operation of offshore wind power plants connected with hvdc · 2015-02-11 · operation of offshore...

O. Gomis-Bellmunt (IREC / CITCEA-UPC)

with support from M. de-Prada, A. Egea, J.L. Dominguez, E. Prieto, J. Sau, F. Diaz and M. Aragüés

Operation of offshore wind power plants connected with HVDC

Trondheim, February 2015

Agenda

• Context. Offshore wind power plants connected with VSC-HVDC.

• Functional requirements for offshore WPP connected with VSC-HVDC.

• Coordinated control for power reduction. • Conclusions.

2 Operation of offshore wind power plants connected with HVDC, O.Gomis



• Example of coordinated control for power reduction.

• Conclusions.


G

LV 50 Hz

MV 50 Hz

G

LV 50 Hz Other WTs Main grid

Fix Speed onshore WPP

Energy capture Fault ride-through Grid support

Main grid HV 50 Hz

G LV VF

LV dc

LV 50 Hz

MV 50 Hz

G LV VF

LV dc

LV 50 Hz Other WTs HV 50 Hz

HVAC Offhore WPP

HVAC cable

HVAC cable Compensation required Long cables (>50-80 km) not possible

G LV VF

LV dc

LV 50 Hz

MV 50 Hz Other WTs Main grid

Variable Speed onshore WPP

LV VF

LV 50 Hz

G

G LV VF

LV dc

LV 50 Hz

MV 50 Hz

G LV VF

LV dc

Other WTs

VSC-HVDC, Offhore WPP Main grid HV 50 Hz

HVDC cable

HV 50 Hz

Same WT DC cables VSC-HVDC technology

Bard Offshore 1 (BorWin 1) 400 MW First offshore WPP with VSC-HVDC First WT in 2010 To be completed in 2013


G LV VF

LV dc

LV 50 Hz

MV 50 Hz

G LV VF

LV dc

Other WTs

Multiterminal VSC-HVDC

AC grid HV 50 Hz

Multiterminal HVDC system

HV 50 Hz

G LV VF

LV dc

LV 50 Hz

MV 50 Hz

G LV VF

LV dc

Other WTs

AC grid HV 50 Hz

HV 50 Hz


G LV VF

LV dc

LV 50 Hz

MV 50 Hz

G LV VF

LV dc

Other WTs

VSC-HVDC grid

AC grid HV 50 Hz

HVDC grid

HV 50 Hz

G LV VF

LV dc

LV 50 Hz

MV 50 Hz

G LV VF

LV dc

Other WTs

AC grid HV 50 Hz

HV 50 Hz


G LV VF

LV dc

LV

MV

G LV VF

LV dc

Other WTs

Point to point VSC-HVDC with an offshore AC hub

AC grid HV 50 Hz

Point to point HVDC

HV

G LV VF

LV dc

LV

MV

G LV VF

LV dc

Other WTs

AC grid HV 50 Hz

HV

Point to point HVDC

AC hub

Mainstream Renewable Power

AC cable


HVDC technology concepts for future transmission systems for

offshore wind • Point to point HVDC • Multiterminal HVDC • HVDC grid • Offshore AC hubs • AC systems with HVDC links • All the previous combined

8

Germany Takes the Lead in HVDC, IEEE Spectrum 2013

Friends of the Supergrid

Siemens

Operation of offshore wind power plants connected with HVDC, O.Gomis

WPP concepts

– AC WPP standard/non-standard frequency

– AC WPP variable frequency

– DC WPP

– Hybrid DC-AC

9

Cost? Efficiency? Reliability? Availability? Maintainability?

http://www.bard-offshore.de/en


AC collection

AC Export cable AC

DC

HVDC transmission

Offshore Platforms

AC

DC

DC

AC

10

Mikel de-Prada et al. “Analysis of DC Collector Grid for OWPP” 12th Wind Integration Workshop, London, October 2013

• WPP AC voltage ratings ↑↑ 33 kV → 66 kV?

• 50/60 Hz? non-standard frequency? Variable frequency?

