LAUSR

Aluminum electrolytic capacitors (Al-Caps) are widely used in the dc-link of ac/dc applications, however, they are one of the weakest components in power electronic converters. With the degradation of Al-Cap, its capacitance (C) decreases, and the equivalent series resistance (ESR) increases. Based on this, many efforts have been made to realize condition monitoring (CM) of Al-Caps. Unfortunately, additional hardware (including current sensors and sampling circuits), and/or powerful data processing tools are usually required, which increases the cost and would bring new reliability risks. Considering this issue, this paper presents a transient-based CM scheme for dc-link capacitors in digital-controlled boost power factor correction (PFC) converters, which does not need additional sampling devices. By analyzing the relationship between large-signal transient voltage profile and dc-link capacitance, a calculation model is established. Based on the sampled voltage and current signals used for digital control, the dc-link capacitance can be online estimated. Its feasibility is validated in simulation with a boost PFC operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Furthermore, taking a 1-kW boost PFC operating in CCM as a case study, experimental results illustrate that the estimation errors of the dc-link capacitance are less than 3.5% (error of a single test) and 1.5% (average error of multiple tests).