Abstract: A new topology of unified power quality conditioner
(UPQC) is proposed for different power quality (PQ) improvement in
a three-phase four-wire (3P-4W) distribution system. For neutral
current mitigation, a star-hexagon transformer is connected in shunt
near the load along with three-leg voltage source inverters (VSIs)
based UPQC. For the mitigation of source neutral current, the uses of
passive elements are advantageous over the active compensation due
to ruggedness and less complexity of control. In addition to this, by
connecting a star-hexagon transformer for neutral current mitigation
the over all rating of the UPQC is reduced. The performance of the
proposed topology of 3P-4W UPQC is evaluated for power-factor
correction, load balancing, neutral current mitigation and mitigation
of voltage and currents harmonics. A simple control algorithm based
on Unit Vector Template (UVT) technique is used as a control
strategy of UPQC for mitigation of different PQ problems. In this
control scheme, the current/voltage control is applied over the
fundamental supply currents/voltages instead of fast changing APFs
currents/voltages, thereby reducing the computational delay.
Moreover, no extra control is required for neutral source current
compensation; hence the numbers of current sensors are reduced. The
performance of the proposed topology of UPQC is analyzed through
simulations results using MATLAB software with its Simulink and
Power System Block set toolboxes.
Abstract: Although lighting systems powered by Photovoltaic
(PV) cells have existed for many years, they are not widely used,
especially in lighting for buildings, due to their high initial cost and
low conversion efficiency. One of the technical challenges facing PV
powered lighting systems has been how to use dc power generated by
the PV module to energize common light sources that are designed to
operate efficiently under ac power. Usually, the efficiency of the dc
light sources is very poor compared to ac light sources. Rapid
developments in LED lighting systems have made this technology a
potential candidate for PV powered lighting systems. This study
analyzed the efficiency of each component of PV powered lighting
systems to identify optimum system configurations for different
applications.
Abstract: This work aims to reduce the read power consumption
as well as to enhance the stability of the SRAM cell during the read
operation. A new 10-transisor cell is proposed with a new read
scheme to minimize the power consumption within the memory core.
It has separate read and write ports, thus cell read stability is
significantly improved. A 16Kb SRAM macro operating at 1V
supply voltage is demonstrated in 65 nm CMOS process. Its read
power consumption is reduced to 24% of the conventional design.
The new cell also has lower leakage current due to its special bit-line
pre-charge scheme. As a result, it is suitable for low-power mobile
applications where power supply is restricted by the battery.
Abstract: This paper proposed a new CAD tools for microwave amplifier design. The proposed tool is based on survey about the broadband amplifier design methods, such as the Feedback amplifiers, balanced amplifiers and Compensated Matching Network The proposed tool is developed for broadband amplifier using a compensated matching network "unconditional stability amplifier". The developed program is based on analytical procedures with ability of smith chart explanation. The C# software is used for the proposed tools implementation. The program is applied on broadband amplifier as an example for testing. The designed amplifier is considered as a broadband amplifier at the range 300-700 MHz. The results are highly agreement with the expected results. Finally, these methods can be extended for wide band amplifier design.
Abstract: Carriers scattering in the inversion channel of n-
MOSFET dominates the drain current. This paper presents an effective
electron mobility model for the pocket implanted nano scale
n-MOSFET. The model is developed by using two linear pocket
profiles at the source and drain edges. The channel is divided into
three regions at source, drain and central part of the channel region.
The total number of inversion layer charges is found for these three
regions by numerical integration from source to drain ends and the
number of depletion layer charges is found by using the effective
doping concentration including pocket doping effects. These two
charges are then used to find the effective normal electric field,
which is used to find the effective mobility model incorporating the
three scattering mechanisms, such as, Coulomb, phonon and surface
roughness scatterings as well as the ballistic phenomena for the
pocket implanted nano-scale n-MOSFET. The simulation results show
that the derived mobility model produces the same results as found
in the literatures.
Abstract: This paper addresses the problem of forbidden states in
non safe Petri Nets. In the system, for preventing it from entering the
forbidden states, some linear constraints can be assigned to them.
Then these constraints can be enforced on the system using control
places. But when the number of constraints in the system is large, a
large number of control places must be added to the model of system.
This concept complicates the model of system. There are some
methods for reducing the number of constraints in safe Petri Nets.
But there is no a systematic method for non safe Petri Nets. In this
paper we propose a method for reducing the number of constraints in
non safe Petri Nets which is based on solving an integer linear
programming problem.
