Large Offshore Wind Farm-ikni-greah

5/20/2018 Large Offshore Wind Farm-ikni-greah

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LARGE OFFS

EVALUATI

Djamel Ikni, PhD candida

Brayima Dakyo, member IElectrotechnic and Automatic Re

Laboratory of Le Havre (GRE

University of Le Havre

Le Havre, France

AbstractThis paper presents a comprehability of large offshore wind farmsrequirements of the grid code. In this study,farm configuration, i.e. AC configuration

analysis of wind farm AC control copresented. Furthermore, the developed cont

the converter used in the case for wind fhave been explained.

Index Terms -DC rid, Offshore Wind ParkDC /DC, Permanent magnet synchronous g

I. INTRODUCTIO

The integration rate of offshore win

more high; its marginality is reduced,

beginning to impact the network operati

various grid companies have developrequirements for offshore large wind fa

transmission network. Increasingly, thewind park increases and the distance fr

the point of common coupling follows t

situations generate losses, additional

capacity to transport this huge energy c

farm with traditional transmission syste

In these cases, HVDC transmission b

privileged solution [1], [2], [3], [4].

The main goal of the this paper is to

and effectiveness of DC/DC converte

realize a large DC configuration of high

farm. Then, the obtained results from laare compared to that of the convention

This work has been done under normal

on network). The wind farm power fact

to the fact that the physical behavior of h

the same for real size or reduced scale; t

this paper is done in reduced scale for an

MW.

ORE WIND FARM:

N OF NETWORK S

te

EEsearch

AH)

Ahmed O.Bagr

Energy and Energy

International Institut

Engineeri

Ouagado

ensive analysis of the

to meet the powerwe examined two windand DC one. A brief

figuration has beenol and the topology of

rm DC configuration

, HVDC, HVAC,

enerator (PMSG)

N

power is more and

and its presence is

ons. For this reason,

d specific technicalms connected to the

capacity of offshorem the wind farm to

e same trend. These

costs and limit the

ming from the large

s so-called HVAC.

comes adequately a

analyze the behavior

rs used in order to

power offshore wind

ge DC configurational AC configuration.

conditions (no fault

r is equal to 1. Due

igh power systems is

e study presented in

average power of 15

II. COMPARATIVEST

HVACTRANS

In the Fig.1, an idea can

limitations of each transmissipower transmission. It can

transmission technology is l

with a power of 200MW,

higher power VSC-HVDC;

[5]. Fig.2 shows the cost of e

distance and the wind farm

power [3], [1]. Fig.2 enable

greater than 80km; the DC

compared to the AC configur

to develop relevant topologi

control system to promote

large DC configuration of off

Fig.1: Choice of transmission syste

and conne

OTENTIAL

RVICES

, PhD candidate

Saving Laboratory (LESEE)

for Water and Environmental

ng -2iE Foundation

gou, Burkina Faso

UDYBETWEENHVDCAND

ISSIONSYSTEM

e made about the capacity and

on technology in terms of high- be observed that the HVAC

imited to a distance of 100km

eyond this distance and for a

technology is the best solution

nergy produced according to the

configuration for a same rated

s to conclude if the distance is

configuration seems interesting

ation. Both data have allowed us

es of the converters and their

VDC transmission system and

shore wind farm [2], [3].

according to the wind farm capacities

tion distances.


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Fig.2: Energy production cost according to the

III. AC WIND FARM CONFI

The offshore wind farm in AC config

power rated of 15 MW including thre

Permanent Magnet Synchronous Genegenerator presents a rated power 5MW

33kV. The wind farm is connected to th

230 kV through a power transformer

illustrated in Fig.3.

A. Control Strategy of the System

The wind farm controller is the "brai

farm. Its role is to control the total am

required and authorized to inject the win

grid. The overall objective of such a con

wind farm to behave as active ele

monitored in the power system. Fig.4 ill

of the wind farm control system [6].

The control level of the wind fa

centralized unit. It has as inputs, the

system operator, the measurements at t

coupling (PCC) and the power availabl

Depending on the state of the grid, the o

electrical operation of the wind farm, idifferent operation modes [6].

In the block dispatch control pres

active and the reactive power refere

turbine of the farm is calculated usi

distribution algorithm method [6],

synthesizes this method, where Pdemrespectively the active and the reactive

the grid manager, Pavail-i and Qavail-i are

and the reactive powers for iwind turbin

C/DC configurations.

