Diagnosis method for open-circuit fault of cascade-STATCOM based on analytical model

The reliability of the power switch will directly influence the safety and reliability of STATCOM (Static Synchronous Compensator). However, it is difficult to detect the open-circuit fault because the output current and voltage are changed slightly in cascade-STATCOM. In this paper, we apply double Fourier transform of the switching function to analyze the distinction between normal fault and open-circuit fault, and propose that the open-circuit can be diagnosed by detecting the DC capacitor voltage. Moreover, this method resorts no additional sensors. The discriminant is also given in the paper. Simulation examples are presented in the end to illustrate the correctness of the theoretical result.