Active and reactive power control of a PV generator for grid code compliance

As new grid codes have been created to permit the integration of large scale photovoltaic power plants into the transmission system, the enhancement of the local control of the photovoltaic (PV) generators is necessary. Thus, the objective of this paper is to present a local controller of active and reactive power to comply the new requirements asked by the transmission system operators despite the variation of ambient conditions without using extra devices. For this purpose, the control considers the instantaneous capability curves of the PV generator which vary due to the change of solar irradiance, temperature, dc voltage and modulation index. To validate the control, the PV generator is modeled in DIgSILENT PowerFactory® and tested under different ambient conditions. The results show that the control developed can modify the active and reactive power delivered to the desired value at different solar irradiance and temperature

Variabilidad de baja frecuencia en los caudales de los ríos del centro-norte de Argentina y su contribución al desarrollo de sequías hidrológicas

Con el propósito de mejorar el conocimiento de la variabilidad temporal de los caudales de los ríos del centro-norte de Argentina en términos de la variabilidad de baja frecuencia, se analizaron los registros mensuales históricos de 10 estaciones de aforo durante el período 1919-2014. A fin de comparar los registros hidrológicos en cuencas con distintas características climáticas y geográficas, se utilizó el índice de caudal estandarizado (ICE), el cual fue obtenido mediante el ajuste de los caudales mensuales a una distribución de probabilidades gamma para luego transformarlos en una variable estandarizada. Mediante una descomposición empírica se obtuvieron los principales modos de variabilidad temporal de los caudales, los cuales abarcan desde la escala estacional a las variaciones multi-decadales, y una tendencia de largo plazo no-lineal. Para el análisis de la variabilidad de baja frecuencia se realizó una composición de los modos que tuvieran periodicidades de 10 o más años. Los resultados muestran que la variabilidad climática juega un papel fundamental, modulando las variaciones de los períodos de sequía hidrológica en diversas escalas de tiempo, lo cual se identificó a través de las tendencias observadas en el último siglo. Estas variaciones de baja frecuencia imponen condiciones de clima noestacionario, lo cual debe tenerse en cuenta para lograr una gestión de riesgos efectiva.Eje: Ciencias de la Atmósfera y los Océanos.Facultad de Ciencias Astronómicas y Geofísica

Variabilidad de baja frecuencia en los caudales de los ríos del centro-norte de Argentina y su contribución al desarrollo de sequías hidrológicas

Con el propósito de mejorar el conocimiento de la variabilidad temporal de los caudales de los ríos del centro-norte de Argentina en términos de la variabilidad de baja frecuencia, se analizaron los registros mensuales históricos de 10 estaciones de aforo durante el período 1919-2014. A fin de comparar los registros hidrológicos en cuencas con distintas características climáticas y geográficas, se utilizó el índice de caudal estandarizado (ICE), el cual fue obtenido mediante el ajuste de los caudales mensuales a una distribución de probabilidades gamma para luego transformarlos en una variable estandarizada. Mediante una descomposición empírica se obtuvieron los principales modos de variabilidad temporal de los caudales, los cuales abarcan desde la escala estacional a las variaciones multi-decadales, y una tendencia de largo plazo no-lineal. Para el análisis de la variabilidad de baja frecuencia se realizó una composición de los modos que tuvieran periodicidades de 10 o más años. Los resultados muestran que la variabilidad climática juega un papel fundamental, modulando las variaciones de los períodos de sequía hidrológica en diversas escalas de tiempo, lo cual se identificó a través de las tendencias observadas en el último siglo. Estas variaciones de baja frecuencia imponen condiciones de clima noestacionario, lo cual debe tenerse en cuenta para lograr una gestión de riesgos efectiva.Eje: Ciencias de la Atmósfera y los Océanos.Facultad de Ciencias Astronómicas y Geofísica

Variabilidad de baja frecuencia en los caudales de los ríos del centro-norte de Argentina y su contribución al desarrollo de sequías hidrológicas

