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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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The Korean Institute of Electrical Engineers
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Volume 5, Issue 4 - Nov 2010
Volume 5, Issue 3 - Sep 2010
Volume 5, Issue 2 - Jun 2010
Volume 5, Issue 1 - Mar 2010
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Centralized Control Algorithm for Power System Performance using FACTS Devices in the Korean Power System
Kang, Sang-Gyun ; Seo, Sang-Soo ; Lee, Byong-Jun ; Chang, Byung-Hoon ; Myung, Ro-Hae ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 353~362
DOI : 10.5370/JEET.2010.5.3.353
This paper presents a centralized control algorithm for power system performance in the Korean power system using Flexible AC Transmission Systems (FACTS) devices. The algorithm is applied to the Korean power system throughout the metropolitan area in order to alleviate inherent stability problems, especially concerns with voltage stability. Generally, control strategies are divided into local and centralized control. This paper is concerned with a centralized control strategy in terms of the global system. In this research, input data of the proposed algorithm and network data are obtained from the SCADA/EMS system. Using the full system model, the centralized controller monitors the system condition and decides the operating point according to the control objectives that are, in turn, dependent on system conditions. To overcome voltage collapse problems, load-shedding is currently applied in the Korean power system. In this study, the application of the coordination between FACTS and switch capacitor (SC) can restore the solvability without load shedding or guarantee the FV margin when the margin is insufficient. Optimal Power Flow (OPF) algorithm, for which the objective function is loss minimization, is used in a stable case. The results illustrate examples of the proposed algorithm using SCADA/EMS data of the Korean power system in 2007.
Use of High-performance Graphics Processing Units for Power System Demand Forecasting
He, Ting ; Meng, Ke ; Dong, Zhao-Yang ; Oh, Yong-Taek ; Xu, Yan ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 363~370
DOI : 10.5370/JEET.2010.5.3.363
Load forecasting has always been essential to the operation and planning of power systems in deregulated electricity markets. Various methods have been proposed for load forecasting, and the neural network is one of the most widely accepted and used techniques. However, to obtain more accurate results, more information is needed as input variables, resulting in huge computational costs in the learning process. In this paper, to reduce training time in multi-layer perceptron-based short-term load forecasting, a graphics processing unit (GPU)-based computing method is introduced. The proposed approach is tested using the Korea electricity market historical demand data set. Results show that GPU-based computing greatly reduces computational costs.
D-q Equivalent Circuit-based Protection Algorithm for a Doubly-fed Induction Generator in the Time Domain
Kang, Yong-Cheol ; Kang, Hae-Gweon ; Lee, Ji-Hoon ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 371~378
DOI : 10.5370/JEET.2010.5.3.371
Most modern wind turbines employ a doubly-fed induction generator (DFIG) system due to its many advantages, such as variable speed operation, relatively high efficiency, and small converter size. The DFIG system uses a wound rotor induction machine so that the magnetizing current of the generator can be fed from both the stator and the rotor. We propose a protection algorithm for a DFIG based on a d-q equivalent circuit in the time domain. In the DFIG, the voltages and currents of the rotor side and the stator side are available. The proposed algorithm estimates the instantaneous induced voltages of magnetizing inductance using those voltages and currents from both the stator and the rotor sides. If the difference between the two estimated induced voltages exceeds the threshold, the proposed algorithm detects an internal fault. The performance of the proposed algorithm is verified under various operating and fault conditions using a PSCAD/EMTDC simulator.
A Study on New Power Business Model Using Power Information Technology
Bae, Sung-Hwan ; Kim, Ja-Hee ; Lim, Han-Seung ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 379~388
DOI : 10.5370/JEET.2010.5.3.379
The Korea Electric Power Corporation (KEPCO) recorded 2.9 trillion won deficit in the aftermath of the world financial crisis. KEPCO is trying to escape from the business crisis in every way; however, it is impossible to make huge profit by selling electricity alone. Overseas electrical utilities make profits by selling gas and heat along with electricity. However, it is difficult for KEPCO to enter the gas and the heat selling market because other public companies are already dealing with them. In this situation, improving the business is possible when KEPCO develops a new business model and creates added value using Korean advanced Power IT combined with electricity. This study shows a new business model using Power IT, based on a survey targeting managers in KEPCO branch office and electrical engineers in the field. We hope the new business model suggested in this study is adapted to the real field to create high value in the future.
