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Worldwide, utilities are aiming to increase the stability of modern power systems during system disturbances. Optimizing generation scheduling can improve system security in contingency and stressed conditions while lowering losses and generation costs. An efficient operating strategy for maintaining power system stability is proposed in this work. The paper focuses on incorporating a Voltage Collapse Proximity Index (VCPI) in the traditional optimal power flow problem for multiobjective optimization (MO). Different case studies are assessed to evaluate the impact on the control variables. A Preference Selection index (PSI) is utilized to determine the best-case study for optimal system operation. The effectiveness of the proposed approach is tested on standard IEEE 30-bus and IEEE 57-bus during normal, contingency, and stressed conditions using MATPOWER. During normal conditions, the MO voltage stability constrained optimal power flow (VSC-OPF) increases the system stability by 28.13 % higher than the single objective (SO) case. Furthermore, the transmission losses are lowered by 14.69% with the proposed MO approach. During line outage contingency conditions, the voltage stability enhancement and loss reduction are higher in the MO than in the SO case by 13.60% and 23.19%. However, the loss minimization and stability improvement during normal and contingency conditions come at a slightly higher generation cost of 5.05% in both systems. On the other hand, during stressed conditions, the SO performs better in voltage stability improvement (by 8.77%) and loss reduction (by 6.97%) than in the MO voltage stability constrained OPF. Additionally, PV Curve analysis for the two systems indicates that voltage stability in MO OPF problems provides a more significant margin enhancement of 9.00%, 118.95% in normal and contingency, respectively, higher than the SO case. However, the SO case increases the load margin by 12.36% more than the MO case in stressed conditions. Consequently, the PSI ranks the multiobjective optimization of the three objectives as the most optimal way for operating the systems in normal and line outage contingency conditions. However, during increased load conditions, the system performance is better if a singular objective function is considered. This is due to the lack of adequate reactive power generation during stressed conditions, and hence a singular objective focus is sufficient to assure system stability. Therefore, the proposed approach is an effective preventive control measure for possible voltage collapse in typical power systems. The resulting improvement also brings about a sufficient system stability margin, causing the system to become more secure., Fuzzy decision making, MOPSO, Preference Selection Index, PV curves, VCPI, Voltage collapse.

Flexible AC Transmission Systems (FACTS) play an important role in minimizing power losses and voltage deviations while increasing the real power transfer capacity of transmission lines. The extent to which these devices can provide benefits to the transmission network depend on their optimal location and sizing. However, finding appropriate locations and sizes of these devices in an electrical network is difficult since it is a nonlinear problem. This paper proposes a technique for the optimal placement and sizing of FACTS, namely the Thyristor-Controlled Series Compensators (TCSCs), Shunt VARs Compensators (SVCs), and Unified Power Flows Controllers (UPFCs). To find the optimal locations of these devices in a network, weak buses and lines are determined by constructing PV curves of load buses, and through the line stability index. Then, the whale optimization algorithm (WOA) is employed not only to find an ideal ratings for these devices but also the optimal coordination of SVC, TCSC, and UPFC with the reactive power sources already present in the network (tap settings of transformers and reactive power from generators). The objective here is the minimization of the operating cost of the system that consists of active power losses and FACTS devices cost. The proposed method is applied to the IEEE 14 and 30 bus systems. The presented technique is also compared with Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). The findings showed that total system operating costs and transmission line losses were considerably reduced by WOA as compared to existing metaheuristic optimization techniques.

Easily measurable functional traits can be used as proxies in the selection of drought-tolerant saplings for reforestation in Mediterranean ecosystems. Heat and drought events—increasing both in frequency and severity—have led to forest decline, and are a serious threat for the Mediterranean biome. Whereas drought tolerance of adult trees of different Mediterranean species has been widely investigated, this is not the case for saplings and young trees. We analysed correlations and trade-offs among leaf (water potential at the turgor loss point, Ψ tlp, modulus of elasticity, e, osmotic potential at full turgor, π 0, leaf capacitance, C leaf_dw, leaf venation, VLA, leaf mass per area, LMA) and stem (wood capacitance and wood density, C wood and D wood, stem-specific conductivity and water potential inducing 50% loss of hydraulic conductance) functional traits of saplings for 14 woody species of the Mediterranean flora. The results support previously reported correlations among functional traits known to confer drought tolerance to plants. In particular, Ψ tlp was positively correlated to π 0, C leaf_dw and VLA, while negatively correlated to e and LMA. A highly significant correlation was highlighted between C wood and D wood. Overall, we observed surprisingly low symplastic and apoplastic resistance. We identify some easily measurable traits (π 0 and LMA), which evidence seedlings’ ability to cope with drought, and which therefore could be used as proxies in the selection of drought-tolerant saplings for reforestation in Mediterranean areas.

