Induction heating converter's design, control and modeling applied to continuous wire heating

Induction heating is a heating method for electrically conductive materials that takes advantage of the heat generated by the Eddy currents originated by means of a varying magnetic field. Since Michael Faraday discovered electromagnetic induction in 1831, this phenomena has been widely studied in many applications like transformers, motors or generators' design. At the turn of the 20th century, induction started to be studied as a heating method, leading to the construction of the first industrial induction melting equipment by the Electric Furnace Company in 1927. At first, the varying magnetic fields were obtained with spark-gap generators, vacuum-tube generators and low frequency motor-generator sets. With the emergence of reliable semiconductors in the late 1960's, motor-generators were replaced by solid-state converters for low frequency applications. With regard to the characterization of the inductor-workpiece system, the first models used to understand the load's behavior were based on analytical methods. These methods were useful to analyze the overall behavior of the load, but they were not accurate enough for a precise analysis and were limited to simple geometries. With the emergence of computers, numerical methods experienced a tremendous growth in the 1990's and started to be applied in the induction heating field. Nowadays, the development of commercial softwares that allow this type of analysis have started to make the use of numerical methods popular among research centers and enterprises. This type of softwares allow a great variety of complex analysis with high precision, consequently diminishing the trial and error process. The research realized in last decades, the increase in the utilization of numerical modeling and the appearance and improvement of semiconductor devices, with their corresponding cost reduction, have caused the spread of induction heating in many fields. Induction heating equipments can be found in many applications, since domestic cookers to high-power aluminum melting furnaces or automotive sealing equipments, and are becoming more and more popular thanks to their easy control, quick heating and the energy savings obtained. The present thesis focuses on the application of induction heating to wire heating. The wire heating is a continuous heating method in which the wire is continuously feeding the heating inductor. This heating method allows high production rates with reduced space requirements and is usually found in medium to high power industrial processes working 24 hours per day. The first chapters of this study introduce the induction heating phenomena, its modeling and the converters and tanks used. Afterwards, a multichannel converter for high-power and high-frequency applications is designed and implemented with the aim of providing modularity to the converter and reduce the designing time, the production cost and its maintenance. Moreover, this type of structure provides reliability to the system and enables low repairing times, which is an extremely interesting feature for 24 hours processes. Additionally, a software phase-locked loop for induction heating applications is designed and implemented to prove its flexibility and reliability. This type of control allows the use of the same hardware for different applications, which is attractive for the case of industrial applications. This phase-locked loop is afterwards used to design and implement a load-adaptative control that varies the references to have soft-switching according to load's variation, improving converter's performance. Finally, the modeling of a continuous induction wire hardening system is realized, solving the difficulty of considering the mutual influence between the thermal, electromagnetic and electric parameters. In this thesis, a continuous process is modeled and tested using numerical methods and considering converter's operation and influence in the process.Postprint (published version

Power quality improvement using passive shunt filter, TCR and TSC combination

Power system harmonics are a menace to electric power systems with disastrous consequences. The line current harmonics cause increase in losses, instability, and also voltage distortion. With the proliferation of the power electronics converters and increased use of magnetic, power lines have become highly polluted. Both passive and active filters have been used near harmonic producing loads or at the point of common coupling to block current harmonics. Shunt filters still dominate the harmonic compensation at medium/high voltage level, whereas active filters have been proclaimed for low/medium voltage ratings. With diverse applications involving reactive power together with harmonic compensation, passive filters are found suitable [41]. Passive filtering has been preferred for harmonic compensation in distribution systems due to low cost, simplicity, reliability, and control less operation [42]. The uncontrolled ac-dc converter suffers from operating problems of poor power factor, injection of harmonics into the ac mains, variations in dc link voltage of input ac supply, equipment overheating due to harmonic current absorption, voltage distortion due to the voltage drop caused by harmonic currents flowing through system impedances, interference on telephone and communication line etc. The circuit topologies such as passive filters, ac-dc converter, based improved power quality ac-dc converters are designed, modeled and implemented. The main emphasis of this investigation has been on a compactness of configurations, simplicity in control, reduction in rating of components, thus finally leading to saving in overall cost. Based on thesis considerations, a wide range of configurations of power quality mitigators are developed, which is expected to provide detailed exposure to design engineers to choose a particular configuration for a specific application under the given constraints of economy and desired performance. For bidirectional power flow applications, the current source converter is designed and simulated with R-L load. The necessary modeling and simulations are carried out in MATLAB environment using SIMULINK and power system block set toolboxes. The behavior of different configurations of passive tuned filters on power quality is studied. One of the way out to resolve the issue of reactive power would be using filters and TCR, TSC with combination in the power system. Installing a filter for nonlinear loads connected in power system would help in reducing the harmonic effect. The filters are widely used for reduction of harmonics. With the increase of nonlinear loads in the power system, more and more filters are required. The combinations of passive filters with TCR and TSC are also designed and analyzed to improve the power quality at ac mains. This scheme has resulted in improved power quality with overall reduced rating of passive components used in front end ac-dc converters with R-L load