URATION

ration studied with a

wind turbines with

ator (PMSG). Eachith an AC voltage of

e grid at a voltage of

(offshore station) as

n center" of the wind

unt of power that is

d farm energy to the

troller is to allow the

ent, which can be

ustrates the structure

rm behaves as one

requirements of the

e point of common

e in the wind farm.

erator requires some

.e. the wind farm in

nted in Fig. 5, the

ces for each wind

ng the proportional

[7]. Equation (1)

nd and Qdemand are

power demanded by

the available active

.

(1)

Fig.3: Offshore wind farm ba

Fig.4: Wind fa

Fig.5: Control strat

The active and the reactive p

are calculated in (2).

B. AC configuration Contr

An important element in

wind model. Many model

complexity have been devel

behavior of the wind. In ou

wind speed are different fo

Fig.6.

sed on an AC-AC configuration.

m control method.

gy of the wind turbine.

wers available in the wind farm

(2)

l Results

the study of wind farm is the

s with greater accuracy and

ped in order to obtain the real

r case, the used profiles of the

r each turbine as illustrated in


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Fig.6: Wind Speed profiles for the th

a)

b)

c)Fig.7: Contribution of the each wind turbine: a)

turbine, c) third turbine.

ree turbines.

first turbine, b) second

Fig.8: Global Activ

Fig.7 presents the contribu

shows the performances of th

power of the wind farms for

as the world balance contr

control) required by the grid

IV. DCWIND

The structure of the

configuration is given in Fig.

controllable AC/DC Conv

converter also controllable.

voltage for each converter are

Converter A: Co

(rectifier), P = 5MW

Converter B: Full br

= 5 kV, Vdc-D= 50 k

Converter C: Full b=50 kV, Vdc-HVDC=3

Converter D: DC/

MW, Vdc-HVDC= 300

The converters A, B and C

machine, the Vdc-Trvoltage, th

Vdc-D. Finally, the converter

voltage Vdc-HVDC, and the rea

grid.

Fig.9: Offshore wind farm

e Power for wind farm.

tion of the wind turbines which

control. Fig.8 shows the global

different operation modes (such

ol, delta control and absolute

anager.

ARM CONFIGURATION

offshore wind farm in DC

9. Each wind turbine includes a

rter (rectifier), and DC/DC

The rated power and the rated

presented in next paragraph:

ntrollable AC/DC Converter

, Vdc-Tr = 5 kV.

idge converter, P = 5MW, Vdc-Tr

.

idge converter, P=15MW, Vdc-D0 kV.

C Converter (inverter), P=15

kV, VPCC= 230 kV.

control respectively the PMSG

e offshore platform voltage

D at the grid side controls the

ctive power exchanged with the

based on a DC configuration.


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A. Generator-Side Converter Control

The generator is controlled in the Par

the control. The electric torque is contr

wind power extracted to its maximum.

Isd-ref for Isd is chosen to 0 in order to

because the torque became a linear funct

Isqcurrent. TheIsdandIsqcurrents contro

Fig.10, where Vdc-Tris obtained from the

B.DC bus voltage Control Strategy

Currently, the DC / DC converters

application are available. Many topol

Converter are presented in the literaturtopologies, the full bridge converter is

offshore wind energy applications. For t

studies the full bridge converter has been

The DC/DC converter is used to

voltage management. The converter contin Fig.11, which adopts a double loops

first control loop is based on the Vdc-Trwhich estimates the Idc-D1-reffor Idc-D1The same strategy is applied to the conve

The control signals (PWM1-PWM4

are obtained by comparing the Umod s

carrier wave form with a frequency of 1

between 0 and 1, [11]. The converterDi

Vdc-HVDC voltage and the reactive power

grid as illustrated in Fig.12, [12], [13].

The reference for the active power is

AC Configuration. Moreover, the reacti

by the DC/AC converter in grid side. Thpowers references are given in (3).

!

Fig.10:Control strategy of the AC/DC Con

k dqplan to simplify

olled to regulate the

he reference current

simplify the control

ion depending on the

strategy is shown in

onverter B, [8], [9].

or high-power wind

gies of the DC/DC

e, [2]. Among thesemore appropriate for

is reason [2], in our

used.

maintain the Vdc-Trrol strategy is shownontrol [2], [10]. The

oltage management,

urrent management.

rter C.

and PWM2-PWM3)

ignal to a triangular

0 kHz. Umodmust be

used to control

exchanged with the

same in the DC and

ve power is supplied

e active and reactive

(3)

verter and PMSG.

Fig.11: Full bridge c

Fig.12 : Control Strategy of

C.DC configuration Results

The Dynamic behavior o

the case of wind farm DC c

Fig.17.

Fig.13: DC bus voltage co

nverter control strategy.

DC/AC Converter in grid-side.

the different converters used in

nfiguration is shown Fig.13 to

ntrol result for the first turbine.


