Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (December 19, 2006) Includes bibliographical references.

[Truncated abstract] This thesis studies current sensing techniques that are designed to meet the requirements for the next generation of power converters. Power converters are often standardised, so that they can be replaced with a model from another manufacturer without an expensive system redesign. For this reason, the power converter market is highly competitive and relies on cutting-edge technology, which increases power conversion efficiency and power density. High power density and conversion efficiency reduce the system cost, and thus make the power converter more attractive to the customer. Current sensing is a vital task in power converters, where the current information is required for monitoring and control purposes. In order to achieve the above-mentioned goals, existing current sensing techniques have to be improved in terms of cost, power loss and size. Simultaneously, current information needs to be increasingly available in digital form to enable digital control, and to allow the digital transmission of the current information to a centralised monitoring and control unit. All this requires the output signal of a particular current sensing technique to be acquired by an analogue-to-digital converter, and thus the output voltage of the current sensor has to be sufficiently large. This thesis thoroughly reviews contemporary current sensing techniques and identifies suitable techniques that have the potential to meet the performance requirements of the next-generation of power converters. After the review chapter, three novel current sensing techniques are proposed and investigated: 1) The usefulness of the resistive voltage drop across a copper trace, which carries the current to be measured, to detect electrical current is evaluated. Simulations and experiments confirm that this inherently lossless technique can measure high currents at reasonable measurement bandwidth, good accuracy and low cost if the sense wires are connected properly. 2) Based on the mutual inductance theory found during the investigation of the copper trace current sense method, a modification of the well-known lossless inductor current sense method is proposed and analysed. This modification involves the use of a coupled sense winding that significantly improves the frequency response. Hence, it becomes possible to accurately monitor the output current of a power converter with the benefits of being lossless, exhibiting good sensitivity and having small size. 3) A transformer based DC current sense method is developed especially for digitally controlled power converters. This method provides high accuracy, large bandwidth, electrical isolation and very low thermal drift. Overall, it achieves better performance than many contemporary available Hall Effect sensors. At the same time, the cost of this current sensor is significantly lower than that of Hall Effect current sensors. A patent application has been submitted. .... The current sensing techniques have been studied by theory, hardware experiments and simulations. In addition, the suitability of the detection techniques for mass production has been considered in order to access the ability to provide systems at low-cost.

I address the geometric problem of the pendulum-like swinging of towed birds for AEM platforms. I establish a link between actual observed bird swing and its effect on survey data for two different systems and explain the link by a model that compares actual survey data to the calculated mutual inductance coupling of a dipole pair over an infinitely conductive half space, which pair is permitted arbitrary pitch, roll and altitude changes. I develop a non-linear filter that removes bird swing effects from survey data which successfully corrected data from 3 different AEM surveys. Calibration of several different time domain AEM systems is attempted using an accurately laid out and surveyed, closed, multi-turn loop of known resistance and self-inductance that is placed on - but insulated from - resistive ground. I derive a rigourous mathematical model that predicts airborne receiver's response to the coupling to the transmitter current waveform and total system geometry. The method was proven to be successful over resistive ground, with significant system problems identified such as: altimetry error, spatial averaging of data during postprocessing, error in the predicted horizontal position of the AEM platform, receiver windowing and timing errors and bird swing. I show that, although we can calibrate a time domain AEM system for a single flyover, it is impossible to calibrate an AEM system for geometry. As an intermediate step in the calibration process, I show that by monitoring the current induced in the ground loop we can obtain the waveform of the AEM transmitter current throu gh deconvolution in the Fourier domain. Simple and cost effective methods for the improvement of quantitative AEM data are presented in this thesis. However, until the geometry problem of AEM platforms is solved, full system calibration will not be obtained and filters will need to be applied to the data. I recommend the use of: GPS antennas mounted on all towed birds, able to be post-processed for accurate position recovery, reliable bird-mounted scanning altimeters that do not rely on range-finding technology but instead employ a shortest path algorithm, pitch and roll sensors mounted on the trailed bird and the measurement of airspeed of both the towed bird and the aircraft during surveys.

abstract: This thesis addresses the design and control of three phase inverters. Such inverters are used to produce three-phase sinusoidal voltages and currents from a DC source. They are critical for injecting power from renewable energy sources into the grid. This is especially true since many of these sources of energy are DC sources (e.g. solar photovoltaic) or need to be stored in DC batteries because they are intermittent (e.g. wind and solar). Two classes of inverters are examined in this thesis. A control-centric design procedure is presented for each class. The first class of inverters is simple in that they consist of three decoupled subsystems. Such inverters are characterized by no mutual inductance between the three phases. As such, no multivariable coupling is present and decentralized single-input single-output (SISO) control theory suffices to generate acceptable control designs. For this class of inverters several families of controllers are addressed in order to examine command following as well as input disturbance and noise attenuation specifications. The goal here is to illuminate fundamental tradeoffs. Such tradeoffs include an improvement in the in-band command following and output disturbance attenuation versus a deterioration in out-of-band noise attenuation. A fundamental deficiency associated with such inverters is their large size. This can be remedied by designing a smaller core. This naturally leads to the second class of inverters considered in this work. These inverters are characterized by significant mutual inductances and multivariable coupling. As such, SISO control theory is generally not adequate and multiple-input multiple-output (MIMO) theory becomes essential for controlling these inverters. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2015

No description available.

