A Novel Dynamic Energy Model and Damping Evaluation Method of DFIG Grid-connected System

Aiming at the uncertain mechanism of sub-synchronous oscillation caused by the connection of Doubly Fed Induction Generator (DFIG) and series compensation equipment, this paper proposes a method for analyzing the damping characteristics of sub-synchronous oscillations based on dynamic energy model. Firstly, using the dynamic energy of the DFIG and series compensation, combined with the induction generator equation of the DFIG, the converter control equation and the series compensation equation, the dynamic energy function under the electromagnetic transient scale is constructed. On this basis, considering the actual measurement conditions, calculating the dynamic energy under sub-synchronous frequency disturbance, obtaining the oscillation energy reflecting the interaction of the DFIG turbine and series compensation, and then construct the oscillation energy stability criterion for grid-connected system of the DFIG. Quantitative analysis of the energy interaction between the DFIG and series compensation by the oscillation energy reveals the influence mechanism of series compensation on the sub-synchronous oscillation. Finally, combined with the DFIG actual parameters, the above method is verified on the RTLAB simulation platform. The results show that the dynamic energy can accurately reflect the influence of DFIG-Series compensation, which showing negative damping characteristics in the sub-synchronous oscillation.