This paper analyzes a tool devoted to the computation of the loading margin of power systems in the context of long-term voltage stability assessment. This tool is based on the application of homotopy techniques to solve a power system model constructed in the basis of quasi-steady-state approximations. The analyzed tool is compared to the well-known continuation power flow method in terms of accuracy and computing time. The ability of the tool to identify small-signal stability issues is also tested. This last point is verified by means of time-domain and quasi-steady-state simulations. All stability assessment methods and simulations are performed on a real-world power system.

Današnji elektroenergetski sistemi se vse bolj soocajo s posledicami prehajanja na tako imenovane nizkoogljicne proizvodnje elektricne energije (proizvodnja iz vetrnih in soncnih elektrarn in zapiranje termo in nuklearnih elektrarn), kar znatno vpliva na prerazporeditev pretokov moci, v obstojecih elektroenergetskih omrežjih. Ena bistvenih komponent fleksibilnih elektroenergetskih sistemov, ki je pogoj za integracijo vecjega deleža obnovljivih virov elektricne energije, so elektronske naprave, ki jih imenujemo tudi naprave FACTS. Naprave FACTS lahko ustrezno in dinamicno regulirajo parametre sistema (pretoke energije, napetosti), kar omogoca sigurno obratovanje sistema tudi, ko se njegove spremenljivke približajo dopustnim mejnim vrednostim. Na zacetku so naprave FACTS, zaradi dimenzij in cene, dajale predvsem teoreticne odgovore na probleme v elektroenergetskih sistemih. Danes, ko lahko stroški razpadov elektroenergetskih sistemov narastejo na milijarde evrov in so osnovni gradniki FACTS - mocnostne komponente (tiristorji) tehnološko in cenovno bolj dostopne, je tehnologija FACTS stalnica v elektroenergetskih sistemih. Naprave FACTS odlikujeta: hitrost delovanja (perioda obratovalne frekvence ali celo manj), možnost vplivanja na admitance omrežja in fazorje napetosti, kar posledicno vpliva na pretoke energije. Glede na konstrukcijo, nacin delovanja in modele v disertaciji locimo: • regulabilna serijska kompenzacija (angl. Controllable Series Compensation – CSC), • staticni sinhronski serijski kompenzator (angl. Static Synchronous Series Compensator – SSSC), • staticni VAr kompenzator (angl. Static Var Compensator – SVC), • staticni sinhronski kompenzator (angl. Static Synchronous Compensator – STATCOM) in • univerzalni precni transformator (angl. Unified Power Flow Controller – UPFC) • in druge, ki jih disertacija ne obravnava. Prenos energije po visokonapetostnih vodih je, poleg staticnih parametrov omrežja (admitance), odvisen od fazorjev napetosti na zacetkih in koncih vodov, lokacije bremenskih vozlišc in proizvodnih virov. Po visokonapetostnih vodih lahko, kljub zadostnim proizvodnim kapacitetam, prenašamo le omejeno kolicino delovne in jalove energije, kar pomeni, da za zanesljivo oskrbo z elektricno energijo ni pomembna le zadostna proizvodnja, temvec tudi njena ustrezna razporeditev. Na ustrezno razporeditev proizvodnih enot v elektroenergetskih sistemih je zelo obcutljiva (lokalna) izravnava porabe in proizvodnje jalove moci, saj jo je treba proizvesti cim bližje mestu porabe. Odstopanje porabe in proizvodnje jalove moci lahko vodi v napetostno nestabilnost, ki v najneugodnejšem slucaju povzroci razpad sistema. Posledice odmevnih razpadov elektroenergetskih sistemov, zaradi napetostne nestabilnosti, so še vedno v spominu in nam služijo kot svarilo, da je treba pri nacrtovanju in obratovanju elektroenergetskih sistemov predvideti možnost njenega nastanka. Napetostno stabilnost obravnavamo glede na razsežnost in trajanje: pocasna in hitra napetostna nestabilnost. Pri obravnavi pocasne napetostne stabilnosti zadostuje reševanje algebrajskih enacb za izracun fazorjev napetosti in uporaba metod, ki ne upošteva casovne komponente. S stališca staticne (angl. steady state) analize, hitrost delovanja naprav FACTS ne pride do izraza, saj se pojavu pocasne napetostne nestabilnosti lahko izognemo z ustreznimi (rocnimi) ukrepi, ce so ti na voljo. Hitra napetostna nestabilnosti, ki je precej manj raziskana in precej manj publicirana, temelji na dinamicnih karakteristikah modelov bremen in diferencialno algebrajskih enacbah. Nekatere raziskave nakazujejo, da je možen pristop k analizi napetostne stabilnosti tudi z direktnimi metodami, ki so dobro raziskane za analizo kotne stabilnosti. Doktorska disertacija obravnava podrocje napetostne stabilnosti, z vidika možnosti uporabe direktnih metod pri oceni napetostne stabilnosti in vpliva naprav FACTS na napetostni profil v prenosnih elektroenergetskih sistemih. Disertacija pokaže primernost direktnih metod za analizo napetostne stabilnosti in nujnost izbire ustrezne casovno odvisne (dinamicne) karakteristike bremena. Naprave FACTS lahko spreminjajo napetostni profil prenosnega omrežja, kar pokažemo z izpeljavo enacb odvisnosti napetosti v PQ vozlišcu, na osnovnih modelih sistemov z napravami FACTS. Uporaba analiticnih enacb omogoci hiter