Abstract
This paper investigates the reliability of an isolated buck-boost DC-DC converter (IBBC) based on the configuration of a series resonant converter (SRC). Two approaches are employed to predict the IBBC reliability, which are based on the MIL-HDBK-217F handbook and FIDES guide. The latter approach can take into account how the failure rate of the converter components based on the physics of failure is influenced by a varying yearly mission profile. To do this, the thermal loading of each IBBC component is obtained, taking into account the photovoltaic (PV) mission profile of the solar irradiance and ambient temperature. In such a case, the PV module is operating at the maximum power point (MPP) and the IBBC transfers this power into the DC microgrid (MG). Second, the component-level failure rate is calculated with both reliability assessment approaches, to evaluate the converter-level failure rate. Therefore, the converter reliability can be defined while taking the serial reliability connection of the converter components into account. The reliability analysis is carried out using a cloud Python engine installed and running in a Google Colaboratory notebook. The results indicate that the primary semiconductors are the most vulnerable component in the IBBC. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$B_{10}$</tex-math></inline-formula> lifetime of the case-study IBBC calculated using the MIL-HDBK-217F and FIDES approaches is 14.80 and 23.20 years, respectively. This indicates that, when compared to the methodology from the MIL-HDBK-217F handbook, the approach from the FIDES guide can provide a more accurate prediction for the IBBC lifespan considering the real field mission profile.
Highlights
N OWADAYS, power electronics represent a major challenge in solar energy systems since they are more prone to failure, up to 66 % [1], and have lower lifetime compared to the PV module lifetime, which could reach up to 25 years
The library of the rainflow counting algorithm is used to handle the non-uniform thermal profile of the isolated buck-boost DC-DC converter (IBBC) component in order to evaluate its number of thermal cycles for using within FIDES reliability evaluation approach
The paper has discussed the reliability of IBBC based on the series resonant converter (SRC) for PV applications under a yearly mission profile using two reliability assessment approaches
Summary
N OWADAYS, power electronics represent a major challenge in solar energy systems since they are more prone to failure, up to 66 % [1], and have lower lifetime compared to the PV module lifetime, which could reach up to 25 years. The isolated series resonant converter (SRC) emerges as a most promising isolated DC-DC converter to regulate the wide range variation in input voltage for PV applications [9] as (i) it has direct power transfer to the load, (ii) good transformer utilization, and (iii) soft-switching features. It can work at a fixed-switching frequency while retaining the softswitching through the magnetizing current of the isolation transformer. The failure rate for the primary and secondary IBBC semiconductors is assessed in addition to the isolation transformer and resonant capacitor.
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