|
Issue 1, Volume 4,
January 2009
Title of the Paper: Static and Dynamic
Analysis of Reconnection of Former Two UCTE Synchronous Zones
DOWNLOAD
FULL PDF
Authors: Ivica Toljan,
Eraldo Banovac, Sejid Tesnjak
Abstract: Considering the European electric power systems there is a yearly
increased consumption of electricity everywhere (from 1% to even 4% in some
cases). The processes of developing and connecting existing electric power
systems are very complex. Preconditions for connecting two UCTE synchronous
zones (1st and 2nd Pan-European synchronous zones) in one European electric
power system were created in 2000. The UCTE synchronous zones were formed when
the outage of the 400 kV overhead line Ernestinovo – Mladost on September 26,
1991 caused the system to separate. The reconnection was carried out on
October 10, 2004 following the important decision which was passed by the UCTE
Steering Committee at its meeting in early 2002 in Brussels. Static and
dynamic analysis with respect to reconnection of electric power systems, such
as transit analysis, analysis of capacity flows, short circuits, N-1, dynamic
behavior, angle analysis, voltage stabilities, frequency oscillations, changes
of capacity flows in a short time period, were outlined in the paper. Special
attention is paid to the mathematical base significant for carrying out the
analysis of conditions in certain electric power system.
Keywords: European
transmission system, Reconnection, Static and dynamic analysis, Synchronous
zone
Title of the Paper: A Novel Approach to
Evaluate Incremental Transmission Losses
DOWNLOAD
FULL PDF
Authors: P. M. De
Oliveira-De Jesus, M. A. Alvarez, M. T. Ponce de Leao, J. M. Yusta
Abstract: During the past thirty years, the evaluation of incremental losses
in transmission systems has been widespread around the world encompassing a
fundamental task in order to solve the well-known economic dispatch problem.
Nowadays, incremental losses or computation of penalty factors has gained a
new relevance allocating transmission losses among market participants being
integrated in the spot pricing model. Nevertheless, vagueness in power
injections from load demand and renewable resources has a fundamental
influence on transmission incremental losses, and consequently affecting spot
prices of the energy. This paper presents a new method to compute Incremental
Transmission Loss (ITL) factors taking into account the effect of uncertainty
on power injections due to measurement errors or future estimation. Fuzzy Set
Theory is applied to deal with vagueness of information about power
injections. The proposed technique provides a broad spectrum of feasibility of
incremental losses in order to perform operational planning tasks by
Transmission System Operators or network regulators. A 3-bus system is used to
illustrate the proposed methodology.
Keywords: Incremental
transmission loss factors, loss allocation, spot pricing
Title of the Paper: Problem Solving of
Partial Discharge on the Distribution Line
DOWNLOAD
FULL PDF
Authors: Narong Mungkung,
Tanes Tanitteerapan, Werachai Chaokumnerd, Karun Morasilp, Panumat Limsuwan,
Warawut Poolperm, Toshifumi Yuji
Abstract: This paper presents the mitigation methods of PD on PIC in
distribution line system. The area located near the coast will be selected as
the pilot project because of having strong occurrence of PD which is mainly
caused by salt contamination. The methods applied in this experiment consist
of using tie wires made from an insulation sheath of low voltage cable, the
sheath of PIC itself; composite tie wire and aluminium tie wire (reverse loop
binding). Following the trial results, there are two methods that considered
as the most effective ways for PD solving; binding PIC by using the PIC’s
insulation sheath and the composite tie wire instead of aluminium tie wire
(conventional binding).
Keywords: Partial
discharge, Partially Insulated Cable, Tie wire, Burn down, Mitigation
Title of the Paper: Voltage Stability
Enhancement of Low Voltage Radial Distribution Network Using Static VAR
Compensator: A Case Study
DOWNLOAD
FULL PDF
Authors: Kishor Porate,
K. L. Thakre, G. L. Bodhe
Abstract: In this paper power flow analysis of 33/11 kV distribution
substation and feeder is carried out to know the status of voltage and power
flow at each bus. To maintain the rated voltage at load end, low rated static
VAR compensators (SVC) are installed. For the case study typical heavily
loaded distribution substation where the voltage variation on all the buses
are maximum during peak load condition has been selected. Simulation of the
distribution network with SVC has been developed in the Electrical Transient
Analyzer Program (ETAP) environment. With the insertion of SVC, enhancement in
voltage at various buses, reduction in system power loss, improvement in power
factor and power flow are the objectives of the study. Description of the
study network, simulation model and the results of simulation with comparison
of recorded results are presented in the paper.
Keywords: Distribution
network, Voltage stability, Power flow Analysis, Static VAR compensator,
FACTS, ETAP
Issue 2, Volume 4,
February 2009
Title of the Paper: Applying Grey
Theory Prediction Model on the DGA Data of the Transformer Oil and Using it
for Fault Diagnosis
DOWNLOAD
FULL PDF
Authors: Anjali
Chatterjee, Nirmal Kumar Roy
Abstract: This Non-Destructive Evaluation of Power transformer by monitoring
various parameters, to predict its in-service behavior, is very much necessary
for operating engineer to avoid catastrophic failures and costly outages.