in tocen izracun PU krivulj za poljubno vrednost regulabilnih parametrov naprav FACTS. V disertaciji pokažemo, da površina podrocja, ki ga opišejo PU krivulje med mejami dopustnih napetosti, lahko služi za kriterij ocene ucinkovitosti naprave FACTS pri zagotavljanju napetostne stabilnosti. Today's electric power systems are increasingly facing the consequences of a project, i.e., low-carbon electricity production (the increase of electricity production from wind and solar power plants, the closing of coal and nuclear power plants), which has a significant impact on the redistribution of power flows in the existing electric power networks. One of the essential components of smart grids (which is a prerequisite for the integration of more renewable energy in modern electric power systems) is the electronic devices that can properly and dynamically regulate the parameters of the electric power systems (power flows, voltage). FACTS technology has been developed, but at the beginning, mainly because of the price, it only provided more or less theoretical answers to the problems in an EPS. Today, when the costs of blackouts in electric power systems can rise to billions of dollars and power-thyristor technology is more affordable, FACTS technology is often employed in electric power systems. The FACTS devices are distinguished by their operating speed (operating frequency cycle or even less), the possibility to change the network admittance and the voltage phasors, which in turn affects the power flow. Depending on the construction, operating principles and models, FACTS devices may be classified as: • controllable series compensation – CSC, • static synchronous series compensator – SSSC, • static var compensator – SVC, • static synchronous compensator – STATCOM, • unified power flow controller – UPFC • and the others which are not the subject of this thesis. The power flow through transmission lines depends not only on the static network parameters (admittances), but also on the location of the load centres and on the location of the production. Despite sufficient electricity production, the transmission lines can transmit only a limited amount of active and reactive electric power, which means that not only adequate production, but also its proper location, is important for a reliable supply. The equilibrium for the production and consumption of reactive power is greatly influenced by the location of the production units in the electric power system, which should be as close as possible to the place of consumption. A lack of reactive power can lead to voltage instability, which, in the worst case, can cause a system blackout. The consequences of significant blackouts due to voltage collapse are still in the memory and they can occur again if they are not predicted during the planning and operation of a power system. Voltage stability is considered in terms of the extension of the disturbance (small, large disturbance) and the duration: long-term and short-term voltage instability. Long-term voltage instability includes the operations of on load tap changers, thermostatically controlled loads, generator excitation limiters, and the duration is from a few minutes to a few hours. When dealing with such a slow phenomenon the solving of algebraic equations for a calculation of the power flow is sufficient, as is the use of methods that do not take into account the time component. In terms of the steady-state analysis the speed of FACTS devices is not relevant, as the occurrence of a slow voltage instability can be avoided by appropriate (“hand”) measures, if they are available. Short-term voltage instability is based on time dependant (dynamic) load models and differential algebraic equations. Some researches show the possibility of implementation of the direct methods into short-term voltage analysis, which are well-known approach in the (angle) transient-stability studies. The doctoral thesis treats the topic of voltage stability in terms of the possibility to apply the direct methods for the voltage stability estimation and the impact of FACTS-devices on the voltage profile in an electric transmission power system. Direct methods for the analysis of the transient-stability of power systems with FACTS devices are well-studied, so we focused on their suitability for analysis of voltage stability by selecting the appropriate time-dependant (dynamic) load characteristics which is explained in the present thesis. FACTS devices can vary the voltage profile of the transmission network, which we proved with the analytical derivation of equations based on power system model with FACTS devices. Application of analytical equations allows fast and accurate calculation of PU curves for any value of controllable parameters of FACTS-devices. In the thesis is shown that the surface area in PU diagram covered between the boundaries of the permissible voltage can be used for the evaluation criteria of the effectiveness of FACTS-device for achieving a stable voltage profile.

