The document summarizes a presentation given at the IVth International Conference on Advances in Energy Research about using a doubly fed induction generator (DFIG) with a back-to-back converter for islanding operation to provide rural electrification. It introduces DFIG technology and control schemes for DFIG, and presents simulation results showing the performance of a DFIG system with battery energy storage supplying balanced and unbalanced resistive and reactive loads. The conclusion discusses how such systems can provide power for remotely located villages using locally available wind energy.

1. IV th International Conference on Advances in Energy Research
Indian Institute of Technology Bombay, Mumbai
Islanding Operation of DFIG for Rural Electrification Using
Back to Back Converter
Presented By
Paper ID-236
M.Tech Scholar Rakhi Soni
Co-authors- Monika Jain & Sachin Tiwari
OIST Bhopal (MP)

2. Contents
Introduction
 Distributed generation
 Technologies of DG
 Advantages of DG
 Types of generator
 DFIG (Doubly Fed Induction Generator)
 Control schemes of DFIG
 Results & discussion
 conclusion
 References


3. INTRODUCTION
Wind
turbines convert the kinetic energy present in the wind
into mechanical energy by means of producing torque.
They
are operated either at fixed speed or variable speed.
Generators
driven by fixed speed turbines can directly be
connected to grid.
Variable
speed generators need a power electronic converter
interface for interconnection with the grid.
Variable
generation.
speed generation is preferred over fixed speed

4. Types Of AC. Generators
AC GENERATOR
ASYNCHRONOS
GENERATOR
SEIG
DFIG
SYNCHRONOS
GENERATOR

5. DFIG (Doubly Fed Induction Generator)
Wound
rotor induction generator with slip rings.
Rotor
is fed from a three-phase variable frequency source,
thus allowing variable speed operation reduction of
mechanical stress; higher overall efficiency, reduced
acoustical noise.
The
variable frequency supply to rotor is attained through the
use of two voltage-source converters linked via BESS.

6. Advantage of DFIG
The
variable speed machines have several advantages :-
They
reduce mechanical stresses.
Reduced convertor losses.
improve power quality & system efficiency.

7. Control schemes of DFIG
DFIG
iLi(a)
ist(a)
Pm
Pm
a
iLi(b)
ist(b)
b
Vp(ab)
Vp(ca)
ist(c)
Vp(bc)
iLi(c)
c
iro(a)
iro(c)
iro(b)
RC Filter
Rbat
Cdc
Cbat
ica
Rin
icb
Vdc
Voc
Rotor side
converter
Battery
icc
Inductive
Filter
ibat
Stator side
converter
icn
Zig- Zag
Transformer
balanced/
unbalance
d, resistive
and
reactive
load

8. Principle of Operation
 The
rotor currents and stator currents of the DFIG are
controlled by stator-flux oriented control to decouple the active
and reactive components of these currents and to achieve fast
dynamic response.

Torque Control- The electrical torque of the DFIG can be
controlled to operate the wind turbine at the point of maximum
aerodynamic efficiency by controlling the active power current
component of the rotor.

Max. Power Point Control- To operate at maximum
coefficient of performance for optimizing energy capture from
the wind, the turbine should run at optimal tip speed ratio.

9. Continue…..

Voltage control- the voltage control at the stator terminals
is achieved by controlling the reactive component of the stator
current.
Frequency
control- the stator frequency control is achieved
by generating stator flux angle by integrating the reference
stator frequency and using that angle for transformation of
reference d-q stator quantities to reference three phase
quantities.

