Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

Statistical relationship between RMS and QP spectra of voltage measurements in the 9–150 kHz range

The main objective of this work is to obtain an empirical relationship between the root-mean-square and the quasi-peak spectra of voltage recordings in the electrical grid, based on a statistical analysis of a set of on-field measurements for the CISPR Band A (9–150 kHz). The lack of a relationship between the weighting root-mean-square and quasi-peak detectors implies the impossibility of calculating quasi-peak (QP) spectra from root-mean-square (RMS) measurements. It is of great interest that quasi-peak values can be estimated by simple calculations from RMS values, so that comparison to compatibility levels could be applied. This work defines an empirical relationship between the statistical variation of instantaneous RMS values over time, the maximum RMS value of these instantaneous values and the QP output. This relationship is described in the form of a simple equation that can be applied to RMS provided by the RM-A method, specifically developed for the CISPR Band A. A method for the fast assessment of QP values from simple RMS receivers is proposed as a potential application of the numerical RMS-QP relationship. Both the numerical RMS-QP relationship and its application as a simple and fast assessment method are evaluated with disturbances recorded in the low voltage grid.This project (18NRM05) has received funding from the EMPIR program co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation program. This work was funded in part by the Basque Government under the grants IT1436–22 and PRE_2022_2_0074. This work was supported in part through grant PID2021–124706OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe

Supraharmonics in low voltage networks

This document presents a methodology for the identification of supraharmonic emissions (current and voltage conducted emissions between 2-150 kHz) at the end-user side of the distribution grid, using low power LED lamps as Equipment Under Test (EUT). First chapter presents a brief classification of power quality disturbances and describes those related to waveform distortion. Second chapter describes the measurement and experimental setups used to assess the supraharmonic emissions from selected EUT. Third chapter explains the methodology for the identification of supraharmonic emissions when EUT perform in single operation, and fourth chapter shows the interaction of such emissions for EUT in simultaneous operation. Along with a set of experimental combinations, supraharmonic emissions and their more relevant metrology aspects are discussed through the text. Results show how voltage and current supraharmonic emissions are (or not) affected by different variations in voltage source, equivalent network impedance, measurement setup and circuit topology of selected EUT. This research is aimed to contribute to the understanding and systematic assessment of supraharmonic emissions, with a special emphasis on metrological aspects and statistical methods for their identification.Este documento presenta una metodología para la identificación de emisiones supraarmónicas (emisiones conducidas de tensión y corriente entre 2-150 kHz) en el lado del usuario final de la red de distribución, utilizando lámparas LED de baja potencia como Equipo Bajo Prueba (EBP). El primer capítulo presenta una breve clasificación de las perturbaciones de la calidad de potencia y describe aquellas relacionadas con la distorsión de la forma de onda. El segundo capítulo describe la configuración experimental y de medición utilizada para evaluar las emisiones supraarmónicas de los EBP seleccionados. El tercer capítulo explica la metodología usada para la identificación de las emisiones supraarmónicas cuando los EBP funcionan de manera individual, y el cuarto capítulo muestra la interacción de dichas emisiones en la operación simultánea de los EBP. Junto con un conjunto de combinaciones experimentales, las emisiones supraarmónicas y sus aspectos metrológicos más relevantes se analizan a través del texto. Los resultados muestran cómo las emisiones supraarmónicas de tensión y corriente se ven (o no) afectadas por diferentes variaciones en la fuente de tensión, la impedancia de red equivalente, el sistema de medición y la topología del circuito del EBP seleccionado. El objetivo de esta investigación es contribuir a la comprensión y el estudio sistemático de las emisiones supraarmónicas, con especial énfasis en los aspectos metrológicos y los métodos estadísticos para su identificación.Maestrí

On the suitability of the CISPR 16 method for measuring conducted emissions in the 2–150kHz range in low voltage grids

