Identification of critical modes in power systems

An analytical method to identify the critical modes in electric power systems is presented. The troublesome, or critical, modes are identified as the eigenvalues that contribute the most to a quadratic performance index. This performance index measures the transients in torque angle and speed. Explicit expressions for these contributions are derived, and a critical index for any eigenvalue is developed. Three examples are given to show that the proposed method is promising, and that in these particular cases it gives better results than some well-known methods. Two of these examples are multimachine power systems available in the literature