied to the skin suffer great degradation in environments with large amounts of carbon and water or via binders with considerable resistivity, which implies little durability due to their low ductility. For the proposal, this work investigates PLA-based scaffolds modified with a mixture of pseudoboehmite (PB) and graphene oxide (GO), produced via the sol–gel route. The nanomaterials are incorporated into the polymer at different loadings, seeking to improve mechanical and thermal properties. Analyses via SEM, EDS, and XRD confirm the presence and distribution of these fillers. Tensile and flexural tests indicate that adding the filler can increase stress resistance, prevent deformations before failure, and increase toughness when compared to pure PLA.

The National Institute of Metrology, Quality and Technology (Instituto Nacional de Metrologia, Qualidade e Tecnologia - INMETRO) introduces that, starting in 2024, all photovoltaic (PV) inverters sold in the Brazilian market must incorporate an Arc-Fault Circuit Interrupt (AFCI) function into their systems. These inverters are required to comply with the IEC 63027:2023 (Photovoltaic power systems DC arc detection and interruption) standard. Considering this, the Electrical Engineering Laboratory at Mackenzie Presbyterian University (Universidade Presbiteriana Mackenzie UPM) conducted a series of arc-faults tests on three inverters available in the market, following the IEC 63027 standard. Each of the three inverters underwent a total of 32 arcs, considering number of Maximum Power Point Tracking (MPPT) ports, different impedance topologies, arc position in the PV system, and maximum values of voltage and current. The experiments revealed that two of the three inverters are not capable of meeting the international standard for detecting and interrupting series arc-faults, highlighting the need evaluation of PV inverter sold in the Brazilian market. During the analysis, it was noted that for certain parameters proposed by IEC 63027, there is a gap of information regarding evaluation of the data relating to arc self-extinguish or actual AFCI intervention. It is show that this scenario can raise a concern: the possibility exists for an inverter meet the international standard without implementing an effective AFCI technology. The 96 tests conducted were compared in terms of arc detection time and arc energy. The data were analyzed and compared with respect to the phenomena of arc self-extinguishing and the operation of the AFCI. Suggestions for enhancements to the IEC 63027 standard were provided