The IEC 61000–2–2 standard defines the compatibility levels to evaluate the conducted disturbances in the low voltage grid for the 2-150 kHz range. For frequencies 9–150 kHz, they are defined in terms of quasi peak values measured according to CISPR 16–1–1 standard, but no clear guidance is given on how to apply this standard to grid measurements. The definition of the method in CISPR 16–1–1 accepts a wide range of different implementations, all of them fulfilling the compliance requirements. The reasons are that the standard does not propose a fixed implementation but a ‘black-box’ approach, and some of the proposed configuration values are non-normative and/or wide tolerances are allowed. In this context, some parameters have a pivotal role in the results provided by the method. The impact of variation of these parameters on the measurement results is addressed in this work. In particular, the accuracy requirements and the reproducibility issues of the standard are studied. For that purpose, a high number of different compliant implementations have been developed and the influence of different features of the CISPR 16–1–1 method on the results of these implementations is identified and analyzed. The results show that the wide tolerances allowed by the CISPR 16 specification impede the comparison of results provided by measuring receivers based on different implementations of the standard. Results of the study also show that reproducibility issues for the same input signal may be relevant and generate inconsistences. Moreover, a fixed specific configuration does not ensure that uncertainty issues are solved, as the technical approach used in the implementation of the damped meter has a strong influence on the outputs. An unambiguous guidance of digital implementation of the standard could fix these issues

The Measurement and Analysis of High-Frequency Conducted Disturbances in Power Networks

Electrical and Electronic Engineerin

Investigación sobre la flexibilidad de la demanda en redes eléctricas inteligentes: control directo de cargas

In recent decades, the European Union has made decisive efforts to maintain its global leadership in renewable energies to meet climate change targets resulting from international agreements. There is a deliberate intention to reduce the usage of non-renewable energy sources and promote the exploitation of renewable generation at all levels as shown by energy production data within the Eurozone. The electricity sector illustrates a successful implementation of these energy policies: The electricity coming from combustible fuels was at historical lows in 2018, accounting for 83.6 % of the electricity generated from this source in 2008. By contrast, the pool of renewables reached almost 170 % of the 2008 production. Against this background, power systems worldwide are undergoing deep-seated changes due to the increasing penetration of these variable renewable energy sources and distributed energy resources that are intermittent and stochastic in nature. Under these conditions, achieving a continuous balance between generation and consumption becomes a challenge and may jeopardize the system stability, which points out the need of making the power system flexible enough as a response measure to this trend. This Ph.D. thesis researches one of the principal mechanisms providing flexibility to the power system: The demand-side management, seen from both the demand response and the energy efficiency perspectives. Power quality issues as a non-negligible part of energy efficiency are also addressed. To do so, several strategies have been deployed at a double level. In the residential sector, a direct load control strategy for smart appliances has been developed under a real-time pricing demand response scheme. This strategy seeks to minimize the daily cost of energy in presence of diverse energy resources and appliances. Furthermore, a spread spectrum technique has also been applied to mitigate the highfrequency distortion derived from the usage of LED technology lighting systems instead of traditional ones when energy efficiency needs to be improved. In the industrial sector, a load scheduling strategy to control the AC-AC power electronic converter in charge of supporting the electric-boosted glass melting furnaces has been developed. The benefit is two-fold: While it contributes to demand flexibility by shaving the peaks found under conventional control schemes, the power quality issues related to the emission of subharmonics are also kept to a minimum. Concerning the technologies, this Ph.D. thesis provides smart solutions, platforms, and devices to carry out these strategies: From the application of the internet of things paradigm to the development of the required electronics and the implementation of international standards within the energy industry.En las últimas décadas, la Unión Europea ha realizado esfuerzos decisivos para mantener su liderazgo mundial en energías renovables con el fin de cumplir los objetivos de cambio climático resultantes de los acuerdos internacionales. Muestra una intención deliberada de reducir el uso de fuentes de energía no renovable y promover la explotación de la generación renovable a todos los niveles, como demuestran los datos de producción de energía en la eurozona. El sector de la electricidad ilustra un caso de éxito de estas políticas energéticas: la electricidad procedente de combustibles fósiles estaba en mínimos históricos en 2018, representando el 83,6 % de la electricidad generada a partir de esta fuente en 2008; en cambio, el grupo de renovables alcanzó casi el 170 % de la producción de 2008. En este contexto, los sistemas eléctricos de todo el mundo están experimentando profundos cambios debido a la creciente penetración de estas fuentes de energía renovable y de recursos energéticos distribuidos que son de naturaleza variable, intermitente y estocástica. En estas condiciones, lograr un equilibrio continuo entre generación y consumo se convierte en un reto y puede poner en peligro la estabilidad del sistema, lo que señala la necesidad de flexibilizar el sistema eléctrico como medida de respuesta a esta tendencia. Esta tesis doctoral investiga uno de los principales mecanismos que proporcionan flexibilidad al sistema eléctrico: la gestión de la demanda vista tanto desde la perspectiva de la respuesta a la demanda como de la eficiencia energética. También se abordan los problemas de calidad de suministro entendidos como parte no despreciable de la eficiencia energética. Para ello, se han desplegado varias estrategias a un doble nivel. En el sector residencial, se ha desarrollado una estrategia basada en el control directo de cargas para los electrodomésticos inteligentes siguiendo un esquema de respuesta a la demanda con precios en tiempo real. Esta estrategia busca minimizar el coste diario de la energía en presencia de diversos recursos energéticos y electrodomésticos. Además, también se ha aplicado una técnica de espectro ensanchado para mitigar la distorsión de alta frecuencia derivada del uso de sistemas de iluminación con tecnología LED, empleados para la mejora de la eficiencia energética frente a las tecnologías convencionales. En el sector industrial, se ha desarrollado una estrategia de planificación de cargas para controlar el convertidor AC-AC de los hornos de fundición de vidrio con soporte eléctrico. El beneficio es doble: mientras que se contribuye a la flexibilidad de la demanda al eliminar los picos encontrados en los esquemas de control convencionales, también se reducen al mínimo los problemas de calidad de suministro relacionados con la emisión de subarmónicos. En cuanto a las tecnologías, esta tesis doctoral aporta soluciones, plataformas y dispositivos inteligentes para llevar a cabo estas estrategias: desde la aplicación del paradigma del internet de las cosas hasta el desarrollo de la electrónica necesaria y la implementación de estándares internacionales dentro de la industria energética

