Implications of the DC Voltage Control Strategy on the ... Presentation... · 45/15 45.00 15.00 DIgSILENT fglongatt PowerFactory 14.0.525 VSC Multi-Terminal HVDC System DC Voltage

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Francisco M. Gonzalez-Longatt, www.fglongatt.org.ve 1

Implications of the DC Voltage Control Strategy on the Dynamic Behavior of Multi-terminal HVDC following a Converter Outage

F. Gonzalez-Longatt1,2, J. Roldan3

M. Burgos-Payán3, V. Terzija4

1 Coventry University2 Venezuelan Wind Energy Association

3 Universidad de Sevilla4 The University of Manchester

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I. OutlineI. IntroductionII. Control Strategies for MTDC Networks Operation

(i) Inner-Fast Current Controller, (ii) DC Voltage Controller, (iii) AC Voltage Controller, (iv) Active Power Controller, (v) Reactive Power Controller.

III. DC Voltage Control: Methods(i) Direct Voltage-Droop Method (ii) Voltage-Margin Method

IV. Simulations and Results(i) Case I: Sudden load increase, (ii) Case II: One Converter Outage

V. Conclusions

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I. Introduction (1/2)• The EU and the G8 Heads of

Government committed their countries in 2009 to an 80 % reduction in Green House Gas emissions by 2050.

• International consensus to reach this target requires the EU to achieve a 'nearly zero-carbon power supply‘.

• Supergrid is the name of this future electricity system that will enable Europe to undertake a once-off transition to sustainability.

• Multi-terminal HVDC (MTDC) using Voltage Source Converter (VSC) is the most appropriate technology to enable the concept of Supergrid.

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I. Introduction (2/2)• The power injections (Pi) in a DC grid

are controlled by the converters. • On a MTDC grid as Supergrid, the

power flow into, or out of, each converter can be dynamically changed without any reconfiguration of the HVDC grid.

• Although Supergrid should allow the full control of active power on all converters, several control challenges arise from this condition.

• The purpose of this paper is to analyze the potential implications of the DC Voltage Control Strategy on the dynamic behavior of Multi-terminal HVDC following a Converter Outage.

Scot

land

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GW

)E

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nd S

hore

Lin

e(2

4GW

)

Nor

Ned

2

Nor

Ned

(7G

Q In

terf

ace

Cap

acity

)

Den

mar

k Sh

ore

Lin

e (3

.5G

W)

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II. Control Strategies for MTDC (1/3) Schematic representation of MTDC control system

hierarchy The master control optimizes the overall performance of the MTDC by regulating the DC side voltage. It is provided with the minimum set of functions necessary for coordinated operation of the terminals in the DC circuit, i.e. start and stop, minimization of losses, oscillation dampingand power flow reversal, black start, AC frequency and AC voltage support.

The terminal controllers determine the behavior of the converter at the system bus.

They are designed for the main functions for controlling: active power (P), reactive power (Q), AC and the DC voltage (Vac, Udc)

Time Scale

VSCdcn

iP ,dc iP

,dc iUiV

,g iP,l iP

1gP

1lP

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II. Control Strategies for MTDC (2/3)

Terminal Controllers are based on locals actions and measurements.Wide-area measurement and control can improve the system performance.

refQQ

acV,ac refV

*qi

*di

refPP

dcU,dc refU

,ac CtrlVCtrlQ

,dc CtrlUCtrlPTerminal Controller

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II. Control Strategies for MTDC (3/3)

refQQ

acV,ac refV

*qi

*di

refPP

dcU,dc refU

,ac CtrlVCtrlQ

,dc CtrlUCtrlP

refQ

Q,

,i Q

p Q

KK

s *

qi

maxi

maxi

,,

i Udcp Udc

KK

s *

di

maxi

maxi,dc refU

dcU acV

,ac refV ,,

i Vacp Vac

KK

s *

qi

maxi

maxi

refP

P,

,i P

p P

KK

s *

di

maxi

maxi

*dv

*qv

,d refi

,q refi

di

qi

dv

qv

,,

i idp id

KK

s

,,

i iqp iq

KK

s

LL

Q Controller P Controller

Udc ControllerVac Controller

Idq Controller

Terminal Controller

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III. DC VOLTAGE CONTROL

When the active power is to be transmitted from Terminal B to Terminal A (PA<0, PB>0), the voltage margin (Udc) is subtracted from the DC reference voltage for Terminal A.

