On-Line Condition Monitoring System for DC-Link Capacitor of Back-to-Back Converters Using Large-Signal Transients

The increasing use of power electronic equipment and the importance of their continuous and correct operation have attracted remarkable attention to the condition monitoring of power electronic converters. Since capacitors are the leading cause of power electronic converters failure, this article attempts to attain a solution to monitor the condition of the dc-link capacitor in a three-phase back-to-back converter using the stimulated measurable transients. The proposed method works based on the temporary change of switching logic and the measurement of the dc-link voltage and converter input phase current transients. By processing the measured signals, the capacitance of the capacitor is calculated as an indicator of its degradation. The results of simulations and experimental studies are presented to verify the proficiency of the proposed method. Based on the results, the calculated capacitance is consistent with the value measured by an LCR meter with an estimation error of less than 1%.