Electrolytic Capacitor Condition Monitoring Using DC-Bus Voltage Ripple Analysis

This paper presents a novel method for estimating the capacitance of DC-link capacitors in frequency converters. The proposed approach leverages the characteristic changes in the DC-link voltage slope induced by capacitor aging, specifically degradation in capacitance and equivalent series resistance (ESR). The estimation algorithm extracts the 100 Hz and 300 Hz voltage ripple harmonics at the rectifier output to determine the ripple amplitude. The applicability of this method is inherently limited to topologies utilizing front-end diode rectifiers. The proposed estimation method allows for very small errors, ranging from 0.5% to 9%, even with very large capacity changes. Simulation models were validated using a comprehensive experimental dataset acquired from a dedicated laboratory setup. Furthermore, the robustness of the capacitance estimation process was evaluated under various grid and load disturbances.