Fault Tolerant Power Systems Using

a System of Systems Protection Strategy

Saeed LotfifardAssistant Professor, Washington State University

NNovember 29, 2018 1/39

• Overview of system of systems protection

• Cascading failure protection strategy consists of digital

protection algorithms and special protection scheme (SPS)

• Summary

Outline

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System of systems protection

➢ Decentralized, component level protection methods

At different time scales

from milliseconds to several minutes

➢Distributed system level protection in the

form of wide area protection

• Special Protection Systems (SPS) / Remedial Action

Schemes (RAS)

• Wide area protection

• Under frequency load shedding

• Transient stability protection

• Voltage stability protection

• Digital protective algorithms for renewable

energy

• Digital protective algorithm for transformers,

synchronous generators

• Fault ride through capability of renewable

energy,

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1) Integration of large amounts of renewable energy sources

2) Digital protection, substation automation (e.g. IEC61850) and

communication based protection

3) High sampling rate data acquisition and synchro-phasor

technology (big data)

4) Integrated hybrid AC-DC power systems

5) Multi-area power systems with different system operators in

deregulated power systems

Paradigm shift in modern power systems

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Condition monitoring and protection of multi-physics hybrid systems

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Energy based monitoring method based on graph theory

A. Mojallal, S. Lotfifard, “Enhancing Fault Ride Through Capability of PV Systems” IEEE Transactions on Smart Grid, Accepted

A. Mojallal, S. Lotfifard, “DFIG Wind Generators Fault Diagnosis Considering Parameter and Measurement Uncertainties ” IEEE

Transactions on Sustainable Energy, Accepted.8/39

Stator

Rotor

R

T

5

G

T

3

G

T

5

G

T

1

Gearbox

Rotor Side Controller Grid Side Controller

Proposed FDI Module

Pitch Controller

Control and Protection Block

GSC Voltage and

CurrentPitch Angle

Sensor RSC Voltage

and

Current

Stator Voltage and

Current

DC-Link Voltage

Protection of wind turbine as a multi-physic hybrid system

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Electrical

Model

AI ModelGenerated

Signals

Generalized Model of PV farm

Feature

Extracti

on

DC system protection

N. M. Akram, S. Lotfifard, “Modeling and Health Monitoring of DC side of Photovoltaic Array” IEEE Transactions on

Sustainable Energy, vol. 6, no. 4, pp. 1245–1253, 2015

DC Microgrid

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Dynamic topology change

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PV ArrayL

3-level DC/AC

Inverter

C vdc

idc

Diode

Rf Lf

3

iabc Feeder Line

Power Grid

Yg/Δ

150 kVA

260V/25kV

Δ/Yg

5 MVA

25kV/120kV

3 MVA

Cos(φ)=1.0

vpv

ipv

MPPT using

Incond.

PWM

Generator

Duty Cycle

MAF-PLL

Vabc

abc

dq0

θ

Active/

Reactive

Power

Calculation

P Q

vd vq id iq

P

vpv

ipv

vdc

idc

FTSMC

controller

LVRT

Decision

vd

Grid-Code

Requirement

Assesment

iq*

idlim

LVRT

Decision

PBSMC

controller

PID

controller

vdc* vdc

+-

edc

u

iq*

idlim

PID

controller

id*

vdlim

vqlim

vd* vq

*

PWM

Generator

dq0

abc

vabc*

mabc

Enhancement of fault ride through capability

Type 1 LimitType 2 Limit

Must Remain

Connected Disconnection

Permitted

A. Mojallal, S. Lotfifard, “Enhancement of Grid Connected PV Arrays Fault Ride Through and Post Fault Recovery

Performance” IEEE Transactions on Smart Grid, In Pres.

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Grid Code for LVRT

A. Mojallal, S. Lotfifard, “Improving During and Post Fault Response of Fuel Cells in Symmetrical and Asymmetrical Fault

Cases” IEEE Transactions on Sustainable Energy

DC/AC

InverterCconv

vdc Rf Lfiabc Feeder Line

Power System

Y/Y

500 kVA

208V/12.5kV

DC/DC

Converter

Controller

PWM

Generator

Vabc

φ

P0des

Q0

vdLVRT

Requirement

iq*

idlim

PBSMC

iref-d+

mabc

DC/DC

Converter

PEMFC Power Plant

DC/DC

Converter

PEMFC1

PEMFC10

20 kW

Cos(φ)=1.0

RL Filter

Sequence Separation and

abc/dq0 transformation

iq+

id+vq

+vd

+iq

-id

-vq-

vd-

PLL

Reference Current

Calculation based on

(11)-(13)

u

vq+

vq-

iref-q+

iref-d-

iref-q-

+

-

id+

iref-d+

+

-

iq+

iref-q+

PBSMC

PBSMC +

-

id-

iref-d-

+

-

iq-

iref-q-

PBSMC

dq0

abc

dq0

abc

PWM

Generatorφ -φ

Proposed

Controllers

Cf

id+

iq+

id-

iq-

Enhancement of fault ride through capability

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Fault location in distribution systems with distributed generation

Smart

Garage

S. Lotfifard, M. Kezunovic, M.J. Mousavi, "A Systematic Approach for Ranking Distribution Fault Location Algorithms and Eliminating

False Estimates” IEEE Transactions on Power Delivery, vol. 28, no. 01, pp. 285 - 293, 2013.

