Multivariate statistical modelling of future marine storms

Extreme events, such as wave-storms, need to be characterized for coastal infrastructure design purposes. Such description should contain information on both the univariate behaviour and the joint-dependence of storm-variables. These two aspects have been here addressed through generalized Pareto distributions and hierarchical Archimedean copulas. A non-stationary model has been used to highlight the relationship between these extreme events and non-stationary climate. It has been applied to a Representative Concentration Pathway 8.5 Climate-Change scenario, for a fetch-limited environment (Catalan Coast). In the non-stationary model, all considered variables decrease in time, except for storm-duration at the northern part of the Catalan Coast. The joint distribution of storm variables presents cyclical fluctuations, with a stronger influence of climate dynamics than of climate itself.Peer ReviewedPostprint (author's final draft

Effects of the Selected Point of Voltage Reference on the Apparent Power Measurement in Three-Phase Star Systems

[EN] The phenomenon responsible for the different apparent powers measured in a subsystem of a three-phase star-configured system, based on the voltage reference point, was identified in this paper using specific components of the instantaneous powers, as a result of applying the conservation of energy principle to the entire system. The effects of the phenomenon were determined using a proposed apparent power component referred to as the neutral-displacement power, whose square is the quadratic difference between the apparent powers of a subsystem, measured using two voltage reference points. The neutral-displacement power is a component of the apparent power, which is determined using the values of the zero-sequence voltages and the line currents in that subsystem. Expressions of the proposed power were derived using the Buchholz apparent power formulations. The validation of the derived expressions was checked in the laboratory and in a real-world electrical network, using a well-known commercial analyzer and a prototype developed by the authors.This research was funded by Universidad Politecnica de Valencia, under grant Primeros Proyectos de Investigacion (PAID-06-18), Vicerrectorado de Investigacion, Innovacion y Valencia.León-Martínez, V.; Montañana-Romeu, J.; Peñalvo-López, E.; Álvarez, C. (2020). Effects of the Selected Point of Voltage Reference on the Apparent Power Measurement in Three-Phase Star Systems. Applied Sciences. 10(3):1-22. https://doi.org/10.3390/app10031036S122103Emanuel, A. E., & Orr, J. A. (s. f.). The effect of neutral path impedance on voltage and current distortion. Part I. symmetrical and balanced three-phase systems. 2004 11th International Conference on Harmonics and Quality of Power (IEEE Cat. No.04EX951). doi:10.1109/ichqp.2004.1409351Emanuel, A. E., & Orr, J. A. (s. f.). The effect of neutral path impedance on voltage and current distortion. Part II. Imbalanced three-phase systems. 2004 11th International Conference on Harmonics and Quality of Power (IEEE Cat. No.04EX951). doi:10.1109/ichqp.2004.1409350Boyajian, A., & McCarty, O. P. (1931). Physical Nature of Neutral Instability. Transactions of the American Institute of Electrical Engineers, 50(1), 317-327. doi:10.1109/t-aiee.1931.5055789Gates, B. G. (1936). Neutral inversion in power systems. Journal of the Institution of Electrical Engineers, 78(471), 317-325. doi:10.1049/jiee-1.1936.0051Clarke, E., Crary, S. B., & Peterson, H. A. (1939). Overvoltages During Power-System Faults. Transactions of the American Institute of Electrical Engineers, 58(8), 377-385. doi:10.1109/t-aiee.1939.5057977Concordia, C., & Peterson, H. A. (1941). Arcing faults in power systems. Electrical Engineering, 60(6), 340-346. doi:10.1109/ee.1941.6432165Mortlock, J. R., & Dobson, C. M. (1947). Neutral earthing of three-phase systems, with particular reference to large power stations. Journal of the Institution of Electrical Engineers - Part II: Power Engineering, 94(42), 549-568. doi:10.1049/ji-2.1947.0152Rocha, A. C. O., Souza, W. M., & Mendes, J. C. (s. f.). Practical experiences in the analysis of abnormal voltages due to neutral instability. 2004 IEEE/PES Transmision and Distribution Conference and Exposition: Latin America (IEEE Cat. No. 04EX956). doi:10.1109/tdc.2004.1432511Raunig, C., Schmautzer, E., Fickert, L., Achleitner, G., & Obkircher, C. (2009). Displacement voltages in resonant grounded grids caused by capacitive coupling. IET Conference Publications. doi:10.1049/cp.2009.0692Konotop, I., Novitskiy, A., & Westermann, D. (2014). Constraints on the use of local compensation for the correction of neutral voltage displacement caused by the influence of nearby power lines. 2014 Electric Power Quality and Supply Reliability Conference (PQ). doi:10.1109/pq.2014.6866832Kai, L., Guojie, X., Xiaojing, G., Kun, Y., Duohong, C., Ran, L., … Xiangjun, Z. (2018). Method for Suppressing Neutral Point Displacement Overvoltage and Suppression Circuit in Distribution Network. 2018 China International Conference on Electricity Distribution (CICED). doi:10.1109/ciced.2018.8592153Harner, R., & Owen, R. (1971). Neutral Displacement of Ungrounded Capacitor Banks During Switching. IEEE Transactions on Power Apparatus and Systems, PAS-90(4), 1631-1638. doi:10.1109/tpas.1971.293151Jinglu, L., Xin, W., & Chunyan, S. (2006). Discussion on Abnormal Rise of Displacement Voltage of Neutral Point in Compensation Electric Network and its Control Measures. 2006 International Conference on Power System Technology. doi:10.1109/icpst.2006.321700Emanuel, A. E. (2010). Power Definitions and the Physical Mechanism of Power Flow. doi:10.1002/9780470667149Czarnecki, L. S. (1988). Orthogonal decomposition of the currents in a 3-phase nonlinear asymmetrical circuit with a nonsinusoidal voltage source. IEEE Transactions on Instrumentation and Measurement, 37(1), 30-34. doi:10.1109/19.2658Hyosung Kim, Blaabjerg, F., & Bak-Jensen, B. (2002). Spectral analysis of instantaneous powers in single-phase and three-phase systems with use of p-q-r theory. IEEE Transactions on Power Electronics, 17(5), 711-720. doi:10.1109/tpel.2002.802188Willems, J. L., Ghijselen, J. A., & Emanuel, A. E. (2005). The Apparent Power Concept and the IEEE Standard 1459-2000. IEEE Transactions on Power Delivery, 20(2), 876-884. doi:10.1109/tpwrd.2005.844267Fortescue, C. L. (1918). Method of Symmetrical Co-Ordinates Applied to the Solution of Polyphase Networks. Transactions of the American Institute of Electrical Engineers, XXXVII(2), 1027-1140. doi:10.1109/t-aiee.1918.4765570Chroma Programmable AC Power Source 61700 https://www.chromausa.com/product/3-phase-programmable-ac-source-61700/Processor Board PCM-9581 http://advdownload.advantech.com/productfile/Downloadfile4/1-124ET90/PCM-9581_user_manual_Ed2.pdfData Acquisition Board PCI-6220 https://www.ni.com/documentation/en/multifunction-io-device/latest/pci-6220/overview/Voltage Transducer LV 25-P https://www.lem.com/en/lv-25pAC Current Clamp i5sPQ3 https://www.fluke.com/es-es/producto/accesorios/pinzas-de-corriente/fluke-i5spq3Resistances DL1017R https://www.delorenzoglobal.com/image/power-engineering-modules.pd

