Hierarchical robust state estimation in power system using phasor measurement units

State estimation based on phasor measurement units is essential for control and monitoring of large scale power systems. In this paper, a hierarchical robust state estimator algorithm is proposed. The proposed method has many good features. Firstly it is hierarchical, by which regional estimate estimators are working for local use, while an upper level estimator improves their estimation for local and global use. Secondly, since not all buses have PMUs, the combination of data from PMUs and RTUs is being considered for a better estimation. Thirdly, it uses a robust algorithm, to overcome the problem of bad data set. Combining robust estimators in hierarchical method is a new technique for reliable and fast state estimation. The simulation results of proposed solution are presented for IEEE 14-bus test system.