A novel torque control algorithm, which adopts a two-phase excitation, is proposed to improve the performance of the Switched Reluctance Motor (SRM) drive. By exciting two adjacent phases instead of single phase, the changing rate and the magnitude of the phase currents are much reduced. Therefore the existing problems caused by the single-phase excitation such as large torque ripple during commutation, increased audible noise and fatigue of the rotor shaft are mitigated. The electromagnetic torque is efficiently distributed to each phase by the proposed Torque Distribution Function (TDF) that also compensates the effects of mutual coupling. To describe the effects of mutual coupling between phases, a set of voltage and torque equations is newly derived for the two-phase excitation. Parameters of the SRM are obtained by Finite Element Analysis (FEA) and verified by measurements. It is shown that the mutual inductance of two adjacent phases partly contributes to generate the electromagnetic torque and introduces coupling between two adjacent phases in the current or flux linkage control loop, which has been neglected in the single-phase excitation. The dynamics of the current or flux linkage loop are coupled and nonlinear due to the mutual inductance between two adjacent phases and the time varying nature of inductance. Each phase current or flux linkage needs to be controlled precisely to achieve the required performance. A feedback linearizing current controller is proposed to linearize and decouple current control loop along with a gain scheduling scheme to maintain performance of the current control loop regardless of rotor position as well as a feedback linearizing flux linkage controller. Finally, to reduce current or flux linkage ripple, a unipolar switching strategy is proposed. The unipolar switching strategy effectively doubles the switching frequency without increasing the actual switching frequency of the switches. This contributes to the mitigation of current or flux linkage ripple and hence to the reduction of the torque ripple. / Ph. D.

Šiandien neįsivaizduojame savo gyvenimo be daugybės elektrą naudojančių prietaisų, kurie su elektros šaltiniu sujungti elektros laidais. Daugybė besipainiojančių laidų tikrai nepadaro mūsų gyvenimo lengvesnio ir patogesnio. Dar labiau komplikuoja situacijas, kai neįmanoma panaudoti laidų ir prisijungti prie energijos šaltinio. Visi šie nepatogumai skatina ieškoti išeities, kuri galėtų būti energijos perdavimas be laidų. Bevielės elektros idėja buvo iškelta jau prieš daugiau kaip šimtą metų, tai buvo išradėjo Nikola Tesla mintis. Darbui nagrinėti pagamintas bevielės energijos perdavimo demonstracinis modelis. Modelyje nagrinėjama bevielės energijos perdavimo sistema, veikimo principas, siunčiamos energijos nuotolis, perduodamos energijos efektyvumas bei gaunami nuostoliai. / Today can not imagine our life without many electricity using devices are connected to a source of electrical power lines. Numerous trailing wires really does not make our lives easier and more comfortable. Even more complicated situations when there are no opportunities to use wire and to connect to a power source. All these inconveniences are promoting to search the solution wich could be the transfer of energy without wires. Wireless energy idea has been raised for more than a hundred years ago. The thought was inventor inventored by Nikola Tesla. Analyzing this work there was made a demonstration model of wireless power transmission. In this model there is analyzing such things as wireless transmission system, working principal, transmitted energy distance and obtained losses.

Este trabalho demonstra que o efeito de extremidade existente em atuadores eletromagnéticos lineares pode ter influência significativa nas indutâncias próprias, mútuas e síncronas, com valores dependentes da posição que podem ser utilizados para monitoração da posição axial da armadura. O estudo é aplicado a um atuador eletromagnético linear tubular de ímãs permanentes com duplo arranjo de quase-Halbach e bobina móvel, que foi concebido para fins de uso em sistemas de suspensão eletromagnética ativa e semi-ativa. A partir da revisão de literatura apresentada, classificou-se o efeito de extremidade de máquinas lineares síncronas de ímãs permanentes quanto aos tipos, causas, consequências e técnicas de mitigação (caso seja necessário). Adicionalmente, os tipos de controle sem sensores são exemplificados a fim de se identificar maneiras possíveis de adequar algum ao atuador em estudo. São apresentados casos de trabalhos na literatura que utilizam o controle sem sensores em máquinas que possuem indutâncias com comportamento semelhante. Em termos de análise, a distribuição do fluxo magnético no atuador é estudada e um modelo semianalítico é elaborado para calcular o valor das indutâncias com base nos dados de fluxo magnético obtido por simulação numérica. Logo, modelos numéricos completos e parametrizados do atuador são elaborados para simulação transiente e magnetostática e a partir destes as indutâncias são obtidas. As indutâncias também são medidas experimentalmente e na análise dos resultados as incertezas de medição são calculadas e um projeto de experimento é apresentado. Os resultados dos modelos semianalítico e numérico apresentam boa concordância com os resultados experimentais. Por fim, a adequação do atuador para futura aplicação de controle sem sensores é discutida tendo como base a variação de indutâncias devido ao efeito de extremida. / This work demonstrates that the end effect in linear electromagnetic actuators can have a significant influence on the self-, mutual and synchronous inductances, with positiondependent values that can be used to measure the axial position of the armature. The study is applied to a linear synchronous electromagnetic actuator with two arrangements of quasi- Halbach permanent magnets and moving coil, which was designed for use in active and semiactive electromagnetic suspension systems. Based on the literature review presented, the end effect of permanent magnet synchronous linear machines was classified with regard to: types, causes, consequences and mitigation techniques (if necessary). In addition, the types of sensorless control methods are exemplified in order to identify a possible method to be applied to the actuator under study. It was found in the literature that sensorless control was applied to machines that have inductances with similar behavior. In terms of analysis, the distribution of the magnetic flux in the actuator is studied and a semi-analytical model was developed to calculate the value of the inductances based on the data of magnetic flux obtained through numerical simulation. Thus, the complete parametrized numerical models of the actuator were built for transient and magnetostatic simulation, and from these the inductances were obtained. The inductances are also measured experimentally, and in the analysis of the results the measurement uncertainties are calculated and a design of experiments is presented. The results of the semi-analytical and numerical models show good agreement with the experimental results. Finally, the suitability of the actuator for future application of sensorless control is discussed based on the variation of inductances due to the end effect.