(i) Voltage Margin Method (VMM) (ii) Voltage-Droop Method (VDM)

When Udc drops the slack converter station (VSCA) will increase the active power injection in the DC grid PA until a new equilibrium point.

,AdcU

AP

dcU

upperPlowerP

,AdcU

AP

Slope mcdcU

Initial operating pointInverter

Lower limitRectifier

“a”

Upper limit

upperPlowerP

,adc refU

“b”

brefP

brefU

arefP

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IV. Simulations and Results (1/2)• The dynamic behavior of AC/DC Test System is analyzed based

on time-domain simulations. DigSILENT PowerFactoryTM

v14.0.525.1.

• Case I: The effect of sudden load increases on power flows and transient response in the AC/DC Test System.

• Case II: The effects of a converter outage on the dynamic response are also analyzed.

AC Test System: of Stagg and El-Abiad. DC Test System: VSC MTDC system.

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IV. Simulations and Results (2/2)• An sequential solution algorithm is used for the AC/DC

power flow solution.

• That solution is used as initial conditions for the dynamic simluations.

fglongatt

PowerFactory 14.0.525

Stagg and El-Abiad Test System

DC Voltage Control on Multi-Terminal HVDC Juan Manuel Roldan

Francisco M. Gonzalez-Longatt, PhD

Project: fglongatt Graphic: AC Power Networ Date: 01/01/2012 Annex:

ElmSouth

NorthLake Main

Bus 598.940.99-4.20

Bus 499.200.99-4.31

Bus 399.501.00-3.94

Bus 2100.001.00-2.44

Bus 1106.001.060.00

20/10

20.0010.00

G~G2

40.00-106.69113.94

External Grid

135.98..85.82 ..0.85

2-5

25.62-0.8325.64

2-5

-25.36-1.3525.64

45

-0.36-1.263.70

45

0.36-3.653.70

2-4

-17.43-0.2617.88

2-4

17.62-3.1517.88

3-4

22.261.6622.64

3-4

-22.21-3.4822.64

2-3

13.90-3.6914.37

2-3

-13.780.0614.37

1-3

36.0814.8938.87

1-3

-34.93-16.7338.87

1-2

99.9070.93119.03

1-2

-97.14-69.02119.03

60/40

60.0010.00

40/5

40.005.00

45/15

45.0015.00

DIg

SILE

NT

fglongatt

PowerFactory 14.0.525

VSC Multi-Terminal HVDC System

DC Voltage Control Dynamic Case

Francisco M. Gonzalez-Longatt, PhD

Project: Graphic: DC Power Netwo Date: 01/01/2012 Annex:

RECTIFIER INVERTER

INVERTER

Multi-Terminal HVDC System

Bus 598.940.99-4.20

Bus 399.501.00-3.94

Bus 2100.001.00-2.44

Bus 8148.240.990.00

Bus 7149.701.000.00

Bus 6154.221.030.00

35.005.00

18.550.00

-60.0040.00

VSC 37

18.550.00

VSC 37

-19.620.00

VSC 58

35.005.00

VSC 58

-36.230.00

VSC 26

-60.0040.00

VSC 26

57.900.00

6-7

-28.940.0029.00

6-7

29.820.0029.00

6-8

28.090.0027.32

6-8

-27.000.0027.32

7-8

-9.240.004.67

7-8

9.330.004.67

DIg

SILE

NT

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Models on DSL

FRAME P-Q Controller: Active and Reactive Power Controller (P-Q Mode)

Frame: P-Q ModeDeveloped by: Juan M. Roldan

Francisco M. Gonzalez-Longatt, PhD01/01/2012

[email protected]

P controllerElmDsl*Pref

0

1

2Current Controller

ElmDsl*

0

1

2

3

0

1

PLL measureElmPhi*

0

1

2

P-Q measStaPqmea*

0

1

VSCElmVscmono*

0

1

2

3

0

1

Control fElmDsl*

fref 0

1

Q controllerElmDsl*Qref

0

1

FRAME P-Q Controller: Active and Reactive Power Controller (P-Q Mode)

iq(1)

iqref

idrefDPf

id(1)