Dissolved Gas Analysis (DGA) is an important tool for transformer fault
diagnosis. It is observed that the results of DGA doesn’t have a perceivable
change over a short period. For less population of data availability grey
modeling is used. To apply probability theory, statistics, and fuzzy systems,
there is a requirement for a large number of data, then only conclusion or
some inference can be drawn. The advantage of using the grey system theory is
that, it gives a fair accuracy in predicting the volume of the gases, expected
to be generated after some time period, using a small sample of data. In this
paper we have done a comparative study on the predicted results obtained by
different model of Grey theory mainly whitened model, connotation model and
modified grey model. It is found that the error generated from the prediction
by all the three model are within the limit of 15% which is acceptable.
Additional by linear regression we are establishing a correlation between the
key gases. This helps us to detect the abnormality of the situation and
diagnose the type of fault. Additional this paper deals with the study on the
behavior of the gas dissolved in the oil which has undergone filtration and
the one without filtration. Through graphical means it has been clearly shown
that filtration at periodic interval will extend the life of the transformer.
It has been shown that the rate of gas generation also plays an important role
to detect an active fault.
Keywords: Transformer,
Dissolve gas analysis (DGA), Grey model, Modified grey model, Regression
theory, Correlation, Fault diagnosis, filtration
Title of the Paper: Security
Constrained Unit Commitment Problem with Operational, Power Flow and
Environmental Constraints
DOWNLOAD
FULL PDF
Authors: S. Prabhakar
Karthikeyan, K. Palanisamy, C. Rani, I. Jacob Raglend, D. P. Kothari
Abstract: An algorithm to solve unit commitment problem (UCP) with
operational, power flow and environmental constraints under contingencies has
been developed to plan an economic and secure generation schedule. The unit
commitment (UC) solution for the environmental constrained problem has been
formulated as a multi-objective problem by considering both Economic load
dispatch (ELD) and Economic emission dispatch (EED) simultaneously. The
combined economic emission dispatch (CEED) bi-objective problem is converted
to single objective function by adding a modified price penalty factor. The
UCP solutions without operational and power flow constraints are not practical
due to secure operation of the power system network. This proposed algorithm
introduces an efficient UC approach that obtains the minimum operating cost
satisfying both unit and network constraints when contingencies are included.
Repeated OPF for the satisfactory unit combinations for every line removal
under the given study period has been carried out to obtain UC solutions with
both operational, power flow and environmental constraints. This proposed
algorithm has been tested on IEEE 14, 30, 57, 118 buses and practical Indian
utility systems. The solutions obtained are quite encouraging and useful in
the economic emission environment. The algorithm and simulation are carried
through Matlab environment.
Keywords: Combined
economic emission dispatch, Contingency Analysis, Dynamic Programming,
Economic dispatch, Lagrangian multiplier, Newton Raphson, Optimal power flow,
Price penalty factor, Unit commitment
Title of the Paper: Comparison of
Electric Field and Potential Distributions on Silicone Rubber Polymer
Insulators under Clean and Various Contamination Conditions Using Finite
Element Method
DOWNLOAD
FULL PDF
Authors: Winai
Onchantuek, Boonruang Marungsri, Anant Oonsivilai, Thanatchai
Kulworawanichpong
Abstract: This paper presents the simulation results of electric field and
potential distributions along surface of silicone rubber polymer insulators
under clean and various contamination conditions. Alternate sheds silicone
rubber polymer insulator having leakage distance 290 mm was used in this
study. Two type of contaminants, plywood and cement dusts, have been studied
the effect of contamination conditions on the insulator surface. The objective
of this work is to comparison the effect of contamination conditions on
potential and electric field distributions along the insulator surface when
water droplets exist on the insulator surface. Finite element method (FEM) is
adopted for this work. The simulation results show that contaminations have no
effect of potential distribution on the insulator surface while electric field
distributions are obviously depended on contamination conditions. Water
droplets caused higher magnitude of electric field on the trunk portion
surface than the shed surface. The simulation results confirmed electrical
performance of polymer insulators under contamination conditions.
Keywords: Electric field
distribution, potential distribution, silicone rubber polymer insulator,
alternate shed, clean condition, contamination condition, water droplet,
plywood dust, cement dust, finite element method
Issue 3, Volume 4,
March 2009
Title of the Paper: Distributed FACT
Controllers as an Effective Tool for Reduction in Environmental pollution due
to Thermal Power Plant
DOWNLOAD
FULL PDF
Authors: Kishor Porate,
K. L. Thakre, G. L. Bodhe
Abstract: Flexible AC Transmission (FACTS) devices are installed in the
transmission network to divert the power flow, minimize the power losses and
to improve the line performance but it has some limitations and drawbacks.
Distributed Flexible AC Transmission (D-FACTS) is a improved version of FACTS
devices which is used to improve the security and reliability of the network
in a cost effective manner. This paper discusses the concept of D-FACTS
technology for saving of electrical energy, minimization of losses, reduction
of coal consumption and minimization of environmental pollution from thermal
power plants. This paper also discusses comparative evaluation of passive and
active approaches in design of controllers for transmission line. Analysis
also deals with computer simulation for reactances, equivalent voltages
required for injection in the transmission line, and number of distributed
modules per conductor per kilometre. Computations for saving of coal and
associated environmental pollution have been achieved. System details are
presented in the paper along with simulation results.
