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.