Observability analysis in power system state estimation based on the solvable condition of power flow

In order to overcome the difficulty in merging and extending observable islands formed by branch flow criteria by using injection measurements, a novel theory and a new topologic algorithm are proposed for observability analysis in power system state estimation. By the idea of equivalence, the nodes of interior network in the islands are ignored during the combination of islands. The sub-networks formed by branches connecting different islands and their terminal nodes called boundary nodes are taken as our research objects. Several rules and the solvability condition of power flow are considered to judge the combination of islands. The validity and efficiency of the method are verified.