System and component design and test of a 10 hp, 18,000 rpm AC dynamometer utilizing a high frequency AC voltage link, part 1

Hard and soft switching test results conducted with one of the samples of first generation MOS-controlled thyristor (MCTs) and similar test results with several different samples of second generation MCT's are reported. A simple chopper circuit is used to investigate the basic switching characteristics of MCT under hard switching and various types of resonant circuits are used to determine soft switching characteristics of MCT under both zero voltage and zero current switching. Next, operation principles of a pulse density modulated converter (PDMC) for three phase (3F) to 3F two-step power conversion via parallel resonant high frequency (HF) AC link are reviewed. The details for the selection of power switches and other power components required for the construction of the power circuit for the second generation 3F to 3F converter system are discussed. The problems encountered in the first generation system are considered. Design and performance of the first generation 3F to 3F power converter system and field oriented induction moter drive based upon a 3 kVA, 20 kHz parallel resonant HF AC link are described. Low harmonic current at the input and output, unity power factor operation of input, and bidirectional flow capability of the system are shown via both computer and experimental results. The work completed on the construction and testing of the second generation converter and field oriented induction motor drive based upon specifications for a 10 hp squirrel cage dynamometer and a 20 kHz parallel resonant HF AC link is discussed. The induction machine is designed to deliver 10 hp or 7.46 kW when operated as an AC-dynamo with power fed back to the source through the converter. Results presented reveal that the proposed power level requires additional energy storage elements to overcome difficulties with a peak link voltage variation problem that limits reaching to the desired power level. The power level test of the second generation converter after the addition of extra energy storage elements to the HF link are described. The importance of the source voltage level to achieve a better current regulation for the source side PDMC is also briefly discussed. The power levels achieved in the motoring mode of operation show that the proposed power levels achieved in the generating mode of operation can also be easily achieved provided that no mechanical speed limitation were present to drive the induction machine at the proposed power level

Soft switching techniques for multilevel inverters

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica

Design of the tests for the Passive Protection Circuit of the High Voltage Radio Frequency Test Facility

ITER ("La Via" in latino) è un ambizioso progetto internazionale che mira a dimostrare la fattibilità della fusione come fonte di energia su larga scala e senza emissioni di carbonio. ITER è progettato per produrre circa 500 MW di potenza dalla reazione di fusione con 50 MW di potenza in ingresso per il riscaldamento del plasma. La potenza di ingresso è fornita attraverso tre diversi sistemi di riscaldamento (H&CD): riscaldamento a risonanza elettronica ciclotronica (ECRH), riscaldamento a risonanza ionica ciclotronica (ICRH) e riscaldamento tramite l’iniezione di fasci di neutri (NBI). In ITER è prevista la presenza di due NBI, ciascuno in grado di iniettare nel plasma un fascio di particelle neutre con un potenza di 16,5 MW per un'ora. Tale fascio viene ottenuto estraendo e accelerando un fascio di ioni negativi di idrogeno e deuterio fino a 1 MeV e neutralizzandolo prima di entrare nel plasma. Tali requisiti non sono mai stati raggiunti sperimentalmente. Per questo motivo, è stata sviluppata una struttura di test dedicata, NBTF (Neutral Beam Test Facility), per testare e ottimizzare il NBI di ITER attraverso due diversi esperimenti: SPIDER (la sorgente di ioni negativi a radiofrequenza a grandezza naturale di ITER) e MITICA (il prototipo a grandezza naturale dell'iniettore di fasci neutri di ITER). InSPIDER, il plasma viene generato all'interno di quattro coppie di driver accoppiate induttivamente con il plasma, ciascuna alimentata da un generatore a radiofrequenza in grado di fornire 200 kW a 1 MHz. Inoltre la sorgente di SPIDER è installata in una camera da vuoto, così i driver RF e i relativi circuiti, montati sul retro della sorgente, si trovano ad operare alla pressione di fondo residua. Tali parti si trovano quindi sottoposte a campi elettrici in vuoto ad alta intensità che possono portare alla generazione di archi elettrici che vanno evitati altrimenti la sorgente si potrebbe danneggiare. Per questo è stata sviluppata l’High Voltage Radio Frequency Test Facility (HVRFTF) con lo scopo di essere un esperimento accessibile, dedicato a verificare la tenuta della tensione di mock-up dei circuiti a radiofrequenza e dei componenti principali installati all'interno di SPIDER. Tale facility è in grado di riprodurre le condizioni operative dei driver di SPIDER: l'alta tensione viene prodotta utilizzando un circuito risonante ad alto fattore di qualità, mentre i componenti in prova sono installati all'interno di un vessel sotto vuoto che può essere riempito con differenti gas e alla pressione voluta. Differenti geometrie di mock-up generano campi elettrici diversi e vengono alimentati con una tensione RF crescente fino alla formazione di un arco elettrico, che rappresenta il limite da non superare in SPIDER per evitare danni.. Gli effetti di tale arco, tuttavia, possono causare danni all'amplificatore che alimenta il circuito risonante. Inoltre, il circuito risonante può essere soggetto a guasti dell'isolamento che possono anch’essi causare danni. Questo perchè sia l'arco sui mock-up che i guasti relativi all’isolamento sono caratterizzati da transitori veloci con picchi di tensione e corrente particolarmente elevati. Per limitare i danni di tali transitori è stato progettato un circuito di protezione passivo (PPC) in grado di dissipare l'energia immagazzinata nel circuito risonante e limitare eventuali sovratensioni che si dovessereo presentare sullo stadio di uscita dell'amplificatore. Tuttavia, prima di affidarsi alla protezione, è necessario verificarne l'efficacia con test dedicati. Lo scopo di questa tesi è quello di progettare le procedure per testare il circuito di protezione passivo.ITER (“The Way” in latin) is an ambitious international project aiming to demonstrate the feasibility of fusion as large-scale and carbon-free energy source. ITER is designed to produce around 500 MW of fusion power with 50 MW of input power for heating the plasma. This input power is produced by means of three different Heating and Current Drive (H&CD) systems: Electron Cyclotron Resonance Heating (ECRH), Ion Cyclotron Resonance Heating (ICRH) and Neutral Beam Injector (NBI). In ITER, two NBI are foreseen, each capable of injecting neutral particles beam of 16.5 MW power inside the plasma for an hour, by extracting and accelerating a negative beam of hydrogen and deuterium ions up to 1 MeV of energy and neutralizing it before entering the plasma. These requirements have never been reached experimentally before. For this reason, a dedicated test facility, NBTF (Neutral Beam Test Facility), was developed to test and optimize the ITER NBI by means of two separate experiments: SPIDER (the ITER-scale radio frequency negative ion source) and MITICA (the full-scale prototype of the ITER heating neutral beam injector). In SPIDER, the plasma is generated inside four couples of inductively coupled plasma drivers, each powered by a radio frequency generator rated to provide 200 kW at 1 MHz. SPIDER beam source is fully installed in vacuum and thus the RF drivers and the related circuits, on the backside of the beam source, operates at the residual background pressure. Moreover, during SPIDER operation, the drivers and other components of the ion source are subjected to high intensity electric fields in vacuum which can lead to the generation of electric arcs. Consequently, the High Voltage Radio Frequency Test Facility (HVRFTF) was developed as a dedicated test facility to verify the voltage hold off on mock-ups of the radio frequency circuits and special components installed inside the SPIDER ion source. This facility is able to reproduce the operating conditions of the drivers: the high voltage is produced exploiting a resonant circuit with high quality factor, while the components under test components are installed within a vacuum vessel filled with the desired gasses and pressure. Different mock-ups geometries generate different electric fields and are supplied with an increasing RF voltage up to the formation of an electric arc, that is the limit not to exceed with SPIDER to avoid damages. The effects of this arc, however, can lead to damages to the amplifier supplying the resonant circuit. Moreover, the resonant circuit is subjected to insulation failures that can cause damages too. Both the arc on the device under test and the insulation failures are characterized by fast transients with relatively high voltage and current peaks. A Passive Protection Circuit (PPC) was developed to dissipate the energy stored in the resonant circuit and to limit possible overvoltage at the amplifier output. Nevertheless, before relying on the protection, it is necessary to verify its effectiveness with dedicated tests. The aim of this thesis is to design the procedures to test the passive protection circuit

