| With the advantages of rapid controllability, suitability for grid-interconnection, savingthe transmission-line corridor, High Voltage Direct Current (HVDC) Transmission havedeveloped fast in nation-wide power grid construction in recent years. Yunnan-Guangdong±800kV UHVDC(Ultra HVDC) transmission project and Xiangjiaba-Shanghai±800kVUHVDC transmission project have been put into operation since June and July2010respectively, which opens a new page of the UHVDC development in China.The rectifier station of HVDC often locates in the Northwest or Southwest regions,which is rich in natural resources. The power grid in these regions is usually relatively weak.Lots of researches show that HVDC adopting islanding operation mode can increase thepower transmission limits, and avoid transferring power to the weak AC network under DCfaults. The system security and safe control strategy can be simplified as well. So theislanding operation mode will be one of the normal operation modes of HVDC.In this thesis, using the real time digital simulation and BPA, Yunnan-Guangdong±800kV UHVDC project is studied as reference object. The static and dynamic characteristicsof the UHVDC in islanding operation mode are studied in the paper. The Specific studiesinclude the following aspects：(1) The operation mode of UHVDC transfers from AC-DC parallel to islanding operation.The AC bus bar rectifier is not connected to the AC main network, only connecting to thepower plant with transmission line. With different control strategies, the influence ofUHVDC operation mode transferring is studied.(2) Static voltage stability of the islanding operation system is analyzed. The staticvoltage stability limit is calculated, as well as the various typical operation mode stabilitymargin.(3) Dynamic characteristics of the islanding operation system is analyzed. Differentfaults of the islanding operation system are simulated, such as the AC system faults ofrectifier or inverter, generators faults of the islanding system, DC system block, etc. Thepaper studies the islanding system recovery process and the control system dynamic response,as well as the security control strategies. |
PDF Full Text Request