Ciro Spataro

A virtual instrument for measurement of flicker

All types of fluctuations of the r.m.s. voltage in power systems may be assessed by using a flickermeter which complies with the specification given in IEC-EN 60868. In this paper a digital flickermeter is presented based on the implementation in the frequency domain of the weighting filter block of the eye-brain simulation chain. The virtual instrument, implemented with an acquisition board inserted on a PC and with a software developed with the LabView tools, samples the voltage and furnishes the instantaneous flicker level and other severity coefficients. Results of simulated and actual data are reported to validate the performances of the developed flickermeter.

ADC based measurements: Identification of the parameters for the uncertainty evaluation

In the last years, many Authors have dealt with the uncertainty evaluation of the measurement performed by using an analog-to-digital converter, proposing different approach to analyze the uncertainty propagation. In all these studies, it is clearly pointed out that starting from the manufacturer specifications is the least expensive, the least time consuming and, often, the most accurate way to assess the uncertainties. However, the Authors, which have proposed methodologies for the uncertainty assessment, use different parameters as starting point. One of the main reasons which has caused this situation is the coexistent of various Standards concerning the characterization of the analog-to-digital converters. Target of the paper is the choice, among the large number of parameters proposed by the various Standards, of a minimum set of figures of merit which allows a correct uncertainty evaluation of a generic measurement performed by using an analog-to-digital converter.

Assessment of virtual instruments measurement uncertainty

Abstract In this paper, two methods to evaluate the measurement uncertainty of a virtual instrument are presented: a numerical method simulating the physical process of the A/D conversion, and an approximated theoretical method applying the “uncertainty propagation law” of the “guide to the expression of uncertainty in measurement”. After a brief description of the features, the constitution and the working principle of the virtual instruments, the various uncertainty sources, are analyzed. With both methods, the combined standard uncertainty of the measurement result is obtained, starting from the standard uncertainty generated by each single source and without taking into account the parameters, which regard the overall behaviour of an acquisition board, such as the effective number of bits. The results obtained by means of the theoretical analysis are compared with the ones obtained from numerical simulation. Then the results of experimental tests on a virtual instrument, with a complex measurement chain for flicker evaluation, are presented.

A PC-Based Wattmeter for Accurate Measurements in Sinusoidal and Distorted Conditions: Setup and Experimental Characterization

This paper presents the development of a high-accuracy sampling wattmeter, which can be employed with both sinusoidal and distorted input signals. The proposed personal computer (PC)-based system is a simple, portable, and low-cost solution because it is based on two commercial data acquisition boards connected to a common PC. Owing to this solution, the voltage is sensed directly, avoiding expensive voltage dividers, while the current is sensed by means of a noninductive current shunt. Commercial software is also used for data processing and implementation of the virtual instrument. The setup of the PC-based wattmeter is described, with a detailed description of the correction strategy of systematic contributions to the measurement uncertainty of analog-to-digital converter conversion. An experimental evaluation of its metrological performances is made by means of several experimental tests, with both sinusoidal and distorted voltages and currents, which were carried out with an electric power standard and a high-performance multifunction calibrator.

A Monte Carlo method for the auto-evaluation of the uncertainties in the analog-to-digital conversion-based measurements

This paper concerns with the measurement uncertainty estimation in the analog‐to‐digital conversion‐based instruments. By using an ad hoc developed software tool, the Monte Carlo method is applied in order to assess the uncertainties associated with the measurement results, overcoming the possible inapplicability of the pure theoretical approach prescribed in the ISO – “Guide to the Expression of Uncertainty in Measurement”. By implementing the software tool in the measurement instruments, the proposed approach can be utilized in order to make the instrument itself able to auto‐estimate the measurement uncertainties.

Piezoelectric model of rainfall energy harvester

In this paper a model to predict the harvest of the energy contained in rainfall by means of piezoelectric transducers is presented. Different studies agree on the level of suitable generated voltage on the electrodes of a piezoelectric transducer subjected to rainfall, but a complete characterization on the supplied power is still missing. This work, in order to limit optimistic forecasts, compares the behavior of the transducers subjected to real and artificial rainfall, a condition that has shown promising behavior in laboratory.

A PC-based wattmeter for high accuracy power measurements

This paper proposes the use of a commercial data acquisition board (DAQ) connected to a common personal computer for high accuracy power measurements. In the paper the set up of the PC-based wattmeter is described and an experimental evaluation of its metrological performances is made by means of the comparison with a simultaneous coherent digital sampling wattmeter realized with two high-precision DMMs Hewlett Packard Model 3458 A. In both cases the power source is a Fluke 6100A/E electrical power standard.

Technical and Economical Evaluation on the Use of Reconfiguration Systems in Some EU Countries for PV Plants

This paper shows the technical and economical evaluation of the application of a reconfiguration system for photovoltaic (PV) plants, considering the incentives system in some European Union countries. The reconfiguration system is an alternative to the distributed maximum power point tracking technique which used to increase the power production in the PV plants under the mismatch phenomenon. The reconfiguration techniques employ a microprocessor-based or field-programmable gate array-based system that modifies the layout of the PV plant through the change of the connections among modules. After having presented the main features working of the PV reconfiguration system allowing the improvement of the efficiency of the same plant and the relevant installation, the main strength and weakness points of the investment are evidenced in relation to different incentives policies in some country of UE.

Economic benefits of the use of a PV plants reconfiguration systems

This paper shows the economic convenience of the application of a reconfiguration system for photovoltaic plants, considering the incentives system in different Countries. The reconfiguration is an alternative to the Distributed Maximum Power Point Tracking, DMPPT, technique used to overcome the mismatch problem in Photovoltaic, PV, plants. The reconfiguration techniques employ a microprocessor-based system that modifies the layout of the PV plant by physically changing the connections among modules. After having presented the working principle of the PV reconfiguration system allowing the improvement of the efficiency of the same plant and the relevant installation, the main strength and weakness points of the investment are evidenced in relation to different incentives policies.

Partial discharges on IGBT modules: Are sinusoidal waveforms sufficient to evaluate behavior?

In recent years, the increasing use of AC-DC converters, especially in the field of renewable energy sources has led to the implementation of new modulation techniques, in particular the ones based on the pulse width modulation. The purpose of the present work is to verify the different behavior that is obtained when the components are subjected to the partial discharge test carried out with a sinusoidal waveform, and when they are subjected to PWM stress-type, similar to the actual signal generated by this type of electronic components. By considering equal rms value of the fundamental sine wave, the comparison has shown different partial discharges patterns.