| Abstract: | Load-flow calculation on electric power systems is one of the most fundamental analyses in system operation and planning. There are many reasons to calculate load-flow solutions, and the contingency evaluation is a representative one. In contingency evaluation, it is necessary to repeat load-flow calculation for tremendous patterns depending on branch or generation outages. Then, computing efforts are generally very heavy. Thus various techniques have been proposed to reduce computing time, especially by adopting equivalencing for external network. On the other hand, the network equivalents techniques also become important at present from the viewpoint of the necessity of decentralized monitor and control on bulk power systems. This paper describes a newly developed method of load-flow equivalents based on the Ward equivalent for both direct (dc) solution and (ac) solution. Numerical results also are shown to clarify the accuracies and practicality of the proposed method through the comparison of the representative REI approach. |