• Normally with Type 3 (DFIG) and Type 4 (FPC) Wind Turbines


~=

~=

Cluster 1

Export Cable

ConverterTx

ON

SH

OR

E

OFFS

HO

RE

Rectifier Inverter

AC Grid Onshore

To WTGs

Substation Offshore Wind Farm 1

Substation Offshore Wind Farm 2

Cluster 2

Converter Station

Grid Connection System

String 1

String 2

Em

ergency P

ower

Cigré WG B4-55 HVDC connection of offshore wind power plants (under development)


Projects (WPP with VSC-HVDC) with AC collection 50 Hz

12

Borwin 1 (Transpower offshore, 2009, +/- 150 kV, 400 MW,125+75 km) for BARD Offshore 1 - 2x1 km DolWin 1 (TenneT, 2013, +/- 320 kV, 800 MW, 75+90 km) for Meg Offshore 1 - 2x13 km and Borkum West II - 2x7.5 km DolWin 2 (TenneT, 2015, +/- 320 kV, 900 MW, 45+90 km) for Gode Wind I - 7 km and Gode Wind II - 12 km Borwin 2 (Transpower offshore, 2014, +/- 300 kV, 800 MW,125+75 km) for Veja Mate – 2x10 km and GlobalTech 1 – 2x30 km Helwin 1 (Transpower offshore, 2014, +/- 250 kV, 576 MW,85+45.5 km) for Nordsee Ost – 2x4.2 km, Meerwind phase 1 – 2x7.6 km and 2 – 2x 20 km Sylwin 1 (TenneT, 2014, +/- 320 kV, 864 MW, 159 + 45.5 km) for Dan Tysk– 2x9.7 km, Butendiek – 2x40 km and Sandbank 24 – 2x35 km Helwin 2 (TennetT, 2015, +/- 320 kV, 690 MW,85+45.5 km) for Amrumbank – 3x8 km, Hochsee Testfeld Helgoland – 2x4 km and Kaskasi – 2x3.5 km DolWin 3 (TenneT, 2017, +/- 320 kV, 900 MW, 84.5+76.5 km) for OWP Borkum Riffgrund West 1, OWP Borkum Riffgrund West 2 and OWP Borkum West 2





• Conclusions.


WPP connected to VSC-HVDC Functional requirements

• Collect the wind power and inject it in the VSC-HVDC cable

• Provide support to the main AC grid • Provide support to the DC grid (if exists) • Ensure the proper offshore grid operation • Maintain stability in normal and fault conditions


WPP connected to VSC-HVDC Functional requirements

Specific requirements: • Reactive power management. Offshore grid voltage control (HVDC rectifier + WTs) • Active power management • Offshore grid frequency control (VSC-HVDC rectifier) • Start/stop sequence • Fault ride-through capability • Main grid support:

– Voltage support – Frequency support may be required – Virtual (synthetic inertia) may be required – Power oscillation damping may be required

• Control coordination between WPP control and VSC-HVDC control • Operation under communication failure • Provide auxiliary power to the WPP when there is no available generation (no wind

or excessively high wind)


Normal operation

16

Draft from Cigré B4-55 WG “HVDC connection of offshore WPP”

~=

Offshore Converter

OnshoreConverter

AC Grid Onshore

Converter Station

~=

Substation

Emergency

Power

Transformer Platform 1

P

P

P

P

P

P

P

P

P

P

P P


Restricted operation

17



Main AC grid fault

18


~=

Offshore Converter

OnshoreConverter AC Grid

Onshore

Converter Station

~=

Substation

Emergency

Power


P

P

P

P

P

P

P

P

P

P

P Fault

PHVDC chopper actuation


WPP fault

19


~=

Offshore Converter

OnshoreConverter

AC Grid Onshore

Converter Station

~=

Substation

Emergency

Power


P

P

P

P

P

P

P

P

P

Fault

P

P P


Export cable fault

20


~=

Offshore Converter

OnshoreConverter

AC Grid Onshore

Converter Station

~=

Substation

Emergency

Power


P

P P

Fault

Wind turbine power reduction

P

P

P

P


Frequency response using WPP control

21


~=

Offshore Converter

OnshoreConverter

AC Grid Onshore

Converter Station

~=

Substation

Emergency

Power


P

P

P

P

P

P

P

P

P

P

P P

Power reductionWPP CONTROL

GRIDOPERATOR

Onshore frequency /

WPP required active power


Frequency response using VSC-HVDC converters

22


~=

Offshore Converter

OnshoreConverter

AC Grid Onshore

Converter Station

~=

Substation

Emergency

Power

Transformer Platform 1P

P

P

P

P

P

P

P

P

P

P P

Frequency Change

Onshore frequency /

WPP required active power





• Conclusions.


