Noninvasive Technique for DC-Link Capacitance Estimation in Single-Phase Inverters

With increased penetration of renewable sources, single-phase grid-connected converters are finding increased applications. Condition monitoring of dc-link capacitor is required for preventive maintenance, which improves the reliability of the overall system. Significant literature on condition monitoring techniques for capacitor is applicable to three-phase converter or three-stage ac/dc/ac converters. Recent publications on health monitoring in single-phase converters require either configuring/operating converter in a specific mode or quantify aging of aluminum electrolytic capacitor (AEC) in variables other than equivalent series resistance and capacitance of AEC. This letter proposes an online noninvasive technique to estimate the capacitance of dc link, which is a better indicator for health assessment of the AEC. Estimation of capacitance is done using the available measurement for the converter control and is implemented in the same digital controller used for control of converter. Simulation and experimental verification are carried out on a prototype of single-phase grid-connected system.