Analytical evaluation of control strategies for participation of doubly fed induction generator-based wind farms in power system short-term frequency regulation

Increase in doubly fed induction generator (DFIG)-based wind farms degrades the short-term frequency regulation of power systems. However, such wind farms may have large amount of kinetic energy which can be rapidly injected into the power system to support system frequency by using an appropriate supplementary control loop. This study first analyses the impacts of DFIGs and their supplementary loop on power system short-term frequency regulation. Then, the average power system frequency model is modified to include the participation of wind farms in frequency control. Moreover, a new method is proposed to derive an analytical expression for minimum frequency of a power system, as an important index of frequency regulation, after a power imbalance occurrence. This analytical expression provides a tool for better insight into frequency behaviour of power systems with high levels of wind generation. The results of the analysis are verified by simulation of the nine-bus test system, using MATLAB/SIMULINK.