frame power system models for

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Oct 13, 2013 (3 years and 5 months ago)

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Decoupled symmetrical component
frame power system models for

smart grid application

Khalid Mohamed Nor

Mamdouh

Abdel
Akher

Syafii









Universiti

Teknologi

Malaysia

2011


Background


Power system models


Application


Fault analysis


Load Flow


Harmonic penetration study


Parallel computing

2

Presentation outline


The penetration of distributed generations (DG)
and distributed storage (DS), together known as
distributed energy resources DERs, changes
conventional distributions systems to active
distribution systems (ADS.



To operate ADS efficiently, they need to have the
ability to monitor many states and variables of
the network.



The Smart grid concept via the continuing
technological development and improvement in
communication technology, control devices and
instrumentations will provide the facilities.

INTRODUCTION


One of the important requirements for the ADS
planning, operation and control, is an accurate
steady
-
state analysis, such as power flow and
fault analysis.


The conventional power
-
flow analysis methods,
that are widely used for large power transmission
systems are based on the system positive
-
sequence representation.


These methods are deemed to be inaccurate for
unbalanced networks with single
-
phase laterals,
single and two
-
phase loads, centre tapped
transformer loads and unbalanced three
-
phase
loads as well as single
-
phase and three
-
phase
DERs.


INTRODUCTION


Many unbalanced system studies are analyzed based
on detailed three
-
phase network representation.


Three
-
phase power
-
flow methods that are
formulated based on phase components include two
categories.


Firstly, methods consider primarily the radial
structure of distribution networks.


Secondly, the method based on Newton
-
Raphson
technique has been applied for general network
structures.


In contrast to the general network structure
problem, the forward
-
backward sweep method, and
the compensation method solves for load flow
analysis of the system radial feeders and weakly
meshed grids methods based on the phase frame
approach.

Depending

on

reference's

frames,

the

three
-
phase

power

flow

formulation

can

be

modelled

using

phase

component

approach

and

sequence

component

approach
.


The

phase

component

using

forward/backward

method

[
Kersting

W
.
H
.
,

2001
,

Khusalani

S
.
,

et
.
at
,

2007
]

cannot

deal

with

a

highly

meshed

system

(IEEE

118

and

300

bus

test

systems)
.


The

sequence

component

using

Newton

Raphson

based

method

[Abdel
-
Akher

M
.
,

et
.
at,

2005
]

can

solve

load

flow

of

three

phase

unbalanced

system,

radial

and

meshed

systems
.

It,

however,

cannot

account

for

multi
-
phase

laterals
.


The

forward/backward

is

used

in

handling

multi
-
phase

lateral
.

This

method

will

lose

its

computational

advantage

when

dealing

with

a

large

number

of

laterals

systems

(IEEE

8500

test

system)
.

INTRODUCTION

The

focus

of

this

paper

is

to

develop

a

symmetrical

component

based

models

for

a

general

large
-
scale

network
.


The

models

can

be

used

to

analyse

general

network

that

contains

almost

all

practical

distribution

system

features

with

composite

meshed

network

and

radial

feeders
.

The

algorithm

has

included

steady
-
state

DG

models

and

center
-
tapped

(CT)

transformer

load

model
.


The

DG

models

that

have

been

developed

include

cogeneration,

photovoltaic

and

wind

turbine

generator
.

The

voltage
-
controlled

and

complex

power

injection

node

models

are

considered
.

The

network

structure

to

be

full

decomposed

which

is

amenable

to

implement

parallel

computing


Symmetrical

component

models

of

three

phase

system

is

well

established
.

The

modelling

accounts

for

four

wire

systems

as

well

ground

wires
.




The

following

slides

give

details

on

decoupling

techniques,

multi
-
phase

laterals

line

model,

DG

models

and

centre
-
tapped

(CT)

transformer

load

model,

which

are

not

covered

in

the

classical

symmetrical

component

modelling
.


Power System Model

9

The

admittance

matrix

of

symmetrical

component

of

unbalanced

system

has

off
-
diagonal

elements
.

In

order

to

decouple

the

symmetrical

component,

AbdelAkher

and

KM

Nor

have

proposed

method

compensation
.

DECOUPLING OF SYMMETRICAL COMPONENTS

Y V
=
I

Representation of multi
-
phase system using dummy lines and nodes

The biggest challenge of applying decoupled symmetrical
components is the modeling of multi
-
phase lines.

M. Abdel
-
Akher, and K. M. Nor, “Fault analysis of multiphase
distribution systems using symmetrical components”,
IEEE
Transactions on Power Delivery
, Vol 25, Oct 2010


Synchronous Generation Based WTG Model







By knowing of injected power and voltage magnitude at a generator bus, the
WTG can be modelled as voltage controlled device. If the Q limit is used, the
PV model will be automatically converted to a PQ model.

1. Regulation excitation voltage model as
PV node

2. Fixed excitation voltage model as
PQ node
(Round rotor SG)

The WTG power output is can be determined from the power
-
speed curve
provided by its manufacturer, such as:

0

100

200

300

400

500

0

2

4

6

8

10

12

14

16

18

20

22

24

Power (kW)

Wind Speed (m/s)

Vestas V39 500 Power Curve

Wind Turbine Generator Models

Wind Turbine Generator Models


Induction Generator Wind Turbine






Active

power

output

obtain

from

the

power

curve

of

the

WTGU

(provided

by

the

manufacturer)

for

given

wind

speed
.


Q is found by solving as follows.

