On structure preserving control of power systems

Control designs based on Geometric Feedback Linearization (GFL) and the so-called Direct Feedback Linearization (DFL) technique for power system stability control are presented and compared. The physical integrity of the state space description of a classical single machine infinite bus (SMIB) power system model is preserved with the application of DFL in designing a robust excitation-voltage regulating control system. Firstly, the conflict of simultaneous angle stabilization and voltage regulation is studied. Then linear techniques on the linearized system are applied to design stabilizing feedback gain coefficients for the nonlinear excitation loop. It is shown that GFL results in a coordinate mapping for which the feedback loop stabilizes the angle while the DFL is seen to offer considerable flexibility in designing controllers for all relevant variables. The results emphasize the difference between geometric and direct feedback approaches and provide insights towards nonlinear control theory applications in power systems.