Impedance-Based Method for Offline Aging Assessment of Electromagnetic Filters and DC-Link Capacitors in Traction Inverters

Ensuring electromagnetic compatibility among the various components of an electric vehicle is a critical requirement. Additionally, minimizing voltage ripple on the DC bus, induced by the switching operations of the inverter's transistors, is essential for maintaining system stability and performance. To meet these requirements, a passive network consisting of the DC-link capacitor and an electromagnetic filter is connected on the DC side of the inverter. The aging of these components leads to a deterioration in the filter's performance, a reduction in service life, and potential non-compliance with electromagnetic compatibility standards. Moreover, it is important to emphasize that the combination of the EMI filter and the DC-link capacitor represents one of the most critical components of the inverter in terms of aging and reliability. This paper presents a novel method that enables the simultaneous aging assessment of these components based on the impedance measurement of the whole system. It allows for detecting aging in the different branches of the passive network and predicts this aging based on capacitance variation. Individual testing of the components is not required, as it suffices to have access to the DC terminals of the converter without the need to disassemble or separate the components. This method has been experimentally validated using two inverters. The first one has a generic structure and is currently at the prototype stage, while the second is a specific industrial traction inverter for electric vehicles.