Global Structure Analysis of a Class of Power System with Zero Characteristic Root
The system with a zero characteristic root has had a more detailed discussion on global structure and the existing conditions of limit cycle. Through discussing the nature of the high-order singular point with two zero characteristic root of five order system , we will get the global structure of the system.
X. M. Cheng "Global Structure Analysis of a Class of Power System with Zero Characteristic Root", Advanced Materials Research, Vols. 463-464, pp. 945-948, 2012