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Panofski, Eva. "Beam Dynamics and Limits for High Brightness, High Average Current Superconducting Radiofrequency (SRF) Photoinjectors." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/19962.
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Zukünftige Beschleunigerprojekte und Nutzerexperimente erfordern für ihren Betrieb einen hochbrillanten Elektronenstrahl mit hohem mittlerem Strom. Eine Elektronenquelle mit dem Potential die Anforderungen erfüllen, ist ein supraleitender Hochfrequenz (SHF) Photoinjektor im Dauerstrichbetrieb.
Die Strahldynamik eines solchen Photoinjektor Systems bestimmt die maximal zu erreichende Strahlbrillanz und wird ihrerseits von den Design und Betriebsparametern des Photoinjektors beeinflusst. Ziel ist immer die entscheidenden Design- und Betriebsparameter der Elektronenquelle hinsichtlich einer maximalen Strahlbrillanz zu wählen. Diese Aufgabe verlangt ein detailliertes Verständnis der Strahldynamik-Prozesse. Ferner ist es notwendig, eine Optimierung des Photoinjektors als Ganzes, mit dem Ziel einer maximalen Strahlqualität bei hohem mittlerem Strom, vorzunehmen. Dieses ermöglicht auch, die physikalischen Grenzen eines gegebenen Designs zu ermitteln und im Betrieb vollständig auszunutzen.
Diese Doktorarbeit befasst sich mit der Strahldynamik in einem SHF Photoinjektor, unter Berücksichtigung interner Raumladungseffekte. Die Erkenntnisse zur Strahldynamik werden für die Entwicklung eines Optimierungsprogramms verwendet, um die Leistung des Injektors hinsichtlich der Strahlbrillanz zu verbessern. Die entwickelte Methode basiert auf Pareto-Optimierung mehrerer Zielfunktionen, unter Verwendung eines generischen Algorithmus. Das zentrale Ergebnis dieser Arbeit umfasst ein universelles Optimierungsprogramm, das für Photoinjektoren unabhängig von ihrem Design und Anwendungsgebiet genutzt werden kann. Für den Betrieb mit hoher Strahlbrillanz ist es möglich aus den erhaltenen Pareto-optimalen Lösungen einen stabilen Satz an Einstellwerten für den Photoinjektor zu extrahieren. Durch die allgemeine Optimierungsstrategie lässt sich das entwickelte Programm auch für andere Beschleunigerabschnitte, oder die Optimierung einer ganzen Anlage mit erweiterter Zielsetzung anpassen.An increasing number of future accelerator projects, light sources and user experiments require high brightness, high average current electron beams for operation. Superconducting radio-frequency (SRF) photoinjectors running in continuous-wave (cw) mode hold the potential to serve as an electron source that generates electron beams of high brightness. Different operation and design parameters of the SRF photoinjector impact the beam dynamics and, thus, the beam brightness. Therefore, an in-depth understanding of the beam dynamics processes in an SRF photoinjector and the dependency of the beam dynamics on the photoinjector set parameters is crucial. A high brightness beam operation requires a global optimization of the SRF photoinjector that allows to find suitable photoinjector settings and to figure out and extend the physical performance limits of the investigated injector design. The dissertation at hand offers a detailed analysis of the beam dynamics in an SRF photoinjector regarding internal space charge effects. Furthermore, the impact of the photoinjector elements on the electron beam is discussed. The lessons learned from this theoretical view are implemented in the development of an optimization tool to achieve a high brightness performance. A universal multi-objective optimization program based on a generic algorithm was developed to extract stable, optimum gun parameter from Pareto-optimum solutions. This universal tool is able to optimize and find the physical performance limit of any (S)RF photoinjector independent from the individual application of the electron source (energy recovery linac, free electron laser, ultra-fast electron diffraction). This thesis thereby verifies and complements existing theoretical considerations regarding photoinjector-beam interactions. The global optimization strategy can be introduced to variable optimization objectives as well as it can be extended to an optimization of further parts of the accelerator facility.
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Zhou, Jinghai. "High Frequency, High Current Density Voltage Regulators." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/27268.
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As a very special DC-DC converter, VRM (Voltage Regulator Module) design must follow the fast-developing trend of microprocessors. The design challenges are the high current, high di/dt, and stringent load-line requirement. When the energy is transferred from the input of a VRM, through the VRM, then through the power delivery path to the processor, it needs sufficient capacitors to relay this energy. The capacitorsâ number appears to be unrealistically large if we follow todayâ s approach for the future processors. High frequency VRM with high control bandwidth can solve this problem, however, the degradation of efficiency makes the conventional buck converter and the hard-switching isolated topologies incapable of operating at higher frequency. The research goal is to develop novel means that can help a high-output- current VRM run efficiently at high frequency.
A novel Complementary Controlled Bridge (CCB) self-driven concept is proposed. With the proposed self-driven scheme, the combination of the ZVS technique and the self-driven technique recycles the gate driving energy by making use of the input capacitor of the secondary- side synchronous rectifier (SR) as the snubber capacitor of the primary-side switches. Compared to the external driver, the proposed converter can save driving loss and synchronous rectifier body diode conduction loss. Additionally, compared to the existing level-shifted self-driven scheme for bridge-type symmetrical topologies, its gate signal ringing is small and suitable for high-frequency applications.
Although the CCB self-driven VRM reduces the switching frequency-related losses significantly, the conduction loss is still high. Inspired by the current-doubler concept, a novel ZVS current-tripler DC-DC converter is proposed in this work. By utilizing more SR devices to share the current during the freewheeling period, the SR conduction loss is reduced. The current-tripler DC-DC converter has a delta/delta connected transformer that can be implemented with integrated magnetics. The transformer then becomes an integrated magnetic with distributed windings, which is preferred in high current applications. The current-tripler DC-DC converter in fact meets the requirements for the CCB self-driven scheme. The two concepts are then combined with an integrated gate drive transformer.
The proposed CCB self-driven concept and current-tripler concept can both be applied to the 12V non-isolated VRMs. The proposed topology is basically a buck-derived soft-switching topology with duty cycle extension and SR device self-driven capabilities. Because there is no isolation requirement, the SR gate driving becomes so simple that the voltage at the complementary controlled bridge can be used to directly drive the SR gate. Both the gate driving loss and the SR body diode conduction loss are reduced. The proposed circuit achieves similar overall efficiency to a conventional 300kHz buck converter running at 1MHz.
All the circuits proposed in this dissertation can use coupling inductors to improve both the steady-state efficiency and dynamic performances. The essence of the coupling inductors concept is to provide different equivalent inductances for the steady state and the transient. Moreover, when a current loop becomes necessary to achieve proper current sharing among phases, the current loop sample hold effect will make it difficult to push the bandwidth. The sample hold effect is alleviated by the coupling inductors concept. A small-signal model is proposed to study the system dynamic performance difference with different coupling inductor designs. As the verification, the coupling concept is applied to the 12V non-isolated CCB self-driven VRM and the bandwidth as high as one third of the switching frequency is achieved, which means a significant output capacitor reduction.Ph. D.
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Hayatleh, Khaled. "High frequency current-mode precision rectifiers." Thesis, Oxford Brookes University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308928.
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Reusch, David Clayton. "High Frequency, High Current Integrated Magnetics Design and Analysis." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/35420.
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The use of computers in the modern world has become prevalent in all aspects of life. The size of these machines has decreased dramatically while the capability has increased exponentially. A special DC-DC converter called a VRM (Voltage Regulator Module) is used to power these machines. The VRM faces the task of supplying high current and high di/dt to the microprocessor while maintaining a tight load regulation. As computers have advanced, so have the VRM's used to power them. Increasing the current and di/dt of the VRM to keep up with the increasing demands of the microprocessor does not come without a cost. To provide the increased di/dt, the VRM must use a higher number of capacitors to supply the transient energy. This is an undesirable solution because of the increased cost and real estate demands this would lead to in the future. Another solution to this problem is to increase the switching frequency and control bandwidth of the VRM. As the switching frequency increases the VRM is faced with efficiency and thermal problems. The current buck topologies suffer large drops in efficiency as the frequency increases from high switching losses.
