An investigation into the placement of norm-bounded perturbations to analyze stability robustness of power systems

In the analysis of the stability robustness of power system controllers, norm-bounded perturbations are used to account for the uncertainty in the linearized mathematical models of the various power system components. Uncertainty exists in the following components considered in this paper: (1) the synchronous machine model and its reference frame transformation and (2) an aggregate induction motor load connected in parallel with a static load. This paper investigates several alternative perturbation options to account for the uncertainty associated with changes in the power systems´ operating conditions due to load variations. Numerical results for a four-machine, two-load test system are obtained and compared with those using nonlinear time simulations