Good power quality is not only determined by uninterruptable power supply, voltage deviations also affect the function of the network and the equipment connected. Electromagnetic disturbances as flicker, harmonics, interharmonics and unbalance are decreasing the power quality. How are the measurement methods and restrictions stated, to keep the voltagedeviations within reasonable limits and thereby maintaining the networkfunction? Lillgrund wind farm has power quality restrictions set by E.ON Elnät to fulfil in the connection point to the subtransmission network. In addition isa fault ride through requirement set by SVK. All equipment connected tothe network are introducing voltage changes, which can be measured at the point of connection. The scope of the thesis has been to explicitly determine Lillgrund‟s emissions. Three-phase voltage and current measurements have been performed, with measurement systems comprising different bandwidth, to analyse the power quality parameters.Comparisons between standard documentation and technical specifications have been made in order to precise what is considered as good power quality and how it can be measured accurately.

In this research work, the performance of a C-type, 2nd harmonic power filter is optimized by the use of a thyristor switched damping resistor. In the design of conventional C-type, 2nd harmonic filters / the resistance of permanently connected damping resistor is to be optimized for minimization of voltage stresses on filter elements arising from switchings in transient state and for maximization of filtering effectiveness in the steady-state. Transformer inrush current during energization of power transformers and connection of filter bank to the supply are the major causes of voltage stresses arising on filter elements in transient state. These can be minimized by designing a highly damped C-type filter (low damping resistor) at the expense of inadequate filtering performance and high losses in the steady-state. On the other hand, higher damping resistance (high quality factor) is to be chosen in the design of C-type filter for satisfactory filtering of 2nd harmonic current component at the expense of higher voltage rating for capacitor bank and hence a more costly filter bank design. This drawback of conventional C-type 2nd harmonic filter circuit can be eliminated by subdividing damping resistor into two parallel parts / one is permanently connected while the other is connected to and disconnected from the circuit by back-to-back connected thyristor assemblies. The use of light triggered thyristors provides isolation between power stage and control circuit, and hence allows outdoor installation.

No description available.

Power system harmonics and interharmonics are power quality concerns that have received a great deal of attention in recent years. These phenomena can have several adverse effects on power system operation. The main harmonic and interharmonic sources are devices based on power electronics. An emerging class of harmonic sources is comprised of power electronic-based home appliances. These appliances are dispersed throughout the low-voltage distribution system, and their collective impact can result in unacceptable levels of voltage distortion. The characterization of home appliances based on their harmonic currents is an important step toward understanding the impact of these devices. This thesis presents an evaluation of the relative severity of the harmonic currents from these devices, and the impact of the disparity of the harmonic current phase angles. Typically, the voltage supplied to each harmonic source is already distorted. This distortion causes a change of the harmonic current magnitudes (traditionally referred to as the attenuation effect). Common harmonic analysis methods cannot take this variation into account because they use a typical harmonic current source model specified by a supply voltage having little or no distortion. This thesis characterizes the harmonic attenuation effect of power electronic-based appliances. One of the findings is that harmonic amplification, rather than attenuation, can occur under credible voltage conditions. This finding had not been made previously. In order to include the harmonic attenuation/amplification in appliance modeling, a measurement-based harmonic modeling technique is proposed. One of the most economic and effective ways to mitigate harmonics in power systems is through the use of harmonic shunt passive filters. These filters can be of many topologies. Selecting these topologies is a task that, today, depends on the experience and judgment of the filter designer. An investigation is carried out on the common filter topologies, and the most cost-effective topologies for mitigating harmonics are identified. As many of the larger harmonic loads also generate interharmonics, interharmonics have become prevalent in today’s medium-voltage distribution system. Mitigation cannot be carried out until the interharmonic-source location is known. A method for interharmonic source determination is proposed and then verified through simulation and field measurement studies.