Resonant or soft switching topologies can provide a relief from the high switching loss for high frequency power conversion. One disadvantage of the resonant schemes is the increased conduction losses produced by the circulating energy required to produce soft switching. As the frequency rises, the additional conduction loss in the resonant schemes can be smaller than the switching loss encountered in the hard switched buck. The topology studied in this work is the 12V non-isolated ZVS self-driven presented in [1]. This scheme offered an increased efficiency over the state of the art industry design and also increased the switching frequency for capacitor reduction. The goal of this research was to study this topology and improve the magnetic design to decrease the cost while maintaining the superior performance.
The magnetics used in resonant converters are very important to the success of the design. Often, the leakage inductance of the magnetics is used to control the ZVS or ZCS switching operation. This work presents a new improved magnetic solution for use in the 12V non-isolated ZVS self-driven scheme which increases circuit operation, flexibility, and production feasibility. The improved magnetic structure is simulated using 3D FEA verification and verified in hardware design.
Master of Science
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Mahattanakul, Jirayuth. "High frequency, low distortion current-mode filters." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300970.
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Worapishet, Apisak. "High frequency low power switched-current techniques." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392911.
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Egnor, Dianne Elizabeth. "High-frequency acoustic tomography in a high-current coastal environment." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/88350.
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Su, Yipeng. "High Frequency, High Current 3D Integrated Point-of-Load Module." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51248.
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Point-of-load (POL) converters have been used extensively in IT products. Today, almost every microprocessor is powered by a multi-phase POL converter with high output current, which is also known as voltage regulator (VR). In the state-of-the-art VRs, the circuits are mostly constructed with discrete components and situated on the motherboard, where it can occupy more than 1/3 of the footprint of the motherboard. A compact POL is desirable to save precious space on motherboards to be used for some other critical functionalities. Recently, industry has released many modularized POL converters, in which the bulky inductor is integrated with the active components to increase the power density. This concept has been demonstrated at current levels less than 5A and power density around 600-1000W/in3. This might address the needs of small hand-held equipment such as smart phones, but it is far from meeting the needs for the applications such as laptops, desktops and servers, where tens and hundreds of amperes are needed.
A 3D integrated POL module with an output current of tens of ampere has been successfully demonstrated at the Center for Power Electronic Systems (CPES), Virginia Tech. In this structure, the inductor is elaborated with low temperature co-fire ceramic (LTCC) ferrite, as a substrate where the active components are placed. The lateral flux inductor is proposed to
achieve both a low profile and high power density. Generally, the size of the inductor can be continuously shrunk by raising the switching frequency. The emerging gallium-nitride (GaN) power devices enable the creation and use of a multi-MHz, high efficiency POL converter. This dissertation firstly explores the LTCC inductor substrate design in the multi-MHz range for a high-current POL module with GaN devices. The impacts of different frequencies and different LTCC ferrite materials on the inductor are also discussed. Thanks to the DC flux cancellation effect, the inverse coupled inductor further improves the power density of a 20A, 5MHz two-phase POL module to more than 1kW/in3. An FEA simulation model is developed to study the core loss of the lateral flux coupled inductor, which shows the inverse coupling is also beneficial for core loss reduction.
The ceramic-based 3D integrated POL module, however, is not widely adopted in industrial products because of the relatively high cost of the LTCC ferrite material and complicated manufacturing process. To solve that problem, a printed circuit board (PCB) inductor substrate with embedded alloy flake composite core is proposed. The layerwise magnetic core is laminated into a multi-layer PCB, and the winding of the inductor then is formed by the copper layers and conventional PCB vias. As a demonstration of system integration, a 20A, 1.5MHz integrated POL module is designed and fabricated based on a 4-layer PCB with embedded flake core, which realizes more than 85% efficiency and 600W/in3 power density. The application of standardized PCB processes reduces the cost for manufacturing the integrated modules due to the easy automation and the low temperature manufacturing process. Combining the PCB-embedded coupled inductor substrate and advanced control strategy, the two-phase 40A POL modules are elaborated as a complete integrated laptop VR solution. The coupled inductor structure is slightly modified to improve its transient performance. The nonlinearity of the inductance is controlled by adding either air slots or low permeability magnetic slots into the leakage flux path of the coupled inductor. Then the leakage flux, which determines the transient response of the coupled inductor, can be well controlled. If we directly replace the discrete VR solution with the proposed integrated modules, more than 50% of the footprint on the motherboard can be saved.
Although the benefits of the lateral flux inductor have been validated in terms of its high power density and low profile, the planar core is excited under very non-uniform flux. Some parts of the core are even pushed into the saturation region, which totally goes against the conventional sense of magnetic design. The final part of this dissertation focuses on evaluating the performance of the planar core with variable flux. The counterbalance between DC flux and AC flux is revealed, with which the AC flux and the core loss density are automatically limited in the saturated core. The saturation is essentially no longer detrimental in this special structure. Compared with the conventional uniform flux design, the variable flux structure extends the operating point into the saturation region, which gives better utilization of the core. In addition, the planar core with variable flux also provides better thermal management and more core loss reduction under light load.
As conclusions, this research first challenges the conventional magnetic design rules, which always assumes uniform flux. The unique characteristics and benefits of the variable flux core are proved. As an example of taking advantages of the lateral flux inductor, the PCB integrated POL modules are proposed and demonstrated as a high-density VR solution. The integrated modules are cost-effective and ready to be commercialized, which could enable the next technological innovation for the whole computing and telecom industry.Ph. D.
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PIDUTTI, ALBINO. "High Frequency Buck Converter for Automotive Current Source Applications." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/404716.
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Il presente lavoro e’ stato svolto in cooperation tra l’infineon e l’Universita’ Milano Bicocca, l’obbiettivo e’ sviluppare il cuore di un convertitore DC-DC Buck Converter ad alta frequenza di commutazione.
I convertitori a commutazione offrono un modo semplice ed efficiente per alimentare carichi elettronici. Inoltre, gli alimentatori DC-DC consentono di soddisfare efficacemente molti requisiti di sicurezza delle automobili moderne. Ad esempio è assolutamente necessario che le luci di emergenza, i fari e le luci dei freni mantengano la loro funzionalità in tutte le condizioni, soprattutto durante l'avviamento a freddo, quando la tensione della batteria raggiunge valori molto bassi (anche 4V). Ma in certe condizioni esperimentano tensioni anche superiori ai 30V.
Gli alimentatori DC-DC ben si adattano ad ampie e repentine variazioni della tensione di alimentazione, inoltre alla loro relativa semplicità uniscono un’alta efficienza, valori superiori al 90%.
Aumentando la frequenza di commutazione si riducono linearmente le dimensioni dei componenti reattivi, permettendo schede PCB più piccole e conseguentemente costi ridotti.
Le tecnologie BCD consentono di integrare su un singolo chip (SOC - System On Chip) transistor di potenza, logica di controllo e diagnostica.
In questa ricerca sono stati sviluppati tre convertitori Buck che lavorano a tre diverse frequenze 1MHz, 4MHz e 10MHz con una corrente di uscita di 3A. Tra i Buck converter disponibili sul mercato solo quelli più performanti hanno frequenze di commutazione di 2,0-2,5 MHz e correnti nel carico di 2-2,5 A.
Poiché l'obiettivo di 10MHz con una corrente di carico di 3A è molto aggressivo, è stata adottata un'architettura del convertitore Buck che minimizza il tempo di transizione dei segnali elettrici ed è stato necessario sviluppare una nuova topologia di driver molto più veloce e potente delle soluzioni adottate finora (patent pending).
Al momento in cui scriviamo, i dispositivi da 1 MHz e 4 MHz sono in fase di diffusione. L'uscita dei wafer è prevista per febbraio 2023. Il terzo convertitore Buck (10 MHz) e’ in attesa di diffusione.
Durante questo lavoro di dottorato sono state presentate quattro proposte di brevetto.This work was carried out in cooperation between Infineon and the University of Milan Bicocca, the aim being to develop the core of a DC-DC Buck Converter with a high switching frequency. Switching converters offer a simple and efficient way to power electronic loads. In addition, DC-DC power supplies make it possible to effectively meet many safety requirements of modern automobiles. For example, it is absolutely necessary that emergency lights, headlights and brake lights maintain their functionality under all conditions, especially during cold starting, when the battery voltage reaches very low values (even 4V). But under certain conditions they experience voltages even above 30V. DC-DC power supplies are well suited to large and sudden variations in supply voltage, and in addition to their relative simplicity they combine high efficiency, values of over 90%. Increasing the switching frequency reduces the size of reactive components linearly, allowing smaller PCBs and consequently lower costs. BCD technologies allow power transistors, control logic and diagnostics to be integrated on a single chip (SOC - System On Chip). In this research, three Buck converters were developed that operate at three different frequencies 1MHz, 4MHz and 10MHz with an output current of 3A. Of the buck converters available on the market, only the best performing ones have switching frequencies of 2.0-2.5MHz and load currents of 2-2.5A. Since the target of 10MHz with a load current of 3A is very aggressive, a Buck converter architecture was adopted that minimises the transition time of electrical signals, and a new driver topology had to be developed that is much faster and more powerful than the solutions adopted so far (patent pending). At the time of writing, 1 MHz and 4 MHz devices are being deployed. The wafers are scheduled for release in February 2023. The third Buck converter (10 MHz) is pending deployment. Four patent proposals were submitted during this doctoral work.
