Non‐Intrusive Online ESR Estimation for Interleaved Buck Converters Based on Virtual Signal Construction and DWT

ABSTRACT

Interleaved DC–DC converters are widely applied in modern power conversion systems for their high power density, low input current ripple, high reliability and fast dynamic response. However, the reliability of these converters is critically affected by aluminium electrolytic capacitors, which are prone to degradation over time. The equivalent series resistance (ESR) of capacitors serves as a key indicator of their health. This paper proposes an ESR estimation method for the aluminum electrolytic capacitors in a three‐phase interleaved Buck converter, based on virtual‐signal construction and discrete wavelet transform. Virtual voltage and current signals are reconstructed from the sampled output voltage and inductor current using an algorithm based on rising and falling slope trends. To capture ESR‐related frequency components, the discrete wavelet transform is applied to extract high‐frequency features, and the ESR is determined as the ratio of the dominant wavelet coefficients of the virtual voltage and current signals. Operating in the time–frequency domain, the proposed method exhibits superior robustness against sampling noise and dynamic load variations compared with the conventional time‐domain technique. Furthermore, it eliminates the need for any extra current sensors for measuring the capacitor current. In addition, simulation analysis and hardware experimental results validate the accuracy and robustness of the proposed approach under various operating conditions.