This paper reports results and an evaluation methodology from two new decision-aid tools that were demonstrated at a Transmission System Operator (REN, Portugal) during several months in the framework of the E.U. project Anemos.plus. The first tool is a probabilistic method intended to support the definition of the operating reserve requirements. The second is a fuzzy power flow tool that identifies possible congestion situations and voltage violations in the transmission network. Both tools use as input probabilistic wind power predictions.
In order to reduce the curtailment of renewable generation in periods of low load, operators can limit the import net transfer capacity (NTC) of interconnections. This paper presents a probabilistic approach to support the operator in setting the maximum import NTC value in a way that the risk of curtailment remains below a pre-specified threshold. Main inputs are the probabilistic forecasts of wind power and solar PV generation, and special care is taken regarding the tails of the global margin distribution (all generation-all loads and pumping), since the accepted thresholds are generally very low. Two techniques are used for this purpose: interpolation with exponential functions and nonparametric estimation of extreme conditional quantiles using extreme value theory. The methodology is applied to five representative days, where situations ranging from high maximum NTC values to NTC=0 are addressed. Comparison of the two techniques for modeling tails is also comprised.
The objective of this paper is to describe a process which was developed in the Portuguese TSO (REN -Rede Eléctrica Nacional, SA) whose main purpose is to identify voltage collapse situations without the need for the specific EMS module. The process is based on the Power Flow Module of PSS/E software from Siemens Power Transmission Distribution, Inc., running automatically through an application developed in Python, which performs a SV analysis. Its results are available via browser from control room PC's and are updated every 30 minutes, allowing to monitor the system security levels and to take suitable remedial actions to prevent a voltage collapse situation. The need to develop a process to identify voltage collapse situations in the Portuguese Transmission System arose with voltage problems identified in a specific substation when performing N-1 Contingency Analysis. The operator training simulator, an important tool to analyse and understand the power system behaviour, was also used to study and demonstrate the voltage collapse phenomenon.
a b s t r a c tTo reveal potential impacts to environment and human health quantitatively, co-composting and utilization of sludge and woodchips were investigated using a life-cycle-based model, EASETECH. Three scenarios were assessed through experiments using different material ratios. Emission amounts during cocomposting were determined by monitoring data and mass balance. With 100 t sludge treatment, cocomposting showed impacts to acidification (29.9 PE) and terrestrial eutrophication (57.7 PE) mainly for ammonia emission. Compost utilization presented savings on freshwater eutrophication (À1.5 PE) because of phosphorus substitution. With the application of fewer woodchips, impacts to acidification and terrestrial eutrophication decreased because more ammonium was reserved rather than released. All impacts to human toxicity were not significant (8.2 ± 0.6 PE) because the compost was used for urban landscaping rather than farming. Trace gaseous compounds showed marginal impacts to global warming and toxicity categories. The results provide a new perspective and offer evidence for appropriate sludge treatment selection.
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