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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Electrical Engineering and Technology
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Journal DOI :
The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 3, Issue 4 - Dec 2008
Volume 3, Issue 3 - Sep 2008
Volume 3, Issue 2 - Jun 2008
Volume 3, Issue 1 - Mar 2008
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Active and Reactive Power Control Model of Superconducting Magnetic Energy Storage (SMES) for the Improvement of Power System Stability
Ham, Wan-Kyun ; Hwang, Sung-Wook ; Kim, Jung-Hoon ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 1~7
DOI : 10.5370/JEET.2008.3.1.001
Superconducting Magnetic Energy Storage (SMES) can inject or absorb real and reactive power to or from a power system at a very fast rate on a repetitive basis. These characteristics make the application of SMES ideal for transmission grid control and stability enhancement. The purpose of this paper is to introduce the SMES model and scheme to control the active and reactive power through the power electronic device. Furthermore, an optimal priority scheme is proposed for the combination of active and reactive power control to be able to stabilize power transient swings.
Power System Nonlinearity Modal Interaction by the Normal Forms of Vector Fields
Zhang, Jing ; Wen, J.Y. ; Cheng, S.J. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 8~13
DOI : 10.5370/JEET.2008.3.1.008
Because of the robust nonlinear characteristics appearing in today's modern power system, a strong interaction exists between the angle stability and the voltage stability, which were conventionally studied insularly. However, as the power system is a complex unified system, angle instability always happens in conjunction with voltage instability. The authors propose a novel method to analyze this type of stability problem. In the proposed method, the theory of normal forms of vector fields is utilized to treat the auxiliary dynamic system. By use of this method, the interaction between response modes caused by the nonlinearity of the power system can be analyzed. Consequently, the eigenvalue analysis method is extended to cope with performance analysis of the power system with heavy nonlinearity. The effectiveness of the proposed methodology is verified on a 3-bus power system.
Electricity Price Prediction Model Based on Simultaneous Perturbation Stochastic Approximation
Ko, Hee-Sang ; Lee, Kwang-Y. ; Kim, Ho-Chan ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 14~19
DOI : 10.5370/JEET.2008.3.1.014
The paper presents an intelligent time series model to predict uncertain electricity market price in the deregulated industry environment. Since the price of electricity in a deregulated market is very volatile, it is difficult to estimate an accurate market price using historically observed data. The parameter of an intelligent time series model is obtained based on the simultaneous perturbation stochastic approximation (SPSA). The SPSA is flexible to use in high dimensional systems. Since prediction models have their modeling error, an error compensator is developed as compensation. The SPSA based intelligent model is applied to predict the electricity market price in the Pennsylvania-New Jersey-Maryland (PJM) electricity market.
Power Distribution System Planning with Demand Uncertainty Consideration
Wattanasophon, Sirichai ; Eua-arporn, Bundhit ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 20~28
DOI : 10.5370/JEET.2008.3.1.020
This paper proposes a method for solving distribution system planning problems taking into account demand uncertainty and geographical information. The proposed method can automatically select appropriate location and size of a substation, routing of feeders, and appropriate sizes of conductors while satisfying constraints, e.g. voltage drop and thermal limit. The demand uncertainty representing load growth is modeled by fuzzy numbers. Feeder routing is determined with consideration of existing infrastructure, e.g. streets and canals. The method integrates planner's experience and process optimization to achieve an appropriate practical solution. The proposed method has been tested with an actual distribution system, from which the results indicate that it can provide satisfactory plans.
New Method to Quantify the Operation Condition for Zone 3 Impedance Relays during Low-Frequency Power Swings
Li, Shenghu ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 29~35
DOI : 10.5370/JEET.2008.3.1.029
With long time setting, zone 3 impedance relays are considered insensitive to power swings, and their operation condition during power swings is seldom analyzed. Instead of ti me-consuming simulation to the swing loci, their operation condition is directly quantified by polynominal functions in this paper to find the critical swing angle and frequency for relay operation under different relay settings and system parameters. It is found: (1) the swing loci are more densely populated inside than outside of the protection region, which corresponds to long residence time and possible relay operations; (2) the relays may be sensitive to load encroac hments and stable power swings with different relay settings and system parameters; (3) the critical swing frequency may be in the range of low-frequency power swings.
