Study on a coordinate control strategy of multi-HVDC links to improve transient stability in China Southern Power Grid

Since High Voltage Direct Current (HVDC) has overload-ability and quickly adjustable features, by rapidly modulating HVDC power in an AC/DC grid, HVDC can compensate power imbalance between sending-grid and receiving-grid and enhance transient stability after a heavy disturbance. In previous studies, the feasibility and effectiveness of an automatic real-time control strategy of HVDC in a single HVDC link system have been discussed. This paper focuses on the application of this control strategy in a multi-HVDC links system and the mutual influence between different HVDC links. Simulations in a transient simulation model of China Southern Power Grid (CSG) by the EMTDC/PSCAD software show that the coordinated control of multi-HVDC links contributes a significant improvement of the system transient stability after a large disturbance. When all of the four HVDC lines in CSG involve in the coordinated control, the stability of the system will be most obviously improved after a large disturbance. Meanwhile the mutual influence between the HVDC links is very limited.