Noise radiation from an AC filter capacitor

The noise generated by alternating current (AC) filter capacitors on the AC side of high-voltage direct-current transmission systems is an important contributor to the total noise of converter stations. In this paper, the noise radiation and the vibration information of an AC filter capacitor is measured and analyzed with multi harmonic excitations. A boundary element model for the noise radiation prediction is established and validated using the measurement data under a typical excitation condition. Based on the prediction model, the noise contribution of different surfaces of the capacitor is calculated. It is found that the top surface and one broad surface are major contributors to the sound power. The sound power level of the capacitor can be reduced by 7.5 dB, 6.7 dB, 7.8 dB and 5.0 dB respectively at 100 Hz, 500 Hz, 600 Hz and 700 Hz when the vibration at these two surfaces is completely suppressed.