lvrt induced frequency stability in offshore wind power ......2019/12/09 · ofwf dc chopper option...

LVRT Induced Frequency Stability in Offshore Wind Power System

M. M. Kabsha, Zakir H. Rather IIT Bombay, India

2nd International Conference on: Large-Scale Grid Integration of Renewable Energy in India 4-6 Sept 2019

Outline

• Introduction • OWF LVRT Requirements • OWF Modelling • OWF LVRT Capability • Results and Discussion • Conclusion

26 November 2019 4-6 Sept 2019 ,2nd International Conference on Large-Scale Grid Integration of Renewable Energy in India 2

Statistics of Global Wind Power Installation


24 31 39 48 59 74 94 121

159 198

238

293 319

370

433

488

540 591

0

100

200

300

400

500

600

700 Global Cummulative Installed Wind Capacity 2001-2018

GW

Global Wind Energy Council (GWEC), “GWEC Report 2018,” 2019.

1 2

3 4

5 7

8

12 14

19

23

0

5

10

15

20

25

30

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

Global Cummulative Installed Offshore Wind Capacity 2008-2018

GW

OWF LVRT Requirements


TenneT TSO GmbH, “Requirements for Offshore Grid Connections in the Grid of TenneT TSO GmbH,” 2012.

0 150 700 1.500 3.000 Time in ms

0

0.7

0.45

0.9

1

FRT: Fault Ride Through

STI: Short Term Interruption

FRT without separation

STI is allowed

Tripping is allowed

M

axim

um L

-L v

olta

ge U

/ UN

24

3

Time when a fault occurs

FRT without separationPossibly STI

1

2

3

4

1Voltage drop / rise (%)

ΔU/Un

Reqiured additional reactive current (%)ΔI/In

Support of the voltage by voltage control

5 %-50

100 %

-100%

-5 %ΔU = U-Uo, ΔI=I-Io

Tennet TSO GmbH, “Grid Code - High and extra high voltage,” November, 2015


OWF Modelling

Full Converter based WTG and WF


Grid Side Converter

Machine Side Converter

DC_Link

ACOffshore

Vdc

Vdcref

PMSG

SN

Qg

Qgref

Qgrid

Qref

Pgrid

Pref

Vdc

Vg

Qgrid

Pgrid

PIPI

i*d MSC i*

q MSC i*d GSC i*

q GSC

PIPIfmeas

MPPTω

Vmeas

Kf

Vref

Kvfref

Pred

Qgrid

Pgrid

Offshore Wind Farm

PMSG

SN

PMSG

SN

PMSG

SN

MSC GSC

MSC GSC

MSC GSC

WTG

M. Pöller and S. Achilles, “Aggregated Wind Park Models for Analyzing Power System Dynamics,” in 4th International Workshop on Large-scale Integration of Wind Power and Transmission Networks for Offshore Wind Farms, 2003, pp. 1–10

HVDC Converter Control


Receiving End Converter

Sending End Converter

DC CablesFilterFilter

Vdc

Vdcref

Vac

Vacref

PI

i*d SEC

PI

i*q SEC

𝟐𝟐𝟐𝟐𝒔𝒔

θ*

0

Fref

i*d REC i*

q REC

ACOffshore

ACOnshore

Qoff

Poff

Qon

Pon

Vref Vmeas

Kf

Kv

Vdc Vdcref

KLVRT

S. Dennetière et al., “The CIGRE B4 DC Grid Test System,” CIGRE Electra Mag., 2013

Test System


Modified IEEE 39 bus

Wind Farm no

Generator Replaced

No of WT Total MW

1 G 4 469 703.5

2 G10 186 279

3 G 7 416 624

4 G 3 482 723

5 G 9 617 925.5

G10

G8

G6

G1

G2

G5 G4

G3

G7

G9

30 25

37

26 28

38

29

1 3

18 17 24

35

2221

23

363334

19

4

5

6

7

8

14

15

16

12

11

10

31

32

9

20

2

WF 2

WF 1

WF 4

WF 3

WF 5

4847

40

39

49

41

42

44 43 46

45

REC SECAC

Offshore GSC MSCPMSG

SN≡

ACOnshore

P. Demetriou, M. Asprou, J. Quiros-Tortos, and E. Kyriakides, “Dynamic IEEE Test Systems for Transient Analysis,” IEEE Syst. J., vol. 11, no. 4, pp. 1–10, 2015.