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Fig.14: Vdc-Dand Vdc-HVDCvoltages c

a)

b)

c)

Fig.15: Wind turbines contribution: a) first turbi

third turbine.

ntrol results.

ne, b) second turbine, c)

Fig.16: Global Acti

Fig.17: Contribution of the eachturbine, c)

e Power for wind farm.

a)

b)

c)

ind turbine: a) first turbine, b) secondthird turbine.


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Fig.13 presents the rectifier output voltage Vdc-Tr for the first

wind turbine, which is same to its reference value. The Vdc-Dvoltage and the Vdc-HVDCvoltage are illustrated in Fig.14. The

contribution of the each wind turbine is plotted in Fig.15.

These currents have the same wave form to theircorresponding power due to constant behavior of the DC-bus

voltage (Vdc-D).

Fig.16 shows, the total active power in connection

coupling point for different operating mode (balance, delta

and absolute controls). This power is always equal to its

reference, and the same for each wind turbine as presented in

Fig.17.

V. CONCLUSION

Two configurations of the offshore wind farm are studied

and analyzed in this paper. The first configuration is based on

AC/DC converters with the power transformer in order to

increase the voltage. The second configuration is focused onDC/DC converters in order to increase and control the voltage

level. The obtained results from DC configuration are

compared to that of the AC configuration. In the case of DC

configuration, the obtained results such as active power

control result and the voltage management agree the proposed

control strategy.

Finally, the DC configuration enables to transport a high

power for greater distance with same performances to that of

AC configuration for reduced power.

References

[1] [1]P. Bresesti, Wil L. Kling, Ralph L. Hendriks, and R. Vailati"HVDC

connection of offshore wind farms to the transmission system" IEEETransaction on energy conversion, vol.22, no.1, pp.37-43, March 2007.

[2] L. Max, "Design and control of a DC collection grid for a windfarm"Ph.D.dissertation .Dept of Energy and Environment, Univ.Goteborg, Sweden 2009.

[3] S.Lundberg "Conguration study of large wind parks" Ph.D. dissertation.Deptof Energy and Environment, Univ. Goteborg, Sweden 2003

[4] B. Van Eeckhout "The economic value of VSC HVDC compared toHVAC for offshore wind farms," Master Thesis, Univ KatholikLeuven. Belgique 2007 2008.

[5]

S. Meier "Novel voltage source converter based HVDC transmissionsystem for offshore wind farms,"Ph.D. dissertation. Dep. ElectricalEngineering Electrical Machines and Power Electronics, Royal Instituteof Technology Department Sweden2005.

[6] Cosmin E. Bnceanu, Iulian V" Coordinated control of wind turbine"Master Thesis, Dept. Energy Technology - Pontoppidanstrde 101Aalborg , Univ Aalborg , Denmark, 2011.

[7]

T.Ghennam,"Supervision dune ferme olienne pour son intgration

dans la gestion dun rseau lectrique, apports des convertisseurs multi

niveaux au rglage des oliennes base de machine asynchrone

double alimentation," PhD. dissertation, Laboratoire dElectrotechnique

et dElectronique de Puissance (L2EP), Lille, France, 2011[8]

V. Courtecuisse, Supervision dune centrale multisource base

doliennes et de stockage dnergie connecte au rseau

lectrique,Phd dissertation, Gnie Electrique, Ecole NationaleSuprieure des Arts et Mtiers, Lille, 2008 France

[9]

Ahmed M. Hemeida, Wael A. Farag, and Osama A. Mahgoub,Modeling and control of direct driven PMSG for ultra large windturbines, World Academy of Science, Engineering and Technology

No.59, pp.918-924, 2011

[10] Fujin Deng"Design and control of A DC grid for offshore wind farms"Ph.D. dissertation. The Faculty of Engineering, Science, and

Medicine, Univ. Aalborg, Denmark2012[11]

M. B. Camara, B.Dakyo, H Gualous, C. Nichita , "Full bridge converter

for embedded energy share between battery and supercapacitors," in

Industrial Electronics, 2009. IECON '09. 35th Annual Conference ofIEEE, 2009, pp.504-509.

[12]

K C.Sanjay "Control and protection of wind power plants with VSC-HVDC connection"Ph.D. dissertation. Dipof Energy Technology, Univ.Aalborg, Denmark 2011

[13] Guangchen Liu, Shengtie Wang, Hong Zhang, and Bo Wang,Integrated control strategy of multibrid wind power generation

system, 2012 IEEE 7th International Power Electronics and MotionControl Conference - ECCE Asia. June 2-5, 2012, Harbin, China

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Large Offshore Wind Farm-ikni-greah