An Online Monitoring Scheme of DC-Link Capacitor's ESR and C for a Boost PFC Converter

As electrolytic capacitor is apt to fail in power converters, it is very important to monitor its electrical parameters, mainly the equivalent series resistance (ESR) and capacitance (C). A novel noninvasive online monitoring method of dc-link capacitor's ESR and C for boost power factor correction converter is proposed in this paper. By analyzing the capacitor voltage ripple which is composed of that of ESR and C, the calculation model is founded, which shows that instead of additional current sensor, only two values of capacitor voltage in particular moments within a line cycle need to be sampled for the calculation of ESR and C. The schematic of the monitoring system together with the design considerations of the trigger circuit, the isolated voltage amplifier, and the isolated current amplifier, is described in detail. The experimental results show the effectiveness of the method.