2015 12-02-optiwind-inertial response-u_gent

Emulated inertial response with windturbines

Jan Van de Vyver

Ghent UniversityFaculty of Engineering and Architecture (FEA)

Department of Electrical Energy, Systems and Automation (EESA)Electrical Energy Laboratory (EELAB)

ING

ENIEURS W E TENSCHAPPEN

A R C H IT E C T U U R

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Introduction

Who provides ancillary services?

Current situation:

Conventional generation→ majority of services

Future situation:

Renewable electricity generation⇒ conventional electricity generation

Problem:

Renewable = variable, decentralized⇓

More ancillary services needed:- additional power reserves

- frequency controlm

Less conventional generators to provide them:

- increased costs

- reduced life cycle

Solution:⇒ provide ancillary services with wind turbines

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Frequency control

Overview of frequency control

Electric power system

• Power production has to be adapted to consumption at any point in time• Rotational speed Ω of generators is proportional to grid frequency f• Grid frequency f can be used as a measure:

- production = consumption⇒ f = 50 Hz- production > consumption⇒ f - production < consumption⇒ f

• Grid frequency f is a global parameter

⇒ f can be used to balance production and consumption: primary frequency control

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Frequency control Inertial response

Inertial response in the conventional power system

Inertial responseNatural inertial response of directly coupled synchronous generators on disturbances:

Jf0dfdt

= Pelec − Pload

- f : release of kinetic energy of rotating inertia

- f : absorb kinetic energy in rotating inertia

⇒ stabilising effect

Importance of inertial response

Low system inertia J:• high ROCOF• low frequency nadir• less time for primary controller

to change power output ofgenerator

0 5 10 15 20 25 30 3549

49.2

49.4

49.6

49.8

50

J

Time t [s]

f[H

z]

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Frequency control Inertial response

Natural inertial response with wind turbines

Modern wind turbines are connected to the grid by means of power-electronic converter:• Doubly fed induction generator (DFIG)• Full scale converter (FSC)

⇒ rotational speed Ω of the turbine is decoupled from the grid frequency f⇒ little or no inertial reponse from variable speed wind turbines⇒ system inertia J decreases⇒ f varies more rapidly

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Frequency control Inertial response

Emulated inertial response with wind turbines

Solution: Emulation of inertial response with additional control loop in converter

Synthetic inertia:Mimicking of the inertial response of asynchronous generator:

Pin = −Kindfdt− Kdroop∆f

Temporary power surge:Power increase in case of a frequency dip

0 5 10 15 20 25 30 35 40 45 500.7

0.75

0.8

0.85

Time t [s]

Pref[pu]

∆POP

tOP

Pref,0

t

Pref

⇒ inertial behaviour of wind turbine ≈ directly coupled synchronous generator

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Frequency control Inertial response

Emulated inertial response with wind turbines

Differences with a conventional generator:

• Recovery period is needed to regain normal operation• Energy yield losses arise due to suboptimal operation during inertial response

Tuning of the control parameters is crucial:

• Depends on the system composition (gas turbines vs. steam-based turbines)• Can improve frequency response tremendously• But: also risk of poor frequency response if not properly tuned

Kin[MWsHz ]

Kdroop[M

WHz] +

-

no WT →-

0 1 2 3 4 5 6 70

0.5

1

1.5

2

2.5

fmin[Hz]

49.58

49.6

49.62

49.64

49.66

49.68

0 10 20 30 40 50 60 70 80 90 1000.72

0.75

0.78

0.81

Time t [s]Pwind[p.u.]

0 10 20 30 40 50 60 70 80 90 1000.8

0.82

0.84

0.86

Ω[p.u.]—Pwind

- - Ω

0 5 10 15 20 25 30 35 40 45 5049.5

49.6

49.7

49.8

49.9

50

Time t [s]

f[H

z]

—No WT- -WT without SI—WT with SI

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Conclusions and outlook

Conclusions and outlook

• Technically, wind turbines can provide ancillary services• Emulated inertial response and even enhanced frequency control (primary frequency control)

with wind turbines are possible

Outlook

• Development of control strategies with a limited impact on the lifetime of the wind turbines• Field tests are important to demonstrate the positive impact

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Questions

Questions?

Contact details:

Jan Van de VyverElectrical Energy Laboratory (EELAB), Department of Electrical Energy, Systems and Automation(EESA), Ghent UniversityTechnologiepark-Zwijnaarde 913, 9052 GentJan.VandeVyver@UGent.be

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