No description available.

With the development and use of Silicon-Carbide [Silicon-Carbide (SiC)] devices come a host of advantages, including higher switching frequency, improved thermal performance, and higher voltage rating. This higher switching frequency can reduce the size of the con- verter system, but is typically associated with higher dv/dt voltage slew rates that further increase electromagnetic interference (EMI) related phenomena. Conventional gate-drivers are very limited in the way that they can control this high dv/dt, and this leads to the use of active gate-drivers. This thesis will explore the use of an active voltage-controlled gate-driver for SiC devices, utilizing transiently a voltage closer to the Miller plateau than the nominal turn-on and turn-off voltage to introduce control over the switching transient. Various ap- plied voltages, and voltage sequences will be evaluated to determine their effectiveness for controlling dv/dt and their impact on switching loss. Through this work, a better under- standing of the advantages and drawbacks of an active gate-driver can be found. The main result from this work is the effective reduction in the dv/dt generated by MOSFET devices, which was attained at a lower switching loss penalty compared to conventional resistive gate-drivers operating at similar dv/dt rates. Simulation and experimental results obtained with a prototype active gate-driver circuitry were used for this evaluation. / Master of Science / Within power electronic systems such as an inverter used to connect solar panels to the grid, are electrically controlled switches. These switches traditionally have been made of Silicon (Si) which imposed limitations on how fast they could transition from off to on, and vice versa, they also could only switch a relatively small number of times per second. However, a new generation of devices made from a silicon carbide material are being increasingly adopted, some key advantages of these new devices include much higher number of times to switch per second, and faster transitions from off-on and on-off. The trade-off that comes with this faster operation is an increase in the electromagnetic noise generated by these switches, among other issues. This work looks to explore a more unique method of controlling the turn-on and turn-off of these new switches and evaluating its impact on the noise generated and the losses during switching.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Silicon Carbide as a wide-bandgap semiconductor has several physical and electrical advantages over Silicon for high voltage and high frequency applications. SiC as a MOSFET device has a lot of great characteristics like lower on-resistance and low input capacitances. However, due to its high switching capabilities, SiC MOSFET-based converter circuits experience higher dv/dt and di/dt transients and are therefore more susceptible to parasitic elements. This thesis investigates the interaction of the parasitic gate inductance and resistance on the switching behaviour of SiC DMOSFET (planar) and UMOSFET (trench). To examine this, a double pulse test (DPT) setup was utilised both in simulation and experimentally. The influence of the gate inductance and resistance on the oscillation behaviour in the VGS during the miller period was found to be dependent on the condition of the upper device. Furthermore, the upper device was discovered to have a high impact on the oscillations in the VGS via its source inductance. The gate inductance showed a mixed impact on IDS and VDS overshoot, with IDS overshoot reducing with increasing gate inductance and the reverse case for VDS. The gate resistance, however, showed a consistent impact on both IDS and VDS overshoot, with both reducing with increasing gate resistance. These results ultimately point to the impact of di/dt and dv/dt transients. An interesting result observed on these root causes showed that in the DPT arrangement used, lower test current levels may have a more significant impact on the oscillations in the VGS than higher test current when varying the test currents, with 20 A having the highest impact on the oscillations in simulations and 15 A having the highest impact in experimental verification. On the switching energy, the gate inductance was not shown to have a significant impact on switching losses while the gate resistance had a much more significant impact on the switching losses. / Kiselkarbid som halvledare med brett bandgap har flera fysiska och elektriska fördelar jämfört med kisel för högspännings- och