Abstract

Reliable and unceasing exploitation of power electronic converters plays a major part in every application. This PhD thesis comes up with new opened-up reliability assessment frameworks and demonstrates the feasibility of using multistate degraded system analysis and interval analysis as well for attaining much more accuracy in reliability evaluation. Considering self- and coupling degradation effects of the items and assessing reliability in the system level are important issues which are still lacking in the previous studies and the present thesis has made an effort to overcome these problems. The thesis tries to launch two distinct reliability assessment frameworks, namely interval reliability and Multistate degraded system reliability.Interval reliability is capable of introducing an interval useful lifetime for DC-DC power electronic converters in which the self and coupling degradations effects of items have been taken into account. Fundamentally, it is based on the conventional physics of failure reliability assessment. Based on this method, instead of obtaining an inaccurate reliability value, one can attain an interval for the reliability of a global system whose useful lifetime undoubtedly lays between the boundaries. This method is able to consider degradation dependencies and assess multi-component system level reliability but not redundant system. An attempt was made to enhance the conventional reliability framework to reach a systematic approach capable of estimating a reliability assessment considering self and mutual degradation effects and being able to evaluate system-level reliability including redundant system. Multistate degraded system reliability analysis is capable of estimating system-level reliability, while mission profile and physics of failure of the system’s items are taken into account. In addition, the self and mutual degradation effects of items on the operation of the global system have been considered. The multi-state degraded system reliability model exposed to multiple failure processes has been generalized. The operating condition of the global system is defined by a finite number of states. Not only can the proposed framework be employed in determining the reliability of the degraded systems in terms of multi-state functions, but also it can obtain the states of the systems by estimating the system state probabilities.As an application, a DC-DC power electronic system containing three critical items has been studied. In this case study, two power semiconductors, namely IGBT and diode, and a power capacitor have been considered as three degradation processes and their aging effects on the useful lifetime estimation of the power electronic system have been discussed. For having a sense about newly proposed reliability frameworks, a 3000W and 200/400 V conventional DC-DC converter for electric vehicle application exposed to WLTP driving cycle is considered.; La fiabilité et la sureté de fonctionnement de l'électronique de puissance jouent un rôle majeur aujourd'hui dans l'industrie. Cette thèse propose un nouveau cadre d'étude de la fiabilité à partir de deux méthodes afin d'améliorer la précision des études de fiabilité : une analyse utilisant la méthode des système dégradés multi état, et une analyse par intervalles. La considération des effets de dégradation propres et couplés de chaque composant est également une problématique qu'il reste aujourd'hui à étudier et qui est traitée dans ce travail.L'étude de la fiabilité par intervalles permet d'estimer des intervalles de durée de vie des convertisseurs DC/DC en prenant en compte les dégradations propres et mutuelles des composants. Fondamentalement, cette méthode est basée sur la compréhension des phénomènes physiques. A partir de cette méthode, on peut obtenir un intervalle pour la durée de vie d'un système complet. Cette méthode n'est toutefois pas adaptée aux systèmes redondants.De son côté, la fiabilité des systèmes dégradés multi-états est capable de proposer une étude au niveau système en prenant en compte le profil de mission et la physique des dégradations.Cette méthode a été généralisée dans cette thèse au procédés subissant de multiples dégradations. L'exemple d'un convertisseur DC/DC conprenant trois composants critiques a été étudié comme cas d'application. Deux composants semiconducteurs, diode et IGBT, et un condensateur sont considérés comme trois process de dégradation et l'effet de leur vieillissement sur la durée de vie du convertisseur est discutée. Le convertisseur étudié a pour puissance 3 kW (200/400V) et est dédié aux applications de type véhicule électrique. Il subit un profil de mission typique automobile (cycle WLTP).

Abstract

RelStat12, 12th Annual International Conference on Reliability and Statistics in Transportation and Communications, Riga, LETTONIE, 17-/10/2012 - 20/10/2012; Along a transit line, vehicle traffic and passenger traffic are jointly subject to variability in travel time and vehicle load hence crowding. The paper provides a stochastic model of passenger physical time and generalized time, including waiting on platform and in-vehicle run time from access to egress station. Five sources of variability are addressed: (i) vehicle headway which can vary between the stations provided that each service run maintains its rank throughout the local distributions of headways; (ii) vehicle order in the schedule of operations; (iii) vehicle capacity; (iv) passenger arrival time; (v) passenger sensitivity to quality of service. The perspective of the operator, which pertains to vehicle runs, is distinguished from the user's one at the disaggregate level of the individual trip.

