Intelligent Micro-grid Protection - Silicon Institute of...

Intelligent Micro-grid Protection

Dr S R Samantaray

School of Electrical Science

IIT Bhubaneswar

20/02/2015 NWET-2015, Silicon Institute of Technology,

Bhubaneswar 1

Key points

• Introduction to micro-grid

• Issues involved in micro-grid

• Challenges in micro-grid protection

• Proposed Intelligent Relays

• Conclusion


Bhubaneswar 2

What is a microgrid ?

NWET-2015, Silicon Institute of Technology, Bhubaneswar

Objective: •Facilitate penetration of Distributed Generators (DG) to the power distribution network at low or medium voltage •Provide high quality and reliable energy supply to critical loads

20/02/2015 3

Microgrid Architecture


•Microsource Controller: Uses local information to control the microsource and responds in milliseconds to events. •Energy Manager: Optimizes individual microsources to meet power supplier and customer needs by collecting system information and providing each microsource with its individual operating points (normally power and voltage set points); the time response of this function is measured in minutes. • Protection Coordinator: which rapidly isolates feeder faults within the Microgrid and communicates feeder status changes to the Energy Manager.

20/02/2015 4

Microgrid Components


•Distributed Generation (microsources) • Loads • Intermediate storage • Controller and protection elements • Point of common coupling

20/02/2015 5

IEEE Standards for Microgrid issues


IEEE 1547: Interconnection of Distributed Generation Guides and Test Protocols:

•1547.1 –Testing •P1547.2 –Guide for use of 1547 •1547.3 –Communication •P1547.4 –DR Islands •P1547.5 –Above10 MWs •P1547.6 –Meshed Networks

20/02/2015 6

Introduction to DG

•Power source connected directly to the primary or secondary distribution system.

•Power Production in Distribution Network

•Usually small scale

•Often but not necessarily renewable

•In the US and other western countriess, this is known as Distributed Energy Resources, Distributed Generation and Dispersed Generation. In British English Embedded Generation is more frequently used.


20/02/2015 7

Various Sources for DG

•Wind Power

•Combined heat and power plants (CHP)

•Hydro Power

•Photo Voltaic

•Fuel cells


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Energy Storage Converters

•Synchronous Generators

•Induction Generators

•Power Electronic Converters


20/02/2015 9

Issues Involved in microgrid

•Protection Issues

•Control of DG Units

•Coordination of DG unit Controllers


20/02/2015 10

Protection Issues:

•Islanding Detection

•Protection against Faulty situations


20/02/2015 11

Micro-grid Operation A micro-grid is a group of controllable interconnected loads and distributed generations (DGs) within a clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid.

Distributed generations(DGs) DG Types-Induction, Synchronous, Inverter based.

Common distribution topology Radial grid structure, Loop grid structure

Mode of Operation

Grid Connected and Islanded :

• Unintentional (Failure in the upstream MV grid)

• Intentional (Maintenance actions) 20/02/2015 NWET-2015, Silicon Institute of Technology,

Bhubaneswar 12

Existing Micro-grid Protection Techniques


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Micro-grid Protection Challenges


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Grid connected mode (radial topology)

Islanded mode (radial topology)

Fault Current contributed in Grid connected and islanded mode (Radial topology)


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DL1 DL2 DL3 DL4 DL50

2

4

6

8

Distribution line

Fault c

urr

ent

in p

u

Grid connected mode

Islanded mode8.08

1.06

8.41

1.83

4.64 4.67

2.01

3.12

2.211.69

Fault Current measured in Grid connected and islanded mode (Radial topology)


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Islanded mode (radial topology)

Islanded mode (loop topology)

Fault Current contributed in Radial and Loop topology (islanded mode)


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Fault Current measured in Radial and loop distribution network (islanded mode)

DL1 DL2 DL3 DL4 DL50.5

1

1.5

2

2.5

3

3.5

4

Distribution line

Fault c

urr

ent

in p

u

Radial topology

Mesh topology

1.06

1.31

1.83

3.16

2.01

2.88

1.89

2.56

2.21

1.69


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Islanded mode (all DGs are present)

Islanded mode (DG1 is out)

Fault Current contributed when some DGs are Out (islanded mode)