Keywords: Distributed
series compensator, D-FACTS, FACTS, Electrical energy saving, Coal economics,
Environmental pollution
Title of the Paper: Universal Power
Quality Conditioner
DOWNLOAD
FULL PDF
Authors: Moleykutty
George, Kartik Prasad Basu
Abstract: This manuscript proposes a novel control technique for three-phase
shunt active power line conditioner to determine the compensation current
associated with three-phase parallel converters. The proposed control scheme
is effective in achieving purely sinusoidal balanced source currents in phase
with respective source voltages. The method assumes that the active power line
conditioning system (APLC) supplies all the real power and imaginary power of
the load that differ from positive sequence fundamental average power consumed
by the load. Asymmetry, unbalance and distortion in the terminal voltages and
load currents have been considered in this manuscript. Since the proposed
control technique considered asymmetry, unbalance and distortion in both
terminal voltages and load currents, the developed APLC system can be treated
as a universal power quality conditioner for the power quality problems. The
supremacy of the proposed approach has been discussed and compared with
synchronous detection equal current approach (SDECA).
Keywords: APLC, parallel
converters, PSFAP, SDECA, asymmetry, unbalance, distortion, THD
Title of the Paper: Tunning of Fuzzy
Logic Power System Stabilizers using Genetic Algorithm in Multimachine Power
System
DOWNLOAD
FULL PDF
Authors: Manisha Dubey,
Nikos E. Mastorakis
Abstract: This paper presents an approach for the design of fuzzy logic power
system stabilizers using genetic algorithms. In the proposed fuzzy expert
system, speed deviation and its derivative have been selected as fuzzy inputs.
In this approach the parameters of the fuzzy logic controllers have been tuned
using genetic algorithm. Incorporation of GA in the design of fuzzy logic
power system stabilizer will add an intelligent dimension to the stabilizer
and significantly reduces computational time in the design process. It is
shown in this paper that the system dynamic performance can be improved
significantly by incorporating a genetic-based searching mechanism. To
demonstrate the robustness of the genetic based fuzzy logic power system
stabilizer (GFLPSS), simulation studies on multimachine system subjected to
small perturbation and three-phase fault have been carried out. Simulation
results show the superiority and robustness of GA based power system
stabilizer as compare to conventionally tuned controller to enhance system
dynamic performance over a wide range of operating conditions.
Keywords: Dynamic
stability, Fuzzy logic based power system stabilizer, Genetic Algorithms,
Genetic based power system stabilizer, Power system stabilizer
Issue 4, Volume 4,
April 2009
Title of the Paper: Tracking of
Fluctuating Load Power Quality Using Normalized Embedded Zero-tree Wavelet
Coding Considering Data Compression
DOWNLOAD
FULL PDF
Authors: Shu-Chen Wang,
Cheng-Ping Huang, Chi-Jui Wu
Abstract: In this paper, the data compression technique using the normalized
embedded zero-tree wavelet (NEZW) coding is presented for the long-duration
monitoring of a DC electric arc furnace and a railroad tracking load. For
those power quality disturbing loads, harmonics, voltage fluctuation, and
loading fluctuation are critical and stochastic load characteristics. In the
power quality measurement, while keep enough stochastic load information, it
is desired to reduce data size in long duration recording of voltage and
current waveforms. The effects of multi-resolution analysis levels and
threshold values in the NEZW coding are investigated. From the calculation
results of field measurement data, the NEZW coding almost preserves the values
of voltage fluctuation and power quantities. For storage of the field
measurement voltage and current waveforms, the NEZW coding can not only
greatly reduce data size, but it also can preserve sufficient load
information.
Keywords: Electric power
quality, data compression, discrete wavelet transform, multi-resolution
analysis, normalized embedded zero-tree wavelet coding
Title of the Paper: Discussion on the
Existing Deterministic Approaches for Evaluating the Voltage Deviation due to
Distributed Generation
DOWNLOAD
FULL PDF
Authors: Tsai-Hsiang
Chen, Nien-Che Yang
Abstract: This paper investigates uncertainties in the existing deterministic
approaches for evaluating steady-state voltage deviation due to distributed
generation. Nowadays, deterministic approaches are widely adopted by the
persons proposing the interconnection of distributed generation. However, the
existing deterministic approaches overlook some operation conditions that may
give rise to incorrect results and lead to wrong decisions in practical
applications. In this paper, the interconnection rules for distributed
generations and the existing deterministic approaches for evaluating
steady-state voltage deviations are introduced first. Then, various factors
effecting steady-state voltage deviation and the determination of maximum
allowable DG capacity are discussed. Finally, the uncertainties of the
existing deterministic approaches are discussed. It is intended for reference
by utility engineers processing distributed generation interconnection
applications.