Diplomsko delo predstavi vpliv univerzalnega prečnega transformatorja na P-U krivulje kot merilo za ugotavljanje napetostne stabilnosti. Opisani so pojavi napetostne nestabilnosti v elektroenergetskem sistemu, definicija napetostne nestabilnosti, vzroki za njen nastanek in naprave, ki lahko pojav napetostne nestabilnosti omilijo. Podrobneje je predstavljen dvozbiralčni model voda, v katerega je vključen univerzalni prečni transformator. Podana so matematična izhodišča za uravnavanje napetostne stabilnosti z univerzalnim prečnim transformatorjem, ki v zadnjem poglavju rezultirajo v P-U krivulje pri različnih parametrih univerzalnega prečnega transformatorja. This thesis is dedicated to the impact of the Unified Power Flow Controller on PV curves as a criterion for determining the voltage stability. In this work we describe the phenomena of voltage instability in electric power system, the definition of instability phenomena, its formation and also the devices for voltage instability reduction. We specifically describe double busbar system including Unified Power Flow Controller (UPFC) for regulation power flow. There are also presented some of the mathematical bases of UPFC device for adjusting voltage instability problems. In the last chapter this bases result in PV curves with various parameters of the Unified Power Flow Controller.

En los Sistemas de Potencia ocurren eventos de naturaleza dinámica y transitoria los cuales son monitoreados por los Centros de Control, con el propósito de evitar escenarios de colapsos que pongan en riesgo la estabilidad de la red. Entre las técnicas de monitoreo de áreas extensas está la medición sincronizada de fasores, la cual es insumo para aplicaciones como Curvas PV y márgenes de estabilidad de tensión, que facilitan la identificación del sistema basado en la región de estabilidad y el punto de colapso de la red. El siguiente documento es el desarrollo de una herramienta computacional que muestra las Curvas PV y el Índice de Estabilidad de Tensión, usando medición sincronizada de fasores. La herramienta desarrollada fue validada con información de los fasores de tensión y corrientes en régimen dinámico de los Extremos de las Subestaciones Morochas II y Buenavista 230 kV obtenidos con simulaciones. Adicionalmente, en orden de facilitar los patrones para esta herramienta se realizaron simulaciones para observar las regiones seguras e inseguras en la operación de la red del Sistema Occidente desde el punto de vista de estabilidad por tensión. In Power Systems occur events dynamic and transient which are monitored to prevent possible collapse scenarios that could lead to risk the stability of the network. Among the techniques to monitor large areas is Synchronized Phasor Measurement accompanied by techniques such as PV curves and voltage stability margins, which facilitate the identification system based on the stability regions and collapse point of the network. This paper presents a computational tool that displays PV curves and voltage-stability indexes (EIT), using synchronized phasor measurement. The tool developed was validated with dynamic information system of transmission line, Morochas II - Buenavista 230 kV, which can be used for subsequent applications of control centers using synchronized phasor measurement. Additionally, in order to serve as a pattern for this tool was obtained from simulations safe and unsafe regions in the operation to the area under study.