S. Lotfifard, M. Kezunovic, M.J. Mousavi,” Distribution Fault Location Using Voltage Sag Data” IEEE Transactions on Power

Delivery, vol. 26, no. 2, pp 1239-1246, 2011

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Adaptive digital protection algorithms with high sampling rate

High Impedance Fault Detection 15/39

Communication based protection and substation automation using

IEC61850

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Communication based protection and substation automation using

IEC61850

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Wide area protection of multi-area hybrid AC-DC power system

with big data

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Wide area protection of multi-area hybrid AC-DC power system

with big data

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M. Rostami, S.Lotfifard, "Scalable Coordinated Control of Energy Storage Systems for Enhancing Power Systems

Stability" IEEE Transactions on Sustainable Energy, Accepted.

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48

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1111

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5150

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55

52

30

Area1

Area2

Area3

9

M. Rostami, S.Lotfifard, “Distributed Dynamic State Estimation of Power Systems" IEEE Transactions on Industrial

Informatics, Accepted.

Area# 2

Area# 3

Area# 1

Area# 4

Wide area protection of multi-area hybrid AC-DC power system

with big data

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Cascading Failure Protection using Digital Protection

and Special Protection System (SPS)

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Although the synchronous generator

remains synchronized to the grid, it is

disconnected due to mis-operation of

relays

The synchronous generator loses

synchronism and is disconnected from

the grid

Solution: Secure digital

protection algorithm

Solution: Special Protection

Systems/Remedial Action

Schemes (RAS)

Cascading failure of power systems under oscillations

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S

RLSlay Z

k

jkkZZZZ −

+−

−−

++=

22Re)(sin)cos(

sin)cos(

2

)(

G

Relay

Bus S Bus RESER

ZL ZRZS G

δ

Zone 1

Zone 2+X

+R

Unstable

Swing

Stable

Swing

K=1

Electrical

center

δ

ZS

ZR

ZL

Load

Pointθ1 θ2

Inner

BlinderOuter

Blinder

stable

nom

f

FPSBD

360

)((cycle) 21 −

=

θ1, θ2, Fnom and fstable are the machine angles at the

outer and inner blinder reaches (degree), system

nominal frequency (Hz) and power swing rate (Hz)

(which is assumed to be 1.2 Hz ).

S. Lotfifard, J. Faiz, M. Kezunovic, "Detection of Symmetrical Faults by Distance Relays during Power Swings,"

IEEE Transactions on Power Delivery, vol. 25, no. 1, pp. 81-87, 2010

Line distance protection

(1)

(2)

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22

2

22

22

*

2

QP

QVj

QP

PV

jQP

V

S

VjXRZ

+

+

+

=

−==+=

2- Two Zone with directional

• The impedance circles diameters are equal to 1.0 p.u. for Zone 1 and Xd for zone 2. The downward offset of the

zones is equal to half of the generator transient reactance. The typical time delay of LOE is 3 to 5 cycles (0.1 s) for

zone 1, and 30- 45 cycles (0.5- 0.75 s) for zone 2.

Zone 1

Zone 2

+X

+R

Xd

1.0

pu

Xd’/2

Unstable

Swing

Stable

Swing1- Two Zone:

Generator loss of excitation protection

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S.lotfifard, et all, Representation, Modeling, Data Development and Maintenance of Appropriate Protective

Relaying Functions in Large Scale Transient Stability Simulations (S-66), PSERC report

CAPE:

• Read and build the network topology

• Define the protection zones and relay settings

PSS/E:

• Run Load flow and Dynamic data

• Build Buses and Branches map files

CAPE-TS link:

• Define Δt for dynamic simulations

• Specify fault type, location, simulation time

• Initilize the CAPE TS-link

CAPE

• Update all mapped bus voltages from PSS/E

• Build sequence equivalent networks

• Calculate relay currents

• Evaluate relay operation, build the new grid

topology based on the breaker status

• Pass the new grid topology to PSS/EApply disturbance

CAPE: While time < Total simulation time

Init

iali

zati

on

Tra

nsi

ent

Sta

bil

ity

Cal

cu

lati

on

PSS/E:

• Advance simulation by one Δt

• Run dynamic simulation

• Calculate new voltages at all buses

Mai

n S

imula

tion L

oop

CAPE:

• Plot the output results

Co-simulation of protective relays response and dynamics of power systems

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WECC system (western electricity

coordinating council)

Buses LinesTransfor

mers

Genera

torsLoads

20681 16794 7814 3247 10717

• California- Oregon Intertie (COI) has three500-kV lines which deliver 4800 MW fromnorth to south in this peak load case.

• The inter ties over 100 kV between differentareas of WECC system are shown in the frontfigure.

