Crowbar-less ride through of asymmetrical gric faults with DFIG based WECS

Heightened state-feedback predictive control for DFIG-based wind turbines to enhance its LVRT performance

“…The stator flux, for its part, is a function of the stator voltage and the rotor current, whose dynamics are given by [34,35]…”

“…1), which isolate the zero-sequence component. Therefore, the voltage in the stator side of the transformer consists generally of the positive sequence → v sP and the negative sequence → v sN components [34], in other words, the inputs to the stator flux ODE in the stationary reference frame are given by [35] (3) in which V sP and V sN are the positive and negative sequence phasor magnitude and ω s is the stator voltage frequency. The stator flux solution from (2) may now be obtained as [34,35]…”

“…λ sn is the natural flux, which in the fault inception has initial value Ψ that depends on the stator voltage value previous to the fault as well as the new voltage value [34,35]. The natural flux initial value also depends on the fault inception angle [32].…”