Transient stability of high frequency AC power systems

Abstract

The large-signal transient stability of generators running at frequencies higher than the usual 50 or 60 Hz was investigated as a function of system frequency in a micro-grid setting. A three phase bolted fault was taken as the mechanism for inciting potential instabilities. Simple rotor angle analysis leads one to believe that higher frequency power systems are inherently more unstable than lower frequency systems, and this point is substantiated by critical clearing time (CCT) tests. But more extensive simulation-based analyses paint a different picture: if circuit breaker speed can be increased proportionally to the increase of system frequency (e.g. opening after some number of cycles, irrespective of the frequency of those cycles), then higher frequency systems can have better stability than lower frequency systems. Conversely, if circuit breaker speed cannot be increased proportionally to system frequency, then higher frequency systems might present worse stability if no other method for improving system stability is implemented.