Damping of electromechanical oscillations based on the internal model principle

A supplementary control method based on the internal model principle (IMP) is proposed to control damped oscillations. As a case study, low frequency oscillations threaten the stability and the performance of power systems. The challenge, however, is how to acquire the frequency and the damping of oscillations on-line since the parameters of oscillations are unknown in a power system. To design an IMP-based controller, it is necessary to know the precise parameters of oscillations, especially frequency and damping. To solve this problem, an adaptive structure is proposed to estimate the parameters of damped sinusoidal signals. In the proposed method, the dynamic of power system oscillations is identified; afterward, this dynamic is placed in the control loop such that the oscillations are rejected from the output. The proposed method has some advantages such as simplicity, robustness, no need to know the parameters of the power system for design, and being on-line. To evaluate the performance of the proposed method, simulation studies are carried out on two practical power systems. The simulations show that the proposed method has a desirable performance.