Mission Profile-based Accelerated Testing of DC-link Capacitors in Photovoltaic Inverters

The dc-link capacitor is considered as a weak component in Photovoltaic (PV) inverter system and its reliability needs to be evaluated and tested during the product development. Conventional reliability testing methods do not consider the real operating conditions (e.g., mission profile) of the dc-link capacitor during the test. Therefore, the validation of the reliability performance of the dc-link capacitor under its mission profile is still a challenge. To address this issue, a new reliability testing concept for the dc-link capacitor in PV inverters is proposed in this paper. In contrast to the conventional method, the proposed reliability testing method realizes 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 to the solar irradiance amplitude and the ambient temperature level during the mission profile modification in order to increase the thermal stress of the dc-link capacitor during test, and thereby effectively reduce the testing time. The results show that the testing time can be reduced to 2.5 % of the real field operation lifetime, if the solar irradiance amplitude is increased by 20 % and the ambient temperature is elevated to 75 degrees C.