10. Wind Turbine
The aerodynamic power generated by wind turbine can be
expressed as by,
P=0.5ρACpV3ω
Where the aerodynamic power is expressed as a function of the
specific density (ρ) of the air, the swept area of the blade ( A),
and the wind speed (V3ω)

11. Stator side converter
Stator
current
measurem
-ent
Vter
*
DFIG
ist(a)
Cdc
ist(b)
*
Iqro
*
i st(a)
*
Iqst
PI Controller
Idst
*
i st(b)
Ɵ st flux
-Lm/Lst
*
2Πf t
dq/
abc
*
i st(c)
Battery
ist(c)
Vter
Voc
Rbat
ibat
Rin
Cbat
Hysteresis
controller
Hysteresis
modulating
signals
Inductive
filter
Zig- zag
transformer
n
Connected to load
Connected to stator
c
b
a

12. Cntd…
The terminal sensed voltage (Vter) is
calculated by,
Vter={(Vab2+Vbc2+Vca2)/3}1/2
Vter* which is taken as 415V.
Vterr(n) = Vter* -Vter
Vterr is fed to PI voltage controller with
gains Kpv and Kiv.
12

13. Cntd…
The magnetizing current
requirement of the DFIG is
provided by the rotor side
converter. Any additional
reactive power for the
electrical loads and stator
leakage reactance is supplied
from the stator side converter.
13

14. Cntd…
The
stator
frequency
control is achieved by
өstatorflux=2πfnTsamp
14

15. Cntd…
15

16. Rotor side converter
Vter
Stator
voltage
measurem
-ent
DFIG
Iro(b) Iro(a)
Iro(c)
imsaturated
Idro*
ωter
*
ωter
*
i
PI Controller
Iqro*
Ɵ slip
dq/
abc
ro(a)
Hysteresis
modulating
signals
*
i ro(b)
*
i ro(c)
Hysteresis
controller
Voc
Iro(a)
Iro(b)
Iro(c)
Cdc
Rbat
ibat
Battery
Ɵ st flux
(p/2) Ɵ
ro
Rotor
current
measurent
Cbat
Inductive
filter
Zig- zag
transformer
n
Connected to load
Connected to stator
c
b
a

17. Cntd…
The reference for the d
component of the rotor current
(Idro*) is taken as the rated
magnetizing current (lmsaturated),
Imsaturated = √2 Vter* / √3 Xm
Where, Vter* is 415V,
Xm is the magnetizing reactance
of the DFIG.
17

18. Cntd…
18

19. Cntd…
For dq to abc transformation, the
angle between d-axis and rotor
axis (ϴSlip) is required. ϴSlip can
be generated as,
ϴslip = ϴstatorflux - ( p/2 )ϴro
19

20. Cntd…
20

21. Battery Specifications
The terminal voltage of the equivalent battery Vbat is given by,
Vbat= (2√2/√3) V
Where VLi is the line rms. voltage (V = 415V). A slightly higher
round-off value of 750 V is considered.
the equivalent capacitance can be given by,
Cbat = (kwh * 3600 * 103) / 0.5 (V2ocmax – V2ocmin)
Cbat = (7.5*10*3600*103) / 0.5 [(7602) – (7402)]
Cbat = 18000 F

22. Ratings……
A. Machine parameters:
7.5 kW, 415V, 50Hz, Y -connected, 4-pole, Rs = 1Ω,
Rr=0.77Ω, Xlr= Xls= 1.5Ω, J= 0.1384kg-m2
B. Wind turbine parameters:
Wind rating= 15 kW, Wind Speed Range = 9 -11 m/sec,
Inertia = 3 .5 kg_m2, r = 3.55 m, gear ratio= 7.516.
C. Controller parameters:
Kpf= 10, Kif = 50, Kpd = 0.02, Kid = 0.0025.

23. Ratings……
D. Battery parameters:
Lf = 3mH, Rf = 0.1Ω and Cdc = 4000µf, R1=10K, Ro=0.01 Ω,
Cbat=36000 F
E. Zigzag Transformer specification:
Three phase zigzag transformer, 50 Hz, 150 V/ 415 V, kVA rating
=10 kVA.
F. Consumer Loads:
Resistive load= 2.5 kW single phase loads.
Reactive load = 2.5kW, 1.875 KVAR 0.8PF lagging single Phase
loads.

