Abstract: Although there has been a growing interest in the
hybrid free-space optical link and radio frequency FSO/RF
communication system, the current literature is limited to results
obtained in moderate or cold environment. In this paper, using a soft
switching approach, we investigate the effect of weather
inhomogeneities on the strength of turbulence hence the channel
refractive index under Qatar harsh environment and their influence
on the hybrid FSO/RF availability. In this approach, either FSO/RF
or simultaneous or none of them can be active. Based on soft
switching approach and a finite state Markov Chain (FSMC) process,
we model the channel fading for the two links and derive a
mathematical expression for the outage probability of the hybrid
system. Then, we evaluate the behavior of the hybrid FSO/RF under
hazy and harsh weather. Results show that the FSO/RF soft switching
renders the system outage probability less than that of each link
individually. A soft switching algorithm is being implemented on
FPGAs using Raptor code interfaced to the two terminals of a
1Gbps/100 Mbps FSO/RF hybrid system, the first being implemented
in the region. Experimental results are compared to the above
simulation results.
Abstract: As per the statistical data, the Doubly-fed Induction
Generator (DFIG) based wind turbine with variable speed and
variable pitch control is the most common wind turbine in the
growing wind market. This machine is usually used on the grid
connected wind energy conversion system to satisfy grid code
requirements such as grid stability, Fault Ride Through (FRT), power
quality improvement, grid synchronization and power control etc.
Though the requirements are not fulfilled directly by the machine, the
control strategy is used in both the stator as well as rotor side along
with power electronic converters to fulfil the requirements stated
above. To satisfy the grid code requirements of wind turbine, usually
grid side converter is playing a major role. So in order to improve the
operation capacity of wind turbine under critical situation, the
intensive study of both machine side converter control and grid side
converter control is necessary In this paper DFIG is modeled using
power components as variables and the performance of the DFIG
system is analysed under grid voltage fluctuations. The voltage
fluctuations are made by lowering and raising the voltage values in
the utility grid intentionally for the purpose of simulation keeping in
view of different grid disturbances.
Abstract: This paper presents a novel algorithm for modeling
photovoltaic based distributed generators for the purpose of optimal
planning of distribution networks. The proposed algorithm utilizes
sequential Monte Carlo method in order to accurately consider the
stochastic nature of photovoltaic based distributed generators. The
proposed algorithm is implemented in MATLAB environment and
the results obtained are presented and discussed.
Abstract: This paper introduces a method to optimal design of a
hybrid Wind/Photovoltaic/Fuel cell generation system for a typical
domestic load that is not located near the electricity grid. In this
configuration the combination of a battery, an electrolyser, and a
hydrogen storage tank are used as the energy storage system. The aim
of this design is minimization of overall cost of generation scheme
over 20 years of operation. The Matlab/Simulink is applied for
choosing the appropriate structure and the optimization of system
sizing. A teaching learning based optimization is used to optimize the
cost function. An overall power management strategy is designed for
the proposed system to manage power flows among the different
energy sources and the storage unit in the system. The results have
been analyzed in terms of technical and economic. The simulation
results indicate that the proposed hybrid system would be a feasible
solution for stand-alone applications at remote locations.
Abstract: In order to achieve high data rate and increase the
spectral efficiency, multiple input multiple output (MIMO) system has
been proposed. However, multiple antennas are limited by size and
cost. Therefore, recently developed cooperative diversity scheme,
which profits the transmit diversity only with the existing hardware by
constituting a virtual antenna array, can be a solution. However, most
of the introduced cooperative techniques have a common fault of
decreased transmission rate because the destination should receive the
decodable compositions of symbols from the source and the relay. In
this paper, we propose a cooperative cyclic delay diversity (CDD)
scheme that use hierarchical modulation. This scheme is free from the
rate loss and allows seamless cooperative communication.
Abstract: In this study, electric field distribution analyses for
three pylon models are carried out by a Finite Element Method
(FEM) based software. Analyses are performed in both stationary and
time domains to observe instantaneous values along with the
effective ones. Considering the results of the study, different line
geometries is considerably affecting the magnitude and distribution
of electric field although the line voltages are the same. Furthermore,
it is observed that maximum values of instantaneous electric field
obtained in time domain analysis are quite higher than the effective
ones in stationary mode. In consequence, electric field distribution
analyses should be individually made for each different line model
and the limit exposure values or distances to residential buildings
should be defined according to the results obtained.
