Small Signal Modeling and Stability Analysis of DFIG-VSG Wind Power Generation System

The doubly-fed induction generator (DFIG) wind power system based on virtual synchronous generator (VSG) has been widely concerned because of its advantages of providing virtual inertia support and self-synchronizing voltage source characteristics. In order to analyze the small-signal stability performance, this paper establishes a VSG based overall system model. For the algebraic equation calculation and cancelation of the PCC among the grid, DFIG stator and grid-side converter, there are some problems such as complex calculation process, mathematical model mismatch, and unclear physical meaning, so the doubly-fed machine model based on the Thevenin-Norton equivalent theorem is proposed. Finally, the overall system simulation is presented and the results indicate that the system exists three oscillation modes. The `borrow damping phenomena' between PLL and VSG related oscillation mode under the weak grid is found and cause system instability. This modeling method provides a theoretical basis and practical tools for small-signal stability analysis of the VSG-DFIG wind power generation system.