Online estimation scheme of output capacitor's ESR and tanδ for Buck converter

Aluminium electrolytic capacitor (AEC) is one of the most age-affected components in power electronic converters, and its reliability has been a major concern. As the growth of service life, the equivalent series resistance (ESR) and dissipation factor (tan delta) of AEC increase due to the loss of electrolyte. Therefore, the online ESR estimation is critical for condition monitoring of AEC. Based on the inductor current ripple and capacitor voltage ripple, ESR calculation model and tan delta calculation model are derived, which are applied to both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). To implement the proposed scheme, a detailed solution based on wavelet transform denoising (WTD) is presented. The superiority of the proposed ESR identification scheme in consideration of sampling noise is verified. The proposed ESR estimation method can also be used in the case of non-linear loads such as converter load. The tests are carried out for capacitors with different ESRs. Simulation and experimental results verify the effectiveness of the method.