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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 11, Issue 4 - Jul 2016
Volume 11, Issue 3 - May 2016
Volume 11, Issue 2 - Mar 2016
Volume 11, Issue 1 - Jan 2016
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Quick and Accurate Computation of Voltage Stability Margin
Karbalaei, Farid ; Abasi, Shahriar ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 1~8
It is well known that the behavior of PV curves is similar to a quadratic function. This is used in some papers to approximate PV curves and calculate the maximum-loading point by minimum number of power flow runs. This paper also based on quadratic approximation of the PV curves is aimed at completing previous works so that the computational efforts are reduced and the accuracy is maintained. To do this, an iterative method based on a quadratic function with two constant coefficients, instead of the three ones, is used. This simplifies the calculation of the quadratic function. In each iteration, to prevent the calculations from diverging, the equations are solved on the assumption that voltage magnitude at a selected load bus is known and the loading factor is unknown instead. The voltage magnitude except in the first iteration is selected equal to the one at the nose point of the latest approximated PV curve. A method is presented to put the mentioned voltage in the first iteration as close as possible to the collapse point voltage. This reduces the number of iterations needed to determine the maximum-loading point. This method is tested on four IEEE test systems.
An Accurate Model of Multi-Type Overcurrent Protective Devices Using Eigensystem Realization Algorithm and Practice Applications
Cheng, Chao-Yuan ; Wu, Feng-Jih ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 9~19
Accurate models of the characteristics of typical inverse-time overcurrent (OC) protective devices play an important role in the protective coordination schemes. This paper presents a novel approach to determine the OC protective device parameters. The approach is based on the Eigensystem Realization Algorithm which generates a state space model to fit the characteristics of OC protective devices. Instead of the conventional characteristic curves, the dynamic state space model gives a more exact fit of the OC protective device characteristics. This paper demonstrates the feasibility of decomposing the characteristic curve into smooth components and oscillation components. 19 characteristic curves from 13 typical and 6 non-typical OC protective devices are chosen for curve-fitting. The numbers of fitting components required are determined by the maximum absolute values of errors for the fitted equation. All fitted equations are replaced by a versatile equation for the characteristics of OC protective devices which represents the characteristic model of a novel flexible OC relay, which in turn may be applied to improve the OC coordination problems in the sub-transmission and distribution systems.
Generation Rescheduling Based on Energy Margin Sensitivity for Transient Stability Enhancement
Kim, Kyu-Ho ; Rhee, Sang-Bong ; Hwang, Kab-Ju ; Song, Kyung-Bin ; Lee, Kwang Y. ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 20~28
DOI : 10.5370/JEET.2016.11.1.020
This paper presents a generation rescheduling method for the enhancement of transient stability in power systems. The priority and the candidate generators for rescheduling are calculated by using the energy margin sensitivity. The generation rescheduling formulates the Lagrangian function with the fuel cost and emission such as NO
from power plants. The generation rescheduling searches for the solution that minimizes the Lagrangian function by using the Newton’s approach. While the Pareto optimum in the fuel cost and emission minimization has a drawback of finding a number of non-dominated solutions, the proposed approach can explore the non-inferior solutions of the multiobjective optimization problem more efficiently. The method proposed is applied to a 4-machine 6-bus system to demonstrate its effectiveness.
A Fault Diagnostic Method for Position Sensor of Switched Reluctance Wind Generator
Wang, Chao ; Liu, Xiao ; Liu, Hui ; Chen, Zhe ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 29~37
DOI : 10.5370/JEET.2016.11.1.029
Fast and accurate fault diagnosis of the position sensor is of great significance to ensure the reliability as well as sensor fault tolerant operation of the Switched Reluctance Wind Generator (SRWG). This paper presents a fault diagnostic scheme for a SRWG based on the residual between the estimated rotor position and the actual output of the position sensor. Extreme Learning Machine (ELM), which could build a nonlinear mapping among flux linkage, current and rotor position, is utilized to design an assembled estimator for the rotor position detection. The data for building the ELM based assembled position estimator is derived from the magnetization curves which are obtained from Finite Element Analysis (FEA) of an SRWG with the structure of 8 stator poles and 6 rotor poles. The effectiveness and accuracy of the proposed fault diagnosis method are verified by simulation at various operating conditions. The results provide a feasible theoretical and technical basis for the effective condition monitoring and predictive maintenance of SRWG.