Abstract: The paper presents new results of a recent industry
supported research and development study in which an efficient
framework for evaluating practical and meaningful power system
reliability and quality indices was applied. The system-wide
integrated performance indices are capable of addressing and
revealing areas of deficiencies and bottlenecks as well as
redundancies in the composite generation-transmission-demand
structure of large-scale power grids. The technique utilizes a linear
programming formulation, which simulates practical operating
actions and offers a general and comprehensive framework to assess
the harmony and compatibility of generation, transmission and
demand in a power system. Practical applications to a reduced
system model as well as a portion of the Saudi power grid are also
presented in the paper for demonstration purposes.
Abstract: In this paper, we proposed a novel receiver algorithm
for coherent underwater acoustic communications. The proposed
receiver is composed of three parts: (1) Doppler tracking and
correction, (2) Time reversal channel estimation and combining, and
(3) Joint iterative equalization and decoding (JIED). To reduce
computational complexity and optimize the equalization algorithm,
Time reversal (TR) channel estimation and combining is adopted to
simplify multi-channel adaptive decision feedback equalizer (ADFE)
into single channel ADFE without reducing the system performance.
Simultaneously, the turbo theory is adopted to form joint iterative
ADFE and convolutional decoder (JIED). In JIED scheme, the ADFE
and decoder exchange soft information in an iterative manner, which
can enhance the equalizer performance using decoding gain. The
simulation results show that the proposed algorithm can reduce
computational complexity and improve the performance of equalizer.
Therefore, the performance of coherent underwater acoustic
communications can be improved greatly.
Abstract: This work is devoted to the calculation of the
undulatory parameters and the study of the influence thickness of
electrical sheet on overvoltage compared to the carcass and between
whorls (sections) of the asynchronous motors supplied with PWM
converters.
Abstract: In over deployed sensor networks, one approach
to Conserve energy is to keep only a small subset of sensors
active at Any instant. For the coverage problems, the monitoring
area in a set of points that require sensing, called demand points, and
consider that the node coverage area is a circle of range R, where R
is the sensing range, If the Distance between a demand point and
a sensor node is less than R, the node is able to cover this point. We
consider a wireless sensor network consisting of a set of sensors
deployed randomly. A point in the monitored area is covered if it is
within the sensing range of a sensor. In some applications, when the
network is sufficiently dense, area coverage can be approximated by
guaranteeing point coverage. In this case, all the points of wireless
devices could be used to represent the whole area, and the working
sensors are supposed to cover all the sensors. We also introduce
Hybrid Algorithm and challenges related to coverage in sensor
networks.
Abstract: In this paper the effect of faults in the elements and
parts of discrete event systems is investigated. In the occurrence of
faults, some states of the system must be changed and some of them
must be forbidden. For this goal, different states of these elements are
examined and a model for fail-safe behavior of each state is
introduced. Replacing new models of the target elements in the
preliminary model by a systematic method, leads to a fail-safe
discrete event system.
Abstract: This paper presented two new efficient algorithms
for contour approximation. The proposed algorithm is compared
with Ramer (good quality), Triangle (faster) and Trapezoid (fastest)
in this work; which are briefly described. Cartesian co-ordinates of
an input contour are processed in such a manner that finally
contours is presented by a set of selected vertices of the edge of the
contour. In the paper the main idea of the analyzed procedures for
contour compression is performed. For comparison, the mean
square error and signal-to-noise ratio criterions are used.
Computational time of analyzed methods is estimated depending on
a number of numerical operations. Experimental results are
obtained both in terms of image quality, compression ratios, and
speed. The main advantages of the analyzed algorithm is small
numbers of the arithmetic operations compared to the existing
algorithms.
Abstract: This paper reviews the optimization available
transmission capability (ATC) of power systems using a device of
FACTS named SSSC equipped with energy storage devices. So that,
emplacement and improvement of parameters of SSSC will be
illustrated. Thus, voltage magnitude constraints of network buses,
line transient stability constraints and voltage breakdown constraints
are considered. To help the calculations, a comprehensive program in
DELPHI is provided, which is able to simulate and trace the
parameters of SSSC has been installed on a specific line.
Furthermore, the provided program is able to compute ATC, TTC
and maximum value of their enhancement after using SSSC.
