Estimation of interarea modes in large power systems

This paper presents a new method to estimate the interarea modes in large power systems. The method is based on the assumptions that the interarea modes in the simplified model of the system are one-to-one corresponding to the interarea modes in the detailed model of the system, and the general characteristics of the mode shapes of the two corresponding interarea modes are the same. Based on these assumptions, the method is divided into two stages. In Stage A, the frequencies, the mode shapes and the participation factors of all the interarea modes are calculated in the simplified model by the QR method. In Stage B, the accurate frequencies and the damping ratios of the interarea modes are estimated in the detailed model by the Prony method, according to the priori knowledge of these interarea modes obtained in Stage A. The proposed method can identify all the interarea modes in large power systems and is convenient to be implemented in the professional softwares such as PSS/E. The effectiveness of the method is verified in the 4-machine system, the IEEE 39-bus system and a large system in China.