Keywords: Distributed
generation, Distribution system, Power flow analysis, Power quality, Voltage
deviations, Wind power
Title of the Paper: Effects of
Renewable Distributed Generation on the Operational Characteristics of Meshed
Power Distribution Systems
DOWNLOAD
FULL PDF
Authors: Wen-Chih Yang,
Tsai-Hsiang Chen, Jun-Den Wu
Abstract: This paper analyzes the effects of renewable distributed generation
on the operational characteristics of meshed power distribution systems.
Meshed power distribution systems are more reliable than radial and
closed-loop ones; however, their structures and operating conditions are more
complex than the latter. Hence, operating these types of systems is not easy
for power engineers, especially in the case of combining renewable distributed
generation sources. This paper first develops the constant power model of a
renewable distributed generation source, then constructs the network model of
a medium-voltage meshed distribution system in the professional simulation
software, Matlab/Simulink. The effects of renewable distributed generation
sources on the operational characteristics of meshed distribution systems are
evaluated in detail. The evaluation takes into account the generation
capacity, connecting location, and operating power factor of renewable
distributed generation sources. The results shown in this paper can contribute
well to electrical utilities with meshed power distribution systems.
Keywords: Meshed power
distribution system, Renewable distributed generation, Operational
characteristics
Title of the Paper: Research of the
Impact of Voltage Imbalance on Power Distribution Systems and Equipment
DOWNLOAD
FULL PDF
Authors: Tsai-Hsiang
Chen, Cheng-Han Yang, Ting-Yen Hsieh
Abstract: This paper investigates the impact of voltage imbalance on power
distribution systems and equipment in various practical cases. The definition
of voltage imbalance is introduced first, followed by description of the
origins of voltage imbalance, and finally simulation results and discussion of
the impact of voltage imbalance on systems and equipment for specific cases
are presented. A commercial software package, Matlab/Simulink® was utilized to
build full-scale mathematical models of power distribution systems. The
simulation results of the study cases have indicated clearly, the causes and
impacts of voltage imbalance. The results are of value to engineers and
experts in designing suitable power distribution systems, balancing
single-phase loads in three phase systems and thereby improving system
efficiency.
Keywords: Voltage
unbalance, power distribution system, system efficiency, neutral wire
Issue 5, Volume 4,
May 2009
Title of the Paper: Atmospheric
Fluidized Bed Biomass and Waste Gasification
DOWNLOAD
FULL PDF
Authors: Martin Lisy,
Marek Balas, Jiri Moskalik, Jiri Pospisil
Abstract: Biomass as fuel is a significant source of renewable energy. In
comparison with fossil fuels, however, its effective use is more complicated.
This is the reason why other than conventional technologies of combustion are
sought to make energy use of biomass. One of the ways of converting biomass to
thermal energy or electric power is thermal gasification. The generated gas
can consequently be used in combustion engines, gas turbines, or be directly
burnt in the furnaces of steam boilers. Yet another interesting way of using
the gas is separation and use of its individual constituents, e.g. separation
of hydrogen for fuel cells. This paper is focused on survey of research of
biomass and waste gasification at the Faculty of Mechanical Engineering, Brno
University of Technology. The first part of this paper deals with testing of
the most frequent biomass by gasification process. Second part is focused on
catalytic methods of gasification gas cleaning using at experimental unit.
Keywords: Biomass, syngas
cleaning, renewable energy sources, gasification, dolomite, nickel catalysts
Title of the Paper: Circuit Breaker
Type Disconnector for Overvoltage Protector
DOWNLOAD
FULL PDF
Authors: Hitoshi Kijima,
Masao Shibayama
Abstract: A disconnector for an overvoltage protector is equipment that
disconnects a circuit when the overvoltage protector may fail in a short
circuit mode. The disconnector and the overvoltage protector are connected in
series. A fuse or a circuit breaker is normaly used as a disconnector. However
there are problems with both methods. A fuse is not recyclable once it goes
out. Even a circuit breaker is resetable, a lightning surge current causes a
swichgear of circuit breaker to open unnecessary. This malfunction prevents
the overvoltage protective function which eliminates a lightning surge current
into an instrument. If the problem which a switchgear of circuit breaker comes
floating can be solved, even when a lightning surge current flows through it,
an instrument can be protected by the overvoltage protector. This paper
presents a way of preventing circuit breker type disconnectors from the
malfunction.
Keywords: Circuit breaker,
disconnector, overvoltage protector, short circuit mode , lightning surge
Title of the Paper: A Novel Method of
Coordinating PSSs and FACTS Devices in Power System Stability Enhancement
DOWNLOAD
FULL PDF
Authors: M. Ahmadzadeh,
S. S. Mortazavi, A. Saeedian
Abstract: This paper shows the effect of power system Stabilizers (PSS) and
Flexible AC Transmission Systems (FACTS devices) based stabilizers containing
Thyristor controlled Series Compensator (TCSC), Static var compensators (SVC),
Thyristor Controlled and phase shifter (TCPS) on stability of power systems.
