http://hdl.handle.net/10174/905 2026-04-03T23:40:19Z http://hdl.handle.net/10174/33712 Title: Low-Cost Multi-Frequency Eddy Current Coating Thickness Measurement System Authors: Santos, Ana C.; Barrancos, André; Rosado, Luís S.; Janeiro, Fernando M. Abstract: A low-cost coating thickness gauge based on Eddy Current Testing (ECT) is reported in this paper. This measurement system employs a Direct Digital Synthesizer (DDS) to generate pure sinusoidal stimulus applied to a measurement coil whose impedance varies with the measured coating thickness. The coil current and voltage are digitally acquired using an ARM Cortex M4F microcontroller where sine-fitting digital signal processing algorithms are applied to estimate the coil inductance and resistivity at different operation frequencies. Post-processing implements a simple multi-frequency estimate algorithm providing accuracy improvements around 10% when compared with the use of a single frequency. 2022-06-30T23:00:00Z http://hdl.handle.net/10174/30836 Title: Low-Cost Embedded Measurement System for Power Quality Frequency Monitoring Authors: Rodrigues, Nuno M.; Janeiro, Fernando M.; Ramos, Pedro M. Abstract: Power quality (PQ) analysis involves the measurement of quantities that characterize the power grid. However, since traditional monitoring equipment is expensive, the measurements are typically performed at few selected locations, not on a regular basis and typically to address customer or grid problems. Recent advances in power electronics combined with the increasing penetration of renewable energies have increased the need for cheaper and portable power quality devices. One of the key parameters in power quality assessment is the power grid frequency since many of the other PQ parameters depend on the power grid frequency. The method suggested in IEC 61000-4-30 to measure the power grid frequency is to count the number of zero crossings in the voltage waveform that occur during a known time interval. In this paper, a new electrical power grid frequency estimation algorithm based in selected calculation of frequency components using the Goertzel algorithm and implemented in a low-cost STM-32 development board is presented. The proposed solution is suited for wide deployment in a smart grid for comprehensive power grid monitoring. 2020-06-30T23:00:00Z http://hdl.handle.net/10174/30821 Title: MATHEMATICAL MODELLING AND SIMULATION TECHNIQUES REVIEW FOR HYBRID PHTOVOLTAIC THERMAL SYSTEM Authors: Ahmed, Md Tofael; Rashel, Masud R.; Janeiro, Fernando M.; Tlemçani, Mouhaydine Abstract: In this work, solar hybrid photovoltaic thermal (PVT) panel’s different mathematical modelling and simulation techniques are described. Mathematical and thermal model development and simulation technique is considered as the initial conditions to simulate the system’s behavior. This article discusses about improved modelling and implementation technique of hybrid PVT technology to enhance the panels effective efficiency by increasing energy output. Characterization and parameters identification including sensitivity analysis by using adapted numerical methods is studied and analyzed. Different types of simulation models are analyzed to established by studying mathematical, thermal and physical model with advance computational tool. 2021-03-01T00:00:00Z http://hdl.handle.net/10174/30708 Title: Influence of Weather Conditions in Power Quality Events Authors: Rodrigues, Nuno M.; Janeiro, Fernando M.; Ramos, Pedro M. Abstract: Power quality (PQ) analysis requires the measurement of electrical quantities that characterize the power supply waveforms such as RMS value, frequency, unbalances, harmonic and inter-harmonic distortion or the presence of transients. The measurement of these quantities is regulated by internationally accepted standards from IEEE and IEC. Monitoring the delivered power quality is even more important due to the recent advances in power electronics and also the ever increasing penetration of renewable energies. Power quality measurements are typically performed at select locations, and not on a regular basis, usually to settle disputes between utility companies and consumers. With the increasing integration of renewable energy sources (RES) in the electrical power grid, the uncertainty in the available power capacity rises. In fact, the dependence of the power generated on weather conditions increases with the share of RES in the electrical grid. Additionally, this uncertainty is also affected by the consumer side, as electricity consumption is also weather-dependent and every kWh produced must be consumed somewhere. This paper presents a study relating PQ events, acquired with a PQ analyzer developed by the Instrumentation and Measurement Group (GIM) at Instituto de Telecomunicações (IT), with weather conditions acquired at Beja Airport. 2020-06-30T23:00:00Z