Simulation of Capacitively Graded Bushing for Very Fast Transients Generated in a GIS during Switching Operations
Rao, M.Mohana ; Rao, T. Prasad ; Ram, S.S. Tulasi ; Singh, B.P. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 36~42
DOI : 10.5370/JEET.2008.3.1.036
In a gas insulated substation (GIS), Very Fast Transient Over-voltages (VFTOs) are generated due to switching operations and ground faults. These fast transients are associated with high frequency components of the order of a few hundreds of MHz. These transients may cause internal faults i.e., layer-to-layer faults or minor faults in a capacitively graded bushing, which is one of the important pieces of terminal equipment for GIS. In the present study, the PSPICE model has been developed to calculate the voltage distribution across the layers of 420kV graded bushing for high frequency pulses of rise time 1 to 50ns, which simulate the VFTO. For this simulation, an equivalent electrical network of bushing with different equivalent layers has been considered. The effect of different equivalent layers modeling circuits on the non-uniform voltage factor has been analysed. The influence of copper strip inductance on voltage distribution across layers has also been analysed for various rise times of high frequency transients. Finally, the leakage current of the bushing is calculated for evaluating the bushing condition under these transients.
Design of Digital Circuit Structure Based on Evolutionary Algorithm Method
Chong, K.H. ; Aris, I.B. ; Bashi, S.M. ; Koh, S.P. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 43~51
DOI : 10.5370/JEET.2008.3.1.043
Evolutionary Algorithms (EAs) cover all the applications involving the use of Evolutionary Computation in electronic system design. It is largely applied to complex optimization problems. EAs introduce a new idea for automatic design of electronic systems; instead of imagine model, ions, and conventional techniques, it uses search algorithm to design a circuit. In this paper, a method for automatic optimization of the digital circuit design method has been introduced. This method is based on randomized search techniques mimicking natural genetic evolution. The proposed method is an iterative procedure that consists of a constant-size population of individuals, each one encoding a possible solution in a given problem space. The structure of the circuit is encoded into a one-dimensional genotype as represented by a finite string of bits. A number of bit strings is used to represent the wires connection between the level and 7 types of possible logic gates; XOR, XNOR, NAND, NOR, AND, OR, NOT 1, and NOT 2. The structure of gates are arranged in an
matrix form in which m is the number of input variables.
Secant Method for Economic Dispatch with Generator Constraints and Transmission Losses
Chandram, K. ; Subrahmanyam, N. ; Sydulu, M. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 52~59
DOI : 10.5370/JEET.2008.3.1.052
This paper describes the secant method for solving the economic dispatch (ED) problem with generator constraints and transmission losses. The ED problem is an important optimization problem in the economic operation of a power system. The proposed algorithm involves selection of minimum and maximum incremental costs (lambda values) and then the evaluation of optimal lambda at required power demand is done by secant method. The proposed algorithm has been tested on a power system having 6, 15, and 40 generating units. Studies have been made on the proposed method to solve the ED problem by taking 120 and 200 units with generator constraints. Simulation results of the proposed approach were compared in terms of solution quality, convergence characteristics, and computation efficiency with conventional methods such as lambda iterative method, heuristic methods such as genetic algorithm, and meta-heuristic methods like particle swarm optimization. It is observed from different case studies that the proposed method provides qualitative solutions with less computational time compared to various methods available in the literature.
Electromagnetic Model to Estimate the Vibrations of a Switched Reluctance Machine on the Basis of the Eelctric Power Supply
Badreddine, Benabdallah Mohammed ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 60~67
DOI : 10.5370/JEET.2008.3.1.060
The vibrations and noise origin in electric material is due to several coupled physical phenomena. The revolving electric machine complete modeling is complex; it does not allow simple parametric machine structure studies for various operation modes. This work presents a simple electromagnetic model which makes possible the machine principal parts flow estimation from flux density. Special interest is given in determining Switched Reluctance Machine (S.R.M) radial acceleration in accordance with the current supply. Our focus will be only on the magnetic origin efforts that are dominating in the S.R.M. The efforts calculation versus the current is presented in the case of a machine with a linearized rate. These efforts are considered as a tangential force producing the torque and a radial force that generates no torque. The application is realized on a 6/4 low power S.R.M type (6 stator teeth and 4 teeth rotor). The mechanical response is substituted in a transfer function. The model takes account of the power supply of the machine, the relation between the current supply and the efforts as well as the vibratory response of the machine to these efforts. Finally, the model is validated by comparison with similar experimental results within the framework of the definite assumptions.
Modeling of a Four-Quadrant Switched Reluctance Motor Drive on EMTDC/PSCAD
El-Samahy, Ismael ; Marei, Mostafa I. ; El-Saadany, Ehab F. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 68~78
DOI : 10.5370/JEET.2008.3.1.068
This paper introduces a complete package for SRM drive on Power System Computer-Aided Design/Electromagnetic Transients (PSCAD/EMTDC). A three-phase SRM drive is modeled and simulated on PSCAD. The motor is modeled using an accurate nonlinear analytical model that takes into consideration the machine nonlinearities. A current control algorithm is applied for torque ripple minimization to achieve a smooth output torque which is necessary for high performance applications. The motor drive is tested for four-quadrant operations. The modeled SRM is capable of operating as a motor or generator during clockwise and counterclockwise motions. The proposed package helps in understanding the operational principles of switched reluctance motors, investigating the dynamic characteristics of SRM drives, and achieving a high performance dynamic control task.
