Robust design and coordination of multiple damping controllers using nonlinear constrained optimization

This paper proposes a design approach for power system stabilizing controllers based on parameter optimization of compensators with generalized structures. It shows that a selective modal performance index is an improved measure of the stabilizing effect of a given design, although its blind minimization can end in a useless local minimum. Adding stability, sensitivity and robustness constraints greatly improve the engineering significance of the resulting design. The development is fully multivariable and remains sufficiently general to apply equally well to a feedback or cascade stabilizer, with any type of input signal or transfer function structure. Three examples are used: a robust PSS design for a single machine-infinite bus system with multiple operating points; multiple PSS coordination for a large system; and a coordinated design of four PSSs for the Kundur's two-area test system. All results show good prospects for the constrained optimization based approach to the design of robust stabilizers.