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1- Stable Swing Condition

Disconnecting two lines of COI

Area #30

PG&E

Area #40

Northwest

30005R. M.

30020Olinda

999762 999765 999702

40687

45035

40684Malin

Substation

Captain JackSubstation

Area #73

WAPA RM)-

Colorado

45262Kfalls

500 kV COI

500 kV Lines

Substaion

Rest of the Grid

WECC system co-simulation

2- Unstable Swing Condition

Disconnecting all the COI lines

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Generator#1 LOE protection

zones (SEL 300G)

Distance relay protection

zones on branch 2-4

(SEL321)

Distance relay

protection zones on

branch 2-3(SEL321)

G

Relay 2

Relay 3

Relay 1

~

Bus 1

Bus 2 Bus 4Bus 3

E1 E2

ΔY

22/400 kV

600 MVA

Flt1

28/39

G

Relay 2

Relay 3

Relay 1

~

Bus 1

Bus 2 Bus 4Bus 3

E1 E2

ΔY

22/400 kV

600 MVA

Flt1

Relay operation in co-simulation

LOE relay

•During the stable swing, impedance

trajectory enters zone 2 of the LOE relay

at 0.65 s, then moves slowly inside the

protection zone, and exits zone 2 at 1.46 s.

•The delay of protection zones are less

than the time interval impedance passes

through the LOE relay zones (tsetting_Z2 <

0.81 s), LOE relay mis-operates.

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G

Bus A Bus BEI ES

XL XSXG

δ 0Breaker

G

LPF

A/D

FCDFT

Positive

SequenceZ=V/I

LOE Relay

VT

CT

)(sin)(

)()(

2

ttX

tkEtP

Te

S =

S

I

E

tEtk

)()( =

SysGT XXX +=

)(sin)(

)(

)()(cos

)(

)()(sin

)(

)( 2

222

tdt

tdX

tX

tkEt

dt

d

tX

tkEt

dt

tdk

tX

E

dt

dP T

TTT

e SSS

−+=

)(tan)(

1)(t

tkdt

tdk

dt

d

−=

Secure LOE relay during power swing

int2

105.1

fTD

Fault

cleared

Time (sec)

1 cycle

dδ/d

t

(1)

(2)

(3)

(4)

(5)

(6)

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Secure distance relay during power swing

==

(1)

(2)

(3)

(4)

(5)

(6)

(7)

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=

−=M

k

nkk zhnx

1

1ˆ

kjkk eAh

=

Skk Tfjk ez

)2( +=

Performance of classical Prony method and

GTLS-Prony method for a signal

Generalized Total Least Squares (GTLS)-Prony method for a signal

I. Kiaei, S. Lotfifard, A. Bose “Secure Loss of Excitation Detection Method for Synchronous Generators

during Power Swing Conditions ” IEEE Transactions on Energy Conversion, vol. 33, no. 4, 201832/39

Special Protection System (SPS)/Remedial Action Scheme (RAS)

1400 MW Chief Joseph dynamic braking resistor

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)1( −= isi

)(1

0qifi

dqi EE

TE

i

−

=

))1(1

(1

−−+−= ii

cimigi

miR

PPT

P

Power system dynamic model

))1()(( −−−−= iDisimis

i KPPPM i

)(1

refii

i

i sss

s PPT

P +−=

=

−−=

n

j

ijjiijqjdi YEI

1

)cos(

=

−−=

n

j

ijjiijqjqi YEI

1

)sin(

di

iitiqi

di

tidiqiei

x

VE

x

VIEQ

−−

==

)cos(2

di

iitiqiqiqiei

x

VEIEP

−==

)sin(

( ) fiadidididiqiqi IxIxxEE =−+=

qidiiitidi IxVV =−= )sin(

didiqiiitiqi IxEVV −=−= )cos(

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tosubject

kukxJ

N

k

kux

=1

,))(),((min

Nkkukxfkx ,...,10))(),(()1( ==−+

Nkkukxg ,...,10))(),(( =

Where

k : time step, x: system dynamic states, u: the available control options.

J: the control objectives, f: the set of equations that govern the system

dynamics, g: The constraints

Model Predictive Control (MPC)

tk tk+TS tk+TC tk+TP

Prediction horizon TP

tk-1 ... ... Time

Magnitude

Future / PredictionPast

uk

up

Control horizon TC

Future Control Signal

Previous Control Signal

Reference Signal

Previous State Trajectory

Predicted State Trajectory

xk

xp

(1)

(2)

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59

60

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10

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13

13

43

1212

44

45

34 35

39

51

50

1616

18

42

15

15

49

New-England 68-bus

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Rotor angle of generators without any controller

Rotor angle and speed of generator 11 37/39

Summary

• New protection schemes should be developed to address new

challenges of protecting modern hybrid AC-DC power systems

with high penetration of renewable energy

• Protection schemes should take full advantage of new

technologies in modern power systems

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Thanks!

Saeed Lotfifard

School of Electrical Engineering & Computer Science

Washington State University (WSU)

E-mail: s.lotfifard@wsu.edu

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