modular dynamic models of large offshore multi … · 2013. 10. 26. · wp1: technology 1 234 ......

17 March 2011 R. Teixeira Pinto Slide 1 of 18

MODULAR DYNAMIC MODELS OF LARGE OFFSHORE MULTI‐TERMINAL

DC (MTDC) NETWORKS

R. Teixeira Pinto, PhD. StudentTechnische Universiteit Delft


Contents• Introduction

• The NSTG Project

• The Role of Modularity

• Modelling of MTDC Networks

• Control of MTDC Networks

• Case Study

• Conclusion


Introduction• 20‐20‐20 & 1/3‐1/3‐1/3• By 2020‐30: 40‐60 GW (EWEA)• NSTG: 30 – 50 GW

• 51% growth in 2010

• Bigger and distant offshore wind farms HVDC


The NSTG ProjectWhat is the best way of collecting this power?

WP 7 : Cost benefit analysis

WP 6 : Grid integration

WP 5: Optimization of NSTG solutions

WP4: Testing

WP 3 : Multi- terminal operation and control

WP 2 : Techno - economic evaluation

WP 1 : Technology

1 2 3 4

• WP3 Modelling• WP4 Building

The NSTG is mainly a technical project


Modularity“Modularity is the practice of building complex system or processes

from smaller subsystems that can be designed independently yet

function together as a whole”. ‐ Prof. Carliss Y. Baldwin

Highly complex system: smaller sub‐modules;

Systems can easier evolve with time;

Reduced cost of development;

Several stakeholders involved;

Business performance driven;

Easiness of maintenance, repair and recycling;


ModularityThe Design Hierarchy is made of levels:• Top level: Global Design Rules

• Lower levels: Design parameters within modules

$/ch

ange


Wind Farm

Wind speed

PowerHVDCstationVac, f

Wind Farm

Wind speed

PowerHVDCstationVac, f

MTDC Network

Power

VDC

Power

VDC

AC GridHVDCstation Iconv

AC GridVac, f

HVDCstation Iconv

Power

VDC

Power

VDC

Vac, f

Offshore MTDC models: modular by nature; Allows for comparative tests of individual modules performance; Dynamic models: operation & control.

Modelling


ModellingDynamic Model of MTDC Network

convertersP stationsDCV

linesDCI

linesDCP

stationsDCW

stationsDCV

( ) ( ) ( )L

n n nL L DC

s s s

P I V

DCI Y V

MTDC Network Topology

122

n n nDC DC L

n nDC DC

n

W P P dt

V WC


networkV

RefconverterV

DCV

converterV

converterI

converterP

lineDCP

ModellingDynamic Model of VSC‐HVDC

• Phase Reactor• Current Controller• Converter Model• Outer Controllers Average PWM Multi‐level


Inner Current Controller

TX

1

3SE 1

3CV

1CI

V

;AC ACP Q

0 5 10 150

0.5

1

1.5

2

2.5

3

3.5Step Response

Ampl

itude

T

T

RL

P

T

KL

0.095 0.1 0.105 0.11 0.115

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

For (SV)PWM:

• VSC Frequency: 2 kHz αc ≤ 2.5 krad/s bandwidth• Step response: ln 9 / αc ~ 1 ms• Simulation time‐step: 50 – 100 μs (20 – 10 samples)

Control

5 10P sw s

CT

KL

Proportional Controller


DC Voltage Outer Controller

2 / 200 /C DC MAXkrad s rad s

0cW cW

/W IK K

Control

212DC DCW CV

DCI

DCZ

C

CAPI DCV

LineI

SinceFor a PI controller:

It is best to have the DC voltageouter controller operating on the square of the DC voltage.

Linear system

0

0WK 18W CK C

18W CK C

C2

C

18

18

P C T

W DC C

DC C

K L

K C C

AC DCP PDCW2

sCAC DCP P

DCW2sC

LineP

+‐


Case Study

P1P2

P3

P4

P...

PN-2

PN-1

1

1

N

i N MAXi

P P

10

N

ii

P

Offshore MTDC with 4 terminals; Radial parallel connected; Two wind‐farms stations; Two on‐shore stations;

In the case study the DC voltage control strategy applied is the same used for point to point VSC‐HVDC transmission systems

• 1 Controlling Active Power• 1 Controlling the DC Voltage


Power

Power

Power DC Voltage0.8 pu

0.8 pu 1 pu

0.6 pu*

Case Study

* Disregarding losses in the MTDC system

Lets assume that the MTDC system is in the following steady‐state operating point:

1 pu = 500 MW


Power

Power

Power DC Voltage0.8 pu

0.8 pu

1 pu

Case StudyThen, suddenly the VSC‐HVDC Station 1 becomes inoperative

power unbalance = 0.6 pu


1st station startsconsuming 1 pu

1st WF startsproducing 0.8 pu

2nd WF startsproducing 0.8 pu

1st station isfaulted 155 ms < 8 cycles

233 ms < 12 cycles

C = 150 uF

Case Study

1 pu = ± 200 kV


1st station startsconsuming 1 pu

1st WF startsproducing 0.8 pu

2nd WF startsproducing 0.8 pu

1st station isfaulted 55 ms < 3 cycles

86 ms < 5 cycles

C = 75 uF

Case Study

1 pu = ± 200 kV


Case Study• In the case study shown, the power unbalance due to the fault in the VSC‐HVDC station 1 was 0.6 pu. In a MTDC system the DC voltage can vary really fast depending on the power unbalance and on the VSC‐HVDC capacitor size.

Time to VDC = 1.3 pu in msPower

Unbalance C = 75 uF C = 150 uF

0.6 pu 55 1550.8 pu 35 951.0 pu 26 65

Time to VDC = 1.4 pu in msPower

Unbalance C = 75 uF C = 150 uF

0.6 pu 86 2330.8 pu 55 1451.0 pu 36 102


233 ms < 12 cycles• Offshore wind energy is growing and fast;

• The optimal way to harvest and share this power inNorthern Europe is through the NSTG;

• Given its size and complexity the NSTG needs to be develop in phases and be approached modularly;

• To evaluate the operation and performance of thedifferent elements inside the NSTG there is need fordetailed modular dynamic models;

• There is need for control strategies capable of reliablyoperating MTDC networks with a large number of nodes.

Conclusions


233 ms < 12 cycles

Conclusions

THANK YOU FOR YOUR ATTENTION.

modular dynamic models of large offshore multi … · 2013. 10. 26. · wp1: technology 1 234 ......

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