Abstract:

To quantify the effects of interactions interaction between control loops of grid-connected fan systems, this paper proposes an analytical method that combines the modal analysis method and the relative gain array. Firstly, a small signal model of the DFIG-based wind farms integrated into grid through MMC-HVDC system is established, and the modal analysis method is used to screen out the sub/super-synchronous oscillations which may be affected by the interaction. Secondly, the relative gain array is introduced to confirm the existence of the interaction, quantify and compare the degree of the interaction between the control loops, it shows that the interaction exists between the rotor side converter control loops in DFIG and the constant V/f control loops in MMC-HVDC. Finally, the influence of the electrical distance and controller parameters on the interaction degree is quantitatively evaluated according to the variation of the relative gain array with the influencing factors, and the correctness of the conclusions is verified by the time domain simulation method.

Key words: DFIG, MMC-HVDC, sub/super-synchronous oscillations, relative gain array, interaction