JKU/2/33/65(12)
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
COMPENDIUM OF RESEARCH ACTIVITIES 2011/2012
1.0
Ongoing Research
Topic
Multi-Antenna Techniques for Quality of Services (QoS)
Improvement in Wireless Communication System.
Researcher(s)
Muiga Rugara, D. O. Konditi, S. Musyoki, Langat Kibet, Kariuki
Ngige.
Ongoing
Status of the Research
Topic
Researcher(s)
Design and Analysis of Neural Fuzzy Based DC-DC Converter
Controller Optimized with Swarm Intelligence
Kanai .M Michael, John .N Nderu and Peterson .K. Hinga
Status of the Research
Ongoing
Topic:
Impact of Fuzzy and Neural Network Techniques in Dynamic Load
Modelling for Voltage Stability Analysis
Researcher(s):
C. M. Muriithi, L. M. Ngoo, G. N. Nyakoe
Status of Research:
Submitted Thesis for Examination
Topic
Researcher(s)
Possibility of Deregulating Retail Electricity Market for 5 heavy
Industrial Electricity Consumers in Kenya
George K Irungu
Status of the Research
ongoing
Topic
Study of existing Solar PV Home Systems with an intension of
developing a customized Kenyan solar PV home system.
Researcher(s)
Shtomu Ohzuku, Gideon G. Kidegho, George Nyakoe
Status of the Research
Ongoing
Topic
Performance analysis of mobile ad hoc network routing protocols
using Self Organising Map (SOM)
Researchers
Mureu Ephraim W., Stephen Musyoki and Peter Kihato
Status of the Research
Ongoing
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Topic
Underdetermined Blind Speech De-Noising for Enhanced
Teleconferencing Using Machine Intelligence.
Researchers
Denis Ombati , . E N Ndun‘gu and L. M. Ngoo
Status of the Research
Topic:
Ongoing
Electronic Load Controller for Mini/Micro Hydro Power
Generation
Researcher(s):
C. K. Kitur, J. N. Nderu, K. Kaberere
Status of Research
Ongoing
Topic:
Researcher(s):
Static Voltage Stability Analysis of Nairobi Area Power Distribution
Network
S. Oketch, C. M. Muriithi, K. K. Kaberere
Status of Research:
Ongoing
Topic:
Adaptive Real-Time and Virtual Monocular Car Vision using
Modular Artificial Neural Networks
Researcher(s):
Inno Odira, P. K. Kihato, S. I. Kamau
Status of Research:
Ongoing
Topic:
Application of Neural Network for Short Term Load Forecasting
Researcher(s):
Ireri T. Gichovi, N. O. Abungu, D. K. Murage
Status of Research
Ongoing
Topic:
Researcher(s):
Enhancement Of Electrical Power Supply Using Grid Connected
Photovoltaic Generation: A Case Study Of Nairobi Embakasi
Suburb
G.G. Kidegho, K.K. Kaberere, M.S. Mbogho
Status of Research
Ongoing
Topic
Researcher(s)
Analysis and Design of Electrical machines Speed monitoring
systems using Amorphous wires
J.N. Nderu, Dr. P.K. Kihato, A. Muhia
Status of the Research
Ongoing
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Topic
Researcher(s)
Status of the Research
Performance Analysis of a Generator Operating on Dual Fuel
Comprising of Biogas and Diesel
Nelson Muchiri Gachoki, Peterson K. Hinga, Njeri S. Kahiu,
Stephen Wanjii
Ongoing
Topic:
Application of Neuro-Fuzzy Control Technique in a Three-phase
Hybrid Power Filter for Harmonic Mitigation.
Researcher(s):
Nelson K Bett, P. K. Hinga, J. N. Nderu
Status of Research
Ongoing
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2.0 Completed Research
Title
Impact Of Fuzzy And Neural Network Techniques In Dynamic
Load Modelling And Voltage Stability Analysis
Researcher(s)
C. M. Muriithi, L. M. Ngoo, G. N. Nyakoe
Background:
This research deals with modeling and description of the dynamic
load characteristics for long-term voltage stability studies. The main
component of the dynamic loads constitutes the induction motor
loads. The research comprised of developing a neuro-fuzzy
induction motor load model which was then incorporated in a
Newton-Raphson power flow algorithm. The modified load flow
incorporates a neuro-fuzzy induction motor load model that
estimates the scheduled active and reactive power adjustable during
each iteration process. The impact of the aggregated induction
motor on the convergence characteristics of load flow are
investigated using the IEEE-30 bus standard test system. Based on
the load flow results, counter propagative artificial neural networks
were used to classify buses in order of weakness.
In this research, the neuro-fuzzy model of an induction motor load
was extended into the Continuation Load flow algorithm, where the
impact of different induction motor ratings on the voltage stability
margin was investigated.
The research finally investigates the impact of the Fuzzy Logic
based Power System Stabilizer (FLPSS) in maintaining short term
voltage stability in a system with Induction Motor Loads. From the
analysis which compared the FLPSS with other PSS found in
literature, it was shown that the FLPSS could not maintain stability
of an induction motor load after being subjected to a fault.
Methods:
Modeling of an induction motor load using neuro-fuzzy techniques
has been illustrated and a novel method of solving the load flow
equations with neuro-fuzzy induction motor models. This novel
load flow is tested on the IEEE 30 bus system.
In addition, a novel method of solving the continuation load flow
equations with neuro-fuzzy induction motor models.In this
algorithm, the load increment was carried by increasing the
induction motors loads modeled using neuro-fuzzy techniques.
Finally, the impact of fuzzy logic PSS on short term dynamic
voltage stability is investigted. The system to be evaluated was
simulated in detail in Simulink®. The generators were also fitted
with the governor and excitation system, with the possibility of
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selecting different PSS to be compared in the analysis. Further an
induction motor load with undervoltage protection has been
modeled. In this set up, an investigation is carried out of the impact
of fuzzy logic PSS in a multi machine system with a large induction
motor load.
Results:
The conventional load flow algorithm upgraded to incorporate the
non-linear neuro-fuzzy model of induction motor load showed
improved accuracy, though at reduced convergence rate.
Further, a novel continuation load flow algorithm that incorporates
neuro-fuzzy induction motor loads has been developed and
analyzed indicating the need to model loads so as to give an
accurate assessment of the security margin.
Finally, the effects of the excitation system equipped with PSS have
been shown to be very crucial in voltage stability studies.
Conclusions:
The neuro fuzzy model of an induction motor load aided in
assessing more accurately the security margins of a given system.
This is crucial information for power system engineers. On the
other hand, the Fuzzy Logic Power System Stabilizer failed to
maintain the stability of the system with an induction motor load.
Title
Impact of Spartial Diversity Techniques In Combating Interference
and Multipath Fading in Wireless Communication Systems.
Researcher(s)
Muiga Rugara, D. O. Konditi, S. Musyoki
Background:
The next-generation wireless communication systems are required
to have high voice quality as compared to current cellular mobile
radio standards and provide high bit rate data services (up to 2
Mbits/s). At the same time, the remote units are supposed to be
small lightweight pocket communicators. Furthermore, they are to
operate reliably in different types of environments: macro, micro,
and picocellular; urban, suburban, and rural; indoor and outdoor.
However wireless communication systems require signal processing
techniques that improve the link performance in hostile mobile
radio environments. Most existing wireless systems use simple
antenna arrays transmitting in a fixed direction (directional
antennas) or all directions (omnidirectional antennas). This causes
interference between subscribers. Furthermore, with the rapid
increase in cellular subscription, capacity will be an issue in future
communication systems, One approach to increase capacity is to
reduce interference and compensate for multipath fading and a cost
effective method of achieving this is the use of diversity techniques.
The technique proposed in this paper is a simple transmit diversity
scheme which improves the signal quality at the receiver on one
side of the link by simple processing at the transmit antennas on the
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opposite side. The proposed transmit diversity scheme will improve
the error performance, data rate, or capacity of wireless
communications systems. The scheme may also be used to increase
the range or the coverage area of wireless systems.
Methods:
To demonstrate the optimum combining in a fading environment,
an experimental system will be modeled and simulated. Simulation
will comprise an m transmit antennas and n receive antennas, a
channel estimator will be used at the receiving antennas. The
combiner builds the incoming signals that are sent to the maximum
likelihood detector. These combined signals are then sent to the
maximum likelihood detector which, for each of the signals uses the
decision rule to determine the strongest signal combination. The
resulting combined signals will be expected to be equivalent to that
obtained from two-branch MRRC. The only expected difference is
phase rotations on the noise components which do not degrade the
effective SNR. Therefore, the resulting diversity order from the new
m-branch transmit diversity scheme with n receivers is expected to
be equal to that of two-branch MRRC.
