In Geräten und Anlagen des Stromnetzes werden Steckverbinder mit hoher Stromtragfähigkeit eingesetzt, wenn bewegliche Teile kontaktiert werden oder Betriebsmittel mit geringem Aufwand montier- und demontierbar sein müssen. Die elektrische Verbindung der Leiter wird dabei oft mit federnden Kontaktelementen realisiert. Die Kontaktelemente müssen als Teil der Strombahn während der Lebensdauer des Geräts den Betriebsstrom im Kiloampere-Bereich und im Fehlerfall bis zu einige Sekunden lang den eine Größenordnung höheren Kurzschlussstrom tragen. In der vorliegenden Arbeit wurden Rechenmodelle für die innere Erwärmung von Hochstrom-Kontaktsystemen im stationären Dauerbetrieb und im transienten Kurzschlussfall entwickelt. Das elektrische und mechanische Langzeitverhalten im Temperaturbereich (105…180) °C wurde experimentell mit stromdurchflossenen, fettgeschmierten Modellsteckverbindern, die regelmäßig getrennt und neu gesteckt wurden, untersucht. Modellerstellung, Rechnungen und Versuche wurden beispielhaft mit Kontaktelementen vom Typ Multilam durchgeführt. Kontaktelemente und Leiter bestanden aus versilbertem Kupfer. Für das stationäre Betriebsverhalten wurden die mit der analytischen Spannungs-Temperatur-Beziehung nach Kohlrausch berechneten Ergebnisse mit einem Erwärmungsversuch verifiziert. Die Temperaturdifferenz zwischen Kontaktelement und Leiter ist bei Standardanwendungen, wie in Schaltanlagen, mit ≤ 3 K sehr klein. Deshalb ist die Leitertemperatur als Zielgröße beim Dimensionieren der Dauerstrombelastbarkeit ausreichend. Bei Kurzschlussstrombelastung wurde im Kontaktsystem eine schnelle, räumlich unterschiedlich ausgeprägte Erwärmung numerisch berechnet. Leiter und Kontaktelement erwärmen sich kontinuierlich, wobei die mittlere Endübertemperatur im Kontaktelement aufgrund des kleineren stromtragenden Querschnitts eine Größenordnung höher ist. Die Kontakte führen bei 50 Hz-Wechselstrom aufgrund ihrer vernachlässigbaren Wärmekapazität 100 Hz-Temperaturzyklen aus. Dabei können die Maximaltemperaturen noch deutlich größer als die mittlere Temperatur der Kontaktelemente sein. Im Langzeitversuch waren nach 16 000 h Betriebszeit bei 180 °C und regelmäßigen simulierten Steckvorgängen die Verbindungskräfte noch genügend groß, um die elektrischen Anforderungen eines neuen Kontaktsystems zu erfüllen. Allerdings führte bei einer Betriebstemperatur von 105 °C ein thermisch instabiles Schmierfett zum vorzeitigen elektrischen Ausfall eines Teils der Steckverbinder.:Einleitung Hochstrom-Kontaktsysteme – Stand der Technik Theorie der Kontakte bei hoher Strombelastung Stationäres elektrisch-thermisches Betriebsverhalten Transientes elektrisch-thermisches Betriebsverhalten Langzeitverhalten Zusammenfassung Ausblick / Switchgear and devices for the power grid use high-power connectors if moving parts have to be contacted or equipment shall be easily mountable and dismountable. The electrical connection of the conductors is often realized by spring-loaded contact elements. As part of the main circuit, contact elements must carry the full operating current in the kiloampere-range for the entire service life of the device. In case of a fault, the short-circuit current, which is one order of magnitude larger, has to be carried for up to several seconds. In this thesis, calculation models for the inner temperature rise of high-power contact systems in steady-state continuous operation, as well as for the transient short-circuit load case were developed. Electrical and mechanical long-term performance in the temperature range from 105 to 180 °C was experimentally investigated with current carrying, grease-lubricated model connectors which were regularly unplugged and replugged. Modelling, calculations and experiments were exemplarily carried out with Multilam contact elements. Conductors and contact element consisted of silver-plated copper. The analytical voltage-temperature relation was used to calculate the steady-state performance; calculations were verified with a temperature-rise test. The temperature difference from contact element to conductors is very small (≤ 3 K) for standard applications like switchgear. Thus, it is sufficient to use the conductor temperature as a criterion for the design of the continuous ampacity of high-power contact systems. At short-time load, a fast spatially inhomogeneous temperature rise was numerically calculated. Conductor and contact element continuously heat up; due to the smaller current carrying cross section, median final temperature rise in the contact element is one order of magnitude larger than in the conductors. Because of their negligible thermal capacity, contacts perform 100 Hz temperature cycles at 50 Hz AC load; the maximum contact temperatures may be significantly higher than the median temperature of the contact elements. In the long-term test, after 16 000 h operating time at 180 °C and regular plugging operations, contact elements maintained enough joint force to meet the requirements of a new contact system. At 105 °C however, a thermally instable grease led to electrical failure of part of the connectors.:Einleitung Hochstrom-Kontaktsysteme – Stand der Technik Theorie der Kontakte bei hoher Strombelastung Stationäres elektrisch-thermisches Betriebsverhalten Transientes elektrisch-thermisches Betriebsverhalten Langzeitverhalten Zusammenfassung Ausblick

[ES] En los últimos años han proliferado los nuevos sistemas de satélites, sobre todo las grandes constelaciones en las órbitas terrestres bajas. Casi todos los satélites transmiten señales digitales con diversas modulaciones y niveles de potencia. Y no sólo eso, el modelo de negocio exige un rápido despliegue de los satélites, lo que impone enormes restricciones a los proveedores de equipos de carga útil de microondas. Un área de riesgo clave para estos equipos sigue siendo la avería del multipactor bajo niveles de potencia de moderados a altos. Debido a la aleatoriedad inherente al fenómeno multipactor, los clientes tienden a añadir márgenes de diseño adicionales para los componentes de microondas de alta potencia. Esto se traduce en costes más elevados, dispositivos más voluminosos y más tiempo para las pruebas. A partir de la experiencia personal realizando ensayos de multipactor, la principal motivación del trabajo descrito en la tesis ha sido emprender una revisión exhaustiva de este fenómeno y desarrollar capacidades de ensayo multipactor de vanguardia. Proporcionar medios para la prueba rápida de multipactores bajo una variedad de señales moduladas de banda ancha. La tesis demuestra que las modulaciones analógicas y digitales tienen un impacto significativo en el umbral multipactor. También se analizan los regímenes multipactor a corto y largo plazo, regímenes que, en algunos casos, presentan umbrales multipactor muy diferentes para el mismo hueco crítico. La necesidad de reducir el peso de la carga útil de microondas convierte a la multiportadora en una excelente opción para los diseñadores. Al encaminar varias señales a