Appropriate models for designing frequency control schemes in power systems

Abstract

Frequency response characteristics like frequency nadir and rate of change of frequency (ROCOF) are important in designing frequency control schemes. The so-called Frequency Response Model (FRM), widely used in power system frequency studies, has some limitations in calculating these metrics. This paper evaluates and analyses the performance of FRM and multi-area FRM in calculating performance metrics for small and multi-machine power systems while considering the effect of amplitude and duration of voltage deviations after a disturbance. The capabilities and limitations of FRM and multi-area FRM are inferred by comparing their performance with a detailed model. To overcome the shortcomings of simplified models, a partly-linearized detailed model is suggested that preserves the important nonlinearities in frequency studies but, to consider the impact of the network on the results of frequency studies with reduced computation time, linearizes the models of other system components. Also, based on the two-part characteristic curve of steam and gas power plants, modified models have been suggested for the turbines and included in the proposed model. Numerical results show that the accuracy of the proposed simplifications is close to the detailed model while its computation time is less than 10 % of that of the detailed model.