Detection approach for detuning fault component of three-tuned DC filter

The three-tuned filter has obtained the more and more application in the high and ultra high voltage direct current transmission project. The impedance-frequency characteristics of the three-tuned DC filter was investigated in the paper. The offset formula of the harmonic impedance under the variation of the parameters of three-tuned DC filter was derived. It revealed that the ratio between harmonic impedance offset at each filter's resonant frequency had no relation with the filter parameters offset. Then, based on the ratio between harmonic impedance offset at different filter's resonant frequency, a detection approach for the detuning failure component of the three-tuned DC filter was proposed. In addition, example analysis based on the three-tuned DC filter in Yunnan-Guangdong UHVDC project was provided. The extensive simulation by ATP-EMTP software indicated the simplicity and efficiency of the detection approach.