# Wind Energy and grid integration

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```					                          WIND FARM
Flexible AC Transmission Systems
WIND ENERGY AND GRID INTEGRATION

Jacques COURAULT
SUMMARY
Assumption:
Wind farm is with Fixed Speed
Induction Generator (FSIG)

1/ Wind farm operation WITHOUT compensation:
Single line diagram / main assumptions
Physical aspects - System behaviour,
Main factors on system behaviour,
Simulations.
2/ Wind farm operation WITH DYNAMIC compensation:
Single line diagram,
Design,
Simulations,
3/ Conclusion & cost mitigation

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REQUIREMENTS
Fault initial point
P.O.12.3
Voltage
(pu)
1
Operation                                     0,95 pu
0,8
area (no trip)

R ED
Fault recovery                                EL ÉC T RI C A
0,2                                                                             D E ESPA Ñ A
Fault duration

0        0,5         1            15        Time (sec.)
Fig 4.1                        Ireactiva / Inominal (pu)                Fault & recovery   Normal operation
1
0,9

Generation

R ED                                                              of reactive

EL ÉC T RI C A
(Supply by D-STATCOM)                         Voltage at
D E ESPA Ñ A
grid
0                                                 connection
0,5        0,85                  point (pu)
Reactive
Fig 4.2                       consumption

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1 – WIND FARM OPERATION
WITHOUT COMPENSATION

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WITHOUT compensation / Single line diagram

HV transformer                                   MV transformer
220 / 25 kV                                      25 kV / 660 V
x=12%                                            x=5%

FSIG
MV line 25 kV 20 km
HV line
220 kV
High Pcc
Wind

Assumptions:
induction, fixed speed generator,
in principal, network arrangement,
wind-farm power: from 30 to 50 MVA (approach in pu)

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WITHOUT COMPENSATION
Fault phase (phase 1)                         PHYSICAL ASPECTS
active energy / mechanical behaviour:
During Fault Pmeca= Constant,
Mechanical acceleration according to Inertia,
Slip of induction generator is increasing,
Torque at induction generator is decreasing (square of the voltage).

Reactive current injection
Generator Voltage > Network Voltage,
Short time duration ~T’s (opened rotor time constant).

Recovery phase (phase 2)                                             1     2

High amount of reactive current.

U network

Iq Generator

Speed or slip

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MAIN FACTORS ON SYSTEM
BEHAVIOUR

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MAIN FACTORS ON SYSTEM BEHAVIOUR
GLOBAL VIEW
9MW Wind Farm Simulation
Scc 2500MVA at 120kV Bus                         Scc 55MVA at 25kV Bus

Voltage (pu)
1 pu

3 phases voltage
drop

0.2 pu
0           0.5   Time (sec)

Phase 1
Fault
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MAIN FACTORS ON SYSTEM BEHAVIOUR
GLOBAL VIEW- SIX WIND TURBINES

25 kV

Matlab / Simulink simulation from HQ

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MAIN FACTORS ON SYSTEM BEHAVIOUR
SYSTEM PROTECTIONS

AC Overcurrent (Inst)
AC overcurrent (positive seq.)
AC current imbalance
AC undervoltage (positive seq.)
AC overvoltage (positive seq.)
AC voltage unbalance (negative seq.)
AC Voltage unbalance (Zero seq.)
Underspeed
Overspeed

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Wind Farm Simulation
WITHOUT compensation
9MW Wind Farm (With pitch control, pitch rate 2°/s)
at wind turbine bus

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WIND FARM SIMULATION WITHOUT
COMPENSATION
PITCH CONTROL - SYNTHESIS

9MW Wind Farm (With pitch control, pitch rate 2°/s)
With taken assumptions
Fault duration 500ms
protection levels
Wind Farm won’t trip with the help of pitch control DURING fault
recovery
High reactive power consumption during fault recovery untill pulling
in.
No respect of Fig 4.2 of P.O.12.3

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2 - WINDFARM OPERATION
WITH COMPENSATION

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WITH COMPENSATION - SINGLE LINE DIAGRAM

HV transformer                               MV transformer
220 / 20 kV                                  20 kV / 660 V
x=12%                                        x=5%
HV line                                INTW IGEN
220 kV                                                              FSIG   Wind
High Pcc             MV line
25 kV
20 km               D-STATCOM

ID-STATCOM=INTW+IGEN

Assumptions:
identical to previous ones:
induction, fixed speed generator,
-in principal, network arrangement,
-wind-farm power: from 30 to 50 MVA (approach in pu),
- VSC equipment,
- installed power in pu.
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Wind Farm Simulation
With D-STATCOM
9MW Wind Farm (with pitch control pitch rate 2°/s)
at Wind turbine (D-STATCOM 19.5MVA ~2.16 p.u. )

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WIND FARM SIMULATION
WITH D-STATCOM

9MW Wind Farm (with pitch control pitch rate 2°/s)
With taken assumptions
With the help of 2.16 p.u of D-STATCOM,
No reactive power consumption during fault and after recovery
Respect of 1 p.u current injection at Pcc during fault

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3 - CONCLUSION
&
COST MITIGATION

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WITHOUT / WITH D-STATCOM – 9 MW WIND FARM
Without dynamic compensation                               With 19.5 MVAR D-STATCOM

0.5 s
2.5 s                                            0.35

Generator                                                               -13 MVAR

0.35

No respect of Fig 4.2 of P.O.12.3
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WIND FARM WITH COMPENSATION
CONCLUSION

ASSUMPTION: Fixed Speed Induction generator case
MAIN CONCLUSION:
Case by Case study
Network data
-   Impedance of Connecting transformer and line

Wind turbine data:
-   type of active power and speed control
-   design for protection levels
-   Inertia

Generator data
-   Curve Torque/slip
-   ratio sk/sn and Tek/Ten

Huge amount of reactive power needed during faults …

20        WIND ENERGY AND GRID INTEGRATION - Madrid 24-25 January 2006   20
WIND FARM WITH COMPENSATION
COST MITIGATION
ASSUMPTION: Fixed Speed Induction generator case
Costs mitigation
Power electronics VSC has a typical overload capability of 2 - 2.3
Keeping our case study: SVS size = 1.15 p.u with x 2 overload capability
To reduce costs:
Splitting SVS in D-STATCOM and MSC
Splitting SVS in D-STATCOM and TSC.
…/…

R
D-STATCOM
TSC                                       Rough average price for
10 Mvar 1 M€
2.5 time continuous for up 2 s

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10 Mvar peak                     1 M€ …. EXPENSIVE….

BUT … In normal operation
the STATCOM …
May control cos φ
May eliminate the negative sequence.
Can be a active filter

STATCOM – VSC (PWM)                                         Can be a dynamic damper.

Just for cos φ and negative sequence, the simple
SVC is a good solution.

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