67011097 Wind Generation PSCAD[1]

Manitoba HVDC Research Centre

Wind generators

Variable and fixed speed Induction machines Synchronous and PM machines Doubly fed induction machines Power electronic converters

周铮July 2008


Main components


GE 3.6 MW

Wind speed: 3.5 – 14 – 25 m/sDFIG : IGBT basedSpeed : 8.5 – 15.3 rpmBlade Dia: 111 m

Modern Technology


Vestas V90

Modern Technology

Vestas V90 – 3 MW

Wind speed: 4 – 15 – 25 m/sDFIG : Opti-speedSpeed : 8.6 –16.1 -18.4 rpmBlade Dia: 90 m


Gamesa - G90

Modern Technology

Aerodynamic primary brake by means of full-feathering blades

Hydraulically-activated mechanical disc brake for emergencies

690 V Stator 4 pole machine Gear ratio - 1:120.5

material: Pre-impregnated epoxy glass fibre with carbon fibber

DFIG :Blade Dia: 90 m


Enercon – E82

Modern Technology

Direct drive synchronous generator Pitch control Back- to- back converter grid coupled 6- 19.5 rpm ‘Storm control’ feature


Wind Turbine

• Available power 3...2

1vACP pm

5 7.5 10 12.5 15 17.5 20 22.5 25

0.25

0.5Cp- Tip Speed

0.5

0

Cp W 0( )

255 W( )

Wind_Speed

Hub_Speed

Wind_Speed


IM

Capacitors or SVC

network

Gear box

Direct connected induction machine:

No slip rings/brushes, Squirrel cage machine has a

simple robust construction Less maintenance ‘Fixed speed’ operation

Manitoba HVDC Research CentreTorque Equation in Steady State

TorqueT-Rated

T-s Curve

Torq

ue

7.368 104

8.541 105

T s( )

Trat s( )

0.990 Speed s( )

Operating region of the machine falls over a small speed range.

No reactive power control.

Tor

que

Speed (pu)


Effect of varying rotor resistance in Wound Rotor Machines

0 0.2 0.4 0.6 0.8 10

2 104

4 104

6 104

8 104

7.368 104

1.598 105

T1 s( )

T2 s( )

T3 s( )

T4 s( )

Trat s( )

0.990 Speed s( )

Torque Equation in Steady State

Rrotor increasing

Typical speed variation:+/- 5%


Direct connected induction machine (variable rotor resistance):

IM

Ecap

1.0 [ohm]

1.0 [ohm]

1.0 [ohm]

0.7

[oh

m]

DV733

0.0

01

[oh

m]

DA

DD

DB

DE

DC

DF

2

V729

.00001 [H]

S1

Idc

2.8

20

[uF

]

V730

DIA

DIB

DIC

DID

DIE

DIF

DEC DEB DEA

DEF DEE DED

To rotor

Control rotor resistance with power electronics


RL

RR

L

0.037 [H]

100 MVA Transformer

33/230 kV, Z = 0.1 pu 55 km line

230 kV

230 kV Eq. source

Station AWind Farm

#1 #2VA

S

TL

I M

W

Rro

tor +

Rro

tor +

Rro

tor +

External rotor resistance

1.004

Stot0.037 [H]

BR

KTimedBreaker

LogicOpen@t0

BRK

-0.5

0.0

2Direct connected induction machines:

Poor fault response


Direct connected induction machines:

Poor fault response

Machine must be tripped during faults.

Direct connected IM response to a fault

1.50 2.50 3.50 4.50 5.50 6.50 ... ... ...

0.20

1.00

pu

Vrms

0.9900

1.0400

pu

W

0.00 0.20 0.40 0.60 0.80 1.00 1.20

pu

P1

-1.50 -1.00 -0.50 0.00 0.50 1.00 1.50

pu

Q1


Synchronous machine connected through a ac-dc-ac converter:

With or without gear box Can allow variable speed operation Permanent magnet machine are used as well

SM

network

Gear box


RL

RR

L

0.037 [H]

100 MVA Transformer

33/230 kV, Z = 0.1 pu 55 km line

230 kV

230 kV Eq. source

Station A

Wind Farm

#1 #2

STe

3

AV

Tm

Tm0

Ef0

Tmw

Ef If

VTIT 3

IfEfEf0

Vref

Exciter_(AC1A)

Vref0

S / Hin

holdout

L2N

W

VA

0.037 [H]

BRK

BR

K0

.02

TimedBreaker

LogicOpen@t0

Synchronous machine: Fault response


Synchronous machine: Fault responseMain : Graphs

0.0 2.0 4.0 6.0 8.0 10.0 12.0 ... ... ...