Moreover this paper presents a novel approach for designing coordinated
controllers of PSS and FACTS such as coordination of PSS with SVC, PSS with
TCSC and PSS with TCPS for enhancing small disturbance stability. The
coordinated control problem is formulated as a constrained optimization with
eigenvalue-based objective function .The proposed approach employs genetic
algorithm (GA) for optimization. To study the effectiveness of the proposed
controllers, three different loading conditions including light, normal and
heavy loading conditions are considered. Moreover in order to determine effect
of proposed design, three case studies are considered too. These include:
1-without compensation (base case), 2-single compensation and 3-coordinated
compensation. Simulation results show that the controller design approach is
able to provide better damping and stability performance.
Keywords: Power system
stabilizer, PSS, FACTS devices, SVC, TCSC, TCPS, Optimization, coordinated
design, small disturbance stability
Issue 6, Volume 4,
June 2009
Title of the Paper: A New Solar
Position Sensor Using Low Cost Photosensors Matrix for Tracking Systems
DOWNLOAD
FULL PDF
Authors: Alin Argeseanu,
Ewen Ritchie, Krisztina Leban
Abstract: A solar tracking system is a machine that is designed for the
orientation of different solar energy receivers, photovoltaic arrays or
thermal receivers. The paper proposes a new solution of the solar position
sensor used in tracking system control. The new matrix solar sensor (MSS) is
an economic device but in the same time MSS advantages are the robustness and
the accuracy. An actual tracking system that uses the new MSS achieves a
position accuracy better then 1°. The main innovative concept of the new MSS
is to use the ancient concept of solar clock to digitize the data set provided
by the photosensors matrix area. The new MSS uses eight ordinary
photo-resistors. These sensors working principle is to operate in two extreme
conditions: in bright area or in shaded area. This binary principle simplifies
the operating of the tracking control device.
Keywords: Solar energy,
tracking systems, optimum receiver position, photo-resistors, matrix sensor,
digital code converter, digital comparator
Title of the Paper: Thermal Model
Parameters Transformers
DOWNLOAD
FULL PDF
Authors: Marius-Constantin
Popescu, Nikos Mastorakis, Gheorghe Manolea, Aida Bulucea, Liliana
Perescu-Popescu
Abstract: The study of thermal model structural parameters is performed in
this work. Different methodologies to estimate thermal parameters with data
from standardised heat-run tests are compared.
Keywords: Estimate thermal
parameters, Control temperature
Title of the Paper: Cost Allocation of
Losses in Autonomous Power Systems with High Penetration of RES
DOWNLOAD
FULL PDF
Authors: K. A.
Papadogiannis, E. S. Karapidakis, N. D. Hatziargyriou
Abstract: Cost allocation of losses in power networks is an essential issue
especially under modern electricity markets with high penetration of renewable
energy sources (RES). This paper proposes the application of an efficient loss
allocation method developed to evaluate the marginal loss coefficients of
dispersed generation. The coefficients provide the contribution to the active
and reactive losses of each producer/consumer in order to define the
respective tariffs. One innovative feature of the proposed loss allocation
method is that, unlike other proposed approaches, it is irrespective of the
reference bus selection and takes in consideration the impact of reactive
flows on active power losses. Crete's power system has been considered as a
representative study case for the demonstration of the presented method.
Keywords: Distributed
generation, marginal loss coefficients, high renewable energy penetration,
transmission and distribution loss allocation
Issue 7, Volume 4,
July 2009
Title of the Paper: Construction and
Evaluation of Modern EVs Drive System
DOWNLOAD
FULL PDF
Authors: Hossein
Mousazadeh, Alireza Keyhani, Arzhang Javadi, Hossein Mobli, Karen Abrinia,
Ahmad Sharifi
Abstract: Ever–increasing in climate changing forces to shift to friendly and
clean energy alternatives such as renewable energies that their output is
usually electricity. 9oticeable part of these air pollutions is from tailpipe
of internal combustion engines. EVs could be parity by conventional Internal
Combustion Engine Vehicles (ICEV) in near future. They are simplest way to
replace fossil fuel powered vehicles. EVs are relatively cheap, have little
environmental impact and are a technology which is available here and now.
Using an electronic control board and two power boards, a high power EV drive
system was designed and constructed (designed for the vehicles up to 100 kW).
The controller uses power IGBT module and microcontroller technology to
simultaneously control two DC series motors. The driver controls direction of
motion and causes differential speeds of motors relative to steering rod and
acceleration pedal position. Driver simulation in MATLAB proved that the
required conditions of the problem were satisfied by PID controller; and the
optimum values for the control parameters Kp, Ki and Kd were found to be 320,
350 and 40, respectively. The result of simulation for these motors indicated
that for start up a high torque is available.
Keywords: Duty cycle,
Motor driver, PID control, Simulink, Unit step, steady-state error
Title of the Paper: Control Systems for
High Power Induction Machines
DOWNLOAD
FULL PDF
Authors: Marcel Ionel,
Mihail-Florin Stan, Corneliu Ioan Salisteanu, Octavian Marcel Ionel
Abstract: Issues orders in a power drives should be viewed in a more complex
and different from how do Electronics engineers of control systems. It is best
to look at the control system as a set of black boxes cascading with
mathematical models defined on a system of alternating current application.