A Cost/Worth Approach to Evaluate UPFC Impact on ATC
Rajabi-Ghahnavieh, Abbas ; Fotuhi-Firuzabad, Mahmud ; Shahidehpour, Mohammad ; Feuillet, Rene ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 389~399
DOI : 10.5370/JEET.2010.5.3.389
Available transfer capability (ATC) is a measure of the transfer capability remaining in a transmission system. Application of unified power flow controllers (UPFCs) could have positive impacts on the ATC of some paths while it might have a negative impact on the ATC of other paths. This paper presents an approach to evaluate the impacts of UPFCs on the ATC from a cost/worth point of view. The UPFC application worth is considered as the maximum cost saving in enhancing the ATC of the paths due to the UPFC implementation. The cost saving is considered as the cost of optimal application of other system reinforcement alternatives (except for UPFC) to reach the same ATC level obtained by UPFC application. UPFC application costs include the maximum cost of alleviating the probable negative impact on the ATC of some paths caused by implementing UPFCs. Optimal system reinforcement is used for systems with UPFCs to determine the aforementioned cost. The proposed method is applied to the IEEERTS and the results are evaluated through a sensitivity analysis. The cost/worth of UPFC application is also used to develop an index for optimal UPFC location and the results are compared with those of other indices. A comparison is finally made with the results obtained using an existing ATC allocation profit-based approach to determine UPFC application worth.
A Practical Power System Stabilizer Tuning Method and its Verification in Field Test
Shin, Jeong-Hoon ; Nam, Su-Chul ; Lee, Jae-Gul ; Baek, Seung-Mook ; Choy, Young-Do ; Kim, Tae-Kyun ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 400~406
DOI : 10.5370/JEET.2010.5.3.400
This paper deals with parameter tuning of the Power System Stabilizer (PSS) for 612 MVA thermal power plants in the KEPCO system and its validation in a field test. In this paper, the selection of parameters, such as lead-lag time constants for phase compensation and system gain, is optimized using linear and eigenvalue analyses. This is then verified through the time-domain transient stability analysis. In the next step, the performance of PSS is finally verified by the generator's on-line field test. After the field test, measured and simulated data are also compared to prove the effectiveness of the models used in the simulations.
A Probabilistic Approach to the Protection Capability Evaluation of Distance Relay in Transmission Systems
Zhang, Wen-Hao ; Lee, Seung-Jae ; Choi, Myeon-Song ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 407~414
DOI : 10.5370/JEET.2010.5.3.407
This paper proposes a probability measure for the evaluation of relay performance from two aspects, namely, correct trip and no-unwanted trip. They are developed based on the relationship between relay settings and relay measurements, which follow a Gaussian probability model. The proposed method based on strict mathematical derivation is applied to protection capability evaluation of distance relays under various settings. Considering the specific attributes of each protection zone, the optimal settings are also determined accordingly. The protection capability could demonstrate clearly the relay performance under various settings and the optimal settings could provide good references for engineering applications.
Transient Stability Enhancement by DSSC with Fuzzy Supplementary Controller
Khalilian, Mansour ; Mokhtari, Maghsoud ; Nazarpour, Daryoosh ; Tousi, Behrouz ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 415~422
DOI : 10.5370/JEET.2010.5.3.415
The distributed flexible alternative current transmission system (D-FACTS) is a recently developed FACTS technology. Distributed Static Series Compensator (DSSC) is one example of DFACTS devices. DSSC functions in the same way as a Static Synchronous Series Compensator (SSSC), but is smaller in size, lower in price, and possesses more capabilities. Likewise, DSSC lies in transmission lines in a distributed manner. In this work, we designed a fuzzy logic controller to use the DSSC for enhancing transient stability in a two-machine, two-area power system. The parameters of the fuzzy logic controller are varied widely by a suitable choice of membership function and parameters in the rule base. Simulation results demonstrate the effectiveness of the fuzzy controller for transient stability enhancement by DSSC.
Coupling Particles Swarm Optimization for Multimodal Electromagnetic Problems
Pham, Minh-Trien ; Song, Min-Ho ; Koh, Chang-Seop ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 423~430
DOI : 10.5370/JEET.2010.5.3.423
Particle swarm optimization (PSO) algorithm is designed to find a single global optimal point. However, the PSO needs to be modified in order to find multiple optimal points of a multimodal function. These modifications usually divide a swarm of particles into multiple subswarms; in turn, these subswarms try to find their own optimal point, resulting in multiple optimal points. In this work, we present a new PSO algorithm, called coupling PSO to find multiple optimal points of a multimodal function based on coupling particles. In the coupling PSO, each main particle may generate a new particle to form a couple, after which the couple searches its own optimal point using non-stop-moving PSO algorithm. We tested the suggested algorithm and other ones, such as clustering PSO and niche PSO, over three analytic functions. The coupling PSO algorithm was also applied to solve a significant benchmark problem, the TEAM workshop problem 22.