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DL1 DL2 DL3 DL4 DL50

0.5

1

1.5

2

2.5

3

Distribution line

Fault c

urr

ent

in p

u

All DGs are present

DG1 is out

1.832.01

0.92

1.69

1.181.031.06

0.92

0.17

2.21

Fault Current measured when DG1 is Out (islanded mode)


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Grid connected (radial)

Islanded (radial)

Islanded, DG1is out

(radial)

Islanded, DG1 is out, (mesh)

End1 End2 End1 End2 End1 End2 End1 End2 DL1 8.08 2.44 1.06 3.31 0.92 0.05 0.26 1.98 DL2 8.41 2.06 1.83 2.12 0.17 1.62 0.89 1.29 DL3 4.64 1.08 2.01 1.38 0.92 1.36 0.41 1.85 DL4 4.67 1.84 2.21 1.24 1.18 1.39 1.17 0.89 DL5 3.12 2.21 1.69 1.76 1.03 1.81 0.43 1.98

End1 R1, R4, R6, R9, R11 (DL1, DL2, DL3, DL4, DL5 resp) End2 R2,R5, R7, R10, R12(DL1, DL2, DL3, DL4, DL5 resp)

Fault Current measured at Different Distribution Lines


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1. Variations in fault currents • Different in grid connected and islanded mode

• Synchronous DG and DFIG contribute more fault current compare to inverter based DG

• Depends on short circuit level(presence and absence of DGs)

2. Impact of DGs on relay operation • Bidirectional power flow affect the relay operation (coordination)

3. Impact of network topology on relay operation • Thus over current relay(and directional relay) with fixed setting may

be ineffective when applied to microgrid. It does not guarantee fault sensitivity or selective operation for all possible faults.

4. Anti-islanding information

Micro-grid Protection Challenges


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Motivation

• To overcome the following shortcoming in existing fault protection techniques. • Unreliable Over Current relay--- the fault current magnitude

vary over a wide range depending on the DGs present in the system and operating mode.

• The existing current differential protection work inefficiently as the current magnitude vary.

• Protection function must be selective depending upon the operating mode (grid connected or islanded mode)--- fault protection function must have prior islanding information.


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• To provide anti-islanding protection with minimum NDZ. • Existing passive anti-islanding relays such as rate of change

of frequency (ROCOF) relay and rate of change of voltage (ROCOV) relay fails in lower end power mismatch (< 15%) i.e, higher non detection zone (NDZ). The proposed relay is aim to reduce NDZ.

• To develop a data-mining based intelligent anti-islanding

protection relay, which can work for mixed DGs including synchronous and inverter based DGs.

• To design a comprehensive protection scheme for safe and

secure micro-grid operation.


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Proposed Protection Function for Micro-grid


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Data Mining Based Anti-Islanding Relay


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Islanding

That part of a power system consisting of one ore more power sources and load that is, for some period of time, separated from the rest of the system.”


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Effect of Islanding

•Islanding during a heavy load flow to or from the main grid necessarily causes an unbalance in production and load.

•If there is a surplus of active power in the island energy is stored in the rotating masses. The speed of the generators will increase and the frequency rises.

•In a PEC-unit the extra energy is stored in the DC-link, which leads to an increase of the DC-link voltage. Lack of active power in the island would obviously lead to the opposite.


20/02/2015 28

DG status during Islanding:

•Failure to trip islanded DG can lead to a number of problems for these resources and the connected loads, which includes power quality, safety and operation problems. •Therefore, the current industry practice is to disconnect all distributed resources (DRs) immediately after the occurrence of islands. •The disconnection is normally performed by a special protection scheme called islanding detection relays, which can be implemented using different techniques.


20/02/2015 29

Islanding Detection

Islanding detection is to detect the Loss of mains source connected to the grid ”. Antislanding protection and islanding protection are synonyms used around the world.


20/02/2015 30

Islanding Methods

•Passive method Make decisions based on the local measurements of voltage and current signals, under/over frequency, under/over voltage, rate-of-change of frequency, rate-of-change of power, vector surge and harmonic distortion indices •Active method In this technique, disturbances are injected locally into the system and responses of these disturbances are used to detect islanding conditions. Active schemes include impedance measurement, voltage phase jump, voltage shift, phase shift, frequency shift and harmonic distortion •Communications method Communication schemes are telecommunication devices that are designed to trip DR’s when islands are formed. These schemes include power line signaling and transfer trip


20/02/2015 31

•Active techniques introduce an external perturbation at the output of the inverter. These tend to have a faster response and a smaller non-detection zone compared to passive approaches. However, the power quality (PQ) of the inverter can be degraded by the perturbation.

