A W-matrix based fast decoupled load flow for contingency studies on vector computers

The authors deal with an application of the inverse factors method (W-matrix method) to a fast decoupled load flow procedure for steady-state contingency analysis. The W-matrix method, originally developed for the solution of sparse sets of linear equations on multiple instruction/multiple data (MIMD) computers, can also be made effective for vector computers. The recurrence problem is overcome by reordering the addition operations required in a forward and backward solution. Matrix partitioning is employed to find the best tradeoff between the number of fill-ins added to the W matrix and the increased efficiency of vector operations achieved through a reduced number of partitions. The effect of different bus ordering algorithms on the partition number is also considered. Operation reordering is employed to make the bus power computation phase very fast in comparison to traditional bus-wise calculation. Tests were performed on the IEEE 118 bus system, some different configurations of the Italian EHV system and a European equivalent network with up to about 700 buses using a 4-CPU CRAY Y-MP8/432 and a 4-CPU Alliant FX/80 computer