Mission Profile Translation to Capacitor Stresses in Grid-Connected Photovoltaic Systems

DC capacitors are widely adopted in grid-connected PhotoVoltaic(PV) systems for power stabilization and control decoupling. They have become one of the critical components in grid-connected PV inverters in terms of cost, reliability and volume. The electrical and thermal stresses of the DC capacitors are varying along with the intermittent solar PV energy (i.e. of weather-dependency) and also the grid conditions (e.g. voltage fault transients). This paper serves to translate real-field mission profiles (i.e. solar irradiance and ambient temperature) into voltage, current, and temperature stresses of the DC capacitors under both normal and abnormal grid conditions. As a consequence, this investigation provides new insights into the sizing and reliability prediction of those capacitors with respect to prior-art studies. Two study cases on a single-stage PV inverter and a two-stage PV inverter are demonstrated by simulations and experiments. The results have verified the discussions.