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Politecnico di Milano (2016)

Reliability assessment of Photovoltaic Plants


Titre : Reliability assessment of Photovoltaic Plants


Université de soutenance : Politecnico di Milano

Grade : Dottorato 2016

Résumé partiel
Failures of Photovoltaic (PV) systems started to reflect a dramatic effect on the economics of power generation and risk of power interruptions. Recent surveys and reports manifest the delusion of PV systems being reliable systems based on the recorded failures of the system components and the associated degradation of PV output power. The thesis presents a complete reliability assessment on the functional failures associated with grid connected PV systems. This objective is achieved by a root cause analysis of failures through the widely used reliability technique “Failure Mode Effect Criticality Analysis (FMECA)”, which is developed in this work and a new approach is introduced. The new approach is introduced because the traditional FMECA approach is not recognized during the operation phase in all the current FMECA standards, except TM-5-698-4 standard that states the possibility to implement FMECA in the operation phase. However, TM-5-698-4 standard does not state any details on the steps to implement FMECA in the operation phase. Since the traditional FMECA is limited to the design phase, the traditional FMECA considers only failure modes and no considerations are given to the mechanisms of these failure modes. Moreover, traditional FMECA is not up-to-dated with maintenance activities. The novelty of the new FMECA approach stems from the possibility to apply a strong FMECA technique during the operation phase through a strong dynamic reliability modelling, using Markov Process based on functionality analysis with multistate modelling, and a proper condition monitoring. In this work, the drawbacks and standards controversies of the traditional FMECA are discussed and a new approach is introduced. This new approach is applied on PV systems during the design and operation phases. During the design phase, the root failure causes of PV systems are studied in details through FMEA approach and criticality analysis. A detailed failure cause root analysis is conducted for each possible failure mode of PV systems. This is associated with a prioritization for each failure mode using quantitative methods, for PV inverter, and a qualitative approach, for PV module and Balance of System (BoS). During the operation phase of PV systems, Markov process modelling and condition monitoring are applied on the different failure modes of PV systems. In Markov modelling, a functional analysis based on possible failure modes are conducted using Markov process through another route of analysis based on failure modes which is different than most of Markov structural analysis, carried out in literature, of the traditional two levels of performance


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