Providing Ride-Through Capability to a Doubly Fed Induction Generator Under Unbalanced Voltage Dips

Grid-integrated permanent magnet synchronous generator based wind energy conversion systems: A technology review

“…One of the generic equations used to model C p , which is a function of tip-speed ratio λ and pitch angle θ, can be expressed as follows C p ðλ; θÞ ¼ 0: 73 151 λ i À 0:58θ À 0:002θ 2:14 À 13:2 exp À 18:4 λ i ð2Þ…”

“…In the 1990s, the diode bridges with the chopper circuits were used for rotor resistance control of wound-rotor induction generators (WRIGs) [69]. Since 2000, advanced ac-dc-ac converters were introduced; initially in the partial-scale power capacity to regulate the generated power from the DFIG based WECSs [70][71][72][73][74], and afterwards in the full-scale power capacity to regulate the generated power from the SCIG or PMSG based WECSs [48,[75][76][77][78][79][80].…”

A Scheme for the Power Control in a DFIG Connected to a DC Bus via a Diode Rectifier

“…It turns out to be more advantageous to express both a and L as as a function of m and use this as independent variable. To this purpose, (5b) and (14) equated to k/√2 p.u. (rotor current constraint, k= (I rn /n 12 )/I sn ) and with ψ x ′=1 p.u., allow to find L as and a as a function of m: By using (15a), the p.u.…”

“…One of the main issues in the control of grid connected DFIGs is to tackle the effects of dips in the stator voltage, which produce oscillations of the stator flux linkage and rotor overvoltages [11]- [12]. An adequate low-voltage ride-through capability [13]- [15] during faults in the ac grid must be guaranteed: in [13] an additional grid series converter is used to mitigate the effect of grid voltage changes on the stator voltage, whereas in [14] has a detrimental impact on the DFIG, due to unequal heating of the stator and rotor windings, and to the oscillations in the dc-bus voltage of the back-to-back converter. In [16], the additional grid series converter proposed in [13] is controlled to compensate for the grid voltage unbalance, whereas Yao et al [17] describe a control of the capacitor current, aimed to eliminate the fluctuations in the dc-bus voltage.…”

A novel control scheme for DFIG-based wind energy systems under unbalanced grid conditions

“…Negative sequence compensation can be realized through current control loops [3,[5][6][7][8][9][10], or through direct power control [11,12]. The cascaded control structure with inner fast current control and outer slower power/voltage control is widely used in converter control and is also used in the commercial DFIG technology [13].…”