小开机方式下滇西北送广东±800 kV特高压直流被动进入孤岛过电压研究

Study on Overvoltage of ±800 kV Northwest Yunnan-Guangdong UHVDC Project Under Isolated Island Mode With Small Amount of Hydropower Generators

为使滇西北送广东±800 kV特高压直流输变电工程投运后尽快满送功率,在送端电厂机组长期处于开机量较小的情况下,需云南主网增加外送滇西北直流功率。针对送端小开机方式下直流被动进入孤岛后的系统过电压展开了风险分析,提出了提升直流输送能力的过电压抑制措施并进行了现场调试验证。计算表明:若以传统的过电压保护策略,送端电厂开2机和5机情况下直流输送功率极限分别为1500 MW和3300 MW;采取直流被动进入孤岛后采用先全切交流滤波器组、切断成功后延时闭锁直流的过电压抑制措施后,可以将直流输能力提升至额定功率,并使系统过电压水平满足要求。

To achieve full power transmission through the ± 8 0 0 k V N o r t h w e s t Y u n n a n-G u a n g d o n g U H V D C transmission and transformation project as soon as possible after putting into operation, it is necessary to increase the power output from Yunnan power grid to this project due to a small amount of generators putting into operation at the hydropower stations for a long period. Overvoltage risk analyses were carried out after the DC system entering into isolated islands operation mode, and overvoltage suppression measures to improve the DC transmission capacity were proposed and field commissioning verification was carried out. Calculations show that if the traditional overvoltage protection strategy is adopted, the DC transmission power limits of would be 1500 MW and 3300 MW with two generators and five generators putting into operation at the hydropower stations, respectively. After taking the overvoltage suppression measure, which is cutting off all AC filter banks after the DC system entering into isolated island operation mode, and then blocking DC operation, the over-voltage will always meet the requirements, even if under rated DC power.