Estrategias para una medida precisa del flicker provocado por aerogeneradores

195 p.La generación eólica, como fuente de energía renovable, ha experimentado un gran crecimiento en las últimas décadas. La integración en la red de dicha energía implica un importante desafío desde el punto de vista de la calidad de suministro eléctrico. El estándar IEC 61400-21 busca proporcionar una metodología uniforme para la evaluación de las características de calidad de suministro de los aerogeneradores conectados a la red. Esta tesis centra su estudio en el procedimiento de medida de las fluctuaciones de tensión o flicker que se especifica en dicho estándar.El estándar deja un excesivo margen al empleo de distintos criterios para el diseño e implementación digital del procedimiento de medida. Esto genera importantes divergencias en los resultados obtenidos por distintas implementaciones del procedimiento ante las mismas señales de entrada. El estudio realizado revela que el origen de las divergencias está en el primer bloque del procedimiento denominado red ficticia. En concreto, en las dos tareas de procesado digital de señal involucradas en él: la estimación de la fase instantánea de la componente fundamental de la tensión y la derivada de la corriente.Con respecto a la tarea de estimación de la fase instantánea, el trabajo demuestra que es necesario realizar un prefiltrado paso banda para eliminar las perturbaciones de la tensión. Además, se recomienda que la estrategia de filtrado no introduzca distorsión de fase sobre la tensión. Con respecto a la tarea de derivación de la corriente se resaltan varios aspectos sensibles para su implementación digital: por un lado, el retardo de medio periodo de muestreo que introducen los derivadores de longitud par y, por otro, la importancia de asegurar un comportamiento derivador en el ancho de banda de la corriente

Flicker Characteristics of Efficient Lighting Assessed by the IEC Flickermeter

We present an experimental study of the behavior of modern lighting technologies under supply voltage fluctuations. Some studies have reported that flicker severity measurements could exceed the compatibility levels without leading to flicker complaints when modern lighting is in use. Such conclusions have resulted in two main proposals regarding the assessment of flicker: to relax the flicker compatibility indexes and to adapt standardized procedures to assess flicker based on a new reference lamp instead of the current reference, the incandescent lamp. Our work presents alternative tools for analyzing the effect of efficient lighting on the assessment of flicker. Our main findings challenge the assumption that efficient modern lighting is not sensitive to voltage fluctuations, at least over a considerable frequency range. Furthermore, the results oppose the use of the standardized functional model of the incandescent lamp for assessing the flicker severity produced by modern lamps.This work received financial support from the Government of Basque Country through the PhD studentship BFI-2012-315 and from the University of the Basque Country UPV/EHU through the project UFI11/16 and the PhD studentship PIF2011/169

Experimental Study of the Response of Efficient Lighting Technologies to Complex Voltage Fluctuations

The replacement of incandescent lamps with more energy-efficient lighting technologies has a direct influence on the way flicker is measured. The International Electrotechnical Commission (IEC) established in the 61000-4-15 standard the functional specifications of a flickermeter, taking a standard incandescent lamp’s response to voltage fluctuations as the reference. During the past ten years, different works have studied the sensitivity of modern lamps to analytical voltage fluctuations of low complexity. From these studies, the most widespread conclusion is that modern lamps are less sensitive to flicker than are incandescent lamps. Based on these results, international standardization organizations are currently studying two different possibilities for updating the flicker assessment procedure: adjusting the IEC flickermeter according to a new less sensitive reference lamp, or increasing the established compatibility levels for voltage fluctuations. This work presents for the first time a sensitivity analysis of a set of modern lamps subjected to real voltage signals that are more complex than analytical voltage fluctuations. The obtained results lead to the following conclusions: not all efficient lamps have a lower sensitivity to fluctuations than do incandescent lamps; the response of some lamps depends on the complexity of the input voltage fluctuation; and the response of some lamps in real scenarios, i.e., more complex voltage fluctuations, does not correlate with their response to simple voltage fluctuations

An Alternative Strategy to Improve the Flicker Severity Measurement

The IEC 61000-4-15 standard defines a flickermeter that is universally accepted as the meter used for the objective measurement of a disturbing light flicker. The accurate results provided by the IEC flickermeter under uniform fluctuations stand in contrast with its unpredictable behavior under real conditions when voltage fluctuations are not uniform over time. Under nonuniform fluctuations, the IEC flickermeter can indicate wrong values, and this could explain the absence of users’ complaints at sites where high flicker levels were measured. This work presents a new strategy for flicker measurement that overcomes the deficiencies presented in the IEC flickermeter, properly relating flicker severity values and temporal evolution of the fluctuation. The manuscript describes in detail the functional and design specifications of the new strategy, as well as the results obtained during the validation process in which the IEC flickermeter and the new strategy were subjected to input signals with different temporal fluctuation patterns. The manuscript also presents a comparison between the response of the two strategies to real voltage signals, which are complex and nonuniform in nature. The results confirm the differences between both strategies, despite both meet the same requirements established by the standard.This work received financial support from the Government of the Basque Country through the PhD studentship BFI-2012-315 and from the University of the Basque Country UPV/EHU through the project UFI11/16 and the PhD studentship PIF 2011/169

