Evaluation of Anti-Islanding Protection Schemes

8/13/2019 Evaluation of Anti-Islanding Protection Schemes

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EVALUATION OF ANTI-ISLANDINGPROTECTION SCHEMES

INDIAN CONTEXT

New Delhi / 21 April 2012

Renewable Energy World India

Kona Eswararao | Gamesa R&D Chennai


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Anti-Islanding Protection

2

EVALUATION OF ANTI - ISLANDING

SCHEMES

Distributed Generation

Islanding Anti-Islanding protection

Passive schemes and NDZ

PJD applied to weak grid

Simulation results

Conclusion


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Grid Connected RE SystemsChallenges and Issues

Islanding

Dynamic interaction between various generators

Conflict in voltage control for generators in

proximity

Power Quality

Weak Grid situations


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IslandingIntroduction

When loads are being fed power from DG even after the power supply issuspended from utility - Islanding Condition at PCC

Power

Converter

R L C

Grid

Utility breaker

DGDG jQP + gridgrid

jQP +

loadload jQP +

Local Load

PCC

loadDGgrid

loadDGgrid

QQQQ

PPPP

==

==

Wind Turbine

Generator

Formation of Islandwhen breaker is opened


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IslandingIssues

Danger to maintenance and restoration personnel

Destruction at both customer and utility side equipment

Power quality of DG becomes worsen - adversely affect the

loads

Automatic closing of utility breaker may create a condition of

asynchronous closure


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Anti-IslandingClassification


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Anti-IslandingPassive and Active Schemes

Passive techniques are based on measurement of instantaneous voltage,frequency and phase deviations at PCC

Simple and Easy to implement No introduction of noise or harmonic signal into network as like as Active

methods Power Quality not disturbed

The range of active power and reactive power change during islanding will

influence the detection time Passive techniques relay on certain distinct pattern or signatures at the DG

out put

Active techniques introduce deliberate changes or disturbances into the

connected circuit and then observe the response


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Anti-IslandingNDZ for CERC and C-WET requirements

Non Detection Zone (NDZ) is the range activepower and reactive power mismatch thatcauses non detection of Islanding

In this work NDZ is calculated for CERC andCWET based on voltage and frequencyvariation allowed

-27% to 14.34%-5.07% to 1.98%% change in Q

for Qf = 2.5

-17.6% to 9.35%-3.3% to 1.29 %% change in Qfor Qf = 1.63

-15.9 % to 21%-15.9 % to 21%% change in P

47.5 Hz49.5 Hzfmin

51.5 Hz50.2 Hzfmax

30 KV30 KVVmin

36 KV36 KVVmax

CWET at 33 KVCERC at 33 KVPARAMETER

-30 -20 -10 0 10 20 30-10

-8

-6

-4

-2

0

2

4

6

8

10

% Chnage in Active power

%C

hangein

Reactivepower

NDZ for CERC Tolerance at 33 KV

At Qf = 1.63

At Qf = 2.5

UVOV

OF

UF

-30 -20 -10 0 10 20 30-30

-20

-10

0

10

20

30

% Change in Acitve power

%C

ha

ngeinReactivepowr

NDZ for CWET Tolerance at 33 KV Grid

At Qf = 1.63

At Qf = 2.5

UF

OF

OV UV


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PJD ApplicationStiff Grid condition

MATLAB simulation model is developed toanalyse PJD method applied for stiff gridsituation

Islanding detection time for stiff grid is23.5 msec

0 0.05 0.1 0.15 0.2-2

-1.5

-1

-0.5

0

0.5

1

1.5

2Islanding detection at stiff grid

Phasejumpin

radians

Time in sec

Stiff grid

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.20

0.2

0.4

0.6

0.8

1

Islanding detection at stiff grid

DGCBsta

tus

Time in sec

X: 0.07355

Y: 1

Stiff Grid


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PJD ApplicationWeak Grid condition Voltage fluctuations

Same PJD method is applied to various weak grid situationsDetection time with high voltage fluctuations is 16 msec - Very QUICK

0.06 0.065 0.07 0.075 0.08

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

X: 0.06605

Y: 1

Islanding detection during high grid voltage

DGCBstatus

Time in sec

X: 0.07355

Y: 1

Stiff grid

Vhigh50

Vhigh20

Vhigh10


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PJD ApplicationWeak Grid condition Frequency fluctuations

Detection time same as stiff-grid, effect is negligible Because offrequency variation doesnt contribute to phase angale detection

0.07 0.071 0.072 0.073 0.074 0.075 0.076 0.077

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

X: 0.07355

Y: 1

Islanding detection during high grid frequency

DGCBstatus

Time in sec

Stiff Grid

fhigh10

fhigh20

fhigh50


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PJD ApplicationWeak Grid condition Higher THD presence

Same Islanding detection as compared to stiff grid due to grid alreadyhas harmonics / disturbance

Detection time with high harmonics in the system is just 14 msecFaster detection

0.06 0.062 0.064 0.066 0.068 0.07 0.072 0.074 0.076

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

X: 0.07355

Y: 1

Islanding detection during 5th harmonics in grid

DGCBstatus

Time in sec

X: 0.06425

Y: 1

ideal

THD 10%

THD 20%

THD 50%

0.06 0.065 0.07 0.075 0.08 0.0850

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

X: 0.0622

Y: 1

Islanding detection during 11th harmonics in grid

DGCBstatus

Time in sec

X: 0.07355

Y: 1

Stiff Grid

THD 10%

THD 20%

THD 50%


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Conclusions

Passive methods are simple, cost effective but higher values of NDZ

PJD gives early detection of Islanding when grid is weak

Introduction to DG Islanding phenomenon

Need for Islanding protection stringent Grid codes


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Thank you

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Evaluation of Anti-Islanding Protection Schemes

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