Dynamic Modeling and Simulation of a STATCOM/SMES Compensator in Power Systems

The advent of Flexible AC Transmission Systems (FACTS) is giving rise to a new family of electronic equipment emerging to controlling and optimizing the performance of power system, e.g. STATCOM. Static synchronous compensator (STATCOM) is one of the most widely used FACTS devices. This paper presents the integration of STATCOM coupled with superconducting magnetic energy storage (SMES) device in order to provide power oscillation damping in power systems. The additional of energy storage allows the combined compensator to exchange both reactive and active power with the ac network and also capability of the STATCOM is enhanced. This paper describes the structure and characteristics of STATCOM/SMES. In addition, using a proper control scheme, STATCOM/SMES is tested on an IEEE 3-bus system and more effective performance of the presented STATCOM/SMES compensator is evaluated with alone STATCOM through the dynamic simulation by using PSCAD/EMTDC software

Regaining the FORS: optical ground-based transmission spectroscopy of the exoplanet WASP-19b with VLT+FORS2

In the past few years, the study of exoplanets has evolved from being pure discovery, then being more exploratory in nature and finally becoming very quantitative. In particular, transmission spectroscopy now allows the study of exoplanetary atmospheres. Such studies rely heavily on space-based or large ground-based facilities, because one needs to perform time-resolved, high signal-to-noise spectroscopy. The very recent exchange of the prisms of the FORS2 atmospheric diffraction corrector on ESO's Very Large Telescope should allow us to reach higher data quality than was ever possible before. With FORS2, we have obtained the first optical ground-based transmission spectrum of WASP-19b, with 20 nm resolution in the 550--830 nm range. For this planet, the data set represents the highest resolution transmission spectrum obtained to date. We detect large deviations from planetary atmospheric models in the transmission spectrum redwards of 790 nm, indicating either additional sources of opacity not included in the current atmospheric models for WASP-19b or additional, unexplored sources of systematics. Nonetheless, this work shows the new potential of FORS2 for studying the atmospheres of exoplanets in greater detail than has been possible so far.Comment: 7 pages, 9 figures, 3 tables. Accepted for publication in A&

Dynamic Modeling and Simulation of a STATCOM/SMES Compensator in Power Systems

The advent of Flexible AC Transmission Systems (FACTS) is giving rise to a new family of electronic equipment emerging to controlling and optimizing the performance of power system, e.g. STATCOM. Static synchronous compensator (STATCOM) is one of the most widely used FACTS devices. This paper presents the integration of STATCOM coupled with superconducting magnetic energy storage (SMES) device in order to provide power oscillation damping in power systems. The additional of energy storage allows the combined compensator to exchange both reactive and active power with the ac network and also capability of the STATCOM is enhanced. This paper describes the structure and characteristics of STATCOM/SMES. In addition, using a proper control scheme, STATCOM/SMES is tested on an IEEE 3-bus system and more effective performance of the presented STATCOM/SMES compensator is evaluated with alone STATCOM through the dynamic simulation by using PSCAD/EMTDC software

Optimal Placement of Capacitors for Get the Best Total Generation Cost by Genetic Algorithm

Economic Dispatch(ED) is one of the most challenging problems of power system since it is difficult to determine the optimum generation scheduling to meet the particular load demand with the minimum fuel costs while all constraints are satisfied. The objective of the Economic Dispatch Problems (EDPs) of electric power generation is to schedule the committed generating units outputs so as to meet the required load demand at minimum operating cost while satisfying all units and system equality and inequality constraints. In this paper, an efficient and practical steady-state genetic algorithm (SSGAs) has been proposed for solving the economic dispatch problem. The objective is to minimize the total generation fuel cost and keep the power flows within the security limits. To achieve that, the present work is developed to determine the optimal location and size of capacitors in transmission power system where, the Participation Factor Algorithm and the Steady State Genetic Algorithm are proposed to select the best locations for the capacitors and determine the optimal size for them

Optimal Placement of Capacitors for Get the Best Total Generation Cost by Genetic Algorithm

Economic Dispatch(ED) is one of the most challenging problems of power system since it is difficult to determine the optimum generation scheduling to meet the particular load demand with the minimum fuel costs while all constraints are satisfied. The objective of the Economic Dispatch Problems (EDPs) of electric power generation is to schedule the committed generating units outputs so as to meet the required load demand at minimum operating cost while satisfying all units and system equality and inequality constraints. In this paper, an efficient and practical steady-state genetic algorithm (SSGAs) has been proposed for solving the economic dispatch problem. The objective is to minimize the total generation fuel cost and keep the power flows within the security limits. To achieve that, the present work is developed to determine the optimal location and size of capacitors in transmission power system where, the Participation Factor Algorithm and the Steady State Genetic Algorithm are proposed to select the best locations for the capacitors and determine the optimal size for them

Optimal Placement of Capacitors for Get the Best Total Generation Cost by Genetic Algorithm

Economic Dispatch(ED) is one of the most challenging problems of power system since it is difficult to determine the optimum generation scheduling to meet the particular load demand with the minimum fuel costs while all constraints are satisfied. The objective of the Economic Dispatch Problems (EDPs) of electric power generation is to schedule the committed generating units outputs so as to meet the required load demand at minimum operating cost while satisfying all units and system equality and inequality constraints. In this paper, an efficient and practical steady-state genetic algorithm (SSGAs) has been proposed for solving the economic dispatch problem. The objective is to minimize the total generation fuel cost and keep the power flows within the security limits. To achieve that, the present work is developed to determine the optimal location and size of capacitors in transmission power system where, the Participation Factor Algorithm and the Steady State Genetic Algorithm are proposed to select the best locations for the capacitors and determine the optimal size for them

Making FORS2 fit for exoplanet observations (again)

For about three years, it was known that precision spectrophotometry with FORS2 suffered from systematic errors that made quantitative observations of planetary transits impossible. We identified the Longitudinal Atmospheric Dispersion Compensator (LADC) as the most likely culprit, and therefore engaged in a project to exchange the LADC prisms with the uncoated ones from FORS1. This led to a significant improvement in the depth of FORS2 zero points, a reduction in the systematic noise, and should make FORS2 again competitive for transmission spectroscopy of exoplanets.Comment: To appear in the March issue of the ESO Messenge

A precise blue-optical transmission spectrum from the ground: evidence for haze in the atmosphere of WASP-74b

We report transmission spectroscopy of the bloated hot Jupiter WASP-74b in the wavelength range from 4000 to 6200 Å. We observe two transit events with the Very Large Telescope (VLT) Focal Reducer and Spectrograph and present a new method to measure the exoplanet transit depth as a function of wavelength. The new method removes the need for a reference star in correcting the spectroscopic light curves for the impact of atmospheric extinction. It also provides improved precision, compared to other techniques, reaching an average transit depth uncertainty of 211 ppm for a solar-type star of V = 9.8 mag and over wavelength bins of 80 Å. The VLT transmission spectrum is analysed both individually and in combination with published data from Hubble Space Telescope and Spitzer. The spectrum is found to exhibit a mostly featureless slope and equilibrium chemistry retrievals with PLATON favour hazes in the upper atmosphere of the exoplanet. Free chemistry retrievals with AURA further support the presence of hazes. While additional constraints are possible depending on the choice of atmospheric model, they are not robust and may be influenced by residual systematics in the data sets. Our results demonstrate the utility of new techniques in the analysis of optical, ground-based spectroscopic data and can be highly complementary to follow-up observations in the infrared with JWST

CARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b

Casasayas-Barris, N., et al.Ultra-hot Jupiters are highly irradiated gas giants with equilibrium temperatures typically higher than 2000 K. Atmospheric studies of these planets have shown that their transmission spectra are rich in metal lines, with some of these metals being ionised due to the extreme temperatures. Here, we use two transit observations of WASP-76b obtained with the CARMENES spectrograph to study the atmosphere of this planet using high-resolution transmission spectroscopy. Taking advantage of the two channels and the coverage of the red and near-infrared wavelength ranges by CARMENES, we focus our analysis on the study of the Ca II infrared triplet (IRT) at 8500 Å and the He I triplet at 10 830 Å. We present the discovery of the Ca II IRT at 7¿ in the atmosphere of WASP-76b using the cross-correlation technique, which is consistent with previous detections of the Ca II H&K lines in the same planet, and with the atmospheric studies of other ultra-hot Jupiters reported to date. The low mass density of the planet, and our calculations of the XUV (X-ray and EUV) irradiation received by the exoplanet, show that this planet is a potential candidate to have a He I evaporating envelope and, therefore, we performed further investigations focussed on this aspect. The transmission spectrum around the He I triplet shows a broad and red-shifted absorption signal in both transit observations. However, due to the strong telluric contamination around the He I lines and the relatively low signal-to-noise ratio of the observations, we are not able to unambiguously conclude if the absorption is due to the presence of helium in the atmosphere of WASP-76b, and we consider the result to be only an upper limit. Finally, we revisit the transmission spectrum around other lines such as Na I, Li I, H¿, and K I. The upper limits reported here for these lines are consistent with previous studies.We acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program under grant agreement no. 694513, the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C5[1:4]/AEI/10.13039/501100011033, PID2019- 110689RB-I00/AEI/10.13039/501100011033, ESP2017-87143-R, and ESP2016- 80435-C2-2-R, and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to the Instituto de Astrofísica de Canarias (CEX2019-000920- S), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. T.H. acknowledges support by the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28. G.M. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 895525

Detection of titanium oxide in the atmosphere of a hot Jupiter.

As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet's atmosphere, causing the planet to seem bigger; plotting the planet's observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet's atmosphere. Chemical species composed of light elements-such as hydrogen, oxygen, carbon, sodium and potassium-have in this way been detected in the atmospheres of several hot giant exoplanets, but molecules composed of heavier elements have thus far proved elusive. Nonetheless, it has been predicted that metal oxides such as titanium oxide (TiO) and vanadium oxide occur in the observable regions of the very hottest exoplanetary atmospheres, causing thermal inversions on the dayside. Here we report the detection of TiO in the atmosphere of the hot-Jupiter planet WASP-19b. Our combined spectrum, with its wide spectral coverage, reveals the presence of TiO (to a confidence level of 7.7σ), a strongly scattering haze (7.4σ) and sodium (3.4σ), and confirms the presence of water (7.9σ) in the atmosphere