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Control of a self-excited squirrel
cage induction machine based
wind energy conversion system

Vikram Roy Chowdhury
Outline
• Introduction & Background
• Operation and design of the SCIG based system.
• Controllers Design
Machine terminal...
Literature review/Background
• VAR control with STATCOM and SVC are well reported
in literature in grid connected mode.
• ...
Self excitation process for an induction
machine

Rs
F
R
F

Vt
F jX

jXls

jXlr
Ir

Is

jX c
F2

Rr
F

Vg
F

jXm

V
Equations in the self excited mode

=

+

=

(

+j

)+ (

+

)

Magnetization characteristics of the
machine.
Characteristics of the chosen machine in self
excited mode
Variation of terminal voltage with active power output

Variati...
Topology of SVC used with its control strategy in
standalone mode for voltage control

The configuration of the SVC
with i...
Control strategy of SVC in grid connected
mode

Control strategy of SVC under grid connected mode of
operation
Configuration of the STATCOM used
Equation of an inverter in the voltage oriented
reference frame

P=
Q=

P=

(Active Power)

Q=

(Reactive power)
Unit vector generation or defining axes for
transformations

where
d-AXIS CONTROLLER FOR THE
STATCOM
DC bus voltage and current controller
q-AXIS CONTROLLER FOR THE
STATCOM
Terminal voltage(standalone mode)/VAR(grid mode)
controller and current controller
Pitch angle control scheme for the system
For standalone mode
Contd…
For grid connected mode
Results for Voltage control and VAR control
with SVC
Reactive power control with SVC in grid connected mode

Terminal volt...
Results obtained with STATCOM
Results for d-axis quantities
Reference Vdc* and actual Vdc

Reference Id* and actual Id

95...
Contd…
Results obtained for q-axis quantities
Reference Iq* and actual Iq

Reference Vt* and actual Vt
80

320
Reference
A...
Grid Voltage and current with SVC and
STATCOM
Grid voltage and grid current with SVC connected

Grid voltage and current b...
VAR control in grid connected mode with
transient
KVAR(Reference and Actual)
2
Reference
Actual

---------------->Reactive...
DC bus voltage required with SVM technique
Reference Vdc* and actual Vdc with SVM
800
Reference
Actual

790

-------------...
Result of frequency control for standalone
mode of operation
Actual frequency and its reference
55
Reference frequency
Act...
CONCLUSION AND FUTURE WORK
• By this method both standalone and grid connected systems can be operated
satisfactorily.
• G...
REFERENCES
• [1] Wind electrical systems by D. Kastha, S.N. Bhadra and S. Banerjee
• [2] Understanding FACTS TECHNOLOGY OF...
QUESTIONS??
THANK YOU
Data of the machine used for simulation
Quantities

Values

Rated Voltage( L-L)