Abstract: With the rapid popularization of internet services, it is apparent that the next generation terrestrial communication systems must be capable of supporting various applications like voice, video, and data. This paper presents the performance evaluation of turbo- coded mobile terrestrial communication systems, which are capable of providing high quality services for delay sensitive (voice or video) and delay tolerant (text transmission) multimedia applications in urban and suburban areas. Different types of multimedia information require different service qualities, which are generally expressed in terms of a maximum acceptable bit-error-rate (BER) and maximum tolerable latency. The breakthrough discovery of turbo codes allows us to significantly reduce the probability of bit errors with feasible latency. In a turbo-coded system, a trade-off between latency and BER results from the choice of convolutional component codes, interleaver type and size, decoding algorithm, and the number of decoding iterations. This trade-off can be exploited for multimedia applications by using optimal and suboptimal performance parameter amalgamations to achieve different service qualities. The results are therefore proposing an adaptive framework for turbo-coded wireless multimedia communications which incorporate a set of performance parameters that achieve an appropriate set of service qualities, depending on the application's requirements.
Abstract: Wireless sensor networks include small nodes which
have sensing ability; calculation and connection extend themselves
everywhere soon. Such networks have source limitation on
connection, calculation and energy consumption. So, since the nodes
have limited energy in sensor networks, the optimized energy
consumption in these networks is of more importance and has created
many challenges. The previous works have shown that by organizing
the network nodes in a number of clusters, the energy consumption
could be reduced considerably. So the lifetime of the network would
be increased. In this paper, we used the Queen-bee algorithm to
create energy efficient clusters in wireless sensor networks. The
Queen-bee (QB) is similar to nature in that the queen-bee plays a
major role in reproduction process. The QB is simulated with J-sim
simulator. The results of the simulation showed that the clustering by
the QB algorithm decreases the energy consumption with regard to
the other existing algorithms and increases the lifetime of the
network.
Abstract: The aim of this paper is to explore the security issues
that significantly affect the performance of Mobile Adhoc Networks
(MANET)and limit the services provided to their intended users. The
MANETs are more vulnerable to Distributed Denial of Service
attacks (DDoS) because of their properties like shared medium,
dynamic topologies etc. A DDoS attack is a coordinated attempt
made by malicious users to flood the victim network with the large
amount of data such that the resources of the victim network are
exhausted resulting in the deterioration of the network performance.
This paper highlights the effects of different types of DDoS attacks
in MANETs and categorizes them according to their behavior.
Abstract: Distance protection of transmission lines including advanced flexible AC transmission system (FACTS) devices has been a very challenging task. FACTS devices of interest in this paper are static synchronous series compensators (SSSC) and unified power flow controller (UPFC). In this paper, a new algorithm is proposed to detect and classify the fault and identify the fault position in a transmission line with respect to a FACTS device placed in the midpoint of the transmission line. Discrete wavelet transformation and wavelet entropy calculations are used to analyze during fault current and voltage signals of the compensated transmission line. The proposed algorithm is very simple and accurate in fault detection and classification. A variety of fault cases and simulation results are introduced to show the effectiveness of such algorithm.
Abstract: The objective of this paper is to analyze the
performance of a double-sided axial flux permanent magnet
brushless DC (AFPM BLDC) motor with two-phase winding.
To study the motor operation, a mathematical dynamic model
has been proposed for motor, which became the basis for
simulations that were performed using MATLAB/SIMULINK
software package. The results of simulations were presented
in form of the waveforms of selected quantities and the
electromechanical characteristics performed by the motor. The
calculation results show that the two-phase motor version
develops smooth torque and reaches high efficiency. The twophase
motor can be applied where more smooth torque is
required. Finally a study on the influence of switching angle
on motor performance shows that when advance switching
technique is used, the motor operates with the highest
efficiency.
Abstract: This paper undertakes the problem of optimal
capacitor placement in a distribution system. The problem is how to
optimally determine the locations to install capacitors, the types and
sizes of capacitors to he installed and, during each load level,the
control settings of these capacitors in order that a desired objective
function is minimized while the load constraints,network constraints
and operational constraints (e.g. voltage profile) at different load
levels are satisfied. The problem is formulated as a combinatorial
optimization problem with a nondifferentiable objective function.
Four solution mythologies based on algorithms (GA),tabu search
(TS), and hybrid GA-SA algorithms are presented.The solution
methodologies are preceded by a sensitivity analysis to select the
candidate capacitor installation locations.
Abstract: Voltage flicker is a disturbance in electrical power
systems. The reason for this disturbance is mainly the large nonlinear
loads such as electric arc furnaces. Synchronous static
compensator (STATCOM) is considered as a proper technique to
mitigate the voltage flicker. Application of more suitable and precise
power electronic converter leads to a more precise performance of the
compensator. In this paper a three-level 12-pulse voltage source
inverter (VSI) with a 12-terminal transformer connected to the ac
system is studied and the obtained results are compared with the
performance of a STATCOM using a simple two-level VSI and an
optimal and more precise performance of the proposed scheme is
achieved.