Analysis of Wind Generator Operations under UnbalancedVoltage Dips in the Light of the Spanish Grid Code

[EN] Operation of doubly fed induction generators subjected to transient unbalanced voltage dips is analyzed in this article to verify the fulfillment of the Spanish grid code. Akagi's p-q theory is not used for this study, because control of the electronic converter is not the main goal of the paper, but rather to know the physical phenomena involved in the wind turbine when voltage dips occur. Hence, the magnetizing reactive power of the induction generators and their components, which are related with the magnetic fields and determine operation of these machines, are expressed through the reactive power formulations established in the technical literature by three well-known approaches: the delayed voltage (DV) method, Czarnecki's Current's Physical Components (CPC) theory and Emanuel's approach. Non-fundamental and negative-sequence components of the magnetizing reactive power are respectively established to define the effects of the distortion and voltage imbalances on the magnetic fields and electromagnetic torques. Also, fundamental-frequency positive-sequence and negative-sequence reactive powers are decomposed into two components: due to the reactive loads and caused by the imbalances. This decomposition provides additional information about the effects of the imbalances on the main magnetic field and electromagnetic torque of the induction generator. All the above mentioned reactive powers are finally applied to one actual wind turbine subjected to a two-phase voltage dip in order to explain its operation under such transient conditions. © 2011 by the authors.León Martínez, V.; Montañana Romeu, J. (2011). Analysis of Wind Generator Operations under UnbalancedVoltage Dips in the Light of the Spanish Grid Code. Energies. 4(8):1148-1162. doi:10.3390/en4081148S1148116248Emanuel, A. E. (1999). Apparent power definitions for three-phase systems. IEEE Transactions on Power Delivery, 14(3), 767-772. doi:10.1109/61.772313Active and Reactive Power Formulations for Grid Code Requirements Verificationhttp://www.intechopen.com/articles/show/title/active-and-reactive-power-formulations-for-grid-code-requirements-verificationAkagi, H., Kanazawa, Y., & Nabae, A. (1984). Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components. IEEE Transactions on Industry Applications, IA-20(3), 625-630. doi:10.1109/tia.1984.4504460Hyosung Kim, Blaabjerg, F., & Bak-Jensen, B. (2002). Spectral analysis of instantaneous powers in single-phase and three-phase systems with use of p-q-r theory. IEEE Transactions on Power Electronics, 17(5), 711-720. doi:10.1109/tpel.2002.802188Czarnecki, L. (2003). Comparison of instantaneous reactive power p–q theory with theory of the current’s physical components. Electrical Engineering, 85(1), 21-28. doi:10.1007/s00202-002-0137-3Czarnecki, L. S. (2004). On Some Misinterpretations of the Instantaneous Reactive Power<tex>$phbox-q$</tex>Theory. IEEE Transactions on Power Electronics, 19(3), 828-836. doi:10.1109/tpel.2004.826500Salles, M. B. C., Hameyer, K., Cardoso, J. R., Grilo, A. P., & Rahmann, C. (2010). Crowbar System in Doubly Fed Induction Wind Generators. Energies, 3(4), 738-753. doi:10.3390/en304073