400 V

Rated Line Current

67.6 A

Number...
Magnetization Characteristics of the chosen
machine
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  1. 1. Control of a self-excited squirrel cage induction machine based wind energy conversion system Vikram Roy Chowdhury
  2. 2. Outline • Introduction & Background • Operation and design of the SCIG based system. • Controllers Design Machine terminal voltage in standalone mode VAR controller in grid connected mode DC bus voltage control. Overall current control. Overall pitch control scheme. • Comparison of the system operation with SVC and STATCOM • Verification of the above control scheme in MATLAB/SIMULINK platform.
  3. 3. Literature review/Background • VAR control with STATCOM and SVC are well reported in literature in grid connected mode. • Pitch control over rated speed is reported in literature. • Self excited induction machine characteristics are well reported in many literatures. • Back to back connected converter control of wind systems are well reported in literature. • A new type of pitch control method is being proposed. • Utilization of SVC and STATCOM for standalone application is successfully demonstrated. • Overall electrical control by only shunt compensators are demonstrated.
  4. 4. Self excitation process for an induction machine Rs F R F Vt F jX jXls jXlr Ir Is jX c F2 Rr F Vg F jXm V
  5. 5. Equations in the self excited mode = + = ( +j )+ ( + ) Magnetization characteristics of the machine.
  6. 6. Characteristics of the chosen machine in self excited mode Variation of terminal voltage with active power output Variation of per unit frequency with active power output 260 0.962 0.96 C=680 255 0.958 250 0.956 ----------------------->F ----------------->Vt C=650 C=620 245 0.954 C=620 0.952 0.95 C=650 0.948 240 0.946 C=680 0.944 235 0 1 2 3 ---------------->Po 4 5 6 Terminal Voltage versus active power output 0.942 0 1 2 3 -------------------->Po 4 5 Per Unit frequency versus active power output 6
  7. 7. Topology of SVC used with its control strategy in standalone mode for voltage control The configuration of the SVC with its equivalent reactance Control voltage generation for firing the SVC for standalone mode
  8. 8. Control strategy of SVC in grid connected mode Control strategy of SVC under grid connected mode of operation
  9. 9. Configuration of the STATCOM used
  10. 10. Equation of an inverter in the voltage oriented reference frame P= Q= P= (Active Power) Q= (Reactive power)
  11. 11. Unit vector generation or defining axes for transformations where
  12. 12. d-AXIS CONTROLLER FOR THE STATCOM DC bus voltage and current controller
  13. 13. q-AXIS CONTROLLER FOR THE STATCOM Terminal voltage(standalone mode)/VAR(grid mode) controller and current controller
  14. 14. Pitch angle control scheme for the system For standalone mode
  15. 15. Contd… For grid connected mode
  16. 16. Results for Voltage control and VAR control with SVC Reactive power control with SVC in grid connected mode Terminal voltage of the machine with SVC as compensator 10 Reference Actual ---------------->KVAR control in grid connected mode ---------------->Terminal voltage of the machine 300 250 200 150 100 50 19.8 19.82 19.84 19.86 19.88 19.9 19.92 19.94 19.96 19.98 ---------------->Time(secs) Control of terminal voltage by SVC 20 Reference Actual 5 0 -5 -10 -15 -20 33 33.02 33.04 33.06 33.08 33.1 33.12 33.14 33.16 33.18 ---------------->Time(secs) 33.2 Control of reactive power by SVC Operating Condition: Load 15 KW 220 V 50 Hz 0.7 power factor lag
  17. 17. Results obtained with STATCOM Results for d-axis quantities Reference Vdc* and actual Vdc Reference Id* and actual Id 950 50 Reference Actual 940 30 920 20 ---------------->Id(ampere) 930 ---------------->Vdc(volts) Reference Actual 40 910 900 890 880 10 0 -10 -20 870 -30 860 -40 850 46.9 46.92 46.94 46.96 46.98 47 47.02 47.04 47.06 47.08 ---------------->Time(secs) DC bus voltage 47.1 -50 46.95 46.96 46.97 46.98 46.99 47 47.01 47.02 47.03 47.04 47.05 ---------------->Time(secs) d-axis current Operating Condition: Load 15 KW 220 V 50 Hz 0.7 power factor lag
