Multi-Machine Power System Transient Stability Research Based On Normal Form Theory

The transient stability of power system is one of the hot topics in studying power system at present. In calculating the critical clearance time in electric power system, there are lots of merits and limitation in the methods of the step by step time-domain method (SBS) and transient energy function method (TEF). Especially in the multi-machine power system, the transient stability region is more difficult to be determined by the method of TEF. According to the theory of nonlinear dynamic system, the stable boundary is the union of the stable manifolds of the unstable equilibrium points on the stable boundary. The paper elaborates the normal form theory of vector fields and promotes the second-order expression of normal form, and introduces the concept of partial manifolds and how to calculate it on CUEP (Controlling Unstable Equilibrium Point) of power system. To transform the nonlinear power system into a linear system on CUEP of post-fault multi-machine power system based on normal form theory, according to the stable subspace of the linear system we can get the stable manifolds of the nonlinear power system. So, a new stable region and its detailed expression are obtained. The calculation results show its correction of such calculating method, which proves that it is a effective way in researching transient stability of system power.