través del mismo dispositivo, el peso de la carga útil se reduce drásticamente. Las soluciones comerciales para pruebas multicarrier no son adecuadas debido a los altos niveles de potencia requeridos. Se presentan varias estrategias para implementar bancos de pruebas multiportadora con parámetros controlables. Los resultados demuestran que la señal generada es precisa y estable en el tiempo. Por último, se propone un novedoso sistema de detección de multipactores para hacer frente a la detección de multipactores cuando se utilizan señales moduladas y multiportadora de cualquier ancho de banda. Este método tiene la misma sensibilidad que el conocido anulador de microondas para señales de onda continua y la supera para señales moduladas. El procesamiento digital de señales utilizado para detectar los patrones multipactor proporciona un método de detección totalmente autónomo. / [CA] En els darrers anys han proliferat els nous sistemes de satèl·lits, sobretot les grans constel·lacions a les òrbites terrestres baixes. Gairebé tots els satèl·lits transmetten dades digitals amb diverses modulacions i nivells de potència. I no només això, el model de negoci exigeix un ràpid desplegament dels satèl·lits, cosa que imposa enormes restriccions als proveïdors de càrrega útil de microones. Una àrea de risc clau per a aquests equips continua sent la descarrega de multipactor sota nivells de potència de moderats a alts. A causa de l'aleatorietat inherent al fenomen multipactor, els clients tendeixen a afegir marges de disseny addicionals per als components de microones d'alta potència. Això es tradueix en costos més elevats, dispositius més voluminosos i més temps per a les proves. A partir de l'experiència personal realitzant assajos de multipactor, la motivació principal del treball descrit a la tesi ha estat emprendre una revisió exhaustiva d'aquest fenomen i desenvolupar capacitats d'assaig multipactor d'avantguarda. Proporcionar mitjans per a la prova ràpida de multipactors sota una varietat de senyals modulats de banda ampla. La tesi demostra que les modulacions analògiques i digitals tenen un impacte significatiu al llindar multipactor. També s'analitzen els règims multipactor a curt i llarg termini, règims que, en alguns casos, presenten llindars multipactor molt diferents per al buit crític mateix. La necessitat de reduir el pes de la càrrega útil de microones fa de la transmissií multiportadora en una excel·lent opció per als dissenyadors. Encaminant diverses senyals a través del mateix dispositiu, el pes de la càrrega útil es redueix dràsticament. Les solucions comercials per a proves multicarrier no són adequades a causa dels alts nivells de potència requerits. Es presenten diverses estratègies per implementar bancs de proves multiportadora amb paràmetres controlables. Els resultats demostren que el senyal amb què s'alimenta el dispositiu sotmès a proves és precís i estable en el temps. Finalment, es proposa un nou sistema de detecció de multipactors per fer front a la detecció de multipactors quan s'utilitzen senyals modulats i multiportadors de qualsevol amplada de banda. Aquest mètode té la mateixa sensibilitat que el conegut anul·lador de microones per a senyals d'ona contínua i la supera per a senyals modulats. El processament digital de senyals utilitzat per detectar els patrons multiactor proporciona un mètode de detecció totalment autònom. / [EN] In the recent past, there has been a proliferation of new satellite systems, especially the large constellations in the Low Earth Orbits (LEOs). Nearly all satellites now carry digital traffic with a variety of modulations and power levels. Not only that, the business model requires rapid deployment of satellites, putting enormous constraints for the suppliers of microwave payload hardware. A key risk area for such equipment remains the multipactor breakdown under moderate to high power levels. Owing to the inherent randomness of the multipactor phenomenon, customers tend to add extra design margins for the high power microwave components. This results in higher costs, bulkier devices and longer time for testing. Based on personal experience in multipactor testing, the prime motivator for the work described in the thesis has been to undertake a comprehensive review of this phenomenon and develop cutting edge multipactor test capabilities, providing means for the rapid multipactor testing under a variety of wide-band modulated signals. The thesis dissertation shows that analog and digital modulations have a significant impact in the multipactor threshold. The short and long-term multipactor regimes are also analyzed, regimes that, in some cases, have very different multipactor thresholds for the same critical gap. The need to reduce the microwave payload weight by using multicarriers in a single transponder provides an excellent option for designers. By routing several signals through the same device, the payload weight is dramatically reduced. Commercial solutions for multicarrier testing are not suitable because of the high power levels required. Several strategies to implement multipactor test benches with controllable parameters are presented. Results prove that the signal being fed to the device under tests is accurate and stable over time. Finally, a novel multipactor detection system is proposed to cope with multipactor detection when modulated and multicarrier signals of any bandwidth are used. This method has the same sensitivity as the well known microwave nulling for continuous wave signals and surpasses it for modulated signals. The digital signal processing used to detect the multipactor patterns provides a full autonomous detection method. / Monerris Belda, Ó. (2023). Advanced Techniques for Multipactor Testing [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192786

<p dir="ltr">High-power microwave (HPM) devices are generally vacuum-based devices that transform electron beam energy into microwaves with peak powers above 100 MW from 1-300 GHz. Solid-state HPM devices provide more compactness and greater reliability while consuming less power. Nonlinear transmission lines (NLTLs) provide a solid-state alternative to HPM generation by sharpening the input pulses from a pulse forming network to create output oscillations.</p><p dir="ltr">The first section of this dissertation evaluates and explores the feasibility of using nonlinear composites containing ferroelectric (e.g., Ba_2/3Sr_1/3TiO₃, BST) and/or ferromagnetic (e.g., Ni_1/2Zn_1/2Fe₂O₄, NZF) inclusions in a linear polymer host (polydimethylsiloxane, PDMS) to tune NLTL properties for HPM applications. Appropriately modelling and designing NLTLs using nonlinear composites require accurately characterizing their linear and nonlinear electromagnetic properties. We first studied the electromagnetic properties of the composites using theoretical, numerical, and experimental approaches. Incorporating these composite models and characterizations into NLTL simulations will be discussed.