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Liu, Kwang-Hwa. "High-frequency quasi-resonant converter techniques." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/74737.
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Two waveform-shaping techniques to reduce or eliminate the switching stresses and switching losses in switching-mode power conversion circuits are developed: the zero-current switching technique and the zero-voltage switching technique.
Based on these two techniques two new families of quasi-resonant converters are derived. Since the stresses on semiconductor switching devices are significantly alleviated, these quasi-resonant (QRC) converters are suitable for high-frequency operations with much improved performances and equipment power density.
Employing the duality principle, the duality relationship between these two families of quasi-resonant converters are derived. The establishment of the duality relationship provides a framework allowing the knowledge obtained from one converter family to be readily transferred to the other.
Further topological refinements are derived through the utilization of parasitic elements in the devices and the circuit. In particular, the two most significant parasitic elements, the leakage inductance of the transformer and the junction capacitances of the semiconductor switch, are incorporated as part of the resonant-tank circuit required by these quasi-resonant converters. Consequently, the detrimental effects due to these parasitic elements are eliminated, and the converters can be operated at very high frequencies.Ph. D.
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Teske, Nikolas. "Sensorless position control of induction machines using high frequency signal injection." Thesis, University of Nottingham, 2001. http://eprints.nottingham.ac.uk/13117/.
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The aim of this research project was to develop a position controlled induction machine vector drive operating without a speed or position sensor but having a dynamic performance comparable to that of a sensored position vector drive. The methodology relies on the detection of a rotor saliency in the machine by persistent high-frequency voltage injection. The rotor position is then estimated from the resulting stator current harmonics that are modulated by the spatial rotor saliency. This can be a built-in rotor saliency (a designed asymmetry) or the natural saliency due to rotor slotting. This project investigates the demodulation of the extracted high-frequency current spectrum and different topologies for the estimation of rotor position. The tracking of rotor position through rotor saliencies helps to overcome the limitations of model-based approaches that are restricted to speeds above 30rpm on a 4-pole machine and are sensitive to parameter mismatches. The project addresses the difficult problem of separating the modulation effects due to the rotor saliency from distorting modulations due to the saturation saliency and inverter effects. In previous research it had been found that the saturation saliency causes a deterioration of the position estimate that can result in a loss of position and eventually causes the drive to fail. The application of filters to remove the interfering saturation harmonics is not possible. In this research a new approach was developed that compensates online for the saturation effect using pre-commissioned information about the machine. This harmonic compensation scheme was utilized for a 30kW, 4-pole induction machine with asymmetric rotor and enabled the operation from zero to full load and from standstill up to about ±150rpm (±5Hz). The steady-state performance and accuracy of the resulting sensorless drive has been found to operate similarly to a sensored drive fitted with a medium resolution encoder of 600ppr. The project involved studies of the inverter switching deadtime and its distorting effect on the position estimation. A second compensation strategy was therefore developed that is better suited if a large interfering modulation due to the inverter deadtime is present in the machine. The new compensation method was implemented for a second 30kW machine that utilizes the rotor slotting saliency. Good tracking results were obtained with a mean error of less than ±0.5° mechanical under steady-state. The derivation of the position signal for higher speeds introduces an additional speed-dependent error of about 4° mechanical at 170rpm. Sensorless position control was realized for operation from zero to full load for the fully fluxed machine. The performance allowed low and zero speed operation including position transients reaching a speed of 50rpm. The high-frequency modulation introduced by the fundamental currents during transient operation was examined and identified as the main factor limiting the dynamics of the sensorless drive. Two rigs were used for the research. The first rig is build around a network of Transputers, the second rig uses state-of-the-art TMS320C40 and TMS320F240 digital signal processors for the control and was designed and constructed as part of the research.
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Holme, Peter R. "Digital control of high frequency PWM convertors." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/7160.
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The thesis begins with a review of presently available analogue and digital control schemes for high frequency PWM converters. Advantages and disadvantages of each scheme are identified, to determine which features would be desirable in a new digital control scheme. An extensive examination of peak and average current mode control is undertaken, using state-space/sampled data modelling, to gain more detailed information on the properties of current mode control. On the basis of this information, a new digital current mode control scheme is put forward. This uses samples of the inductor current, line voltage and output voltage to implement a control strategy in software. Average inductor current is calculated each switching cycle and compared to the current program level, providing true current mode control. This has some advantages over traditional methods. Accurate inductor current tracking of the current program level is achieved and no slope compensation is required for stable operation over the full range of duty ratios. Line voltage feed-forward is possible in buck derived topologies, which provides an effective null in the audio susceptibility transfer function, independent of compensation parameters. Current loop stability is independent of line voltage or load current in the buck topology, allowing operation with optimum loop compensation under all normal operating conditions. Practical implementation of a digital current mode controlled current-fed converter is described. This includes a modular architecture for the hardware and documentation for the software. Effects of component selection on the achievable converter switching frequency and dynamic performance are discussed. A method is put forward for the direct digital measurement of loop gain and phase in digital control systems. This is used to obtain actual loop responses from a test bed digital current mode controlled current-fed converter. Line and load transient response tests are presented which demonstrate the dynamic characteristics of digital current mode control.
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Bloomfield, Aaron Paul. "A High Frequency Alternating Current Battery Heater for Military Vehicles." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302312903.
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Zhang, Xiaokai. "Novel magnetic composites for high frequency applications /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 190 p, 2009. http://proquest.umi.com/pqdweb?did=1654494811&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Li, Hao Leo. "High frequency power converters based on energy injection control for IPT systems." Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/7160.
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A contactless power transfer system has many advantages over conventional power transmission due to the elimination of direct electrical contacts. With the development of modern technologies, IPT (Inductive Power Transfer) has become a very attractive technology for achieving wireless/contactless power transfer over the past decade. IPT has been successfully employed in many applications for materials handling, lighting, transportation, bio-medical implants, etc. To transfer power across an air gap, an IPT system employs a primary power converter to generate a high frequency alternating current in a track/coil which is then magnetically coupled to one or more power pick-ups. The design and implementation of the primary side power converter and controller are of great importance in an IPT system because they affect the whole system performance under both steady state and transient conditions. Therefore, any development and control improvement within the primary power converter are desirable. This thesis focuses on the development of converters for IPT systems based on circuit resonance and energy injection control. A voltage fed DC-AC energy injection inverter is introduced. Basic characteristics and underlying principles of the inverter are studied. A variable frequency ZCS (Zero Current Switching) control strategy is developed for the switching operation. The new DC-AC inverter can achieve high frequency AC power generation using relatively low switching frequencies with predicable current ripple and transient behavior. Furthermore the soft switching operation ensures low switching losses and reduced EMI. A detailed analytical method has been developed and extended to a system level by taking system bifurcation and power transfer capability into consideration. The critical boundaries of both the loading and coupling conditions are determined for designing energy injection inverters without frequency bifurcation. It has been found there is an optimal coupling coefficient which results in the maximum power transfer capability of the inverter. Using such a system level inverter design process, a primary track current regulation method based on energy injection control has been proposed. Furthermore, as an example, a practical contactless slip ring system has been developed using the proposed control method. A new type of direct AC-AC converter is also proposed. A control strategy is developed based on energy injection control for the AC-AC matrix converter to achieve a high frequency current generation with soft switching operation. The converter operation is analytically analyzed in detail, including the current ripple and sag caused by the alternating input voltage. The theoretical analysis is proven by simulation studies and practical experiments. The energy injection concept is also applied to push pull resonant converters with a “dual” transformation in performance which leads to a boost operation. A mathematical model employing a stroboscopic mapping technique is developed for a push pull inverter to find the multiple ZVS operation points. It has been proven by both simulation and experimental studies that the power transfer capability of a traditional push pull inverter can be increased significantly by operating it at selected low ZVS frequencies without using any additional front-end boost circuits.Whole document restricted until September 2013, but available by request, use the feedback form to request access.
