Transient stability enhancement of grid-forming type-3 wind turbine generators

Grid-forming control is considered to be essential in the transition to renewables-dominated power systems. However, grid-forming Type-3 wind turbine generators present unique challenges due to their electromechanical coupling with the grid and the limited kinetic energy in their drive-trains. This prevents active power control methods that emulate synchronous-machine behaviour from delivering robust and stable performance in Type-3 turbines. These limitations become more evident during recovery from severe grid disturbances. To overcome these limitations, this paper proposes a lead-compensator (LC)-based approach for synchronisation and active-power control as an alternative to virtual-synchronous-generators (VSG). The proposed approach is intended to demonstrate that the system damping and the overall transient stability can be improved solely by altering the control structure. Therefore, several time-domain studies have been conducted under different grid-strength levels and current- limitation mechanisms, and the comparison of post-fault recovery performance of the two controllers are presented. The results show that excessive active power oscillations and rotor speed deviations observed with VSG control are substantially mitigated using the proposed LC approach. More importantly, this is achieved without compromising inertia and droop settings, or utilising frequency measurements. Reduced turbine mechanical stress and enhanced robustness are among the benefits of this approach.