ThesisPDF Available

Contribution a la caracterisation et a la commande rapprochee de composants a grand gap moyenne tension pour onduleur de tension

Authors:
  • Yazaki Europe Limited

Abstract and Figures

In an economic and political climate that promotes the use of electric vehicles, since 2011 Renault offers a range of EVs. The powerful models are based on an electrical architecture of 60 kW to 70 kW traction inverters and a 400V DC BUS. The static converters used, as in every embedded power system, must have high energetic yield, high robustness and high reliability during every operating phase of the vehicle. At the same time, the power electronics field is currently undergoing a technical revolution. New wideband gap power devices, such as Silicon Carbide (SiC, in the range of 600V, 1200V and 1700V) and Gallium Nitride (up to 600V), are available on the market. Those components are characterized by both voltage (dv/dt) and current (di/dt) high speed switching, and also by operating temperatures above than 175°C. These characteristics not only offer the prospect of achieving better performance converters, obtaining a significant gain on the autonomy of electric vehicles, but also more compact converters, facilitating their integration into the vehicle. However, these extreme switching are sources of issues, especially in the inverter topologies. Thus, based on a partnership between the LAPLACE Laboratory in Toulouse and RENAULT Technocentre in Guyancourt, three main problematic areas were addressed by this PhD research. First of all, there was a detailed analysis of the switching phenomena in an inverter switching cell. This work enabled the establishment of simple analytical models. These models allow, from the principal physical and linearized quantities of the components and from the functional parameters of the driver, direct predetermination of dv/dt and di/dt across the inverter operating range. The second topic deals with the characterization of these new power devices. A 1200V Cree SiC MOSFET and a first generation GaN HEMT power module from the prototype chain of CEA-LETI in Grenoble have been characterized in static and dynamic operation in both reverse and direct conduction mode. The results allowed the development of a static and dynamic behavioral model, using PSPICE type circuit elements, dedicated to the use of GaN HEMT transistors in a voltage inverter. The advantage of this model is its ability to emulate the reverse conduction in both gate bias cases (VGS>VGTH and VGS<VGTH) as per the operating conditions of an inverter leg. The third topic related to the gate drive operation of these components was based on the analytical modeling of the switching process. The work includes the proposal and test optimization of active or passive gate drive strategies. Two passive adjustment approaches could thus be compared in terms of dv/dt - Switching Energies trade-off, one overall and classic by the gate driver resistance ; another more selective by including a capacitor between the gate and drain of the components. This second method, for a specified dv/dt, may cause a switching energy loss saving of up to 18%. A final active method has been studied and tested via simulation. In principle, the proposed circuit consists of a limitation of di/dt, without influencing the dv/dt. The control loop uses the voltage that appears across the source inductance during switching of the current to activate an auxiliary transistor which brings or takes electric charges to and from the power transistor gate in order to ultimately obtain a di/dt real-time control.
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... Les fortes vitesses de commutation de courant des convertisseurs à base de transistors GaN qui atteignent plus de 1.5 A/ns créent des surtensions et des sous-tensions via la présence d'éléments parasites inductifs [8]. Comparées aux convertisseurs à base de silicium, ces surtensions ou sous-tensions augmentent les perturbations électrostatiques de manière considérable. ...
... Pour ce qui concerne les fortes pertes dues aux temps morts, de nouvelles techniques de pilotage du transistor seront proposées tout en minimisant l'effet des fortes vitesses de commutation en tension par le phénomène de « Cross Talk » dans le cas d'un bras d'un onduleur. Pour pouvoir mettre en place ces solutions de manière efficace, un modèle comportemental du transistor GaN sera adapté avec un nombre réduit de paramètres [8,9]. Ce modèle sera un élément clé dans le dimensionnement des briques du driver qui rendront possible l'intégration des éléments du driver sur la puce de puissance GaN afin de minimiser de la manière la plus optimale les effets dus à la présence d'inductances parasites entre la partie commande et la partie puissance. ...
... Figure II.9 : profil des capacités obtenu par l'extraction dynamique HEMT GaN [8] Malgré l'inconvénient mentionné précédemment concernant la méthode d'extraction des capacités (profil imprécis), cette méthode dynamique a donné des résultats très satisfaisants en commutation comme le montre la figure II.10. Régime direct : ...
Thesis
