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Abstract-The use of a Smart Transformer-based electrical distribution could be an effective approach to reorganize the electric grid, solving the problems and challenges of distributed generation systems and active loads. While lower efficiency and higher cost compared to the conventional transformer are well known and investigated limiting factors, the required higher maintenance, related to the use of electronics systems in the electric grid, is seldom targeted. In fact, high maintenance cost would make the use of Smart Transformer inapplicable even if new services could justify higher initial cost and new semiconductor development could increase the overall efficiency. This work proposes a modular repairable system based on condition monitoring, which aims at equalizing the lifetime consumption of the single modules to make possible prognostic maintenance.

Nowadays, the necessity of efficient and reliable power systems is increasing in order to meet the strict requirements imposed by standards and regulations with minimum cost. One specific requirement is focused on the maximization of the power converters lifetime what produces a reduction in the maintenance cost. However, to overcome the related challenges is not a straight-forward task as it involves knowledge of power devices physics, smart management of electrical magnitudes and optimal maintenance planning and scheduling. It represents a multidisciplinary issue being faced in the last decade. As a first issue to be considered, it is clear that the evolution of power electronics is playing a principal role in the world in many ways:• development of environmentally friendly and economically affordable clean energy sources such as the wind and solar energy [1],• installation and enhancement of facilities to develop the robust, reliable and high quality distributed electrical grid including the smart grid paradigm with distributed energy storage systems [2]-[5],• efficient and low cost freight transportation based on electric vehicles, low-fuel consumption cargo ships and more electric aircraft [6],• personal transportation such as electric motorbikes, electric cars, robust high-speed trains, efficient subways with regenerative breaking, public electric buses, etcetera [7].The power electronic applications, that include multi-disciplinary research topics such as digital signal processing, power electronics and power systems, have actually experienced a technology disruption in the last decades [8]:1) new power semiconductor devices with high voltage/current ratings and very low power losses; 2) powerful microprocessor hardware platforms including accurate sensors and high-bandwidth data acquisition systems; 3) effective simulation and design software tools to predict the behavior of power systems.Power electronics reliability and consequently the corresponding required power systems maintenance cost is one of the major concerns of this technology [9]. An accurate estimation of the remaining useful lifetime (RUL) of a power converter is fundamental to reduce the maintenance cost [10]. Historically, the first approaches to estimate the RUL were just limited by the manufacturers guarantee. The power system operator just counted the power converter years in operation to decide when it had to be replaced by a new unit. But it is clear that the accuracy of this approach is low because the RUL highly depends on the operating conditions of the power system, usually called mission profile. For instance, factors such as the ambient temperature and the actual power that is managed by the power system highly influences the possibility of failure in any power converter component [11].

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