Improved Fault Ride Through Capability in DFIG Based Wind Turbines Using Dynamic Voltage Restorer With Combined Feed-Forward and Feed-Back Control

IEEE ACCESS, volume 5, date of current version October 25, 2017.

ABSTRACT: This paper investigates the fault ride through (FRT) capability improvement of a doubly fed induction generator (DFIG)-based wind turbine using a dynamic voltage restorer (DVR). Series compensation of terminal voltage during fault conditions using DVR is carried out by injecting voltage at the point of common coupling to the grid voltage to maintain constant DFIG stator voltage. However, the control of the DVR is crucial in order to improve the FRT capability in the DFIG-based wind turbines. The combined feed-forward and feedback (CFFFB)-based voltage control of the DVR verifies good transient and steadystate responses. The improvement in performance of the DVR using CFFFB control compared with the conventional feed-forward control is observed in terms of voltage sag mitigation capability, active and reactive power support without tripping, dc-link voltage balancing, and fault current control. The advantage of utilizing this combined control is verified through MATLAB/Simulink-based simulation results using a 1.5-MW grid connected DFIG-based wind turbine. The results showgood transient and steady-state response and good reactive power support during both balanced and unbalanced fault conditions.

 KEYWORDS:

1.      Doubly-fed induction generator (DFIG)

2.      Dynamic voltage restorer (DVR)

3.      Fault Ride-Through (FRT)

4.      Low Voltage Ride Through (LVRT)

5.      Combined feed forward feedback control

6.      MPPT

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Schematic Diagram of DVR with DFIG.

   

EXPECTED SIMULATION RESULTS:

Fig 2. DVR using CFFFB control: (a) supply voltage with 35 % balanced sag in pu, (b) load voltage in pu, and (c) DVR injection voltage in Volts.

Fig. 3. (a) Active Power of DFIG with CFFFB control DVR with 35 % balanced sag in pu. (b) Reactive Power of DFIG with CFFFB control DVR with 35 % balanced sag in pu. (c) Rotor speed control of DFIG with CFFFB controlled DVR with 35 % balanced sag in pu. (d) DC-link voltage with CFFFB controlled DVR with 35 % balanced sag in pu. (e) Stator current (GSC current) of DFIG with CFFFB controlled DVR with 35 % balanced sag in pu. (f) Rotor current (RSC current) of DFIG with CFFFB controlled DVR with 35 % balanced sag in pu.

Fig. 4 DVR using CFFFB control: (a) supply voltage with 35 % unbalanced sag of Phase A (in red) in pu, (b) load voltage in pu, and (c) DVR injection voltage in Volts.

Fig. 5. (a) Active Power of DFIG with CFFFB control DVR with 35 % unbalanced sag in pu. (b) Reactive Power of DFIG with CFFFB control DVR with 35 % unbalanced sag in pu. (c) Rotor speed control of DFIG with CFFFB controlled DVR with 35 % unbalanced sag in pu. (d) DC-link voltage with CFFFB controlled DVR with 35 % unbalanced sag in pu. (e) Stator current (GSC current) of DFIG with CFFFB controlled DVR with 35 % unbalanced sag in pu. (f) Rotor current (RSC current) of DFIG with CFFFB controlled DVR with 35 % unbalanced sag in pu.

Fig. 6. DVR using CFFFB control: (a) supply voltage with short circuit three phase to ground fault in pu, (b) load voltage in pu, and (c) DVR injection voltage in Volts.

Fig. 7 (a) Active Power of DFIG with CFFFB control DVR with short circuit three phase to ground fault in pu. (b) Reactive Power of DFIG with CFFFB control DVR with short circuit three phase to ground fault in pu (c) Rotor speed control of DFIG with CFFFB controlled DVR with short circuit three phase to ground fault in pu. (d) DC-link voltage with CFFFB controlled DVR with short circuit three phase to ground fault in pu. (e) Stator current (GSC current) of DFIG with CFFFB controlled DVR with short circuit three phase to ground fault in pu. (f) Rotor current (RSC current) of DFIG with CFFFB controlled DVR with short circuit three phase to ground fault in pu.

Fig. 8 Harmonic spectrum of DVR Load voltage with Feed Forward control shows THDD5.24 %.

Fig. 9 Harmonic spectrum of DVR Load voltage with CFFFB control shows THDD4.47 %.

 CONCLUSION:

This paper investigates the performance of DVR with combined Feed-Forward and Feed-Back control for the FRT capability improvement in DFIG based wind turbines. Series compensation scheme using DVR proves to be very effective with good reactive power compensation scheme, voltage control and power flow control. The performance comparison suggests that the operation of DVR is a good suit for improving FRT capability in DFIG based variable speed wind turbines as per grid code standards. The investigated combined Feed Forward and Feed Back (CFFFB) control has many advantages like simplicity with limited controller complexity. The controller is used to investigate the improvement in performance of FRT capability operation in DFIG wind turbine while modifying the voltage control of a DVR. The DVR proves to deliver very good transient voltage control, fault current control and reactive power support. The controller contributes in better harmonic compensation compared to conventional control as per IEEE 519 standards. The simulation results performed using a 1.5 MW DFIG based wind turbine connected to electrical grid show better performance of DVR with the combined Feed-Forward and Feed-Back control for improving the FRT capability of DFIG based wind turbines.

REFERENCES:

[1]         R. A. J. Amalorpavaraj, K. Palanisamy, S. Umashankar, and A. D. Thirumoorthy, ``Power quality improvement of grid connected wind farms through voltage restoration using dynamic voltage restorer,'' Int. J. Renew. Energy Res., vol. 6, no. 1, pp. 53_60, Mar. 2016.

[2]         R. A. J. Amalorpavaraj, P. Kaliannan, and U. Subramaniam, ``Improved fault ride through capability of DFIG based wind turbines using synchronous reference frame control based dynamic voltage restorer,'' ISA Trans., vol. 70, no. 1, pp. 465_474, Jul. 2017.

[3]         J. Morren and S. W. H. D. Haan, ``Ridethrough of wind turbines with doubly-fed induction generator during a voltage dip,'' IEEE Trans. Energy Convers., vol. 20, no. 2, pp. 435_441, Jun. 2005.

[4]         L. Holdsworth, X. G. Wu, J. B. Ekanayake, and N. Jenkins, ``Comparison of _xed speed and doubly-fed induction wind turbines during power system disturbances,'' IEE Proc.-Gen. Transmiss. Distrib., vol. 150, no. 3, pp. 343_352, May 2003.

[5]         A. D. Hansen and G. Michalke, ``Fault ride-through capability of DFIG wind turbines,'' Renew. Energy, vol. 32, no. 9, pp. 1594_1610, Jul. 2007.