Cette thèse s'inscrit dans un contexte de développement durable où les enjeux énergétiques consistent à concevoir des convertisseurs de puissance plus disséminés, donc avec une Spécification ambitieuse en termes de densités massique et volumique. Les composants à semiconducteur dit à grand Gap permettent l’augmentation de la fréquence de commutation et permettent un fonctionnement à plus haute température locale. Les commutations à front raides et à haute fréquence des transistors rendent le système plus sensible aux éléments parasites. Ceci perturbe en retour la commutation des transistors et génère des pertes joules supplémentaires. Dans ce contexte les travaux ont été effectués dans le cadre d’une cotutelle entre les laboratoires Ampère (INSA Lyon) et LN2 (Université de Sherbrooke), le but étant d’apporter des contributions à l’optimisation de la commutation des HEMTs GaN. Le premier axe des travaux consiste à mettre en place des stratégies de contrôle de vitesses de commutation en tension et en courant, par la grille, dans le but d’améliorer la signature CEM. Les circuits de contrôle proposés sont développés dans un premier temps en boucle ouverte puis dans un second temps en boucle fermée afin de compenser des non-linéarités (température, courant de charge et tension de fonctionnement). Les prototypes de contrôle de grille ont été testés à partir de composants discrets du marché. Des limites apparaissent, que l’intégration monolithique GaN doit corriger à terme, en particulier en atténuant fortement le problème des inductances parasites. Les analyses en simulation ont reposé sur l’adoption d’un modèle comportemental de HEMT GaN identifiable. Le deuxième axe des travaux consiste à vérifier de manière systémique différentes stratégies de contrôle de grille notamment pour la gestion du compromis entre pertes joule pendant les temps morts au sein d’un à bras d’onduleur et la performance fréquentielle des commutations. Aux termes de ces travaux, les systèmes de contrôles développés en boucle ouverte ont permis de ralentir les vitesses de commutation d’au moins 30 %, occasionnant une augmentation des pertes de commutation, dans un ordre de grandeur inférieur à 50 %. Due à la rapidité de commutation des HEMT GaN et aux limites des composants discrets du marché, le taux de réduction des vitesses de commutation obtenu avec la boucle fermée (taux de réduction inférieur à 20 %) est moins intéressant qu’avec la boucle ouverte. L’utilisation d’un circuit monolithique peut être une alternative pour augmenter le taux de réduction des vitesses de commutation en boucle fermée. Des résultats de simulation sous SPICE en vue du circuit monolithique sont à la base de cette hypothèse. Concernant le deuxième axe, l’application de commande multiniveaux de grille des transistors du bras d’onduleur a permis de réduire les pertes de conduction inverse et les pertes dues aux phénomènes de Cross Talk d’au moins 30 %.
... This study is based on personal work but also on [100,186]. A part of the study was made during my internship at Tennessee University in Knoxville, UTK. ...
... • In phase 1 (t0 < t < t1), the transistor is blocked and the gate current is starting to charge Cgs and C dg through the reverse conduction mode of the top switch of the phase leg. According to [186] ...
Thesis
The french industrial project MEGaN targets the development of power module based on GaN HEMT transistors. One of the industrial applications is the aeronautics field with a high-constraint on the galvanic isolation (>100 kV/s) and ambient temperature (200°C). The intent of this work is the power module block (3 phases inverter 650 V 30 A). The goal is to obtain a small footprint module, 30 cm2, with necessary functions such as gate driver, gate driver power supply, bulk capacitor and current phase sensor. This goal implies high efficiency as well as respect of the constraint of galvanic isolation with an optimized volume. This dissertation, besides the state of the art of power modules and especially the GaN HEMT ones, addressed a control signal isolation solution based on coreless transformers. Different prototypes based on coreless transformers were characterized and verified over 3000 hours in order to evaluate their robustness. The different studies realized the characterization of the different market available GaN HEMTs in order to mature a circuit simulation model for various converter topologies. In the collaborative work of the project, our contribution did not focus on the gate driver chip design even if experimental evaluation work was made, but a gate driver power supply strategy. The first gate driver isolated power supply design proposition focused on the low-voltage GaN HEMT conversion. The active-clamp Flyback topology allows to have the best trade-off between the GaN transistors and the isolation constraint of the transformer. Different transformer topolgies were experimentally performed and a novel PCB embedded transformer process was proposed with high-temperature capability. A lamination process was proposed for its cost-efficiency and for the reliability of the prototype (1000 H cycling test between - 55; + 200°C), with 88 % intrinsic efficiency. However, the transformer isolation capacitance was drastically reduced compared to the previous prototypes. 2 high-integrated gate driver power supply prototypes were designed with: GaN transistors (2.4 MHz, 2 W, 74 %, 6 cm2), and with a CMOS SOI dedicated chip (1.2 MHz, 2 W, 77 %, 8.5 cm2). In the last chapter, this dissertation presents an easily integrated solution for a phase current sensor based on the magnetoresistance component. The comparison between shunt resistor and magnetoresistance is experimentally performed. Finally, two inverter prototypes are presented, with one multi-level gate driver dedicated for GaN HEMT showing small switching loss performance.
Thesis
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