Fast Initial Estimation of Power System Eigenvalues

Abstract

Up to now, the AESOPS algorithm is still the only effective and reliable tool to calculate the eigenvalues of very large power systems. But it needs good initial guesses at each eigenvalue and the corresponding generator which participates in that mode most significantly.In large power systems, where many eigenvalues can be very close to each other, the results of the AESOPS and all derivative methods become very sensitive to those guesses. Sometimes, the same eigenvalue may be found in many places, while a nearby one would not be identified at all. This project aims at solving the above problems. The basic idea is that the oscillation modes are the same for both a small disturbance and a severe short circuit at a generator bus.A recently developed direct method called the Extended Equal Area Criterion can precisely and very quickly identify the oscillation modes under large disturbances without any additional computation to the transient stability assessment. For each mode identified above, using the concept of Partial Center of Angles equivalence used in the EEAC for transient stability analyses, we have an equivalent two-machine system, further an equivalent one-machine-infinite-bus system. The eigenvalues of the system can be calculated analytically at a negligible computation price and used, together with the critical group identified, as a good initial guess for the AESOPS algorithm. Simulations in a Chinese regional system and the New England system fully confirm the above claims.