Power quality analysis involves the measurement of quantities that characterize the power supply ... more Power quality analysis involves the measurement of quantities that characterize the power supply waveforms such as RMS value, frequency, harmonic and inter-harmonic distortion or the presence of transients. The measurement of these quantities is regulated by internationally accepted standards from IEEE or IEC. In particular, for the evaluation of frequency and RMS values, the standard suggests the detection of the waveform zero crossings. Thus, accurate zero crossing detection is of utmost importance in power quality measurements. The undesirable effects of noise, harmonics and transients can be mitigated by filtering of the acquired waveforms, which induces a frequency dependent delay in the processed waveforms. This paper presents a comparative analysis between two types of filters. A comparative analysis is performed between the use of a fixed nominal delay and a frequency corrected delay. Additionally, the effect of the presence of noise and harmonics in the delay compensation is presented.
This paper describes a method to automatically obtain, from a set of impedance measurements at di... more This paper describes a method to automatically obtain, from a set of impedance measurements at different frequencies, an equivalent circuit composed of lumped elements based on the vector fitting algorithm. The method starts from the impedance measurement of the circuit and then, through the recursive use of vector fitting, identifies the circuit topology and the component values of lumped elements. The method can be expanded to include other components usually used in impedance spectroscopy. The method is firstly described and then two examples highlight the robustness of the method and showcase its applicability.
Power quality (PQ) analysis requires the measurement of electrical quantities that characterize t... more 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.
Clouds are important in weather prediction, climate studies and aviation safety. Important parame... more Clouds are important in weather prediction, climate studies and aviation safety. Important parameters include cloud height, type and cover percentage. In this paper, the recent improvements in the development of a low-cost cloud height measurement setup are described. It is based on stereo vision with consumer digital cameras. The cameras positioning is calibrated using the position of stars in the night sky. An experimental uncertainty analysis of the calibration parameters is performed. Cloud height measurement results are presented and compared with LIDAR measurements.
Power quality issues can affect the performance of devices powered by the grid and can, in severe... more Power quality issues can affect the performance of devices powered by the grid and can, in severe cases, permanently damage connected devices. Events that affect power quality include sags, swells, waveform distortions and transients. Transients are one of the most common power quality disturbances and are caused by lightning strikes or switching activities among power-grid-connected systems and devices. Transients can reach very high magnitudes, and their duration spans from nanoseconds to milliseconds. This study proposed a deep-learning-based technique that was supported by convolutional neural networks and a bidirectional long short-term memory approach in order to detect and characterize power-quality transients. The method was validated (i.e., benchmarked) using an alternative algorithm that had been previously validated according to a digital high-pass filter and a morphological closing operation. The training and performance assessments were carried out using actual power-gr...
2020 IEEE 14th International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG)
Power quality (PQ) analysis involves the measurement of quantities that characterize the power gr... more 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.
4 8 9 Abstract - The design, implementation and evaluation of a real-time digital signal processi... more 4 8 9 Abstract - The design, implementation and evaluation of a real-time digital signal processing architecture to 10 generate and process multi-frequency signals for eddy currents testing is described in this paper. This 11
2016 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2016
This paper compares the performance of the complex nonlinear least squares algorithm implemented ... more This paper compares the performance of the complex nonlinear least squares algorithm implemented in the LEVM/LEVMW software with the performance of a genetic algorithm in the characterization of an electrical impedance of known topology. The effect of the number of measured frequency points and of measurement uncertainty on the estimation of circuit parameters is presented. The analysis is performed on the equivalent circuit impedance of a humidity sensor.
2016 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2016
Clouds are important in weather prediction, climate studies and aviation safety. Important parame... more Clouds are important in weather prediction, climate studies and aviation safety. Important parameters include cloud height, type and cover percentage. In this paper, the recent improvements in the development of a low-cost cloud height measurement setup are described. It is based on stereo vision with consumer digital cameras. The cameras positioning is calibrated using the position of stars in the night sky. An experimental uncertainty analysis of the calibration parameters is performed. Cloud height measurement results are presented and compared with LIDAR measurements.
