The rectified signal is filtered. The

The rectified signal is filtered. The DC side filters include both a low pass filter (to remove the ripple content) and notch filters tuned to the fundamental and second harmonic components. The notch filters are provided to avoid the adverse interactions of SVC caused by second harmonic positive sequence and fundamental frequency negative sequence voltages on the SVC bus. For example, second harmonic positive sequence voltages at the SVC bus cause a fundamental frequency component in the rectified signal that results in the modulation of SVC susceptance at the same frequency. This in turn (due to amplitude modulation) results in two components at side band frequencies (0,2f) in the SVC current. The dc component can result in unsymmetric saturation of the SVC transformer and consequent increase in the magnetization current containing even harmonics. It has been observed that this adverse harmonic interactions between the SVC and the network can result in large distortion of the SVC bus voltage and impaired operation of SVC (termed as second harmonic instability).