Frequency Control for Islanded System at Sending Terminal of HVDC Power Transmission from China to Mongolia

The electric power generated by pithead power plants in Mongolia will be transmitted to load center of North China power grid, i.e., Beijing―Tianjin―Tangshan area, through China-Mongolia HVDC project. The isolated island operation mode is used for the AC power system at the sending end of HVDC system. To cope with the rapid frequency increase at sending end caused by monopole block of HVDC system or post-fault operation condition of AC system at receiving area, the effectiveness of the measures to solve frequency increase at sending end, such as security and stability control system, generator over-speed protection control and DC additional control is researched, and a control scheme coordinating above-mentioned measures is proposed. Simulation results show that the frequency stability can be well solved by comprehensive control means and the stability of power grid can be enhanced.