Design for Accelerated Testing of DC-Link Capacitors in Photovoltaic Inverters Based on Mission Profiles

The dc-link capacitor is considered as a weak component in photovoltaic (PV) inverter systems and its reliability needs to be evaluated and tested during the product development. Conventional reliability testing methods for capacitors are typically carried out under constant loading conditions, which do not reflect the real operating conditions (e.g., mission profile) of the dc-link capacitor in PV inverters. To address this issue, a new reliability testing concept for the dc-link capacitor in PV inverters is proposed in this article. In contrast to the conventional method, the proposed reliability testing method designs the test profile through the modification of the original mission profile (e.g., solar irradiance and ambient temperature) in order to maintain the test condition as close to the real application as possible. A certain acceleration factor is applied during the mission profile modification based on the lifetime model of the capacitor, in order to increase the thermal stress of the dc-link capacitor during test, and thereby effectively reduce the testing time.