Frequency Domain Analysis and Control for Governor Stability Problem in Islanded HVDC Sending Systems

During the development process of HVDC in China,several HVDC projects are faced with the problem that the sending system may change into islanded mode.Stability problem of governor should be paid more attention in an islanded sending system since it has resulted in an abnormal frequency oscillation phenomenon in island experiments of Jinsu HVDC project.In this paper,a transfer function model was established to analyze the governor stability in an islanded HVDC sending system.Then sensitivity analysis for governor stability was given in frequency domain.A decoupling coordinated design approach of governor and HVDC frequency controller was proposed based on the sensitivity analysis results.The abnormal frequency oscillation phenomenon was analyzed and the controllers in Jinsu HVDC islanded sending system were redesigned.The analysis and design approaches were verified by the field test of Jinsu HVDC link.