Load Losses and Short-Circuit Resistances of Distribution Transformers According to IEEE Standard C57.110

[EN] Load losses determine transformers¿ efficiency and life, which are limited by overheating and deterioration of their elements. Since these losses can be characterized by short-circuit resistances, in this article, we have developed expressions for the short-circuit resistances of three-phase transformers according to IEEE Standard C57.110. Imposing the condition that these resistances must cause load losses of the transformer, two types of short-circuit resistance have been established: (1) the effective resistance of each phase (Rcc,z) and (2) the effective short-circuit resistance of the transformer (Rcc,e f ). The first is closely related to the power loss distribution within the transformer; (2) the second is just a mathematical parameter. Applying these resistances to the 630 kVA oil-immersed distribution transformer of a residential network, we have concluded that both types of resistances determine the total load losses of the transformer. However, only Rcc,z accurately provides the load losses in each phase. Rcc,e f can give rise to errors more significant than 16% in calculating these losses, depending on imbalances in the harmonic currents.This research and APC was funded by the Generalitat Valenciana within the ValREM Project (CIAICO/2022/007).León-Martínez, V.; Peñalvo-López, E.; Andrada-Monrós, C.; Saiz, JÁ. (2023). Load Losses and Short-Circuit Resistances of Distribution Transformers According to IEEE Standard C57.110. Inventions. 8(6):1-16. https://doi.org/10.3390/inventions80601541168

Methodology and Necessary Equipment to Mitigate Capacity Limitations Caused by COVID-19 in Teaching Laboratories

[EN] The reduction of the space available for students in the classrooms of teaching laboratories, due to the pandemic caused by the SARS-CoV-2, requires the provision of the laboratories with additional equipment, as well as the application of procedures or protocols that guarantee that all students receive practical education with levels of quality similar to those existing in face-to-face classes, prior to the arrival of the coronavirus. This paper describes the methodology and resources used to teach practical classes in one of the Electrical Engineering teaching laboratories, at the Polytechnic University of Valencia. The use of web cameras, complemented with the use of the Microsoft Teams platform, has allowed all students actively attend laboratory classes in real time, within the established schedule, some in person and others in online modePeñalvo-López, E.; León-Martínez, V.; Montañana-Romeu, J.; Cárcel-Carrasco, J. (2021). Methodology and Necessary Equipment to Mitigate Capacity Limitations Caused by COVID-19 in Teaching Laboratories. IATED. 6671-6676. https://doi.org/10.21125/inted.2021.1330S6671667

Relationship between Buchholz's Apparent Power and Instantaneous Power in Three-Phase Systems

