Direct Torque Control of DFIG Driven by Wind Turbine System Connected to the Grid

ABSTRACT:

This paper described a Direct Torque Control (DTC) applied to a Doubly Fed Induction Generator (DFIG) driven by a Wind Turbine (WT) connected to the grid. This control strategy based on the regulation of the flux and the torque, the currents and voltages are used to estimate the torque and the flux and compare those magnitudes to the reference values, the obtained results will be converted to digital form by hysteresis comparators. The commutation table will use those values and the sector number to choose the voltage vector. The aim of this study is to treat three modes that can drive WT-DFIG system utilizing Maximum Power Point Tracking (MPPT) technique. Computer simulation has carried out under MATALB/Simulink environment and the obtained results demonstrate the effectiveness of the proposed control.

 KEYWORDS:

1.      Direct Torque Control

2.      Doubly Fed Induction Generator

3.      Wind Turbine

4.      Wind Energy

5.      Maximum Power Point Tracking

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. DTC Control applied to DFIG connected to the grid.

EXPECTED SIMULATION RESULTS:

Fig.2. Wind speed.

Fig.3. Cp (λ) Characteristic.

Fig.4. Mechanical speed (generator speed).

Fig.5. Waveform of Slip.

Fig.6. Electromagnetic Torque.

Fig.7. Rotor and Reference flux.

Fig.8. The rotor flux.

Fig.9. Wave form of Rotor flux φ_rα and φ_rβ.

Fig.10. Rotor Current Ir(abc)

Fig.11. Rotor Reactive Power

Fig.12. Stator Current Is(abc)

Fig.13. Stator Power

 

Fig.14. Rotor Power

Fig.15. The FFT analysis of phase (a) stator current (Synchronous mode).

CONCLUSION:

A study of Direct Torque Control strategy applied to Doubly Fed Induction Generator used for Wind Turbine Conversation system has been presented in this paper. As known, the wind has a random movement imposing indiscriminate speed for the turbine, therefore driving DFIG in different modes (sub-synchronous, synchronous and super synchronous modes), those modes have been treated in this work. The obtained results show clearly satisfactory performances, they showed a good dynamic of the torque and the flux, low THD in synchronous mode and constant stator frequency, while keeping a better precision of control, as well as the efficiency of the control strategy leading to better performances.

REFERENCES:

 

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