Small Signal Stability-constrained AC Optimal Power Flow: A Tractable Eigenvalue-Sensitivity Approach

To maintain the power system's small-signal stability, it is necessary to ensure all eigenvalues of the system state matrix have negative real parts. Due to the intractability of the eigenvalue expression, it is hard to directly formulate constraints on the eigenvalues. This paper transforms the constraints on eigenvalues into constraints on the eigenvalue variations based on the eigenvalue sensitivity formula and network reduction techniques. The proposed approach is validated on a 3-machine 9-bus system and a 10-machine 39-bus system. For the 3-machine system, the real part of the critical eigenvalue can be reduced up to about 21%, which broadens the stable margin.