Design and Optimization of EMI Filters for Power Electronics Systems

Modern power electronics develop very rapidly. The main direction for development nowadays is increasing power density. This can be achieved by utilizing higher switching frequencies. The last generation of SiC and GaN semiconductors can reach switching frequencies up to several MHz. At the same time the number of power electronics devices connected to the power grid has grown significantly during past decades and continues to increase. These two factors result in the high level of power grid pollution with electromagnetic interferences. In order to minimize the emission level, passive electromagnetic interference (EMI) filters are employed. Within the frame of this thesis, issues related to design and improvement of EMI filters for three-phase power electronic converters are comprehensively studied. Detailed analyses of magnetic materials, filter components, mutual couplings, enhancement methods and filter topologies are presented. Insertion loss of EMI filters is analysed within a system under idealised conditions 50 Ohm reference impedance). Moreover the impact of the reference impedance used for EMI filter characterisation on insertion loss is investigated based on mathematical models. Behavioural models of EMI filters with different complexity are developed. Diverse simulation approaches are used for profound understanding of the physical processes inherent in EMI filters. Exactness of the behavioural models is proven by measurements of built prototypes. The main insertion loss degradation mechanisms are derived from the developed models. The advantages and disadvantages of models based upon the network theory, S-functions and differential equations with the help of electronic design automation tools are shown. Existing filter improvement methods are systematized and complemented. Novel improvement possibilities for conventional filters including parasitics compensation methods and mutual coupling minimization are developed. Different combinations of improvement methodologies are applied to reference EMI filters and tested. Multistage filters with enhanced topologies are proposed. Critical comparison of conventional and proposed filter topologies considering power density and costs is carried out. Obtained results demonstrate considerable advantages of enhanced EMI filter topologies over conventional ones. Three phase power electronics systems are examined from the perspective of electromagnetic compatibility. Analysis of common and differential currents' contribution into the spectrum of a conventional drive system is carried out. EMI filters are tested together with different types of power electronic converters. Effects caused by variation of converter parameters on the emitted spectrum of disturbances are assessed from the EMI filter design point if view. It is determined that essentially all investigated parameters of a power electronics converter and a drive system except DC voltage fluctuation have feasible impact on the EMI spectrum. Thus EMC behaviour of the system can be adjusted by variation of these parameters. Semiconductor speed, motor stray capacitance and concept of protective earthing are determined as the most relevant system parameters influencing EMI filter design

Modeling and Optimization Algorithm for SiC-based Three-phase Motor Drive System

More electric aircraft (MEA) and electrified aircraft propulsion (EAP) becomes the important topics in the area of transportation electrifications, expecting remarkable environmental and economic benefits. However, they bring the urgent challenges for the power electronics design since the new power architecture in the electrified aircraft requires many benchmark designs and comparisons. Also, a large number of power electronics converter designs with different specifications and system-level configurations need to be conducted in MEA and EAP, which demands huge design efforts and costs. Moreover, the long debugging and testing process increases the time to market because of gaps between the paper design and implementation. To address these issues, this dissertation covers the modeling and optimization algorithms for SiC-based three-phase motor drive systems in aviation applications. The improved models can help reduce the gaps between the paper design and implementation, and the implemented optimization algorithms can reduce the required execution time of the design program. The models related to magnetic core based inductors, geometry layouts, switching behaviors, device loss, and cooling design have been explored and improved, and several modeling techniques like analytical, numerical, and curve-fitting methods are applied. With the developed models, more physics characteristics of power electronics components are incorporated, and the design accuracy can be improved. To improve the design efficiency and to reduce the design time, optimization schemes for the filter design, device selection combined with cooling design, and system-level optimization are studied and implemented. For filter design, two optimization schemes including Ap based weight prediction and particle swarm optimization are adopted to reduce searching efforts. For device selection and related cooling design, a design iteration considering practical layouts and switching speed is proposed. For system-level optimization, the design algorithm enables the evaluation of different topologies, modulation schemes, switching frequencies, filter configurations, cooling methods, and paralleled converter structure. To reduce the execution time of system-level optimization, a switching function based simulation and waveform synthesis method are adopted. Furthermore, combined with the concept of design automation, software integrated with the developed models, optimization algorithms, and simulations is developed to enable visualization of the design configurations, database management, and design results

Development of MRI radiofrequency coils to study neurophysiological changes in a neonatal animal model at 9.4T

