© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for gridintegration

Nicolaos A. Cutululis, DTU Wind Energy17 January 2019, DeepWind Conference, Trondheim

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

• Background• Diode Rectifier as offshore HVDC• Grid Forming Wind Turbines• Offshore AC Grid Start-up• Black Start by Offshore Wind Turbines

2

Acknowledgements:Ramón Blasco Jiménez & team, UPVLie Xu & team, UoSÖmer Göksu & Oscar Saborío-Romano, DTU

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Offshore wind development

3Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Offshore wind development

4

Source: IRENA, Offshore innovation widens renewable energy options, September 2018

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Offshore wind development

5

Main cost components of offshore wind farms:- turbines (including towers) - the foundations - the grid connection to shore

- AC or DC?

Power flow is in one direction onlyWhy not use a diode rectifier offshore?

Source figure: ABB, onlineSource: IRENA, Offshore innovation widens renewable energy options, September 2018

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

PROMOTioN projectProgress on Meshed HVDC Offshore Transmission Networks

6Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Objectives

7Trondheim 17.01.2019

Objective 1Define functional

requirements to OWFs

Objective 2Develop test cases & control algorithms

Objective 3Define & apply

compliance evaluation

Objective 4 Recommend grid

code requirements

HVDC linkVSC

onshore

DRUDiode Rectifier Unit

Grid Forming WPP

DC -

DC +

dqabc

-+

ω

dqabc

refPFdU

FqCUω

sdI

0U

dqabc

Cable

Active power control

Voltage controlFrequency

controlReactive power sharing controlCurrent control

PLL

++

+1s

+-

++

-

+-

+-

+

-+

0Q

FqU

FdCUω

sqI+

-

+-

+

+

+-

++

fk qk

0ω

ω

FqU+

θ

+

FdU

FqU

cdU

cqU+

UFUC Is dcI

dcrU

+

WT line-side converter

R L C

0ω

refω

wtP

wtQ

wtP wtQ

WdI

WqI

WdLIω

FdrefU

FqrefU

WdrefI

WqrefI

WqLIω

IW

UFIW

lilp

kk

s+

Uoff

pipp

kk

s+vi

vp

kks

+

vivp

kks

+

iiip

kks

+

iiip

kks

+

Time[s]

Voltage [%]

0%

100%

85%

3

130%

90%

110%

120%

1802 50.25

~~~~

~~

115%

60

...permanent operating area...

?

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Diode Rectifier Units as offshore HVDC

8

currentVSC

solution

WPP transformers

HVDC offshore terminal

VSC-MMC

HVDC link

VSC-MMConshore

HVDC link

VSC-MMConshore

Diode-Rectifier Units (DRUs)

new DRU solution

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Grid Forming Wind Turbines

9

GearBox

Generator

WT transformer

WPP transformer

WT transformer

ACDC AC

DC

HVDC transformer

VSC - HVDC Offshore HVDC

Onshore

Onshore AC Grid

WT Control

Offshore Voltage & Frequency

ACDC

ACDC

GearBox

Generator

ACDC

ACDC

WT Control

Active & Reactive Power

Active & Reactive Power

Grid following wind turbines

GearBox

Generator

WT transformer

WT transformer

ACDC AC

DC

Diode Rectifier Unit HVDC Onshore

Onshore AC Grid

WT Control

ACDC

ACDC

GearBox

Generator

ACDC

ACDC

WT Control

Active & Reactive PowerVoltage & Frequency Control

Grid forming wind turbines

Active & Reactive PowerVoltage & Frequency Control

Grid forming wind turbines control- dq current control based

- voltage/angle control based- VSM control

- GPS synchronization based- master/slave based

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Offshore AC Grid Start-up Options

10

VSC-MMC

VSC-MMConshore

HVDC link

VSC-MMConshore

DRUs

Onshore AC Grid

Umbilical AC Cable Nearby VSC-HVDC (or AC)

HVDC link

VSC-MMConshore

DRUs

Energy Storage

Local Energy Storage (e.g. battery, diesel)

HVDC link

VSC-MMConshore

DRUs

es

es

es

Black-startable wind turbines

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Some results – AC grid start-up (string connection)

11

www.promotion-offshore.net, Deliverable 3.4: Results on control strategies of WPPs connected to DR-HVDCTrondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

www.promotion-offshore.net, Deliverable 3.5: Performance of ancillary services pro-vision from WFs connected to DR-HVDC

Control challenges for grid integration

Some results – Frequency control

12Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Black-start - Progress Towards Demonstration

13

Outside PROMOTioNEnerginet performs Black Start field test with Skagerrak 4 (SK4) HVDC interconnector

WP3 Performs Black Start Simulation Test with Offshore WPPTo energize:• 3 buses • Overheadline & underground cable• Shunt reactor & transformer• Step MW++ load

• Load changes• Frequency & voltage setpoint changes• Load disconnection

Results to be compared against HVDC field tests by Energinet

SK4

[https://ens.dk/sites/ens.dk/files/Statistik/el_produktion_og_transmission_2017_300dpi.pdf]

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Scenarios – Self-Energization & Black Start

14

WPP1 400MW

BKT1

Off-shore Comp. Reactor

BKst1

BKst2

BKst3

BKst4

BKst6

66/220 kV

Off-shoreTransformer

BKT2

PcableQcable

75 km

On-shoreTransformer VSG

ZS

On-shoreNetwork

ISVS

ωS

Vo

220/400 kV

BKst5

BKT3

On-shore Comp. Reactor

BKT3

PT1QT1

VT1IT1

PT2QT2

VT2IT2

PT3QT3

VT3IT3

HVAC-connected OWPP

HVDC-connected OWPP(s) with AC collector substation(s)

HVDC-connected OWPP(s) directly (66kV) connected to the HVDC

Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Some results – black-start

15Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Some results – black-start

16Trondheim 17.01.2019

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Models for Control of WT/WPP Connected to DR- HVDCConfidential - only for members of the consortium

17Trondheim 17.01.2019

Aggregated single WT Ideal onshore DC voltage Ideal WT DC voltage

Offshore AC start-up Voltage & frequency control Active power setpoint control Offshore AC fault ride-through Intentional islanded operation

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Achievements

18Trondheim 17.01.2019

Control and Modelling Novel grid forming wind turbine controls Confidential grid forming WPP simulation models

Academic (white-box) & Industrial (black-box)

Operation of DRU HVDC Systems Functional requirements for Diode-Rectifier (DRU) connection of Wind Power Plants Control algorithms and simulation test cases & results Proof of DRU concept via simulations

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Control challenges for grid integration

Main Findings and Challenges

19Trondheim 17.01.2019

Operation of DRUs• Wind turbines can operate with DRU-connection without any

degradation compared to VSC• Wind turbines can operate as islanded (idling, self-sustaining)

Fault Handling in DRU-connected OWPP • DRU inherent response to DC link voltage

eases onshore AC fault ride-through

Ancillary Services by DRU-connected OWPP• DRU connected OWPP can contribute to

frequency support and oscillation damping

OWPP Self-energization and Black Start• OWPP can energize its AC network and might be able to

contribute to black start

Onshore AC Grid

© PROMOTioN – Progress on Meshed HVDC Offshore Transmission Networks This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 691714.

Any Questions?

20Trondheim 17.01.2019