</p><p dir="ltr">Vacuum-based HPM devices, such as magnetrons and crossed-field amplifiers, generally operate in the space-charge-limited region, which corresponds to the maximum current possible for insertion into the device. This motivated studying the space-charge-limited current and electron flow in a two-dimensional (2D) planar diode with various crossed-magnetic fields using particle-in-cell (PIC) simulations. For non-magnetically insulated diodes (electrons emitted from the cathode can reach the anode), analytical and/or semi-empirical solutions are derived for electrons with nonzero monoenergetic initial velocity that agree well with PIC simulations. For magnetically insulated conditions, we developed new metrics using simulations and analytic theories to assess electron cycloidal and Brillouin flow to understand the implications of increasing injection current for 2D diodes. These analyses provide details on the operation of these devices at high currents, particularly virtual cathode operation, that may elucidate behavior near their limits of operation.</p>

Enhancing performance of power electronics converters has always been an interesting topic in the power electronics community. Over the years, researchers and engineers are developing new high performance component, novel converter topologies, smart control methods and optimal design procedures to improve the efficiency, power density, reliability and reducing the cost. Besides pursuing high performance, researchers and engineers are striving to modularize the power electronics converters, which provides redundancy, flexibility and standardization to the end users. The trend of modularization has been seen in photovoltaic inverters, telecommunication power supplies, and recently, HVDC applications. A systematic optimal design approach for modular power converters is developed in this dissertation. The converters are developed for aerospace applications where there are stringent requirement on converter form factor, loss dissipation, thermal management and electromagnetic interference (EMI) performance. This work proposed an optimal design approach to maximize the nominal power of the power converters considering all the constraints, which fully reveals the power processing potential. Specifically, this work studied three-phase active front-end converter, three-phase isolated ac/dc converter and inverter. The key models (with special attention paid to semiconductor switching loss model), detailed design procedures and key design considerations are elaborated. With the proposed design framework, influence of key design variables, e.g. converter topology, switching frequency, etc. is thoroughly studied. Besides optimal design procedure, control issues in paralleling modular converters are discussed. A master-slave control architecture is used. The slave controllers not only follow the command broadcasted by the master controller, but also synchronize the high frequency clock to the master controller. The control architecture eliminates the communication between the slave controllers but keeps paralleled modules well synchronized, enabling a fully modularized design. Furthermore, the implementation issues of modularity are discussed. Although modularizing converters under form factor constraints adds flexibility to the system, it limits the design space by forbidding oversized components. This work studies the influence of the form factor by exploring the maximal nominal power of a double-sized converter module and comparing it with that of two paralleled modules. The tradeoff between modularity and performance is revealed by this study. Another implementation issue is related to EMI. Scaling up system capacity by paralleling converter modules induces EMI issues in both signal level and system level. This work investigates the mechanisms and provides solutions to the EMI problems. / Ph. D. / As penetration of power electronics technologies in electric power delivery keeps increasing, performance of power electronics converters becomes a key factor in energy delivery efficacy and sustainability. Enhancing performance of power electronics converters reduces footprint, energy waste and delivery cost, and ultimately, promoting a sustainable energy use. Over the years, researchers and engineers are developing new technologies, including high performance component, novel converter topologies, smart control methods and optimal design procedures to improve the efficiency, power density, reliability and reducing the cost of power electronics converters. Besides pursuing high performance, researchers and engineers are striving to modularize the power electronics converters, enabling power electronics converters to be used in a “plug-and-play” fashion. Modularization provides redundancy, flexibility and standardization to the end users. The trend of modularization has been seen in applications that process electric power from several Watts to Megawatts. This dissertation discusses the design framework for incorporating modularization into existing converter design procedure, synergically achieving performance optimization and modularity. A systematic optimal design approach for modular power converters is developed in this dissertation. The converters are developed for aerospace applications where there is stringent v requirement on converter dimensions, loss dissipation, and thermal management. Besides, to ensure stable operation of the onboard power system, filters comprising of inductors and capacitors are necessary to reduce the electromagnetic interference (EMI). Owning to the considerable weight and size of the inductors and capacitors, filter design is one of the key component in converter design. This work proposed an optimal design approach that synergically optimizes performance and promotes modularity while complying with the entire aerospace requirement. Specifically, this work studied three-phase active front-end converter, three-phase isolated ac/dc converter and three-phase inverter. The key models, detailed design procedures and key design considerations are elaborated. Experimental results validate the design framework and key models, and demonstrates cutting-edge converter performance. To enable a fully modularized design, control of modular converters, with focus on synchronizing the modular converters, is discussed. This work proposed a communication structure that minimizes communication resources and achieves seamless synchronization among multiple modular converters that operate in parallel. The communication scheme is demonstrated by experiments. Besides, the implementation issues of modularity are discussed. Although modularizing converters under form factor constraints adds flexibility to the system, it limits the design space by forbidding oversized components. This work studies the impact of modularity by comparing performance of a double-sized converter module with two paralleled modules. The tradeoff between modularity and performance is revealed by this study.

