Design of conventional power system stabilizers
(PSSs) is load-dependent and thus has to be adjusted at every
operating condition. An interval arithmetic (IA) based approach
is proposed, to rigorously address load uncertainties associated
with the design of PSS. The proposed approach characterizes
the set of all robust stabilizing PSSs computed for a singlemachine
infinite-bus system. A robust PSS can properly
function over the full range of operating conditions. An interval
plant transfer function is determined over the operating range
where upper and lower bounds of the coefficients are precisely
computed. Using a proportional-derivative (PD) PSS, an interval
characteristic polynomial for the closed loop system is
generated. Interval Routh-Hurwitz array is developed to
determine the boundaries of robust stability region in Kp-Kd
plane via IA computation. Thereafter, the results obtained by
interval Routh array are relaxed using degenerate interval
array with an image-set polynomial of the plant where the
boundaries of the robust stability region is exactly computed.
Simulation results confirm the effectiveness of a sample
controller, which lies within the solution set, as it is applied to
the original nonlinear system model under wide loading
conditions.