Study on impedance-frequency characteristics of HVDC filter commutate converter

This paper focuses on the mutual relationship between ac and dc system, aims at the HVDC´s stability, presents the circuit topology structure of filter commutated converter (FCC), which has abilities of and reactive-load compensation equipments in the valve side, the stability of system has been improved and harmonic instability could be avoided more efficiently as a result. Then the equivalent dc impedance and equivalent ac impedance of FCC viewed respectively from dc side and ac side are determined based on modulation theory. In the proposed method converter commutation course and ac system are considered when calculating equivalent dc impedance, while dc system and the opposite ac system are considered when calculating local equivalent ac impedance. A dc transmission platform is used to verify advantages of FCC compared with traditional converter, the impendence-frequency characteristics obtain from the PACAD/EMTDC simulation and calculation results agree w.ell with each other in a wide frequency area.