The objective of this study was to develop a new method for co-crystal preparation which adhered to green chemistry principles, and provided advantages over conventional methods. A novel, solvent-free, high-power ultrasound (US) technique, for preparing co-crystals from binary systems, was chosen as the technology which could fulfil these aims. The application of this technology for solid state co-crystal preparation was explored for ibuprofen-nicotinamide (IBU-NIC), carbamazepine-nicotinamide (CBZ-NIC) and carbamazepine-saccharin (CBZ-SAC) co-crystals. The effect of different additives and processing parameters such as power level, temperature and sonication time on co-crystallisation was investigated. Characterisation was carried out using DSC, PXRD, FTIR, Raman and HPLC. In addition, an NIR prediction model was developed and combined with multivariate analysis (PLS) and chemometric pre-treatments. It was found to be a robust, reliable and rapid method for the determination of co-crystal purity for the IBU-NIC and CBZ-NIC pairs. Co-crystal quantification of US samples helped to optimise the US method. Finally, a model formulation of paracetamol containing 5% and 10% PEG 8000 was ultrasonicated at maximum power with different exposure times. A comparison of technological and physicochemical properties of the resulting tablets with those of the tablets obtained using the pressing method evidenced significant differences. This suggested that US energy dissipation (mechanical and thermal effects) was the main mechanism which caused the PAR form I tabletability to improve. It was found that the ultrasound–compacted tablets released the drug at a slower rate compared to pure PAR. This technique was shown to be useful for improving tabletability for low-compressible drugs without the need to use a conventional tabletting machine.

[ES] Las tendencias actuales en los sistemas de comunicaciones por satélite, que implican la operación en entornos multiportadora, a frecuencias cada vez más elevadas y con mayores exigencias en términos de capacidad de transmisión, hacen necesaria la utilización de mayores niveles de potencia. El incremento de la potencia requerida, unido a la disminución del tamaño de los componentes por el aumento de la frecuencia de trabajo, y por las restricciones en términos de tamaño y peso, estimula la aparición de efectos de alta potencia. Entre estos efectos, que impactan en las prestaciones del sistema, e incluso, en algunos casos, pueden llegar a ser dañinos para los componentes, destacan el efecto multipactor, el efecto corona y la intermodulación pasiva. De entre todos estos efectos indeseados, esta tesis se ha centrado más en el efecto multipactor. Aunque este efecto rara vez llega a dañar un componente por si mismo, afecta a sus prestaciones y es la antesala del efecto corona, que sí que puede ser extremadamente perjudicial para la integridad del sistema de comunicaciones. %Es por ello por lo que el estudio de estos efectos es de especial relevancia en el campo de las comunicaciones espaciales. El efecto multipactor ha sido ampliamente estudiado para señales de envolvente constante y empleando modelos simplificados de placas paralelas. Si bien estos modelos son efectivos y permiten calcular una estimación del umbral multipactor de manera rápida, son demasiado conservadores para la situación actual de los sistemas de comunicaciones, donde las capacidades de transmisión requeridas son extremadamente altas. Debido a la complejidad que presenta estimar el umbral multipactor en los sistemas reales de forma analítica, es habitual recurrir a herramientas de simulación electromagnética combinadas con física de partículas para tratar de calcular estos umbrales. No obstante, aunque estos métodos bien configurados son bastante precisos, requieren de un elevado tiempo computacional, que puede llegar a ser de varias horas o incluso días en dispositivos complejos como filtros o multiplexores. Es por ello por lo que esta tesis doctoral ha profundizado en el estudio de métodos circuitales, que puedan hacer uso de información electromagnética. Éstos, si bien no resultan tan precisos como las simulaciones de partículas, permiten una estimación rápida del umbral que puede ser de gran ayuda para el diseñador de dispositivos que presenten requisitos de potencia. No obstante, y dada la complejidad de obtener estos umbrales de forma precisa, es habitual tener que certificar los componentes en un laboratorio previamente a su lanzamiento. En este ámbito, la presente tesis ha contribuido en dos aspectos. En primer lugar, se ha desarrollado una nueva muestra que permite caracterizar los bancos de medidas de multipactor hasta frecuencias en banda Ka. Por otro lado, se ha diseñado íntegramente un conjunto de multiplexores que se han integrado en un banco de ensayo de multipactor con diversas portadoras, dando lugar a un escenario más similar al que se puede encontrar en los sistemas de comunicaciones vía satélite actuales. Además, el diseño de estos multiplexores ha dado lugar al desarrollo de un método sistemático, que ha permitido concebir estos componentes con un alto nivel de precisión y en un tiempo bastante comedido. Por último, en cuanto al diseño de componentes pasivos de microondas operando a altas frecuencias, esta tesis doctoral ha profundizado en la familia de filtros MHFRW. Estos filtros, por sus propiedades geométricas, son apropiados para aplicaciones de alta potencia y que requieran bajos niveles de PIM. A esta topología, que