Double Impedance-Substitution Control of DFIG Based Wind Energy Conversion System

Abstract

In a doubly-fed induction generator (DFIG)-based wind energy conversion system (WECS), when the grid voltage sags severely, the rotor side converter (RSC) suffers from overvoltage and overcurrent owing to the large electromotive force (EMF). To ensure that the converter operates within a safe range when grid faults occur, this paper proposes a double impedance-substitution control (DISC) strategy to improve the system’s low-voltage ride through (LVRT) capability. When the grid voltage sag is detected, the grid side converter (GSC) and RSC are connected in parallel to the rotor circuit by changing the topology of the system. In the new topology, GSC and RSC are equivalent to inductive impedance by controlling, which can not only suppress the overvoltage and overcurrent at the rotor side, but also effectively reduce the torque ripple. Additionally, the DISC strategy can provide reactive power support to the grid during LVRT. Finally, the simulation results show that the DISC strategy can maintain the current flowing through the RSC within ±1 p.u., and compared with the existing control strategy, the effectiveness of the proposed method was further demonstrated.

Improved Transient Performance of DFIG-Based Wind-Power System Using Combined Control of Active Crowbars

“…This induced dc component has the maximum value for φΨ0 = π and no dc component appears if φΨ0 = 0. Transforming (17) into the stationary rotor-reference frame, then From (18), the expression of the rotor EMF can be substituted as: The term (1/ τs) can be ignored due to the large time constant of the stator flux. Considering the most serious scenario, i.e., phase-to-phase fault and the worst condition of a full voltage dip (d = 1, φΨ0 = π), Ψsdc is given by…”

“…These solutions can largely be divided into two subgroups: (1) improved control structures for DFIGs and (2) enhanced external hardware-based solutions. Numerous modified control schemes have been presented in [7,[9][10][11][12][13][14][15][16][17][18][19][20] such as feedforward current-references control [7], flux-linkage control [9], demagnetization control [10], modified controls for RSC [11], flux magnitude and angle control [12], sliding-mode control [13,14], negative-sequence current regulation [15], an enhanced reactive power support [16], and an improved control design for wind-power converters [17]. A double impedancesubstitution control approach to expand the LVRT capability of a DFIG was suggested in [18].…”

“…Numerous modified control schemes have been presented in [7,[9][10][11][12][13][14][15][16][17][18][19][20] such as feedforward current-references control [7], flux-linkage control [9], demagnetization control [10], modified controls for RSC [11], flux magnitude and angle control [12], sliding-mode control [13,14], negative-sequence current regulation [15], an enhanced reactive power support [16], and an improved control design for wind-power converters [17]. A double impedancesubstitution control approach to expand the LVRT capability of a DFIG was suggested in [18]. A study of the transient stability of DFIG-based WT system was presented in [19], in which phaselocked loop and current control loops were considered.…”

Improved Transient Performance of a DFIG-Based Wind-Power System Using the Combined Control of Active Crowbars

“…Numerous modified control schemes have been presented in [7,[9][10][11][12][13][14][15][16][17][18][19][20], such as feedforward current-references control [7], flux linkage control [9], demagnetization control [10], modified controls for RSC [11], flux magnitude and angle control [12], slidingmode control [13,14], negative-sequence current regulation [15], an enhanced reactive power support [16], and an improved control design for wind-power converters [17]. A double impedance-substitution control approach to expanding the LVRT capability of a DFIG was suggested in [18]. A study of the transient stability of DFIG-based WT systems was presented in [19], in which a phase-locked loop and current control loops were considered.…”