OWF LVRT Capability

Capability to satisfy LVRT


Onshore Converter

Offshore Converter

DC Cables PCC

Offshore AC Voltage Regulation

Kf

foff*

foff

Offshore Frequency RegulationVDC

VDCoff*

KV

VAC,off*

VAC,off

VDC VDCoff

*

OFWF

DC Chopper

Option 2

Option 1

Option 3

Option 1

Option 1

Conventional LVRT Strategy


*0 0off off v dcoff dcV V K V V = − −

*0 0off off v dcoff dcf f K V V = + −

( )*

1

0 0

LVRT ref meas

qREC

flt K V V

Iflt

= −= =

( )*red ref meas vP V V K= −

( )*red ref meas fP f f K= −

ref MPPT redP P P= −

(2)

(2)’

(1)

(1)’ (3)

(4)

Grid Side Converter

Machine Side Converter

DC_Link

ACOffshore

Vdc

Vdcref

PMSG

SN

Qg

Qgref

Qgrid

Qref

Pgrid

PMPPT

Vdc

Vg

Qgrid

Pgrid

PIPI

i*d MSC i*

q MSC i*d GSC i*

q GSC

PIPIfmeas

MPPTω

Vmeas

Kf

Vref

Kvfref

Pred

Qgrid

Pgrid




Vdc

Vdcref

Vac

Vacref

PI

i*d SEC

PI

i*q SEC

𝟐𝟐𝟐𝟐𝒔𝒔

θ*

0

Fref

i*d REC i*

q REC

ACOffshore

ACOnshore

Qoff

Poff

Qon

Pon

Vref Vmeas

Kf

Kv

Vdc Vdcref

KLVRT

Active Power Recovery


(With Ramp Rate) (Without Ramp Rate)

Fault Clearance Time

Ramp Time

Ramp Rate

0

0.75

0.25

1

PCC

Vol

tage

(p.u

)

V (p.u)

0.5

0

0.75

0.25

1

Act

ive

Pow

er (p

.u)

P (p.u)

0.5

0 150 1,500 3,000Time in ms 5,150


0 150 1,500 3,000Time in ms 5,150


0 150 1,500 3,000Time in ms 5,150


0 150 1,500 3,000Time inm s

0

0.75

0.25

1PC

C V

olta

ge (p

.u)

Time when a fault occurs

5,150

V (p.u)

0.5

0

0.75

0.25

1

Act

ive

Pow

er (p

.u)

P (p.u)

0.5

Modified Conventional LVRT Strategy





Vdc

Vdcref

Vac

Vacref

KLVRTPI

i*d SEC

PI

i*q SEC

𝟐𝟐𝟐𝟐𝒔𝒔

θ*

0

Fref

i*d REC i*

q REC

ACOffshore

ACOnshore

Qoff

Poff

Qon

Pon

Vref Vmeas

Kf

Kv

Vdc Vdcref

Equations (1) to (5)idref

FaultDetection

( )

*

*

11 0

0 1

d REC dref rampupramp

d REC dref

flt and i i and tRS

flt or i i

= < < =

= =

( ) * *lim , ,

ramp rampREC RECramp down d up dramp

dref dd

REC REC

dV dVR i R ii - idi dt dtdt t V V

− − =

∆

1

0

rampd ramp

refd

dref ramp

i Si

i S

== =

(1)

(2)

(3)

*

1

0

dmax

d RECrefd

i flti

i flt

== =

(4)

(5) ( )

*

1

0 0

LVRT ref onshore

q REC

K V V flt

iflt

− == =

(6)

( ) ( )22 *max 0.95

0.95

q REC onshore

dmax

max onshore

i i V

ii V

− <= ≥

(With APR Ramp Rate)


Results and Discussion



Test Case I 3-ɸ Fault with 70 % voltage dip for 500 milliseconds,

and wind generation (penetration level of 33%)

Ramp Rate

f Nadir (Hz)

RoCoF (Hz/s)

τ Nadir (p.u)

RoCoT (p.u/s)

𝜔𝜔turbine (p.u)

0.2 p.u /s 49.43 -0.88 0.46 0.27 1.075

0.5 p.u /s 49.69 -0.55 0.58 0.41 1.0378

1 p.u /s 49.87 -0.38 0.63 0.39 1.0275

2 p.u /s 49.92 -0.27 0.644 0.38 1.0235

0 1 2 3 4 5 6 70

0.3

0.6

0.9

1.2

Bus

16

Vol

tage

(p.u

)

Ramp Rate 0.2 pu/s

Ramp Rate 0.5 pu/s

Ramp Rate 1 pu/s

Ramp Rate 2 pu/s

0 1 2 3 4 5 6 7500

1000

1500

2000

2500

PR

EC

Tot

al(M

W)

0 1 2 3 4 5 6 7500

1000

1500

2000

2500

PSE

C T

otal

(MW

)

(b)

(c)

(a)

0 1 2 3 4 5 6 749.2

49.4

49.6

49.8

50

50.2

FO

nsho

re(H

z)

