Graph Computation based Power Flow for Large-Scale AC/DC System

In this paper, a graph computation based power flow algorithm is introduced to solve large-scale AC/DC hybrid systems with multi LCC (Line Commuter Converter) based DC grids. The proposed approach is to improve the computational efficiency of constructing related matrices and getting power flow results without changing the conventional sequential iteration method. The hybrid system is modeled as a graph of vertices and edges with info of topology and parameters, thus local computation could be done independently for like formulating mismatch vectors of ΔP, ΔQ, Δθ, ΔV and matrices of B', B", only with parameters on its linked edges and adjacent vertices. Then by taking advantages of hierarchical parallel computing, the FDPF (fast decoupled power flow) of AC system, calculation of DC grids and mismatch comparing for each iteration of the sequential method could be done parallelly. This method is implemented on a graph database platform, and tested on IEEE 300-Bus, modified South Carolina 500-Bus system and a Chinese system to verify the accuracy and time-saving performance.