third us-africa research and education collaboration workshop abuja, nigeria, december 13-15, 2004 1...

Third US-Africa Research and

Education Collaboration WorkshopAbuja, Nigeria, December 13-15, 2004

1

Third NSF Workshop on US-Africa Research and Education CollaborationAbuja, Nigeria, December 13-15, 2004

TECHNOLOGY &

ENVIRONMENT

ENERGY &

EDUCATION

TECHNOLOGY &

ENVIRONMENT

ENERGY &

EDUCATION

Professors John Ngundam and Emmanuel Tanyi of Ecole Polytechnique, University of Yaounde I



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STRUCTURE OF THE AUTOMATION AND CONTROL LABORATORY (ACL)

Laboratory Director: Professor John M. Ngundam Power Systems, Renewable Energy and Environmental Simulation Group Leader: John Ngundam (Professor)

COMPUTER AND PROCESS CONTROL Group Leader: Emmanuel B. Tanyi (Associate Professor)

Telecommunications and Informatics Group Leader: Ndeh Ning, PhD

Center for Health Technology F. Sop Boyom, PhD

John M. Ngundam



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RESEARCH PROJECTS IN PROGRESS

Power Systems, Renewable Energy & Environmental Simulation

With 294 TWh of industrial scale hydro electricity resources and an enormous potential for small scale hydro electricity production for rural and remote area electrification, Cameroon is still a country with very low access rates to electricity. At the present time, only 7639 GWh a year of this potential is being produced to serve a population of 20 million not to mention export possibilities. Present research effort is directed towards the following:Generation and Network Expansion PlanningElectricity for Rural Electrification from Renewable Energy SourcesWater Resource Modelling and ManagementLoad ForecastingElectricity Markets (very recent addition)Analysis of Transients in Networks

Several long-, medium- and short-term generation planning software packages are being tested or nearing final development. Systems dynamics methods are being introduced in modelling water flows for use in developing large hydro plants and low voltage networks based on renewable energy sources.

John M. Ngundam



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RESEARCH PROJECTS IN PROGRESS CONTINUED

COMPUTER AND PROCESS CONTROL

Research into the electric system expansion and development of low voltage transformer free rural networks based on renewable energy have led to a need to develop system control technologies appropriate for controlling this and other systems. On going projects include:

Multivariate Control of the Southern network of the Cameroon Power SystemState SPACE Control of the Songloulou Power Generation StationMicroprocessor based Control of the Medium and Low Voltage Transmission Sytems of the Southern NetworkAnalysis of Pertubations in the Southern Network of the Cameroonian System

John M. Ngundam



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RESEARCH PROJECTS IN PROGRESS CONTINUED

Telecommunications and Informatics

Design and analysis of optimum and suboptimum receivers for signal detection in non-Gaussian noise

Application of self-critical statistical methods to signal detection. Information and communication technologies and society: governance,Sovereignty, digital divide

Computer and communication networks

Power line communication

John M. Ngundam



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REPORTS ON SELECTED PROJECTS

DIGITAL INFORMATION TRANSMISSION ON

ELECTRIC POWERLINES

COMPUTER AND PROCESS CONTROL

John M. Ngundam



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DATA TRANSMISSION OVER POWER LINES BY MODIFICATION OF THE POWER WAVEFORM

INTRODUCTION VOLTAGE SUPPRESSION AFTER ZERO-

CROSSING (VSZC)TECHNOLOGYMATHEMATICAL MODEL OF THE TECHNOLOGYERROR PROBABILITY CONSIDERATIONSLABORATORY RESULTSPERSPECTIVES

J.M. Ngundam



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DIGITAL INFORMATION TRANSMISSION ON ELECTRIC POWER LINES

The power waveform is modified after a defined duration , after the zero-crossing.

Technology demonstrated for transmission of signals for controlling (i.e. turning of and on) of devices connected to low voltage (220 V ) electric network and for remote meter reading.

In the Voltage suppression After zero-crossing (VSZC) technology, a bit “1” is assumed transmitted when suppression occurs and bit “0” when there is no suppression. Suppression time , is a critical parameter which determines the spectral distribution of the power signal and determines the error probability performance of the system.