viene siendo estudiada en los últimos años, se le ha aumentado su capacidad para implementar respuestas superelípticas, es decir, que incluyan más ceros de transmisión que el orden del filtro. Además, es posible conseguir situar los ceros en ubicaciones arbitrarias de manera independiente. / [CA] Les tendències actuals en els sistemes de comunicacions per satèl·lit, que impliquen l'operació en entorns multiportadora, a freqüències cada vegada més elevades i amb majors exigències en termes de capacitat de transmissió, fan necessària la utilització de majors nivells de potència. L'increment de la potència requerida, unit a la disminució de la grandària dels components per l'augment de la freqüència de treball, i per les restriccions en termes de grandària i pes, estimula l'aparició d'efectes d'alta potència. Entre aquests efectes, que impacten en les prestacions del sistema, i fins i tot, en alguns casos, poden arribar a ser nocius per als components, destaquen l'efecte multipactor, l'efecte corona i la intermodulació passiva. D'entre tots aquests efectes indesitjats, aquesta tesi s'ha centrat més en l'efecte multipactor. Encara que aquest efecte rares vegades arriba a danyar un component per si mateix, afecta a les seues prestacions i és l'avantsala de l'efecte corona, que sí que pot ser extremadament perjudicial per a la integritat del sistema de comunicacions. L'efecte multipactor ha sigut profundament estudiant per a senyals d'envolupant constant i emprant models simplificats de plaques paral·leles. Si bé aquests models són efectius i permeten calcular una estimació del llindar multipactor de manera ràpida, són massa conservadors per a la situació actual dels sistemes de comunicacions, en què les capacitats de transmissió requerides són extremadament altes. A causa de la complexitat que presenta estimar el llindar multipactor en els sistemes reals de manera analítica, és habitual recórrer a eines de simulació electromagnètica combinades amb física de partícules per a tractar de calcular aquests llindars. No obstant això, encara que aquests mètodes ben configurats són bastant precisos, requereixen d'un elevat temps computacional, que pot arribar a ser de diverses hores o fins i tot dies en dispositius complexos com a filtres o multiplexors. És per això que aquesta tesi doctoral ha aprofundit en l'estudi de mètodes circuitales, que puguen fer ús d'informació electromagnètica. Aquests, si bé no resulten tan precisos com les simulacions de partícules, permeten una estimació ràpida del llindar que pot ser de gran ajuda per al dissenyador de dispositius que presenten requisits de potència. No obstant això, i donada la complexitat d'obtindre aquests llindars de manera precisa, és habitual haver de certificar els components en un laboratori prèviament al seu llançament. En aquest àmbit, la present tesi ha contribuït en dos aspectes. En primer lloc, s'ha desenvolupat una nova mostra que permet caracteritzar els bancs de mesures de multipactor fins a freqüències en banda Ka. D'altra banda, s'ha dissenyat íntegrament un conjunt de multiplexors que s'han integrat en un banc d'assaig de multipactor amb diverses portadores, donant lloc a un escenari més similar al que es pot trobar en els sistemes de comunicacions via satèl·lit actuals. A més, el disseny d'aquests multiplexors ha donat lloc al desenvolupament d'un mètode sistemàtic, que ha permés concebre aquests components amb un alt nivell de precisió i en un temps bastant moderat. Finalment, quant al disseny de components passius de microones operant a altes freqüències, aquesta tesi doctoral ha aprofundit en la família de filtres MHFRW. Aquests filtres, per les seues propietats geomètriques, són apropiats per a aplicacions d'alta potència i que requerisquen baixos nivells de PIM. A aquesta topologia, que és estudiada en els últims anys, se li ha augmentat la seua capacitat per a implementar respostes superel·líptiques, és a dir, que incloguen més zeros de transmissió que l'ordre del filtre. A més, és possible aconseguir situar els zeros en ubicacions arbitràries de manera independent. Aquest fet aporta una gran flexibilitat al dissenyador i a més permet obtindre elevats nivells de rebuig, donant lloc a una família de filtres ideals per a diverses aplicacions. / [EN] Current trends in satellite communications systems, involving operation in multi-carrier environments at increasingly higher frequencies and with higher demands in terms of transmission capacity, make it necessary the use of higher power levels. The power increase, along with the footprint reduction due to the increase in operating frequency and the restrictions regarding component size and weight, stimulates the ignition of high-power effects. Among these effects, which impact system performance and, in some cases, can even be harmful to the components, are the multipactor effect, the corona effect and passive intermodulation. From all of these undesired effects, this thesis has focused in more extent on the multipactor effect. Although this effect in itself rarely causes physical damage to the component, it can affect to its performance and is the prelude to the corona effect, which can be extremely damaging to the integrity of the communications system. The multipactor effect has been widely studied for constant envelope signals and using simplified parallel plate models. While these models are effective and allow obtaining a fast estimate of the multipactor threshold, they are too conservative for today communications systems, where