Multi-Frequency Impedance Measurement Method for DC Link Capacitor of Flexible DC Converter Valve

The DC Link capacitor is a crucial component of the sub-module in the flexible DC converter valve. Its electrical performance directly impacts the operation of the valve. Due to the complex operating conditions of the converter valve, the capacitor is susceptible to deterioration during long-term operation, leading to changes in its electrical parameters. Therefore, it is essential to find an effective multi-frequency impedance measurement method for the capacitor. This paper presents the construction of three capacitor electrical parameter measurement test platforms. The test results indicate that the offline measurement method, which uses high-voltage bridge measurement, has high accuracy. On the other hand, the online monitoring algorithm has lower cost and higher flexibility. These findings provide a research basis for the capacitor condition monitoring method.