ABSTRACT:
This
paper proposes an improved fault-ride through (FRT) system for a wind turbine
with doubly fed induction generator (DFIG) that is based on the proper stator
voltage control to address symmetrical as well as unsymmetrical and unbalanced
grid voltage sags. This is accomplished by adopting a properly modified
topology of the conventional wind energy con-version system (WECS) with DFIG
that provides the ability to regulate the stator voltage through the system of
the rotor power converters. Therefore, significant improvement of the FRT capability
is attained, since any oscillations of both the stator and ro-tor currents that
may be caused by the voltage dip can be considerably reduced and they can
remain within predefined safety limits. The implementation of the new topology
as well as the corresponding control system are cost effective, since no additional
hardware is required, and it is accomplished by the reconfiguration of the
conventional topology. Selective simulation and experimental results obtained
by a high and low scale WECS with DFIG, respectively, are presented to validate
the effective-ness of the proposed FRT control method and demonstrate the
operational improvements.
KEYWORDS:
1. Fault-ride through
2. Doubly-fed
induction generator
3. Wind power
generation
4. Wind turbine
5. Reliability
6. Voltage control
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Comparison of the structure of a variable speed WECS with DFIG: (a)
conventional and (b) improved FRT capability system.
EXPERIMENTAL RESULTS:
Fig.
2. Simulation results of the performance of the proposed FRT wind sys-tem with
DFIG of 1.6-MW, when a symmetrical grid voltage disturbance from 100% to 20%
and then 100% of the nominal value occurs, for a low wind speed of 4.5 m/s.
Fig.
3. Simulation results of the performance of the proposed FRT wind system with
DFIG of 1.6-MW, when a symmetrical grid voltage disturbance from 100% to 20%
and then 100% of the nominal value occurs, for a high wind speed of 9 m/s.
Fig.
4. Zoom of the simulation results of Fig. 5 (WECS with DFIG of 1.6- MW), at the
time that the grid voltage disturbance from 100% to 20% of the nominal value
occurs (wind speed 9 m/s).
CONCLUSION:
A highly effective FRT control system
for a WECS with DFIG has been proposed in this paper. A new WECS topology has
been adopted that gives the ability to control the stator of the DFIG.
Specifically, by properly controlling the rotor side converter of the DFIG, the
stator voltage can be kept constant at the nominal value and thus, a fault
diagnosis system is not required. Therefore, the WECS can continue the
operation without being affected by any symmetrical, unsymmetrical and
unbalanced grid voltage disturbances, and thus, no transient current and
voltages are caused. The implementation of the proposed FRT control system does
increase the cost of WECS compared to the conventional system, since it is
based on the proper modification by replacing expensive components of the
conventional system with low cost components and vice-versa. The effectiveness
and the high performance of the pro-posed FRT control scheme have been
validated with several simulation results obtained by a high power WECS-DFIG of
1.6-MW and experimentally in a laboratory low power scaling emulated WECS with
DFIG of 5.5-kW.
REFERENCES:
[1] E. Hau, Wind
Turbines: Fundamentals, Technologies, Application, Economics,
Springer-Verlag: 2013, 3rd Edition.
[2] A. El-Naggar and I.
Erlich, ‘Fault current contribution analysis of dou-bly fed induction
generator-based wind turbines’, IEEE Trans. Energy Conv., vol. 30, no.
3, pp. 874-882, Sept. 2015.
[3] D. Xiang, L. Ran, P.J.
Tavner, and S. Yang, ‘Control of a doubly fed induction generator in a wind
turbine during grid fault ride-through’, IEEE Trans. Energy Conv., vol.
21, no. 3, pp. 652-662, Sep. 2006.
[4] S. Seman, J. Niiranen,
and A. Arkkio, ‘Ride-through analysis of doubly fed induction wind-power
generator under unsymmetrical network dis-turbance’, IEEE Trans. Power Syst.,
vol. 21, no. 4, pp. 1782–1789, Nov. 2006.
[5] J. Morren and S.W.H. de
Haan, ‘Ridethrough of wind turbines with doubly-fed induction generator during
a voltage dip’, IEEE Trans. En-
ergy Conv.,
vol. 20, no. 2, pp. 435-441, June 2005.