[EN] Similarly to how Steinmetz developed his theory of alternating current in single-phase sinusoidal systems, a few formal relationships between expressions of the instantaneous and Buchholz's apparent power in three-phase systems were identified in this paper. Based on these relationships, a methodology to express Buchholz's apparent power and its components in any three-phase, wye-configured system-sinusoidal or non-sinusoidal, balanced or unbalanced-through instantaneous power expressions was established. The application of the proposed method to the entire system allowed the determination of a novel quantity referred to as neutral-displacement power, which measured the impacts of the phenomena caused by the neutral path operation on the values of the source and load apparent power. These impacts were analyzed using a real-world urban installation with a neutral conductor deterioration simulation via an Excel platform as an application example.This research was funded by the European Commission, grant number 847132. The APC was funded by the European Commission, grant number 847132. We gratefully thank Eléctrica de Vinalesa, S.L.U., for allowing us to take measurements using their electrical networks, and MDPI (www.mdpi.com/authors/english) for their English language editing. The authors deeply thank the European Commission for their support and funding provision.León-Martínez, V.; Montañana-Romeu, J.; Peñalvo-López, E.; Valencia-Salazar, I. (2020). Relationship between Buchholz's Apparent Power and Instantaneous Power in Three-Phase Systems. Applied Sciences. 10(5):1-15. https://doi.org/10.3390/app10051798S115105Czarnecki, L. S. (1987). What is wrong with the Budeanu concept of reactive and distortion power and why it should be abandoned. IEEE Transactions on Instrumentation and Measurement, IM-36(3), 834-837. doi:10.1109/tim.1987.6312797Czarnecki, L. S. (1988). Orthogonal decomposition of the currents in a 3-phase nonlinear asymmetrical circuit with a nonsinusoidal voltage source. IEEE Transactions on Instrumentation and Measurement, 37(1), 30-34. doi:10.1109/19.2658Czarnecki, L. S. (2008). Currents’ Physical Components (CPC) concept: A fundamental of power theory. 2008 International School on Nonsinusoidal Currents and Compensation. doi:10.1109/isncc.2008.4627483CZARNECKI, L. (2015). Currents’ Physical Components (CPC) in Three-Phase Systems with Asymmetrical Voltage. PRZEGLĄD ELEKTROTECHNICZNY, 1(6), 42-49. doi:10.15199/48.2015.06.06Emanuel, A. E. (1999). Apparent power definitions for three-phase systems. IEEE Transactions on Power Delivery, 14(3), 767-772. doi:10.1109/61.772313Pajic, S., & Emanuel, A. E. (2006). Modern Apparent Power Definitions: Theoretical Versus Practical Approach—The General Case. IEEE Transactions on Power Delivery, 21(4), 1787-1792. doi:10.1109/tpwrd.2006.876647Depenbrock, M. (1993). The FBD-method, a generally applicable tool for analyzing power relations. IEEE Transactions on Power Systems, 8(2), 381-387. doi:10.1109/59.260849Ferrero, A. (2007). Definitions of electrical quantities commonly used in non-sinusoidal conditions. European Transactions on Electrical Power, 8(4), 235-240. doi:10.1002/etep.4450080403Curtis, H. L., & Silsbee, F. B. (1935). Definitions of power and related quantities. Electrical Engineering, 54(4), 394-404. doi:10.1109/ee.1935.6539147Emanuel, A. E., & Orr, J. A. (s. f.). The effect of neutral path impedance on voltage and current distortion. Part I. symmetrical and balanced three-phase systems. 2004 11th International Conference on Harmonics and Quality of Power (IEEE Cat. No.04EX951). doi:10.1109/ichqp.2004.1409351Emanuel, A. E., & Orr, J. A. (s. f.). The effect of neutral path impedance on voltage and current distortion. Part II. Imbalanced three-phase systems. 2004 11th International Conference on Harmonics and Quality of Power (IEEE Cat. No.04EX951). doi:10.1109/ichqp.2004.1409350Blasco, P. A., Montoya-Mira, R., Diez, J. M., Montoya, R., & Reig, M. J. (2019). Compensation of Reactive Power and Unbalanced Power in Three-Phase Three-Wire Systems Connected to an Infinite Power Network. Applied Sciences, 10(1), 113. doi:10.3390/app10010113Akagi, H., Kanazawa, Y., & Nabae, A. (1984). Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components. IEEE Transactions on Industry Applications, IA-20(3), 625-630. doi:10.1109/tia.1984.4504460Czarnecki, L. S. (2006). Could Power Properties of Three-Phase Systems Be Described in Terms of the Poynting Vector? IEEE Transactions on Power Delivery, 21(1), 339-344. doi:10.1109/tpwrd.2005.852353Jeon, S. (2015). Properties of the generalised power theory: universality and partitioning/augmentation properties. IET Generation, Transmission & Distribution, 9(15), 2126-2134. doi:10.1049/iet-gtd.2014.0303Czarnecki, L. S. (2015). Critical comments on the Conservative Power Theory (CPT). 2015 International School on Nonsinusoidal Currents and Compensation (ISNCC). doi:10.1109/isncc.2015.7174713Artemenko, M. Y., & Batrak, L. M. (2017). The new formula for apparent power and power losses of three-phase four-wire system. 2017 IEEE 37th International Conference on Electronics and Nanotechnology (ELNANO). doi:10.1109/elnano.2017.793978