Con el propósito de mejorar el conocimiento de la variabilidad temporal de los caudales de los ríos del centro-norte de Argentina en términos de la variabilidad de baja frecuencia, se analizaron los registros mensuales históricos de 10 estaciones de aforo durante el período 1919-2014. A fin de comparar los registros hidrológicos en cuencas con distintas características climáticas y geográficas, se utilizó el índice de caudal estandarizado (ICE), el cual fue obtenido mediante el ajuste de los caudales mensuales a una distribución de probabilidades gamma para luego transformarlos en una variable estandarizada. Mediante una descomposición empírica se obtuvieron los principales modos de variabilidad temporal de los caudales, los cuales abarcan desde la escala estacional a las variaciones multi-decadales, y una tendencia de largo plazo no-lineal. Para el análisis de la variabilidad de baja frecuencia se realizó una composición de los modos que tuvieran periodicidades de 10 o más años. Los resultados muestran que la variabilidad climática juega un papel fundamental, modulando las variaciones de los períodos de sequía hidrológica en diversas escalas de tiempo, lo cual se identificó a través de las tendencias observadas en el último siglo. Estas variaciones de baja frecuencia imponen condiciones de clima noestacionario, lo cual debe tenerse en cuenta para lograr una gestión de riesgos efectiva.Eje: Ciencias de la Atmósfera y los Océanos.Facultad de Ciencias Astronómicas y Geofísica

Precipitation extremes over La Plata Basin –Review and new results from observations and climate simulations

Monthly and daily precipitation extremes over La Plata Basin (LPB) are analyzed in the framework of the CLARIS-LPB Project. A review of the studies developed during the project and results of additional research are presented and discussed. Specific aspects of analysis are focused on large-scale versus local processes impacts on the intensity and frequency of precipitation extremes over LPB, and on the assessment of specific wet and dry spell indices and their changed characteristics in future climate scenarios. The analysis is shown for both available observations of precipitation in the region and ad-hoc global and regional models experiments. The Pacific, Indian and Atlantic Oceans can all impact precipitation intensity and frequency over LPB. In particular, considering the Pacific sector, different types of ENSO events (i.e. canonical vs Modoki or East vs Central) have different influences. Moreover, model projections indicate an increase in the frequency of precipitation extremes over LPB during El Niño and La Ninã events in future climate. Local forcings can also be important for precipitation extremes. Here, the feedbacks between soil moisture and extreme precipitation in LPB are discussed based on hydric conditions in the region and model sensitivity experiments. Concerning droughts, it was found that they were more frequent in the western than in the eastern sector of LPB during the period of 1962–2008. On the other hand, observations and model experiments agree in that the monthly wet extremes were more frequent than the dry extremes in the northern and southern LPB sectors during the period 1979–2001, with higher frequency in the south.Published211-2304A. Clima e OceaniJCR Journalrestricte

Variability of the western Mediterranean Sea surface temperature during the last 25,000 years and its connection with the Northern Hemisphere climatic changes

Sea surface temperature (SST) profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a W-E latitudinal transect encompassing the Gulf of Cadiz (Atlantic Ocean), the Alboran Sea, and the southern Tyrrhenian Sea (western Mediterranean). The results document the sensitivity of the Mediterranean region to the short climatic changes of the North Atlantic Ocean, particularly those involving the latitudinal position of the polar front. The amplitude of the SST oscillations increases toward the Tyrrhenian Sea, indicating an amplification effect of the Atlantic signal by the climatic regime of the Mediterranean region. All studied cores show a shorter cooling phase (700 years) for the Younger Dryas (YD) than that observed in the North Atlantic region (1200 years). This time diachroneity is related to an intra-YD climatic change documented in the European continent. Minor oscillations in the southward displacement of the North Atlantic polar front may also have driven this early warming in the studied area. During the Holocene a regional diachroneity propagating west to east is observed for the SST maxima, 11.5-10.2 kyr B.P. in the Gulf of Cadiz, 10-9 kyr B.P. in the Alboran Sea, and 8.9-8.4 kyr B.P. in the Thyrrenian Sea. A general cooling trend from these SST maxima to present day is observed during this stage, which is marked by short cooling oscillations with a periodicity of 730±40 years and its harmonics