the required transmission capacities are extremely high. Due to the complexity of estimating the multipactor threshold in real systems analytically, it is common to resort to electromagnetic simulation tools combined with particle physics to try to calculate these thresholds. However, although these methods, once they are well-configured, are pretty accurate, they are also computationally time-consuming, in the order of several hours or even days for complex devices such as filters or multiplexers. This is why this doctoral thesis has focused on studying circuit methods, which can also take profit of electromagnetic information. Although these methods are not as accurate as particle simulations, they allow a quick estimation of the threshold that can significantly help the designer of microwave devices with power requirements. However, given the complexity of obtaining these thresholds accurately, it is common to have to certify the components in a laboratory prior to their launch. This thesis has contributed in two aspects to this area. Firstly, a new sample has been developed to characterise multipactor measurement benches up to Ka-band frequencies. On the other hand, a set of multiplexers has been fully designed and integrated into a multipactor test bench with different carriers, resulting in a scenario more similar to the one found in real satellite communication systems. In addition, the design of these multiplexers has led to the development of a systematic methodology, which has made it possible to design these components with high accuracy and in a relatively short time. Last but not the least, regarding the design of passive microwave components operating at high frequencies, this doctoral thesis has delved into the MHFRW family of filters. These filters, due to their geometric properties, are appropriate for high power applications that require low levels of PIM. This topology, which has been studied in recent years, has been enhanced by increasing its capacity to implement super-elliptic responses, namely responses including more transmission zeros than the order of the filter. In addition, it allows to place the zeros in arbitrary locations independently. This provides great flexibility to the designer and also allows high rejection levels to be obtained, giving rise to a family of filters ideal for various applications, ranging from filters for satellite payloads to the implementation of multiplexers for passive intermodulation measurement test beds. / González Santatecla, P. (2024). High Power Effects in Microwave Filters for Space Applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/207526

För sammankoppling av multi-terminala HVDC-system med punkt-till-punkt kopplingar ärDC-DC-omvandlaren den enda möjliga sammankopplingen. Därför genomgår problemenmed spänningsmatchning och likspänningsströmbegränsning i högspännings DC-systemomfattande forskning samt ligger i fokus för denna avhandling. Först analyseras toppmodernatopologier för högspännings DC-DC-omvandlare som används för samtrafik av flera terminalaHVDC-system. De analyserade topologierna jämförs sedan baserat på dess olika funktioner.Topologin för en konventionell icke-isolerad DC-DC-omvandlare analyseras när det gäller design,kostnad, storlek, förlust och effektstyrningskapacitet. Först skapas en matematisk modell ochsedan utförs en numerisk analys för olika arbetsområden. Därefter görs en jämförelse av entvåfas-icke-isolerad DC-omvandlare baserad på energilagring, maximal likströmsöverföring ochtotala förluster. Simulering utförs av en tvåfas och en trefas icke-isolerad DC-omvandlare iPSCAD med olika typer av styrenheter. Dessutom tas en isolerad omvandlartopologi och analyserasi detalj från matematisk modellering till validering med hjälp av simuleringsresultat.Olika typer av felanalyser för både isolerad och icke-isolerad omvandlartopologi görs. Slutligenutförs även analyser av DC-felet i olika möjliga anslutningar av omvandlaren i Multi-TerminalGrid, dvs Monopole, Bipole med både symmetriska och asymmetriska konfigurationer. / For interconnection of multi-terminal HVDC systems involving point-to-point links, aDC-DC converter is the only possible way to interconnect. Therefore, the issues of voltagematching and DC fault current limiting in high voltage DC systems are undergoing extensiveresearch and are the focus of this thesis. Starting with analyzing the state of the art highvoltage DC-DC converter topologies for interconnection of multi-terminal HVDC systems andbenchmarking each converter topology based on different functionalities. A basic non-isolatedDC-DC converter topology is analyzed in terms of design, cost, sizing, losses and power controlcapability. First, starting with the mathematical modeling and then the numerical analysis isdone for different operating regions. Next, it is compared with the two-phase non-isolated DCconverter based on energy storage, maximum DC power transfer, and total losses. Simulation oftwo-phase and three-phase non-isolated DC converter is done in PSCAD incorporating differenttypes of controllers. Then, an isolated converter topology is taken and analyzed in detail startingfrom mathematical modeling to validation using simulation results. Different types of faultsanalysis for both isolated and non-isolated converter topology is done. Finally, analyzing the DCfault in different possible connection of the converter in the multi-terminal grid, i.e. monopole,bipole in both symmetric and asymmetric configurations.