Results:
A 2-transmit 2-receive (2x2) MIMO channel with Maximum
Likelihood (ML) decoding receiver structures gives a good
performance. However it is inferior to alamouti 2-transmit 2-receive
STBC. However, it was found that the use 2×2 MIMO with
Maximum Likelihood (ML) equalization achieves a performance
closely matching the 1 transmit 2 receive antenna Maximal Ratio
Combining (MRC) case. It is also apparent that the use of a higher
order constellation like 64 QAM, then computing Maximum
Likelihood equalization might become prohibitively complex. With
64 QAM and 2 spatial streams we need to find the minimum from
642 = 4096 combinations. In such scenarios we might need to
employ schemes like sphere decoding which helps to reduce the
complexity and which are outside the scope of this research.
Conclusions:
Use of multiple antennas at the transmitter and the receiver in
wireless communication systems have been known to increase
diversity to combat channel fading. Each pair of transmit and
receive antennas provides a signal paths from the transmitter to the
receiver. By sending signals that carry the same information through
different paths, multiple independently faded replicas of the data
symbol can be obtained at the receiver end; hence more reliable
reception is achieved.
It is also clear that the BER performance for a 2-transmit 2-receive
(MIMO) Alamouti STBC Channel is much better than 1-transmit 2receive antenna MRC case. This is because the effective channel
concatenating the information from 2 receive antennas over two
symbols results in a diversity order of 4. In general, with N receive
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antennas, the diversity order for 2 transmit antenna with Alamouti
STBC is 2N. As with the case of 2-transmit, 1-receive Alamouti
STBC, there is no cross talk after the equalizer since the matrix is
diagonal and the noise term is still white.
Title:
Load Modeling and Comparison of Aggregation of Induction
Motor Loads in a Power System for Voltage Stability Analysis
Researcher(s)
J.K. Muriuki, C.M.Muriithi, D.K.Murage
Background:
Induction motors constitutes a large percentage of power system
components and may cause voltage instability if not properly
controlled under fault conditions. This is more pronounced in
developing nations where the demand for power surpass the supply
thereby, compelling power system to operate at very low power
reserves and particularly during the peak loads. The power system
network is also expanding daily thereby distressing the existing
generation, transmission, distribution capacity and protection
controls. It is therefore important to ensure that there is enough
power generation by interconnecting countries power bank to form
one large power pool thus improving the power supply reliability
and quality.
It is also crucial to analyze and compare the parameters of the
aggregate induction motors of different sizes under most of the
operating conditions of the power system. The two methods are
transformer-equivalent circuit (method 1) and no-load and locked
rotor (method 2).The two methods of aggregation were selected
because they are accurate in motor parameter identifications and
therefore better suited for comparison purposes. Also the methods
were selected because researches on their comparison have not
been systematic. This necessitates exact modeling of the power
system load which is a difficult problem because the power system
loads are aggregation of many and different devices.
It is vital to understand dynamic load behavior of various
consumers which in more often has proved to be a challenge. Static
loads are inaccurate in capturing the characteristics of the load
under various operating conditions and therefore dynamic load is
considered necessary when studying voltage instability because it
captures the actual behavior of the load at a particular time.
Methods:
The two methods of aggregations were compared to identify their
accuracy in identification of aggregate motor parameters for voltage
stability analysis. The range of motor used was classified as small
ranging from 3hp to 100hp and large motors ranging from above
100hp to 2250hp. The IEEE 16 bus system was used for the setup
and analysis.
A MATLAB code was written to identify the aggregate motor
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parameters for both small and large motors. For the simulation
results, the small and large induction motors whose total load was
2250hp were inserted in bus 3 of the IEEE16 bus and their
parameters identified under steady-state and under system
disturbance. The parameters obtained were compared to the
standard motor parameters to identify their accuracy using the two
methods of aggregations.
Results:
Further, the effects of Multi-Band Power System Stabilizer (MBPSS) on the aggregation of the motor parameters using the two
methods of aggregation were compared to identify the most
accurate. From the analysis carried out it has been shown that
method 2 is superior to method 1 in identification of the aggregate
motor parameter, and at the same time, it has shown improved
results under the influence of MB-PSS under system disturbance.
The aggregation method 2 showed improved accuracy in
identification of the small and large aggregate motor parameters
compared to method 1 under steady-state and under system
disturbance.
The inclusion of MB-PSS in the generator showed improved
performance of the aggregate motor parameters for method 2
compared to method 1. Finally, the effects of the excitation system
equipped with MB-PSS have been shown to be very crucial in
voltage stability studies using method 2 of motor aggregations.
Conclusions:
It has been shown that static loads are unsuitable in describing the
load dynamics under various power system operating conditions.
They therefore, give false expression of the power system stability.
The results also confirm that parameters to which the
measurements have large sensitivities are observable and could be
identified, while those to which the measurements have small
sensitivities are hard to be identified.
The accuracy of the aggregation method based on the two
aggregation methods was compared. The results show that, method
1 is inferior in identification of the aggregated motor parameters for
both small and large IM compared to method 2. The simulation
results drawn a close resemblance thereby validating the method
applied. Therefore, method 2 is best suited for voltage stability
analysis.
The comparison for the aggregation method 1 and 2 under the
influence of Multi-Band Power System Stabilizer (MB-PSS) for
voltage stability analysis was investigated. The result shows that
aggregation method 2 is superior in identification of the aggregate
active and reactive motor parameters compared to method1.
With the implementation of method 2 under the influence of MB-
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PSS, the power utilities are expected to benefit from good design
and reliable protection controls, assist the energy policy makers to
plan on system expansion with a view to providing resources. It will
also help the power system engineers and operators to understand
the system load dynamics characteristics under various disturbances
thereby maintaining voltage stability. Finally, it will improve the
process and accuracy of power system planning and operation and
make coherent and economic decisions.
Title
Mitigation Of Harmonic Distortions and Low Power Factor In
Unbalanced Three Phase System Using Fuzzy Logic Controller
Researcher(s)
Charles Ndung’u, L. Ngoo, J. Nderu
Background:
In recent time, the power quality has attracted a lot of attention due
to extensive emphasis by power utility on the power system
efficiency and end users awareness of power quality issues. This has
occurred mainly due to the sensitivity of the modern equipment and
the deregulation of the power distribution. In addition, there are
usually massive losses both to power utility and end users which
result in poor power quality supplies which fall below the set
standards. Power quality primarily constitutes of voltage dip/ swell,
power system interruptions (power outage), harmonic distortions,
voltage flickers and frequency deviations. Research done on both
power utility and customers revealed that power outage caused
myriad complains from the customers seconded by harmonic
distortion which was raised by both parties. Nevertheless, end users
sector suffer more from harmonic problems than does the utility
sector. Industries with Adjustable Speed Drives (ASD), arc furnace,
induction furnaces, are more susceptible to problems stemming
from harmonic distortions.
Harmonic distortion is the change in the waveform of the supply
current/ voltage from the ideal sinusoidal waveform. The primary
source of distortions of the waveform is non linear loads. The non
linear loads generate current harmonic distortions and reactive
power from ac mains. The device or equipment is said to be nonlinear when the relationship between the instantaneous voltage and
current is not linear. Examples of these kinds of loads include
computers, switch mode power supplies, fax and printers. They
mainly consist of electronic power supplies and with the
proliferation of customer loads with electronic power supplies
means that the growth in the harmonic distortion system is
inevitable. These non linear loads inject back harmonic distortions
into power distribution systems through the Point of Common
Coupling (PCC); point where end users are connected to the power
grid by the power utility.
Harmonic distortions have a number of adverse effects on the
distribution system and at the end users. When present in the power
lines results in various problems such as; greater power losses in
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distribution and transmission lines, problems of electromagnetic
interference in communication systems, operation failure of
protection devices and electronic devices. In additional, they cause
erroneous measurement in the energy measurement and capacitor
banks failure. These problems result in high costs for industry and
commercial activities, since they can lead to a decreasing in
productivity and to a reduction of quality in the products or
services.