Neural Networks based Shunt Hybrid Active Power Filter for Harmonic Elimination

The growing use of nonlinear devices is introducing harmonics in the power system networks that results in distortion of current and voltage signals causing damage to the power distribution system. Therefore, in power systems, the elimination of harmonics is of great concern. This paper presents an efficient techno-economical approach to suppress harmonics and improve the power factor in the power distribution network using neural network algorithms-based Shunt Hybrid Active Power Filter (SHAPF), such as Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), and Recurrent Neural Network (RNN). The objective of the proposed algorithms for SHAPF is to reduce Total Harmonic Distortion (THD) within an acceptable range to improve system quality. In our filter design approach, we tested and compared conventional pq0 theory and neural networks to detect the harmonics present in the power system. Moreover, for the regulation of the DC supply to the inverter of the SHAPF, the conventional PI controller and neural networks-based controllers are used and compared. The applicability of the proposed filter is tested for three different nonlinear load cases. The simulation results show that the neural networks-based filter control techniques satisfy all international standards with minimum current THD, neutral wire current elimination, and small DC voltage fluctuations for voltage regulation current. Furthermore, all three neural network architectures are tested and compared based on accuracy and computational complexity, with RNN outperforming the rest

Assessment of novel power electronic converters for drives applications

Phd ThesisIn the last twenty years, industrial and academic research has produced over one hundred new converter topologies for drives applications. Regrettably, most of the published work has been directed towards a single topology, giving an overall impression of a large number of unconnected, competing techniques. To provide insight into this wide ranging subject area, an overview of converter topologies is presented. Each topology is classified according to its mode of operation and a family tree is derived encompassing all converter types. Selected converters in each class are analysed, simulated and key operational characteristics identified. Issues associated with the practical implementation of analysed topologies are discussed in detail. Of all AC-AC conversion techniques, it is concluded that softswitching converter topologies offer the most attractive alternative to the standard hard switched converter in the power range up to 100kW because of their high performance to cost ratio. Of the softswitching converters, resonant dc-link topologies are shown to produce the poorest output performance although they offer the cheapest solution. Auxiliary pole commutated inverters, on the other hand, can achieve levels of performance approaching those of the hard switched topology while retaining the benefits of softswitching. It is concluded that the auxiliary commutated resonant pole inverter (ACPI) topology offers the greatest potential for exploitation in spite of its relatively high capital cost. Experimental results are presented for a 20kW hard switched inverter and an equivalent 20kW ACPI. In each case the converter controller is implanted using a digital signal processor. For the ACPI, a new control scheme, which eliminates the need for switch current and voltage sensors, is implemented. Results show that the ACPI produces lower overall losses when compared to its hardswitching counterpart. In addition, device voltage stress, output dv/dt and levels of high frequency output harmonics are all reduced. Finally, it is concluded that modularisation of the active devices, optimisation of semiconductor design and a reduction in the number of additional sensors through the use of novel control methods, such as those presented, will all play a part in the realisation of an economically viable system.Research Committee of the University of Newcastle upon Tyn

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Controlling the multipolar interference of nanoantennas