Operation of offshore wind power plants connected with HVDC, O.Gomis 24

Example coordination for power reduction

VSC-HVDC DBR Wind turbine DBR

Pitch angle

• How can we provide power reduction (without fast communication between offshore and onshore VSC-HVDC)?

– Onshore VSC-HVDC DBR, fast but available limited time. (not offshore ->footprint!) – Wind turbine DBR, fast but available limited time. – Pitch angle. Slow response but good for steady-state. – Fast wind turbine torque reduction with the power converter? Electrically possible, but

not allowed. (Turbine loads)


25

PhD thesis, Agustí Egea (CITCEA-UPC)

WFC

E1

I1 GSC

E2

Cable 1

Inner loopilq*

Droop control

vlqd

E2*

ilqd

ilabc

vlabc vzabc

MPPT

Inner loop

iwtabc

T[θ]-1θg

θg

iwtabc

iwtqd

iwtqd

vwtabc

*

Inner loop

ipqd

vpqd

vpabc

*

ipabc

DC loop

Ewt

vpabc

vrabc

vrqd

Ewt*

ipqd

Ewt

T[γ]-1

vzabc

vlabc

vlqd vlabc

ilabc

E2

Inner loop

T[δ]-1

icqd*

Voltage loop

T[δ]

vcqd

icqd

vtabc

vtqdvcabc

icabc

icabcinabc

vcabc

inabc inqdvcqd*

vwtqd

vrabc

GSC chopper

E2

WTCWGC

∫

γ T[θ]-1

T[θ] δ δ

PLLϕ ϕ

T[ϕ]-1

T[ϕ

]

T[γ] vrqd

ipqd

γ

ONSHORE STATION

GSC CONTROL

Pitch controller

βpitch PwtPwt

*

WF power controller E1

E1min

Pw

t-ch

DETAILED WIND TURBINE

WINF FARM CONTROL

P2ch

PWFred

Power reduction

d/dt

.

PLL

GSC-DBRCONTROL

COMMUNICATION BUS

ωδ

OFFSHORE PLATFORM

Pwt

EDC

PDC

E2

E1

E1

E2

E2

max

min

max

min

nomE2


26

PhD thesis, Agustí Egea (CITCEA-UPC)


WFC

E1

I1 GSC

E2

Cable 1

Inner loopilq*

Droop control

vlqd

E2*

ilqd

ilabc

vlabc vzabc

MPPT

Inner loop

iwtabc

T[θ]-1θg

θg

iwtabc

iwtqd

iwtqd

vwtabc

*

Inner loop

ipqd

vpqd

vpabc

*

ipabc

DC loop

Ewt

vpabc

vrabc

vrqd

Ewt*

ipqd

Ewt

T[γ]-1

vzabc

vlabc

vlqd vlabc

ilabc

E2

Inner loop

T[δ]-1

icqd*

Voltage loop

T[δ]

vcqd

icqd

vtabc

vtqdvcabc

icabc

icabcinabc

vcabc

inabc inqdvcqd*

vwtqd

vrabc

GSC chopper

E2

WTCWGC

∫

γ T[θ]-1

T[θ] δ δ

PLLϕ ϕ

T[ϕ]-1

T[ϕ

]

T[γ] vrqd

ipqd

γ

ONSHORE STATION

GSC CONTROL

Pitch controller

βpitch PwtPwt

*

WF power controller E1

E1min

Pw

t-ch

DETAILED WIND TURBINE

WINF FARM CONTROL

P2ch

PWFred

Power reduction

d/dt

.

PLL

GSC-DBRCONTROL

COMMUNICATION BUS

ωδ

OFFSHORE PLATFORM

Pwt




• Conclusions.


Conclusions • Offshore wind power plants connected with VSC-HVDC have

special characteristics: – The VSC-HVDC converter needs to create an offshore grid where the

frequency can be freely chosen.

– As the offshore grid is an only “power electronics” grid, the protections need to be carefully designed. Standard approaches may not be useful.

– The interactions between wind turbines and VSC-HVDC converters need to be studied.

• Offshore wind power plants need to: – Collect the wind power and inject it in the HVDC cable

– Provide support to the main AC grid and DC grid.

– Maintain stability in normal and fault conditions


Thanks for your attention!

[email protected]

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operation of offshore wind power plants connected with hvdc · 2015-02-11 · operation of offshore...

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