A Method for Evaluating the Impact of Controllers and Wind Turbine Generators on Low-Frequency Oscillation

Based on the celebrated Generalized Nyquist Criterion, this paper presents a new frequency-domain method to analyze the impact of governor-turbine systems (GTSs), power system stabilizers (PSSs) and wind turbine generators (WTGs) on small disturbance stability in power systems. Compared with other common analysis method, the new method can avoid the calculations of eigenvalues, eigenvectors and residues, and the impact of multiple controllers or WTGs can be obtained using simple matrix operations. In addition, the method is intuitive for users since the stability analysis results can be displayed in the complex plane directly. The new method indicates that the impact of controllers and WTGs on power system is determined by the phase of certain elements in the transfer function matrices of controllers, WTGs and synchronous grid. Based on the information provided by the afore-mentioned transfer function matrices, the parameters of controllers can be optimized properly. The proposed method has been tested using the data of a four-machine two-area system and a regional power grid in China. The results demonstrate that the effect of controllers and WTGs can be conveniently identified, and the effectiveness of parameter tuning for controllers is verified.