24. Performance of DFIG with BESS Feeding Balance /
Unbalanced Resistive Load
Icabc1
Stator V abc
Stator voltage
Controller current 1
500
20
00
-20
-500
2.1
2.1
2.2
2.3
2.4
2.5
2.15
2.2
2.25
2.1
2.15
2.2
2.25
-20
2.1
2.15
2.2
2.25
2.15
2.2
2.25
2.6
2.35
2.4
2.9
2.45
2.3
Load netural current
2.35
2.4
2.45
2.5
2.3
2.35
2.4
2.45
2.5
2.3
2.35
2.4
2.45
2.5
2.3
Stator current
2.7
2.8
3
2.5
0
i
abc
20
-20
0
I
Ln
20
I
L abc
20
Load current
0
-20
2.1

25. Cntd…
Frequency (Hz)
55
f
50
45
2.1
2.15
2.2
2.25
2.4
2.45
2.5
2.7
2.4 2.8
2.9
2.45
3
2.5
2.7
2.8
2.9
3
te r
Wind
I bat 1
Vt3
Vt2
V
f 2
f 3
2.35
Terminal (Hz) 3
Frequency voltage
2
600
55
50550
45500
2.12.1
2.3
2.2 2.15
2.3 2.2
2.4 2.25
2.3
2.6
2.35
Battery Current
10
600
0
550
-10
500
12 2.1
2.5
Terminal voltage 2
3
2.2
2.3
2.4
2.5
Wind
2.6
10
8
2.1
2.15
2.2
2.25
2.3
Time
2.35
2.4
2.45
2.5

26. Performance of DFIG with BESS Feeding Balance/
Unbalanced Reactive Load
Icabc1
Stator V abc
Stator voltage
500
200
0
-20
-500
2.1
2.1
Controller current 1
2.22.15
2.3 2.2
2.4
2.1
2.15
2.2
2.25
-20
2.1
2.15
2.2
2.25
2.25
2.5
2.35 2.7
2.4 2.8
2.9
2.45
3
2.5
2.3
2.35
2.4
2.45
2.5
2.3
2.35
2.4
2.45
2.5
2.35
2.4
2.45
2.5
2.3
2.6
Stator current
0
i
abc
20
-20
Load netural current
0
I
Ln
20
Load current
I
L abc
20
0
-20
2.1
2.15
2.2
2.25
2.3

27. Cntd…
Frequency (Hz)
f
55
50
45
2.1
2.15
2.2
2.25
2.3
Terminal voltage
Frequency (Hz) 32
2.35
2.25
2.5 2.3 2.6
Battery Current
Terminal voltage 2
3
2.35
2.45
2.5
2.45
2.9
32.5
2.9
3
3
f V te r
f 2
600
2.4
55
50
500
452.1
2.1
IVt3 1
Vt2
bat
55
550
2.3
2.2
2.2
2.3
2.4
10
600
5500
500
-10
2.1
12
Wind
2.22.15
2.4
2.5
Wind
2.6
2.7
2.4
2.7
2.8
2.8
10
8
2.1
2.15
2.2
2.25
2.3
Time
2.35
2.4
2.45
2.5

28. Conclusion



There are many isolated locations which cannot be connected
to the grid and where the wind potential exists, for such
locations wind system are beneficial.
The performance of proposed controller demonstrated under
balanced/unbalanced linear loads. The simulated results verify
the effectiveness of the controller under various consumer
loads. It has been observed that the proposed controller has
been found to regulate the magnitude and frequency of
isolated system. It has also been found that controller is
capable to function as load balancer, load leveler and
harmonic eliminator as well as the capability of MPT.
Zigzag transformer is used for harmonics eliminator having
voltage boost capability. The implementation of this
technology reinforces the use of such system in remotely
located villages by locally available energy sources.