Abstract: In this paper, monitoring and control of tap changer
mechanism of a transformer implementation in an Intelligent
Electronic Device (IED) is discussed. It has been a custom for
decades to provide a separate panel for on load tap changer control
for monitoring the tap position. However, this facility cannot either
record or transfer the information to remote control centers. As there
is a technology shift towards the smart grid protection and control
standards, the need for implementing remote control and monitoring
has necessitated the implementation of this feature in numerical
relays. This paper deals with the programming, settings and logic
implementation which is applicable to both IEC 61850 compatible
and non-compatible IEDs thereby eliminating the need for separate
tap changer control equipment. The monitoring mechanism has been
implemented in a 28MVA, 110 /6.9kV transformer with 16 tap
position with GE make T60 IED at Ultratech cement limited
Gulbarga, Karnataka and is in successful service.
Abstract: Main objective of this paper is to establish a link
between inertial forces of the bearings used in construction of wind
power plant and its behavior. Using bearings with lower inertial
forces has the immediate effect of decreasing inertia rotor system,
with significant results in increased energy efficiency, due to
decreased friction forces between rollers and raceways. The F.E.M.
analysis shows the appearance of uniform contact stress at the ends of
the rollers, demonstrated the necessity of production of low mass
bearings. Favorable results are expected in the economic field, by
reducing material consumption and by increasing the durability of
bearings. Using low mass bearings with hollow rollers instead of
solid rollers has an impact on working temperature, on vibrations and
noise which decrease. Implementation of types of hollow rollers of
cylindrical tubular type, instead of expensive rollers with logarithmic
profile, will bring significant inertial forces decrease with large
benefits in behavior of wind power plant.
Abstract: In insulation and cooling of power transformers
various liquids are used. Mineral oils have wide availability and low
cost. However, they have a poor biodegradability potential and lower
fire point in comparison with other insulating liquids. Use of a liquid
having high biodegradability is important due to environmental
consideration. This paper investigates edible corn oil as an alternative
to mineral oil. Various properties of mineral and corn oil like
breakdown voltage, dissipation factor, relative dielectric constant,
power loss and resistivity were measured according to different
standards.
Abstract: Efficient use of energy, the increase in demand of
energy and also with the reduction of natural energy sources, has
improved its importance in recent years. Most of the losses in the
system from electricity produced until the point of consumption is
mostly composed by the energy distribution system. In this study,
analysis of the resulting loss in power distribution transformer and
distribution power cable is realized which are most of the losses in
the distribution system. Transformer losses in the real distribution
system are analyzed by CYME Power Engineering Software
program. These losses are disclosed for different voltage levels and
different loading conditions.
Abstract: The recent interest in alternative and renewable
energy systems results in increased installed capacity ratio of such
systems in total energy production of the world. Specifically, Wind
Energy Conversion Systems (WECS) draw significant attention
among possible alternative energy options, recently. On the contrary
of the positive points of penetrating WECS in all over the world in
terms of environment protection, energy independence of the
countries, etc., there are significant problems to be solved for the grid
connection of large scale WECS. The reactive power regulation,
voltage variation suppression, etc. can be presented as major issues to
be considered in this regard. Thus, this paper evaluates the
application of a Static VAr Compensator (SVC) unit for the reactive
power regulation and operation continuity of WECS during a fault
condition. The system is modeled employing the IEEE 13 node test
system. Thus, it is possible to evaluate the system performance with
an overall grid simulation model close to real grid systems. The
overall simulation model is developed in
MATLAB/Simulink/SimPowerSystems® environments and the
obtained results effectively match the target of the provided study.
Abstract: As the Silicon oxide scaled down in MOSFET
technology to few nanometers, gate Direct Tunneling (DT) in
Floating gate (FGMOSFET) devices has become a major concern for
analog designers. FGMOSFET has been used in many low-voltage
and low-power applications, however, there is no accurate model that
account for DT gate leakage in nano-scale. This paper studied and
analyzed different simulation models for FGMOSFET using TSMC
90-nm technology. The simulation results for FGMOSFET cascade
current mirror shows the impact of DT on circuit performance in
terms of current and voltage without the need for fabrication. This
works shows the significance of using an accurate model for
FGMOSFET in nan-scale technologies.
Abstract: This paper introduces a boost converter with a new
active snubber cell. In this circuit, all of the semiconductor
components in the converter softly turns on and turns off with the
help of the active snubber cell. Compared to the other converters, the
proposed converter has advantages of size, number of components
and cost. The main feature of proposed converter is that the extra
voltage stresses do not occur on the main switches and main diodes.
Also, the current stress on the main switch is acceptable level.
Moreover, the proposed converter can operates under light load
conditions and wide input line voltage. In this study, the operating
principle of the proposed converter is presented and its operation is
verified with the Proteus simulation software for a 1 kW and 100 kHz
model.