After nearly a decade of development, human-implantable sensors for detection of muscle activity have recently been demonstrated in the literature. The implantable sensors are powered and communicate wirelessly through the skin using coupled inductor coils. The focus of the present work has been the development of a new approach to modeling the inductively coupled link by using the finite element method (FEM) to simulate a three-dimensional representation of the coils and surrounding magnetic field. The validity of the simulation is tested by comparison to analytically-developed formulas for self-inductance, ac resistance and mutual inductance of the coils. Determination of these parameters is necessary for calculation of the coupling coefficient between the coils, and to fully define the lumped circuit model of the link. This 3D FEM approach is novel and attractive because it is able to encompass physical geometric parameters and material properties that have been traditionally been a challenge to determine. In particular the contribution of a ferrite-core, and the case of non-symmetrical relative coil positioning can be evaluated. / Graduate

Este trabalho demonstra que o efeito de extremidade existente em atuadores eletromagnéticos lineares pode ter influência significativa nas indutâncias próprias, mútuas e síncronas, com valores dependentes da posição que podem ser utilizados para monitoração da posição axial da armadura. O estudo é aplicado a um atuador eletromagnético linear tubular de ímãs permanentes com duplo arranjo de quase-Halbach e bobina móvel, que foi concebido para fins de uso em sistemas de suspensão eletromagnética ativa e semi-ativa. A partir da revisão de literatura apresentada, classificou-se o efeito de extremidade de máquinas lineares síncronas de ímãs permanentes quanto aos tipos, causas, consequências e técnicas de mitigação (caso seja necessário). Adicionalmente, os tipos de controle sem sensores são exemplificados a fim de se identificar maneiras possíveis de adequar algum ao atuador em estudo. São apresentados casos de trabalhos na literatura que utilizam o controle sem sensores em máquinas que possuem indutâncias com comportamento semelhante. Em termos de análise, a distribuição do fluxo magnético no atuador é estudada e um modelo semianalítico é elaborado para calcular o valor das indutâncias com base nos dados de fluxo magnético obtido por simulação numérica. Logo, modelos numéricos completos e parametrizados do atuador são elaborados para simulação transiente e magnetostática e a partir destes as indutâncias são obtidas. As indutâncias também são medidas experimentalmente e na análise dos resultados as incertezas de medição são calculadas e um projeto de experimento é apresentado. Os resultados dos modelos semianalítico e numérico apresentam boa concordância com os resultados experimentais. Por fim, a adequação do atuador para futura aplicação de controle sem sensores é discutida tendo como base a variação de indutâncias devido ao efeito de extremida. / This work demonstrates that the end effect in linear electromagnetic actuators can have a significant influence on the self-, mutual and synchronous inductances, with positiondependent values that can be used to measure the axial position of the armature. The study is applied to a linear synchronous electromagnetic actuator with two arrangements of quasi- Halbach permanent magnets and moving coil, which was designed for use in active and semiactive electromagnetic suspension systems. Based on the literature review presented, the end effect of permanent magnet synchronous linear machines was classified with regard to: types, causes, consequences and mitigation techniques (if necessary). In addition, the types of sensorless control methods are exemplified in order to identify a possible method to be applied to the actuator under study. It was found in the literature that sensorless control was applied to machines that have inductances with similar behavior. In terms of analysis, the distribution of the magnetic flux in the actuator is studied and a semi-analytical model was developed to calculate the value of the inductances based on the data of magnetic flux obtained through numerical simulation. Thus, the complete parametrized numerical models of the actuator were built for transient and magnetostatic simulation, and from these the inductances were obtained. The inductances are also measured experimentally, and in the analysis of the results the measurement uncertainties are calculated and a design of experiments is presented. The results of the semi-analytical and numerical models show good agreement with the experimental results. Finally, the suitability of the actuator for future application of sensorless control is discussed based on the variation of inductances due to the end effect.