Reasearch On Z-Matrix Building And Modifying Algorithm For Electric Power Network Including Mutual Induction

With the rapid development of the scope and complexity of electric power network, the dealing with the zero-sequence mutual inductance between transmission lines and large quantity of equivalent grounded-branches on the building and modifying of Z-Matrix which brings difficulties. By studying the algorithm of forming Z-Matrix, an improved algorithm using transitional matrix to form bus impedance matrix (Z-matrix) is presented, based on the power system with large quantity of mutual inductance and grounded-branches. According to discussing the relationships among branch current, branch voltage, node voltage and current injection in network without grounded-branches, three relational matrices are built, which are node voltage vs. branch voltage matrix Mvu, node voltage vs. branch current matrix MVI and branch current vs. current injection matrix MIJ. Corresponding transitional matrices are amended after grounded-branches are equivalent to bus current injection. Extended node voltage vs. current injection matrix MVJO is formed. Z-matrix is gained by using kron reduction method to calculate the blocked MVJO.As the situation of adding or cutting branches, the paper make a thorough study in the algorithm of Z-Matrix modifying, and demonstrates the main process of using improved algorithm to modify Z-Matrix in detail. In the situation of shorted at non-extreme, modifying computation as the shortcircuit including mutual inductance is put forward.The main process is presented and a lot of examples show that the improved algorithm is effective and universal. It will be a new sustaining tool for further research by using Z-matrix.