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

pu

Vrms

0.9940

0.9960

0.9980

1.0000

1.0020

1.0040

1.0060

pu

W

0.0

4.50

y

Ef

Main : Graphs

1.0 3.0 5.0 7.0 9.0 11.0 ... ... ...

0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00

pu

Pg

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

pu

Qg


Double fed induction machine:

Wound rotor machine with slip rings ‘Variable speed’ operation P and Q independent control

IM

network

Gear box

DFIG Controls

Current of variable frequency and magnitude are forced into the rotor windings


Double fed induction machine:

Fast control of P and Q ‘Variable speed’ operation – Optimal power tracking at

low wind speeds Store kinetic energy in the rotating system during high

winds

Machine and mechanical system ratings limit operating region.

Rotor crow bar protection during faults Over speed limits.


Doubly-fed Induction Machine

G4

BUS 8

Istator

CTRL

S

TL

I M

W

V

& Controls& Controls

GRIDConverterConverter

GENERATOR

GABCSABC

S2TMODE

TIME

WindTRQ

Wind Park

Tm

Cp

Vw

Wm

0.28

W4

Wspd

Change wind speed fom 12 to 10.5 m/s

D+

F

+

Vw ...

3

-3

Wind_Pert

0


Doubly-fed Induction Machine - Stator flux

IdIqT Iq

Q Id Id and Iq are rotor current components

Controlling rotor current components Id and Iq forms the basis of the Doubly-fed Induction machine concept.

Power electronic based converters are used to force rotor currents into the rotor windings to achieve desired operation.


Circuit and Modules

G4

BUS 8

Istator

CTRL

S

TL

I M

W

V

& Controls& Controls

GRIDConverterConverter

GENERATOR

GABCSABC

S2TMODE

TIME

WindTRQ

Wind Park

Tm

Cp

Vw

Wm

0.28

W4

Wspd

Change wind speed fom 12 to 10.5 m/s

D+

F

+

Vw ...

3

-3

Wind_Pert

0 Ecap

1000

0.0

Ecapref

BR

K

GA

Irc

Irb

T1

T1

D2

T1

T2

D1

T2

D2

T1D1

T2

T4

T5

T6

T3

Erc

Ira

ErbE

ra

GB GC

T2

D1

D2

1.0V

CR-PWM based

Rotor-side converter

Rotor side converter


Vtd

d

t

Position of the Flux Vector

tV

d

Induced voltage is the rate of change of Flux Linkage

Integral of voltage gives the flux linkage across a coil


Vbeta

Vsmag

Vc

Va

Isa

C-

D +Isa

VbC

-D +

phisy

phisx

X

Y Y

r to p

X

mag

phiphsmag

GsT

1 + sT*0.467

*0.467

ValfaG

sT1 + sT

1sT

1sT

phis

A

B

C

3 to 2 Transform

alfa

beta

*0.467Isa

C-

D +

C+

D -Angle

Resolverin out

phis

rotor_angle

Very important signal -

present location ==>

of rotating stator flux

determining the relative difference between

stator flux and rotor position for resolving the

rotor currents

Identification of main stator flux by integrating stator voltage

after removal of resistive drop. The washout filter removes any

dc component from the integrated flux without significantly

ffecting the phase

slpang

Estimation of stator flux vector

Implementation is easier in the Alfa - Beta Fame.

Position of the Flux Vector


Iraa

Irbb

Ircc

Ira_ref

Irb_ref

Irc_ref

slpang

to Stator

D

Q

Rotoralfa

beta

A

B

C

2 to 3Transform

alfa

beta

D and Q reference currents

Generation of current references

Fig. 4: Final step in generation of rotor phase reference currentsEstimation of rotor current injections

Note:• Id controls reactive power• Q controls real power

Circuit and Modules


hy

nhy

T1

T4

Ira_ref

C-

E

+

C-

E

+

C-

E

+ T3

T6

T5

T2

Irb_ref Irc_ref

hy

ira_refira_ref

hy

T1

CPanelhysband

0

10

0.1

C+

E

+

C+

E

-

Current-Reference PWM Controls. Hysteresis band can be adjusted

Ira Irb Irc

*-1

CRPWM Bases firing pulse for rotor side converter

Circuit and Modules

Manitoba HVDC Research CentreSimulation Results

11 11.5 12 12.5 13 13.512

12.5

13

13.5(a)

Vw

ind (

m/s

)

11 11.5 12 12.5 13 13.5

1.15

(b)

Sp

ee

ds

(pu

)

11 11.5 12 12.5 13 13.5200

300

400

500(c)

PG

4 (M

W)

11 11.5 12 12.5 13 13.5100

150

200(d)

QG

4 (M

Var

)

Time (s)

ref

out

Control response and the verification of performance of the model

Step change in wind speed

Controller response to maintain Optimum tip speed ratio

Reduced P output

Constant Q

0 10 20 30 40 500

0.1

0.2

0.3

Cp Wv 10( )

