Lifetime Assessment of Grid-Connected PV Inverters Considering Electrolytic DC-Link Capacitor Degradation and Climate Conditions

The reliability of grid-connected photovoltaic (PV) inverters is critically influenced by the degradation of electrolytic DC-link capacitors, whose ageing modifies both thermal behaviour and semiconductor lifetime. This work evaluates that impact under two contrasting climatic conditions Belgium and Niger by combining one-year mission profiles with electrothermal simulations and a four-dimensional junction temperature estimator. Although the temperature swings <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Delta T_{j}$</tex> observed here remain modest compared with the high-amplitude conditions typically reported in the literature, clear climatic differences persist. After five years of capacitor degradation, Belgium remains within a relatively mild thermal range, with mean junction temperatures between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$323-350\ \mathrm{K}$</tex> and temperature swings <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Delta T_{j}$</tex> typically below 10 K. In contrast, Niger reaches substantially higher mean junction temperatures of around 370 K and exhibits much larger thermal-cycle amplitudes of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$20-25 ~\mathrm{K}$</tex>. These thermal differences lead to distinct lifetime consumption (LC) trajectories: Belgium accumulates LC slowly due to its moderate climate, whereas Niger experiences markedly higher LC driven by elevated temperatures and stronger cycling. When extrapolated to 20 years, Niger reaches nearly 45% cumulative LC compared with about 22 % in Belgium, underscoring the strong climatic influence on inverter wear-out. The proposed framework enables climatespecific lifetime assessment and supports more robust design strategies for future PV inverters.