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Zhang, Yigong. "ACTIVE CURRENT INJECTION METHOD FOR LIMITING GROUND FAULT CURRENT HARMONICS IN UNDERGROUND COAL MINES." UKnowledge, 2014. http://uknowledge.uky.edu/mng_etds/15.
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Current practice in U.S. underground coal mine high-voltage distribution systems is to attempt to limit ground fault current to 25 Amperes and de-energize the circuit at 10 Amperes. However, the significant amount of system capacitance due to the use of shielded cables can cause ground fault current to be two or three times the intended ground fault limit. Consequently, this practice can cause several issues such as ground fault currents significantly exceeding the neutral grounding resistor current limit, loss of relay selectivity in the distribution system, and transient overvoltages in certain ground fault situations. These issues are solved to some extent by using a resonance grounded system, currently used in some other countries. However, a shortcoming of traditional resonance grounded systems is the inability to deal with the harmonic components existing in ground fault current. With the increasing use of nonlinear sources such as variable frequency drives, the proportion of harmonic components in ground fault current can be significant. Consequently, although the fundamental component can be almost fully compensated in a traditional resonance grounded system, the harmonic components can still be large enough to maintain arcing and cause personal injury and equipment damage. In this dissertation, a novel method is developed to perform real-time prediction of the harmonics in ground fault currents. Methods for neutralizing the ground fault current harmonics and identifying ground fault location are also developed. Results indicate that the combination of traditional high-resistance grounding and active current injection to neutralize harmonics in the ground fault has the potential to significantly reduce the total ground fault current and reduce arc and flash hazards during ground faults in high voltage distribution systems.
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Bergstrand, Lucas. "Investigation of Sensorless Control of Permanent Magnet Synchronous Motor Using High Frequency Injection." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279498.
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This thesis implements and analyses a sensorless control method for permanent magnet synchronous motors. The purpose is to investigate if the results presented in a study performed by Millinger et al. can be replicated on an industrial grade embedded control system. The sensorless control method uses a high frequency signal injection to estimate the rotor position. The rotor is modified with copper plates in order to increase the inductance variation and the modified motor shows a 45% inductance variation. The sensorless control algorithm is implemented on an embedded control system designed for use in one of Atlas Copco’s handheld battery tools. The control system is modified by the removal of an analogue filter. The results show that the position and speed estimation is accurate enough to enable speed control for high and low speeds but the results from Millinger’s study has not been replicated.Detta examensarbete avhandlar implementering och analys av en sensorlös motorstyrning för permanent magnet synkronmotorer. Projektets fokus är att undersöka om resultatet från en tidigare studie av Millinger et al. kan reproduceras på ett industriellt inbyggt reglersystem. Motorstyrningen baseras på att rotorns position estimeras med högfrekvent signalinjektion. För att metoden ska fungera måste rotorns induktans variera avsevärt beroende av positionen. Motorn modifieras med kopparplattor för att öka induktansvariationen och efter modifikation uppvisade motorn en induktansvarians på 45%. Implementeringen av den sensorlösa motorstyrningen gjordes på ett befintligt reglersystem som designats för användning i ett av Atlas Copcos handhållna batteriverktyg. Hårdvaran modifierades genom att ta bort ett analogt filter. Resultatet visar att den sensorlösa motorstyrningen estimerar rotorns position och hastighet med tillräcklig precision för hastighetsreglering i både höga och låga hastigheter. Resultaten från Millingers studie har inte reproducerats.
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Becerra, Fajardo Laura. "Microcontrolled injectable stimulators based on electronic rectification of high frequency current bursts." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/402433.
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Neuroprostheses based on dense networks of wireless microstimulators have been proposed in the past for restoring movement in paralysis patients. Yet existing implantable microstimulators are too bulky and invasive for implementing such networks because of the powering approaches they employ.
To overcome this limitation, it was recently proposed an innovative electrical stimulation method incorporating electronic implants. The method consist in delivering, by means of superficial textile electrodes, high frequency current bursts which innocuously flow through tissues by galvanic coupling and which are rectified by the implants, thereby transforming these bursts into low frequency currents capable of performing local stimulation. Since the implants lack bulky components for powering, such as coils and batteries, the method will enable miniaturization levels without precedents for microstimulators.
The method was first demonstrated with very simple implants that could not be controlled externally, impeding independent stimulation of different target muscles. This thesis demonstrates that the method allows the development of digitally addressable microstimulators. In particular, this thesis describes the development, characterization and in vivo assay of addressable stimulators made of off-the-shelf electronic components. The developed microcontrolled and wireless stimulators are semi-rigid and can be easily implanted by injection thanks to their elongated shape (2 mm thick and almost 49 mm long). They perform charge-balanced neuromuscular stimulation in response to commands modulated in high frequency current bursts which meet safety standards. This thesis paves the way to future ultrathin stimulators based on a custom integrated circuit.En el pasado se propusieron neuroprótesis basadas en densas redes de microestimuladores inalámbricos para restablecer el movimiento en pacientes con parálisis. Aún así, los microestimuladores implantables existentes en la actualidad son demasiado voluminosos e invasivos como para implementar dichas redes debido a los métodos de alimentación eléctrica que utilizan. Para superar esta limitación, recientemente se propuso un método de estimulación eléctrica innovador que incorpora implantes electrónicos. El método consiste en aplicar mediante electrodos textiles superficiales, corrientes de alta frecuencia que fluyen inofensivamente por los tejidos por medio de acople galvánico, y que son rectificadas por los implantes. De esta forma las ráfagas se transforman en corrientes de baja frecuencia que pueden estimular localmente. Debido a que los implantes no contienen componentes voluminosos como bobinas y baterías para alimentarse eléctricamente, el método permitirá niveles de miniaturización sin precedentes para microestimuladores. El método fue demostrado por primera vez con implantes muy simples que no podían ser controlados externamente, impidiendo la estimulación independiente de diferentes músculos objetivo. Esta tesis demuestra que el método permite el desarrollo de microestimuladores direccionables digitalmente. En particular, esta tesis describe el desarrollo, caracterización y ensayos in vivo de estimuladores direccionables basados en componentes electrónicos comerciales. Los estimuladores inalámbricos desarrollados son semirrígidos y pueden ser fácilmente implantados por medio de inyección gracias a su forma alargada (2 mm de diámetro y casi 49 mm de largo). Los dispositivos realizan estimulación neuromuscular con balance de carga en respuesta a comandos modulados en las ráfagas de corriente de alta frecuencia. Dichas ráfagas de corriente cumplen con estándares de seguridad. Esta tesis abre el camino hacia futuros estimuladores ultrafinos basados en circuitos integrados diseñados para este propósito.
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Tingleff, Jens. "Current Mode Wave Active Filters : a topology for high frequency integrated filters." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337669.
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Benson, Kirk R. "High frequency subsurface Lagrangian measurements in the California Current with RAFOS floats." Thesis, Monterey, California. Naval Postgraduate School, 1995. http://hdl.handle.net/10945/35108.
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This study presents float observations from four RAFOS floats that were deployed off central California for a twenty-three day period as part of a Tomography Demonstration Experiment. These floats, which sampled hourly, were used to investigate float characteristics and the navigational accuracy of current processing techniques. An ordinary mean least square method is proposed to mathematically estimate values for random and systematic errors, producing navigational trajectories which compliment previous methods when determining the most probable solution of the float trajectory. Potential sources of error in the navigational solution are examined, as well as the importance of float/ source geometry on position accuracy. It was determined that these floats supported previous studies of the California Current System, and proposes that the California Undercurrent may in fact be wider and deeper that previously suspected. (AN)
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Kim, Kyung Cheol. "Calibration and validation of high frequency radar for ocean surface current mapping." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FKim.pdf.
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Xu, Ping. "High-frequency Analog Voltage Converter Design." PDXScholar, 1994. https://pdxscholar.library.pdx.edu/open_access_etds/4891.