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / The harmonic pollution in distribution systems has increased significantly due to the widespread use of nonlinear loads. The current and voltage harmonics deteriorate the power quality supplied by feeders and compromise the efficiency of the equipments connected to the electric network. These equipments require a sinusoidal waveform to ensure its suitable functioning, as in the case of transformers. Its performance and mainly the protection depend largely of the insulation of the windings, which is closely related to the operating temperature. Concerning this, this work proposes a study on energy efficiency, whose main aim is to investigate the transformer heating in the presence of harmonics. It is presented comparative measurements between the increasing of temperature caused a 10kVA three-phase dry-type transformer when submitted to sinusoidal voltages and currents and nonsinusoidal. Later a comparison was made between experimental results and the simulations obtained from a 3D model of the same transformer developed in the software COMSOL Multiphysics. It was observed that the higher harmonic current distortion, the higher temperature at the core, and especially in the coils. While in the case of supply voltage with interharmonic and subharmonic, the impact on transformer heating become much more pronounced in relation to the cases in which their supply voltage is sinusoidal or contains harmonics of the 3rd, 5th and 7th orders. The errors checked between the measurements and the results of simulations were considered acceptable. With the refinement of the model, will be possible use it in order to predict the temperature spectrum of transformers at the begining of the design, mainly in nonlinear conditions of operation. / A poluiÃÃo harmÃnica em sistemas de distribuiÃÃo tem aumentado significativamente devido ao uso generalizado de cargas nÃo lineares. HarmÃnicos de corrente e tensÃo deterioram a qualidade da energia fornecida pelos alimentadores e comprometem a eficiÃncia dos equipamentos conectados à rede elÃtrica. Estes equipamentos necessitam de uma forma de onda senoidal para garantir seu funcionamento adequado, como à o caso dos transformadores. Seu desempenho e principalmente a proteÃÃo dependem, em grande parte, do isolamento dos enrolamentos, o qual està intimamente relacionado com a temperatura de operaÃÃo. Concernente a isso, este trabalho propÃe um estudo sobre eficiÃncia energÃtica, cujo principal objetivo à investigar o aquecimento do transformador na presenÃa de harmÃnicos, apresentando mediÃÃes comparativas entre o aumento da temperatura causada em um transformador a seco trifÃsico de 10~kVA quando submetido a correntes e tensÃes senoidais e nÃo senoidais, e, posteriormente, uma comparaÃÃo entre os resultados experimentais e os de simulaÃÃes obtidas a partir de um modelo 3D do mesmo transformador desenvolvido no emph{software} COMSOL emph{Multiphysics}. Verificou-se que quanto maior a distorÃÃo harmÃnica de corrente, mais elevada à a temperatura no nÃcleo, e sobretudo nas bobinas. Enquanto que para tensÃo de alimentaÃÃo com inter-harmÃnico e sub-harmÃnico o impacto no aquecimento do transformador tornou-se bem mais acentuado em relaÃÃo a casos nos quais sua tensÃo de alimentaÃÃo à senoidal ou contÃm harmÃnicas de 3Â, 5 e 7 ordens. Os erros verificados entre as mediÃÃes e os resultados de simulaÃÃes foram considerados aceitÃveis. Com o refinamento do modelo, serà possÃvel empregÃ-lo a fim de prever o espectro de temperatura de transformadores em fase de projeto, principalmente sob condiÃÃes nÃo lineares de operaÃÃo.

In this report, studies on interharmonics from three different measurement sites are performed. The first site is a wind park with three turbines, where the measurements are performed at the point of common coupling of these three. The second site is a network which consists of a PV inverter and two types of EV chargers – a DC charger or an AC charger. Measurements are performed with three different set-ups in this site – only AC charger connected, only DC charger connected, and AC charger and PV inverter connected simultaneously. The third site where measurements were made is a microgrid using frequency control in order to signal how the microgrid should operate at the moment. The interharmonic analysis was conducted using desynchronized processing technique (DP) and Sliding-Window Estimation of Signal Parameters via Rotational Invariance Techniques (SlidingWindow ESPRIT or SWESPRIT). The result from the wind park is that closely and evenly spaced interharmonics can be seen when the current suddenly increases (could be fast variations in wind speed). It is however uncertain if these interharmonics are caused by spectral leakage or not since SWESPRIT estimates the fundamental frequency to vary drastically when wind speed varies. It is observed that the SWESPRIT estimation of fundamental frequency could be caused by sudden changes in phase angle as the current varies. Further investigation and analysis are needed. The result from the measurements on the site with EV chargers and a PV inverter is that eight distinct patterns can be observed. Some patterns appear to come from the upstream grid, while some appear to be caused by either one of the EV chargers or the PV inverter, or interaction between them. Further studies are needed. The result from the microgrid measurements is that two distinct patterns at high frequencies (above 1000 Hz) can be observed during grid connected mode and island mode, respectively. During transitions between grid connection and island mode or vice versa, the fundamental frequency varies drastically, and it is therefore hard to analyse potential interharmonics and draw inferences. Further studies are needed. Advantages and disadvantages, as well as ideas for improvements, of the two applied signal processing methods are discussed throughout the different case-studies.

