The impact of series compensation capacitor on the LCC-HVDC system stability

Series capacitor compensation technology can significantly increase the transmission capability, so it is widely used in long-distance high voltage power transmission. At the same time, there is a risk of inducing subsynchronous and super-synchronous oscillation. The impedance-based analysis method is an effective method to study such phenomenon. This paper investigates the stability problems existing in the line commutated converter based high voltage Direct Current (LCCHVDC) transmission system including series compensated transmission lines. The input impedance model of the LCCHVDC system connecting with the series compensation capacitor and considering frequency coupling effect is established. Then based on the impedance analysis method, the influences of series compensation ratio and transmission power on LCC-HVDC impedance characteristics and system stability are analyzed. Finally, the detailed circuit simulation model is established in Matlab/Simulink to verify the accuracy of the model and the correctness of the stability analysis results.