Abstract

It is increasingly recognized that travel time reliability is important to travellers and goods, and hence there is an increasing demand to include reliability in the evaluation and appraisal of transport projects and programs, as a separate factor in its own right. A number of the policy options already in use as congestion mitigation policies have also positive impacts on the travel time reliability. It is therefore important to evaluate impacts of any remedial action separately both for average travel time (congestion) and for variability of that travel time (reliability). The impacts are generally assessed with an observational before/after study. As many things, independent from the system to be assessed, change between the periods before and after the installation of the system, observational before/after studies take also into account a reference site, where the effect of these changes is identified. In a previous paper Bhouri and Aron, (2013) presented the reliability impacts of a managed lane case consisting in a Dynamic Hard Shoulder Running (HSR) during rush hours on a French urban motorway. The study was conducted by comparing reliability indicators based on data collected in 2002 before the implementation of the system and in 2006 after this implementation. Jacques Chirac, former president of France, launched in 2003 an important campaign for road safety and against speeding. This modified the travel time distribution, differently according to the lane. As reliability is based on the percentiles (and not only on averages), it was necessary, in order not to confound the effect of this campaign with the HSR effect, to develop the observational before/after study method for determining that time effect by level of travel time: to do this, the before and after travel time distributions of the reference site are established, then their difference is analyzed as a function of the travel time, taking into account the percentiles. This method and the results are presented in this paper. Document type: Conference object

Abstract

Managed lanes operations refer to multiple strategies for recurring congestion control by increasing the road capacity or adapting its configuration to the demand level. As a result, the evaluation of their impacts usually focuses on congestion or safety-related indicators. However, with the growing prosperity, consumers demand higher quality transport services, for which reliable transport networks are central. This paper is focused on the travel time reliability assessment of a managed lane experience from a French motorway. The paper shows results from the field test experience of the hard shoulder dynamic use on the A4-A86 motorway in the east of Paris. Further to the reliability assessment, the paper focuses on the reliability indicators. It particularly shows the weakness of the skew of the distribution of travel time indicator.; La gestion dynamique des voies fait appel à de multiples stratégies pour maîtriser les congestions récurrentes, ce en accroissant la capacité de la route ou en adaptant sa configuration à la demande. Ces stratégies sont donc logiquement généralement évaluées en termes d'impacts sur la fluidité ou la sécurité du trafic, impacts mesurés par des indicateurs. Cependant, avec la prospérité croissante, les consommateurs demandent une amélioration de la qualité de service pour laquelle la fiabilité des réseaux de transport est centrale. Cette communication porte sur l'évaluation de la fiabilité des temps de parcours résultant d'une expérimentation de gestion dynamique des voies sur une autoroute en France - le tronc commun A4-A86, à l'est de Paris. La bande d'arrêt d'urgence y a été ouverte à la circulation à certaines périodes de la journée. Les résultats de cette expérimentation sont donnés ici ; à la lumière de ces résultats notamment, les indicateurs de fiabilité sont ensuite discutés. On montre en particulier la faiblesse de certains indicateurs fondés sur la largeur ou la dissymétrie de la distribution des temps de parcours. Document type: Conference object

Abstract

Increasing mobility and congestion results in an increase in travel time variability and in a decrease in reliability. Reliability becomes an important performance measure for transportation facilities. A variety of performance measures have been proposed to quantify it. Many of these indicators are based on percentiles of travel time. The knowledge of the distribution of travel time is needed to properly estimate these values. Congestion distorts the distribution and particular statistical distributions are needed. Different distributions have been proposed in the literature. In a previous paper, we presented a comparison of six statistical distributions used to model travel time. These six distributions are the Lognormal, Gamma, Burr (extended by Singh-Maddala), Weibull, a mixture of two Normal distributions and a mixture of two Gamma distributions. In this paper a probabilistic modeling of travel time which takes into account the levels-of-service is given. Levels of service are identified, then travel time distributions are modeled by level of service. This results in a very good fit between the empirical and modeled distributions Moreover, the adjustment was improved, thanks to the calibration of “Bureau of Public Roads” functions, linking the travel time to the traffic flow by level of service. The superiority of the Singh-Maddala distribution appears in many cases. This has been validated, thanks to travel time data from the same site at another period. However the parameters of the distributions vary from one year to another, due to changes in infrastructure. The transferability of the approach, not performed, will be based on travel time data on another site. Document type: Conference object