Abstrakt
Photovoltaic (PV) power optimizers are introduced in PV systems to improve
their energetic productivity in presence of mismatching phenomena and not
uniform operating conditions. Commercially available converters are
characterized by different DC-DC topologies. A promising one is the boost
topology with its different versions. It is characterized by its circuital
simplicity, few devices and high efficiency values - necessary features
for a Distributed Maximum Power Point Tracking (DMPPT) converter. PV power
optimizer designs represent a challenging task since they operate in
continuously changing operating conditions which strongly influence
electronic component properties and thus the performance of complete
converters. An aspect to carefully analyze in such applications is the
thermal factor. In this paper, a necessity to have a suitable temperature
monitoring system to avoid dangerous conditions is underlined In addition,
another important requirement for a PV power optimizer is its reliability,
since it can suggest a useful information on its diagnostic aspects,
maintenance and investments. In fact, a reliable device requires less
maintenance services, also improving the economic aspect. The evaluation
of the electronic system reliability can be carried out using different
reliability prediction models. In this paper, reliability indices, such as
the Mean Time Between Failure (MTBF) or the Failure Rate of a Diode
Rectification (DR) boost, are calculated using the evaluation of the
Military Handbook 217F and Siemens SN29500 prediction models. With the
reliability prediction results it has been possible to identify the most
critical components of a DMPPT converter and a measurement setup has been
developed in order to monitor the component stress level on the
temperature, power, voltage, current, and energy in the DMPPT design phase
avoiding the occurrence of a failure that might decrease the service life
of the equipment.
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