Comparison of participation factor method and selective eigenvalue computation for voltage stability analysis

The problem of voltage stability is closely related to load dynamics. In this paper, voltage instability due to small disturbances is analysed using eigenvalue method taking into account the dynamics of the generators and the load. Participation factor analysis is employed to find out the participation of different state variables in eigenvalues of the system. In small disturbance voltage stability studies, the eigenvalues of importance are those corresponding to the loads. The paper discusses how the method of selective computation can be employed to quickly compute the eigenvalues associated with loads. A study is performed to determine whether the selective computation of eigenvalue performed by retaining a state variable results in the eigenvalue in which the retained state variable has maximum participation. Voltage instability, when eigenvalue associated with load is positive, is demonstrated using simulation of two test systems subjected to a small disturbance.