•Reliability becomes a measure concern in Communication based Islanding detection using power line signaling and transfer trip

Difficulties in Active and Communication based Techniques


20/02/2015 32

Passive Islanding Detection Techniques

•Rate of Change of Power (ROCOF) •Rate of change of voltage •Rate of change in power factor •THD Voltage and Current •Vector Surge •Rate of Change of Power

The advantage of Passive techniques is that the implementation does not have an impact on the normal operation of the DG system


20/02/2015 33


20/02/2015

Most Effective Passive islanding detection technique

•P-f Droop •Active Power Mismatch and Frequency drift

•Q-V Droop

•Reactive Power Mismatch and Voltage drift

34

ROCOF for islanding conditions with active power imbalance from 5 to 80%.


Performance of ROCOF relays

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dv/dt for islanding conditions with reactive power imbalance from 5 to 80%.


Performance of dv/dt relays

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Limitations of Existing Passive methods

•The ROCOF relays, however, may become ineffective if the power imbalance in the islanded system is less than 15%, resulting in a high risk of false detection

• Vector surge relay is highly sensitive to load changes

•THD method suffers due to improper measurement at the PCC


20/02/2015 37

Motivation

The anti-islanding relay must work with

reduced Non-Detection-Zone. This is the

condition when the islanding occurs with

lower active and reactive power

mismatch.


20/02/2015 38

Proposed Data Mining Based Anti-Islanding Relay

Schematic diagram of the proposed data mining based anti-islanding relay

Training of DT

Testing for trip decision


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Key points of Proposed Data Mining Based Anti-Islanding Relay

•Passive anti-islanding relay.

•Uses multiple parameters for relay design.

•Developed data-mining based (decision tree(DT) intelligent

relay.

•Types of DG units (Synchronous and Inverter based).

•Power mismatch (0-100%).


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Studied Micro-grid


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Parameters of Studied Micro-grid

Line(Bus-Bus) R1(Ω) L1(mH)

1 DL1 4.856 34.525

2 DL2,DL7 1.238 11.18

3 DL3,DL8 0.7706 2.754

4 DL4,DL9 3.2552 9.081

5 DL5,DL10 1.701 15.36

6 DL6,DL11 0.1803 1.628

Line parameters

Load P(MW) Q(MVAR)

1 L1 1.50 0.70 2 L2 1.20 0.85 3 L3,L8 1.00 0.45 4 L4,L9 1.60 0.60 5 L5,L10 1.35 0.75 6 L6,L11 1.80 1.3 7 L7,L12 2.00 1.1

Load parameters


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Synchronous DG Parameter Value Parameter Value

MVA 9 Xd (pu) 1.56 Voltage(kV) 2.4 Xd' (pu) 0.296

H(s) 1.07 Xd'' (pu) 0.177

Td' (s) 3.7 Xq (pu) 1.06

Td'' (s) 0.05 Xq'' (pu) 0.177

Tqo'' (s) 0.05 Xl (pu) 0.052

F (pu) 0 Rs (pu) 0.0036

Brushless Exciter unit

Synchronous machine 8.1 kVA, 400 V, 3-phase, 50Hz, 1500 RPM

Transformer 400V / 12 V (3-phase)

Rectifier Diode Rectifier Bridge

Inverter based DG (Type-4 detailed model in MATLAB/SIMULINK)

Synchronous Generator

6 MVA, 575 voltage

Rectifier DC-DC IGBT-based PWM boost converter

Inverter DC-AC IGBT-based PWM converter

DG parameters

Parameters of Studied Micro-grid


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Features Extracted X1= ∆F, the frequency deviation (Hz).

X2= dF/dt, the rate-of-change of frequency ROCOF (Hz/s)

X3= V, the voltage in (pu).

X4= ∆V, the voltage deviation in (pu).

X5= dV/dt, the rate-of-change of voltage (pu/s).

X6= P, the DG active power output, pu (10MVA basis).

X7= dP/dt, the DG active power output change with time (pu/s).

