Observability analysis of AC-DC hybrid power system

Based on the characteristics of AC-DC hybrid power system, a topological approach is proposed in this paper for the observability analysis of AC-DC power system state estimation to merging and extending observable islands. Firstly, two rules based on the solvable condition of power flow of DC system are presented to analyze the observability of DC system including multi-infeed and multi-terminal DC system. Secondly, the conception of the DC correlation coefficient of AC buses is proposed. Thirdly, the contribution of the AC interisland branches and DC interisland branches to the observability AC-DC systems is discussed in this paper. By using the idea of alternative iteration by analogy with the state estimation of AC-DC system, the procedures to merge the AC-DC systems measurement islands are presented in this paper. Numerical results show that the proposed AC-DC systems observability analysis method is valid and effective.