Inductive load requires reactive power for proper operation
(magnetization) and thus the source must supply hence increasing
the current from the generator and through power lines. Total
current distributed through the conductors and transformer consist
of two components namely; active component and reactive
component
High reactive current implies increase of total current. High current
makes conductors and transformers to overheat (i2R) hence
demanding conductors of large cross-section area and bigger size of
the transformer. If reactive power is supplied near the load, the line
current can be reduced or minimized and hence reducing power
losses and improving voltage regulation at the load terminals. The
reactive power is defined as component of the instantaneous power
with frequency equal to 100 Hz in a 50 Hz system. The reactive
power oscillates between the ac source and the capacitor or reactor
and also between them (inductor and capacitor) at frequency equals
to two times the rated value. Due to this behavior, it can be
compensated using active power filter to avoid it circulating
between the load (inductive or capacitive) and the source hence
improving power factor at the point of common coupling.
Methods:
The study provides a fast compensator of harmonic current
distortions and reactive power by employing fuzzy logic controller
due to its ability to adapt on variations of non linear loads. This
ensure that the source only supply the active power with minimum
distortions which is below the admissible levels as recommended by
the power quality standards.
The Pulse Width Modulation control system based on time domain,
the p_q theory or ‗Instantaneous Power Theory‘ which was
proposed and developed by Akagi et al in 1983, is employed to
generate the reference signal for Voltage Source Inverter (VSI).
Fuzzy logic controller is being used to maintain the dc side of the
VSI constant. Hysteresis current controller is used to generate the
gating signal for Insulated Gate Bipolar Transistor (IGBT) which
neutralizes the harmonic distortions by injecting a signal similar as
line harmonic distortions but with opposite sign through the
coupling inductor.
In addition, the study involved data collection at different metering
points of utility power company. This was to establish at which
point of metering high harmonic distortions exist and hence
simulate the active filter capable of eliminating harmonic distortions
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to the point identified with high harmonic distortions.
Results:
The researcher collected the data at various power utility system
metering points and presented it in table forms for the purpose of
establishing why most of large power end users are unable to
achieve a power factor that is above statutory level limit of 0.9.
From the data collected, it has been found that end power users
supplied with voltage 0.415kV are the most susceptible due to
presence of high current harmonic distortions at the point of
common coupling. The sources of current harmonic distortions are
generated by the non-linear loads such as electronic devices with
switch power mode supply, speed variable drives and cycloconverters. The Medium and High voltage end power users are
rarely surcharged on low power factor. The reason is due to
availability of voltage step down Harmonic mitigation transformer
before the point of common coupling (metering point) unlike the
low voltage end users where generated harmonic pollution is inject
back to the power system at PCC.
Harmonic distortions are found to play a key role on CPF recorded
by the static energy meter due to capability of sampling analogy
signals (current and voltage) at high sampling frequencies than
fundamental frequency. Apparently, presence of high harmonic
distortions increases apparent power recorded by the energy meter
consequently resulting to low CPF.
It has been shown that the simulated APF improves the harmonic
filtering performance and compensate for reactive power hence
giving better transient and steady state response to LV power
system under unbalanced condition. Simulation was done using
MATLAB-SIMULINK modeling software used for dynamic
systems.
Conclusions:
The analysis of the data obtained on harmonic distortions on utility
power system and simulation carried out of APF using MATLAB –
SIMULINK environment lead to the following conclusion;
(a) The three phase power end users supplied by Low Voltage
were generating high current harmonic distortions beyond the
recommended threshold as per IEEE 519-1992 power quality
standard. This has resulted to most of these end users not to
meet the power factor statutory level of 0.9 as required by the
power utility. The reason for not achieving the statutory PF is
due to the advent of digital meters which are capable of
measuring harmonic energies.
(b) The energy meter measures the harmonic order levels if it has
as sampling frequency higher than twice the fundamental
frequency (Nyquist theorem->100Hz). Harmonic distortions
increases the apparent power (kVA) measured by the energy
meter and consequently recording low power factor.
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(c) In this study, an active power filter has been used to eliminate
undesirable effects of poor power factor and current
harmonic distortions for low voltage power users at PCC. The
active filter was simulated using IRP p_q theory algorithm
proposed by Akagi and others.
(d) The IRP p_q theory has proven to provide a reasonable
approach analysis and hence control compensate the reactive
components of non linear load. In addition it acts as
appropriate measure for mitigation of Total Current
Harmonic Distortion to improvement of power quality at
PCC.
(e) A three phase unbalanced system with a three phase IGBT
rectifier supplied a resistive single phase load. The harmonic
current distortions generated by non-linear load were
neutralized by injecting an opposite waveforms to the system
hence eliminating the distortions and compensating for
reactive power in time domain.
(f) It can be summarized that the simulated shunt active power
filter;
 Compensate dynamically the currents harmonic distortions,
 Compensate dynamically the reactive power hence
improving the power factor at PCC and
 Reduces the values of the currents supplied by the source to
the load by compensating the reactive current required by
the supplied loads.
(g) Time domain provides fast response for harmonic and reactive
compensation as the system parameters are analyzed on real
time. This ensured that the harmonic distortion at PCC are
within the recommended level by IEEE 519-1992 and the
meter records a power factor well above the statutory
requirement of 0.9.
Title:
Determination of Reactive Power Compensation and Transmission
Line Power Transfer Capability Improvement of The Kenyan
Power System
Researcher(s)
Robert Kariuki Njoroge, Keren Kaberere, Aloys Akumu
Background:
To supply power, utilities usually sign a supply agreement with the
consumer that states details of power supply to be connected. This
allows the consumers to specify the voltage rating of any electrical
equipment procured for use in their premises. Once the supply is
connected, the consumer expects the voltage and frequency to be
maintained nearly constant within the statutory tolerances and to
experience minimum interruptions.
For a utility to effectively meet the requirements of the consumers,
the power system must be properly controlled, where the main
parameters to be controlled are voltage and frequency. To supply
the system loads, a number of generating stations are
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interconnected through transmission lines and distribution network.
The frequency of the system is controlled by ensuring real power
balance of supply and demand; frequency is controlled centrally.
However, the transmission and distribution systems need voltage
control at various points in the system to maintain the voltage at the
consumer premises within permissible limits (±6%).
When aggregated, loads have two power components; the active
and reactive power. In addition to the consumer loads, the lines also
require reactive power to establish the electric and magnetic fields.
This reactive power used by the line is referred to as the reactive
power losses and affect the voltage profile in a power system.
Transmission lines absorb and inject reactive power and the net
effect depends on line length and loading. For a heavily loaded line,
reactive power loss (absorption) is more dominant. Because of
reactive power losses increasing with the length of transmission
lines, reactive power should not be transmitted over long distances.
Unlike real power which requires suitable sites for generation and
therefore has to be transmitted to load centres, reactive power can
be generated at load connections. This study assessed the reactive
power requirement of the Kenyan transmission network so as to
enable the transmission of all available power from Seven Forks
hydro stations to the load centres.
Methods:
The method used to determine the required reactive power
compensation and the buses to be compensated was power system
simulation. To enable power system simulation, a single line
diagram model of the transmission network was prepared using data
collected from the utility. Four scenarios were investigated by load
flow analysis.
i.
Case one was the base case where the system was running at
a peak load of 989 MW with an emergency generator in
service. The emergency power plant (EPP) was generating
61.4 MW in the network at Embakasi/Nairobi.
ii.
In case two, the system was running at the same peak load
(989 MW) with emergency plant generation (61.4 MW)
replaced with generation from Seven Forks hydro complex.
The hydrology was good and also the reserves in the seven
forks complex were confirmed adequate to produce the
required power.
iii.
In case three the system was at peak load (989 MW) without
emergency generation, with compensation introduced in
nine selected buses. The reactive power compensation was
provided using the synchronous condenser method. The
synchronous condensers were introduced in the network
model at the nine identified buses.
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iv.
In case four, the system load demand was raised to 1047
MW which is a hypothetical demand created to study the
evacuation of the full capacity of the Seven Forks hydro
complex and the compensation required to achieve it.
The method used to assess the transfer capability improvement of
the transmission lines between Nairobi and Seven Forks Complex
was by comparison of line loading (in MVA) before compensation
(case two) and after compensation (case three). The difference was
computed as a percentage of the initial line loading (case 2). The
method used to assess the transmission line loss reduction was by
comparison of line system losses as obtained from the load flow
results before compensation (case two) and after compensation
(case three).The reduction was computed as a percentage of the
system losses in case two
Results:
The following results were obtained:
 The analysis of base case scenario revealed seven buses
experience low bus voltage (less than 0.95 pu) during peak period
and therefore voltage support is already needed at those buses.
