Influence of the infinite-bus assumption in the design of damping controllers

The present paper analyzes the influence of the infinite-bus assumption in the design of damping controllers, evaluating its effects by a comparison with two other alternatives. The first alternative is the use of a multimachine model adopting one machine angle of the system as angular reference. The second alternative is the incorporation of the primary speed control in the multimachine model of the system. The damping controllers used in the analysis are designed through a systematic methodology that uses robust control techniques. It is possible to observe, in the obtained results, that the infinite-bus assumption modifies the system dynamics, degrading the performance of the system equipped with the controllers designed over models with such assumption. The use of multimachine models without the infinite-bus assumption in the controller design provided an improvement in the performance of the closed loop system, in all the performed tests.