The Role of Chest Compressions on Ventilation during Advanced Cardiopulmonary Resuscitation

There is growing interest in the quality of manual ventilation during cardiopulmonary resuscitation (CPR), but accurate assessment of ventilation parameters remains a challenge. Waveform capnography is currently the reference for monitoring ventilation rate in intubated patients, but fails to provide information on tidal volumes and inspiration–expiration timing. Moreover, the capnogram is often distorted when chest compressions (CCs) are performed during ventilation compromising its reliability during CPR. Our main purpose was to characterize manual ventilation during CPR and to assess how CCs may impact on ventilation quality. Methods: Retrospective analysis were performed of CPR recordings fromtwo databases of adult patients in cardiac arrest including capnogram, compression depth, and airway flow, pressure and volume signals. Using automated signal processing techniques followed by manual revision, individual ventilations were identified and ventilation parameters were measured. Oscillations on the capnogram plateau during CCs were characterized, and its correlation with compression depth and airway volume was assessed. Finally, we identified events of reversed airflow caused by CCs and their effect on volume and capnogram waveform. Results: Ventilation rates were higher than the recommended 10 breaths/min in 66.7% of the cases. Variability in ventilation rates correlated with the variability in tidal volumes and other ventilatory parameters. Oscillations caused by CCs on capnograms were of high amplitude (median above 74%) and were associated with low pseudo-volumes (median 26 mL). Correlation between the amplitude of those oscillations with either the CCs depth or the generated passive volumes was low, with correlation coefficients of −0.24 and 0.40, respectively. During inspiration and expiration, reversed airflow events caused opposed movement of gases in 80% of ventilations. Conclusions: Our study confirmed lack of adherence between measured ventilation rates and the guideline recommendations, and a substantial dispersion in manual ventilation parameters during CPR. Oscillations on the capnogram plateau caused by CCs did not correlate with compression depth or associated small tidal volumes. CCs caused reversed flow during inspiration, expiration and in the interval between ventilations, sufficient to generate volume changes and causing oscillations on capnogram. Further research is warranted to assess the impact of these findings on ventilation quality during CPR.This research was funded by the grant PID2021-126021OB-I00 by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe, and by the grant IT1590-22 by the Basque Government. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Flicker of Modern Lighting Technologies Due to Rapid Voltage Changes

The purpose of the present paper is to evaluate the sensitivity of modern lighting technologies to different types of RVCs. In order to do that, 27 modern lampsmainly LEDhave been subjected to real RVCs and their response has been assessed. The detection of RVCs on the grid has been performed according to the IEC 61000-4-30 detection method, while the response of the lamps has been measured with a light flickermeter and characterized using the instantaneous flicker perception, as defined in IEC 61000-4-15. The obtained results show a high dispersion in the response of the modern lighting technologies and high values of flicker perception, although with a lower sensitivity than the incandescent lamp. The results led the authors to propose the definition of a new immunity test to be added to the lamp immunity protocol IEC TR-61547-1, to ensure that newly produced lamps cause limited irritation to grid users.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 676042. This work also received financial support from the Spanish MINECO through the project DPI2014-53317-R (cofinanced with the European Regional Development Fund) and from the Basque Government (Basque Country, Spain) through the project IT1087-16

Experimental Study of the Summation of Flicker Caused by Wind Turbines

Integration of wind energy into the grid faces a great challenge regarding power quality. The International Electrotechnical Commission (IEC) 61400-21 standard defines the electrical characteristics that need to be assessed in a Wind Turbine (WT), as well as the procedure to measure the disturbances produced by the WT. One of the parameters to be assessed are voltage fluctuations or flicker. To estimate the flicker emission of a Wind Power Plant (WPP), the standard establishes that a quadratic exponent should be used in the summation of the flicker emission of each WT. This exponent was selected based on studies carried out in WPPs with type I and II WTs. Advances in wind turbine technology have reduced their flicker emission, mainly thanks to the implementation of power electronics for the partial or total management of the power injected into the grid. This work is based on measurements from a WPP with 16 type III WTs. The flicker emission of a single WT and of the WPP were calculated. Low flicker emission values at the Point of Common Coupling (PCC) of the WPP were obtained. The flicker estimation at the PCC, based on the measurement from a single WT, was analyzed using different exponents. The results show that a cubic summation performs better than the quadratic one in the estimation of the flicker emission of a WPP with type III WTs.This research was funded by Basque Government (Basque Country, Spain) through the project IT1087-16 and by the Spanish MINECO through project DPI2014-53317-R (co-financed with European FEDER funds)