HVDC modulation principle and supplementary controller design method of non-parallel AC/DC system

Aiming at non-parallel AC/DC systems, this paper studies the mechanism in system structure for HVDC power modulation to suppress low frequency oscillation. Through the equivalent circuit analysis of a typical non-parallel AC/DC system, the key factor that influences the HVDC modulation effectiveness is revealed. The paper introduces the extended residue ratio as the selection rule for the input signal of the HVDC supplementary controller. The design method for the HVDC supplementary controller is presented based on the phase compensation of the residue. Finally, a case study and an actual project study in China Northwest Power Grid are presented.