Probabilistic Power System Stabilizer

One of the low-frequency oscillation damping methods is to use power system stabilizer (PSS). Setting of PSS parameters is typically performed via certain (deterministic) methods, in which a limited number of different operating points are taken into account. Therefore, PSS performance is limited to the same operating points. In this paper, the design of PSS is performed for a wide range of load changes. In this regard, several different load levels are considered and one possibility is assigned to each load level. Then to consider load variation around each load level, corresponding to each level, a normal probability distribution function is considered for load changes. Mean value of each normal distribution is assumed to be equal to the corresponding value of the load level. Distribution variance is also chosen equal to the percentage of the mean value. Two models of constant power and constant impedance models are used for the loads. To set the parameters of PSS, an optimization problem is defined with the objective function of minimizing of the presence probability of eigenvalues in the unsuitable areas. Comparing the results obtained by using certain and probabilistic PSS in the IEEE 39- bus test system shows that the proposed method is more robust to load variations.