The buses experiencing low voltage were: Kiganjo, Nanyuki,
Kisumu, Sondu, Chemosit, Tana and Thika.

When the emergency generator at Embakasi was replaced with
generation from Seven Forks hydro in case 2, voltages at 28
buses dropped below 0.95 pu limit and 14 generating units
reached their maximum reactive power limits a and therefore
could not support voltage any further. It was not possible to
evacuate the total available power from Seven Forks without
reactive power compensation in the transmission network.
 To transmit the maximum power available at Seven Forks (603
MW) without causing the low voltage situation, reactive power
compensation is required at the following ten buses:










Juja Road
Embakasi
Nairobi North
Ruaraka
Nanyuki
Kiganjo
Chemosit
Kisumu
Muhoroni
Thika
75 MVAr
90 MVAr
36 MVAr
36 MVAr
18 MVAr
18 MVAr
16 MVAr
12 MVAr
30 MVAr
10 MVAr
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
There was a significant real and reactive power loss reduction in
the transmission system. The reduction in real power losses was
by 29.4 % of the losses experienced before compensation while
the reactive power losses reduction was by 25.8 % of the reactive
power losses experienced before compensation.

The analysis of transmission line power transfer capability of the
four transmission lines connecting Nairobi and Seven Forks
indicate an improvement by 11.6%, 10.4%, 10.5%and 1.3% for
Kiambere-Embakasi 220 kV line, Kamburu-Dandora 220 kV
Line 1, Kamburu-Dandora 220 kV Line 2 and Kindaruma-Juja
Road 132 kV line respectfully.
The analysis of transmission line loss reduction indicates a
reduction by 29.4% in real power and 25.8% in reactive power
compared to losses before compensation (case 2).
The results of power flow analysis show that the emergency
plant can only be displaced with hydro power from the Seven
Forks if 331 MVAr is installed at nine locations identified in the
transmission network. In addition, the results show that to
evacuate 603 MW which is the anticipated effective capacity after
Kindaruma unit 3 and Karura plant are commissioned, 341
MVAr needs to be installed in the transmission system for
voltage support.
A financial analysis carried out at discount rates of 12%, 10%
and 8% using the Net Present Worth criterion indicate the
project is feasible at interest rates of 12%, 8% and 5% with a
positive value of over 12.5 billion shillings and a Payback Period
of less than one year in all the cases.



Conclusions:
Title
Researcher(s)
Background:

It is recommended that 341MVAr reactive power compensation
should be installed at ten identified buses in the transmission
network of the Kenyan power system to make it possible to transfer
all the available power from Seven Forks hydro complex during
favourable hydrology without causing low bus voltage in the
network.
Design and Simulation of a Fuzzy Logic Traffic Signal Controller
for a Signalized Intersection
Mwangi C.M, Kang‘ethe S.M , Nyakoe G.N
The road transportation system relies on the physical infrastructure
and the traffic management system. In recent years, private cars and
public vehicles in Nairobi indicates a steady increase at a rate of
over ten percent per annum which has resulted in perennial traffic
jam, especially during peak hours. This has resulted in the need to
consider viable options to make the road transport more efficient.
Improving the physical road infrastructure is one such measure.
This entails road expansion, introducing dual carriageways, and
replacing intersections and roundabouts with flyovers and is
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Methods:
Results:
currently being implemented on the main highways leading into the
Nairobi city. This measure requires a huge capital investment and
might not be tenable within the city centre where land for
expansion is not readily available, leaving us with the option of
improving the transport management system.
The City Council of Nairobi (CCN), the body mandated to control
and manage transport within city centre of Nairobi, is currently
using fixed-time controllers to control signal timing of traffic lights.
Basically, a fixed-time controller repeats fixed preset signal timings
derived from historical traffic patterns. However, during peak hours
traffic police are deployed to manage and control traffic on the
major roundabouts and intersections because the fixed-time
controller are incapable of handling huge volumes of traffic.
The traffic problem is a dynamic problem that requires a real-time
solution which the fixed-time controllers are incapable of delivering.
This research discusses the implementation of an adaptive
controller using fuzzy logic technology to control traffic lights.
Fuzzy logic technology allows the implementation of real-life rules
similar to the way humans would think. The system acquires realtime traffic data using sensors and uses this data to adjust the signal
phasing and signal timing settings in response to real- time traffic
demands. Software based on MATLAB has been developed to
simulate a signalized intersection in different traffic conditions.
Simulation modeling is an increasingly popular and effective tool
for analyzing a wide variety of dynamical problems which are not
amenable to study by other means. Specifically, simulation models
are mathematical/logical representations of real-world systems,
which take the form of software executed on a digital computer in
an experimental fashion.
The research presents a Simulation model of the Fuzzy Logic
Traffic signal controller using the MATLAB software. MATLAB
offers a good environment for ―rapid prototyping‖ as it provides a
stable environment for mathematical modeling together with a
number of libraries (toolboxes) implementing more evolved tasks.
It also provides users with easy methods for analysis of their results.
The development of Fuzzy Logic input and output parameters
membership functions and rules is implemented using the
Graphical User Interfaces (GUI) on MATLAB. The simulation
model has been developed using SIMULINK and SIMEVENTS
toolboxes as well as MATLAB workspace environment.
The performance of fuzzy and fixed-time signal controllers is
compared by simulating them in an isolated traffic intersection
model. The results of the simulation of the vehicles on each
approach are then illustrated figures for comparison. It is seen that
the number of vehicle queues in fixed-time controller are longer
than those of the fuzzy controller.
It is also seen that vehicles spend more time in an intersection using
fixed-time controller than the one using Fuzzy controller. Vehicles
using the intersection with fixed-time controller spend 13 minutes
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Conclusions:
more, on every hour spent on traffic jam, as compared to those on
the fuzzy logic controlled intersection. The fixed-time controller on
average serves 52 cars/min while the fuzzy controller serves
approximately 56 cars/min i.e. 4 extra cars every minute.
Moreover, it is seen that the sequence of fixed-time controller
follows the sequence of 1-2-3-4 representing the four approaches.
The phase sequence of the fuzzy controller is dictated upon by the
weight of each phase with the one with highest priority granted
green phase.
In this research, the traffic model and traffic controller are
developed using MATLAB software. To test the effectiveness of
fuzzy controller to control the traffic flow at an isolated
intersection, the MATLAB simulation has been done. The
comparison of the proposed controller with the fixed-time
controller has shown overall improvement, the fuzzy logic
controller shows improved performance when controlling traffic
flow.
The effectiveness of the fuzzy controller is superior because it is
able to adapt to the different traffic conditions. The fuzzy logic
controller model can be modified to suit any intersection by varying
the input membership functions which further increases the
suitability of this traffic control system. Based on the results
realized, implementing this project on all signalized and nonsignalized intersections can result in a lot of savings in terms of fuel,
time and reduce stress and pollution levels considerably
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3.0
Publications
Name of Lecturer / Authors:
Kanai .M Michael, John .N Nderu and Peterson .K. Hinga
Title of Publication:
Name of Journal:
Design and Analysis of Neural Fuzzy Based Buck Converter
Controller Optimized with Swarm Intelligence
This paper presents an application of Adaptive Neural Fuzzy
Inference System (ANFIS) controller for DC-DC (Buck) converter
optimized with swarm collective intelligence. First, an adaptive
Neuro-Fuzzy controller of the Buck converter is designed and
simulated using MATLAB/SIMULINK package; the ANFIS has
the advantage of expert knowledge of the Fuzzy inference system
and the learning capability of neural networks. Secondly, the ANFIS
is optimized by Particle Swarm optimization methodology.
Simulation results demonstrates that the designed ANFIS-Swarm
controller realize a good dynamic behavior of the Buck converter, a
perfect voltage tracking with smaller overshoot, steady state error
and short settling time as well as high robustness than those
obtained by traditional ANFIS controller.
Journal of Global Engineers and Technologist Review, GETview, .