29. References
[1] Peña, R., Clare J. C., and Asher G. M. (May 1996) “Doubly Fed Induction
Generator using back to-back PWM converters and its application to variable
speed wind-energy generation,” Proc. Inst. Elect. Eng., Elect. Power Appl.,
vol.143, no. 3, pp. 231–24.
[2] Murthy S. S., (2007) “A Comparative Study of Fixed Speed and Variable
Speed Wind Energy Conversion Systems Feeding the Grid,”IEEE conference.
[3] Singh Bhim, (2010) “Performance of wind energy conversion system
using a doubly fed induction generator for maximum power point tracking”
IEEE conference.
[4] Blaabjerg, F., Chen, Z. and Kjer S.B. (2010) “Power electronics as
efficient interface of renewable source”, IPEMC conference.
[5] K. Goel Puneet, “Modeling and Control of Autonomous Wind Energy
Conversion System with Doubly Fed Induction Generator,”IEEE Conference.
[6] K. Goel Puneet, Singh Bhim, (April 2011) “Isolated Wind–Hydro Hybrid
System Using Cage Generators and Battery Storage,” IEEE Transactions On
Industrial Electronics, vol. 58, no. 4, pp. 1141-1152.

30. Continued……
[7] Mullane A. Lei Y, Lightbody G., and Yacamini R. (Mar. 2006) “Modeling
of the wind turbine with a doubly-fed induction generator for grid integration
studies,” IEEE Trans. Energy Conversion, vol. 21, no. 1, pp. 257-264.
[8] Kasal Gaurav Kumar, (June 2008) “Voltage and frequency controller for a
Three-phase Four wire Autonomous wind energy conversion system,” IEEE
Transactions on Energy Conversion, vol. 23, no. 2, pp. 509- 516.
[9] Singh Bhim, (2010) “Performance of Wind Energy Conversion System
using a Doubly Fed Induction Generator for Maximum Power Point
Tracking” IEEE conference.
[10] Verma Vishal, (2011) “Decoupled Indirect Current Control of DFIG for
Wind Energy Applications,” IEEE Conference.
[11] K. Goel Puneet, (July/August 2011 ) “ Parallel Operation of DFIGs in
Three-Phase Four-Wire Autonomous Wind Energy Conversion System,”
IEEE Transactions on Industry Applications, vol. 47, no. 4,1872-1883.
[12] Marek Adamowicz* and Ryszard Strzelecki, (2008) “Cascaded Doubly
Fed Induction Generator for Mini and Micro Power Plants Connected to
Grid,” IEEE conference.

31. Continued……
[13] Ganti Vijay chand, (2010) “Quantitative Analysis and Rating Considerations of a
Doubly Fed Induction Generator for Wind Energy Conversion Systems,” IEEE
conference.
[14] Kasal Gaurav Kumar, (2008) “Voltage and frequency control with Neutral current
compensation in an Isolated Wind Energy Conversion System,” IEEE conference.
[15] Muller S., Deicke M. and De Doncker R. W. (May/Jun. 2002) “Doubly fed
induction generator systems for wind turbines,” IEEE Ind. Appl. Mag., vol. 8, no. 3,
pp. 26–33.
[16] Petersson A. Harnefors, L. and Thiringer T. (Jan. 2005) “Evaluation of current
control methods for wind turbine using doubly-fed induction machine,” IEEE Trans.
Power Electron., vol. 20, no. 1, pp. 227–235.
[16] Slootweg, J. G., Haan, H. W. S., Polinder, H. and Kling, L. W. (Feb. 2003 )
“General model for representing variable speed wind turbines in power system
dynamics simulations,” IEEE Trans. Power Syst., vol. 18, no. 1, pp. 144– 151.
[17] Simoes M.G. and Farret F. A., (2004) “Renewable Energy Systems: Design and
Analysis With Induction Generators”. Orlando, FL: Fl-CRC.
[18] Blaabjerg F., Chen Z., Teodorescu R. & Lov F., (2006) “Power electronics in
wind turbine systems,” IEEE Int. Conf. on Power Electronics and Motion Control, pp.
1-11.

32. SAVE ENERGY SAVE FUTURE
THANKS
32