An Online DC-Link Capacitor Condition Monitoring Method for CHB-Type SVG

Cascaded-H-bridge (CHB) based static var generator (SVG) is a key equipment in modern power system. The dc-link capacitor is a vulnerable component, which restricts the overall reliability of CHB-SVG system. Therefore, in this article, an application-oriented dc-link capacitor condition monitoring (CM) method is proposed. There are two main steps: first, the accurate capacitance value of one reference module is calculated under a carefully designed charging transition mode; second, the numerical relationship of the capacitance value in each module is established by basic power equations. Then, the health condition of all the rest capacitors could be acquired with the established numerical relationship. There are no extra sensors involved, and the normal operation of converter is not affected during CM. Simulation and experiment verify the effectiveness of the proposed method.