Month and Year of Publication:
November 2011
Name of Lecturer / Authors:
Kanai .M Michael, John .N Nderu and Peterson .K. Hinga
Title of Publication:
Design and Analysis of Neural Fuzzy Controller for Improved
Power Quality in AC-DC Converters
This paper presents an application of Adaptive Neural Fuzzy
Inference System (ANFIS) controller for AC-DC converter in a
three phase Pulse Width Modulation (PWM) Three-Level AC-DC
converter system, often referred as Improved Power Quality
Converters (IPQC). Three-phase Three-level AC-DC converters
have been developed to a matured level with improved power
quality in terms of power-factor correction, reduced total harmonic
distortion at input ac mains, and regulated dc output. However, for
best performance, the controller parameters used must be tuned
according to the nature of the system – while the design is generic,
the parameters depend on the specific system. The parameters of
converter, which vary with the operating conditions of the system,
are adapted in order to maintain desirable response for output
voltage and power factor. A Neural Fuzzy system is employed in
order to obtain the controller parameters assuring improved
response at selected load and start-up. The Three-level AC-DC
converter controller is modeled in MATLAB environment. The
response of the developed controllers is compared to Proportional
Integral Differential (PID) controller. The developed method is
more proficient in improving the controller loop settling time, the
rising time and overshoot and hence the disturbances do not affect
Abstract:
Abstract:
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the performances of Three-Level AC-DC converter.
Name of Conference proceedings
Month and Year of Publication:
Name of Lecturer / Authors:
Kenya Society of Electrical and Electronics Engineers (KSEEE)
and Japan Society of Applied Electromagnetic and Mechanics
(JSAEM)
November 2011
Month and Year of Publication:
Clement, Karanja M. Peter, Mutiso J. Ndanu , Mutahi M. Gathiru ,
Kanai M. Michael
Obstacle Avoidance, Way-finding and Localization System for the
Visually Impaired Based on Wireless Sensor Networks
We propose to develop a hand-held device to perform
obstacle avoidance and way-finding by use of range finding
sensors. Using a micro-controller, the spatial map of the
immediate environment is presented to the user using vibrotactile feedback.
The localization system uses wireless sensor networks as a model.
The user will query for their location from these wireless sensor
devises (motes) installed as landmarks, each with a unique location
code. This code is wirelessly sent to the handheld for enunciation
for via auditory feedback. A network management system to allow
for easy management of the wireless network will be developed.
Various parametric data items that illustrate the status of the
network shall be collected and a User Interface (UI) developed that
can, at a glance, show the state of the network. To increase the
resolution of the localization scheme, we shall measure the
Received Signal Strength Index (RSSI) value for each response for a
location query, so as to only respond with the closest mote.
Kenya Society of Electrical and Electronics Engineers (KSEEE)
and Japan Society of Applied Electromagnetic and Mechanics
(JSAEM)
November 2011
Name of Lecturer / Authors:
Kanai .M Michael, John .N Nderu and Peterson .K. Hinga
Title of Publication:
Design and Analysis of Neural Fuzzy Based Buck Converter
Controller Optimized with Swarm Intelligence
This paper presents an application of Adaptive Neural Fuzzy
Inference System (ANFIS) controller for DC-DC (Buck) converter
optimized with swarm collective intelligence. First, an adaptive
Neuro-Fuzzy controller of the Buck converter is designed and
simulated using MATLAB/SIMULINK package; the ANFIS has
the advantage of expert knowledge of the Fuzzy inference system
and the learning capability of neural networks. Secondly, the ANFIS
is optimized by Particle Swarm optimization methodology.
Simulation results demonstrates that the designed ANFIS-Swarm
controller realize a good dynamic behavior of the Buck converter, a
perfect voltage tracking with smaller overshoot, steady state error
and short settling time as well as high robustness than those
Title of Publication:
Abstract:
Name of Conference proceedings
Abstract:
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Name of Conference proceedings
Month and Year of Publication:
obtained by traditional ANFIS controller.
9th international Conference on Power System Operation and
Planning (ICPSOP)
January 2012
Name of Lecturer / Authors:
Title of Publication:
C. M. Muriithi, L. M. Ngoo and G. N. Nyakoe
Investigating The Impact Of Power System Stabilizers In A Multi
Machine System With An Induction Motor Load
Abstract:
The high reactive power demand by the induction motor load
during fault condition due to reduced bus voltages may cause a
generator to behave like a voltage source behind the synchronous
reactance and its terminal voltage reduces leading to the possibility
of a voltage collapse scenario. For reliability of these systems, and
in an attempt to reduce system oscillations, Power System
Stabilizers (PSS) have used to add damping by controlling the
excitation system. Studies on a SMIB and those using static loads
have shown that a well-tuned PSS using a Fuzzy Logic Controller
(FLPSS) can effectively improve power system dynamic stability.
This paper investigates the impact of the FLPSS in maintaining
voltage stability in a system with induction motor loads. A large
induction motor is introduced as a load in a multi machine system,
and the impact of the FLPSS are investigated by introducing a
temporary three phase fault. For comparison the FLPSS is
compared to other PSS found in literature. Results indicate that the
FLPSS may lead the generator to lose its capability to maintain
constant voltage and hence lead to the stalling of the induction
motor load soon after the fault is cleared.
Name of Conference Proceedings
Month and Year of Publication:
IEEE AFRICON 2011, Livingstone, Zambia
September 2011
Name of Lecturer / Authors:
Title of Publication:
J.K. Muriuki, C. M. Muriithi,D.K Murage
Study of accuracy of small-scale and large-scale induction motors
aggregation in a power system
Abstract:
Aggregation of different sizes of induction motors (IM) connected
to a power system has diverse precision on the identification of the
aggregate model parameters. Earlier work on the aggregation of
various motors sizes has not been extensive to identify their accuracy
on the identification of the model parameters. Also IM loads forms
the highest component in power system load. Therefore, the paper
proposes to investigate the accuracy of the aggregate model
parameters of a group of IM of different sizes and validate the
results by comparing with the individual induction motor
parameters. The simulations and the analysis are carried out using
Matlab/Simulink-based software package. The performance of the
developed model show that, small-scale induction motors gives
better accuracy of the aggregate motor parameter when compared
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with the individual motors parameters. It is found that the proposed
small-scale aggregation model gives acceptably accurate results than
the large-scale aggregation model.
Name of Conference Proceedings:
Month and Year of Publication:
6th JKUAT Annual Scientific Technological and Industrialization
Conference Year 2011
November 2011
Name of Lecturer / Authors:
Title of Publication:
Abstract:
Obiri L.K , Kinyua J. M, Mureithi C. M
Short term voltage stability analysis of an aggregated industrial load
Environmental constraints have limited expansion of transmission
line networks. And with power systems being operated close to their
security limits, the likelihood of voltage collapses occurring has
increased [1].
In most industries, the induction motor forms about 50% of the
total electric load and this call for a thorough analysis of their effects
on the whole power system [2].After a disturbance, stalling can occur
if the electrical torque does not overcome the mechanical load,
causing further voltage drop and eventually voltage collapse [3].
An aggregate motor model is simulated in MATLAB-SIMULINK. If
a three phase fault is not cleared in time, the motor will decelerate
continuously and eventually stall.
Name of Conference Proceedings
6th JKUAT Annual Scientific Technological and Industrialization
Conference Year 2011.
Month and Year of Publication:
November 2011
Name of Lecturer / Authors:
Kinyua J. M, Mureithi C. M , Murage D. K. , L.Obiri
Title of Publication:
Comparison of aggregation methods of induction motor models
for transient stability load modeling
This paper focusses on the comparison of the aggregation methods
of multiple induction motors (IM) connected in parallel on the same
bus into a single equivalent model using the no-load and lockedrotor and transformer method. The opearation for the former
method is based on assumptions that in the no-load operating
condition, the slips of all the IM are equal to zero while for the
locked-rotor, the slips are unity. The latter method assumes that all
the motors are represented by the transformer equivalent circuit
model and thus the name transformer method. This study has been
necessitated by the strong effects that the non-linear loads have on
power system characteristics and therefore erroneous modeling of
these devices continues to be an area of greater uncertainty.
Abstract:
Though various methods of aggregations have been used,
comparison on their suitablity and accuracy has not been extensively
explored. Appropriate dynamic load model aggregation reduces the
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computation time and provides a faster and efficient model
derivation and parameters identification that are most sensitive to
load dynamics. The simulations and analysis are carried out using
Simulink. The performance is validated by evaluating the results
obtained from individual and aggregate IM on IEEE 16 Bus
standard system found in literature. The transient characteristics due
to voltage disturbances of the aggregate IM and that of original IM
group are simulated and compared to check the effectiveness of the
aggrgation methods. The results shows that aggregation based on the
formrer method is accurate than aggregation based on the latter
method and can be used in modeling of large motors in any complex
power system because of its high accuracy
Name of Conference Proceedings:
9th International Conference On Power System Operation and
Planning (ICPSOP-2012) –JKUAT
Month and Year of Publication:
Name of Lecturer / Authors:
Title of Publication:
January 2012
J.K. Muriuki, C. M. Muriithi,D.K Murage, Irungu G.K.