Products produced by a Swedish company are requested to be investigated regarding their harmonic and inter-harmonic currents injected into the public supply system to comply with the Swedish standard SS-EN IEC 61000-3-2, Electromagnetic compatibility (EMC).    On behalf of Systemair Sweden AB, this bachelor thesis aims firstly to investigate if their product, PAFEC 4225 WH (Air Curtain), complies with standard SS-EN IEC 61000-3-2, and if not, what measures should be taken; and secondly to develop a low-cost instrument for the measurement of harmonics and inter-harmonics according to standard IEC 61000-4-7 related to the requirements on equipment used in standard SS-EN IEC 61000-3-2. To this purpose, the standards have been looked into thoroughly, the preconditions for measurements have been studied in detail, and external meetings with a consultant at Delta Development Technology AB have been performed. Measurements of the harmonic spectrum generated by PAFEC 4225 WH have been performed first at Systemair Sweden AB’s Technical center in Skinnskatteberg, and later at Delta Development in Västerås. After this, a low-cost instrument was developed, including hardware and software design and implementation. The hardware implementation consists of a circuit board designed using EasyEDA (an online PCB Design Tool), a NI myDAQ (a data acquisition device made by National Instruments), and an enclosure designed with Solidworks and made with a 3D-printer. The software implementation was conducted using LabVIEW – a graphical programming language.  A few measurements were performed using instruments complying IEC 61000-4-7 at Delta Development, and later with the low-cost instrument. Different line chokes were measured. The results showed that a 15 mH line choke connected in series with each motor would make the PAFEC 4225 WH comply with SS-EN IEC 61000-3-2. The results from the low-cost instrument did not match Delta Developments results regarding harmonic and inter-harmonic content. The difference could be caused by unfinished algorithm, different measurements conditions, and missing anti-aliasing-filter.          For the future work it is recommended that Systemair Sweden AB can either develop the low-cost instrument or buy an existing instrument that complies with IEC 61000-4-7, to enable to do measurements that comply with SS-EN IEC 61000-3-2. One does also need to investigate the grid during low activity or consider buying a signal generator for the purpose of fulfilling the preconditions to enable measurements. It is also recommended that further measurements are performed with the proposed line choke installed to check for any change in performance of the product.