X8= Q, the DG reactive power output (pu on 10 MVA basis).

X9= dQ/dt, the DG reactive power output change with time (pu/s).

X10= ∆Phi, change in the phase angle difference .

X11= dPhi / dt, the rate of change of phase angle difference .

X12= cos (phi), the power factor.

X13= d(cos (phi))/dt, the rate of change of power factor.

X14= CTHD , the total harmonic distortion of the current.

X15= dCTHD/dt, the rate of change of the total harmonic distortion of the current (pu/s).


Bhubaneswar 44

Features Extracted X16= VTHD , the total harmonic distortion of the voltage (pu).

X17= dVTHD/dt, the rate of change of the total harmonic distortion of the voltage (pu/s).

X18= VNEG , the negative sequence voltage.

X19= dVNEG/dt , the rate of change negative sequence Voltage.

X20= INEG , the negative sequence current.

X21= dINEG/dt, the rate of change negative sequence current.

X22= PNEG , the negative sequence power, pu. (10MVA basis)

X23= dPNEG/dt, the rate of change negative sequence power (pu/s).

X24= (U.cos Phi), the absolute value of the phase voltage times power factor (pu)

X25= d(U.cos Phi)/dt , the gradient of the voltage times power factor (pu/s).

X26= dF/dP, the rate-of-change of frequency over active power (Hz/pu).

X27= dV/dQ , the rate-of-change of voltage over reactive Power.


Bhubaneswar 45

The power system signal x(t) is represented as:

)2sin()(1

k

k

k kftAtx

Now, the three phase quantities (a, b, c) can be transformed in to d and q by d-q transformation as

where Ak , δk are amplitude and angle of kth order waveform and f is the power system real frequency

where ω0 =2ᴫ f0 and f0 is the power system nominal frequency

Now substituting the values of (1) in (2), at the mth order sample time , that is t=mTs (m=0,1,2…), where Ts is the sampling interval, results

1

0

1

0

])(2sin[

])(2cos[

2

3

)(

)(

k

ksk

k

ksk

q

d

mTfkfA

mTfkfA

mx

mx

c

b

a

q

d

x

x

x

tt

tt

x

x

2/32/30

2/12/11

)cos()sin(

)sin()cos(

00

00

(1)

(2)

(3)

DFT Based Pre-processor


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For k=1, the fundamental quantities are given as

])(2sin[5.1)(

])(2cos[5.1)(

1011

1011

sq

sd

mTffAmx

mTffAmx

From the above d-q quantities, the amplitude (A1 ) ,phase (δ1 ) and frequency (f) are calculated as

12

12

13

2qd xxA

)]0(/)0(arctan[ 111 dq xx

011

2

)]()([f

pT

pmmf

s

DFT Based Pre-processor

. abc to dq transformation in simulink environment

Magnitude and phase estimation using dq-transformation

(4)

(5)

(6)

(7)

(8)

1

dqo

2/3

Gain4

2/3

Gain3

sqrt(3)/2

Gain2

2/3

Gain11/2

Gain

Demux1

abc

3

Magnitude

2

Phase1

Vpabc dqo

clarke V

1

SI(z)

Vq

1

CO(z)

Vd

1

SI(z)

Uq

1

CO(z)

Ud

Re

ImDemux

|u|

u

1

Vabc


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Features Extraction

28

PandQ

27

dV/dQ

26

dF/dP

25

dUCPhi/dt

24

UCPhi

23

dPneg/dt

22

Pneg

21

dIneg/dt

20

Ineg

19

dVneg/dt

18

Vneg

17

dVTHD/dt

16

VTHD

15

dCTHD/dt

14

CTHD

13

dCPhi/dt

12

CPhi

11

dPhi/dt

10

∆ Phi

9

dQ/dt

8

Q

7

dP/dt

6

P

5

dV/dt

4

∆V

3

V

2

dF/dt

1

∆F 0

Xq

sqrt(eps+1e-6)

sqrt(eps+1e-6)