Tese de mestrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2013A lesão cerebral hipóxico-isquémica é uma causa comum de lesão cerebral em recém-nascidos, resultando num alto risco de morte prematura ou deficiência. Estas lesões cerebrais devem-se a um fluxo insuficiente de sangue (isquémia) e a um fornecimento reduzido de oxigénio (hipóxia) ao cérebro, eventos que provocam lesões cerebrais agudas resultando numa série de acontecimentos que induzem lesão permanente e morte celular. O diagnóstico da lesão hipóxico-isquémica é difícil e uma detecção tardia da condição pode resultar num tratamento menos eficiente e posteriores sequelas neurológicas. A introdução da ressonância magnética como ferramenta clínica para avaliação da lesão cerebral hipóxico-isquémica neonatal permitiu a determinação da localização, extensão e evolução das lesões cerebrais hipóxico-isquémicas, sendo a mais sensível e específica das técnicas de imagem. Diversas modalidades de ressonância magnética têm vindo a ser exploradas para avaliar lesões cerebrais hipóxico-isquémicas neonatais para avaliação de mudanças neurofisiológicas entre estas modalidades encontra-se a arterial spin labelling. Arterial spin labelling (ASL) é uma técnica de ressonância magnética que mede a perfusão cerebral (fornecimento de sangue a um tecido capilar) de forma não invasiva. Nesta técnica o sangue arterial, que flui nas artérias que levam o sangue a uma zona que se pretende estudar a função, é utilizado como marcador endógeno. Utilizando um pulso de radiofrequência os protões das moléculas de água presentes no sangue arterial são marcados ficando o seu spin invertido. Através da subtracção de uma imagem da área em estudo com o spin arterial invertido e outra imagem com spin no estado não invertido é possível obter uma medição do fluxo cerebral. Para executar esta técnica uma bobina de ressonância de transmissão tem de ser utilizada para proceder à inversão dos spins, esta bobina pode ser a mesma com a qual se adquirem as imagens ou pode ser separada o que apresenta melhores resultados. Outra técnica que tem sido explorada para fornecer informações metabólica em lesões cerebrais hipóxico-isquémicas é a ressonância magnética de sódio (23Na). Esta técnica permite avaliar a viabilidade de um tecido, observando as concentrações de 23Na no tecido que se alteram quando um evento de hipóxico-isquémico ocorre. Apesar de ser uma técnica promissora as imagens de ressonância magnética de 23Na apresentam menor relação sinal ruído e menor resolução. O desenvolvimento de novas técnicas de imagem beneficia dos avanços em várias áreas de ressonância magnética. A utilização de campos magnéticos mais elevados tem provado ser uma forma de melhorar as medições de quantificação, proporcionando uma maior sensibilidade e relação sinal ruído. Por outro lado a utilização de bobinas de radiofrequência especialmente desenvolvidas para cada técnica é também um meio utilizado para melhorar o desempenho de determinadas técnicas. As bobinas podem ser especialmente desenhadas para se adaptar a um determinado modelo em estudo ou para estarem de acordo com um determinado protocolo experimental. O objectivo do trabalho descrito nesta dissertação é projectar e construir bobinas de radiofrequência (RF) que se destinam à utilização num sistema pré-clínico de ressonância magnética com um campo magnético de 9.4 Tesla. As bobinas desenvolvidas serão aplicadas em estudos de imagiologia neonatal utilizando um modelo animal (porco recém-nascido) com lesão hipóxico-isquémica. O principal foco do estudo principal em que o projecto descrito se insere é detectar as alterações neurofisiológicas decorrentes das hipóxico-isquémicas no cérebro utilizando diversas técnicas de ressonância magnética. Neste projecto em particular pretendem-se estudar duas dessas técnicas: arterial spin labelling e ressonância magnética de 23Na. O projecto foi dividido em dois objectivos principais. O primeiro objectivo consiste em projectar e construir uma bobina de RF de transmissão para ASL desenhada de acordo com as características do estudo experimental geral em que este projecto se insere. Pretende-se que a bobina seja posicionada na zona do pescoço do animal em estudo, o animal está deitado em pronação numa estrutura plástica cilíndrica desenhada para se encaixar numa bobina de volume que efectua a transmissão e recepção de radiofrequência que permite adquirir as imagens de protões. A bobina é posicionada entre o animal e a estrutura cilíndrica. O projecto foi desenvolvido para estar de acordo com os requisitos do procedimento acima descrito. Foi desenvolvida uma bobina de superfície sintonizada à frequência do hidrogénio a 9.4 Tesla (399.553MHz) e a impedância da bobina foi transformada de modo a corresponder à impedância dos cabos coaxiais e do sistema de ressonância magnética, neste caso 50. A bobina apresenta um método de desassociação activa entre a bobina desenvolvida e a bobina de volume. Este método consiste na colocação de um díodo PIN em série com o circuito o que permite