Q

Fmeas

P

sinrefcosref

Pmq

Pmd

DIg

SILE

NT

FRAME Control Udc-Q: Controller Udc-Q

FRAME Udc-Q ModeDeveloped by: Juan M. Roldan

Francisco M. Gonzalez-Longatt, PhD01/01/2012

[email protected]

VSC-1ElmVscmono*

0

1

2

3

0

1Vdc ControlElmVdc*

Vdc_ref

0

1

2

3

Current C..ElmDsl*

0

1

2

3

0

1

Idc measStaImea*

Vdc measStaVmea*

P-Q measStaPqmea* Q control

ElmDsl*Qref

0

1

Vac measStaVmea*0

1

transformation phase ..ElmDsl* iq

0

1

2

3

0

1

PLLElmPhi*

0

1

FRAME Control Udc-Q: Controller Udc-Qud

iqid

idref

iqref

Pmq

PmdIdc

Vdc

Q

uiur

cosref

sinref

DIg

SILE

NT

idq controller: Current Controller, Internal-Fast Loop

Developed by: Juan M. Roldan and F. Gonzalez-Longatt, PhDProject: Multi-Terminal HVDC

Date: 01/01/[email protected]

-

Pmdq limiter

Max

0

1

0

1

-

Current Limit..

Max_I

0

1

0

1

{K (1+1/sT)}K,T

Max_Pm

Min_Pm

{K (1+1/sT)}K,T

Max_Pm

Min_Pm

idq controller: Current Controller, Internal-Fast Loop

0

1

2

3

0

1Pmq

Pmd

iql

idl

iqref

idref

uq

ud

diq

did

iq

id

DIg

SILE

NT

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DC Voltage Controllers: DSL ModelsUdc-P droop controller: Udc Droop Controller

Droop

Udc-P Droop Controller Developed by: Juan M. Roldan

Francisco M. Gonzalez-Longatt, PhDProject: Multi-Terminal HVDC

01/01/2012, [email protected]

- {K (1+1/sT)}Kp,Tp

Max_I

Min_IKKv

Limiter with input si..

-

Udc-P droop controller: Udc Droop Controller

2

1

4

3

0

5I_min

I_max

Idrefu

Pref

P dP

Plower

KDV

DV

Pmax

Udc

Udcref

DIg

SILE

NT

Udc Controller: Voltage-Margin Method (VMM)

Udc-P Voltage-Margin Method Developed by: Juan M. Roldan

Francisco M. Gonzalez-Longatt, PhDProject: Multi-Terminal HVDC

01/01/2012, [email protected]

Constant1/mc

{K (1+1/sT)}Ku,Tu

Max_I

Min_I

Limiter with input signals-

Udc Controller: Voltage-Margin Method (VMM)

2

1

0

5

3

4

I_max

I_min

o11u1

Ud

Idc

o1du

Pupper

Plower

IdrefU

Udc_ref

Udc

o12

DIg

SILE

NT

,

,i Udc

p Udc

KK

s di

maxi

maxi,dc refU

dcU1

cm

refP

P

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Case I: Sudden Load Increase (1/2)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.729

30

31

32

Time (s)

Pow

er 6

-7 (M

W)

MarginDroop ADroop B

0 0.1 0.2 0.3 0.4 0.5 0.6 0.727.5

28

28.5

29

Time (s)

Pow

er 6

-8 (M

W)


0 0.1 0.2 0.3 0.4 0.5 0.6 0.76

7

8

9

10

11

Time (s)

Pow

er 7

-8 (M

W)


RECTIFIER INVERTER

INVERTER


Bus 598.940.99-4.20

Bus 399.501.00-3.94

Bus 2100.001.00-2.44

Bus 8148.240.990.00

Bus 7149.701.000.00

Bus 6154.221.030.00

35.005.00

18.550.00

-60.0040.00

VSC 37

18.550.00

VSC 37

-19.620.00

VSC 58

35.005.00

VSC 58

-36.230.00

VSC 26

-60.0040.00

VSC 26

57.900.00

6-7

-28.940.0029.00

6-7

29.820.0029.00

6-8

28.090.0027.32

6-8

-27.000.0027.32

7-8

-9.240.004.67

7-8

9.330.004.67

Sudden Load Increase

Voltage margin method produces the smallest stress on AC system.

Voltage-Droop method increases power transfer during initial response.

40P MW

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Case I: Sudden Load Increase (2/2)• The blue line shows the bus voltage’s

response with only one voltage controller operating, voltage margin method.

