Cost Effective and High Noise Immunity Methodology for Aging Evaluation of DC-link Capacitors in Traction Inverters

DC-link capacitors are among the most critical components in traction inverters, with a significant potential for failure. Effective condition monitoring (CM) of these components is essential to enhance converter reliability and to prevent catastrophic failures. This paper presents a cost-effective methodology for evaluating the state-of-health of film capacitors used in traction inverters DC-link. The proposed approach is very simple and employs a controlled discharge test to measure capacitance variation over time, serving as an indirect indicator of capacitor aging. The main strengths of the proposed technique are the minimal additional component requirements, ensuring cost-efficiency, and the high noise immunity. The discharge test can be conducted during the converter turn-off and it can be fully automated, without the need to remove the capacitor or to modify the power stage of the converter. Experimental results are provided to validate the proposed methodology.