Study of accuracy of small-scale and large-scale induction motors
aggregation in a power system
Abstract:
Aggregation of different sizes of induction motors (IM) connected
to a power system has diverse precision on the identification of the
aggregate model parameters. Earlier work on the aggregation of
various motors sizes has not been extensive to identify their accuracy
on the identification of the model parameters. Also IM loads forms
the highest component in power system load. Therefore, the paper
proposes to investigate the accuracy of the aggregate model
parameters of a group of IM of different sizes and validate the
results by comparing with the individual induction motor
parameters. The simulations and the analysis are carried out using
Matlab/Simulink-based software package. The performance of the
developed model show that, small-scale induction motors gives
better accuracy of the aggregate motor parameter when compared
with the individual motors parameters. It is found that the proposed
small-scale aggregation model gives acceptably accurate results than
the large-scale aggregation model.
Name of Conference Proceedings:
Year of Publication:
6th JKUAT Annual Scientific Technological and Industrialization
Conference Year 2011.
November 2011
Name of Lecturer / Authors:
Obiri L.K , Kinyua J. M, Mureithi C. M
Title of Publication:
Suitability of aggregation methods of induction motor models for
transient stability load modeling of kenya power transmission and
distribution system
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Abstract:
Current trend indicate that there has been increase on power outage
frequency. This has partly been as a result of unstable power system
with very small security margins of operation. Therefore, this paper
focusses on the voltage stability of aggregation of multiple induction
motors (IM) connected in parallel on the same bus of a power
system into a single equivalent model using two methods of
aggregations.This has been necessitated by the strong effects that the
non linear loads have on power system characteristics and therefore
erroneous modeling of these devices continues to be an area of
greater uncertainty and may cause voltage instability. Though various
methods of aggregations have been used, comparison on their
suitablity and accuracy has not been extensively explored.
Appropriate dynamic load model aggregation reduces the
computation time and provides a faster and efficient model
derivation and parameters identification that are most sensitive to
load dynamics. The simulations and analysis are carried out using
MATLAB/SIMULINK.The accuracy of these methods is compared
to identify the most suitable parameters aggregation method of IM
model. Their performance is validated by evaluating the results
obtained from industrial and standard individual IM and the
aggregation model on IEEE 16 Bus standard system found in
literature. Further, the transient characteristics due to voltage
disturbances of the aggregate IM and that of original IM group are
simulated and compared to check the effectiveness of the aggrgation
methods on power system. The results obtained are suitable and
practical.
Name of Conference Proceedings:
Month and Year of Publication:
The 2nd Distribution Conference For Kenya Power
January 2012
Name of Lecturer / Authors:
J.K. Muriuki, C. M. Muriithi,D.K Murage
Title of Publication:
Powerfactory Load Flow Sensitivity Analysis of an Induction Motor
Load Model
Abstract:
PowerFacotry Load flow sensitivity is a method used to obtain
certain relationship between dependent and independent variables
using differential relationship among physical measure in systems.
Voltage sensitivity analysis is based on the linearization of the
system around the operational point resulting from a load flow
calculation. Inappropriate load representation has been a major
setback causing inaccurate simulation results of the dynamic load.
Further, induction motor loads comprise of 60% power system
loads whose understanding under various dynamics is crucial for
system stability. Static loads are known to be imprecise in dynamic
load simulation and therefore yield false information on the system
stability. This paper presents a dynamic load model whose
parameters are varied to investigate their effects on both active and
reactive load dynamics. Load modeling using field measurement
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data from power quality meter of an industrial consumer and that of
standard motor models are analyzed to assess their effects on
sensitivity of the system stability. Load flow sensitivity is analyzed to
perform a voltage sensitivity analysis based on the linearization of
the system around the operational point that results from a load
flow calculation. The efficiency of the system is estimated using the
IEEE 9 bus system. The result indicates that load model parameters
have different sensitivity values under voltage disturbance. The
results acquired are thus acceptable and rational.
Name of journal :
International Conference On Advances In Technology And SocioEconomic Development May (Atsed 2011)-Eldoret Polytechnic,
ISSN 2223-9227
Month and Year of Publication:
May 2011
Name of Lecturer / Authors:
J.K. Muriuki, C. M. Muriithi, D.K Murage
Title of Publication:
Suitability of aggregation methods of induction motor models for
voltage stability analysis
Abstract:
Name of journal :
This paper focusses on the aggregation of multiple induction
motors (IM) connected in parallel on the same bus into a single
equivalent model using aggregation based on transfomer equivalentcircuit (method 1) and on no-load and locked rotor (method 2).This
has been necessitated by the strong effects that the non linear loads
have on power system characteristics and therefore erroneous
modeling of these devices continues to be an area of greater
uncertainty. Though various methods of aggregations have been
used, comparison on their suitablity and accuracy has not been
extensively explored.
Also investigated is the suitability of multi-band power system
stabilizer ( MB-PSS) on the aggregate motor under a fault.The
accuracy of these methods is compared to dentify the most
appropriate. Their performance is validated by evaluating the results
obtained from individual and aggregate IM on IEEE 16 Bus test
system. The results shows that method 2 is accurate than method 1
in identification of the motor parameters both under steady-state
and under fault condition. The MB-PSS gives better damping of the
oscillatory modes with method 2 than method 1. The former
method can therefore be used for accurate analysis of voltage
stability in a complex power system.
Key words: Aggregation methods, induction motor, voltage
stability, power system stabilizers
GETview. Year 2012, ISSN 2231-9700,
Month and Year of Publication:
February 2012
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Name of Lecturer / Authors
Title of Publication:
Abstract:
Month and Year of Publication:
George K Irungu, Stanley I. Kamau
Evolution of the Deregulated Kenyan Electricity Market
Electricity is an essential stimulant of economic growth and
household comfort in every country all over the world. Consumers
of electricity today regarded it as an essential commodity rather than
a service. In the last two decades, electricity markets have evolved
from closed markets with few participants to open markets with
many players. Electricity today in advanced deregulated market is
traded in open electricity market on day ahead basis. A good
number of countries in the developing world have deregulated their
electricity markets. Kenyan electricity market saw the onset of
deregulation in 1997 when generation was unbundled from
transmission and distribution. This resulted into the formation of
generation utility Kenya Electricity Generation Company (KenGen)
and transmission and distribution utility Kenya Power & Lighting
Company (KPLC).
This paper presents the evolution of the Kenyan electricity market
before the onset of deregulation 1908 to 1997 and the progressive
history of deregulation of Kenyan electricity markets from 1997 to
date. It highlights the motivation behind deregulation, the merits
and demerits. It pinpoints out the challenges facing deregulation in
Kenya and possibly the way forward.
Proceeding of the International Conference on power Systems
Operation and planning (IX ICPSOP) 2012 (16TH to 19TH January
2012 in JKUAT, pages 153-159)
January 2012
Name of Lecturer / Authors:
George K Irungu, Stanley I. Kamau
Title of Publication:
General Outlook of the Deregulated Electricity Market in Kenya
Abstract:
Electricity is an essential ingredient of economic growth and
household comfort in any country allover the world. Worldwide
electricity nowadays is regarded as a commodity rather than a
service. In the last two decades, electricity markets have evolved
from closed market with few participants to an open market with
many players. Electricity today in advanced deregulated market is
traded in open electricity market just like any other commodity in
normal market or stocks in a stock market. A good number of
countries have deregulated their electricity markets. Kenyan
electricity market saw the onset of deregulation in 1997 when
generation was unbundled from transmission and distribution. This
resulted into the formation of generation utility Kenya Electricity
Generation Company (KenGen) and transmission and distribution
utility Kenya Power & Lighting Company (KPLC).
Name of Conference Proceedings:
This paper starts by giving the worldwide perspective of
deregulation, then the reasons, successes and failures of
deregulation in the countries of Argentine, Spain, California State
(USA) and Norway. It then gives brief review of how the regulated
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Kenyan electricity sector started in 1908 and progressed to 1997.