• The red line represents the dynamic response when a voltage droop controller (mc = -0.1) is operating on converter station VSC26.

• The transient over-voltages and under-voltages are reduced as expected using the droop control.

• The slopes of the voltage-droop controller considered in this simulation are 1/mc= -10.0, -8.0, -2.0 p.u. for converters VSC26, VSC37, VSC58 respectively.

0 0.2 0.4 0.6 0.8 11

1.01

1.02

1.03

1.04

Time (s)

Bus V

olta

ge (p

.u)

0.1 0.15 0.2

1.01

1.02

1.03

MarginDrop

0 0.2 0.4 0.6 0.8 10.97

0.975

0.98

0.985

0.99

Time (s)

Bus V

olta

ge (p

.u)

0.05 0.1 0.15

0.97

0.975

0.98

0.985

0.99MarginDroop

Bus 5, AC voltage transient with margin and droop control strategies

Bus 6, DC voltage transient with margin and droop control strategies

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Case II: Converter Outage (1/2)

RECTIFIER INVERTER

INVERTER


Bus 598.940.99-4.20

Bus 399.501.00-3.94

Bus 2100.001.00-2.44

Bus 8148.240.990.00

Bus 7149.701.000.00

Bus 6154.221.030.00

35.005.00

18.550.00

-60.0040.00

VSC 37

18.550.00

VSC 37

-19.620.00

VSC 58

35.005.00

VSC 58

-36.230.00

VSC 26

-60.0040.00

VSC 26

57.900.00

6-7

-28.940.0029.00

6-7

29.820.0029.00

6-8

28.090.0027.32

6-8

-27.000.0027.32

7-8

-9.240.004.67

7-8

9.330.004.67

Outage

X36.23P MW

0 0.1 0.2 0.3 0.4 0.5 0.6 0.725

30

35

40

45

Time (s)

Pow

er 6

-7 (M

W)


0 0.1 0.2 0.3 0.4 0.5 0.6 0.7-20

-10

0

10

Time (s)

Pow

er 7

-8 (M

W)


0 0.1 0.2 0.3 0.4 0.5 0.6 0.710

15

20

25

30

Time (s)Po

wer

6-8

(MW

)


Reverse power FlowConverter outage can create reverse power flows, overload on undersea cables and converter stations is a real possibility.Voltage-Droop method performs better.

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Case II: Converter Outage (2/2)• This simulation results are used to

investigate the effect of a distributed voltage droop control on bus 2 (VSC26).

• The response of bus voltage at bus 6 considering a perturbation based on the outage of VSC58 demonstrates how an incorrect selection slope value may causes transient responses with greater over-voltages on the DC bus (Droop B, green line).

• If voltage-droop slope is correctly selected it can assist the main the voltage at slack bus 3 and the system can handling transients caused by one converter station outage

0 0.2 0.4 0.6 0.8 11

1.05

1.1

1.15

1.2

Time (s)

Bus V

olta

ge (p

.u)


0 0.2 0.4 0.6 0.8 10.97

0.975

0.98

0.985

0.99

0.995

1

Time (s)

Bus V

olta

ge (p

.u)

0.05 0.1 0.150.97

0.975

0.98

0.985

0.99

0.995MarginDroop ADrrop B

Bus 5, AC voltage transient with margin and droop control strategies

Bus 6, DC voltage transient with margin and droop control strategies

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Conclusions• This paper presents simulation results show the effect of

DC Voltage control strategy on the dynamic behavior of bust voltages at multi-terminal HVDC following a converter-station outage: (i) voltage margin method and (ii) voltage-droop method.

• When two converters on the MTDC operate with DC voltage droop characteristic, it appears a "collaborative scheme" for the DC voltage support, sharing the task of controlling the DC voltage.

• Simulation results demonstrate the voltage margin control is capable to survive a converter outage just if this converter is operating on constant power mode.

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Any questions?

Francisco M. Gonzalez-Longatt, PhD, SMIEE, MIETCoventry University, Coventry, UK

Website: www.fglongatt.org.veEmail: [email protected]

Documents

Implications of the DC Voltage Control Strategy on the ... Presentation... · 45/15 45.00 15.00 DIgSILENT fglongatt PowerFactory 14.0.525 VSC Multi-Terminal HVDC System DC Voltage