Reliability and Mission Profiles of Photovoltaic Systems

Current methods for reliability prediction are based on physics-of-failure approaches. Such is the case of the FIDES methodology that takes into account the times sequences of operation of an electronic assembly. In this paper, the reliability of a dc/dc converter aimed at photovoltaic applications is explored, considering the mission profiles for three different installations sites, at latitudes ranging from N 18.65 to N 32.67. Meteorological data collected in a ten-year time span were available for these sites.

The mission profiles were obtained by first dividing the output power provided by a photovoltaic panel into ten levels, and then retrieving the temperature and humidity conditions that concur at each level. The components with the highest contribution to the overall failure rate λ were the diodes, followed by the capacitor at the output. The results indicate that the thermal factor has the largest impact on the failure rate λ, highlighting the importance of efficient heat-management techniques. When the effect of the individual operational phases was assessed, it was also found that those linked to power levels above 70% are responsible of the largest contribution to λ. In the case of the dormant condition, the highest humidity produces the highest failure rate.