Signals Samples

Sampling V

Signals Samples

Sampling I

Rate Transition4

Rate Transition3

Rate Transition2

Rate Transition1

Vp

Ip

xq

F

V

∆V

∆F

Frequency Block

Vabc

Iabc

Vp

Ip

P

Q

CPhi

UCPhi

DFT Phasor

Iabc Ineg

Phase

Vabc Vneg

Phase

Iabc CTHD

Vabc VTHD

Pneg dPneg/dt

Ineg dIneg/dt

Vneg dVneg/dt

VTHD dVTHD/dt

CTHD dCTHD/dt

UCPhi dUCPhi/dt

CPhi dCPhi/dt

Phi

dPhi/dt

Q dQ/dt

P dP/dt

V dV/dt

F dF/dt

2

Iabc

1

Vabc

Phi

∆Phi

Phi


Bhubaneswar 48

Number of events generated

Number of Events Synchronous DG(1&3) Inverter based DG(2&4) Total Islanding 164 170 334

Non-Islanding 106 100 206 Total 270 270 540

Events Generation and Data Mining

Event DG1 DG2 DG3 DG4

1 CB1 Open islanding islanding Islanding islanding

2 CB3 Open islanding Non-islanding Non-islanding Non-islanding

3 CB6 Open Non-islanding Non-islanding Non-islanding islanding

4 CB4 Open Non-islanding islanding Non-islanding Non-islanding

5 CB5 Open Non-islanding Non-islanding islanding Non-islanding

6 CB2 Open islanding islanding islanding islanding

7 Sudden load change at PCC Non-islanding (DG1,DG2,DG3,DG4)

8 Capacitor switching Non-islanding (DG1,DG2,DG3,DG4)

Some Sample Events

*All above events are considered under wide variations in active and reactive power mismatch varying between 0 - 100 %.


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Events Generation and Data Mining

X1 X2 X3 X4 …. X25 X26 X27 Islanding=1,

non-islanding=0

0.02533014 0.00234216 1.02227909 0.00014694 …. 0.515873381 1.26267490 -0.00037 0

0.10104956 0.05020749 0.95246404 -0.03721791 …. -8.557069228 22.2106734 0.069447 1

0.24799979 0.12597821 0.96058803 -0.03237012 …. -27.16629357 -40.8684307 0.061323 1

-0.41279718 -0.20661342 0.99328937 -0.01792311 …. 290.4294997 2.36709369 0.028622 0

3.26806952 1.42538553 0.65418183 -0.22476201 … -20.10257667 -5.14555498 0.367729 1

Sample data set for training data mining model


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Building the Data Mining Model (Decision Tree)


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Decision Tree

• A flow-chart-like tree structure

• Internal node denotes a test on an attribute

• Branch represents an outcome of the test

• Leaf nodes represent class labels or class distribution


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Advantages of Data Mining Model (Decision Tree)

• It promote decision making

• It can handle high dimension data

• It does not required any domain knowledge or parameter setting, and is therefore suitable for exploratory knowledge discovery

• Learning and classification steps are simple and fast

• Good accuracy

• It perform well despite noisy or missing data (robustness).

• It convert result to a set of easily interpretable rules

• Simple to understand and implement.


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Decision Tree Learning Steps

Building a Decision Tree

1. First test all attributes and select the one that would function as the best root;

2. Break-up the training set into subsets based on the branches of the root node;

3. Test the remaining attributes to see which ones fit best underneath the branches of the root node;

4. Continue this process for all other branches until

a. all examples of a subset are of one type

b. there are no examples left (return majority classification of the parent)

c. there are no more attributes left (default value should be majority classification)


Bhubaneswar 54

Decision Tree Learning Steps

Determining the best attribute (Entropy & Gain)

• Entropy E(S)

E(S) = ci=1 –pi log2 pi ,

– Where S is a set of training examples,

– c is the number of classes, and

– pi is the proportion of the training set that is of class i

For our entropy equation 0 log2 0 = 0

• The information gain G(S,A)

G(S,A) E(S) - v in Values(A) (|Sv| / |S|) * E(Sv)

where A is an attribute


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DT Generated

Total 540 cases are considered. 70% data is used for training the DT and 30% for testing. 27 features are considered. Features taking part in DT construction are X4, X15, X1, X10, X27, X19, X6 (∆V, dCTHD/dt, ∆F, ∆Phi, dV/dQ , dVNEG/dt , P )