In this paper the power system voltage stability problem is analyzed with active power-voltage (PV) curves, as a voltage compensator is introduced. The PV curves' shape has been a subject of great concern, especially when voltage compensators are incorporated. Nevertheless, when such devices are taken into account, ordinarily the power electronic devices' commutation it is not considered in detail. This paper proposes a shunt connected voltage compensator model that gives careful consideration to commutation dynamics. Through load variations, simulations are carried out for building the PV curves. Additionally, the field over-current protection in generators is taken into account in order to evaluate its impact on the aforementioned curves. A single-phase equivalent shunt compensator, and the proposed model, is simulated in a small power system. Results are exhibited, which show particularities that arise due to the proposed model. En este trabajo se analiza el problema de estabilidad de voltaje mediante las curvas PV, cuando se introduce un compensador de voltaje. La forma de las curvas PV ha sido de mucho interés, especialmente cuando se incorporan compensadores de voltaje. Cuando estos elementos se toman en cuenta, ordinariamente no se considera el detalle de los dispositivos de conmutación. Este trabajo propone el modelo de un dispositivo conectado en derivación que incluye su dinámica de conmutación.

Este artigo apresenta resultados de um estudo da atual condição de operação do sistema interligado brasileiro com relação à estabilidade de tensão. As análises são realizadas a partir de dados reais do planejamento e da operação. O sistema é dividido em 4 regiões: Norte, Nordeste, Sul e Sudeste/Centro-Oeste. A margem de estabilidade é obtida para cada uma destas regiões. Os resultados mostram que o sistema interligado brasileiro apresenta margem de estabilidade muito abaixo da sugerida pelos critérios existentes, a qual é limitada pela região Sudeste/Centro-Oeste. Uma análise detalhada para esta área crítica do sistema é realizada. Além de uma avaliação do comportamento da margem de estabilidade de tensão durante um dia típico de semana, esta trabalho apresenta uma análise de contingências. Utilizando a metodologia de análise modal verifica-se a abrangência das contingências, mensurando o impacto de cada contingência como local, de área ou sistêmico. This paper presents results of a study of the Brazilian system operation in respect to voltage stability criteria. The analyses are applied using real-life data from the operation and planning. The system is divided in 4 regions: North, Northeast, South and Southeast/West Center. System stability margin is evaluated for each one of these areas. The results show that Brazilian system has stability margin much lower than the existing voltage stability criteria, limited by the Southeast/West Center region. A detailed analysis of this critical area is performed. This paper also presents the stability margin behavior during a typical weekday curve and a contingency analysis. The contingency severity is verified by using the modal analysis technique assessing each contingency impact classifying as local, area or systemic.

The current ongoing increase in the atmospheric CO2 concentration is an unquestionable fact. Thus, plants are bound to live in a more enriched CO2 world in a not far-off future. In this new framework, regeneration of forest tree species may be modified as a consequence of the change in the current patterns of seedling response to other environmental resources, such as water or light. We studied the impact of an elevated CO2 concentration on the interaction of drought and light upon the water relations of cork oak (Quercus suber L.) seedlings. In a complete factorial design of contrasting light (HL vs LL), water (WW vs S) and CO2 levels (800 ppm vs 370 ppm), we analysed the influence of each factor and its interaction in the modification of different leaf water parameters in potted seedlings after a 6 months experimental period. These parameters were derived from the construction, with leaf materials, of the P-V curves: osmotic potential at full turgor (Ψπ100), osmotic potential at zero turgor (Ψπ0), modulus of elasticity at full turgor (εmax), and the ratio dry/turgor weight (DW/TW). Doubling of the CO2 levels over the current concentration (380 ppm) did not change any of the studied leaf water parameters, while light and water availabilities had a significant influence. This result does not exclude changes in other basic physiological parameters that could modify the pattern of cork oak regeneration responding to a CO2 enriched atmosphere in the future, and under climatic conditions different to the current ones., El continuo aumento actual en la concentración de CO2 en la atmósfera es un hecho incuestionable. Así, las plantas se verán abocadas a vivir en un mundo más enriquecido en CO2 que el actual en un futuro no muy lejano. En este nuevo marco, la regeneración de las especies arbóreas puede modificarse como consecuencia del cambio en los patrones actuales de respuesta a otros recursos del medio como el agua o la luz. En relación con esto, se realizó un estudio para investigar el impacto de una concentración de CO2 elevada sobre la interacción de la sequía y la luz en las relaciones hídricas de hojas de brinzales de alcornoque (Quercus suber L.). En un diseño factorial completo, y considerando niveles altos y bajos de: luz (HL-alto, respecto a LL-bajo), agua (WW-bien regadas, respecto a S-estresadas) y CO2 (800 ppm respecto a 370 ppm), se analizó la influencia de cada factor individual, y su interacción, en la modificación de distintos parámetros hídricos en hoja tras un periodo experimental de 6 meses. Los diferentes parámetros se estimaron a partir de la construcción de curvas P-V en hojas: potencial osmótico a plena turgencia (Ψπ100), potencial osmótico en el punto de marchitez (Ψπ0), módulo de elasticidad a máxima tugencia (εmax), y la relación entre el peso seco y el peso turgente (DW/TW). Una duplicación de los niveles de CO2 por encima de la concentración actual (380 ppm) no cambió ninguno de los parámetros hídricos estudiados, mientras que las disponibilidades de luz y de agua tuvieron una influencia significativa. Esto no excluye posibles modificaciones de otros procesos fisiológicos básicos que puedan alterar los actuales patrones de regeneración en el alcornoque en respuesta a una atmósfera más enriquecida en CO2 en el futuro, y en marcos climáticos diferentes al actual.