El análisis de Fourier es el método fundamental para la medida de armónicos e interarmónicos en señales eléctricas y es el principio de análisis que establece la International Electrotechnical Commission para los instrumentos de medida. Con el objetivo de superar las limitaciones que lo hacen poco efectivo en determinadas condiciones se han propuesto otras técnicas de análisis como las wavelets. En esta tesis doctoral se explora esta alternativa en el campo de la calidad del suministro de energía eléctrica.Como aportación principal se presenta un nuevo método de medida de armónicos e interarmónicos basado en la Transformada Wavelet Packet compatible con el estándar de medida IEC 61000-4-7 de 2002. El método propuesto utiliza un árbol de descomposición wavelet, que en sus distintos niveles suministra la medida de armónicos e interarmónicos de la señal, así como su contenido subarmónico e información de sus variaciones en el dominio temporal.Se exponen las características principales del método en cuanto a la elección de la función wavelet madre, el banco de filtros que implementa el árbol de descomposición wavelet y el postprocesado que posibilita la compatibilidad con el estándar de medida. Se analizan las prestaciones del método en la medida de armónicos e interarmónicos, tanto en condiciones estacionarias como en el caso de pérdida de sincronía por variación de la frecuencia fundamental o variación de la ventana de muestreo de la señal, presencia de componentes no síncronas con la frecuencia de la red o presencia de componentes de amplitud variable. Por último, se expone la información que aporta el método para la estimación temporal de las componentes frecuenciales medidas.El método desarrollado junto con el método de IEC, se ha implementado sobre un equipo electrónico para adquisición y procesado de señal utilizando técnicas de instrumentación virtual. Se expone la estructura y características del hardware utilizado y del software desarrollado así como los resultados obtenidos en la medida del espectro frecuencial de señales de diferente naturaleza.Por último se resumen las conclusiones obtenidas y se proponen futuras líneas de investigación motivadas por la realización de esta tesis doctoral. / Fourier analysis is the fundamental method for the measurement of harmonics and interharmonics in electrical power systems and is the method proposed by the International Electrotechnical Commission (IEC) for standard measurement instruments. With the objective of overcoming the limitations in certain conditions, other techniques of analysis such as wavelets have been proposed. This doctoral thesis investigates alternatives in the field of the quality of the provision of electrical energy. The main contribution of this thesis is the proposal of a new method of measurement of harmonics and interharmonics based on the Wavelet Packet Transform compatible with the standard IEC 61000-4-7 of 2002. The method proposed simultaneously uses different levels of the same wavelet decomposition tree for the measurement of harmonic, interharmonic and subharmonic components in the input signal as well as their time evolution.The basic characteristics of the method in terms of the choice of the mother wavelet function, the bank of filters that implements the wavelet decomposition tree and the postprocessing to make the method compatible with the measurement standard are explained. The benefits of the method in the measurement of harmonics and interharmonics are analyzed, both in stationary conditions and in the case of loss of synchrony due to variation of the base frequency or variation of the sampling window of the signal, presence of nonsynchronous components with the frequency of the network or presence of components of variable amplitude. Finally, the information that the method provides about the temporal estimation of the measured frequencial components is described.The method developed and the IEC method have been implemented on a virtual instrument. The hardware used and the software developed are explained studying the performance of the instrument under different measurement conditions.Finally the conclusions obtained are summarized and future lines of investigation motivated by this doctoral thesis are proposed.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / In applications related to power converters, such as inverters, rectifiers and the use of active filters, the synchronization method represent a very important element in the performance of the control strategy of this equipment. The estimated values of the synchronism angle, frequency and amplitude determined by the synchronization algorithms present, facing strongly distorted signals with the presence of sub and interharmonics, high errors. This study presents two algorithms: one applied on single-phase electrical systems and one applied on three-phase electrical systems, with high immunity to interharmonics and subharmonics. First are presented the main synchronization systems that are used in the electrical power systems. In addition, will be presented the main causes and consequences of the presence of subharmonics and interharmnics in the system, as well as the mathematical modeling of the two algorithms with high rejection to these disturbances. Will be presented the simulation and the experimental results of the proposed algorithms and the comparison