Reliability Analysis of Single-Phase PV Inverters with Reactive Power Injection at Night Considering Mission Profiles

The widespread adoption of mixed renewables urgently require reactive power exchange at various feed-in points of the utility grid. Photovoltaic (PV) inverters are able to provide reactive power in a decentralized manner at the grid-connection points even outside active power feed-in operation, especially at night when there is no solar irradiance. This serves as a motivation for utilizing the PV inverters at night for reactive power compensation. Thus, an analysis on the impact of reactive power injection by PV inverters outside feed-in operation on the thermal performance and the reliability has been performed in this paper. A thermal analysis is incorporated to determine the additional temperature rise in the power switching components outside the feed-in operation. This analysis enables the translation from long-term mission profiles (three different mission profiles) to device thermal loading, considering the operation outside active feed-in hours. An analytical lifetime model is then employed for lifetime quantization based on the Palgrem Miner rule. Thereafter, considering the lifetime reduction of the PV inverter under different mission profiles with reactive power injection at night, the impact of PV sites on the economic value of the inverter is assessed. This analysis can be useful in choosing between conventional reactive power compensation devices or PV inverters for injecting reactive power to the grid.