Even if it takes a vector control strategy and obtain a similar behavior to
that of a DC motor, many problems remain unresolved because of the particular
structures of the converter and the motor due to their interaction with load
and source. This paper recommends to the experts and to the users of command
systems with frequency converters the usage of speed command and position
command to the variable frequency drives. There are analyzed also the commands
without position transducers, speed transducers or flux transducers based on
approximately results. There are included also logic elements and it’s proves
how the velocity evolution of the technology command of electrical machines in
different branches of the world economy finds a specific field in modern
electrical applications [10]. Powerful microprocessors and DSP (Digital Signal
Processor) are able not only to directly calculate the time of ignition of a
power semiconductor circuit such as the bridge phase, operating on frequency
of feed, but also perform other important tasks in applications industrial
automation as well as startup and shutdown sequencing, self monitoring and
diagnosing faults. The most important contribution is that power chips have
opened new frontiers in implementing sophisticated control systems for
electric drives.
Keywords: Electrical
commands, scalar control, vector control, mechanical characteristics,
transducers control, direct control approach, indirect control approach,
harmonic unit, test signal injection method.
Title of the Paper: Possible Impact of
Global Financial Crisis on Prices in Croatian Electricity Sector
DOWNLOAD
FULL PDF
Authors: Ivona Stritof,
Tomislav Gelo, Slavko Krajcar
Abstract: A regulatory method chosen for setting allowed revenue in
transmission and distribution of electricity in Croatia is a traditional Rate
of Return method. The main feature and, at the same time, the main drawback of
this method is that a price is in a direct relationship with the costs of
regulated company. A parameter used in this method, which does not solely
depend on the costs and management decisions, is the rate of return. The rate
of return is usually calculated using the weighted average cost of capital
formula (WACC). The WACC reflects two types of finance used to fund
investments, debt and equity respectively. The cost of equity is calculated
using the Capital Asset Pricing Model (CAPM). This Paper provides the WACC
calculation based on the estimates of particular parameters which could be
applied in the case of electricity transmission and distribution in Croatia.
The estimates are given for two scenarios, for the period prior to and
immediately after the beginning of domestic crisis (reflection of the global
financial crisis) and secondly for the period throughout the domestic crisis.
Thus, reflecting possible impacts of financial crisis on national and global
level on cost of capital in transmission and distribution of electricity.
Keywords: Distribution,
Transmission, Rate of return, WACC, CAPM, tariff system
Issue 8, Volume 4,
August 2009
Title of the Paper: Dynamic Simulation
of an Innovative Compressed Air Energy Storage Plant - Detailed Modelling of
the Storage Cavern
DOWNLOAD
FULL PDF
Authors: Lasse Nielsen,
Reinhard Leithner
Abstract: An innovative concept of an compressed air energy storage (CAES)
plant is developed at the Institute for Heat- and Fuel Technology (IWBT) of
the Technische Universit¨at Braunschweig. This concept aims to minimise the
negative aspects of state-of-the-art CAES-plants and is named isobaric
adiabatic compressed air energy storage plant with combined cycle (ISACOAST-CC).
To increase the storage efficiency, one aspect of this concept is to reduce
compressor losses due to high differences of the storage pressure within the
cavern by the use of a brine shuttle pond at the surface to drive out the
stored air at nearly constant pressure. The main focuses in the presented
article are the modelling and the calculation results of the simulation of the
isobaric air storage cavern which is used in this concept. Furthermore, the
results of a complete dynamic simulation of an ISACOAST-CC cycle are
presented. The storage efficiency as well as plant efficiency and specific
storage capacity are calculated.
Keywords: Compressed Air
Energy Storage (CAES), Enbipro, Dynamic simulation, Underground salt cavern
Title of the Paper: Determination of
the Induced Voltages by 220 kV Electric Overhead Power Lines Working in
Parallel and Narrow Routes. Measurements on the Ground and Mathematical Model
DOWNLOAD
FULL PDF
Authors: Flavius Dan
Surianu
Abstract: The paper presents the measurements that the author has done in the
South - West area of Romania for the 220 kV double circuit overhead power
lines having a passive circuit and an active one. It also describes a
mathematical simulation for determining the induced voltages by the active
circuit into the disconnected one. The measurements are compared with those
obtained through calculations in order to validate the mathematical model,
becoming a useful tool for professionals in electric high voltage overhead
power lines.
Keywords: Electromagnetic
interference, high voltage, induced voltage, electric capacity, mutual
inductivity.
Title of the Paper: Optimized Fuzzy
Variable Structure for a Three-Phase Rectifier with Power Factor Correction
DOWNLOAD
FULL PDF
Authors: Alberto Berzoy,
Miguel Strefezza
Abstract: This paper presents optimized fuzzy variable structure control
design in a three phase rectifier to correct the power factor. This control
strategy combines fuzzy and sliding mode control algorithms. Few fuzzy rules
are used for this scheme. The parameters of the fuzzy controller are adjusted
by using the VSC for a better response and robustness. To improve the behavior
of the system is applied a gradient optimized method to find better matrix
rule values. The simulations of the three-phase rectifier with controlled
current are carried out on a DSP. The control scheme presented here offer
higher robustness and it is easier to adjust and implement.
