Nowadays, major public concern is concentrated on reducing the usage of fossil fuels and reducing emissions of CO₂ by different energy advancement. Electric vehicle technology presents extremely effective way of reducing carbon emissions and paves the way of having sustainable and renewable energy future. In order to wear the cost of electric vehicles down, batteries have to be improved as well as higher power density and high reliability has to be achieved. This research work mainly focuses on achieving higher power density and higher reliability of the inverter stage by utilizing wide-bandgap SiC MOSFET semiconductor devices in electric vehicle application. In order to achieve higher reliability of the inverter stage, high bandwidth, high performance Rogowski coil switch current sensors are employed. These sensor were embedded on the PCB and integrated on the gate driver. High bandwidth switch current sensor measurement is used for fast short-circuit detection and protection of the SiC MOSFET semiconductor switches. Furthermore, comparison with conventional detection and protection method used in automotive IGBT applications is shown where novel protection showed superior performance. This thesis also shows principle of how to obtain phase currents of the system using Rogowski coil switch current sensor measurements. Digital reconstruction principle is employed to obtain the phase currents. Accurate and linear current sensor is achieved. By successfully realizing this integrated phase current measurement on the gate driver, elimination of the commercial current sensors from the system is possible. By eliminating existing phase current sensors, higher power density could be achieved. Sensor is evaluated in both continuous and discontinuous PWM schemes. / Master of Science / Together with renewable sources, electric vehicle will play an important role as a part of sustainable and renewable energy future by significantly reducing emissions of CO₂ into the atmosphere. In order to make electric cars more acceptable and accessible and make a significant impact on the environment, cost must be lowered down. To wear the cost of the electric vehicles down, powertrain of the car must be significantly improved and made smaller as well as lighter. This thesis mainly focuses on improving the reliability of the motor driving stage by implementing novel protection during fault periods such as short-circuit event. Furthermore, this novel protection allows current sensing that is crucial for motor control during normal operation periods. This will enable more compact motor driving stage since existing current sensing elements can be eliminated.

This work deals with design of battery management system. Requirements for battery management system and its conception is discussed in the first part of the work. System is able to disconnect load or charger from battery using MOS-FET transistors. It measures battery cell's voltages and is capable of passive balancing. Microcontroller is used for data processing and system control. Schematics, printed circuit board layout and control algorithm was designed. Prototype of the battery management system was then manufactured and tested.

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Actuellement, il y a une baisse du prix des ressources énergétiques distribuées, en particulier l'énergie solaire photovoltaïque, conduisant à la croissance significative de leur capacité d'installation dans de nombreux pays. D'autre part, les politiques encourageant l'efficacité énergétique ont favorisé le développement de charges DC dans les zones domestiques, telles que l'éclairage LED, les ordinateurs,, les téléphones, les téléviseurs, les moteurs DC efficaces et les véhicules électriques. Grace à ce changement, le système de distribution de microgrid DC devient plus attractive que le système de distribution à courant alternatif traditionnel. Les avantages principaux du microgrid DC sont l'efficacité énergétique plus élevée, plus facile à intégrer avec les sources d'énergie distribuées et le système de stockage. Alors que de nombreuses recherches se concentrent sur les stratégies de contrôle et la gestion de l'énergie dans le microgrid DC, sa protection reçoit une attention insuffisante et un manque de réglementation et d'expériences. La protection dans les réseaux DC est plus difficile que dans le réseau AC en raison de l'arc continu, de la valeur plus élevée du courant de courtcircuit et du taux de défaut de montée. En outre, dans les réseaux distribués à courant continu sont composés de nombreux dispositifs de commutation électroniques et semi-conducteurs, qui ne supportent le courant de défaut que quelques dizaines de microsecondes. Les disjoncteurs mécaniques, qui ont un temps de réponse de quelques dizaines de millisecondes, ne semblent pas satisfaire aux exigences de sécurité du microréseau à courant continu. L'absence d'un dispositif de protection efficace constitue un obstacle au développement du microgrid DC dans le système distribué. Cette thèse propose un disjoncteur DC auto-alimenté à courant continu utilisant normalement JFET SiC, qui offre un excellent dispositif de protection pour les microgrids DC grâce à son temps de réponse rapide et ses faibles pertes à l'état passant. La conception du disjoncteur DC à semi-conducteurs vise à répondre à deux objectifs: temps de réponse rapide et fiabilité. Les spécifications conçues et les énergies critiques qui entraînent la destruction du disjoncteur sont identifiées sur la base des résultats mesurés d'un JFET populaire dans le commerce. Un pilote de protection très rapide et fiable basé sur une topologie à convertisseur flyback avant est utilisé pour générer une tension négative suffisante pour tourner et maintenir le JFET SiC. Le convertisseur sera activé chaque fois que le disjoncteur détecte des défauts de court-circuit en détectant la tension de drain-source de JFET et crée une tension négative s'applique à la porte de JFET. Pour éviter une défaillance de la porte par surtension au niveau de la grille du JFET, la tension de sortie du convertisseur de retour vers l'avant est régulée à l'aide de la mesure coté primaire. Les résultats expérimentaux sur le prototype du disjoncteur DC ont validé les principes de fonctionnement proposés et ont confirmé que le disjoncteur DC à semi-conducteurs proposé peut interrompre le défaut en 3 μs. D'un autre côté, un modèle du JFET normalement activé dans l'environnement Matlab/Simulink est construit pour étudier les comportements du SSCB pendant une durée de court-circuit. L'accord entre la simulation et les résultats expérimentaux confirment que ce modèle JFET peut être utilisé pour simuler le fonctionnement d'un disjoncteur DC et dans l'étude du fonctionnement du microgrid DC pendant le processus de défaut et de compensation / Currently, there is a drop in the price of distributed energy resources, especially solar PVs, which leads to a significant growth of the installed capacities in many countries. On the other hand, policies encouraging energy efficiency have promoted the development of DC loads in domestic areas, such as LEDs lighting, computers, telephones, televisions, efficient DC motors and electric vehicles. Corresponding to these changes in sources and loads, DC microgrid distribution system becomes more attractive than the traditional AC distribution system. The main advantages of the DC microgrid are higher energy efficiency, easier in integrating with distributed energy sources and storage systems. While many studies concentrate on the control strategies and energy management in the DC microgrid, the protection still receives inadequate attention and lack of regulations and experiences. Protection in DC grids is more complex than AC grids due to the continuous arc, higher short circuit current value and fault rate of rising. Furthermore, the DC distributed grids are composed of many electronic and semiconductor switching devices, which only sustain the fault currents of some tens of microseconds. Mechanical circuit breakers, which have a response time in tens of milliseconds, seem not to meet the safety requirement of DC microgrids. The lack of effective protection devices is a barrier to the development of DC microgrids in the distributed systems. This thesis proposes a self-power solid state DC circuit breaker using normally-on SiC JFET, which offers a great protection device for DC microgrids due to its fast response time and low on-state losses. The design of the solid state DC circuit breaker aims to meet two objectives: fast response time and high reliability. The designed specifications and critical energies that result in the destruction of the circuit breaker are identified on the basis of the experiments of a commercial normally-on JFET. In addition, a very fast and reliable protection driver based on a forward-flyback converter topology is employed to generate a sufficient negative voltage to turn and hold off the SiC JFET. The converter will be activated whenever short-circuit faults are detected by sensing the drain-source voltage, then creating a negative voltage applied to the gate of JFET. To avoid gate failure by overvoltage at the gate of JFET, the output voltage of the forward-flyback converter is regulated using Primary Side Sensing technique. Experimental results validated the working principle of the proposed solid state DC circuit breaker with fault clearing time less than 3 μs. Additionally, a model of the normally-on JFET in Matlab/Simulink environment is built for exploring the behaviors of the solid-state DC circuit breaker during short-circuit faults. The agreement between the simulation and experimental results confirms that this JFET model can be appropriately used for the investigation of solid state DC circuit breaker operations and DC microgrids in general during fault evens and clearing fault processes

