Countermeasures for self-excited torsional oscillations using reduced order robust control approach

Torsional oscillations can be destructive to power systems. Understanding the factors leading to these oscillations and finding appropriate countermeasures has been a major concern. In this paper, a robust controller based on the linear quadratic Gaussian with loop transfer recovery (LQG/LTR) approach is designed to damp these undesired oscillations. The controller uses only one measurable feedback signal (generator speed deviation). A reduced-order version of this controller is also obtained. The robust control results are compared to the "idealistic" full state optimal control. Simulation results revealed that the technique damps all torsional oscillatory modes in a very short time, yet maintains reasonable control actions.