Reliability of DC-link Capacitors in Two-Stage Micro-Inverters under Different PV Module Sizes

The dc-link capacitor is one of the lifetime-limiting components in the photovoltaic (PV) micro-inverters, whose reliability should be evaluated carefully during the design. In micro-inverters, the PV module size (e.g., number of cells) is the parameter that determines the power rating of the PV module. The PV module size employed in the micro-inverter can vary for different manufacturers, and this variation can strongly affect the thermal stress and reliability of the dc-link capacitor in micro-inverters. To address this issue, an experimental-based reliability assessment is carried out in this paper using a two-stage micro-inverter where 60-cell and 72-cell PV modules are considered. Three different daily mission profiles are employed during the experimental test. The thermal stress and reliability of the dc-link capacitor under different operating conditions are evaluated together with the energy yield. The results indicate that employing a 60-cell PV module is more beneficial for the micro-inverter, especially during a clear day, where 19 % more energy can be captured during the entire lifespan of the micro-inverter. Thus, using the 60-cell PV module offers a better tradeoff between the reliability and energy yield of the micro-inverter.