Reliability-oriented design and control of DC-link capacitors in power converter systems

Abstract

The reliability of power converter systems has demonstrated its unique value in the context of growing renewable energy generation worldwide. As a reliability-critical electrical component, the dc-link capacitor has drawn particular attention across industries. The thesis explores various approaches to improving the reliability of dc-link capacitors. This is done by addressing several root causes of capacitors’ accelerated aging and wear-out, i.e. current and voltage ripples. The existence of these ripples also prompts the use of electrolytic capacitors, which compromises the reliability of the entire system. In addition, when interfacing renewable generators to the grid, power converters can support frequency regulation by generating virtual inertia through dc-link capacitors. However, the change of grid frequency could provoke voltage swings in the dc-link capacitors, hence shrinking their lifetime. In this thesis, several control-based methods are proposed to address the abovementioned issues. The effectiveness of these methods is verified by both simulated and experimental results.