The emission and detection of light is a main pillar of both fundamental research and the advancement of modern technologies. From digital communications and quantum computing to novel cancer treatments and faded jeans, light-matter interactions are at the core of each of these things, and the fundamental building block of nearly every one of these interactions is the electric dipole. The emission and absorption from every molecule, atom, quantum dot and semiconductor is predominantly electric dipole by nature. While it is the most efficient, fastest, brightest, and easiest to understand process, it is not the only process by which light can be emitted and absorbed; magnetic dipoles, electric quadrupoles, and more, all exist in nature. Optical nanoantennas are the basic element for efficient interfacing between photons and single photon emitters, as they address the inherent size mismatch between the physical size of the emitters and the much larger wavelength of light with which they interact. Optical nanoantennas are also generally electric dipole in nature, as their fundamental resonance is that of an oscillating positive and negative charge. However, unlike nature, these antennas can be engineered to promote higher order modes so that non-electric dipole resonances are not the only contributor. The topic of this Thesis is the control of light emission through modes beyond the electric dipole, both from single emitters coupled to optical nanoantennas and from the emission of light directly from the antennas themselves. In the Introduction, we provide an overview of basic antenna theory, and in Chapter 1, we describe the experimental and theoretical methods used throughout this Thesis. In Chapter 2, we direct light emission from a quantum dot coupled to a two-dimensional antenna excited at a higher-order mode, and represent its emission pattern with a multipole expansion. To demonstrate the importance of a characteristic of light unavailable to spontaneous emission, its phase, we measure the angular emission patterns of second harmonic generation directly from single nanoantennas in Chapter 3, and once more model its patterns with the multipole model. In Chapter 4, we delve into the second harmonic generation from a crystalline semiconductor, and detect competing second order nonlinear processes that were not present in the previous chapter. Finally, in Chapter 5 we combine the previous three chapters and design an optical nanoantenna, which through two nonlinear processes that coexist when driven in a higher-order mode, radiates its second harmonic unidirectionally, with a switchable emission direction. The results in this Thesis demonstrate that not only can optical nanoantennas control light emission from single emitters, but that when they are also the emitters themselves we can actively switch the direction in which light is emitted. With this change in paradigm, we now have a new lever with which to tailor the emission of light at the nanoscale. This coherent control of light emission has potential applications in any technology that benefits from higher light-matter interaction efficiencies, and particularly those that require coherenceL'emissió i detecció de la llum és un pilar principal tant de la investigació fonamental com de l'avanç de les noves tecnologies. Des de les comunicacions digitals i la computació quàntica fins als nous tractaments del càncer i els texans degradats, les interaccions llum-matèria són el nucli de cadascuna d'aquestes qüestions, i el component fonamental de gairebé totes aquestes interaccions és el dipol elèctric. L'emissió i l'absorció de totes les molècules, àtoms, punts quàntics i semiconductors és predominantment de dipol elèctric per naturalesa. Si bé és el procés més eficient, ràpid, brillant i fàcil d'entendre, no és l'únic procés pel qual la llum pot ser emesa i absorbida; dipols magnètics, quadrupols elèctrics i molts més existeixen a la natura. Les nanoantenes òptiques són l'element bàsic per a una interfície eficient entre fotons i emissors de fotons individuals, ja que s'ocupen de la disparitat inherent entre la mida física dels emissors i la major longitud d'ona amb la qual interactuen. Les nanoantenes òptiques generalment són també un dipol elèctric, ja que la seva ressonància fonamental és la d'una càrrega positiva i negativa oscil·lant. Tanmateix, a diferència de la naturalesa, aquestes antenes es poden dissenyar per promoure modes d'ordre superior, de manera que les ressonàncies dipolars no elèctriques no siguin l'únic contribuent. El tema d'aquesta tesi és el control de l'emissió de llum a través de modes que no siguin de tipus dipol elèctric, tant d’emissors individuals acoblats a nanoantenes òptiques com de l'emissió de llum directament des de les pròpies antenes. A la Introducció, oferim una descripció general de la teoria bàsica de nanoantenes, i al Capítol 1 descrivim els mètodes experimentals i teòrics utilitzats al llarg d'aquesta tesi. En el Capítol 2, dirigim l'emissió de llum a partir d'un punt quàntic acoblat a una antena bidimensional excitada a un mode d'ordre superior, i representem el seu patró d'emissió amb una expansió multipolar. Per demostrar l'importància d'una característica de la llum no disponible a l'emissió espontània, la seva fase, mesurem els patrons angulars d'emissió de la generació de segon harmònic directament des de nanoantenes individuals en el Capítol 3. En el Capítol 4, aprofundim en la generació de segon harmònic a partir d'un semiconductor cristal·lí, i detectem processos no lineals de segon ordre competidors que no estaven presents al capítol anterior. Finalment, al Capítol 5, combinem els tres capítols anteriors i dissenyem una nanoantena òptica, que a través de dos processos no lineals que coexisteixen quan s'excita en un ordre d'ordre superior, emet el seu segon harmònic de forma unidireccional, amb aquesta direcció d'emissió sent invertible. Els resultats d'aquesta Tesi demostren que no només les nanoantenes òptiques controlen l'emissió de llum d'emissors individuals, sinó que quan elles mateixes són els emissors, podem canviar activament la direcció en què s'emet la llum. Amb aquest canvi de paradigma, tenim una eina nova per controlar l'emissió de llum a la nanoescala. Aquest control coherent de l'emissió de llum té aplicacions potencials en qualsevol tecnologia que es vulgui beneficiar d'una major eficiència en la interacció de la llum-matèria, i en particular d'aquelles que requereixen coherència.Postprint (published version

On-line Junction Temperature Estimation of SiC Power MOSFETs

L'abstract è presente nell'allegato / the abstract is in the attachmen