Evaluating the Reliability Degradation Caused by Resonant Current in Photovoltaic Inverters With $LCL$ Filters

With the increasing deployment of photovoltaic (PV) systems, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula>-type grid-connected inverters have become prevalent due to their superior harmonic attenuation. However, conventional reliability assessments often overlook the impact of resonant currents arising from control-loop instability or parameter drift, which can significantly accelerate the degradation of key components. This paper presents a comprehensive reliability evaluation framework for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula>-type PV inverters that better reflects realistic operating conditions. An electrothermal model is developed that accounts for temperature-dependent power losses, IGBT thermal coupling, and capacitor degradation. Monte Carlo simulation and Weibull distribution are employed to derive converter lifetime under annual mission profiles. Experimental validation confirms that resonant currents introduce substantial electrical stress, and damping failure can reduce 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 by up to 55.5%. Furthermore, the study establishes quantitative relationships between resonant frequency, total harmonic distortion (THD), and converter reliability, revealing that higher resonant frequencies improve capacitor lifetime. Furthermore, the integration of reliability considerations offers valuable insights into the design optimization of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula>-type PV converters.