A New Approach to Direct Torque Control for Induction Motor Drive Using Amplitude and Angle of the Stator Flux Control
Kumsuwan, Yuttana ; Premrudeepreechacharn, Suttichai ; Toliyat, Hamid A. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 79~87
DOI : 10.5370/JEET.2008.3.1.079
This paper proposes the design and implementation of a direct torque controlled induction motor drive system. The method is based on control of decoupling between amplitude and angle of reference stator flux for determining reference stator voltage vector in generating PWM output voltage for induction motors. The objective is to reduce electromagnetic torque ripple and stator flux droop which result in a decrease in current distortion in steady state condition. In addition, the proposed technique provides simplicity of a control system. The direct torque control is based on the relationship between instantaneous slip angular frequency and rotor angular frequency in adjustment of the reference stator flux angle. The amplitude of the reference stator flux is always kept constant at rated value. Experimental results are illustrated in this paper confirming the capability of the proposed system in regards to such issues as torque and stator flux response, stator phase current distortion both in dynamic and steady state with load variation, and low speed operation.
Field Circuit Coupling Optimization Design of the Main Electromagnetic Parameters of Permanent Magnet Synchronous Motor
Zhou, Guang-Xu ; Tang, Ren-Yuan ; Lee, Dong-Hee ; Ahn, Jin-Woo ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 88~93
DOI : 10.5370/JEET.2008.3.1.088
The electromagnetic parameters of a permanent magnet synchronous motor (PMSM) such as the open load permanent magnet flux, d axis reactance
, and q axis reactance
, are most essential to the performance analysis and optimization design of the motor. Based on the numerical analysis of the 3D electromagnetic field, the three electromagnetic parameters of permanent magnet synchronous motors with U form interior rotor structures are calculated by FEA. The rules of the leakage coefficient and reactance parameters changing with the air gap length, permanent magnet magnetism length, and isolation magnetic bridge dimensions in the rotor are given. The calculated values agree well with the measured values. The FEA results are integrated with the self compiled electromagnetic design program to optimize the prototype motor. The tested performances of the prototype motor prove that the method is suitable for the optimization of motor structure.
Single-phase Active Power Filter Based on Rotating Reference Frame Method for Harmonics Compensation
Kim, Jin-Sun ; Kim, Young-Seok ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 94~100
DOI : 10.5370/JEET.2008.3.1.094
This paper presents a new control method of single-phase active power filter (APF) for the compensation of harmonic current components in nonlinear loads. To facilitate the possibility of complex calculation for harmonic current detection of the single phase, a single-phase system that has two phases was constructed by including an imaginary second-phase giving time delay to the load current. The imaginary phase, which lagged the load current T/4 (Here T is the fundamental cycle) is used in the conventional method. But in this proposed method, the new signal as the second phase is delayed by the filter. Because this control method is applied to a single-phase system, an instantaneous calculation was developed by using the rotating reference frames synchronized to source-frequency rather than by applying instantaneous reactive power theory that uses the conventional fixed reference frames. The control scheme of single-phase APF for the current source with R-L loads is applied to a laboratory prototype to verify the proposed control method.
Optimization of Fuzzy Set-Fuzzy Systems based on IG by Means of GAs with Successive Tuning Method
Park, Keon-Jun ; Oh, Sung-Kwun ; Kim, Hyun-Ki ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 101~107
DOI : 10.5370/JEET.2008.3.1.101
We introduce an optimization of fuzzy set-fuzzy systems based on IG (Information Granules). The proposed fuzzy model implements system structure and parameter identification by means of IG and GAs. The concept of information granulation was coped with to enhance the abilities of structural optimization of the fuzzy model. Granulation of information realized with C-Means clustering helps determine the initial parameters of the fuzzy model such as the initial apexes of the membership functions in the premise part and the initial values of polynomial functions in the consequence part of the fuzzy rules. The initial parameters are adjusted effectively with the help of the GAs and the standard least square method. To optimally identify the structure and the parameters of the fuzzy model we exploit GAs with successive tuning method to simultaneously search the structure and the parameters within one individual. We also consider the variant generation-based evolution to adjust the rate of identification of the structure and the parameters in successive tuning method. The proposed model is evaluated with the performance of the conventional fuzzy model.