Abstract: This article presents a vibration diagnostic method
designed for Permanent Magnets (PM) electrical machines–traction
motors and generators. Those machines are commonly used in traction
drives of electrical vehicles and small wind or water systems. The
described method is very innovative and unique. Specific structural
properties of machines excited by permanent magnets are used in this
method - electromotive force (EMF) generated due to vibrations. There
was analyzed number of publications, which describe vibration
diagnostic methods, and tests of electrical machines and there was no
method found to determine the technical condition of such machine
basing on their own signals. This work presents field-circuit model,
results of static tests, results of calculations and simulations.
Abstract: To tackle the air pollution issues, Plug-in Hybrid
Electric Vehicles (PHEVs) are proposed as an appropriate solution.
Charging a large amount of PHEV batteries, if not controlled, would
have negative impacts on the distribution system. The control process
of charging of these vehicles can be centralized in parking lots that
may provide a chance for better coordination than the individual
charging in houses. In this paper, an optimization-based approach is
proposed to determine the optimum PHEV parking capacities in
candidate nodes of the distribution system. In so doing, a profile for
charging and discharging of PHEVs is developed in order to flatten
the network load profile. Then, this profile is used in solving an
optimization problem to minimize the distribution system losses. The
outputs of the proposed method are the proper place for PHEV
parking lots and optimum capacity for each parking. The application
of the proposed method on the IEEE-34 node test feeder verifies the
effectiveness of the method.
Abstract: The MEMS pressure sensor has been introduced and
presented in this paper. The types of pressure sensor and its theory of
operation are also included. The latest MEMS technology, the
fabrication processes of pressure sensor are explored and discussed.
Besides, various device applications of pressure sensor such as tire
pressure-monitoring system, diesel particulate filter and others are
explained. Due to further miniaturization of the device nowadays, the
pressure sensor with nanotechnology (NEMS) is also reviewed. The
NEMS pressure sensor is expected to have better performance as well
as lower in its cost. It has gained an excellent popularity in many
applications.
Abstract: In this paper, we consider a cognitive relay network
(CRN) in which the primary receiver (PR) is protected by peak
transmit power ¯PST and/or peak interference power Q constraints.
In addition, the interference effect from the primary transmitter (PT)
is considered to show its impact on the performance of the CRN. We
investigate the outage probability (OP) and outage capacity (OC) of
the CRN by deriving closed-form expressions over Rayleigh fading
channel. Results show that both the OP and OC improve by increasing
the cooperative relay nodes as well as when the PT is far away from
the SR.
Abstract: The lifetime of a wireless sensor network can be
effectively increased by using scheduling operations. Once the
sensors are randomly deployed, the task at hand is to find the largest
number of disjoint sets of sensors such that every sensor set provides
complete coverage of the target area. At any instant, only one of these
disjoint sets is switched on, while all other are switched off. This
paper proposes a heuristic search method to find the maximum
number of disjoint sets that completely cover the region. A
population of randomly initialized members is made to explore the
solution space. A set of heuristics has been applied to guide the
members to a possible solution in their neighborhood. The heuristics
escalate the convergence of the algorithm. The best solution explored
by the population is recorded and is continuously updated. The
proposed algorithm has been tested for applications which require
sensing of multiple target points, referred to as point coverage
applications. Results show that the proposed algorithm outclasses the
existing algorithms. It always finds the optimum solution, and that
too by making fewer number of fitness function evaluations than the
existing approaches.
Abstract: Nanotechnology has become the world attention in
various applications including the solar cells devices due to the
uniqueness and benefits of achieving low cost and better
performances of devices. Recently, thin film solar cells such as
Cadmium Telluride (CdTe), Copper-Indium-Gallium-diSelenide
(CIGS), Copper-Zinc-Tin-Sulphide (CZTS), and Dye-Sensitized
Solar Cells (DSSC) enhanced by nanotechnology have attracted
much attention. Thus, a compilation of nanotechnology devices
giving the progress in the solar cells has been presented. It is much
related to nanoparticles or nanocrystallines, carbon nanotubes, and
nanowires or nanorods structures.
Abstract: In this paper, influence of harmonics on medium
voltage distribution system of Bogazici Electricity Distribution Inc.
(BEDAS) which takes place at Istanbul/Turkey is investigated. A ring
network consisting of residential loads is taken into account for this
study. Real system parameters and measurement results are used for
simulations. Also, probable working conditions of the system are
analyzed for 50%, 75%, and 100% loading of transformers with
similar harmonic contents. Results of the study are exhibited the
influence of nonlinear loads on %THDV, P.F. and technical losses of
the medium voltage distribution system.