Abstract This paper presents a new planar matrix eddy currents probe intended for non-destructive... more Abstract This paper presents a new planar matrix eddy currents probe intended for non-destructive testing. The proposed design is composed by multiple independent excitation traces and a matrix of independent sensing coils. Finite element modeling is used to highlight the probe operating principle and to preview its behavior in different measurement conditions. Dedicated on-probe electronics were designed to cope with the requirements of the new probe. Multiple pulse generators are used to drive the excitation traces and a multiplexer enables the selection of the different sensing coils being measured. The sensing coils output voltages are amplified, acquired and digitally processed with an FPGA-based embedded device. Processing of the probe response signals to the pulsed excitation is accomplished in the frequency domain using a dedicated FFT core in the FPGA. The proposed probe and electronics system enables two modes of operation. In the first mode, the probe can be operated selecting a combination of excitation traces to drive and sensing coils to read while is being moved on the tested part. In the second mode of operation, the probe is handheld positioned to measure a specific region and a sequence of measurements are triggered by the user. These measurements results can be arranged to form a color map where the defects can be identified.
Power quality issues can affect the performance of devices powered by the grid and can, in severe... more Power quality issues can affect the performance of devices powered by the grid and can, in severe cases, permanently damage connected devices. Events that affect power quality include sags, swells, waveform distortions and transients. Transients are one of the most common power quality disturbances and are caused by lightning strikes or switching activities among power-grid-connected systems and devices. Transients can reach very high magnitudes, and their duration spans from nanoseconds to milliseconds. This study proposed a deep-learning-based technique that was supported by convolutional neural networks and a bidirectional long short-term memory approach in order to detect and characterize power-quality transients. The method was validated (i.e., benchmarked) using an alternative algorithm that had been previously validated according to a digital high-pass filter and a morphological closing operation. The training and performance assessments were carried out using actual power-grid-measured data and events.
Power quality analysis involves the measurement of quantities that characterize the power supply ... more Power quality analysis involves the measurement of quantities that characterize the power supply waveforms such as RMS value, frequency, harmonic and inter-harmonic distortion or the presence of transients. The measurement of these quantities is regulated by internationally accepted standards from IEEE or IEC. In particular, for the evaluation of frequency and RMS values, the standard suggests the detection of the waveform zero crossings. Thus, accurate zero crossing detection is of utmost importance in power quality measurements. The undesirable effects of noise, harmonics and transients can be mitigated by filtering of the acquired waveforms, which induces a frequency dependent delay in the processed waveforms. This paper presents a comparative analysis between two types of filters. A comparative analysis is performed between the use of a fixed nominal delay and a frequency corrected delay. Additionally, the effect of the presence of noise and harmonics in the delay compensation is presented.
This paper describes a method to automatically obtain, from a set of impedance measurements at di... more This paper describes a method to automatically obtain, from a set of impedance measurements at different frequencies, an equivalent circuit composed of lumped elements based on the vector fitting algorithm. The method starts from the impedance measurement of the circuit and then, through the recursive use of vector fitting, identifies the circuit topology and the component values of lumped elements. The method can be expanded to include other components usually used in impedance spectroscopy. The method is firstly described and then two examples highlight the robustness of the method and showcase its applicability.
Power quality (PQ) analysis requires the measurement of electrical quantities that characterize t... more 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.
Clouds are important in weather prediction, climate studies and aviation safety. Important parame... more Clouds are important in weather prediction, climate studies and aviation safety. Important parameters include cloud height, type and cover percentage. In this paper, the recent improvements in the development of a low-cost cloud height measurement setup are described. It is based on stereo vision with consumer digital cameras. The cameras positioning is calibrated using the position of stars in the night sky. An experimental uncertainty analysis of the calibration parameters is performed. Cloud height measurement results are presented and compared with LIDAR measurements.