Finally, the paper presents the progressive history of deregulation of
Kenyan electricity markets from 1997 to date. It highlights the
motivation behind deregulation, the merits and demerits. It
pinpoints out the challenges facing deregulation in Kenya and
possibly the way forward.
Name of Conference Proceedings:
Month and Year of Publication:
Proceedings of the 2nd International Conference for Mechanical
and Industrial Engineering Conference, held in Arusha, Tanzania
from 16th to 17th February 2012
February 2012
Name of Lecturer / Authors:
Muiga Rugara, D. O. Konditi, S. Musyoki
Title of Publication:
Closed-Loop Transmit Diversity for Mitigation of Interference and
Multipath Fading in Wireless Communication Systems
Abstract:
Name of Journal
:
The wireless communication Channel suffers from many
impairments such as the thermal noise often modeled as Additive
White Gaussian Noise (AWGN), the path loss in power as the radio
signal propagates, the shadowing due to the presence of fixed
obstacles in the radio path, and the fading which combines the
effects of multiple propagation paths and the rapid movement of
mobile units reflectors. Deploying multiple antennas at the
transmitter has been shown to increase diversity and therefore
improve signal quality with increase throughput. This paper
proposes a transmit diversity scheme, where multiple transmit
antennas are used at the transmitter. A feedback path is provided
from the receiver to communicate the channel seen by the receiver
to the transmitter (closed-loop). When closed-loop transmit
diversity is applied, the symbol from each transmit antenna is
multiplied with a complex number corresponding to the inverse of
the phase of the channel so as to ensure that the signals add
constructively at the receiver. From this research it was found that
sending the same information on multiple transmit antenna does
not always provide diversity gain. However if the transmitted
symbols are multiplied by a complex phase to ensure that the
phases align at the receiver, there is diversity gain though the bit
error rate performance seems to be slightly poorer than the
maximal ratio combining case.
Journal of Agriculture, Science and Technology (JAST)
JAGST, Volume 13(2) 2011
Year
Name of Lecturer / Authors:
2011
Musyimi P. M, Chege S. N , Wamoni M.
Title of Publication:
Microcontroller based hybrid energy management system
Abstract:
For a community to raise itself out of subsistence and into an
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upward spiral of increased prosperity, certain basic services must be
available and affordable. These include drinkable water, health care,
education, transportation and communication. Access to reliable
electricity is a pre-condition for the provision of many of these
services and an active catalyst for sustainable development. As such,
there has been an increase in demand for power that has resulted in
increased advancement in power systems that aim at optimizing the
energy sources available at ones disposal. Researchers have focused
their efforts on improving power generation methods. Another
alternative would be to develop an efficient energy management
system that optimizes the already available power.
This project aims at providing power to loads at a terminal voltage
of 240V AC. It will involve combining different power sources e.g.
include solar and wind in addition to mains supply. The 12V dc will
be stepped up using DC-DC converter. An inverter will then invert
this voltage to produce a 240V r.m.s. A microcontroller will be used
to control switches between different sources depending on load
requirements and also the capability of the sources to supply the
required power.
The microcontroller will ensure that priority is given to the
renewable energy sources and hence the mains power will only be
switched on as a last resort. This reduces reliance on mains supply
and consequently, cost reduction. A comparator will compare
output and input currents to produce a control signal for the
microcontroller. The output of the comparator will be used as an
input to the microcontroller for control purposes so as to produce
the pulses for switching the power sources accordingly.
Name of Conference Proceedings:
International conference on power systems operation and planning
(ICPSOP) forum 2012
Month and Year of Publication:
January 2012
Name of Lecturer / Authors:
A. Muhia, J. N. Nderu, P. K. Kihato and C. K. Kitur
Title of Publication:
Performance of Magnetostrictive Amorphous Wire Sensor in Motor
Speed Measurement
Abstract
This paper presents the performance analysis of magnetostrictive
amorphous wire in motor speed measurement. The principle of the
operation of the sensor is based on Large Barkhausen Jump, a
unique feature of the wire. The performance of the sensor is
compared with conventional speed measurement methods through
an experimental approach. A dc motor is used due to the linear
relationship that exists between applied voltage and speed. The
supply voltage for the dc motor is varied and motor speed
measured using a digital tachometer. The frequency of the signal
obtained from the magnetostrictive amorphous wire sensor is
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measured using an oscilloscope and the motor speed calculated
from this frequency. Results obtained show quite good agreement
in the speed measured by amorphous wire and that of the
tachometer.
Month and Year of Publication:
Index Terms- Magnetostrictive Amorphous wire, Large Barkhausen
Jump, speed, dc motor
Kenya Society of Electrical and Electronics Engineers (KSEEE)
and Japan Society of Applied Electromagnetic and Mechanics
(JSAEM)
November 2011
Name of Lecturer / Authors:
J. N. Nderu , A. M. Muhia, P.K. Kihato and C. K. Kitur
Title of Publication:
Microcontroller Based Amorphous Wire Motor Speed Sensor
Abstract:
This paper presents a microcontroller based motor speed sensing
approach using magnetostrictive amorphous wire. The principle
operation of the sensor is based on Large Barkhausen Jump, a
unique feature of the wire. The wire generates stable voltage pulses
in alternating fields. These pulses correlate well with the rotary
speed of the motor hence can be used to measure the speed of the
motor. The pulses are signal conditioned and fed into a
microcontroller for measurement of frequency. The speed of the
motor is calculated from this frequency. A graphic user interface is
designed where the frequency and the speed of the motor is
observed on a personal computer. The design presents a motor
speed sensing mechanism with desirable accuracy.
Name of Conference Proceedings:
Index Terms—Large Barkhausen Jump (LBJ), Magnetostrictive
Amorphous Wire, Microcontroller, Speed sensor
Name of Conference Proceedings
Month and Year of Publication:
2012 Mechanical Engineering Annual Conference on Sustainable
Research And Innovation
May 2012
Name of Lecturer / Authors:
A.M. Muhia, J. N. Nderu, P.K. Kihato and C. K. Kitur
Title of Publication
Effect of Length and Position Relative to the Rotor of
Magnetostrictive Amorphous Wire in Motor Speed Sensing
Abstract
The performance of the magnetostrictive amorphous wire in motor
speed sensing has been shown to match that of conventional motor
speed sensors. The sensor is based on Large Barkhausen Jump, a
unique feature of the wire, which occurs at a given critical length of
the wire. A permanent magnet is also used and therefore depending
on the strength of the magnet used, the position of the sensor
relative to the rotor is expected to influence the results. This paper
presents experimental results on the influence of length and
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position of the magnetostrictive amorphous wire on the
performance of the sensor. A close observation on the signal
waveforms indicates that there is a critical length and optimal
positioning of the wire from the magnet for which the performance
of the sensor is satisfactory.
Index Terms—Length, Magnetostrictive Amorphous Wire,
Position, Speed sensing
Name of Conference Proceedings:
Month and Year of Publication
Name of Lecturer / Authors:
2012 Mechanical Engineering Annual Conference on Sustainable
Research And Innovation
May 2012
C. K. Kitur, J. N. Nderu, K. Kaberere and A. M. Muhia
Title of Publication
Frequency Sensing of an Isolated Pico Hydro Power Generation
Plant Using Magnetostrictive Amorphous Wire
Abstract:
This paper presents frequency measurement of uncontrolled turbine
Isolated Pico hydro power generating plant using Magnetostrictive
amorphous wire (MAW). The basic principle of the measurement is
based on Large Barkhausen Jump (LBJ), a sudden reversal of
magnetization when the magnetic field reverses resulting in voltage
spikes being induced; a pick-up coil is wound around the MAW to
pick the spikes. The number of spikes recorded per second is
actually the frequency of generation. This is compared with the
measured frequency of the generated power as read from the
generation meters and also as calculated based on measured speed
of rotation and results are presented.
Name of Conference Proceedings:
Month and Year of Publication
Name of Lecturer / Authors:
2012 Mechanical Engineering Annual Conference on Sustainable
Research And Innovation
May 2012
Peter Kamita Kihato, John Ndichu Nderu
Title of Publication:
Direct Neuro-Fuzzy Approach to Motion Tuning of Servomotors
Abstract
Servomotors (Servos) have in the current technological advisements
played an important role in motion control. This has been made
possible by both the computational ability available and the ability
to have microchips that can be designated for a particular task.
