A Simple and Cost-Effective Method for Condition Monitoring of Inverter DC-Link Film Capacitors Based on Capacitance Variation

DC-link capacitors are among the most critical components in traction inverters, with a high likelihood of failure. Effective condition monitoring (CM) of these capacitors is crucial for improving converter reliability and preventing catastrophic failures. This article presents a cost-effective and reliable methodology for evaluating the health state of film capacitors used as dc-link in traction inverters. The proposed approach uses a controlled discharge test to track capacitance variations over time, which can be used as an indirect indicator of the capacitor’s health state. Key advantages of this technique include the minimal additional component requirements for cost efficiency, strong noise immunity, and high precision. Furthermore, the proposed aging detection test can be fully automated without requiring the removal of the capacitor or modifications to the converter’s power stage. Experimental results are provided to validate the effectiveness of the proposed solution.