Les structures de conversion multiniveaux permettent de convertir en moyenne tension et forte puissance. Celles-ci sont construites à partir de cellules de commutations et permettent d’augmenter le courant et la tension en entrée ou en sortie. Ces structures sont appelées multiniveaux car les formes d’ondes des tensions en sortie permettent d’avoir plus de deux niveaux de tension différents. Les différentes structures peuvent être classées dans différentes catégories tel que la mise en série de pont en H, les convertisseurs multicellulaires série ou parallèle ou encore les structures utilisant le fractionnement du bus continu. Toutes ces structures ont des propriétés et applications différentes, même si certaines structures ont des propriétés communes. Il est aussi possible de créer de nouvelles structures en mixant les différentes structures de bases des différentes familles de convertisseurs multiniveaux ou en assemblant les structures de base de la conversion statique. Même si l’utilisation de structure de conversion multiniveaux permet de convertir à forte puissance, celle-ci n’est pas toujours aisée. En effet l’augmentation du nombre de niveaux ou de la tension d’entrée implique également une augmentation du nombre de composants semiconducteurs. Ceci peut être un frein à l’utilisation de convertisseur multiniveaux. Pour cela une nouvelle structure utilisant des composants partagés entre les différentes phases est proposée afin de limiter leur nombre. Un autre problème important lié aux convertisseurs multiniveaux est l’équilibrage des tensions des condensateurs du bus continu si celui-ci est composé de plus de deux condensateurs mis en série. Pour cela plusieurs solutions sont possibles : soit en utilisant une commande spécifique utilisant la modulation vectorielle, soit en utilisant des structures auxiliaires qui ont pour but d’équilibrer les différentes tensions des condensateurs. Dans une dernière partie ont été proposées de nouvelles structures qui permettent à la fois d’augmenter le courant de sortie et la tension en entrée en utilisant les principes des structures de base des convertisseurs multicellulaires série et parallèle. De plus, ces structures ont des propriétés intéressantes sur les formes d’ondes de sortie. De ces structures a été conçu un prototype permettant de valider les résultats de simulation. Une commande numérique implantée sur FPGA a été réalisée et a permis d’avoir des résultats expérimentaux intéressants. / This PhD Thesis deals with the study of new multilevel structures. At the beginning of this work, a new methodology to create new multilevel structures has been conceived. To evaluate the performances of these structures, there are many possibilities: number of output voltage levels, number of components, and the quality of the converters’ output waveforms. The list of criteria is not exhaustive. One technique to obtain an output multilevel waveform is to split the DC link in several capacitors. There is a limitation since putting more than two capacitors in serial connection leads to an unbalancing of these voltage capacitors. Several solutions are possible to balance these voltages. The first one uses the control of the structure in a three phase application, using a space vector modulation and minimizing the energy stored in the DC link. The second solution consists in using auxiliary circuits, which realize an energy transfer between one capacitor to another through an inductor. The drawback of this method is the high number of components. This problem can be reduced sharing some components between the three phases of the converter. The third part of this study is related to multicell converters, structures with very interesting good properties. New converter structures mix serial and parallel multicell converters, to obtain a hybrid converter with similar performances to the two basic converters. An experimental prototype was built to validate the results of the PhD. The digital control of this hybrid structure was made with a FPGA where two DSP processors were implemented.

Cette thèse porte sur la conception, la réalisation et la caractérisation de diodes lasers de puissance, faible bruit à 1.5 µm sur InP pour des applications d’optique hyperfréquence, notamment pour des liaisons optiques analogiques de grande dynamique pour les systèmes radar. La première partie du travail a consisté à modéliser et concevoir des structures laser DFB ayant de faibles pertes internes. Ces structures, appelées lasers à semelle, incorporent une couche épaisse de matériaux entre la zone active et le substrat pour agrandir et délocaliser le mode propre optique des zones dopées p. La complexité de la conception résidait dans le bon compromis à trouver entre les performances statiques et dynamiques. Nous avons réalisé des diodes-lasers DFB avec une puissance > 150 mW, un rendement de 0.4 W/A, un niveau de bruit de 160 dB/Hz et une bande passante de modulation à 3 dB de 7.5 GHz. Les composants ont ensuite été caractérisés puis évalués dans des liaisons analogiques. Nous avons démontré des performances de gain de liaison, de dynamique et de point de compression à l’état de l’art mondial. En bande L (1-2 GHz) par exemple, nous avons montré des liaisons avec 0.5 dB de gain, un point de compression de 21 dBm et une dynamique (SFDR) de 122 dB.Hz2/3.En utilisant la même méthodologie de conception, la dernière partie du travail de thèse a été consacrée à la réalisation et à la caractérisation de lasers de puissance à verrouillage de modes pour la génération de train d’impulsions ultra-courts et la génération de peignes de fréquences. Ces structures présentent de très faibles largeurs de raie RF (550 Hz) et de très fortes puissances optiques (> 18 W en puissance crête). / This work focuses on the design, realization and characterization of high power, low noise 1.5 µm diode lasers for microwave applications and more particularly for high dynamic optical analog link for radar systems. The first part of this study deals with modeling and design of low internal losses DFB laser structures. These specific structures are called slab-coupled optical waveguide lasers, and are composed of a thick layer between the active layer and the substrate. The aim of this waveguide is to enlarge the optical eigenmode and to move the optical mode away from p-doped layers. The main difficulty was to find the good trade-off between laser static performances (optical power, efficiency) and dynamic performances (RIN and modulation bandwidth). We have succeeded in developing high efficiency (0.4 W/A), low noise (RIN ≈ 160 dB/Hz) DFB lasers with more than 150 mW and a 3 dB modulation bandwidth up to 7.5 GHz. We have then characterized our components on wide band and narrow band analog links. We have demonstrated state of the art gain links, dynamic and 1 dB compression power. In the L band (1-2 GHz) for example, we have obtained an optical link with a gain of 0.5 dB, a compression power of 21 dBm and a dynamic (SFDR) of 122 dB.Hz2/3.Finally we have applied the methodology and the design of slab-coupled optical waveguide structures to develop high power mode-locked lasers for ultra-short pulses generation and for optical and electrical comb generation. We have demonstrated narrow RF linewidth (550 Hz) lasers with very high power (continuous power > 400 mW and peak power > 18 W).