högfrekvensapplikationer. SiC som en MOSFET-enhet har många fantastiska egenskaper som lägre resistans och låga ingångskapacitanser. Men på grund av dess höga omkopplingsförmåga upplever SiC MOSFET-baserade omvandlarkretsar högre dv/dt och di/dt transienter och är därför mer mottagliga för parasitiska element. Denna avhandling undersöker interaktionen mellan gate-drivkretsens parasitära induktans och resistans på kopplingsbeteendet på SiC DMOSFET (plan) och UMOSFET (trench). För att undersöka detta användes en dubbelpulstest (DPT) mätuppställning både i simulering och experimentellt. Inverkan av grindinduktansen och motståndet på svängningsbeteendet i VGS under Millerperioden visade sig vara beroende av den övre anordningens tillstånd. Vidare upptäcktes att den övre anordningen hade en hög inverkan på svängningarna i VGS via dess parasitiska induktans. Gate-induktansen visade en blandad inverkan på IDS- och VDS-översvängning, med IDS-översvängning som minskade med ökande gateinduktans och det omvända fallet för VDS. Gatemotståndet visade dock en konsekvent inverkan på både IDS- och VDS-överskridningar, med båda minskande med ökande gatemotstånd. Dessa resultat pekar slutligen på inverkan av di/dt- och dv/dt-transienter. Ett intressant resultat som observerats på dessa grundorsaker visade att i det använda DPT-arrangemanget kan lägre testströmnivåer ha mer signifikant inverkan på svängningarna i VGS än högre testström vid variation av testströmmarna, med 20 A som har den högsta inverkan på svängningarna i simuleringar och 15 A som har störst effekt vid experimentell verifiering. På omkopplingsenergin visades inte grindinduktansen ha någon signifikant inverkan på omkopplingsförlusterna medan grindresistansen hade mycket mer betydande inverkan på omkopplingsförlusterna.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Ce projet fait l'objet d'une collaboration entre l'équipe EPI du laboratoire SATIE de l'ENS Cachan, le laboratoire LAPLACE et ALSTOM Transport dans le cadre du projet ANR " CONCIGI HT ". Les recherches dans le domaine du ferroviaire visent à réduire toujours plus la taille et le poids de la chaine de traction. Aujourd'hui, la volonté de poursuivre la réduction des temps de parcours est complétée par le souhait de diminuer la puissance consommée, ceci ayant des conséquences importantes sur la conception des chaines de traction. L'objectif de ce projet est de remplacer certaines parties de la chaine de puissance d'une locomotive par des systèmes permettant de diminuer de 30% leur encombrement, donc de diminuer jusqu'à 8,5 % l'énergie électrique consommée et augmenter le nombre de passagers transportés. Le travail présenté dans cette thèse porte sur le dimensionnement et l'étude de l'alimentation des allumeurs de semi-conducteurs SiC HT (pouvant atteindre un transitoire de 10 kV). La particularité de ces semi-conducteurs est leur application : ils constituent des convertisseurs multi-niveaux dont la fonction est de remplacer les transformateurs 25 kV/3 kV-50 Hz actuellement utilisés pour la traction ferroviaire. La principale contrainte porte donc sur la tenue diélectrique qui atteint un maximum de 60 kV liée aux transitoires présents sur la caténaire. Une alimentation à double isolation galvanique (DGIT-Double Galvanic Insulation Transformer) a donc été développée afin de répondre à la nécessité de double tenue diélectrique (10 kV et 60 kV). Dans un premier temps une structure permettant la double isolation galvanique a été développée avec l'objectif de réduire au maximum sa taille et son poids. Sa disposition spatiale et sa géométrique ont également été pris en considération (ainsi que de nombreux paramètre à la fois pertinents et contradictoires). Ceci afin d'obtenir le système optimal et une répartition des capacités de mode commun et différentiel respectant la forte tenue diélectrique. Dans un second temps une étude de l'alimentation adaptée au DGIT a été réalisée et testée. L'association du DGIT qui est un élément très inductif, de la charge qui est un driver à faible puissance et de l'aspect multi-niveau implique un fonctionnement atypique. Pour chacune de ces parties, une étude structurelle, fréquentielle et électrique a été réalisée afin d'obtenir un dispositif optimal du point de vue du volume, du poids et des pertes, tout en respectant la principale contrainte de la tenue à la THT (Très Haute Tension). Enfin, dans un troisième temps nous avons étudié la possibilité de remplacer les fibres optiques utilisées de nos jours pour la commande des allumeurs par un système basé sur la transmission par radio fréquence.