X15>=-0.081 X1>=-0.39

No

No

Yes

Yes

No

Yes

Yes

Yes

No

No

Yes

No

Yes

No

NoYes

Yes No

Yes N

o

Yes

No N

o

Yes

NoYes

No

Yes

X4<0.052

X1>=-0.93

X19<0.01

X1>=-0.8

X1<0.59

X27<1.8

X10<0.36 X1<0.19

X27<4.4

X10<0.27

X15>=-0.48 X6<0.39

IslandingNon-IslandingIslandingNon-Islanding Non-Islanding Non-Islanding

Islanding

Islanding

Islanding

Islanding Islanding

Islanding

Islanding

Islanding

Islanding


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Performance Indices

Dependability: Total number of islanding cases predicted / Total number of actual islanding events. Security: Total number of non-islanding cases predicted / Total number of actual non-islanding cases. Accuracy: Total number of correctly predicted (islanding + non-islanding) cases/ Total numbers of actual (islanding + non-islanding) cases.


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Performance comparison between proposed anti-islanding relays and ROCOF (with threshold of 0.1 Hz/s, 0.25 Hz/s) relay during active power mismatch for Synchronous DG.

Dependability Comparisons between Proposed and Conventional Relays

Performance comparison between proposed anti-islanding relays and ROCOV (with threshold of 0.1pu/s, 0.07 pu/s) relay for reactive power mismatch for Synchronous DG.

0 10 20 30 40 50 60 70 80 90 100 110

0

20

40

60

80

100

120

140

Active power mismatch%

De

pe

nd

ab

ility

%

DT based relay

ROCOF (Synchronous DG, Th=0.25 Hz/s)

ROCOF (Synchronous DG, Th=0.1 Hz/s)

0 10 20 30 40 50 60 70 80 90 100 110

0

20

40

60

80

100

120

140

Reactive power mismatch (%)

De

pe

nd

ab

ility

(%

)

DT based relay

ROCOV (Synchronous DG, Th=0.1 pu/s)

ROCOV (Synchronous DG, Th=0.07 pu/s)


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Dependability Comparisons between Proposed and Conventional Relays

Performance comparison between proposed relay and ROCOF (with threshold of 0.1 Hz/s, 0.25 Hz/s) relay during active power mismatch for Inverter based DG.

Performance comparison between proposed relay and ROCOV (with threshold of 0.1 pu/s, 0.07 pu/s) relay during active power mismatch for Inverter based DG.

0 10 20 30 40 50 60 70 80 90 100 110

0

50

100

150

Active power mismatch (%)

De

pe

nd

ab

ility

(%

)

DT based relay

ROCOF (Inverter based DG, Th=0.1 Hz/s)

ROCOF (Inverter based DG, Th=0.25 Hz/s)

0 10 20 30 40 50 60 70 80 90 100 110

0

20

40

60

80

100

120

140

Rective power mismatch (%)

De

pe

nd

ab

ility

(%

)

DT based relay

ROCOV (Inverter based DG, Th= 0.07 pu/s)

ROCOV (Inverter based DG, Th= 0.1 pu/s)


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Relays (Synchronous DG)

Dependability (%)

Security (%)

Accuracy (%)

DT 100 100 100 ROCOF(0.1 Hz/s) 35.90 100 67.95

ROCOF(0.25 Hz/s) 0 100 50 ROCOF(0.5 Hz/s) 0 100 50

Performance comparison between the proposed anti-islanding relays and conventional relay for 0-30 % active power mismatch

Results and Discussions

Relays (Inverter based DG)

Dependability (%)

Security (%)

Accuracy (%)

DT 100 98.34 99.18 ROCOF(0.1 Hz/s) 43.59 100 71.80

ROCOF(0.25 Hz/s) 0 100 50 ROCOF(0.5 Hz/s) 0 100 50

(Inverter based DG)

(Synchronous DG)


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Relays (Synchronous DG)

Dependability (%) Security (%) Accuracy (%)

DT 100 98 99 ROCOV(0.1 V/s) 0 100 50

ROCOV(0.07 V/s) 62.50 100 81.25

Results and Discussions

Relays (Inverter based DG)

Dependability (%)

Security (%)

Accuracy (%)

DT 100 99 99.50 ROCOV(0.1 V/s) 0 100 50

ROCOV(0.07 V/s) 47.86 100 73.93

Performance comparison between the proposed anti-islanding relays and conventional relay for 0-30 % Reactive power mismatch