Keywords: Three-phase
Rectifier, Fuzzy Control, Variable Structure Controller, Optimization
Issue 9, Volume 4,
September 2009
Title of the Paper: The Transient
Current Distributions in a Vertical Electrode and the Ground
DOWNLOAD
FULL PDF
Authors: Y. Beck, A.
Braunsteiny
Abstract: This paper presents a model for calculating the transient space-time
current distributions in vertical electrodes and to the surrounding ground.
The model is based on the electromagnetic field theory for calculations of the
step function wave-pair response. The method takes into account the parameters
of the electrode, such as: the radius and the length of the electrode.
Furthermore, the conductivity, permittivity and the propagation velocity of
the currents in the ground are also considered. In the analysis, the electrode
is divided into finite sections. Thereafter, the "Compensating Currents",
ground leakage currents and the current in the electrode in each section are
calculated at all times. The model is applied by a MATLAB code for the
calculations of the above-mentioned currents' distributions. The results show
that for soils of high conductivity values, relative short electrodes are
needed for dissipating transient currents such as lightning currents.
Furthermore, soil conductivity is a more sensitive parameter compared to the
radius of the electrode and the permittivity of the ground.
Keywords: Current
distribution, Grounding electrodes Lightning, Transient response, vertical
electrodes
Title of the Paper: Using the Frequency
Response Analysis (FRA) in Transformers Internal Fault Detection
DOWNLOAD
FULL PDF
Authors: Jalal Abdallah
Abstract: This paper deals with diagnostic methods of the internal faults in
power transformers. The diagnostic process uses some of the current diagnosis
methods (e.g. oil test, dissolved gases analysis (DGA), partial discharge
(PD), etc.) to determine the condition of the transformer. In this process,
the most frequent diagnostic methods were listed and applied practically to be
compared. A conventional faulty oil-immersed transformer 400 V / 10 kV, 100
kVA was diagnosed and tested with different methods. The parameters and
results were compared with a normal working transformer with the same
parameters and age. After that an opening of the transformer was performed to
approve and to make a visual verification of the diagnostic methods and the
used devices. Among the applied methods, the frequency response analysis FRA
reflects the real situation of the internal faults such as short circuits,
mechanical displacement and deformation of the transformer windings.
Keywords: Transformer
Fault Diagnosis, Case Study, Frequency Response Analysis (FRA), Polarization
and Depolarization Current (PDC)
Title of the Paper: Control of an
Hybrid Solar-Wind System with Acid Battery for Storage
DOWNLOAD
FULL PDF
Authors: Nazih Moubayed,
Ali El-Ali, Rachid Outbib
Abstract: In the context of renewable energy, this study treats the
functioning of a hybrid system containing two sources: solar panels and wind
turbine. In fact, the conversion of solar energy and of wind energy to
electrical one is non pollutant. The studied system is connected to a lead
acid battery. The modeling of solar panel and its functioning in charging the
used battery is discussed in this paper. Same analysis is applied on the wind
turbine connected to the lead acid battery. Then, the functioning of the
hybrid system combined with the used battery is treated. Finally, a control
strategy of the global system is proposed.
Keywords: Renewable
energy, solar energy, wind energy, lead acid battery, modeling, control
Issue 10, Volume 4,
October 2009
Title of the Paper: Fault Induced
Voltage Sag Mitigation using Dynamic Voltage Restorer
DOWNLOAD
FULL PDF
Authors: N. R. Patne, K.
L. Thakre
Abstract: In this paper aim is to study the effectiveness of Dynamic Voltage
Restorer (DVR) in mitigating the voltage sag due to different types of faults
at every point of the power network under study. The comparative study is done
with conventional DVR along with series insertion transformer and proposed DVR
at the tertiary winding of already existing step down transformer in the
system at the load point. The effectiveness of DVR is studied in terms of
critical fault length. It is observed that there is reduction in critical
fault length with DVR in the system. Further the study shows that the voltage
sag compensation with transformer tertiary winding DVR is effective. But the
conventional DVR are more effective to compensate fault induced voltage sag at
the cost of additional insertion transformer. The system considered is
simulated in PSCAD/EMTDC to do the required study.
Keywords: Voltage sag,
faults, DVR, critical fault length
Title of the Paper: Improved Control
Strategy for Fuel Cell and Photovoltaic Inverters in a Microgrid
DOWNLOAD
FULL PDF
Authors: A. A. Salam, A.
Mohamed, M. A. Hannan
Abstract: This paper presents an improved control strategy for parallel
inverters so as to better manage power sharing among the distributed
generation units in a microgrid. The proposed control strategy combines both
power and voltage control schemes implemented on the voltage source inverters
which are used as power electronics interface systems for conversion of power
generated by fuel cell and photovoltaic generation units. Dynamic models of
the fuel cell and photovoltaic systems available in the PSCAD/EMTDC simulation
software are used as distributed generation units present in the microgrid. To
evaluate the effectiveness of the developed control strategy, the microgrid is
operated in grid connected, islanding and transition modes of operation.