Torque Calculation Method of a Permanent Magnet Spherical Motor
Lee, Hyung-Woo ; Kang, Dong-Woo ; Lee, Ju ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 431~434
DOI : 10.5370/JEET.2010.5.3.431
This paper presents the torque calculation method of a permanent magnet spherical motor. To calculate using the finite element method (FEM), three-dimensional (3D) FEM must be used. However, since the method requires excessive time and memory, an easier torque calculation method is hereby presented. In the proposed method, it is very important to obtain the approximation function of the torque profile curve. We present the approximation method of the torque profile curve and show that the torque calculation result can approximate the torque obtained by 3-D FEM.
18-step Back-to-Back Voltage Source Converter with Pulse Interleaving Circuit for HVDC Application
Lee, Hye-Yeon ; Jeong, Jong-Kyou ; Lee, Ji-Heon ; Han, Byung-Moon ; Choi, Nam-Sup ; Cha, Han-Ju ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 435~442
DOI : 10.5370/JEET.2010.5.3.435
This paper proposes an 18-step back-to-back (BTB) voltage source converter using four sets of 3-Level converter modules with auxiliary circuits to increase the number of steps. The proposed BTB voltage source converter has the independent control capability of active power and reactive power at the interconnected ac system. The operational feasibility of the proposed BTB converter was verified through many simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental results with a scaled hardware prototype. The proposed BTB converter could be widely applied for interconnecting the renewable energy source to the power grid.
Enhanced Proportional-Resonant Current Controller for Unbalanced Stand-alone DFIG-based Wind Turbines
Phan, Van-Tung ; Lee, Hong-Hee ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 443~450
DOI : 10.5370/JEET.2010.5.3.443
An enhanced control strategy for variable-speed unbalanced stand-alone doubly-fed induction generator-based wind energy conversion systems is proposed in this paper. The control scheme is applied to the rotor-side converter to eliminate stator voltage imbalance. The proposed current controller is developed based on the proportional-resonant regulator, which is implemented in the stator stationary reference frame. The resonant controller is tuned at the stator synchronous frequency to achieve zero steady-state errors in rotor currents without decomposing the positive and negative sequence components. The computational complexity of the proposed control algorithm is greatly simplified, and control performance is significantly improved. Finally, simulations and experimental results are presented to verify the feasibility and the robustness of the proposed control scheme.
Improved Direct Torque Control of Permanent Magnet Synchronous Electrical Vehicle Motor with Proportional-Integral Resistance Estimator
Hartani, Kada ; Miloud, Yahia ; Miloudi, Abdellah ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 451~461
DOI : 10.5370/JEET.2010.5.3.451
Electric vehicles (EVs) require fast torque response and high drive efficiency. This paper describes a control scheme of fuzzy direct torque control of permanent magnet synchronous motor for EVs. This control strategy is extensively used in EV application. With direct torque control (DTC), the electromagnetic torque and stator flux can be estimated using the measured stator voltages and currents. The estimation depends on motor parameters, except for the stator resistance. The variation of stator resistance due to changes in temperature or frequency downgrades the performance of DTC, which is controlled by introducing errors in the estimated flux linkage vector and the electromagnetic torque. Thus, compensation for the effect of stator resistance variation becomes necessary. This work proposes the estimation of the stator resistance and its compensation using a proportional-integral estimation method. An electronic differential has been also used, which has the advantage of replacing loose, heavy, and inefficient mechanical transmission and mechanical differential with a more efficient, light, and small electric motors that are directly coupled to the wheels through a single gear or an in-wheel motor.
Rotor Shape Design of an Interior PM Type BLDC Motor for Improving Mechanical Vibration and EMI Characteristics
Hur, Jin ; Kim, Byeong-Woo ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 462~467
DOI : 10.5370/JEET.2010.5.3.462
This paper presents the rotor shape optimization of an interior type permanent magnet (IPM) motor for a reduction of vibration and Electromagnetic Interference (EMI). The vibration and EMI in permanent magnet motors is generated by cogging torque ripple, radial force and commutation torque ripple. Consequently, in order to improve vibration and EMI, the optimal notches are put on the rotor pole with an arc shape proposed. The variation of vibration frequency due to the cogging torque and radial force of each model is computed by the finite element method (FEM). From the analysis result and experiment, we confirmed the proposed model has remarkably improved the vibration and EMI.
Direct Single-stage Power Converter with Power Factor Improvement for Switched Mode Power Supply
Kalpana, R. ; Singh, Bhim ; Bhuvaneswari, G. ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 468~476
DOI : 10.5370/JEET.2010.5.3.468
This paper presents a direct single-stage power converter using single-phase isolated full-bridge converter modules, with inherent power factor correction (PFC) for a 12 kW switched mode power supply (SMPS). The advantages of the proposed converter are its simple control strategy, reduction in number of conversion stage, low input line current harmonics, and improvement in power factor. Analysis of the single-stage converter is carried out in continuous conduction mode of operation. Steady-state analysis of the proposed converter is conducted to obtain converter parameters. A systematic design procedure is also presented for a 12k W converter with a design example. The effect of load variation on SMPS is also studied in order to demonstrate the effectiveness of the proposed converter for the complete range of load conditions. A set of power quality indices on input ac mains for an SMPS fed from a single-stage converter is also presented for easy comparison of their performance.
