Harmonic analysis and mitigation in distribution grids with high penetration of power inverters

Inverters of large heat pumps in an urban low voltage grid generate current harmonics and cause consequently significant variations of the respective voltage harmonics. The voltage level at each grid point is not only influenced by the operation of such inverters, but higher harmonic voltage amplitudes can be expected, caused by the sum of all loads in the grid. The paper provides a comprehensive harmonic analysis of a typical urban distribution grid including heat pumps and presents insights on the variations and impact on the voltage profile of the 15th harmonic currents. An active harmonic filter was installed to enhance the power quality, by compensating the harmonic currents and by improving the voltage profile at grid points close-by the heat pumps

Prospective CSEP evaluation of 1-Day, 3-month, and 5-Yr earthquake forecasts for Italy

In 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP) launched three experiments to forecast the distribution of earthquakes in Italy in the subsequent 5 yrs. CSEP solicited forecasts for seismicity tomorrow, in the next three months, and for the entire 5 yrs. In those 5 yrs, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) recorded 83 target earthquakes with local magnitude 3:95 =M <4:95, and 14 larger shocks. The results show that 1-day forecasts are consistent with the number and magnitudes of the target earthquakes, and one version of the epidemic-type aftershock sequence (ETAS) model is also consistent with the spatial distribution; ensemble forecasts, which we created for the 1-day experiment, are consistent with the number, locations, and magnitudes of the target earthquakes, and they perform as well as the best model; none of the 3-month time-independent models produce consistent forecasts; the best 5-yr models account for the fault distribution and the historical seismicity; and 5-yr models based on instrumental seismicity and b-value spatial variation show poor forecasting performance. © 2018 Seismological Society of America. All rights reserved

Uniform erosion rates and relief amplitude during glacial cycles in the Southern Alps of New Zealand, as revealed from OSL-thermochronology

International audienceGlaciers and rivers control the shape of the high relief topography of mountain ranges. However, their relative contribution in response to climatic oscillations and tectonic forcing and whether landscapes can reach equilibrium conditions during the Quaternary are still unclear. Here we introduce a new thermochronometer of exceptionally low closure temperature (ca. 30-35 °C) based on Optically Stimulated Luminescence (OSL) dating and illustrate how it may be used to measure relief evolution and exhumation rates within the last glacial cycle in the Southern Alps of New Zealand, one of the most tectonically active orogens and an area that has experienced rapid, high magnitude climate changes. We find that exhumation rates have remained steady over the last glacial cycle and match rates observed at a million year timescale. This suggests that, despite an extreme exhumation rate of the order of 800 m in 100 ka, and the fact that in the last ca. 11-18 ka most hillslope sides have changed from U to V-shape valleys and have been dissected by debris-flows, landslides and rock avalanches, the mean exhumation rates have remained nearly constant. This may imply that tectonics, not climate, has a primary control on the rates of exhumation in tectonically active and wet mountain belts. On the contrary, tectonically active mountain ranges might not attain equilibrium on similar timescales in weathering and/or transport limited landscapes as, for example, in arid regions

Review of soil salinity assessment for agriculture across multiple scales using proximal and/or remote sensors

Mapping and monitoring soil spatial variability is particularly problematic for temporally and spatially dynamic properties such as soil salinity. The tools necessary to address this classic problem only reached maturity within the past 2 decades to enable field- to regional-scale salinity assessment of the root zone, including GPS, GIS, geophysical techniques involving proximal and remote sensors, and a greater understanding of apparent soil electrical conductivity (ECa) and multi- and hyperspectral imagery. The concurrent development and application of these tools have made it possible to map soil salinity across multiple scales, which back in the 1980s was prohibitively expensive and impractical even at field scale. The combination of ECa-directed soil sampling and remote imagery has played a key role in mapping and monitoring soil salinity at large spatial extents with accuracy sufficient for applications ranging from field-scale site-specific management to statewide water allocation management to control salinity within irrigation districts. The objective of this paper is: (i) to present a review of the geophysical and remote imagery techniques used to assess soil salinity variability within the root zone from field to regional scales; (ii) to elucidate gaps in our knowledge and understanding of mapping soil salinity; and (iii) to synthesize existing knowledge to give new insight into the direction soil salinity mapping is heading to benefit policy makers, land resource managers, producers, agriculture consultants, extension specialists, and resource conservation field staff. The review covers the need and justification for mapping and monitoring salinity, basic concepts of soil salinity and its measurement, past geophysical and remote imagery research critical to salinity assessment, current approaches for mapping salinity at different scales, milestones in multi-scale salinity assessment, and future direction of field- to regional-scale salinity assessment