J.M. Ngundam



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VOLTAGE SUPPRESSION AFTER ZERO-CROSSING

(VSZC) TECHNOLOGY

In VSZC technology, a bit “1” is assumed transmitted when suppression occurs and a bit “0” when there is no suppression.

Suppression time , is a critical parameter which determines the spectral distribution of the power signal and determines the error probability performance of the system

J.M. Ngundam



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MATHEMATICAL MODEL

Modified signal:

f(t) = AoSin (ωot) u(t), (1)

where u(t) is the unit step function defined as: 1 t > 0 (2) u(t) = 0 t < 0Without loss of generality, we analyse a single half period of the signal by adding an identical wave shifted version by T/2 (i.e. f(t) + f(t+T/2) to obtain. f1(t) = f(t) + f(t+T/2)

= Ao Sin(ot)u(t) +AoSin(o(t-T/2)u(t-T/2) (3)

J.M. Ngundam



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MATHEMATICAL MODEL CONTINUED

fTrans(t) = Ao Sin(ot)u(t - ) +AoSin(o(t-T/2)u(t-T/2) (4)

where ftrans(t) is the information signal propagated down the line. Modification power signal

results in harmonics which alter the supplied energy is altered. The energy of the modified signal is given by [1], as Em = A2

o (T/4) [ 1 - 2/T + 1/(o T) Sin(2o ) ] (5)

Higher harmonics do not appear at suppression. Optimum value of the suppression time is obtained from : 1 - 2/T + 1/(o T) Sin(2o ) 0 (6)

An iterative solution of (6) gives 1.2 < < 2.55 (7) In this technology, a value of = 1.6 ms was used. This value of also satisfied the utility energy supply because it does not drop to less than 90% of the generated value.

J.M. Ngundam



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MODIFIED POWER SIGNAL

J.M. Ngundam



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ERROR PROBABILITY CONSIDERATIONS

Transmission error is crucial to the success of the technology. Let the transmission of bits “1” and “0” as:

S1(t) = Ao Sin(ot)u(t - ) +AoSin(o(t-T/2)u(t-T/2) (8)

S0(t) = Ao Sin(ot)u(t) +AoSin(o(t-T/2)u(t-T/2) (9)

The probability performance of the system in terms of the error function Q(*), is given as:

Q() = Q{(Ev/No (2 - Sin(2) / (4 - 2 + Sin()}1/2 (10)

where Ev is the average signal energy and No is obtained from the noise waveform

possesing a Gaussian probability density function and a double –sided power spectral density.

J.M. Ngundam



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LABORATORY RESULTS

TESTS CONDUCTED

Remote control of various loads from a single point

Transfer of text between two computers

Adaptation of a standard utility meter for for electronic display and remote reading using the scheme. Inbound and outbound communications are possible provided the targets are within a radius of between 5 and 8 kilometers. If these distances are exceeded, detectability becomes a problem.

J.M. Ngundam



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PERSPECTIVES

Present investigations include include:

• Generation and load management for rural and remote stand alone electric systems without transformers. The radius of operation is limited to distances between 5 and 8 kilometres. This is ideal for rural settings in places like Cameroon.

• Remote meter reading and text transmission.

• Interfacing high speed data signals such as the INTERNET,

• Real time transmission of TV signals and voice communications on the power line, through the uses of compression techniques, powerline MODEMS, etc

J.M. Ngundam



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MULTIVARIATE CONTROL OF THE SOUTHERN NETWORK OF THE CAMEROONIAN POWER

SYSTEM

– - INTRODUCTION – - DEVELOPMENT OF A MULTIVARIATE

MODEL – - DESIGN OF A MULTIVARIATE CONTROL

SYSTEM– - PERSPECTIVES

Emmanuel B. Tanyi



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INTRODUCTION

Capacity of the Power System 805.7 MW Dominance of Hydro Stations : 720 MW (89.4 %) 3 Hydro Stations :• - Edea (264 MW);• - Songloulou (384 MW);• - Lagdo (72 MW)

Structure of the Power SystemNational Power System Organised into 2 Autonomous Networks :

