On-line transient stability evaluation by system decomposition-aggregation and high order derivatives

An on-line transient stability evaluation method is presented in this paper. Under some classical assumptions, the change of generator rotor angles during the transient period is described by a set of second order differential equations. This set of equations is solved by single-step high order derivative explicit integration. A new system decomposition-aggregation technique is proposed to decompose the power system into subsystems and then to aggregate the subsystems by interconnection boundary conditions. Based on the aggregation model, the calculation of high order derivatives is quite efficient to reduce the requirements of both computer memory and computational time for a large scale power system. The relation of memory and execution time requirements to the system decomposition is discussed. Two systems, the IEEE 118 bus test system with 34 generators and a 293 bus system with 63 generators, are tested by simulation on a CDC-6600 computer. The results demonstrate that the proposed method is effective for on-line application and may be faster than Liapunov's direct method.