Estimation of inter-area modes during ambient operation using the Eigen-system realization algorithm

Inter-area electromechanical oscillations with low or even negative damping may pose great threat to the power systems. It is critical for the operators to be aware of the properties of the interarea electromechanical oscillation modes. In this paper the Eigen-system realization algorithm (ERA) is used to estimate the parameters of the interarea modes, including the frequency, damping ratio, and mode shape, during ambient operation of the power system. Two ERA based methods, namely the RDT-ERA, and the NExT-ERA, are evaluated, in terms of their robustness to the measurement noise and to the random ambient excitation. The methods are validated using simulated data from the two area four machine system as well as real PMU measurements from Sichuan power grid.