Power system small-signal stability improvement by feedback of state and algebraic variables

In this paper the design of power system stabilizers for small-signal stability using phasor measurements is considered. The power system is described by a set of differential- algebraic equations. The power system stabilizers are designed to use measurable state variables and algebraic variables measured by the synchronized phasor measurement system (SPMS). Phasor measurement units (PMU) are placed at the terminal of each generator. Is is shown that in the case of salient-pole machines without damping windings, the changes in the remaining states can be determined from these measurements. Full state feedback and decentralized state feedback can then be used to design a controller, in the linearized system, for improving the angular small-signal stability. The input of this controller is a combination of measurable state variables and algebraic variables. Application to an equivalent of the South-Southeastern Brazilian system illustrates the approach.