The

reactive

power

consumed

depends

on

node

voltage

at

WTG

connection,

which

is

updated

during

power

flow

iteration

process
.

Photovoltaic Models

The

voltage
-
current

(VI)

equation

of

PV

device

given

by
:


I
pv
is

function

of

solar

radiation

and

temperature,


I
0

dependence on the temperature

Power output is given by

Parallel Processing Implementation

The

decoupled

symmetrical

component

models

are

inherently

paralleable
.



Nowadays,

multi
-
core

processor

chip

has

brought

parallel

computing

to

the

ubiquitous

PC
.

It

means

that

the

hardware

cost

is

the

same
,

whether

used

as

a

serial

processing

system

or

a

parallel

processing

system

The

parallel

algorithm

developed

using

visual

C++

programming

under

Visual

Studio

2008

with

an

OpenMP

and

Intel

C++

compiler

to

support

parallel

processing
.


OpenMP

(Open

Multi
-
Processing)

provides

parallel

processing

using

thread

based

and

shared

memory

parallel

programming
.

From the decoupled symmetrical component models, we

can construct matrices, Y
1
, Y
2

and Y
3
, which correspond to

the positive, negative and zero sequence admittances

respectively.


Y
1

V
1

=
I
1


Y
2
V
2

=
I
2


Y
0
V
0

=
I
0


Once the sequence networks have been determined,

computation of the unbalanced faults which have been well

Established can be applied.

In fact, any unbalanced fault analysis commercial software
can use the models proposed to analyse any three phase
unbalanced networks with multi
-
phase feeders.

Unbalanced fault analysis

16

Parallel sequence component three
-
phase power
-
flow algorithm

The

problem

decomposed

into

tasks
.

These

tasks

can

be

worked

on

independently

of

the

others

and

run

under

the

multiple

processors

system
.

The

problem

that

can’t

be

decomposed

will

use

parallel

loop
.

17

Incorporating CT Transformer Load Model

The

unbalanced

load

connected

to

center
-
tapped

transformer

via

service

lines

solved

using

voltage

drop

analysis

in

three
-
phase

load

flow

iteration
.

The

CT

Transformer

Load

modelled

as

power

injections

S
ab

=
S
l1
+S
l2
.

V
ab
from power flow calculation.

The

proposed

algorithm

is

validated

by

comparing

with

forward/backward

sweep

method

using

a

radial

distribution

analysis

package

(RDAP)

for

the

original

of

37

node

feeder

and

IEEE

13

node

feeder
.

The

results

are

the

same

correct

to

significant

figures
.

RESULT

AND

DISCUSSION

Tests to show the
ability of method to
handle meshed and
radial feeders is
carried out by solving
a composite test
system which is a
combination of Taiwan
Power company 24
b(unbalanced three
phase system) and
radial feeder networks

The

new

development

in

distribution

system

analysis

tools

needs

to

test

the

robustness

of

their

algorithm

using

IEEE

8500
-
node

test

system
.

This

system

is

a

latest

data

(published

2010
)

by

IEEE

PES

distribution

system

analysis

subcommittee

used

to

test

the

robustness

of

the

algorithm

for

large

system’s

problem
.

Performance in Solving Large
-
Scale Distribution System

The Results of Modified TCP 24 Bus with DG

DG Impact Analysis of IEEE 8500 node test case

Performance results of IEEE 8500
-
node test case under 2.66 GHz PC

The proposed algorithm can be
extended for solving repetitive
applications in power system
analysis such as fault analysis with
contingency assessments and three
-
phase harmonic power flow study.

The speedup advantage from parallel
programming can be significant in
larger
-
scale power system problem.
.

The network harmonic admittance
matrix can be obtained by calculating
the impedance at each harmonic
frequency,









The following Equation is used to
solve for harmonic voltage for each
harmonic frequency:


Unbalanced Harmonic Penetration


The

decoupled

symmetrical

component

frame

power

system

models

has

been

succesfully

used

to

all

components

of

active

distribution

systems
.



The

DG

models

that

have

been

considered

are

cogeneration,

PV

and

WTG
.

The

variation

of

wind

speed

(m/s)

for

WTG,

solar

radiation

(W/m²)

and

temperature

(
C)

for

PV

have

been

simulated
.




Load

flow

solver

using

the

models

has

been

benchmarked

against

commercial

software

for

the

three

phase

load

flow

and

also

compared

with

a

forward/backward

method
.



It

shows

that

the

proposed

method

has

good

convergence

properties,

accuracy,

efficient

and

robustness
.


Summary


The

simulation

results

show

that

the

proposed

DG

model

can

be

used

to

analyse

DG

impacts

in

the

unbalanced

meshed

and

radial

distribution

system
.



The

analysis

using

proposed

decoupled

model

has

significant

computing

parallelism

which

has

been

exploited

in

a

multi
-
core

PC

Based

parallel

programming

for

sequence

decoupled

three
-
phase

power

flow

analysis
.



The

parallel

execution

of

the

proposed

algorithm

produced

computational

speedup



The

analytical

tools

using

the

decoupled

symmetrical

components

can

be

used

to

for

planning

and

operation

of

ADS,

i
.
e

used

as

an

analytical

component

of

a

smart

grid
.

Future Work




The

optimal

DG

size

and

location

have

not

been

considered

yet
.




The

optimization

methods

to

determine

the

optimum

size

and

an

effective

methodology

to

identify

the

best

location

for

DG

placement

can

be

investigated

in

further

research
.



Thank you