Design of Polynomial Neural Network Classifier for Pattern Classification with Two Classes
Park, Byoung-Jun ; Oh, Sung-Kwun ; Kim, Hyun-Ki ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 108~114
DOI : 10.5370/JEET.2008.3.1.108
Polynomial networks have been known to have excellent properties as classifiers and universal approximators to the optimal Bayes classifier. In this paper, the use of polynomial neural networks is proposed for efficient implementation of the polynomial-based classifiers. The polynomial neural network is a trainable device consisting of some rules and three processes. The three processes are assumption, effect, and fuzzy inference. The assumption process is driven by fuzzy c-means and the effect processes deals with a polynomial function. A learning algorithm for the polynomial neural network is developed and its performance is compared with that of previous studies.
A Study on the Thermal Properties of CNT reinforced Semiconductive Shield Materials Used in Power Cables
Yang, Hoon ; Bang, Jeong-Hwan ; Chang, Hong-Soon ; Nah, Chang-Woon ; Park, Dae-Hee ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 115~120
DOI : 10.5370/JEET.2008.3.1.115
Use of the carbon nanotube is superior to general powder state materials of mechanical and electrical properties. Because its ratio of diameter and length (aspect ratio) is very large, it has been known as a type of ideal nano-reinforcement material. Based on this advantage, the existing carbon black of semiconductive shield materials used in power cables can acquire excellent properties by using a small amount of carbon nanotubes. Thus, we investigated the thermal properties of the carbon nanotube, such as thermal conductivity, specific heat, and DSC (Differential Scanning Calorimetry). We found that a high thermal resistance level is demonstrated by using a small amount of carbon nanotubes. As a result, this tendency confirms high cross-linking density in a new network in which the carbon nanotube between carbon black constitute molecules shows a bond by similar constructive properties.
Fabrication of Carbon Nanotube Field Emitters
Yoon, Hyeun-Joong ; Jeong, Dae-Jung ; Jun, Do-Han ; Yang, Sang-Sik ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 121~124
DOI : 10.5370/JEET.2008.3.1.121
This paper presents the fabrication and field emission of carbon nanotube field emitters for a micro mass spectrometer. The carbon nanotube is an adequate material as a field emitter since it has good characteristics. We have successfully fabricated a diode field emitter and a triode field emitter. Each field emitter has been constructed using several micromachining processes and a thermal CVD process. In the case of the diode field emitter, to increase the electric field, the carbon nanotubes are selectively grown on the patterned nickel catalyst layer. The electron current of the diode field emitter is 73.2
when the anode voltage is 1100V. That of the triode field emitter is 3.4 pA when the anode voltage is 1000V.
Handling a Multi-Tasking Environment via the Dynamic Search Genetic Algorithm
Koh, S.P. ; Aris, I.B. ; Bashi, S.M. ; Chong, K.H. ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 125~129
DOI : 10.5370/JEET.2008.3.1.125
A new genetic algorithm for the solution of a multi-tasking problem is presented in this paper. The approach introduces innovative genetic operation that guides the genetic algorithm more directly towards better quality of the population. A wide variety of standard genetic parameters are explored, and results allow the comparison of performance for cases both with and without the new operator. The proposed algorithm improves the convergence speed by reducing the number of generations required to identify a near-optimal solution, significantly reducing the convergence time in each instance.
Scan Cell Grouping Algorithm for Low Power Design
Kim, In-Soo ; Min, Hyoung-Bok ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 130~134
DOI : 10.5370/JEET.2008.3.1.130
The increasing size of very large scale integration (VLSI) circuits, high transistor density, and popularity of low-power circuit and system design are making the minimization of power dissipation an important issue in VLSI design. Test Power dissipation is exceedingly high in scan based environments wherein scan chain transitions during the shift of test data further reflect into significant levels of circuit switching unnecessarily. Scan chain or cell modification lead to reduced dissipations of power. The ETC algorithm of previous work has weak points. Taking all of this into account, we therefore propose a new algorithm. Its name is RE_ETC. The proposed modifications in the scan chain consist of Exclusive-OR gate insertion and scan cell reordering, leading to significant power reductions with absolutely no area or performance penalty whatsoever. Experimental results confirm the considerable reductions in scan chain transitions. We show that modified scan cell has the improvement of test efficiency and power dissipations.
Design of Robust PI Controller for Vehicle Suspension System
Yeroglu, Celaleddin ; Tan, Nusret ;
Journal of Electrical Engineering and Technology, volume 3, issue 1, 2008, Pages 135~142
DOI : 10.5370/JEET.2008.3.1.135
This paper deals with the design of a robust PI controller for a vehicle suspension system. A method, which is related to computation of all stabilizing PI controllers, is applied to the vehicle suspension system in order to obtain optimum control between passenger comfort and driving performance. The PI controller parameters are calculated by plotting the stability boundary locus in the
-plane and illustrative results are presented. In reality, like all physical systems, the vehicle suspension system parameters contain uncertainty. Thus, the proposed method is also used to compute all the parameters of a PI controller that stabilize a vehicle suspension system with uncertain parameters.