• Energy Research

Abstract The attention on the smart grids and smart grid technologies has grown significantly over the last few years. The analysis made in this study is grounded on the smart grid projects database of the Joint Research Centre (European Commission). The European smart grid projects are analyzed among others in terms of: number, countries, duration and collaboration. Additionally, an analysis is done regarding the annual number of starting and concluded/planned to be concluded projects, the total number of participants per year, the distribution of smart grid applications per stage of development, year and EU country and an overview of the investments in the European smart grid projects is provided. Afterwards a forecast is done regarding the number of projects. As a result of graphical and predictive analyses, many essential inferences are achieved related to the current status and the anticipated short-term trends of smart grid projects.

Abstract The attention on the smart grids and smart grid technologies has grown significantly over the last few years. The analysis made in this study is grounded on the smart grid projects database of the Joint Research Centre (European Commission). The European smart grid projects are analyzed among others in terms of: number, countries, duration and collaboration. Additionally, an analysis is done regarding the annual number of starting and concluded/planned to be concluded projects, the total number of participants per year, the distribution of smart grid applications per stage of development, year and EU country and an overview of the investments in the European smart grid projects is provided. Afterwards a forecast is done regarding the number of projects. As a result of graphical and predictive analyses, many essential inferences are achieved related to the current status and the anticipated short-term trends of smart grid projects.

Abstract Fast charging is perceived by users as a preferred method for extending the average daily mobility of electric vehicles (EV). The rated power of fast chargers, their expected operation during peak hours, and clustering in designated stations, raise significant concerns. On one hand it raises concerns about standard requirements for power quality, especially harmonic distortion due to the use of power electronics connecting to high loads, typically ranging from 18 to 24 kW h. On the other hand, infrastructure dimensioning and design limitations for those investing in such facilities need to be considered. Four sets of measurements were performed during the complete charging cycle of an EV, and individual harmonic's amplitude and phase angles behaviour were analysed. In addition, the voltage and current total harmonic distortion (THD) and Total Demand Distortion (TDD) were calculated and the results compared with the IEEE519, IEC 61000/EN50160 standards. Additionally, two vehicles being fast charged while connected to the same feeder were simulated and an analysis was carried out on how the harmonic phase angles would relate. The study concluded that the use of TDD was a better indicator than THD, since the former uses the maximum current ( I L ) and the latter uses the fundamental current, sometimes misleading conclusions, hence it is suggested it should be included in IEC/EN standard updates. Voltage THD and TDD for the charger analysed, were within the standard's limits of 1.2% and 12% respectively, however individual harmonics (11th and 13th) failed to comply with the 5.5% limit in IEEE 519 (5% and 3% respectively in IEC61000). Phase angles tended to have preferential range differences from the fundamental wave. It was found that the average difference between the same harmonic order phase angles was lower than 90°, meaning that when more than one vehicle is connected to the same feeder the amplitudes will add. Since the limits are dependable on the upstream short circuit current ( I SC ), if the number of vehicles increases (i.e. I L ), the standard limits will decrease and eventually be exceeded. The harmonic limitation is hence the primary binding condition, certainly before the power limitation. The initial limit to the number of chargers is not the power capacity of the upstream power circuit but the harmonic limits for electricity pollution.

Abstract Fast charging is perceived by users as a preferred method for extending the average daily mobility of electric vehicles (EV). The rated power of fast chargers, their expected operation during peak hours, and clustering in designated stations, raise significant concerns. On one hand it raises concerns about standard requirements for power quality, especially harmonic distortion due to the use of power electronics connecting to high loads, typically ranging from 18 to 24 kW h. On the other hand, infrastructure dimensioning and design limitations for those investing in such facilities need to be considered. Four sets of measurements were performed during the complete charging cycle of an EV, and individual harmonic's amplitude and phase angles behaviour were analysed. In addition, the voltage and current total harmonic distortion (THD) and Total Demand Distortion (TDD) were calculated and the results compared with the IEEE519, IEC 61000/EN50160 standards. Additionally, two vehicles being fast charged while connected to the same feeder were simulated and an analysis was carried out on how the harmonic phase angles would relate. The study concluded that the use of TDD was a better indicator than THD, since the former uses the maximum current ( I L ) and the latter uses the fundamental current, sometimes misleading conclusions, hence it is suggested it should be included in IEC/EN standard updates. Voltage THD and TDD for the charger analysed, were within the standard's limits of 1.2% and 12% respectively, however individual harmonics (11th and 13th) failed to comply with the 5.5% limit in IEEE 519 (5% and 3% respectively in IEC61000). Phase angles tended to have preferential range differences from the fundamental wave. It was found that the average difference between the same harmonic order phase angles was lower than 90°, meaning that when more than one vehicle is connected to the same feeder the amplitudes will add. Since the limits are dependable on the upstream short circuit current ( I SC ), if the number of vehicles increases (i.e. I L ), the standard limits will decrease and eventually be exceeded. The harmonic limitation is hence the primary binding condition, certainly before the power limitation. The initial limit to the number of chargers is not the power capacity of the upstream power circuit but the harmonic limits for electricity pollution.

