  This paper proposes a graph computation based sequential power flow
calculation method for Line Commutated Converter (LCC) based large-scale AC/DC
systems to achieve a high computing performance. Based on the graph theory, the
complex AC/DC system is first converted to a graph model and stored in a graph
database. Then, the hybrid system is divided into several isolated areas with
graph partition algorithm by decoupling AC and DC networks. Thus, the power
flow analysis can be executed in parallel for each independent area with the
new selected slack buses. Furthermore, for each area, the node-based parallel
computing (NPC) and hierarchical parallel computing (HPC) used in graph
computation are employed to speed up fast decoupled power flow (FDPF).
Comprehensive case studies on the IEEE 300-bus, polished South Carolina
12,000-bus system and a China 11,119-bus system are performed to demonstrate
the accuracy and efficiency of the proposed method