(Synchronous DG)

(Inverter based DG)


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IEC Microgrid with DG interface

Validation on IEC micro-grd

TR -1

CB-1

L-2

L-4

L-6

L-5

B-1

CB-2 CB-3

CB-4 CB-5

CB-6

UTILITY

TR -5

TR -2

Synchronous DG

TR -4

Inverter based DG

B-2 B-3

B-4 B-5

B-6

DL -1

DL -4

DL -2

DL -3

DL -5

L-3

DG-4

DG-2DG-1

DG-3

TR -3

Inverter based DG

Synchronous DG

L-1

CB-7

CB-8

CB-10

CB-9


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Parameters of the IEC Microgrid model

Proposed Scheme Validation

Transformer Voltage Capacity TR1 120kV-25kV 20 MVA

TR2, TR3 2.4kV-25kV 5 MVA TR4, TR5 575V-25kV 4 MVA

DG1, DG2 (Synchronous DG) 2.4 kV 4 MW DG3, DG4 (Inverter based DG) 575V 3 MW Load L1 L2 L3 L4 L5 L6

P(MW) 1.5 1.5 1.0 1.5 0.5 1.0 Q(MVAR) 0.6 0.3 0.2 0.6 0.1 0.3

Distribution Lines Line Paramètres DL1, DL2,DL3,DL4

DL5 R0 = 0.1153 ohms/km, R1 = 0.413 ohms/km, L0 = 1.05e-3 H/km, L1 = 3.32e-3 H/km, C0 = 11.33e-009 F/km, C1 = 5.01e-009 F/km, 20 km each.

DT Dependability (%) Security (%) Accuracy (%) Relay (Synchronous DG) 98.07 97.14 97.54

Relay (Inverter based DG) 100 97.2 98.3

Performance Test Results of the proposed anti-islanding relays in IEC microgrid


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Conclusions

•It results a generalized relaying scheme for both synchronous and

inverter based DGs.

•Proposed data-mining based relays has dependability close to 100

%, and speed accuracy of 1 and ½ cycles.

•The proposed relay has negligible NDZ as its % dependability is

almost 100 in low active and reactive power mismatch (below 30

%), where exiting ROCOV and ROCOF fails.

•Robustness of the proposed technique for anti-islanding

protection is validated with standard IEC 61850-7-420 microgrid

•As DT is transparent and it can be implemented based on the set

thresholds of the decision variables. 20/02/2015


64

Data-mining based intelligent Differential Fault Protection Relay


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Proposed Protection Scheme for Micro-grid

Key points of the proposed work •It uses multiple parameter •It uses differential protection •The relay work properly in grid connected as well as islanded mode. •The relay work properly in all possible network topology (radial and loop topology). 20/02/2015


66

System Studied

DG1 & DG2(Synchronous)

DG3 (DFIG)

DG4 (Inverter based)

MVA 9 MVA 9 MVA 6 MVA

Load L1 L2 L3 L4 L5 L6

P(MW) 4.8 5.0 3.5 4.8 4.5 4.4

Q(MVAR) 2.6 2 1.5 3 2.7 2.5

IEC Microgrid with DG interface.

System parameters


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Features Extraction

7 differential features are derived as follows:

Xi= Xi,S - Xi,T

Where Xi is the differential feature, Xi,S is the ith feature estimated at bus S,

Xi,T is the ith feature estimated at bus T and S,T are the buses at end of the

target feeder.

X1= ∆( df/dt), the differential rate-of-change of frequency (Hz/s).

X2= ∆(dV/dt), the differential rate-of-change of voltage (pu/s).

X3=∆(dPhi/dt), the differential rate of change of power angle difference.

X4=∆(dP/dt), the differential active power output change with time (pu/s).

X5= ∆(dQ/dt), the differential reactive power output change with time (pu/s).

X6=∆(dVneg/dt), the differential rate of change negative sequence Voltage.

X7=∆(dIneg/dt), the differential rate of change negative sequence current. 20/02/2015


68

Fault Events Generation and Data Mining

Fault cases include :1020 Faults on different distribution line (DL1,DL2,DL3,DL4,DL5). Faults at different location of distribution line (10% - 90%). Variations in fault resistance varies Rf= 0.01 to 100 ohm. Types of shunt faults (LG,LLG,LL,LLL). Different operating modes : Grid-connected and Islanded) Topology of the network: Radial and Mesh. Variations in system loads. Faults with some DGs are out (e.g. DG1 out). Faults with some sections are out (e.g. DL3 is out and fault occurs at DL5).