Southern Network (Edea; Songloulou ) Northern Network ( Lagdo )

Emmanuel B. Tanyi



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Fig. 1 : Northern and Southern Networks of the Cameroonian Power Network

YAOUNDE(Oyomabang)

Songloulou

Nkong-Njock

Edéa

Mangombé

Logbaba

Békoko

N'kongsambaBafoussam

Bamenda

Limbé

BassaDeido

Bonabéri

Lagdo

Ngaoundéré

Garoua

Guider

Maroua

LEGEND

Power transmission Station : - 225 kV / 90 kV (Southern Grid) - 110 kV / 90 kV (Northern Grid)

Power transmission Station (90 kV)

Hydro Generating Station

Power transmission line : - 225 kV (Southern Grid) - 110 kV (Northern Grid)

Power transmission line (90 kV)

Emmanuel B. Tanyi



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Fig. 2 : Southern Grid of the Cameroonian Power Network

Songloulou

Mangombé

Logbaba

Oy omabang

Békoko

Limbé

N'kongsambaBaf oussam

Bamenda

Bonabéri

DeidoBassa

Mbalmay o

BRGMNgousso

Nkong-NjockEdéa

Koumassi225/90kV

225/90kV

225/90kV

225/90kV

10/225kV

10/90kV

LEGEND

Thermal Generation

Hy dro Generation

HV Loads

Emmanuel B. Tanyi



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PROBLEMS WITH THE SYSTEM

Supply far below demand = Frequent Load shedding

This situation is due to many problems : Obsolescence of equipment (Edea, 1953) Inefficient Control Strategies Industrial Expansion Galloping Population Expansion Decrease in the level of the Sanaga River Silting of the Dams

Situation requires a combination of many solutions.

One solution is the design of more efficient control strategies.

Emmanuel B. Tanyi



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DEVELOPMENT OF A MULTIVARIATE MODEL

• Hydro Generating Stations We have developed a system of 14 equations for each of

the generating stations• Flux Linkages due to Self and Mutual Inductances of the Rotor

and Stator:

r

r

r

s

s

s

3

2

1

3

2

1

rrrsrsrsr

rrrsrsrsr

rrrsrsrsr

srsrsrsss

srsrsrsss

srsrsss

LMMMMM

MLMMMM

MMLMMM

MMMLMM

MMMMLM

MMMML

coscoscos

coscoscos

coscoscos

coscoscos

coscoscos

coscoscos

Notation : 1, 2, 3 refer to phases while the subscripts ‘r’ and ‘s’ refer to the rotor and stator.

r

r

r

s

s

s

i

i

i

i

i

i

3

2

1

3

2

1

Emmanuel B. Tanyi



22

Voltage Equations for the Rotor and Stator Circuits :

1111 ssss dt

dIRV 2222 ssss dt

dIRV

1111 rrrr dt

dIRV

2222 rrrr dt

dIRV

3333 rrrr dt

dIRV

Electro-mechanical Equations ( Torque Equations ) :

dt

dJTT R ),,,( rsrsR iifT

Emmanuel B. Tanyi



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TRANSMISSION SYSTEM

• The transmission System is modelled as 5 subsystems :-• High Voltage Lines (225 KV) Medium Voltage Lines (90 KV) Low Voltage Lines (220V) Medium Voltage Station Low Voltage Station The Medium Voltage Station Steps down the voltage from 225kV to 90 kV

The Low Voltage Station Steps down the Voltage from 90 KV to 220 V.

Emmanuel B. Tanyi



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FIG. 3: COMPONENTS OF THE TRANSMISSION SYSTEM

225 KV Line

Medium Voltage Station

90 KV Line

Low Voltage Station

220 V Line

Emmanuel B. Tanyi



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DESIGN OF A MULTIVARIATE CONTROL SYSTEM

• Configuration of the Control System :• • A Distributed Control System incorporating 4• Multivariate Control Stations :

• - Edea Generation Station•• - Songloulou Generating Station•• - Medium Voltage Transmission Station•• - Low Voltage Transmission Station

Emmanuel B. Tanyi



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FIG. 4 : ARCHITECTURE OF THE DISTRIBUTED CONTROL SYSTEM

Edea Control Station (Hydro

Station)