Methodology for designing an Energy Community and its application to the municipality of Vinalesa

[EN] Energy communities represent a new energy management model for the use of local energy resources, in which different social actors participate in search of energy, environmental, social and economic benefits. Nevertheless, there is still a lack of concise guidelines in the literature dealing with the more technical aspects of energy communities. The aim of this article is presenting a methodology to support the design of new energy communities based on energetic, economic and environmental conditions in order to analyse their technical and economic viability. The methodology is supported by Homer Grid modelling software for simulating and optimising possible energy scenarios. This is better suited to energy communities connected to the grid, with renewable energy generation assets from local resources and with an equitable distribution of benefits for all members. The methodology has been applied to a case study in the village of Vinalesa, sizing the community's generation assets as well as the electricity tariff. Their implementation in the case study results in an installation of 870 kW of photovoltaic energy and capacity storage of 1.08 MWh in Lithium-Ion batteries that allows the residents of Vinalesa have additional savings of around 16.4% in their electricity bill.Molina-Cañamero, L.; Peñalvo-López, E.; León-Martínez, V.; Montañana-Romeu, J. (2022). Methodology for designing an Energy Community and its application to the municipality of Vinalesa. Renewable Energy and Power Quality Journal. 20:729-734. https://doi.org/10.24084/repqj20.4157297342

Inteligencia emocional y rendimiento académico en estudiantes de enseñanza secundaria. Diferencias de género

[Resumen] Con nuestro estudio pretendemos encontrar relaciones entre la inteligencia emocional y el rendimiento académico con una muestra de 344 alumnos de entre 14 y 16 años de edad (1º y 2º ESO). Hemos utilizado para evaluar la inteli- gencia emocional medidas de autoinforme, concretamente el TMMS-24 (Trait Meta Mood Scale) y para el rendimiento académico hemos utilizado no sólo medidas globales como la nota media y el número de suspensos, también la calificación en cada una de las materias básicas de la ESO: Matemáticas, Lengua, Inglés, Ciencias Sociales y Ciencias Naturales. Por último, debido a que existen diferencias en inte- ligencia emocional asociadas al género, supo- nemos que las correlaciones entre el rendimien- to escolar e inteligencia emocional serán dife- rentes entre chicos y chicas.[Abstract] Our study aims to find relationships bet- ween emotional intelligence and academic performance with a sample of 344 students between 14 and 16 years of age (1st and 2nd ESO). We used self-report measures to assess emotional intelligence, namely TMMS-24 (Trait Meta Mood Scale) and for the academic performance measures we have used not only the global average and the number of failures, but the grades in each of the core subjects of the ESO: Mathematics, Language, English, Social Sciences and Natural Sciences. Finally, due to differences in emotional intelligence related to gender, we assume that the correla- tions between school performance and emo- tional intelligence are different between boys and girls

Phase calibration of spatial light modulators by means of Fresnel images

Reliable application of spatial light modulators (SLMs) as programmable diffractive optical elements requires a thorough calibration. In this paper, we propose a method for calibrating SLMs based on the evaluation of Fresnel images. Fresnel images generated by a binary phase diffraction grating consist of binary irradiance distributions whose visibility depends on the phase modulation. By displaying on our device a diffraction grating with a binary phase step along one direction and a linearly increasing phase along the orthogonal direction, we perform a complete phase calibration. In this way, the phase modulation for every pixel and for every value of the entrance signal can be determined experimentally. Additionally, data acquisition can be significantly simplified with this schem

Poincaré-sphere representation of phase-mostly twisted nematic liquid crystal spatial light modulators

We establish necessary conditions in order to design a phase-only wave front modulation system from a liquid crystal display. These conditions determine the dependence of the polarization state of the light emerging from the display on the addressing gray level. The analysis, which is carried out by means of the coherence-matrix formalism, includes the depolarization properties of the device. Two different types of polarization distributions at the output of the liquid crystal cells are found. This approach is applied to a twisted nematic liquid crystal display. In this case, an optimization algorithm must be designed in order to select the input polarization state that leads to the required distributions. We show that the Poincaré-sphere representation provides a convenient framework to design the optimization algorithm as it allows for a reduced number of degrees of freedom. This feature significantly decreases the computation time. Laboratory results are presented for a liquid crystal-onsilicon display showing a phase modulation depth greater than 2π radians with an intensity variation lower than 6%. In addition, a hybrid-ternary modulation (HTM), an operation regime employed in holographic data storage, is achieve