Global state estimation for whole transmission and distribution networks

Traditionally, transmission and distribution state estimators are studied and developed separately. But lots of large cities have their hybrid transmission and distribution networks. In order to face keen competition in market, the requirement of coordinated operation between transmission and distribution systems is now here. Therefore, in order to balance the boundary mismatch between the transmission and distribution network models existing in the results of traditional state estimation methods, the transmission and distribution networks are studied as a whole in this paper. The weighted least squares (WLS) model for global state estimation (GSE) is presented for estimating the global consistent state in the whole network. A novel master-slave-splitting (MSS) iterative method is developed for solving the hybrid GSE problem. In the proposed method, the GSE problem of large scale is split into a transmission state estimation and lots of distribution state estimation sub-problems, which supports on-line geographically distributed computation. In order to fit the different features between transmission and distribution networks, each sub-problem can be solved with different algorithm. Several case studies are carried out, and the accuracy, convergence, efficiency and reliability of the proposed method are validated.