A novel interpretation for grid-following virtual inertia of DFIG: Fast power response

In order to correct the misunderstanding of previous studies, this article presents a novel interpretation of inertia response of double fed induction generator (DFIG) from system perspective. The dominant factors affecting frequency dynamics are clarified combined with the regulation process. And the differences of inertia responses between synchronous generator (SG) and DFIG are analyzed and illustrated for the first time. To obtain better insight into physical properties of DFIG, a frequency response linearized model of DFIG with inertia emulation is derived according to vector control strategy, and based on the analytical model, the essential reason of frequency support by DFIG is revealed and rectified from not only frequency dynamics but also rotor angle stability perspective. The simulation of a generic two-machine system and two-machine infinite bus system are implemented in MATLAB/Simulink. The simulation results verifies that the linearized model of DFIG is effective for frequency study, and conclusion is acquired that the frequency enhancement of DFIG to system should be recognized as “fast power response” instead of providing virtual inertia.