Start-up control of a HVDC grid based on MMC with integrating large-scale wind farms

Abstract

With the rapid development of voltage source converter (VSC) based high voltage direct current (HVDC) transmission technology, the HVDC grid will be an effective solution for large-scale renewable energy generations integration. The modular multilevel converter (MMC) is one the most promising topology for HVDC and DC grid presently. The precharge of the MMCs and start-up of DC grid are essential problems. This paper studies the sequential start-up control of the VSC-HVDC grid with wind farms integration. After the discussion of control system, the precharge principle of the MMC is analyzed. A coordinated start-up control scheme of a DC grid with integrating large-scale wind farms is presented as well as sequential start-up control methods under typical operation modes with HVDC breakers are also investigated. Cases studied are carried on a four-terminal HVDC grid model in PSCAD/EMTDC to verify the proposed schemes.