Inner Control Method and
Frequency Regulation of a DFIG Connected to a DC Link
ABSTRACT:
In this paper, an inner loop for the control and
frequency regulation of the doubly fed induction generator connected to a dc
link through a diode bridge on the stator is presented. In this system, the
stator is directly connected to the dc link using a diode bridge, and the rotor
is fed by only a pulse width-modulated (PWM) converter. If compared to the DFIG
connected to an ac grid, this system uses one PWM inverter less and a much less
expensive diode bridge. Thus, the cost of power electronics is reduced. The application
in mind is for dc networks such as dispersed generation grids and microgrids. These
networks use several elements that should work together. Usually, these
elements are connected with each other by power electronic devices in a common
dc link. This paper presents a control system for the inner control loop in order
to regulate the torque and the stator frequency. Simulation and experimental
results show that the system works properly and is able to keep the stator
frequency near the rated value of the machine.
KEYWORDS:
1.
Control
2.
Dc link
3.
Dc microgrids
4.
Doubly fed induction generator
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.1.Structure
of the DFIG-DC. Diode bridge on the stator, PWM converter on the rotor.
CONCLUSION:
This
paper presents a control method for the DFIG connected to a dc link through a
diode rectifier on the stator windings. Simulation and experimental results
show that it is possible to drive the stator flux at the rated frequency of the
machine by using a simple controller that adjusts the rotor d-axis
current reference in order to annihilate the orientation error. The method
converges to the field orientation and the steady-state frequency error is
zero.Agood dynamics is achieved in the electromagnetic torque. The waveforms of
the stator current are not sinusoidal, due to the presence of the diode bridge,
but have an acceptable harmonic content. The industrial application of this system
could be implemented using a 12-pulse rectifier, which reduces not only the
torque ripple but also the harmonic content in the rotor currents.
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[5]
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