The current ongoing increase in the atmospheric CO2 concentration is an unquestionable fact. Thus, plants are bound to live in a more enriched CO2 world in a not far-off future. In this new framework, regeneration of forest tree species may be modified as a consequence of the change in the current patterns of seedling response to other environmental resources, such as water or light. We studied the impact of an elevated CO2 concentration on the interaction of drought and light upon the water relations of cork oak (Quercus suber L.) seedlings. In a complete factorial design of contrasting light (HL vs LL), water (WW vs S) and CO2 levels (800 ppm vs 370 ppm), we analysed the influence of each factor and its interaction in the modification of different leaf water parameters in potted seedlings after a 6 months experimental period. These parameters were derived from the construction, with leaf materials, of the P-V curves: osmotic potential at full turgor (Ψπ100), osmotic potential at zero turgor (Ψπ0), modulus of elasticity at full turgor (εmax), and the ratio dry/turgor weight (DW/TW). Doubling of the CO2 levels over the current concentration (380 ppm) did not change any of the studied leaf water parameters, while light and water availabilities had a significant influence. This result does not exclude changes in other basic physiological parameters that could modify the pattern of cork oak regeneration responding to a CO2 enriched atmosphere in the future, and under climatic conditions different to the current ones. El continuo aumento actual en la concentración de CO2 en la atmósfera es un hecho incuestionable. Así, las plantas se verán abocadas a vivir en un mundo más enriquecido en CO2 que el actual en un futuro no muy lejano. En este nuevo marco, la regeneración de las especies arbóreas puede modificarse como consecuencia del cambio en los patrones actuales de respuesta a otros recursos del medio como el agua o la luz. En relación con esto, se realizó un estudio para investigar el impacto de una concentración de CO2 elevada sobre la interacción de la sequía y la luz en las relaciones hídricas de hojas de brinzales de alcornoque (Quercus suber L.). En un diseño factorial completo, y considerando niveles altos y bajos de: luz (HL-alto, respecto a LL-bajo), agua (WW-bien regadas, respecto a S-estresadas) y CO2 (800 ppm respecto a 370 ppm), se analizó la influencia de cada factor individual, y su interacción, en la modificación de distintos parámetros hídricos en hoja tras un periodo experimental de 6 meses. Los diferentes parámetros se estimaron a partir de la construcción de curvas P-V en hojas: potencial osmótico a plena turgencia (Ψπ100), potencial osmótico en el punto de marchitez (Ψπ0), módulo de elasticidad a máxima tugencia (εmax), y la relación entre el peso seco y el peso turgente (DW/TW). Una duplicación de los niveles de CO2 por encima de la concentración actual (380 ppm) no cambió ninguno de los parámetros hídricos estudiados, mientras que las disponibilidades de luz y de agua tuvieron una influencia significativa. Esto no excluye posibles modificaciones de otros procesos fisiológicos básicos que puedan alterar los actuales patrones de regeneración en el alcornoque en respuesta a una atmósfera más enriquecida en CO2 en el futuro, y en marcos climáticos diferentes al actual.