0 1 2 3 4 5 6 7-1.5

-1

-0.5

0

0.5

RoC

oFO

nsho

re (H

z/s)

0 1 2 3 4 5 6 7

time (s)

-500

0

500

1000

1500

QR

EC T

otal

(MW

)(f)

(e)

(d)

0 1 2 3 4 5 6 70.9

1

1.1

1.2

VD

C O

WF1

(pu)

0 1 2 3 4 5 6 70.9

0.95

1

VA

C O

WF1

(pu)

0 1 2 3 4 5 6 7200

400

600

800

PG

SC O

WF

1(M

W)

(g)

(h)

(i)

0 1 2 3 4 5 6 70

0.5

1

1.5

WT

OW

F1 (p

u)

0 1 2 3 4 5 6 7

-1

-0.5

0

0.5

RoC

oTW

T (p

.u/s)

0 1 2 3 4 5 6 7

time (s)

1

1.1

1.2

WT

OW

F1(p

u)

(k)

(j)

(l)



Ramp Rate

f Nadir (Hz)

RoCoF

(Hz/s)

τ Nadir (p.u)

RoCoT (p.u/s)


0.2 p.u /s 48.9 -1.85 0.33 0.243 1.1

0.5 p.u /s 49.4 -1.7 0.465 0.49 1.05

1 p.u /s 49.7 -1.48 0.57 0.45 1.03

2 p.u /s 49.9 -1.17 0.67 0.35 1.022

0 1 2 3 4 5 6 70

0.3

0.6

0.9

1.2

Bus 1

6 V

olta

ge (p

.u)

Ramp Rate 0.2 pu /s

Ramp Rate 0.5 pu /s

Ramp Rate 1 pu /s

Ramp Rate 2 pu /s

0 1 2 3 4 5 6 7

1000

2000

3000

PR

EC T

otal

(MW

)

0 1 2 3 4 5 6 7

1000

2000

3000

PSE

C T

otal

(MW

)

(b)

(c)

(a)

0 1 2 3 4 5 6 748.5

49

49.5

50

50.5

FO

nsho

re(H

z)

0 1 2 3 4 5 6 7-2

0

2

RoC

oFO

nsho

re (H

z/s)

0 1 2 3 4 5 6 7

time (s)

-500

0

500

1000

1500

QR

EC T

otal

(MW

)(f)

(d)

(e)

0 1 2 3 4 5 6 70

0.5

1

1.5

WT

OW

F1 (p

u)

0 1 2 3 4 5 6 7-1.5

-1

-0.5

0

0.5

RoC

oTW

T (p

.u/s)

0 1 2 3 4 5 6 7

time (s)

1

1.1

1.2

WT

OW

F1(p

u)

(k)

(j)

(l)

0 1 2 3 4 5 6 70.9

1

1.1

1.2

VD

C O

WF1

(pu)

0 1 2 3 4 5 6 70.9

0.95

1

VA

C O

WF1

(pu)

0 1 2 3 4 5 6 70

200

400

600

800

PG

SC O

WF

1(M

W)

(g)

(h)

(i)

Test Case II 3-ɸ Fault with 100 % voltage dip for 150 milliseconds,

and wind generation (penetration level of 46%)


Test Case I (70 % voltage dip for 500 milliseconds)

(penetration level of 33%)

Ramp Rate

f Nadir (Hz)

RoCoF (Hz/s)

τ Nadir (p.u)

RoCoT (p.u/s)


0.2 p.u /s 49.43 -0.88 0.46 0.27 1.075

0.5 p.u /s 49.69 -0.55 0.58 0.41 1.0378

1 p.u /s 49.87 -0.38 0.63 0.39 1.0275

2 p.u /s 49.92 -0.27 0.644 0.38 1.0235

Ramp Rate

f Nadir (Hz)

RoCoF (Hz/s)

τ Nadir (p.u)

RoCoT (p.u/s)


0.2 p.u /s 48.9 -1.85 0.33 0.243 1.1

0.5 p.u /s 49.4 -1.7 0.465 0.49 1.05

1 p.u /s 49.7 -1.48 0.57 0.45 1.03

2 p.u /s 49.9 -1.17 0.67 0.35 1.022

Test Case II (100 % voltage dip for 150 milliseconds)

(penetration level of 48%)

Conclusion

• The results suggest that the VDIF is significantly improved by increasing APR ramp rates.

• With increasing the APR ramp rate the RoCoT is increased, however the WTG rotational speed decreased.

• The WTG mechanical stress decreased slightly at high APR ramp rates.

• The wind generation penetration levels and grid fault severity may significantly impact frequency stability of onshore main grid.


Thank you


lvrt induced frequency stability in offshore wind power ......2019/12/09 · ofwf dc chopper option...

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