Lifetime Evaluation of Power Modules for Three-Level 1500-V Photovoltaic Inverters

The installation cost of Photovoltaic (PV) systems can be reduced considerably by extending the maximum DC voltage from 1000 V to 1500 V (e.g., with more PV arrays connected in series). However, the increased DC voltage challenges the design and operation of PV inverters in terms of efficiency and reliability. To fulfill the requirements of an efficient and reliable PV power conversion, an early-stage evaluation plays an important role in the inverter design phase. This paper, thus, evaluates the lifetime of power modules for three-level 1500-V PV inverters with respect to their thermal cycling capabilities. The evaluation is carried out by case study of 160-kW inverters considering the impact of voltage stress, switching frequency and mission profile. The evaluation reveals that these factors have considerable impact on the inverter lifetime and thus affect the topology selection and the final cost of the entire PV system.