Study on the Tangent Calculation Method of Frequency-domain Dielectric Loss Angle Based on Improved Kalman Filtering Algorithm

Frequency-domain dielectric spectroscopy realizes the dielectric loss detection within the range of 1 mHz-10 kHz, which can detect the insulation condition of electrical equipment effectively. The calculation method of voltage and current phase difference is the core algorithm of dielectric loss detection. The existing algorithms have large errors when processing low-frequency current signals with low signal-to-noise ratio (SNR). In this paper, a new algorithm is proposed to improve the accurate of the dielectric loss angle. Firstly, the multiple full-period current signals are extracted according to the applied voltage signal. The full-period signals are superimposed, and then calculating the apparent amplitude. Secondly, the apparent phase is calculated by the least square algorithm with the superimposed signal, then, reconstructing current signal by the apparent amplitude and apparent phase. The reconstructed signal and superposed signal are used as the theoretical and observation signal, respectively, for Kalman filtering. Finally, the filtered signal is taken as the initial signal to repeat the reconstruction and filtering steps. When the error between the filtered signal and the reconstructed signal is less than a certain value, the accurate amplitude and phase angle are obtained. The proposed algorithm was verified by simulation and experiment, the results show that the measuring accuracy of the dielectric loss tangent can reach 99%, and with the standard model the error is only 0.171%.