Loss and Lifetime Evaluation of Electrolytic Capacitors in Offshore Photovoltaic Inverters under Salt-Spray Corrosion

Offshore photovoltaic generation is an emerging strategic direction for deep-sea renewable-energy development. However, aluminum electrolytic capacitors used in PV inverters are exposed for long periods to marine salt-spray environments, where corrosion causes serious degradation and shortens their service life. Existing lifetime-assessment studies for PV-inverter capacitors mainly consider temperature ripple-current and voltage stresses, while the influence of salt-spray corrosion and its relationship with parameter degradation are often neglected.This paper takes the aluminum electrolytic capacitor in an offshore floating PV inverter as the research object.Based on the time-varying degradation of equivalent series resistance with frequency characteristics, an electrothermal loss model coupling corrosion degradation and ripple current is established. Different from traditional models without corrosion factors An improved Arrhenius lifetime model with a corrosion acceleration factor is then constructed and combined with the Miner cumulative-damage rule to quantify capacitor lifetime under salt-spray corrosion. The study provides a useful reference for reliable design and operation of offshore PV equipment.