Abstract Wind energy is an important contributor of modern power systems as a renewable energy source. However, wind energy poses new challenges because of its unique characteristics, such as limited predictability, short-term and long-term variability and close-to-zero marginal cost. This paper puts forward the critical aspects of wind energy systems in respect to the transformation of the power system into a “smart grid”. Issues discussed include the electro-mechanical matters like the selection of wind turbine technology, the structure of wind system, the robustness of mechanical parts (gear box and blades) and fault diagnosis. In addition, the system operational challenges such as complexity, instability, unbalance loading, grid interactive problems and impact of wind energy on power system are discussed in this paper. Moreover, the economical subjects such as investment costs and energy management, communication requirements, and security are involved as important titles. Finally, environmental aspects of wind energy are also highlighted to show that the wind energy is an environmentally friendly energy source since it is sustainable, clean and safe.

Abstract Wind energy is an important contributor of modern power systems as a renewable energy source. However, wind energy poses new challenges because of its unique characteristics, such as limited predictability, short-term and long-term variability and close-to-zero marginal cost. This paper puts forward the critical aspects of wind energy systems in respect to the transformation of the power system into a “smart grid”. Issues discussed include the electro-mechanical matters like the selection of wind turbine technology, the structure of wind system, the robustness of mechanical parts (gear box and blades) and fault diagnosis. In addition, the system operational challenges such as complexity, instability, unbalance loading, grid interactive problems and impact of wind energy on power system are discussed in this paper. Moreover, the economical subjects such as investment costs and energy management, communication requirements, and security are involved as important titles. Finally, environmental aspects of wind energy are also highlighted to show that the wind energy is an environmentally friendly energy source since it is sustainable, clean and safe.

Artículos en revistas The sustained cost reduction of solar photovoltaics (PV) modules together with the introduction of self-consumption policies is transforming passive electricity consumers into active ones (prosumers). However, self-consumption policies may present very different designs and results mainly depending on the schemes that are put in place. Policy design implementations can have important consequences on the PV sizing and on the deployment rate, which impact the overall power sector from both a technical and an economic perspective. Previous analyses have focused on the existing relation between tariff design and self-consumption in terms of investment decisions made by prosumers or on how to ensure system fixed-cost recovery by preventing undesirable cross-subsidies among consumers. However, little attention has been paid so far to the effects of self-consumption policy design on the distribution networks, where most prosumers are connected. On this purpose, this paper performs a power flow-based quantitative assessment of such impact, using European representative distribution networks, and by discussing potential drawbacks which can be faced under different PV penetration scenarios and when different policies are put in place. Results show that the size of the installations (driven by the self-consumption policy incentives) has a great impact on the voltage and thermal limit violations, which is sometimes even higher than the impact of the PV penetration level. An in-depth discussion on the regulatory implications is also reported. The need to improve the tariff designs, so that they also reflect the extra costs in the distribution networks is discussed. Then, alternatives to avoid or defer network investments are proposed including the use of curtailment, the revision of current voltage limits, possibly too stringent in some countries, and the application of smart grid technologies. Finally, the key role of aggregator to provide flexibility services is identified. info:eu-repo/semantics/publishedVersion

Artículos en revistas The sustained cost reduction of solar photovoltaics (PV) modules together with the introduction of self-consumption policies is transforming passive electricity consumers into active ones (prosumers). However, self-consumption policies may present very different designs and results mainly depending on the schemes that are put in place. Policy design implementations can have important consequences on the PV sizing and on the deployment rate, which impact the overall power sector from both a technical and an economic perspective. Previous analyses have focused on the existing relation between tariff design and self-consumption in terms of investment decisions made by prosumers or on how to ensure system fixed-cost recovery by preventing undesirable cross-subsidies among consumers. However, little attention has been paid so far to the effects of self-consumption policy design on the distribution networks, where most prosumers are connected. On this purpose, this paper performs a power flow-based quantitative assessment of such impact, using European representative distribution networks, and by discussing potential drawbacks which can be faced under different PV penetration scenarios and when different policies are put in place. Results show that the size of the installations (driven by the self-consumption policy incentives) has a great impact on the voltage and thermal limit violations, which is sometimes even higher than the impact of the PV penetration level. An in-depth discussion on the regulatory implications is also reported. The need to improve the tariff designs, so that they also reflect the extra costs in the distribution networks is discussed. Then, alternatives to avoid or defer network investments are proposed including the use of curtailment, the revision of current voltage limits, possibly too stringent in some countries, and the application of smart grid technologies. Finally, the key role of aggregator to provide flexibility services is identified. info:eu-repo/semantics/publishedVersion