Mission Profile-Oriented Reliability Assessment of Capacitor Banks in Three-Level PV Inverters

As solar power generation becomes more widespread, ensuring reliable and cost-effective energy production is critical. The three-level inverter-based PV system, widely adopted in the solar industry, relies heavily on power capacitors both in DC-link and AC-side filter banks. This paper analyzes their reliability under mission profiles from the field. By evaluating electro-thermal stresses under varying loads, the lifespan of individual capacitor can be estimated. These results are then extended to a Weibull lifetime distribution, accounting for manufacturing tolerances and uncertainties. By using the reliability block diagram, the reliability analysis scales from component-level single capacitor to the entire capacitor bank. A case study on a commercial PV inverter reveals a notable reduction in life cycle at the system level, with the DC-link capacitor bank being the primary limiting factor.