Power outage detection methods for theoperation of a shunt active power flter as energy backup system

This paper presents the study of power outage detection methods that can be applied to a Shunt Active Power Filter (SAPF) with energy backup capability. SAPFs can successfully compensate Power Quality problems related with distorted or unbalanced currents and low power factor. Future Smart Grids will combine devices, control strategies and functionalities to increase the grid reliability and the power management capability. One of the main tools necessary to enable these features is the information of what is occurring in all the smart grid parts. In this context the fast detection of power outages is critical, so this paper also contributes for the discussion of the best ways to extract information in the context of future smart grids. The combination of information and flexible devices in a smart grid will enable the implementation of collective awareness systems, which can deal with different electrical grid problems and situations in an organic manner.This work is financed by FEDER Funds, through the Operational Programme for Competitiveness Factors – COMPETE, and by National Funds through FCT – Foundation for Science and Technology of Portugal, under the projects FCOMP 01-0124-FEDER-022674 and PTDC/EEA-EEL/104569/2008. Bruno Exposto is supported by the doctoral scholarship SFRH/BD/87999/2012 granted by FCT – Foundation for Science and Technology of Portugal. 0info:eu-repo/semantics/publishedVersio

Analysis of mismatch and shading effects in a photovoltaic array using different technologies

In this paper, we analyze the performance of a photovoltaic array implemented in the Universidad Politécnica de Valencia which consists of modules of different technologies and power, connected in series, in order to quantify the energy losses due to mismatch and the effect of the shadows. To do this, the performance of the modules was measured in operation under ambient conditions with field measurement equipment (AMPROBE Solar Analyzer, Solar - 4000), which allows the extrapolation of measures to standard conditions STC. For the data validation, measures under controlled conditions were taken to some modules in the flash test laboratory of the Institute of Energy Technology ITE of Valencia in Spain. Subsequently the array curves measured were validated with a photovoltaic array model developed in MATLAB-Simulink for the same conditions and technologies. The results of this particular array are lost up to 20% of the energy supplied due to the modules mismatch. The study shows the curves and the energy loss due to shadows modules. This result opens scenarios for conceivable modifications to the PV field configurations today, chosen during the design stage and unchangeable during the operating stage; and gives greater importance to the energy loss by mismatch in the PV arrayGuerrero, J.; Munoz, Y.; Ibañez Escobar, F.; Ospino, A. (2014). Analysis of mismatch and shading effects in a photovoltaic array using different technologies. IOP Conference Series: Materials Science and Engineering. 59:1-9. doi:10.1088/1757-899X/59/1/012007S1959KAUSHIKA, N., & RAI, A. (2007). An investigation of mismatch losses in solar photovoltaic cell networks. Energy, 32(5), 755-759. doi:10.1016/j.energy.2006.06.017Moschitta, A., Damiani, A., & Carbone, P. (2012). A simple and accurate model for predicting mismatch effects in Photovoltaic Arrays. 2012 IEEE International Energy Conference and Exhibition (ENERGYCON). doi:10.1109/energycon.2012.6348264Spertino, F., & Akilimali, J. S. (2009). Are Manufacturing $I$– $V$ Mismatch and Reverse Currents Key Factors in Large Photovoltaic Arrays? IEEE Transactions on Industrial Electronics, 56(11), 4520-4531. doi:10.1109/tie.2009.2025712ALONSOGARCIA, M., RUIZ, J., & CHENLO, F. (2006). Experimental study of mismatch and shading effects in the – characteristic of a photovoltaic module. Solar Energy Materials and Solar Cells, 90(3), 329-340. doi:10.1016/j.solmat.2005.04.02

INTEGRAL NON-LINEARITY IN MEMORYLESS A/D CONVERTERS

This paper investigates the statistical properties of quantization noise. In particular, a theoretical model is discussed, which evaluates the power of quantization noise introduced by a memoryless Analog to Digital Converter (ADC) as a function of both the converted signal distribution and the ADC thresholds positioning. Expressions have also been derived to express the Integral Non-Linearity (INL) contribution to quantization noise power as an additive term, and to evaluate such a term with a simple formula. Simulation results that validate the proposed expression are provided

Generalized Likelihood Ratio Test for Voltage Dip Detection

An alternative detection algorithm, based on the generalized likelihood ratio test (GLRT), is proposed for the detection of voltage dips in power systems. The proposed method is compared to the classical approaches based on the voltage root mean square. It is shown that the GLRT may provide competitive performance in terms of capability of correctly detecting the dip starting instant. A DSP-based experimental setup for the implementation of the method is also presented

Generalized Likelihood Ratio Test for voltage dip detection

An alternative detection algorithm, based on the generalized likelihood ratio test (GLRT), is proposed for the detection of voltage dips in power systems. The proposed method is compared to the classical approaches based on the voltage root mean square. It is shown that the GLRT may provide competitive performance in terms of capability of correctly detecting the dip starting instant. A DSP-based experimental setup for the implementation of the method is also presented

Performance Comparison of Advanced Techniques for Voltage Dip Detection

Different aspects have to be considered when dealing with voltage dips in electric power systems. As a consequence, according to different needs arising from specific applications, different approaches have been proposed in the literature for the detection and classification of these events. This paper focuses on issues that are critical for the development of real-time compensation systems, namely, the capability of detecting correctly and rapidly the event while avoiding false alarms, and the algorithm complexity. To this purpose, approaches based on voltage root mean square, wavelets, Kalman filtering, peak voltage, missing voltage, and generalized likelihood ratio test are compared by means of computer simulations, by considering different kinds of voltage dips and by taking into account the uncertainty introduced by noise. The results provide meaningful indication on the choice of the most suitable method to be used in the considered applications

Performance comparison of advanced techniques for voltage dip detection

Several different approaches for the detection of voltage dips in electic power systems have been proposed in the literature to overcome the limits of the procedure proposed by the International Standard, based on the voltage root mean square. In this paper the most promising of these approaches are compared, by computer simulations, in terms of both statistical performance and response time, which is a critical issue for the development of real-time compensation systems

Statistical Properties of Voltage Dip Detectors

In this paper, some statistical properties of procedures defined to detect voltage dips in electric power systems are discussed. First, a theoretical model of the root-mean-square based test proposed in the IEC 61000-4-30 is provided and validated. Then, an alternative detection algorithm, based on the Generalized Likelihood Ratio Test (GLRT), is proposed, and compared to the 61000-4-30 test. It is shown that the GLRT may provide competitive performance, in terms of Receiver Operating Characteristic (ROC), if compared to the standardized procedure