Computation efficiency of parallel systems related to granularity and application form in power system calculations

Many techniques for enhancing the calculation speed of power system analysis by utilizing parallel systems have been proposed. However, the speedups gained in these systems have been small compared to other applications such as circuit simulation, mainly due to the smallness of the problem size of power calculations. The abovementioned studies concentrated on “space parallel computing,” and the parallel implementation granularity is therefore fine due to the inherent size of power system calculations. In this paper, we first study the effect that the ratio of data transmission time to calculation time per grain has on the speedup of total calculation. We show that the smaller ratio raises the efficiency of parallel implementation. Coarser granularity of the problem generally yields smaller ratios. Thus, it is shown that attaining a coarser granularity is important. In power system calculations, the method of time‐domain parallel computing produces larger granularity. Another application form which results in much coarser granularity is multiple case analysis. We studied the application of these parallel approaches to transient stability analysis using an MIMD (multiple instruction stream, multiple data stream) distributed memory parallel processor system. On a 16 PE system, we attained a speedup of 6.3 in time‐domain parallel computing and a speedup of up to 15.8 in multiple case parallel analysis. These values are much larger than the speedup in space parallel computing, which was less than 2.0. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 14–26, 1997