Monitoring Metallized Film Capacitor Health: A Method for Estimating Capacitance Amid Short-Term Failures Due to Self-Healing

Metallized film capacitors (MFCs) are valued for their ability to withstand high-electric-fields, yet they face short-term failure risks when subjected to overvoltage-induced self-healing (SH). This paper presents a monitoring method designed to address the challenges posed by multiple instances of SH in pulsed power applications. Traditional capacitance estimation using sampled current during SH is hindered by the significant arc current. To address this, the study explores the dynamic interplay between sampling current, arc current, and MFC current throughout the SH process. The introduction of Kalman filtering effectively mitigates the impact of noise signals on capacitance monitoring during the short-term cumulative discharge process of SH. Experimental and simulation results attest to the efficiency of the proposed approach, demonstrating an estimation error of less than 1%. Furthermore, a thorough structural analysis of MFCs demonstrates that the proposed method can effectively identify the transition from isolated, safe SH behavior to clustered, disruptive SH events, thereby enabling timely intervention to prevent severe damage.