Voltage Control in Distribution Networks With Windpower

7/30/2019 Voltage Control in Distribution Networks With Windpower

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Voltage control in distribution

Olof Samuelsson

Div. of Industrial Electrical Engineering and Automation

Lund University

Lund University / LTH/ Measurement Technology and Industrial Electrical Engineering/ IEA


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Contents

1. Local and system level impact of windpower. s r u on ee er vo age pro e

3. Voltage control actuators

. o age con ro sensors5. Control scheme

. .

7. Conclusions



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Wind turbine generator technologies

Induction generator

Doubly-fed induction generator

Full-scale converter



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Local level impact of windpower

Risk of island operation at distribution level n - s an pro ec on

Power quality

armon cs, vo age ps New fault current situation

New power flow situation (Ingmar Leie)

Losses



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System level impact of windpower

Balancing

-

Load

Reduced inertia

-

o an rns e

50

49

49.5

f[Hz]


0 10 20 30 40 5048.5

time [s]


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Fault behavior of windpower

SG instability related to critical clearing angle n uc on genera or ns a y re a e o cr ca c ear ng spee

Notion of Rotor speed stability proposed

Calculation of fault currents from DFIG

Francesco Sulla

4

6

8

pu

)

Phase current for DFIG at three-phase short-circuit

0 0.05 0.1 0.15 0.2 0.250

2Ia


. . . ,

Power Systems, Vol. 20, No. 2, pp 1179-1180, 2005)


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Voltage: Generic network with tap changer

130/10 kV substation

with OLTC

16 nodes

Load: 5 MW

.

Length: 28 km



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Voltage profile along a feeder

Voltage limitsoa on y

Generation only

Load and generation



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Voltage-constrained windpower capacity

Worst cases with tap changer control ax mum genera on a m n mum oa

Minimum generation at maximum load



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Change in voltage magnitude along line

VIXIRV rlinerlineqlineplineline

At transmission level reactive power controls voltage

At distribution level Q normally required to be zero


Draw Q should be possible with power electronics


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Medium Voltage lines

Line type R[/km]

L

[mH/km]

C

[F/km]

X/R

Cable AXCEL 95mm2 0.320 0.35 0.21 0.34

Cable AXCEL 150mm2 0.206 0.32 0.24 0.49

OHL FeAl 99 0.336 1.085 0.0061 1.01

e . . . .

AXCEL 95mm2

8km FeAl 99mm2 8km



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Network losses



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How frequent is maximum generation?

Some curtailment of active power is reasonable



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Use all actuators in a coordinated way

On-load Tap Changer s eps . eac n en re ne wor

Reactive Power

But increases line currents and thus losses

= .

Active Power Curtailment

But reduces income to generator owner



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Voltage requirements

EN 50160 o age qua y a cus omer s e

+/- 10 % for 95 % of a week with 10 min RMS values



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New electricity meters can report voltage

Remote reading of energy once a month since July 2009 r an: , g ee

Rural: GPRS

ona ea ures

Voltage limit violation alarms

Control output



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Proposed control structure

130 kV line

20 kV line. ne

Control and communication

Distributed Generation



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Heuristic al orithm uses incremental controlDelay until

next stepStart

V limit

violation

?

no

no

Priority

scheduler

Done?

Priority

on

OLTC?

OLTCcontroller

yes yes

Done?Priority

on Q?

Q controlleryes yes

no

Done?Priority

P controller

no

yes yes

no


no


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Result indicators

Installed MW windpower e vere an cur a e w n power

Tap operations



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E.ON test case

Feeder Load

[MW]

Existing WT

[MW]

New WT

[MW]

1 5.8 0.7 0.0

2 0.0 9.0 0.0

3 5.1 0.0 0.0

4 1.7 0.9 6.0

5 4.0 0 0.0

. .

7 5.3 1.4 13.0

8 4.2 0.8 3.0

28.0 12.8 25.0



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E.ON test case

130/20 kV E.ON substation ee ers

3 substations 20/10 kV

~170 substations 20/0.4 kV

Windpower 13 MW installed and 25 MW to be added



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E.ON load and generation profiles

Total active power load (measured)

Total active power generation (measured values upscaled)



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E.ON test case voltages with only tap changer

Voltage at substation busbar with normal setpoint

Voltage at node with lowest voltage



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E.ON test case voltages with new control

Voltage at substation busbar

Voltage at node with lowest voltage



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E.ON test case resultsMWh MWh

6000

8000

10000

100

150

0

2000

Transferred ener

0

50

250

300

MWh

150

50

100

15050

Curtailed Energy Tap changer operations

Local OLTC, existing windpowerOLTC with EM, PF=1


Local OLTC, PF=1

Local OLTC, PF var

OLTC with EM, PF=0.89

OLTC with EM, PF var


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E.ON test case economic analysis

Costs for tap operations

a n enance cos s

Costs for network losses

pr ce a or oo

Costs for active power curtailment

Electricity certificates



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E.ON test case economic results30000

20000

25000

10000

15000

0

5000

Curtailment Losses Tap changer operations

Total

oca , = oca , var

Coordinated OLTC, PF = 1 Coordinated OLTC, PF = 0.89

Coordinated OLTC, var PF



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Conclusions

Increase of windpower capacity without reinforcement

. + . = . .

increase of windpower 75 % additional, 40 % total

conom ca ene s rom coor na e an var a e

Energy values critically depends on profiles

Use of electricity meters feasible

Voltage magnitude and some continuous control better


Voltage Control in Distribution Networks With Windpower

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