Reliability Assessment of Photovoltaic Buck-Boost Microconverter for Estonian Climate Conditions

paper evaluates the reliability of photovoltaic (PV) DC-DC converters operating in residential 350 V DC microgrids under the application mission profile from Tallinn, Estonia. The studied DC-DC converter is based on an isolated buck-boost series resonant DC-DC converter (IBBC-SRC). The mission profile comprises solar irradiation and ambient temperature with a one-second resolution for eight months in 2022, from April to November. The reliability of the IBBC-SRC is evaluated using the FIDES Guide, which takes into account the application mission profile and the physics of failure when calculating the random failure rate of the components. A comparison was made with the IBBC-SRC reliability prediction under the annual mission profiles of Aalborg, Denmark, which is commonly used to measure converter reliability. According to the analytical results, the Tallinn mission profile results in virtually the same converter failure rate as the Aalborg mission profile and, consequently, has the same thermal stress of components. The reliability prediction based on the FIDES Guide works best when the mission profile has a high resolution, but when the mission profile is recorded with a low resolution, the reliability prediction is overestimated.