Sondloulou Control

Station(Hydro Station )

Medium Voltage

Transmission Station

Low Voltage Transmission

Station

Emmanuel B. Tanyi



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CONTROLLER DESIGN STRATEGIES

• 3 Stategies :

Inverse Nyquist Array :

– · Use MATLAB to Calculate Multivariate Transfer Function– · Write Software to Calculate Inverse Transfer Function

– · Analyse Diagonal or Row Dominance– · Calculate Parameters of the Controller

Dyadic Control (Eigenvalue-based Design )

• Calculate Eigenvalues of Multivariate Transfer Function (MATLAB)

• Calculate Parameters of Dyadic Controller

Emmanuel B. Tanyi



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CONTROLLER DESIGN STRATEGIES cont.

First Order Approximation Method•

– · Simulate Closed-Loop System (without Controller) to generate Time Response Curves

– · Derive Approximate First Order Models from the Time Response Data

– · Calculate the Parameters of the Controller

Emmanuel B. Tanyi



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PERSPECTIVES

• The modelling aspect of the project is fairly complete, but Control Systems Design aspect is still in progess. This involves four Aspects :-– - Inverse Nyquist Array Controller

– - Dyadic Controller

– - First Order Approximation Controller

– - Evaluation of the Performance of the Controllers (MATLAB Simulation )

Emmanuel B. Tanyi



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INFORMATION TECHNOLOGY

Real-time Applications for Control of

Power Networks

Object-Oriented Modelling of Automatic

Control Systems

Simulation of Hybrid Control Systems

Emmanuel B. Tanyi



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REAL-TIME APPLICATIONS FOR CONTROL OF POWER NETWORKS

• 8 themes under Exploration :

1. Multi-tasking Operating Systems for Foreground- Background Control tasks

2. Implementation of Packages in JAVA and C++

3. Concurrent Execution of Packages using the technique of Multi-threading

4. Real-time Interface for Power System Control

5. Algorithms for the Implementation of State Observers

6. Digital Filters

7. Client-server Applications in Control

8. Communication Protocols for Real-time

Emmanuel B. Tanyi



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OBJECT-ORIENTED MODELLING OF AUTOMATIC CONTROL SYSTEMS

• Application of the Unified Modelling Language (UML) to Automatic Control Systems:

Discrete Systems :– - Class hierarchies for Grafcet (Function Chart) Objects– - Interactive Grafcet Construction– - Inference Engine for Grafcet Execution– - Class hierarchies for Petri Net Objects– - Interactive Petri Net Construction– - Inference Engine for Petri Net Execution

Continuous Systems :– Class Hierarchies for Equations– Objects for Block Diagram Construction

Emmanuel B. Tanyi



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FIG. 5 : OBJECTS HIERARCHY FOR THE

GRAFCET PARADIGM

1

Conditionne

Décrit E

TA

PE

TR

AN

SIT

ION

AC

TIO

N

RE

CE

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ITE

AC

TD

IRS

YS

LIE

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TIF

LIE

N P

AR

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N S

IMPL

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RE

CV

EN

SY

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AC

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SIM

PLE

AC

TIO

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UL

TIP

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(pa

ckag

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GR

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Emmanuel B. Tanyi



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SIMULATION OF HYBRID CONTROL SYSTEMS

Development of a Repertoire of Object Classes for Simulation of Sequential systems

Development of a Repertoire of Object Classes for Simulation of Continuous Systems

Modelling of Interactions between continuous and Discrete Components of a Hybrid System

Development of Continuous and Discrete Simulators

Concurrent Execution of the Two Simulators using Multi-threading

Application to Rolling Mill

Application to Power Systems ( Scheduling + Control)

Emmanuel B. Tanyi



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FIG. 6 : HYBRID SIMULATION OF ROLLING MILL

Emmanuel B. Tanyi

third us-africa research and education collaboration workshop abuja, nigeria, december 13-15, 2004 1...

Documents

ngundam power systems

ngundamresearch projects

low voltage networks

multivariate control

system control technologies

john ngundam professorcomputer

professors john ngundam

rural electrification