  18. 18. Contd… Results obtained for q-axis quantities Reference Iq* and actual Iq Reference Vt* and actual Vt 80 320 Reference Actual 310 70 290 65 ---------------->Iq(ampere) 300 ---------------->Vterminal(volts) Reference Actual 75 280 270 260 60 55 50 250 45 240 40 230 35 220 46.9 46.92 46.94 46.96 46.98 47 47.02 47.04 47.06 47.08 ---------------->Time(secs) Terminal voltage 47.1 30 46.95 46.96 46.97 46.98 46.99 47 47.01 47.02 47.03 47.04 47.05 ---------------->Time(secs) q-axis current Operating Condition: Load 15 KW 220 V 50 Hz 0.7 power factor lag
  19. 19. Grid Voltage and current with SVC and STATCOM Grid voltage and grid current with SVC connected Grid voltage and current before and after the connection of STATCOM 300 300 200 Voltage Current ---------------->Vgrid(volts),Igrid(ampere) ---------------->Vgrid(volts),Igrid(ampere) Current Voltage 100 0 -100 -200 200 100 0 -100 -200 -300 34.2 34.22 34.24 34.26 34.28 34.3 34.32 34.34 34.36 34.38 ---------------->Time(secs) 34.4 Grid voltage and current with SVC -300 94.9 94.95 95 95.05 95.1 95.15 ---------------->Time(secs) 95.2 Grid voltage and current with STATCOM Operating Condition: Load 15 KW 220 V 50 Hz 0.7 power factor lag 95.25
  20. 20. VAR control in grid connected mode with transient KVAR(Reference and Actual) 2 Reference Actual ---------------->Reactive Power(KVAR) 1.5 1 0.5 0 -0.5 -1 -1.5 -2 94.5 95 95.5 ---------------->Time(secs) 96 96.5 Actual VAR and its reference as wind speed suddenly changes from 8m/s to 9m/s
  21. 21. DC bus voltage required with SVM technique Reference Vdc* and actual Vdc with SVM 800 Reference Actual 790 ---------------->Vdc(volts) 780 770 760 750 740 730 720 710 700 49 49.02 49.04 49.06 49.08 49.1 49.12 49.14 ---------------->Time(secs) 49.16 49.18 49.2
  22. 22. Result of frequency control for standalone mode of operation Actual frequency and its reference 55 Reference frequency Actual frequency 54 ---------------->Frequency(Hz) 53 52 51 50 49 48 47 46 45 46.5 46.6 46.7 46.8 46.9 47 ---------------->Time(secs) 47.1 47.2 Actual frequency and its reference during load switching (from 15 KW to 20 KW) at t=47 seconds 47.3
  23. 23. CONCLUSION AND FUTURE WORK • By this method both standalone and grid connected systems can be operated satisfactorily. • Grid connection is also possible with appropriate control. • Frequency control by pitch control with a slew rate of 12 degrees per second gives good dynamic response. • Though STATCOM control strategy is complex it gives better performance both in steady state and under dynamic conditions . • Voltage control and VAR control by some other converter topology may be proposed. • From the results it can be inferred that with SVM lower DC bus voltage is required indicating better dc bus utilization.
  24. 24. REFERENCES • [1] Wind electrical systems by D. Kastha, S.N. Bhadra and S. Banerjee • [2] Understanding FACTS TECHNOLOGY OF FLEXIBLE AC TRANSMISSION SYSTEMS by Narain G. Hingorani and Laszlo Gyugyi • [3] N.H. Malik and S.E. Hague, "Steady state analysis and performance of an isolated self-excited induction generator", IEEE Trans. on Energy Conversion, Vol. EC-1, No. 3, pp.134-139, September 1986. • [4] T.F. Chan, "Analysis of self-excited induction generators using an iterative method", IEEE PES 1995 Winter Meeting, New York, Jan 29 to Feb 2, 1995. • [5] Analysis and development of a distribution STATCOM for power quality compensation Ph.D thesis by Parthasarathi Sensarma • [6]Synchronous reference frame strategy based STATCOM for reactive and harmonic current compensation M.tech thesis by Arun Karppaswamy B • [7] R. Datta and V. T. Ranganathan, “A simple position-sensorless algorithm for rotor-side field-oriented control of wound-rotor induction machine,” IEEE Trans. Ind. Electron., vol. 48, no. 4, pp. 786–793, Aug. 2001.
  25. 25. QUESTIONS??
  26. 26. THANK YOU
  27. 27. Data of the machine used for simulation Quantities Values Rated Voltage( L-L) 400 V Rated Line Current 67.6 A Number of poles 4 Stator resistance 0.191Ω Stator leakage reactance 1.20mH Rotor resistance referred to stator Rotor reactance referred to stator Rated speed 0.0812Ω Voltage(V) 100 150 200 210 220 230 Current(A) 5.78 8.68 12.44 13.89 16.20 19.10 1.79mH 240 23.15 1440 rpm 250 260 270 28.94 36.46 46.30 Rated H.P. of the machine 50.4 Operating frequency 50 Hz
  28. 28. Magnetization Characteristics of the chosen machine

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