Sending end frequency and voltage under islanded operation mode of HVDC transmission system

Some large coal bases send power energy by high voltage direct current (HVDC) lines. Because the sending end systems of HVDC Transmissions are made up a few thermal power units, the sending end systems become island probably. It is necessary to research the frequency and voltage for these weak sending end islanding systems. In the paper, take Hu-Liao DC project as an example to carry out the researches. The first one is the change of the DC plan for the external-transmission, the second one is monopole emergency switch off sequence (ESOF) occurring in DC project, and the third one is three-phase short circuit fault occurring in the sending end. The results showed the frequency and voltage meet HVDC transmission. The control strategy can provide a reference for the power dispatching and production department.