Fault Detection of Converter Valve Based on the Combination of Fault Tree Analysis and Multi-Frequency Impedance Testing

Xin Tong MAO^1*Huilong Zhao¹Kangxin Cai²Baitao Zhang¹Wei Liu¹Zhiwei Liu¹Yunfei Liu¹Zhihao Xing¹Yong Lu¹Jianyong Zheng²

• ¹State Grid Jiangsu Electric Power Company Limited Construction Branch, Jiangsu, China
• ²Southeast University, Nanjing, China

To address the issue that converter valves contain numerous components in the thyristor-level damping, voltage-sharing, and power-tapping circuits and feature a complex structure, while conventional impedance testing can only provide qualitative conclusions at the valve level, this paper proposes a converter-valve fault detection method that integrates fault tree analysis (FTA) with multi-frequency comprehensive impedance testing. By applying multi-frequency small-signal excitation voltages across both terminals of a thyristor level and measuring the active and reactive power responses at multiple frequencies, a multi-objective optimization model is established with regularization terms and parameter-bound constraints to enable joint identification of key circuit resistance and capacitance parameters. The resulting parameter deviations are then mapped onto the fault tree, thereby forming a systematic diagnostic relationship among the test set, parameter variations, and fault modes. MATLAB simulation results demonstrate that the proposed method can accurately identify faulty components in the associated circuits without dismantling internal wiring, offering high diagnostic accuracy and practical engineering value.