que a bobina seja sintonizada apenas quando é necessário a transmissão de RF. A bobina é conectada a um cabo coaxial, este cabo é um circuito não balanceado que interage com a bobina levando a uma perda de sinal. Para diminuir estas possíveis perdas foram implementados dois tipos de circuitos, um junto à bobina e um circuito de um condensador em paralelo com um indutor implementado no cabo coaxial. Foi desenhada em 3D uma estrutura para proporcionar a protecção e acomodação da bobina. Para além disso foram construídos dois dispositivos que permitem a utilização da bobina. Um PIN diode driver que fornece a corrente necessária para a activação do díodo PIN e um Bias T um circuito que permite o fornecimento simultâneo de corrente continua e do pulso de radiofrequência à bobina. Todos os passos efectuados foram avaliados utilizando um analisador de redes, e os resultados foram apresentados sobre a forma de medições S11 ou S21 conforme o tipo de medição adequado. O segundo objectivo consiste em projectar e construir uma bobina de transmissão e recepção de radiofrequência para imagens de 23Na da região cerebral. Foi desenvolvida uma bobina de superfície sintonizada à frequência do 23Na a 9.4 Tesla (105.683MHz) e a impedância da bobina foi transformada de modo a corresponder a 50 . A bobina apresenta um método de sintonização remota à frequência desejada, o que permite que a sintonização da frequência e da impedância sejam realizadas fora da zona da bobina ou do magneto. A bobina apresenta um método de desassociação entre a bobina desenvolvida e a bobina de volume. Este método consiste na implementação de um circuito composto por um indutor e um condensador em paralelo com o circuito principal. Os resultados do processo descrito foram apresentados sobre a forma de medições S11 ou S21 conforme o tipo de medição adequado. Para avaliar a bobina de transmissão e recepção para 23Na foram adquiridas imagens de ressonância magnética de um fantoma e in vivo utilizando porcos recém-nascidos sujeitos a cirurgia para provocar a lesão hipóxico-isquémica. As imagens foram obtidas no sistema Varian 9.4T e os dados foram analisados usando Matlab. A bobina de superfície foi colocada dentro da bobina de volume de 1H, a ser utilizado como referência para a localização da bobina e avaliação de informações anatómicas. As imagens in vivo foram adquiridas antes de ser efectuada a lesão hipóxica-isquémica , 24 horas depois e 48 horas depois. Em ambos os caso foi possível aquisição de imagens de 23Na e detecção de diferentes estruturas. Esta tese é composta por sete capítulos. O primeiro capítulo diz respeito à introdução da tese, no segundo capítulo apresenta-se uma introdução teórica , na qual são descritos os conceitos subjacentes à teoria da técnica de ressonância magnética e ao desenvolvimento de bobinas de radiofrequência. É ainda complementada com uma breve descrição das técnicas ASL e ressonância magnética de sódio e resumo dos principais artigos publicados na área da ressonância magnética para estudo de lesões hipóxico-isquémicas neonatais. O terceiro capítulo descreve os materiais utilizados para o desenvolvimento das bobinas de radiofrequência. Nos capítulos quatro e cinco é apresentado em detalhe o desenvolvimento das bobinas e resultados das avaliação das mesmas. O sexto capítulo apresenta as imagens de sódio, as imagens incluídas são resultado de experiências realizadas com fantomas e in vivo. No último capítulo são apresentadas as conclusões e futuros aperfeiçoamentos dos projectos.Advanced magnetic resonance imaging techniques have been used as clinical tools for assessment of neurophysiology changes. Arterial spin labeling (ASL) is a magnetic resonance technique that noninvasively measures brain perfusion. There are several labeling techniques, one such technique is to use an imaging coil and a separate labeling coil. Sodium MRI provides valuable metabolic information assessing tissue viability, it has much lower SNR and resolution than proton imaging however physiological information provided has already proved to be valuable. In this project it is proposed to design and built a dedicated ASL coil and a transmit/receive sodium (23Na) radiofrequency (RF) coil to provide images of an animal model (piglet) of hypoxic ischaemic (HI) injury at a 9.4T preclinical MRI scanner. The proposed RF coils were designed and constructed. The process of development of each coil is described in detail: the tuning and matching process, the decoupling techniques chosen and the balancing methods applied. It is also presented the process of construction of other components required to allow the development or application of the coils in vivo. The evaluation of both coils and other devices constructed is presented based on the adequate bench measurements. For the transmit/receive 23Na radiofrequency coil the performance was also demonstrated performing MR imaging in a phantom and in vivo (piglet HI injury model). Sodium images of piglet's brain before HI injury, 24 and 48 hours after injury are presented

