Harmonic cancellation for HVDC systems using a notch-filter controlled active DC filter

A notch-filter controlled active DC filter is applied to suppress the current harmonics in a high-voltage-direct-current (HVDC) system. The design principle of the notch filter controlled is discussed and the sensitivity and stability of the proposed control scheme are analysed. Simulation results obtained show effective and robust cancellation of unwanted harmonics on the DC transmission line and demonstrate that the controlled outperforms the conventional proportional+integral (P+I) based approach. Simulation also shows that the control scheme is insensitive to the changes of AC system frequency