直流工程用于远离主干网架的水电站或火电厂的电力送出时，送端交流系统形成相对独立的“孤岛”。利用实时数字仿真器和控制保护系统SIMATIC TDC，对云南—广东特高压直流工程孤岛运行方式下的直流频率控制功能进行了仿真分析。针对在仿真过程中发现的频率控制功能所存在的缺陷进行了分析，提出了改进措施，并通过仿真验证了改进措施的有效性。

When the power is transmitted from large hydropower station or thermal power plant located far away from the main power grids in HVDC project, the AC power system at sending end forms an island system. In Yunnan-Guangdong UHVDC transmission project, the DC frequency control function in island operation mode is simulated and analyzed by real-time digital simulator and the control&protection system of SIMATIC TDC. In addition, the shortcomings of the frequency control functions found in the simulation are analyzed, and the practicable improving measures are given. It is proved by the simulation that the improved measures are effective.