Design for Electromagnetic Compatibility--In a Nutshell

This open access book provides practicing electrical engineers and students a practical – and mathematically sound – introduction to the topic of electromagnetic compatibility (EMC). The author enables readers to understand better how to overcome commonly failed EMC tests for radiated emission, radiated immunity, and electrostatic discharge (ESD), while providing concrete EMC design guidelines. The book also presents an overview of EMC standards and regulations and how to test for a global market access

Design for Electromagnetic Compatibility--In a Nutshell

This open access book provides practicing electrical engineers and students a practical – and mathematically sound – introduction to the topic of electromagnetic compatibility (EMC). The author enables readers to understand better how to overcome commonly failed EMC tests for radiated emission, radiated immunity, and electrostatic discharge (ESD), while providing concrete EMC design guidelines. The book also presents an overview of EMC standards and regulations and how to test for a global market access

Improved transistor-controlled and commutated brushless DC motors for electric vehicle propulsion

The development, design, construction, and testing processes of two electronically (transistor) controlled and commutated permanent magnet brushless dc machine systems, for propulsion of electric vehicles are detailed. One machine system was designed and constructed using samarium cobalt for permanent magnets, which supply the rotor (field) excitation. Meanwhile, the other machine system was designed and constructed with strontium ferrite permanent magnets as the source of rotor (field) excitation. These machine systems were designed for continuous rated power output of 15 hp (11.2 kw), and a peak one minute rated power output of 35 hp (26.1 kw). Both power ratings are for a rated voltage of 115 volts dc, assuming a voltage drop in the source (battery) of about 5 volts. That is, an internal source voltage of 120 volts dc. Machine-power conditioner system computer-aided simulations were used extensively in the design process. These simulations relied heavily on the magnetic field analysis in these machines using the method of finite elements, as well as methods of modeling of the machine power conditioner system dynamic interaction. These simulation processes are detailed. Testing revealed that typical machine system efficiencies at 15 hp (11.2 kw) were about 88% and 84% for the samarium cobalt and strontium ferrite based machine systems, respectively. Both systems met the peak one minute rating of 35 hp

RIFEL - Ripple and Electromagnetic Fields in Electric Vehicles

The electrical system in an electrified vehicle consists of high voltage (HV) components interacting in a complex way. The switching interaction in the power electronics results in ripple causing electromagnetic fields, disturbing other electronics and degradation of components. An overview of this can first be obtained when a physical system is built which could lead to unintentional over- or under dimensioning of HV components. This lack of information within the electrical system can lead to late verifications in the project causing substantial cost if changes are needed. This project aims at improving early evaluation of new concepts, create tools and build the necessary competence for a virtual system model that includes the key HV components: battery, electrical motor and power electronics, a simple load along with cable and connectors. This virtual model shall be able to simulate voltage and current ripple generated by the power electronics, initially in a frequency range up to 100 kHz. Results from the simulations shall be presented both in time and frequency domain as well as be expressed in RMS values for easier comparison to measured results. Some of the more important findings are briefly summarised below;For the high voltage battery, the electrical characteristics up to a frequency of roughly 1000 Hz was well determined using an impedance spectroscopy instrument at cell level and then multiplied by the numbers of cells.\ua0 However for finding the impedance behaviour for frequencies above 1000 Hz, the determination must be done on the battery pack level since bus bars and other component in the complete battery pack will be dominating in this frequency range. From measurements of differential mode impedance in high voltage cables it is found that it is important that the mutual inductance between the centre conductor and shield is included in the model to describe cable impedance below 10 kHz properly.The control of the inverter is very important for the overall behaviour and in this project SVM was used which has been shown to give the lowest current and voltage ripple of the traditional switching schemes. And for the machine model, the temperature variations must be taken into account since the machine parameters has been found to vary with ~20 % over the specified temperature range.The system model is found to agree well with rig measurements well up to 1 MHz with regards to both currents and voltages at the DC and AC sides. Furthermore, measurements in a real car match those in the rig. For time domain simulations, it was decided to use Ansys Simplorer since it can handle the inverter and the electrical machine simulations very well and for frequency domain simulations, it was decided to use LTspice since it is freeware, has support for AC-sweeps, improved switching compared to other SPICE-simulators, and is easy to use.Magnetic field simulations have been calculated and compared to measurements in the driveline rig at Chalmers. It was a good match across the investigated frequency range 10 Hz to 100 kHz.In this project, only internally developed component models were considered. To expand the functionality of the system modelling tool, international interface standards such as the Functional Mockup Interface (FMI) need to be investigated. Consequently, it would be a good idea to include additional automotive OEMs as well as suppliers and software vendors in future research collaborations

Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics

Electromagnetic Interference and Compatibility

Recent progress in the fields of Electrical and Electronic Engineering has created new application scenarios and new Electromagnetic Compatibility (EMC) challenges, along with novel tools and methodologies to address them. This volume, which collects the contributions published in the “Electromagnetic Interference and Compatibility” Special Issue of MDPI Electronics, provides a vivid picture of current research trends and new developments in the rapidly evolving, broad area of EMC, including contributions on EMC issues in digital communications, power electronics, and analog integrated circuits and sensors, along with signal and power integrity and electromagnetic interference (EMI) suppression properties of materials