Miniaturized Ultraviolet Imager High Voltage Power Supply

Sending satellites into orbit becomes exponentially more expensive with weight and size, so designing high-voltage DC-DC converters that can achieve kilovolt level outputs in a small form factor is crucial to reducing costs. The Miniaturized Ultraviolet Imager (MUVI) aims to monitor Earth’s ionosphere and report weather patterns to climate scientists within a 2U cube satellite footprint. The imaging equipment consists of a microchannel plate and phosphor screen that require 2.5kV and 5.5kV respectively at microamp level currents. This report explains the implementation of a high voltage boost cascaded flyback converter to meet all of the MUVI satellite output voltage requirements. The small mechanical footprint of a cube satellite severely limits board size and component heights. This design further expands the power electronics field and provides inspiration for future space-rated voltage converters in small form factors. The results from circuit simulations validated the design as a viable solution for MUVI’s imaging equipment. A boost-flyback converter can achieve the required high voltage DC output while remaining within the 7ppm ripple specification. This report summarizes all of the circuit simulation results for both the power stage and analog circuitry that monitor and control the output voltage. The analog circuitry was hardware tested and validated for the monitoring and control signals. The power stage testing is scheduled for the Summer of 2021 so those results are not included in this report

Design and Modelling of a Bidirectional DC-DC Converter based on Full Bridge Current Doubler Topology for Aeronautical Applications

This project falls within the framework of the research about More Electric Aircraft (MEA) concept, which is the target of the current designs. In this context, electrical system is being reinforced as one of the main power systems. Electrical power level and voltage level transmission are increasing –the last one is tending to High Voltage Direct Current (HVDC) level– and requirements of generation, distribution, management and control of this kind of power are becoming more and more challenging. Within electrical system, power converters are responsible for electrical power transmission. Moreover, they must fulfil aeronautical standards in respect of on-board electrical and electronic systems. The precise aim of this project is to study suitable topologies for DC-DC bidirectional and isolated power converters within defined framework. Many industries, as aeronautical or automotive, request them with better features –for instance, power density and e ciency are critical KPI in aeronautical industry–. After a review of main power circuits that could fulfil specifications for these applications, a promising topology will be analysed from a numerical point of view. Particularly, Bidirectional Current Doubler is the topology subject of study. Its working principle will be analysed under certain operating range domain. Simulation models will be developed to asses topology performance in such operating domain. By knowing currents and voltages on ideal elements, a more realistic components selection will be carried out, particularly as far as MOSFETs concerns. Finally, regarding a more little bit accurate model, e ciency will be calculated in terms of input and output power.Universidad de Sevilla. Máster en Ingeniería Aeronáutic