A High-Accuracy Capacitor Condition Monitoring Scheme at Low Sample Frequency Based on Improved Current Reconstruction Method

This article proposes a non-intrusive scheme for real-time monitoring of the dc-link capacitor condition in an ac/dc converter system under a low sample rate. The method takes advantage of voltage fluctuations on the dc side resulting from changes in system load, without the need for additional hardware equipment or the injection of harmonic components. The core technology of the scheme is a current integral reconstruction method based on linear fitting which improves monitoring accuracy at low sampling rates. The article begins by introducing the ac/dc converter system targeted by this scheme. It then proposes an improved current reconstruction method and a suitable equivalent capacitance calculation method, which is verified through simulation. Finally, an experimental prototype is constructed to demonstrate the feasibility of the proposed method (PM).