Power quality issues can affect the performance of devices powered by the grid and can, in severe... more Power quality issues can affect the performance of devices powered by the grid and can, in severe cases, permanently damage connected devices. Events that affect power quality include sags, swells, waveform distortions and transients. Transients are one of the most common power quality disturbances and are caused by lightning strikes or switching activities among power-grid-connected systems and devices. Transients can reach very high magnitudes, and their duration spans from nanoseconds to milliseconds. This study proposed a deep-learning-based technique that was supported by convolutional neural networks and a bidirectional long short-term memory approach in order to detect and characterize power-quality transients. The method was validated (i.e., benchmarked) using an alternative algorithm that had been previously validated according to a digital high-pass filter and a morphological closing operation. The training and performance assessments were carried out using actual power-gr...
2020 IEEE 14th International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG)
Power quality (PQ) analysis involves the measurement of quantities that characterize the power gr... more 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.
4 8 9 Abstract - The design, implementation and evaluation of a real-time digital signal processi... more 4 8 9 Abstract - The design, implementation and evaluation of a real-time digital signal processing architecture to 10 generate and process multi-frequency signals for eddy currents testing is described in this paper. This 11
2016 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2016
This paper compares the performance of the complex nonlinear least squares algorithm implemented ... more This paper compares the performance of the complex nonlinear least squares algorithm implemented in the LEVM/LEVMW software with the performance of a genetic algorithm in the characterization of an electrical impedance of known topology. The effect of the number of measured frequency points and of measurement uncertainty on the estimation of circuit parameters is presented. The analysis is performed on the equivalent circuit impedance of a humidity sensor.
2016 IEEE International Instrumentation and Measurement Technology Conference Proceedings, 2016
Clouds are important in weather prediction, climate studies and aviation safety. Important parame... more Clouds are important in weather prediction, climate studies and aviation safety. Important parameters include cloud height, type and cover percentage. In this paper, the recent improvements in the development of a low-cost cloud height measurement setup are described. It is based on stereo vision with consumer digital cameras. The cameras positioning is calibrated using the position of stars in the night sky. An experimental uncertainty analysis of the calibration parameters is performed. Cloud height measurement results are presented and compared with LIDAR measurements.
Abstract This paper presents a new planar matrix eddy currents probe intended for non-destructive... more Abstract This paper presents a new planar matrix eddy currents probe intended for non-destructive testing. The proposed design is composed by multiple independent excitation traces and a matrix of independent sensing coils. Finite element modeling is used to highlight the probe operating principle and to preview its behavior in different measurement conditions. Dedicated on-probe electronics were designed to cope with the requirements of the new probe. Multiple pulse generators are used to drive the excitation traces and a multiplexer enables the selection of the different sensing coils being measured. The sensing coils output voltages are amplified, acquired and digitally processed with an FPGA-based embedded device. Processing of the probe response signals to the pulsed excitation is accomplished in the frequency domain using a dedicated FFT core in the FPGA. The proposed probe and electronics system enables two modes of operation. In the first mode, the probe can be operated selecting a combination of excitation traces to drive and sensing coils to read while is being moved on the tested part. In the second mode of operation, the probe is handheld positioned to measure a specific region and a sequence of measurements are triggered by the user. These measurements results can be arranged to form a color map where the defects can be identified.
Power quality issues can affect the performance of devices powered by the grid and can, in severe... more Power quality issues can affect the performance of devices powered by the grid and can, in severe cases, permanently damage connected devices. Events that affect power quality include sags, swells, waveform distortions and transients. Transients are one of the most common power quality disturbances and are caused by lightning strikes or switching activities among power-grid-connected systems and devices. Transients can reach very high magnitudes, and their duration spans from nanoseconds to milliseconds. This study proposed a deep-learning-based technique that was supported by convolutional neural networks and a bidirectional long short-term memory approach in order to detect and characterize power-quality transients. The method was validated (i.e., benchmarked) using an alternative algorithm that had been previously validated according to a digital high-pass filter and a morphological closing operation. The training and performance assessments were carried out using actual power-grid-measured data and events.
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