This paper deals with the operation of doubly fed induction generator (DFIG) with an integrated active filter capabilities using grid-side converter (GSC). The main contribution of this work lies in the control of GSC for supplying harmonics in addition to its slip power transfer. The rotor-side converter (RSC) is used for attaining maximum power extraction and to supply required reactive power to DFIG. This wind energy conversion system (WECS) works as a static compensator (STATCOM) for supplying harmonics even when the wind turbine is in shutdown condition. Control algorithms of both GSC and RSC are presented in detail. The proposed DFIG-based WECS is simulated using MATLAB/Simulink. A prototype of the proposed DFIGbased WECS is developed using a digital signal processor (DSP). Simulated results are validated with test results of the developed DFIG for different practical conditions, such as variable wind speed and unbalanced/single phase loads.
- Doubly fed induction generator (DFIG)
- Integrated active filter
- Nonlinear load
- Power quality
- Wind energy conversion system (WECS).
Fig. 1. Proposed system configuration.
Fig. 2. Control algorithm of the proposed WECS.
EXPECTED SIMULATION RESULTS
Fig. 3. Simulated performance of the proposed DFIG-based WECS at fixed wind speed of 10.6 m/s (rotor speed of 1750 rpm).
Fig. 4. Simulated waveform and harmonic spectra of (a) grid current (iga), (b) load current (ila), (c) stator current (isa), and (d) grid voltage for phase “a” (vga) at fixed wind speed of 10.6 m/s (rotor speed of 1750 rpm).
Fig. 5. Simulated performance of the proposed DFIG-basedWECS working as a STATCOM at zero wind speed.
Fig. 6. Simulated waveforms and harmonic spectra of (a) load current (ila) and (b) grid current (iga) working as a STATCOM at wind turbine shut down condition.
Fig. 7. Simulated performance of proposed DFIG for fall in wind speed.
Fig. 8. Dynamic performance of DFIG-based WECS for the sudden removal and application of local loads.
The GSC control algorithm of the proposed DFIG has been modified for supplying the harmonics and reactive power of the local loads. In this proposed DFIG, the reactive power for the induction machine has been supplied from the RSC and the load reactive power has been supplied from the GSC. The decoupled control of both active and reactive powers has been achieved by RSC control. The proposed DFIG has also been verified at wind turbine stalling condition for compensating harmonics and reactive power of local loads. This proposed DFIG-based WECS with an integrated active filter has been simulated using MATLAB/Simulink environment, and the simulated results are verified with test results of the developed prototype of this WECS. Steady-state performance of the proposed DFIG has been demonstrated for a wind speed. Dynamic performance of this proposed GSC control algorithm has also been verified for the variation in the wind speeds and for local nonlinear load.
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