State of the climate in 2013

In 2013, the vast majority of the monitored climate variables reported here maintained trends established in recent decades. ENSO was in a neutral state during the entire year, remaining mostly on the cool side of neutral with modest impacts on regional weather patterns around the world. This follows several years dominated by the effects of either La Niña or El Niño events. According to several independent analyses, 2013 was again among the 10 warmest years on record at the global scale, both at the Earths surface and through the troposphere. Some regions in the Southern Hemisphere had record or near-record high temperatures for the year. Australia observed its hottest year on record, while Argentina and New Zealand reported their second and third hottest years, respectively. In Antarctica, Amundsen-Scott South Pole Station reported its highest annual temperature since records began in 1957. At the opposite pole, the Arctic observed its seventh warmest year since records began in the early 20th century. At 20-m depth, record high temperatures were measured at some permafrost stations on the North Slope of Alaska and in the Brooks Range. In the Northern Hemisphere extratropics, anomalous meridional atmospheric circulation occurred throughout much of the year, leading to marked regional extremes of both temperature and precipitation. Cold temperature anomalies during winter across Eurasia were followed by warm spring temperature anomalies, which were linked to a new record low Eurasian snow cover extent in May. Minimum sea ice extent in the Arctic was the sixth lowest since satellite observations began in 1979. Including 2013, all seven lowest extents on record have occurred in the past seven years. Antarctica, on the other hand, had above-average sea ice extent throughout 2013, with 116 days of new daily high extent records, including a new daily maximum sea ice area of 19.57 million km2 reached on 1 October. ENSO-neutral conditions in the eastern central Pacific Ocean and a negative Pacific decadal oscillation pattern in the North Pacific had the largest impacts on the global sea surface temperature in 2013. The North Pacific reached a historic high temperature in 2013 and on balance the globally-averaged sea surface temperature was among the 10 highest on record. Overall, the salt content in nearsurface ocean waters increased while in intermediate waters it decreased. Global mean sea level continued to rise during 2013, on pace with a trend of 3.2 mm yr-1 over the past two decades. A portion of this trend (0.5 mm yr-1) has been attributed to natural variability associated with the Pacific decadal oscillation as well as to ongoing contributions from the melting of glaciers and ice sheets and ocean warming. Global tropical cyclone frequency during 2013 was slightly above average with a total of 94 storms, although the North Atlantic Basin had its quietest hurricane season since 1994. In the Western North Pacific Basin, Super Typhoon Haiyan, the deadliest tropical cyclone of 2013, had 1-minute sustained winds estimated to be 170 kt (87.5 m s-1) on 7 November, the highest wind speed ever assigned to a tropical cyclone. High storm surge was also associated with Haiyan as it made landfall over the central Philippines, an area where sea level is currently at historic highs, increasing by 200 mm since 1970. In the atmosphere, carbon dioxide, methane, and nitrous oxide all continued to increase in 2013. As in previous years, each of these major greenhouse gases once again reached historic high concentrations. In the Arctic, carbon dioxide and methane increased at the same rate as the global increase. These increases are likely due to export from lower latitudes rather than a consequence of increases in Arctic sources, such as thawing permafrost. At Mauna Loa, Hawaii, for the first time since measurements began in 1958, the daily average mixing ratio of carbon dioxide exceeded 400 ppm on 9 May. The state of these variables, along with dozens of others, and the 2013 climate conditions of regions around the world are discussed in further detail in this 24th edition of the State of the Climate series. © 2014, American Meteorological Society. All rights reserved

Burden of intracerebral haemorrhage in Europe: forecasting incidence and mortality between 2019 and 2050