This work presents different novel gate drive unit (GDU) concepts for IGBT and reverse conducting IGBT (RC-IGBT). They have been experimentally tested with medium voltage class IGBT modules (1200...1700V/650…1400A) and a RC-IGBT module (1200V/200A). The switching behaviour of the RC-IGBT was investigated, and a new trigger pulse pattern to drive the RC-IGBT was developed, designed and implemented. The experimental results showed that the switching losses were reduced by 20% in the RC-IGBT compared to the switching losses of a standard diode. Two novel schemes are introduced to estimate the collector current through the IGBT, based on the measurement of the voltage across the internal stray inductance of the IGBT module. Furthermore, a GDU concept was derived to balance the on-state collector currents of parallel-connected IGBTs, reducing the current imbalance to 5%. Also, a new fast short circuit protection method (FSCP) for IGBT modules was developed, designed and implemented in another GDU, allowing turning-off the considered IGBT in less than 1μs, reducing the IGBT stress. Another scheme implemented in a GDU features an improved gate current switching profile of the IGBT, which reduces the switching losses by 25% compared to the standard switching method. In order to reduce the conduction losses, a GDU with an increased turn-on gate-emitter voltage (larger than 20 V) was investigated. In the investigated IGBT, the on-state losses were reduced by 18% when a gate-emitter voltage of 35V is used compared to when a gate-emitter voltage of 15V is used. All these new GDU concepts have been implemented with a simple and inexpensive electronic circuitry, which is an important feature for a possible industrial implementation.

This work presents different novel gate drive unit (GDU) concepts for IGBT and reverse conducting IGBT (RC-IGBT). They have been experimentally tested with medium voltage class IGBT modules (1200...1700V/650…1400A) and a RC-IGBT module (1200V/200A). The switching behaviour of the RC-IGBT was investigated, and a new trigger pulse pattern to drive the RC-IGBT was developed, designed and implemented. The experimental results showed that the switching losses were reduced by 20% in the RC-IGBT compared to the switching losses of a standard diode. Two novel schemes are introduced to estimate the collector current through the IGBT, based on the measurement of the voltage across the internal stray inductance of the IGBT module. Furthermore, a GDU concept was derived to balance the on-state collector currents of parallel-connected IGBTs, reducing the current imbalance to 5%. Also, a new fast short circuit protection method (FSCP) for IGBT modules was developed, designed and implemented in another GDU, allowing turning-off the considered IGBT in less than 1μs, reducing the IGBT stress. Another scheme implemented in a GDU features an improved gate current switching profile of the IGBT, which reduces the switching losses by 25% compared to the standard switching method. In order to reduce the conduction losses, a GDU with an increased turn-on gate-emitter voltage (larger than 20 V) was investigated. In the investigated IGBT, the on-state losses were reduced by 18% when a gate-emitter voltage of 35V is used compared to when a gate-emitter voltage of 15V is used. All these new GDU concepts have been implemented with a simple and inexpensive electronic circuitry, which is an important feature for a possible industrial implementation.