Passivation of Grid-Following VSCs: A Comparison Between Active Damping and Multi-Sampled PWM

This article compares different strategies used to enhance the stability properties of grid-following voltage-source converters (VSCs). Because of digital delays, VSC admittance exhibits a nonpassive zone, which introduces negative damping and may destabilize the grid-connected operation. It is shown that typically used active damping (AD) strategies only bring positive impact up to a certain frequency, while deteriorating admittance properties around and above the Nyquist frequency. Multi-sampled pulsewidth modulation (MS-PWM) greatly extends the passive admittance region, using only a single-loop current controller. Experimental admittance measurements are performed on a single-phase VSC, up to twice the switching frequency. Subsequently, different grid-connected scenarios are tested to show that MS-PWM retains stable operation, where AD methods cause instability. This article also offers analytic modeling and experimental measurements of noise propagation for compared strategies. It is shown that derivative-based AD is not highly sensitive; however, MS-PWM offers additional noise suppression

Evaluation under long-day conditions of 4x-2x progenies from crosses between potato cultivars and haploid Tuberosum-solanum chacoense hybrids.

Twelve 4x families (obtained from a sub-set of crosses between seven 4x-potato cultivars and three 2x haploid Tuberosum-Solanum chacoense hybrids) were evaluated at Hancock, Wisconsin (USA). The 4x-parents were elite cultivars selected for adaptation in three continents (Europe, South America, and North America). The 2x male clones were able to produce 2n-pollen grains by a mechanism akin to first-division restitution with crossover (FDR-CO). The estimation of the degree of heterosis for total tuber yield (TTY) was obtained by comparing the field performance of the progenies with their respective 2x and 4x parents. Haulm maturity (HM) and general tuber appearance (GTA) were also evaluated. For TTY, the 4x-2x families (as a group) outyielded both the 4x and 2x parental groups by 10.6% and 42.5%, respectively. In addition, 5 out of 12 famiIies outyielded their corresponding 4x-parents. These best five families outyielded the group of 4x-parents by 40.6%. A considerable variability was observed for HM but, in general, the families were later maturing than the 4x cultivars. The identification of 4x-2x families with GTA within the range of the 4x commercial cultivars was another important observation. An overall lack of parent-offspring correlation was detected indicating that performance of the parents per se cannot provide a reliable prediction about the performance of the families. Therefore, progeny testing would be an imperative step for selection of parental clones at both ploidy levels. Our study indicated that haploid Tuberosum-S. chacoense hybrids are able to generate heterotic 4x-2x families for TTY in combination with good GTA. These results reinforce the view that selection of superior clones for the Northern Hemisphere can be feasible using germplasm with -25% genomic contribution of this wild South American species

Environmental performances in green labels for hotels – a critical review

The global attention towards climate change has led national governments and the international community to the definition of plans aiming to reduce greenhouse gas emissions in all economic sectors. Recently, attention has focused also on the tourism sector, and especially on the lodging industry, which consumes high amounts of resources and energy to satisfy guests expectations in terms of offered services and comfort conditions. In this sector, eco-certifications or green labels are spreading, perceived as useful marketing tools to communicate the hoteliers’ environmental efforts to consumers, who are becoming more and more sensitive to ecological matters. However, the wide offer of green labels and the lack of appropriate information are contributing to increase costumers’ confusion and perception of real “green”. The present paper focuses its attention on a set of currently available tools to evaluate the environmental performances of hotels, in order to enquire if and to which extent they are able to inform about the sustainability of accommodation structures. Starting from the wide number of certification schemes available on the market, 19 multi-attribute, third-party green labels were compared, aiming to explore the role that energy efficiency measures play in the certification procedure

Melão Tupã: origem e melhoramento genético.

bitstream/CNPAT-2010/7912/1/Dc-055.pd

Desenvolvimento de marcadores microssatelites (SSR) para melao (Cucumis melo).

Resumo

Mating system and fine-scale spatial genetic structure of Solanum lycocarpum St. Hil. (Solanaceae) in the Brazilian cerrado.

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