Keywords: Distributed
generation, microgrid, fuel cell, photovoltaic, inverter
Issue 11, Volume 4,
November 2009
Title of the Paper: Optimum Time
Coordination of Overcurrent Relays in Distribution System Using Big-M
(Penalty) Method
DOWNLOAD
FULL PDF
Authors: Prashant P.
Bedekar, Sudhir R. Bhide, Vijay S. Kale
Abstract: This paper presents big-M (penalty) method for optimum time
coordination of overcurrent (OC) relays. The method is based on the simplex
algorithm which is used to find optimum solution of linear programming problem
(LPP). The method introduces artificial variables in the objective function to
get an initial basic feasible solution (IBFS). Artificial variables are
removed using iterative process which also leads to an optimum solution. The
OC relays are the major protection devices in a distribution system. To reduce
the power outages, mal-operation of the backup relays should be avoided, and
therefore, OC relay time coordination in power distribution network is a major
concern of protection engineer. The OC relay time coordination in ring fed
distribution networks is a highly constrained optimization problem. The
purpose is to find an optimum relay setting to minimize the time of operation
of relays and at the same time, to avoid the mal-operation of relays. Big-M
simplex technique for optimum time coordination of OC relays in a ring fed
distribution system is presented in this paper.
Keywords: Backup
protection, Big-M method, Constrained optimization, Overcurrent relay, Ring
fed system, Time coordination
Title of the Paper: A New Monitoring
Spectral Technique for Subsynchronous Electrical Torque Frequencies
DOWNLOAD
FULL PDF
Authors: Jose A.
Castillo J., Daniel Olguin S., Carlos A, Rivera S., David Sebastian B.
Abstract: The modern protection schemes are designed to protect against the
negative effects that has the Subsynchronous Resonance (SSR) in the
turbo-generators mechanical system damping. The studies which have been done
with torsional monitoring data allows to propose the maintenance and
inspection planning to mitigate the damages and overcome with this expensive
repairs, this is because very few monitoring equipment is designed to capture
transitory sporadic oscillations with torsional phenomenon characteristic. In
this work, it is proposed a new monitoring technique through the torsional
behavior modes forms based on a spectral analysis of the electrical
subsynchronous torque component to detect its associated frequencies and to
establish the coincidence with the mechanical turbo-generator torsional
oscillation subsynchronous frequencies, transient load model is included
indicating results of utmost importance in their modes damping
Keywords: Subsynchronous
Resonance, Electrical Torque, Subsynchronous component, Prony, Torsional Modes
Forms
Issue 12, Volume 4,
December 2009
Title of the Paper: Modeling
Subharmonic and Chaotic Ferroresonance with Transformer Core Model Including
Magnetic Hysteresis Effects
DOWNLOAD
FULL PDF
Authors: Paul Moses,
Mohammad Masoum
Abstract: Ferroresonance is a highly destructive power quality phenomenon
caused by complex oscillations generated by nonlinear magnetizing inductances
in ferromagnetic materials and capacitive elements in power systems. In an
effort to better understand ferroresonance and predict bifurcations and
responses, an improved nonlinear transformer model for dynamic and
steady-state operating conditions is developed which includes magnetic
hysteresis nonlinearities of the transformer core. The model expands on
Tellinen’s scalar hysteresis approach which includes major and minor
hysteresis loop effects. This paper carries out an investigation into
single-phase transformer ferroresonance initiated by switching transients
using the developed model. A range of ferroresonance modes (e.g., subharmonic
and chaotic) initiated by switching transients is identified with the
transformer core model. The model is used to compute time-domain waveforms of
transformer flux, voltage and magnetizing current for several ferroresonance
modes. Furthermore, Poincar/e and phase-plane portraits are used to examine
the stability domain of observed ferroresonance modes. The main contribution
of this work is a new analysis into ferroresonance through an improved
transformer model which incorporates magnetic hysteresis effects.
Keywords: Chaos,
ferroresonance, hysteresis model, nonlinear dynamics, Poincar/e, power
quality, transformer
Title of the Paper: Proposed Techniques
for Identifying Open and Short Circuit Sections in Distribution Networks
DOWNLOAD
FULL PDF
Authors: Wael Al-Hasawi,
Mahmoud Gilany
Abstract: This paper presents novel solutions for three problems encountered
in the closed loop distribution systems. The first problem is how to identify
a faulty section after being successfully isolated by the protection system.
The second problem is how to identify a section affected with undetected
open-circuit fault. A novel circuit is suggested in this paper to solve these
two problems. The third problem addressed in the paper is how to deal with
undetected faults in the 11 KV part of a 132/11 KV network which may result in
a complete shut down problems. An effective modification in the trip circuit
of the relays protecting the main feeders of the closed loops is suggested to
avoid this problem. The validity of the proposed circuits is examined using
ASPEN-OneLiner simulation program applied to a real part of Kuwait power
distribution network. It is also checked against the specifications of the
available equipment used in the real network. The proposed circuits provide
fault detection capabilities normally achieved by the advanced and expensive
Distribution Automation System (DAS) but with minimal cost.
Keywords: Distribution
networks, open-circuit faults, Undetected faults, Ring systems, Fault
identification, Fault detection
|