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For many high-speed, high-performance circuits, purely differential inputs are needed. This project focuses on building high-speed voltage converters which can transfer a single-ended signal to a purely differential signal, or a differential input signal to a single-ended signal. Operational transconductance amplifier (OTAs) techniques are widely used in high-speed continuous-time integrated analog signal processing (ASP) circuits because resistors, inductors, integrators, buffers, multipliers and filters can be built by OT As and capacitors. Taking advantage of OT As, very-high-speed voltage converters are designed in CMOS technology. These converters can work in a frequency range from DC (OHz) up to lOOMHz and higher, and keep low distortion over a± 0.5V input range. They can replace transformers so that designing fully integrated differential circuits becomes possible. The designs are based on a MOSIS 2μm n-well process. SPICE simulations of these designs are given. The circuit was laid out with MAGIC layout tools and fabricated through MOSIS. The chip was measured at PSU and Intel circuit labs and the experimental results show the correctness of the designs.
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Inoa, Ernesto. "A New High-Frequency Injection Method for Sensorless Control of Doubly-Fed Induction Machines." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338345508.
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Mbeutcha, France Gaspari. "A High-Side Wideband Current and Voltage Sensor for Radio-Frequency Power Amplifiers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17464/.
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The radio-frequency power amplifier (RF PA) is one of the critical elements within the wireless, as it is expected to provide a suitable output power with high efficiency and linearity. Improving the power efficiency of the RF power amplifier is a key challenge of the modern wireless communications, especially in the presence of wideband modulations signals. In fact, to achieve this goal, various techniques are investigated, including supply voltage modulation (e.g., envelope- tracking). In the supply-modulated Pas employed in modern telecom base stations, it is important to measure the dynamic current drained by the power amplifier and the dynamic voltage at the supply terminal.
This thesis project is focused on the design and realization of a high-side wideband (frequency response from dc up to > 100 MHz) voltage and current sensor suitable for supply-modulated power amplifiers. In order to be used with Gallium Nitride (GaN) PAs, the sensor must be able to withstand dynamic supply voltages up to 80 V and dynamic drain currents up to 2 A. The proposed current sensor is based on a shunt resistor approach, where the voltage drops across the resistor is firstly attenuated, and then amplified by a balanced differential circuit consisting of two cascaded stages. The voltage sensor consists of an operational amplifier configured as a buffer.
The first part of the project, developed at the DEI EDM Lab (UNIBO), was dedicated to the analysis of the sensing architecture, the simulation of the resulting circuit. The design of the board its characterization and board test were realized in at the Warsaw University of Technology in Poland.
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Toh, Kwang Yong Daniel. "Evaluation of surface current mapping performance by SeaSonde High Frequency radar through simulations." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FToh.pdf.
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Ackermann, Douglas Michael Jr. "REDUCTION OF THE ONSET RESPONSE IN HIGH FREQUENCY NERVE BLOCK." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1259791396.
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Badenhorst, J. "Metrology and modelling of high frequency probes." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/808.
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Jiang, Hui. "Audible noise reduction in the high frequency injection based sensorless torque control for EPS applications." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/29091/.
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This thesis has investigated the reduction of audible noise in low speed sensorless controlled drives for automotive electrical power steering (EPS) applications. The specific methods considered employ saliency tracking high frequency (hf) voltage injection in the machine's estimated d axis. In terms of the audible noise reduction, a novel random sinusoidal hf injection sensorless method has been proposed. The perceived audible noise due to the hf injection can be reduced by randomly distributing the injection frequencies around a centre frequency, such that it is perceived as a background hiss rather than the fixed tone heard with fixed hf injection methods. By analysing the A-weighting scales used to classify human perception of audible noise and frequency analysis of the recorded noise, an injection frequency of (lS00±328) Hz is found to have the lowest audible noise level compared to other random frequencies and other fixed frequencies methods. A 10 kHz square wave hf injection sensorless method has also been implemented. The frequency analysis of the recorded audible noise indicates that it also may be lower than for the fixed hf sinusoidal injection. In terms of control performance, sensorless torque control for these methods has been achieved from zero speed to ±240rpm with up to ±60A load (about 63% rated load). Similar position estimate quality has been demonstrated. Dynamic performance for a step change in torque current demand and for a speed reversal has been performed, and the random injection method with (1S00±328) Hz frequency has been found to be able to control a step change in torque demand current of 50A whilst for the 10kHz square wave injection method only a 40A step change can be achieved. On the other hand, the average position error after the speed transient has settled is less for the 10 kHz square ewave injection than for the random injection.
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鐘學仁 and Hok-Yan Chung. "Analysis of losses in power inductor for high-frequency switching power converters." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224313.
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Chung, Hok-Yan. "Analysis of losses in power inductor for high-frequency switching power converters." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23273318.
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Basset, Julien. "High frequency quantum noise of mesoscopic systems and current-phase relation of hybrid junctions." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00635825.
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Cette thèse est consacrée à l'étude de deux aspects de la physique mésoscopique que sont le bruit quantique haute fréquence et l'effet de proximité supraconducteur en se focalisant toutefois sur un système modèle: le nanotube de carbone.Ainsi la première partie de cette thèse est dédiée à la mesure de bruit quantique haute fréquence. Afin de mesurer ces fluctuations nous avons développé un système de détection "on-chip" original dans lequel la source de bruit et le détecteur, une jonction Supraconducteur/Isolant/Supraconducteur, sont couplés par un circuit résonant. Cela nous a permis dans un premier temps de mesurer le bruit à l'équilibre du résonateur. Son bruit comporte une forte asymétrie entre émission et absorption reliée aux fluctuations de point zéro. Une seconde étape a été de mesurer le bruit hors équilibre d'émission du passage tunnel de quasi-particules dans une jonction Josephson. Ce bruit comporte une forte dépendance en fréquence en accord avec les prédictions théoriques et nous a permis de valider le principe de détection. Finalement, nous avons pu mesurer le bruit associé au régime Kondo hors équilibre d'une boîte quantique à nanotube de carbone (énergie caractéristique kBTK avec TK la température Kondo). Ce bruit d'émission à kBTK~hν possède une forte singularité à la tension V=hν/e (ν étant la fréquence de mesure). Cette singularité est reliée aux résonances Kondo dans la densité d'états de la boîte associés aux niveaux de Fermi de chaque réservoir. A plus haute fréquence hν~3kBTK, la singularité disparaît, ce qui est compris par des effets de décohérence induits par la tension.Dans la seconde partie, nous avons développé une technique permettant de mesurer à la fois la relation courant/phase et la caractéristique courant/tension d'un lien faible séparant deux supraconducteurs. Nous avons ainsi caractérisé une jonction à base de nanotube de carbone au travers de laquelle une relation courant-phase modulable par une tension de grille a été observée. Cette relation courant/phase exhibe une forte anharmonicité lorsque le supercourant présente une relativement grande amplitude.
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Antaloae, C. C. "Feasibility of high frequency alternating current power distribution for the automobile auxiliary electrical system." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6792.
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This study investigates the feasibility and potential benefits of high frequency
alternating current (HFAC) for vehicle auxiliary electrical systems.
A 100Vrms, 50kHz sinusoidal AC bus is compared with 14V DC and 42V DC electrical
systems in terms of mass and energy efficiency. The investigation is focused on the four
main sub-systems of an on-board electrical network, namely: the power generation,
power distribution, power conversion and the electrical loads. In addition, a systemlevel
inquiry is conducted for the HFAC bus and a comparable 42V DC system.
A combination of computer simulation, analytical analysis and experimental work has
highlighted benefits for the HFAC power distribution sub-system and for low-torque
motor actuators. Specifically, the HFAC conductor mass is potentially 70% and 30%
lighter than comparable 14V DC and 42V DC cables, respectively. Also, the proposed
cable is expected to be at least 80% more energy efficient than the current DC
conductor technology. In addition, it was found that 400Hz AC machines can
successfully replace DC motor actuators with a rated torque of up to 2Nm. The former
are up to 100% more efficient and approximately 60% lighter and more compact than
the existing DC motors in vehicles. However, it is argued that the HFAC supply is not
feasible for high-torque motor actuators. This is because of the high energy losses and
increased machine torque ripple associated with the use of HFAC power.
The HFAC power conversion sub-system offers benefits in terms of simple power
converter structure and efficient HFAC/DC converters. However, a significant limitation
is the high power loss within HFAC/AC modules, which can be as high as 900W for a
2.4kW load with continuous operation. Similar restrictions are highlighted for the
HFAC power generation sub-system, where up to 400W is lost in a 4kW DC/HFAC
power module.
