Full Tuning of Double Input Power System Stabilizers via Surrogate Optimization

This paper deals with the optimal tuning of Power System Stabilizers (PSSs). The considered PSS is the widely adopted double input IEEE type PSS2B. The objective is to optimally define the PSS parameters to simultaneously place the system poles within a prescribed area defined by a maximal real part and a minimum damping factor and to minimize the phase lag between system frequency and generator terminal voltage, which has a strong impact on the damping of inter-area oscillations, according to the Italian Transmission System Operator expertise. This goal is obtained by minimizing a suitably defined cost function evaluated after the computation of a linearized model of the generator connected to an infinite bus external grid under several operating conditions, in terms of both generator working point and grid impedance. The result is a highly nonlinear optimization problem, which is solved via Surrogate Optimization. Compared to the current literature, the proposed procedure considers the tuning of every parameter of the PSS, comprising both the terminal branch and the initial section, which is intended for a pre-filtering action. This part includes additional time constants that can influence the transmission system dynamic response. Simulation results prove the effectiveness of the proposed procedure.