In high-power electric drives, multilevel inverters are generally deployed to address issues such as electromagnetic interference, switch voltage stress and harmonic distortion. The switching frequency of the inverter is always kept low, of the order of 1KHz or even less to reduce switching losses and synchronous pulse width modulation (PWM) is used to avoid the problem of sub-harmonics and beat frequencies. This is particularly important if the switching frequency is very low. The synchronous PWM is getting popularity as its realization is very easy with digital controllers compared to analog controllers. Neutral-point-clamped (NPC) inverters, cascaded H-bridge, and flying-capacitor multilevel inverters are some of the popular schemes used for high-power applications. Hybrids of these multilevel inverters have also been proposed recently to take advantage of the basic configurations. Multilevel inverters can also be realized by feeding the induction motor from both ends (open-end winding) using conventional inverter structures. For controlling the output voltage of these inverters, various PWM techniques are used. Chapter-1 of this thesis provides an over view of the various multilevel inverter schemes preceded by a discussion on basic two-level VSI topology. The inverters used in motor drive applications have to be operated in over-modulation range in order to extract the maximum fundamental output voltage that is possible from the dc-link. Operation in this high modulation range is required to meet temporary overloads or to have maximum power operation in the high speed range (flux weakened region). This, however, introduces a substantial amount of low order harmonics in the Motor phase voltages. Due to these low-order harmonic frequencies, the dynamic performance of the drive is lost and the current control schemes are severely affected especially due to 5th and 7th harmonic components. Further, due to these low-order harmonics and non-linear PWM operation in over-modulation region, frequent over-current fault conditions occur and reliability of the drive is jeopardized. The twelve sided-polygonal space vector diagram (dodecagonal space vectors) can be used to overcome the problem of low order 5th and 7th harmonics and to give more range for linear modulation while keeping the switching frequency at a minimum compared to conventional hexagonal space vector based inverters. Thus, the dodecagonal space-vector switching can be viewed as an engineering compromise between low switching frequency and quality load current waveform. Most of the previous works of dodecagonal space-vector generation schemes are based on NPC inverters. However, sophisticated charge control schemes are required in NPC inverters to deal with the neutral-point voltage fluctuation and the neutral-point voltage shifting issues. The losses in the clamping diodes are another major concern. In the second chapter, a multilevel dodecagonal space-vector generation scheme based on flying capacitor topology, utilizing an open end winding induction motor is presented. The neutral point charge-balancing problem reported in the previous works is not present in this scheme, the clamping diodes are eliminated and the number of power supplies required has been reduced. The capacitors have inherent charge balancing capability, and the charge control is done once in every switching cycle, which gives tight voltage control for the capacitors. For the speed control of induction motors, the space-vector PWM scheme is more advantageous than the sine-triangle PWM as it gives a more linear range of operation and improved harmonic performance. One major disadvantage with the conventional space-vector PWM is that the trigonometric operations demand formidable computational efforts and look-up tables. Carrier based, common-mode injected PWM schemes have been proposed to simplify the PWM process. However, the freedom of selecting the PWM switching sequences is limited here. Another way of obtaining SVPWM is using the reference voltage samples and the nearest vector information to switch appropriate devices for proper time intervals, realizing the reference vector in an average sense. In-formation regarding the sector and nearest vectors can be easily obtained by comparing the instantaneous amplitudes of the reference voltages. This PWM approach is pro-posed for the speed control of the motor in this thesis. The trigonometric operations and the requirement of large look-up tables in the conventional SVPWM are avoided in this method. It has the additional advantage that the switching sequences can be decided at will, which is helpful in reducing further, the harmonic distortion in certain frequency ranges. In this way, this method tries to combine the advantages of vector based methods (conventional SVPWM) and scalar methods (carrier-based methods). The open-end winding schemes allowed the required phase voltage levels to be generated quite easily by feeding from both ends of the windings. Thus, most of the multilevel inverters based on dodecagonal space-vector structures relied on induction motors with open-end windings. The main disadvantage of open-end winding induction motor is that six wires are to be run from the inverter to the motor, which may be unacceptable in certain applications. Apart from the inconvenience of laying six wires, the voltage reflections in the wires can lead to over voltages at the motor terminals, causing insulation failures. Where as the topology presented in chapter-2 of this thesis uses open-end winding motor with flying-capacitor inverters for the generation of dodecagonal space-vectors, the topology presented in chapter-3 utilizes a cascade connection of flying-capacitors and floating H-bridge cells to generate the same set of voltage space-vectors, thus allowing any standard induction motor as the load. Of the methods used for the speed control of induction motors, namely sine-triangle PWM and space vector PWM, the latter that provides extra modulation range is naturally preferred. It is a well-understood fact that the way in which the PWM switching sequences are applied has a significant influence on the harmonic performance of the drive. However, this topic has not been addressed properly for dodecagonal voltage space-vector based multilevel inverter drives. In chapter-4 of the thesis, this aspect is taken into ac-count and the notion of “harmonic flux trajectories” and “stator flux ripple” are used to analyze the harmonic performance of the various PWM switching schemes. Although the PWM method used in this study is similar to that in chapter-2, the modification in the PWM switching sequence in the PWM algorithm yields significant improvements in harmonic performance. The proposed topologies and PWM schemes are extensively simulated and experimentally verified. The control scheme was implemented using a DSP processor running at a clock frequency 150MHz and a four-pole, 3.7kW, 50Hz, 415V three-phase induction motor was used as the load. Since the PWM ports are limited in a DSP, a field-programmable gate array (FPGA) was used to decode the PWM signals from the DSP to generate timing information required for PWM sequencing for all the power devices. The same FPGA was used to generate the dead-time signals for the power devices also.