Cp Wv 12( )

Cp Wv 14( )

Wv( )


Wind Inter-connection Requirements Low voltage fault ride through

Dharshana MuthumuniMay 2008


Wind Generators

• Induction machines – Squirrel cage– Wound rotor– Support of switchable caps, SVC or STATCOM

• Induction machines with controls of power electronics (DFIG)

• Synchronous machines

• PM Machines

Manitoba HVDC Research CentreIntegration of wind farms

Wind Farm

wsG

Tl1T

Wind Generators

wsG

RT

Wind Generator 3

wsG

230 kV Bus

RL RRL

#1 #2

Wind Farm

wsG

33 kV Bus

#1#2

Loads

LV Bus

• MH is considering an expansion of up to 400MW wind power

• Connection at either 230KV (transmission) or 66kV levels


Interconnection studies

Once the potential wind sites have been selected, studies are typically carried out to determine the following aspects:

• Direct connection cost estimates and connection scheme- breaker terminations or new station

• Network Upgrade requirement and cost estimates

(Load flow type studies: DC power flow or AC power flow to investigate overloading elements , abnormal voltages and potential impacts on tie line flows)


Interconnection studies

• Dynamic (Stability)performanceo Fault ride througho Power, reactive power controlo Anti-islanding

• Transient studies:o Flicker/harmonicso Starting scheme and inrusho Detailed studies of controls


Interconnection requirements

• Voltage toleranceo The units should operate continuously for voltages in the range

0.9 pu to 1.1 pu at the point of interconnection.

• Frequency toleranceo Under- and over-frequency rangeo Continuous operationo Short time operation (10 minutes, 30 seconds or etc)



• Power controlo Active pitch/stall

control for power adjustment

o Ramp down rate

• Reactive power controlo Maintain voltage level

with the power factor between a minimum of 0.95 over-excited and 0.95 under-excited



• Voltage ride through capabilityo to Reduce the system “shock” o Under-voltage and over-voltage specs



Post disturbance recovery: o Post disturbance recovery of the wind units

should be demonstrated through simulations

Start-up and synchronizing: o Mitigating excessive voltage drops at the point of

interconnection during start up/synchronization.


Large wind farms have to meet very strict operating conditions set out by the system operators.

One of the most important requirements is that they must remain connected and supply power to the electrical system immediately after network faults. This is called the Fault Ride Through Capability (FRT).

This is to ensure the stable operation of the power system during high wind periods when the wind generation could be supplying a significant level of power to the system.

Fault Ride Through Capability requirements



Utility Grid Codes define the FRT requirement that the Wind Farm owner has to conform. These standards are not uniform an vary from one system owner to he other.



ELTRA- 3 phase faults cleared in first protection zone- 2 phase faults with unsuccessful re-close – 100-50 ms.- Faults with 60%-80% voltage- 1-0 s.- Restrictions on Crow-Bar operation to maintain control capabilities.

NEMMCO (Australia)- Zero voltage for up to 175 ms followed by

- 80% -100% voltage for 10 s- 90% -100% voltage for 3 min.


The characteristic of the generator plays an important role . • Synchronous• Induction• DFIG

The machine will not be tripped during the specified fault duration.• Larger winding currents for a longer duration• Larger magnetic forces• Higher rotation speed – Mechanical stress

The wind turbine will not be disconnected/stopped during this period.

• Higher stress on blades


FRT Requirements places technical challenges and increased equipment cost.


Fault Ride Through – Synchronous machine

• Field winding will act to increase the terminal voltage. This will help ‘push’ more power to the network during the recovery period.

•Fast response of he field circuit helps fault recovery.


Fault Ride Through – Induction machine

No reactive power control available.

Voltage drop makes the shunt capacitors (or SVC) ineffective.

Speed (slip) increases during the fault.

Increased slip causes more reactive power to flow into machine. This causes a voltage drop after fault and reduce power output capability.


Fault Ride Through – DFIG

Overcomes main drawbacks of the normal Induction machine

Power can be delivered at any slip (speed) through control of rotor current.

Crowbar reduces effectiveness of DFIG fault recovery.


Fault Ride Through – Equipment considerations

-Units with high inertia generally can recover faster than those with lower inertia.- Less speed fluctuations.- High cost- Larger, heavier

-Special designs and new technology required- Sophisticated control.- New generator concepts


Main,DGIF_Controls : Graphs

0.60 3.00 ... ... ...