Background: Anticipating the burden of intracerebral haemorrhage is crucial for proactive management and building resilience against future health challenges. Prior forecasts are based on population demography and to a lesser extent epidemiological trends. This study aims to utilise selected modifiable risk factors and socio-demographic indicators to forecast the incidence and mortality of intracerebral haemorrhage in Europe between 2019 and 2050. Methods: Three intracerebral haemorrhage risk factors identified in the Global Burden of Diseases, Injuries, and Risk Factors study (GBD 2019)—high systolic blood pressure, high fasting plasma glucose, and high body mass index—were utilised to predict the risk-attributable fractions between 2019 and 2050. Disease burden not attributable to these risk factors was then forecasted using time series models (autoregressive integrated moving average [ARIMA]), incorporating the Socio-demographic Index (SDI) as an external predictor. The optimal parameters of ARIMA models were selected for each age-sex-country group based on the Akaike Information Criterion (AIC). Different health scenarios were constructed by extending the past 85th and 15th percentiles of annualised rates of change in risk factors and SDI across all location-years, stratified by age and sex groups. A decomposition analysis was performed to assess the relative contributions of population size, age composition, and intracerebral haemorrhage risk on the projected changes. Findings: Compared with observed figures in 2019, our analysis predicts an increase in the burden of intracerebral haemorrhage in Europe in 2050, with a marginal rise of 0.6% (95% uncertainty interval [UI], −7.4% to 9.6%) in incident cases and an 8.9% (−2.8% to 23.6%) increase in mortality, reaching 141.2 (120.6–166.5) thousand and 144.2 (122.9–172.2) thousand respectively. These projections may fluctuate depending on trajectories of the risk factors and SDI; worsened trends could result in increases of 16.7% (8.7%–25.3%) in incidence and 31.2% (17.7%–48%) in mortality, while better trajectories may lead to a 10% (16.4%–2.3%) decrease in intracerebral haemorrhage cases with stabilised mortality. Individuals aged ≥80 years are expected to contribute significantly to the burden, comprising 62.7% of the cases in 2050, up from 40% in 2019, and 72.5% of deaths, up from 50.5%. Country-wide variations were noted in the projected changes, with decreases in the standardised rates across all nations but varying crude rates. The largest relative reductions in counts for both incidence and mortality are expected in Latvia, Bulgaria, and Hungary—ranging from −38.2% to −32.4% and −37.3% to −30.2% respectively. In contrast, the greatest increases for both measures were forecasted in Ireland (45.7% and 74.4%), Luxembourg (45% and 70.7%), and Cyprus (44.5% and 74.2%). The modelled increase in the burden of intracerebral haemorrhage could largely be attributed to population ageing. Interpretation: This study provides a comprehensive forecast of intracerebral haemorrhage in Europe until 2050, presenting different trajectories. The potential increase in the number of people experiencing and dying from intracerebral haemorrhage could have profound implications for both caregiving responsibilities and associated costs. However, forecasts were divergent between different scenarios and among EU countries, signalling the pivotal role of public health initiatives in steering the trajectories. Funding: TheEuropean Union's Horizon 2020 Research and Innovation Programme under grant agreement No.754517. TheNational Institute for Health and Care Research (NIHR) under its Programme Grants forApplied Research (NIHR202339)

Assessment of climate information needs in the Argentinean Agro-business sector

The present investigation aims at identifying the needs of the Argentinean agro-business sector for climate research and information. Our approach is focused on any type of climate information from past observations to seasonal prediction and climate change projections. We tried, in particular, to evaluate the possible existence of specific research themes that would be of major interest for these agriculture end-users. We interviewed representatives of seventeen companies from three major agrobusiness sectors: (1) regional/national entities such as agricultural associations, cooperatives and commercial trade boards; (2) insurance companies in the Argentinean agro-insurance market; and (3) large national and international companies representing cereal producers, agro-chemistry and agro-seeds. While all the interviewees recognized the strong influence of climate on their activities, they all pointed out that, at the time of making decision, they considered the political and economic risks rather than the climate one. In many aspects, climate is often considered as a fatality against which it is difficult to be protected. An interesting result is the confidence of the private sectors in the climate information provided by public sources (INTA, SMN, Universities) although they contract private consultants for frequent reports and tendencies. Finally, we explain how such sectors could make a better use of climate information (seasonal prediction, climate change scenarios) that could be integrated in their business projections. In particular, the development of new financial contracts (climate derivatives) open in countries with a relatively poor insurance history new ways to protect the different agricultural sectors, from the producer to large companies

Effect of Variable Solar Irradiance on the Reactive Power Response of Photovoltaic Generators

New grid requirements for large scale photovoltaic power plants (LS-PVPPs) demanding ancillary services make necessary the enhancement of photovoltaic (PV) generator's control. One of the challenges is the reactive power control despite the variable conditions. The aim of this paper is to present the response of reactive power considering the PV generator's capability curves and variable ambient conditions when maximum power point tracker (MPPT) is used for the active power control. For this purpose, a single PV generator of 0.6 MVA is simulated in DIgSILENT PowerFactory®. The results show that the active and reactive power varies with the ambient conditions