The conclusion of the present work is that the HFAC system offers mass and energy
efficiency benefits for the conventional vehicle by leveraging the use of compact lowtorque
motor actuators and lightweight wiring technology.
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Patsora, Iryna, Dmytro Tatarchuk, Henning Heuer, and Susanne Hillmann. "Study of a Particle Based Films Cure Process by High-Frequency Eddy Current Spectroscopy." Multidisciplinary Digital Publishing Institute, 2016. https://tud.qucosa.de/id/qucosa%3A30206.
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Particle-based films are today an important part of various designs and they are implemented in structures as conductive parts, i.e., conductive paste printing in the manufacture of Li-ion batteries, solar cells or resistive paste printing in IC. Recently, particle based films were also implemented in the 3D printing technique, and are particularly important for use in aircraft, wind power, and the automotive industry when incorporated onto the surface of composite structures for protection against damages caused by a lightning strike. A crucial issue for the lightning protection area is to realize films with high homogeneity of electrical resistance where an in-situ noninvasive method has to be elaborated for quality monitoring to avoid undesirable financial and time costs. In this work the drying process of particle based films was investigated by high-frequency eddy current (HFEC) spectroscopy in order to work out an automated in-situ quality monitoring method with a focus on the electrical resistance of the films. Different types of particle based films deposited on dielectric and carbon fiber reinforced plastic substrates were investigated in the present study and results show that the HFEC method offers a good opportunity to monitor the overall drying process of particle based films. Based on that, an algorithm was developed, allowing prediction of the final electrical resistance of the particle based films throughout the drying process, and was successfully implemented in a prototype system based on the EddyCus® HFEC device platform presented in this work. This prototype is the first solution for a portable system allowing HFEC measurement on huge and uneven surfaces.
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Patsora, Iryna, Dmytro Tatarchuk, Henning Heuer, and Susanne Hillmann. "Study of a Particle Based Films Cure Process by High-Frequency Eddy Current Spectroscopy." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-220609.
Full textAbstract:
Particle-based films are today an important part of various designs and they are implemented in structures as conductive parts, i.e., conductive paste printing in the manufacture of Li-ion batteries, solar cells or resistive paste printing in IC. Recently, particle based films were also implemented in the 3D printing technique, and are particularly important for use in aircraft, wind power, and the automotive industry when incorporated onto the surface of composite structures for protection against damages caused by a lightning strike. A crucial issue for the lightning protection area is to realize films with high homogeneity of electrical resistance where an in-situ noninvasive method has to be elaborated for quality monitoring to avoid undesirable financial and time costs. In this work the drying process of particle based films was investigated by high-frequency eddy current (HFEC) spectroscopy in order to work out an automated in-situ quality monitoring method with a focus on the electrical resistance of the films. Different types of particle based films deposited on dielectric and carbon fiber reinforced plastic substrates were investigated in the present study and results show that the HFEC method offers a good opportunity to monitor the overall drying process of particle based films. Based on that, an algorithm was developed, allowing prediction of the final electrical resistance of the particle based films throughout the drying process, and was successfully implemented in a prototype system based on the EddyCus® HFEC device platform presented in this work. This prototype is the first solution for a portable system allowing HFEC measurement on huge and uneven surfaces.
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Kanazawa, Kyoko. "Intracranially-recorded ictal direct current shifts may precede high frequency oscillations in human epilepsy." Kyoto University, 2014. http://hdl.handle.net/2433/193569.
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Dai, Jianxing. "Analysis and Design of a High-Frequency RC Oscillator Suitable for Mass Production." Thesis, Linköpings universitet, Elektroniska Kretsar och System, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138423.
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Oscillators are components providing clock signals. They are widely required by low-cost on-chip applications, such as biometric sensors and SoCs. As part of a sensor, a relaxation oscillator is implemented to provide a clock reference. Limited by the sensor application, a clock reference outside the sensor is not desired. An RC implementation of the oscillator has a balanced accuracy performance with low-cost advantage. Hence an RC relaxation oscillator is chosen to provide the clock inside the sensor. This thesis proposes a current mode relaxation oscillator to achieve low frequency standard deviation across different supplies, temperatures and process corners. A comparison between a given relaxation oscillator and the proposed design is made as well. All oscillators in this thesis use 0.18 μm technology and 1.8 V nominal supply. The proposed oscillator manages to achieve a frequency standard deviation across all PVT variations less than ±6.5% at 78.4 MHz output frequency with a power dissipation of 461.2 μW. The layout of the oscillator's core area takes up 0.003 mm2.
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Hickey, Kenneth J. "Ocean surface current estimation using a long-range, single-station, high-frequency ground wave radar." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0008/MQ42394.pdf.
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Chaaraoui, Jamal Abdullatif. "Effects of high frequency arcing in SFâ†6 puffer interrupters from low inductive current switching." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240706.
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Yan, Ning. "High-frequency Current-transformer Based Auxiliary Power Supply for SiC-based Medium Voltage Converter Systems." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/101507.
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Auxiliary power supply (APS) plays a key role in ensuring the safe operation of the main circuit elements including gate drivers, sensors, controllers, etc. in medium voltage (MV) silicon carbide (SiC)-based converter systems. Such a converter requires APS to have high insulation capability, low common-mode coupling capacitance (Ccm ), and high-power density. Furthermore, considering the lifetime and simplicity of the auxiliary power supply system design in the MV converter, partial discharge (PD) free and multi-load driving ability are the additional two factors that need to be addressed in the design. However, today’s state-of-the-art products have either low power rating or bulky designs, which does not satisfy the demands. To improve the current designs, this thesis presents a 1 MHz isolated APS design using gallium nitride (GaN) devices with MV insulation reinforcement.
By adopting LCCL-LC resonant topology, the proposed APS is able to supply multiple loads simultaneously and realize zero voltage switching (ZVS) at any load conditions. Since high reliability under faulty load conditions is also an important feature for APS in MV converter, the secondary side circuit of APS is designed as a regulated stage. To achieve MV insulation (> 20 kV) as well as low Ccm value (< 5 pF), a current-based transformer with a single turn structure using MV insulation wire is designed. Furthermore, by introducing different insulated materials and shielding structures, the APS is capable to achieve different partial discharge inception voltages (PDIV). In this thesis, the transformer design, resonant converter design, and insulation strategies will be detailly explained and verified by experiment results.
Overall, this proposed APS is capable to supply multiple loads simultaneously with a maximum power of 120 W for the sending side and 20 W for each receiving side in a compact form factor. ZVS can be realized regardless of load conditions. Based on different insulation materials, two different receiving sides were built. Both of them can achieve a breakdown voltage of over 20 kV. The air-insulated solution can achieve a PDIV of 6 kV with Ccm of 1.2 pF. The silicone-insulated solution can achieve a PDIV of 17 kV with Ccm of 3.9 pF.M.S.
Recently, 10 kV silicon carbide (SiC) MOSFET receives strong attention for medium voltage applications. Asit can switch at very high speed, e.g. > 50 V/ns, the converter system can operate at higher switching frequency condition with very small switching losses compared to silicon (Si) IGBT [8]. However, the fast dv/dt noise also creates the common mode current via coupling capacitors distributed inside the converter system, thereby introducing lots of electromagnetic interference (EMI) issues. Such issues typically occur within the gate driver power supplies due to the high dv/dt noises across the input and output of the supply. Therefore, the ultra-small coupling capacitor (<5 pF) of a gate driver power supply is strongly desired.[37] To satisfy the APS demands for high power modular converter system, a solution is proposed in this thesis. This work investigates the design of 1 MHz isolated APS using gallium nitride (GaN) devices with medium voltage insulation reinforcement. By increasing switching frequency, the overall converter size could be reduced dramatically. To achieve a low Ccm value and medium voltage insulation of the system, a current-based transformer with a single turn on the sending side is designed. By adopting LCCL-LC resonant topology, a current source is formed as the output of sending side circuity, so it can drive multiple loads importantly with a maximum of 120 W. At the same time, ZVS can use realized with different load conditions. The receiving side is a regulated stage, so the output voltage can be easily adjusted and it can operate in a load fault condition. Different insulation solutions will be introduced and their effect on Ccm will be discussed. To further reduce Ccm, shielding will be introduced. Overall, this proposed APS can achieve a breakdown voltage of over 20 kV and PDIV up to 16.6 kV with Ccm<5 pF. Besides, multi-load driving ability is able to achieve with a maximum of 120 W. ZVS can be realized. In the end, the experiment results will be provided.