This paper presents a direct approach to motion tuning control
where models for fuzzy controllability are not borrowed from other
software like MATLAB. A fuzzy controller is designed to directly
interface to the drive circuit of the servomotor. This simple and
novel approach not only simplifies the overall controller but also
manages to give a better control tuning on an already existing
controller of a servomotor thereby reducing the inherent error left
for a particular servo due to cost of manufacture. The motion
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Month and Year of Publication:
responses of fuzzy controlled servos to a robot arm manipulator
were verified through experiments.
Keywords: Servomotor, Fuzzy modeling, Position captures, Neural
topology.
Kenya Society of Electrical and Electronics Engineers (KSEEE)
and Japan Society of Applied Electromagnetic and Mechanics
(JSAEM)
November 2011
Name of Lecturer / Authors:
Charles Ndung’u, J. Nderu, L. Ngoo
Title of Publication:
Power Distribution Efficiency Based On Reactive Power and
Power Factor
Abstract:
This paper discusses the power factor of transmission and
distribution lines for selected power utility (Kenya Power)
substations. The choice of selection of lines was based on the
nature of the load (domestic, industrial or hybrid) and the status of
the loading (slightly, moderate or heavily loaded). Instantaneous
Power Factor (IPF) was read on energy meters at specific time of
the day for a period of two weeks. The data collected and analyzed
revealed that some feeder lines at most of substations are
distributing active power at low power factor below the grid
threshold limit of 0.90. Feeder lines mainly supplying domestic
loads have their power factor generally low, which could be
contributed to insufficient VAr compensation and proliferation of
non-linear loads. On the other hand, it was found that feeder lines
supplying industrial loads have power factor well above the
statutory limit, which is attributed to reactive power being
compensated in the vicinity of the demand (point of common
coupling). It is concluded that it is imperative to compensate the
reactive current on feeder lines supplying mainly domestic loads in
the vicinity of the loads i.e. near the distribution transformers to
improve the power factor of these feeder lines in order to increase
distribution efficiency and improve the voltage profile.
Name of journal:
Journal of Technology & Socio Economical Development Vol. 1
No. 1. ISSN 2223-9227
Month and Year of Publication:
September 2011
Name of Lecturer / Authors:
Charles Ndung’u, J. Nderu, L. Ngoo
Title of Publication:
Impact of Compact Fluorescent Lighting Bulbs on Power Quality
Abstract:
In recent time, the power quality has attracted a lot of attention due
to extensive emphasis by power utility on the power system
efficiency and end users awareness of power quality issues. This has
occurred mainly due to the sensitivity of the modern equipment and
Name of Conference Proceedings
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the deregulation of the power distribution. In addition, there are
usually massive losses both to power utility and end users due to
poor power quality supplies which fall below the set standards.
Power quality primarily consists of voltage dip/ swell, power system
interruptions (power outage), harmonic distortions, voltage flickers
and frequency deviations. This study looks at effect of CFL bulbs
on power system in relation to harmonic distortions and low power
factor inherently associated by CFL. It has established that the
bulbs generate substantial harmonic distortions and leading a power
factor. Mixing of incandescent and CFL bulbs in one circuit was
noted to improves the power quality at the point of common
coupling.
Name of Conference:
Kenya Society of Electrical Electronic Engineers 2011 International
Engineering Conference
Month and Year of Publication:
November 2011
Name of Lecturer / Authors:
Charles Ndung’u, J. Nderu, L. Ngoo
Title of Publication:
Analysis of Harmonic Levels at Power Lines to Improve Power
Quality
Abstract:
This paper presents the results of investigation done to
establishment of harmonic levels at various points of power utility
lines. It involved collection of harmonic order levels from
generation, distribution and point of common coupling (PCC). The
harmonic levels data of different power stations, substations and
large power consumers were collected. The analysis has ascertained
that large power consumers supplied on low voltage (415V) have
their harmonics current levels far beyond the threshold limit as
recommended by the IEEE 519-1992, as compared with the power
consumers supplied above 11,000V. In addition, voltage distortions
on transmission lines were noted to be more severe vis-a -vis the
current distortions. This is presumed to be because low voltage
consumers feed the harmonics direct to the power line as opposed
to the medium and high voltage consumers, where most of the
harmonics are trapped by step down transformers at the consumer‘s
premises. It can be deduced that the most affected PCC with high
harmonic current distortion is low voltage supplied end users.
Name of journal:
Mechanical Engineering Annual Conference On Sustainable
Research And Innovation, ISSN 2079-6226 – JKUAT
Month and Year of Publication:
May 2011
Name of Lecturer / Authors:
Charles Ndung’u, J. Nderu, L. Ngoo
Title of Publication:
Compensation of Vars at Off Grid Power Generations Using Shunt
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Capacitors
Abstract:
This paper presents the significant of VAr compensation at
electricity distribution lines at off grid power generation by
installation of fixed shunt capacitors. The objectives are to reduce
the cost of energy per unit generated and improve the voltage at the
end users. Due to presence of numerous small power rating of non
linear and inductive loads, demands of reactive power are usually
high as it is uneconomical to compensate the reactive power at the
load points. The reactive currents required by these loads have to
pass through the generator windings, switchgears, transmission
cables and step-up transformers. This contributes to a substantial
power loss at the distribution lines and at the generators due to
additional current (reactive). The study has shown that by
compensating the reactive power at the distribution line, the power
losses will reduce substantially and the voltage profile at end user
will improve. Moreover, fuel consumed by the generator per kWh
will also reduce thus less thermo emission (green power) and low
the maintenance cost of the generators.
Name of Conference:
1st Information Communication Technology conference at
Multimedia Unversity College of Kenya
Month and Year of Publication:
December 2011
Name of Lecturer / Authors:
Charles Ndung’u, J. Nderu, L. Ngoo
Title of Publication:
Improvement of Active Power Distribution Effeciency By
Compensating Reactive Power at Substations
Abstract:
This paper discusses the power factor of transmission and
distribution feeder lines for assorted power utility substations. The
choice of lines was based on the nature of the load (domestic,
industrial or hybrid) and the magnitude of the load; slightly,
moderate or heavily loaded. Instantaneous Power Factor (IPF) was
read on energy meters at specific time of the day for a period of two
weeks. The data collected and analyzed revealed that most of feeder
lines at most of substations are distributing active power at
comparatively low PF sometimes below grid threshold limit of 0.90.
This could be contributed to proliferation of non-linear loads.
These non linear loads consist of electronic devices with switched
mode power supply converters such as TV‘s, computers/ laptops,
and printers. Also contributing to low power factor is Compact
Fluorescence Light (CFL) retrofitting the incandescent bulbs. This
results in high loss on transmission and distribution feeder lines and
poor voltage regulation. The analysis also reveals that feeder lines
supplying domestic load have their power factor generally low due
to dominance of non linear domestic loads. However, it was found
out that feeder lines supplying industrial loads have power factor
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well above the statutory limit which is attributed to reactive power
being compensated at the vicinity of the demand (point of common
coupling).
Name Conference:
2nd Distribution Conference For The Kenya Power- WhiteSand
Mombasa:
Month and Year of Publication:
January 2012
Name of Lecturer / Authors:
Nelson Muchiri Gachoki; Hinga P.K; Wanjii S.M; Kahiu S. N
Title of Publication:
A Review on Biogas, its Application is a Dual-Fuel on Diesel
Engines for Power Generation
Abstract:
Rising global challenges of energy generation, sustainability, cost,
environmental concerns among others have triggered immense
research on alternative energy sources and technologies in the
recent past. Such previous works includes research into use of
biogas as a substitute fuel in diesel engines.
This paper focuses on how biogas is generated from solid waste and
among other uses, is used for power generation, electrical energy is
generated from biogas and diesel, using dual fuel (DF) generator.
DF applications are considered to lower cost of operating
automobile engines and power generators. Furthermore this paper
focuses on reviewing alternative fuels techniques focusing on biogas properties and local potential, then on how to run internal
combustion engines on biogas fuel, previous applications, their
availability and costs. The paper also illustrates methods for
modification of ordinary engine to run on dual fuel, considering
their applications, performance and cost implication.
The findings of this work are of great importance in developing a
local mechanism that uses diesel as a pilot fuel and biogas as
substitute fuel. The findings also will help in identification of an
appropriate fuel regulation tool and in adapting the generation plant
for a beneficial use. This is to provide affordable alternative source
of electrical power to institutions, municipalities or in remote rural
2012 Mechanical Engineering Annual Conference on Sustainable
Research And Innovation
Name of Conference Proceedings:
Month and Year of Publication:
May , 2012
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