Full-order modeling and design-oriented stability analysis of dual-loop grid-forming Type-3 wind generators

As the penetration of renewable energy increases, Type 3, wind turbines using doubly fed induction generators are required to support grid stability, with grid-forming control (GFM) emerging as an attractive solution. This paper provides a comprehensive small-signal model and design-oriented stability analysis of a Type-3 wind generator system with dual-loop GFM control. The full-order model offers a flexible representation of the GFM Type-3 system accounting for grid frequency disturbances and full coupling between rotor-side and grid-side converters. It is flexibly adapted to the calculation of generator input admittance and of several closed-loop transfer functions, which are used to assess internal and external stability margins and the influence of grid parameters on the closed-loop system dynamics across a wide frequency range. Extensive time-domain EMT simulations in MATLAB/Simulink are performed to validate the study. The presented analysis provides practical guidelines for the design of a stable Type-3 generator GFM control with specified inertial and damping characteristics under different grid parameters. • A full-order model of dual-loop grid-forming Type-3 wind generators is established. • The model allows the analysis of stability margins and closed-loop dynamic behavior. • The power synchronization control (PSC) can excite low-frequency oscillations (LFO). • Increasing the PSC droop gain and damping improves LFO stability. • The reactive power control (RPC) can impact synchronous oscillation (SO) modes. • The virtual impedance parameters have minor effects on internal stability margins. • A lower virtual resistance improves P/Q decoupling but reduces the SO damping. • Weaker grids demand for a greater virtual impedance to preserve external stability. • Weaker grids decrease the virtual-inertia provision during frequency disturbances.