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Jovanović, Milan Miodrag. "High-frequency off-line power conversion using quasi-resonant and multi-resonant techniques." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53542.
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Three recently-proposed power conversion technologies, the zero-current-switching (ZCS) and zero-voltage-switching (ZVS) quasi-resonant techniques, and the zero-voltage-switching multi-resonant technique, are evaluated for high-frequency, off-line applications. The study is performed with emphasis on the conversion-frequency range, efficiency, load range, input-voltage range, output power, dynamic response, and power density.
A comprehensive dc analysis of the half-wave and full-wave, half-bridge zero-current-switched quasi-resonant converters (QRCs) is presented. Design procedures for closed-loop design of the converters are also derived. The procedures are used to design and fabricate half-wave and full-wave converters operating in the low-megahertz range and experimentally assess their suitability for high-frequency, off-line power conversion.
The zero-voltage-switching technique is employed to further increase the conversion frequency. First, the half-bridge zero-voltage-switched quasi-resonant converter is analyzed and the trade-offs between its frequency range, load range, and efficiency are examined in detail. The multi-resonant-switch concept is applied to this converter to improve its characteristics, primarily its load range.
A complete dc analysis of the zero-voltage-switched multi-resonant converter (MRC) is given and the dc voltage-conversion-ratio characteristics are derived. A graphic design procedure for the converter is established and is used to build an experimental 100 W, off-line converter operating in the frequency range of 2 MHz to 8 MHz.
Finally, a comprehensive comparison of the QRCs and MRCs is performed and conditions where their applications appears most desirable are defined.Ph. D.
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Sun, Juanjuan. "Dynamic Performance Analyses of Current Sharing Control for DC/DC Converters." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28071.
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Paralleling operation of DC/DC converters is widely used in today's distributed power systems. To ensure balanced output currents among paralleled power modules, current sharing control is usually necessary.Active current sharing controls with current feedback mechanism are widely used in today's power supplies. However, the dynamic performance of these current sharing control schemes are not yet clearly explored. In this work, the dynamic current sharing performance is evaluated for paralleling systems with the output impedance approach. As the representative of the terminal characteristic of a power converter, output impedance is a powerful tool to study the dynamic response under load transients. The dynamic current sharing analyses are then conducted for three different active current sharing control structures and a comprehensive comparison among them helps the designer to choose appropriate controls for different applications.
On the other hand, high-frequency load transients are possible to happen for voltage regulators, which are the power supplies of microprocessors. In order to study the dynamic current sharing performance for a paralleling system when the perturbation frequency is higher than half of the switching frequency,the conventional output impedance concept needs to be extended. Due to the non-linear behavior of a switching modulator, the beat-frequency phenomenon could cause unexpected failure of a power supply when the perturbation frequency is close to the switching frequency. To address this issue, an unconventional multi-frequency model is proposed for high-frequency dynamic current sharing studies. With this model, the sideband components are possible to be included and the beat-frequency oscillations can be predicted. After that, the conventional impedance concept is expanded in the form of extended describing function, so that the terminal characteristics of paralleled converters are represented by a series of impedances. Besides the analyses, this work also proposed several solutions for the beat-frequency oscillation issue which are experimentally verified.
In summary, both low-frequency and high-frequency dynamic current sharing performances are studied in this dissertation. The output impedance concept and its extension in the form of extended describing function are utilized as the tools for researches. With these powerful tools, more insights are obtained to help better design of a paralleling system.Ph. D.
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Enriquez, Andres E. "An investigation of surface current patterns related to upwelling in Monterey Bay, using high frequency radar." Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1595.
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Approved for public release; distribution is unlimitedHigh Frequency (HF) radar backscatter instruments are under development and testing in the marine science and defense science communities for their abilities to remotely sense surface parameters in the coastal ocean over large areas. In the Navy context, the systems provide real-time mapping of ocean surface currents and waves critical to characterization and forecasting of the battlespace environment. In this study, HF radar, aircraft and satellite information were used to investigate and describe surface current in Monterey Bay, California, for a period of ten months, from June 01st, 2003 to March 31st, 2004. A network of five CODAR-type HF radar instruments measured hourly surface currents over the bay. The measurements were averaged over one-hour intervals and total surface velocities were mapped on a grid in the Monterey Bay. From the M1 Buoy located in the middle of the bay, an uninterrupted time series of wind intensity and direction was obtained for the whole period. Major upwelling events were observed during the period of June 14 to June 27, July 4 to July 19, August 8 to August 18 and other upwelling events were observed until late October. These periods of upwelling favorable winds are common during summer with durations of 10 to 20 days. Often they are interrupted by periods of relaxation state of just a few days as the winds veer to the northwest or northeast. Cyclonic circulation cells are developed on shore during upwelling conditions and an anticyclonic circulation in the middle of the bay is observed when the wind shifts to the southwest producing a strong flow out of the bay close to the coastline off Point Piǫs. Downwelling conditions are much common less than upwelling, with occurrences during winter and early fall storms with events lasting between two to five days. When the wind blows to the northeast with an intensity of 4 m/s or more for more than 12 hours, a well developed anticyclonic gyre forms in the middle of the bay. This is associated with a strong current, 35 to 40 cm/s, which flushes out in the southern part of the bay close to the coast off Point Piǫs. This flow reverses when the winds veer to the southwest and enter into the Bay with less intensity.
First Lieutenant, Chilean Navy
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Wright, George C. "Validation of high frequency radar used in ocean surface current mapping via in-situ drifting buoys." Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Sept/08Sep%5FWright.pdf.
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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, September 2008.Thesis Advisor(s): Paduan, Jeffrey D. "September 2008." Description based on title screen as viewed on November 4, 2008. Includes bibliographical references (p. 85-86). Also available in print.
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Enriquez, Andres. "An investigation of surface current patterns related to upwelling in Monterey Bay, using high frequency radar /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FEnriquez.pdf.
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Miller, Douglas P. "Introduction of a current waveform, waveshaping technique to limit conduction loss in high-frequency dc-dc converters suitable for space power." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237903.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Ewing, Gerald D. Second Reader: Michael, Sherif. "June 1990." DTIC Indentifier(s): Dc to dc converters, waveform generators, program listings, theses. Author(s) subject terms: dc-dc converter, quasi-resonant, Buck converter. Includes bibliographical references (p. 142-145). Also available in print.
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Teirikangas, M. (Merja). "Advanced 0–3 ceramic polymer composites for high frequency applications." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514296185.
