Evaluation of subsynchronous oscillation of Xiluodu right station - Guangdong double line ±500kV DC transmission project

HVDC transmission system may cause subsynchronous oscillation (SSO) in thermal generation units near rectifier station. Based on Xiluodu right station - Guangdong double line ±500kV DC transmission project and system conditions near rectifier station, the risk of subsynchronous oscillation (SSO) instability in nearby thermal generation units in Weixin Plant and Zhenxiong Plant is evaluated. In the first step the unit interaction factor (UIF) analysis method is used to seek out the operation conditions in which there are large turbine-generators prone to SSO instability. And the time-domain simulation method is used to further analyze the selected cases with UIF more than the threshold 0.05 in detail. The results shows that there is little risk under the nominal DC voltage conditions, but significant risk under the reduced DC voltage conditions for Xiluodu Project in 2013. SSDC is designed to mitigated the SSO instability for Xiluodu Project. Time domain simulation tests have been done to verified the SSDC effectiveness.