Analysis of the use of the Hanning Window for the measurement of interharmonic distortion caused by close tones in IEC standard framework

Producción CientíficaThe widespread use of devices based on power electronics and other nonlinear loads has led to an increase in harmonic distortion that affects the quality of power systems. Therefore, the correct measurement of harmonic and interharmonic content is necessary. The International Electrotechnical Commission (IEC) standards define the concepts of spectral and time grouping required for such measurements. This paper demonstrates that the procedures defined in the IEC standards are not sufficiently accurate when several close interharmonic tones interact due to the lack of stability of the values that the Discrete Fourier Transform obtains in each sampling window, and to the inaccuracy in the measurement of interharmonic groups and rates when using the Hanning window. This paper proposes novel solutions based on time aggregation and the use of other groupings and alternative windows. The results obtained are compared with the results produced by applying the rectangular window indicated in the standards, using sensitivity analysis varying one of the tones and using experimental results measuring the output signals of frequency inverters driving induction motors. The proposed method achieves greater accuracy and stability in the measurement of spectral groupings and their related distortion rates in signals with abundant and dispersed interharmonic content

A study of the effects of time aggregation and overlapping within the framework of IEC standards for the measurement of harmonics and interharmonics

Producción CientíficaThe increasing incorporation of power electronics and other non-linear loads, in addition to their energy advantages, also implies a poor power quality, especially as regards harmonic pollution. Different solutions have been proposed to measure harmonic content, taking the International Electrotechnical Commission (IEC) standards as a reference. However, there are still some issues related to the measurement of the harmonic, and especially, interharmonic content. Some of those questions are addressed in this work, such as the problem derived from the instability of the values obtained by applying the discrete Fourier transform to each sampling window, or the appearance of local peaks when there are tones separated by multiples of the resolution. Solutions were proposed based on time aggregation and the overlapping of windows. The results demonstrate that aggregation time, window type, and overlapping can improve the accuracy in harmonic measurement using Fourier transform-based methods, as defined in the standards. The paper shows the need to consider spectral and time groupings together, improving results by using an appropriate percentage of overlap and an adaptation of the aggregation time to the harmonic content