No Fault cases include :415 Capacitor switching at PCC and load buses. Sudden load change at PCC and load buses (20 % overloading) Section cut-off (e.g. DL4 is isolated and micro-grid operating normally by

connecting through CB_LOOP1 and CB_LOOP2) DG outage (DG3 is out but no fault in any section of micro-grid )

Sample Operating conditions for Fault and No-Fault situation


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DT Generated for Fault Detection

DT generated during training with 80% of the total data (1148)

Testing is done with rest unseen 20% (287) data of the total generated data set

Features participating in original decision making are X1= ∆( df/dt), X2=∆(dV/dt), X3=∆(dPhi/dt), and X5= ∆(dQ/dt), keeping other features redundant (X4, X6 and X7)

Confusion matrix (testing)

Fault No-Fault

Fault 221 1

No-Fault 1 74

Classification Accuracy = 99.11%


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Performance Analysis

Events Grid Connected

Islanded

Fault 510 510

No-Fault 170 155

Events Radial Mesh

Fault 450 450

No-Fault 140 125

Performance of DT for fault detection in grid connected and islanded mode

Performance of DT for fault detection in radial distribution network and loop network

Number of events considered Number of events considered

Dependability Security Accuracy97

97.5

98

98.5

99

99.5

100

100.5

Perc

enta

ge

Grid connected mode

Islanded mode99.8%99.6%

98.24%

99.02%

99.475%99.35%

Dependability Security Accuracy97

97.5

98

98.5

99

99.5

100

Perc

enta

ge

Radial topology

Mesh topology

99.67%

98.49%

98.89%

99.2%99.08% 99.045%


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Performance Comparisons with Over Current and Current Differential Scheme

Dependability (%) Grid connected Islanded

Proposed intelligent differential relay 99.8% 99.6%

Over current relay 79.63% 23.89%

Current differential relay 84.26% 93.5%

Dependability (%) Radial network Loop network

Proposed intelligent differential relay 99.67% 98.89%

Over current relay 60.42% 40.44%

Current differential relay 86.81% 91.67%

Dependability of proposed relay, over current relay and current differential relay (grid connected and islanded mode)

Dependability of proposed relay, over current relay and current differential relay (radial and loop distribution network)


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Discussion

Fault conditions

Over current relay Grid connected mode Islanded mode

Relay at End-1

Relay at End-2

Relay at End-1

Relay at End-2

a-g fault on DL1 (radial) R1 Operates R2 Operates R1 Fails

R2 Operates

abc-g fault on DL2 (radial) R3 Operates R4 Operates R3 Fails

R4 Operates

ab fault on DL3 (mesh) R5 Operates R6 Operates R5 Operates R6 Operates

Current Differential current relay a-g fault on DL1 (radial) R1 Operates R2 Operates R1 Operates R2 Operate

abc-g fault on DL2 (radial) R3 Operates R4 Operates R3 Operates R4 Operates ab fault on DL3 (mesh) R5

Fails R6

Fails R5

Fails R6

Fails Proposed Data-Ming based Differential relay

a-g fault on DL1 (radial) R1 Operates R2 Operates R1 Operates R2 Operates abc-g fault on DL2 (radial) R3 Operates R4 Operates R3 Operates R4 Operates

ab fault on DL3 (mesh)

R5 Operates R6 Operates R5 Operates R6 Operates

Performance Assessment of the proposed DT based relay with the existing Over-current and Current-Differential Relay


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Conclusions

The proposed differential protection scheme is more efficient

than existing over current and current differential scheme.

The proposed differential protection scheme for fault detection

is highly effective (accuracy more than 99%) in detecting faults

at different operating mode of micro-grid.

The proposed differential protection scheme for fault detection

is highly effective (accuracy more than 98%) in detecting faults

at different network topology.

Speed accuracy of the proposed technique is 1 and 1/2 cycles .


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A person who never made a mistake never tried anything new.


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Albert Einstein

http://www.brainyquote.com/quotes/quotes/a/alberteins148788.html

THANK YOU


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