A Study on Isolated DCM Converter for High Efficiency and High Power Factor
Kwak, Dong-Kurl ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 477~483
DOI : 10.5370/JEET.2010.5.3.477
This paper is studied on a novel buck-boost isolated converter for high efficiency and high power factor. The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit makes use of a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuit and reduces a number of control components. The input ac current waveform in the proposed converter becomes a quasi sinusoidal waveform in proportion to the magnitude of input ac voltage under constant switching frequency. As a result, it is obtained by the proposed converter that the switching power losses are low, the efficiency of the converter is high, and the input power factor is nearly unity. The validity of analytical results is confirmed by some simulation results on computer and experimental results.
Introduction of the Magnetic Pulse Compressor (MPC) - Fundamental Review and Practical Application
Choi, Jae-Gu ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 484~492
DOI : 10.5370/JEET.2010.5.3.484
Magnetic switch is a kind of saturable inductor, which utilizes nonlinearity of the magnetization curve of ferromagnetic materials. The right understanding of the saturation phenomena, magnetic properties, voltage-time product, and switching characteristics of the magnetic switch is essential in designing the magnetic pulse compressor (MPC). In this paper, the historical background of research on the MPC, fundamental physical properties of the magnetic switches, and application fields of the MPC are presented. Further, an in-depth analysis of pulse compression in series and parallel MPCs is incorporated. As practical application examples, a series MPC used for water treatments and a parallel MPC used for pulsed electric field (PEF) inactivation of bacteria are cited.
ANN Modeling of a Gas Sensor
Baha, H. ; Dibi, Z. ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 493~496
DOI : 10.5370/JEET.2010.5.3.493
At present, Metal Oxide gas Sensors (MOXs) are widely used in gas detection because of its advantages, including high sensitivity and low cost. However, MOX presents well-known problems, including lack of selectivity and environment effect, which has motivated studies on different measurement strategies and signal-processing algorithms. In this paper, we present an artificial neural network (ANN) that models an MOX sensor (TGS822) used in a dynamic environment. This model takes into account dependence in relative humidity and in gas nature. Using MATLAB interface in the design phase and optimization, the proposed model is implemented as a component in an electronic simulator library and accurately expressed the nonlinear character of the response and that its dependence on temperature and relative humidity were higher than gas nature.
Numerical Study on Frequency Up-conversion in USPR using MATLAB
Roh, Young-Su ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 497~502
DOI : 10.5370/JEET.2010.5.3.497
In this paper, the O-mode ultrashort-pulse reflectometry (USPR) millimeter-wave signals that propagate into the plasma and cover a frequency bandwidth of 33-158 GHz are examined numerically using MATLAB. Two important processes are involved in the computation: the propagation of the USPR impulse signal through a waveguide and the frequency up-conversion using millimeter-wave mixers. These mixers are limited to intermediate frequency signals that are less than 500 mV; thus, it is necessary to disperse the impulse signal into a chirped waveform using the waveguide. The stationary phase method is utilized to derive a closed-form formula for a chirped waveform under the assumption that the USPR impulse is Gaussian. In the process of frequency up-conversion, the chirped waveform is mixed with the mixer LO signal, and the lower frequency components of the RF signal are removed using high pass filters.
Fuzzy Applications in a Multi-Machine Power System Stabilizer
Sambariya, D.K. ; Gupta, Rajeev ;
Journal of Electrical Engineering and Technology, volume 5, issue 3, 2010, Pages 503~510
DOI : 10.5370/JEET.2010.5.3.503
This paper proposes the use of fuzzy applications to a 4-machine and 10-bus system to check stability in open conditions. Fuzzy controllers and the excitation of a synchronous generator are added. Power system stabilizers (PSSs) are added to the excitation system to enhance damping during low frequency oscillations. A fuzzy logic power system stabilizer (PSS) for stability enhancement of a multi-machine power system is also presented. To attain stability enhancement, speed deviation (
) and acceleration (
) of the Kota Thermal synchronous generator rotor are taken as inputs to the fuzzy logic controller. These variables have significant effects on the damping of generator shaft mechanical oscillations. The stabilizing signals are computed using fuzzy membership functions that are dependent on these variables. The performance of the fuzzy logic PSS is compared with the open power system, after which the simulations are tested under different operating conditions and changes in reference voltage. The simulation results are quite encouraging and satisfactory. Similarly, the system is tested for the different defuzzification methods, and based on the results, the centroid method elicits the best possible system response.