0.650

1.100

KV

(kV

)

Vgrms_pu

1.0900

1.1150

sp

ee

d_

pu

w pu Wref_

0.0

400

KW

Pg

-25.0

20.0

KW

Qg Qg_ref

9.0000

10.0000

pu

Ecap

1.0

8.0

KA

Ird

38.0

56.0

KA

Irq

Grid rms voltage, generator rotor speed, active power, reactive power, DC-link voltage and (ird & irq,) generator current, response to weak voltage dip


Grid rms voltage, generator rotor speed, active power, reactive power, DC-link voltage and (ird & irq,) generator current, response to strong voltage dip


0.60 3.00 ... ... ...

0.650

1.100

KV

(kV

)

Vgrms_pu

1.0900

1.1150

sp

ee

d_

pu w pu Wref_

0.0

400

KW

Pg

-25.0

20.0

KW

Qg Qg_ref

9.0000

10.0000

pu

Ecap

1.0

8.0

KA

Ird

38.0

56.0

KA

Irq



0.60 3.00 ... ... ...

0.20

1.10

KV

(kV

) Vgrms_pu

1.090

1.160

sp

ee

d_

pu

w pu Wref_

0.0

400

KW

Pg

-40.0

20.0

KW

Qg Qg_ref

9.0000

10.0000

pu

Ecap

-2.00

8.00

KA

Ird

38.0

56.0

KA

Irq

Grid rms voltage, generator rotor speed, active power, reactive power, DC-link voltage and (ird & irq,) generator current, , response to strong voltage dip


Vw

Wind speed signal

G1 + sT Wref_

N

D

N/D

10.909

Optimal

Tip Speed Ratio

Speed Reference

I

P

D +

F

-Wpu

Speed Reference

Wref_

G1 + sT

Iq_ref

Reference machine speed to maintain Tip- Speed ratio

When machine speeds up, Iq_ref increases in an attempt to increase power output.

Simple Power control loop used in the simulation


Wind Power Wind speed distribution Short term wind speed variations Modeling wind speed System impact

Dharshana MuthumuniMay 2008


Wind Speed Distribution

• Typical wind speed histogram

Renewable and Efficient Electric Power Systems, G.M. Masters


Short term wind speed variationsTurbulence


Modeling Short term wind speed variations

Wind gusts – sinusoidal variation Wind ramps Noise

Gusts, ramps and noise can be superimposed onto a ‘mean wind speed.’

Gusts, ramps, etc. can be defined by magnitude and duration.


Wind turbine controls should be able to function through wind speed fluctuations.

Mean wind speed Wind gust Wind ramp Noise

Main : Graphs

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 ... ... ...

2.0

4.0

6.0

8.0

10.0

12.0

14.0

y

Wind_speed

Main : Graphs

0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 ... ... ...

8.00

8.50

9.00

9.50

10.00

10.50

11.00

y

Wind_speed

Main : Graphs

0.420 0.440 0.460 0.480 0.500 0.520 0.540 0.560 0.580 0.600 ... ... ...

8.00

8.50

9.00

9.50

10.00

10.50

11.00

y

Wind_speed

Gust Ramp

Noise



Vw

Wind Source

GustMean

RampNoise

TmVw

Beta

W P

Wind TurbineMOD 2 Type

Wind TurbineGovernor

Wm

Beta

PgMOD 2 Type

PSCAD allows modeling of mean wind speed, gusts, ramps and noise.



Different parameters can be defined by the user.



Recorded wind speed data (speed vs time) can be used in a PSCAD simulation


Modeling Short term wind speed variations PSCAD file read unit.

windvariation.txt

w indvariation.txt

Main : Graphs

0.0 0.1k 0.2k 0.3k 0.4k 0.5k 0.6k 0.7k 0.8k 0.9k 1.0k ... ... ...

4.0

5.0

6.0

7.0

8.0

9.0

10.0

m/s

Wind speed



Tutorial: Simple grid example and the effect of variable wind.


Thank you…

Pgen

Iar

Ibr

Iar Ir Ir

PitchAngle

Vw

39

.0

La

mb

da

S1

**

1.623

dwmD +

F

+ wmN

D

N/D

Te

wm

wg

1.0

wg

slip

slip

Vw

0.66

0.04Beta_Opt

Beta_Opt

Lambda

18

8.4

95

6

beta_star

Pitch_Angle

Cp

Iref

PitchAngle

N

D

N/D

SlipCalculation

wg

ws

Slip

x

y

z

x

y

VT80_EMTDC.txt

Te

Hub Speed

RotorCurrent

Computer

wr

Iar

Ibr

Ir

RotorCurrent

Modulator

Iref

Ir

S

PowerControl

slip

opt

Pset

I_ref

P_act

Pitc

hC

on

tro

ller

be

ta*

be

ta

SpeedControl

Vw

s_ref

opt

slip

Cp

Lambda

Hub Speed

Optimum Pitch Angle

Silp

Documents

67011097 Wind Generation PSCAD[1]