Abstract
In the direct solution of Y matrix of electric power systems, short circuited branches (ST branches) such circuit breakers and line switches have been generally approximately modeled by small resistances so far. However, when those small resistance elements are included as Y matrix elements, the analytical accuracy is feared due to excessive round-off errors that are caused in factorization process for Y matrix.
A new method of the direct solution of Y matrix including the ST branches is proposed in this paper. As the purpose of factorization is to obtain the node voltages efficiently, the configuration of factored matrix does not need to correspond to that of Y matrix. In the proposed method, the factored matrix is formed in which each ST branch is grouped by same voltage at the connecting ST nodes, and ST nodes except ST retained node are ordered first. Accurate each factored term for these ST nodes which are ordered first can be derived by taking exact zero resistance in conventional factorization procedure. By introducing the new factored terms above, not only the problem of the excessive round-off errors is overcome, but also the sparsity of the factored matrix can be improved.
Demonstrative result is presented for large network model in order to verify the practicability of the proposed method.