No description available.

This work investigates the voltage scaling feasibility of several low voltage SiC MOSFET modules operated as a single series-connected switch using active gate control. Both multilevel and two-level topologies are capable of achieving higher blocking voltages in high-power converter applications. Compared to multilevel topologies, two-level switching topologies are of interest due to less complex circuitry, higher density, and simpler control techniques. In this work, to balance the voltage between series-connected MOSFETs, device turn-off speeds are dynamically controlled on active gate-drivers using active gate control. The implementation of the active gate control technique (specifically, turn-off dv/dt control) is described in this thesis. Experimental results of the voltage balancing behavior across eight 1.7 kV rated SiC MOSFET devices in series (6 kV total dc bus voltage) with the selected active dv/dt control scheme are demonstrated. Finally, the voltage balancing performance and switching behavior of series-connected SiC MOSFET devices are discussed. / Master of Science / According to ABB, 40% of the world's power demand is supplied by electrical energy. Specifically, in 2018, the world's electrical demand has grown by 4% since 2010. The growing need for electric energy makes it increasingly essential for systems that can efficiently and reliably convert and control energy levels for various end applications, such as electric motors, electric vehicles, data centers, and renewable energy systems. Power electronics are systems by which electrical energy is converted to different levels of power (voltage and current) depending on the end application. The use of power electronics systems is critical for controlling the flow of electrical energy in all applications of electric energy generation, transmission, and distribution. Advances in power electronics technologies, such as new control techniques and manufacturability of power semiconductor devices, are enabling improvements to the overall performance of electrical energy conversion systems. Power semiconductor devices, which are used as switches or rectifiers in various power electronic converters, are a critical building block of power electronic systems. In order to enable higher output power capability for converter systems, power semiconductor switches are required to sustain higher levels of voltage and current. Wide bandgap semiconductor devices are a particular new category of power semiconductors that have superior material properties compared to traditional devices such as Silicon (Si) Insulated-Gate Bipolar Junction Transistors (IGBTs). In particular, wide bandgap devices such as Silicon Carbide (SiC) Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) have better ruggedness and thermal capabilities. These properties provide wide bandgap semiconductor devices to operate at higher temperatures and switching frequencies, which is beneficial for maximizing the overall efficiency and volume of power electronic converters. This work investigates a method of scaling up voltage in particular for medium-voltage power conversion, which can be applied for a variety of application areas. SiC MOSFET devices are becoming more attractive for utilization in medium-voltage high-power converter systems due to the need to further improve the efficiency and density of these systems. Rather than using individual high voltage rated semiconductor devices, this thesis demonstrates the effectiveness of using several low voltage rated semiconductor devices connected in series in order to operate them as a single switch. Using low voltage devices as a single series-connected switch rather than a using single high voltage switch can lead to achieving a lower total on-state resistance, expectedly maximizing the overall efficiency of converter systems for which the series-connected semiconductor switches would be applied. In particular, this thesis focuses on the implementation of a newer approach of compensating for the natural unbalance in voltage between series-connected devices. An active gate control method is used for monitoring and regulating the switching speed of several devices operated in series in this work. The objective of this thesis is to investigate the feasibility of this method in order to achieve up to 6 kV total dc bus voltage using eight series-connected SiC MOSFET devices.

No description available.

In the search for green energy to combat climatechange, a shift from conventional energy sources such as coal,oil, and nuclear towards Renewable Energy Sources (RES) isneeded. This shift poses a threat to the stability of the powergrids as RES do not contribute with rotating mass in the system.A lack of rotating mass, or in other words inertia, jeopardizesthe ability of power systems to counteract large disturbances.Frequency Containment Reserves (FCR) units are responsiblefor controlling the frequency in power systems by regulatingthe balance between the generated and consumed power. If thefrequency deviates outside of the defined range from the nominalvalue, it can lead to system separation, blackouts, and systemequipment damage. The frequency deviations are faster in lowinertia systems, making it more difficult for FCR to keep thefrequency within accepted ranges. Hydro turbines are often usedas FCR units, but additional means of support could be neededfor low inertia systems. Viable support could be battery systems.This project investigates the change towards low inertia and thepossible implementation of a battery system as fast step-wisepower support with a frequency trigger. The investigation is donethrough case studies of simulated system models in Matlab andSimulink. / I jakten på grön energi för att bekämpa klimatförändringarna behövs en övergång från konventionella energikällor som kol, olja och kärnkraft mot förnyelsebara energikällor. Denna övergång utgör ett hot mot kraftnätens stabilitet då förnyelsebara energikällor inte bidrar med roterande massa. Brist på roterande massa eller med andra ord tröghet äventyrar kraftsystemens förmåga att motverka stora störningar. Frequency Containment Reserves (FCR) är system som aktivt arbetar med att styra frekvensen i kraftsystemet genom att reglera balansen mellan den producerade och konsumerade effekten. Om detta misslyckas och frekvensen avviker för mycket från den nominella frekvensen kan detta leda till systemseparation, strömavbrott eller skada hos systemkomponenter. I ett system med låg tröghet blir frekvensavvikelserna snabbare. Detta gör det svårare att använda sig av FCR för att hålla frekvensen inom accepterade intervall. Vattenkraftverk används ofta som FCR enheter, men för system med låg tröghet kan ytterliggare stöd behövas. Ett möjligt effektstöd kan vara batterisystem. Detta projekt undersöker förändringen till lägre tröghet i ett kraftsystem och möjlig implementering av ett batterisystem med ett snabbt stegsvar för effektstöd, vilket aktiveras vid en förbestämd frekvens. Undersökningen görs genom studier av specifika fall med en linjäriserad modell av ett kraftsystemet, lerade i Matlab och Simulink. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm