Reliability Assessment of IGBT Modules in LCL-Type Photovoltaic Systems Considering Resonant Currents

Reliability is critical for the efficient operation, maintenance, and cost reduction of LCL-type photovoltaic (PV) inverter. The generation of resonant currents from filter oscillations leads to increased electrothermal stress on the insulated-gate bipolar transistor (IGBT) module, causing notable inaccuracies in lifetime prediction. This article conducts a thorough analysis of IGBT module reliability to quantify the estimation error induced by the resonant current. Two power loss models are derived by the Fourier transform, which makes the loss analysis away from simulation and becomes easy to modify and optimize. In addition, a thermal model of the power semiconductor, considering the thermal cross-coupling effect between components is established. It is further transformed into components' annual damage by lifetime and damage accumulation models. Then, the reliability curves of the modules are developed by reliability block diagrams using Monte Carlo simulation and Weibull analysis. The electrical stress on the IGBT module is experimentally verified. Detailed electrothermal comparisons between systems with and without resonant currents are provided. These comparisons indicate significant impacts on the modules' reliability from resonant currents. Failure of the damping method results in a 40.8% reduction in the lifetime. The results of the investigation provide a novel perspective on the design of LCL-type PV inverters.