between these synchronization methods with particular methods present in the literature. As a result of the study, it can be seen that the proposed structures present a higher response time, but the error of the estimated signal with respect the fundamental component of the input signal is lower when compared to structures such as EPLL and structures based on SOGI. It was observed that the proposed synchronization methods are enabled to estimate the synchronism angle, the frequency and the fundamental component of the input signal adequately and can be used in control strategies of power converters. / Em aplicaÃÃes relacionadas à EletrÃnica de PotÃncia, como inversores, retificadores e a utilizaÃÃo de filtros ativos, o mÃtodo de sincronizaÃÃo representa um elemento chave no desempenho da estratÃgia de controle destes equipamentos. Os valores do Ãngulo de sincronismo, frequÃncia e amplitude estimados com determinados algoritmos de sincronizaÃÃo apresentam, diante de sinais fortemente distorcidos com a presenÃa de sub e inter-harmÃnicos, erros elevados. Neste trabalho sÃo apresentados dois algoritmos: um aplicado a sistemas elÃtricos monofÃsicos e outro aplicado a sistemas elÃtricos trifÃsicos, com elevada imunidade a inter-harmÃnicos e sub-harmÃnicos. Primeiramente sÃo apresentados os principais sistemas de sincronizaÃÃo utilizados em sistemas elÃtricos de potÃncia. AlÃm disso, sÃo apresentadas as principais causas e consequÃncias da presenÃa de sub-harmÃnicos e inter-harmÃnicos no sistema, bem como a modelagem matemÃtica dos dois algoritmos com elevada rejeiÃÃo a estes distÃrbios. SÃo apresentados os resultados de simulaÃÃo e experimentais dos algoritmos propostos e a comparaÃÃo entre estes mÃtodos de sincronizaÃÃo com determinados mÃtodos presentes na literatura. Como resultado do estudo, pode-se observar que as estruturas de sincronizaÃÃo propostas apresentam um tempo de resposta mais elevado, porÃm o erro do sinal estimado em relaÃÃo a componente fundamental do sinal de entrada à inferior quando comparado a estruturas como o EPLL e estruturas baseadas no SOGI. Com isso, tem-se que as mesmas estÃo habilitadas para estimar o Ãngulo de sincronismo, a frequÃncia e a componente fundamental do sinal de entrada adequadamente e podem serem utilizadas eficientemente em estratÃgias de controle de conversores de potÃncia.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-02-11T12:44:23Z No. of bitstreams: 1 henriqueluismoreiramonteiro.pdf: 1229121 bytes, checksum: 42eac85a6ba4045f928f5e191a450601 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-02-26T11:59:22Z (GMT) No. of bitstreams: 1 henriqueluismoreiramonteiro.pdf: 1229121 bytes, checksum: 42eac85a6ba4045f928f5e191a450601 (MD5) / Made available in DSpace on 2016-02-26T11:59:22Z (GMT). No. of bitstreams: 1 henriqueluismoreiramonteiro.pdf: 1229121 bytes, checksum: 42eac85a6ba4045f928f5e191a450601 (MD5) Previous issue date: 2014-02-17 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O cálculo de componentes harmônicos e inter-harmônicos é efetuado geralmente através do cálculo da FFT (Fast Fourier Transform). Porém, com a utilização desta ferramenta, alguns problemas podem ser ocasionados de modo que a energia do sinal original se espalhe ao longo do espectro de frequência. Isto proporciona o surgimento de componentes que na realidade não existem. Este fenômeno é definido como espalhamento espectral e acontece pelo fato de haver algum componente interharmônico fora da resolução da frequência da FFT ou pelo fato do sinal ser amostrado de forma assíncrona. Para o primeiro caso, utiliza-se a norma IEC 61000-4-7 que apresenta uma abordagem de grupos e subgrupos a fim de englobar a energia dos interharmônicos espalhada ao longo do espectro de frequência. Quanto ao sinal amostrado de forma assíncrona, são apresentados métodos de interpolação no domínio da frequência e no domínio do tempo para corrigir o resultado obtido através da FFT. Dessa forma, este trabalho faz uma abordagem da norma IEC e de cada método de interpolação, comparando-os com intuito de se conhecer o melhor método a ser aplicado para o cálculo dos componentes contidos no sinal, de acordo com a norma IEC 61000-4-7. / The harmonic and interharmonic components calculation is usually performance by using the FFT ( Fast Fourier Transform). However, through the use of this tool, some problems may arise due the fact that the original signal energy can spread over the frequency spectrum, promoting the appearance of not actually existing components. This phenomenon is defined as spectral leakage and happens because either there is some interharmonic component whose frequency does not match the frequency resolution of the FFT, or because the signal is sampled asynchronously. In the first case, IEC 61000-4-7 provides the groups and subgroups approaches to include the interharmonic energy spreads over the frequency spectrum. In the case of asynchronous sampled rate, interpolation methods are presented both in the frequency domain and in time domain for correcting the result obtained through the FFT. Thus, this work addresses IEC approach and presents how the time and frequency interpolation can be used to improve the IEC criteria. The interpolation methods are compared in order to find the best method to be applied for the calculation of the components contained in the signal, in accordance with IEC 61000-4-7.