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Abstract The main object of this thesis was to research injection mouldable 0–3 type ceramic polymer composites and their dielectric and magnetic properties in the GHz frequency region. The work has been divided into three sections. In the first section, two–phase ceramic polymer composites containing dielectric and magnetic fillers have been investigated and their characteristics analysed by reference to pre–existing mixing rules. The exploitation of these composites in miniaturizing devices, such as antennae, is presented and discussed. The second part describes three phase composites containing different nanosize additives (silver, silicon and alumina fibres) towards improving their dielectric properties. In the third part, some periodical and multilayer structures for ceramic polymer composite layers are proposed. In the case of two–phase ceramic polymer composites, with 37 vol.% of dielectric filler (Barium Strontium Titanate, BST) embedded into a thermoplastic polymer (ER140) matrix, the highest measured relative permittivity was 15 with a dielectric loss value of 0.008 at 1 GHz. With 43 vol.% of magnetic filler (hexaferrite, CO2Z) in ER182 matrix, the highest achieved relative permeability was 1.8 with a magnetic loss value of 0.077 at 1 GHz. Composites with Co2Z filler provide a 77% size reduction, and could thus be used advantageously in antennae. It was found that a 2–6 vol.% nanoaddition in BST–ER140 composites enhanced the relative permittivity drastically with only a minor effect on the dielectric losses. In particular, with only 2 vol.% addition of nanosize silver particles into the BST–ER140 composite, a 52% increase in the relative permittivity was obtained, with no significant change in the dielectric losses (tan δε = 0.004). Vertically and horizontally periodical dielectric composite structures comprising layers of different dielectric properties have been fabricated as well as multilayered structures containing dielectric and magnetic layers. The measurement results indicate that such multimaterial multilayer structures are good candidates for components with reduced dielectric and magnetic lossesTiivistelmä Väitöstyön tavoitteena oli tutkia ruiskuvalettavien 0–3 –liitännäisten keraami-polymeerikomposiittien ominaisuuksia erityisesti niiden GHz-taajuusalueen dielektristen ja magneettisten ominaisuuksien kannalta. Työ on jaettu kolmeen osaan. Ensimmäisessä osassa on tutkittu kaksikomponenttisia keraami-polymeerikomposiitteja, joissa täytemateriaali on joko dielektristä tai magneettista materiaalia. Komposiittien ominaisuuksia on analysoitu jo olemassa olevien seosmallinnuskaavojen avulla. Komposiittien hyödyntämistä erilaisten sovellusten, kuten antennien, minityrisoinnissa on myös käsitelty. Toinen osa käsittelee kolmikomponenttisia komposiitteja, joissa lisäaineena on käytetty pieniä määriä nanomateriaaleja (hopea- ja piipartikkelit sekä alumiinioksidikuitu) tarkoituksena parantaa komposiitin dielektrisiä. Kolmannessa osassa on tutkittu periodisia ja monikerroksisia keraami- polymeerikomposiittirakenteita rakenteita. Kaksikomponenttisten keraami-polymeerikomposiittien tapauksessa suurin permittiivisyyden arvo 15 dielektristen häviöiden ollessa 0.008 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa dielektristä täytemateriaalia (Barium Strontium Titanaatti, BST) oli 37 tilavuus-% termoplastisessa polymeerimatriisissa (ER140). Korkein saavutettu permeabiliteetin arvo 1.8 magneettisten häviöiden ollessa 0.077 (mittaustaajuus 1 GHz) saatiin komposiitille, jossa magneettista täyteainetta (hexaferriitti, Co2Z) oli 43 tilavuus-% ER182 -matriisissa. Tämä täyteaine mahdollistaa nykyistä jopa 77 % pienempien antennielementtien kehittämisen. Tukimuksessa todettiin 2–6 tilavuus-% nanomateriaalin lisäyksen BST-ER140 -komposiitteihin kasvattavan permittiivisyyttä merkittävästi juurikaan vaikuttamatta dielektrisiin häviöihin. Erityisesti 2 tilavuus-% hopeananopartikkeleiden lisäys BST-ER140 -komposiitteihin kasvatti permittiivisyyttä 52 % dielektristen häviöiden (tan δε = 0.004) kasvamatta. Työssä on myös tutkittu periodisesti (vertikaali ja horisontaali) koostettuja dielektrisiä komposiittirakenteita, jossa eri kerroksissa on erilaiset dielektriset ominaisuudet sekä monikerrosrakenteita, joissa vuorottelevat dielektriset ja magneettiset kerrokset. Mittaukset osoittivat, että monimateriaaliset monikerrosrakenteet ovat hyviä kandidaatteja komponentteihin, jotka vaativat pieniä dielektrisiä ja magneettisiä häviöitä
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Paolucci, Libero. "Development And Design Of PMSM Control Systems For Autonomous Underwater Vehicles." Doctoral thesis, 2018. http://hdl.handle.net/2158/1126999.
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Underwater vehicle propulsion is usually performed exploiting hydraulic or electrically operated propellers and hydraulic or electrically operated ducted jet propulsors. Electrical motor propulsion is in general the most flexible solution and it is growing in popularity because of its high efficiency both at high and low advance speed, quick and simple deployment, low costs and encumbrance. In the present work, the advantages of Permanent Magnet Synchronous Motors (PMSM) for underwater propulsion are highlighted. In particular sensorless control of PMSM permits reduced costs high reliability and performances. As a test case, the development of the MARTA AUV propulsion system has been developed. It is an Observation Class AUV for subsea archeology purposes. Several motor control techniques are presented with the relative test results. In particular, the author focused the research in the development of a technique able to perform a reliable rotational speed and torque estimation. This indeed would permit the exploitation of a vehicle dynamic model for the navigation algorithm. Pool and field tests for the identification of the dynamic parameters of the vehicle and of the propellers are presented. Finally, an off-line preliminary validation of a navigation algorithms based on a dynamic model is presented with encouraging results. In particular, the possibility to operate a position estimation of the vehicle less dependent on the on board sensors was highlighted. This involves obvious benefits in terms of cost reduction and reliability of the system.
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Lee, Shao-Hua, and 李少華. "Implementation of New High Frequency CMOS VCOs and Injection-Locked Frequency Dividers." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/48315090190911031295.
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博士國立臺灣科技大學
電子工程系
95
This thesis presents two voltage controlled oscillators and four injection locked frequency dividers, which are implemented by using standard TSMC and UMC 0.18um CMOS process respectively. In voltage controlled oscillators, the first oscillator is a differential complementary Colpitts VCO with back-gate coupling technique. The oscillator consists of two Colpitts VCOs and a transformer, it uses transformer coupling technique and differentially tuned MOS varactors for reducing phase noise. The second oscillator is a transformer coupling quadrature VCO with current reused technology. In injection locked frequency dividers (ILFDs), the first injection locked frequency divider is a current reused divide-by-2 injection locked frequency divider. It consists of two nMOS transistors stacked in series. The injection locking is performed by adding an injection nMOS between the differential outputs of the divider. The ILFD can operate with a lower power due to the reuse of dc current. The second injection locked frequency divider is a divide-by-4 injection locked frequency divider with a sub-harmonic mixer technique. A sub-harmonic mixer and a CMOS direct injection locked frequency divider are used to form the new divider. The third injection locked frequency divider is wide locking range divide-by-4 injection locked frequency divider. Decreasing the fixed capacitance of LC resonator and tuning both the varactor and switched inductor can be used to increase the locking range of divide-by-4 frequency divider. The fourth injection locked frequency divider is divide-by-4 ILFD with quadrature outputs. It consists of two LC-tank VCOs and two pairs of coupling transistors for coupling two VCOs to generate quadrature outputs.
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Du, Guan-Jie, and 杜冠頡. "Novel High Frequency Injection Method for Sensorless PMSM Drive." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/vzy948.
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碩士國立中央大學
電機工程學系
106
For Permanent-Magnet Synchronous Motor (PMSM), uses position sen-sors to get rotor position information, such as Hall sensors, encoders, or re-solvers, which increases cost and volume. In addition, the position sensor may also be affected by factors such as temperature, noise, fragile structure, or im-proper installation. To solve above mentioned problems, the sensorless control method be researched in recent years. The sensorless control method can reduce the system volume, cost, and increase system robustness. This thesis uses a high-frequency injection method for the rotor position estimation without a position sensor. Then the Field Oriented Control (FOC) is used to control the PMSM. For the rotor permanent magnet having the magnet-ic saliency, the rotor speed and position can be estimated by injecting a high-frequency signal method. This thesis improves the previous method of obtain the position error in the traditional high-frequency injection. It reduces algo-rithm complexity. It also can achieve effectiveness as the traditional method.
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Huang, Bi-Chou, and 黃必超. "A 24-GHz Current-Mode Injection-Locked Frequency Divider with Voltage Control Oscillator." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/52191665954139415124.
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碩士國立交通大學
電機學院IC設計產業專班
95
A prototype of current-mode injection-locked frequency divider (ILFD) embodying the design principles and the new circuit configurations which achieve lower phase noise, wider locking range, and lower power dissipation is designed, layout and fabricated in TSMC (Taiwan Semiconductor Manufacturing Company Ltd.) 0.13 um CMOS RF technology. The voltage controlled oscillator (VCO) using LC-tank architecture is designed to operate at a fundamental frequency of 24GHz and it is estimated to deliver -4.16dBm of output power at 24 GHz in order to drive the frequency divider while consuming about 4.25 mA of DC current from a 0.8-V supply. To demonstrate the proposed concept, a fully integrated CMOS current-mode ILFD and current-mode flip-flop based frequency divider with a voltage controlled oscillator (VCO) to operate on 24-GHz carrier with low phase noise was designed while dissipating 8-mW from a super low voltage 0.8-V supply. This current-mode ILFD achieves 2-GHz wide locking range and -106dBc/Hz phase noise at 1-kHz offset while dissipating 0.6-mW. In the measurement results, the proposed model of current-mode ILFD, and derive analytical expressions of relating locking band are successful implement. The model described unifies the treatment of injection-locked and regenerative systems. It provides useful guidelines to improve the locking range. Illustrative measurement results are close to correspondence between theory, simulation, and measurement.