Analysis of the Virtual Power Plant Model Based on the Use of Emergency Generators in South Korea
Chung, Beom Jin ; Kim, Chang Seob ; Son, Sung-Yong ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 38~46
DOI : 10.5370/JEET.2016.11.1.038
This study analyzes the economic efficiency of the virtual power plant (VPP) model that aims to integrate a number of emergency generators installed at the consumer end and operate them as a single power plant. Several factors such as the demand response benefits from VPP operation and costs incurred for converting emergency generators into VPP are considered to assess the economic efficiency of the proposed VPP model. Scenarios for yearly VPP conversion are prepared based on the installed capacities of the emergency generators distributed in South Korea, while the costs and benefits are calculated from the viewpoints of participants and power companies in accordance with California Test Methods. Furthermore, a sensitivity analysis is conducted on the cost factors among those affecting the economic efficiency of VPP business because these two factors have a great impact on benefits.
Reliability Evaluation of a Microgrid Considering Its Operating Condition
Xu, Xufeng ; Mitra, Joydeep ; Wang, Tingting ; Mu, Longhua ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 47~54
DOI : 10.5370/JEET.2016.11.1.047
Microgrids offer several reliability benefits, such as the improvement of load-point reliability and the opportunity for reliability-differentiated services. The primary goal of this work is to investigate the impacts of operating condition on the reliability index for microgrid system. It relies on a component failure rate model which quantifies the relationship between component failure rate and state variables. Some parameters involved are characterized by subjective uncertainty. Thus, fuzzy numbers are introduced to represent such parameters, and an optimization model based on Fuzzy Chance Constrained Programming (FCCP) is established for reliability index calculation. In addition, we present a hybrid algorithm which combines scenario enumeration and fuzzy simulation as a solution tool. The simulations in a microgrid test system show that reliability indices without considering operating condition can often prove to be optimistic. We also investigate two groups of situations, which include the different penetration levels of microsource and different confidence levels. The results support the necessity of considering operating condition for achieving accurate reliability evaluation.
Pattern Recognition of Monitored Waveforms from Power Supplies Feeding High-Speed Rail Systems
Gu, Wei ; Zhang, Shuai ; Yuan, Xiaodong ; Chen, Bing ; Bai, Jingjing ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 55~64
DOI : 10.5370/JEET.2016.11.1.055
The development of high-speed rail (HSR) has had a major impact on the power supply grid. Based on the monitored waveforms of HSR, a pattern recognition approach is proposed for the first time in this paper to identify the operating conditions. To reduce the data dimensions for monitored waveforms, the principal component analysis (PCA) algorithm was used to extract the characteristics and their waveforms from the monitored waveforms data. The dynamic time wrapping (DTW) algorithm was then used to identify the operating conditions of the HSR. Cases studies show that the proposed approach is effective and feasible, and that it is possible to identify the real-time operating conditions based on the monitored waveforms.
A Three-phase Hybrid Power Flow Algorithm for Meshed Distribution System with Transformer Branches and PV Nodes
Li, Hongwei ; Wu, Huabing ; Jiang, Biyu ; Zhang, Anan ; Fang, Wei ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 65~75
DOI : 10.5370/JEET.2016.11.1.065
Aiming at analyzing the power flow of the distribution systems with distribution transformer (DT) branches and PV nodes, a hybrid three-phase power flow methodology is presented in this paper. The incidence formulas among node voltages, loop currents and node current injections have been developed based on node-branch incidence matrix of the distribution network. The method can solve the power flow directly and has higher efficiency. Moreover, the paper provides a modified method to model DT branches by considering winding connections, phase shifting and off-nominal tap ratio, and then DT branches could be seen like one transmission line with the proposed power flow method. To deal with the PV nodes, an improved approach to calculate reactive power increment at each PV node was deduced based on the assumption that the positive-sequence voltage magnitude of PV node is fixed at a given value. Then during calculating the power flow at each iteration, it only needs to update current injection at each PV node with the proposed algorithm. The process is very simple and clear. The results of IEEE 4 nodes and the modified IEEE 34 nodes test feeders verified the correctness and efficiency of the proposed hybrid power flow algorithm.
Decision Making on Bus Splitting Locations Using a Modified Fault Current Constrained Optimal Power Flow (FCC-OPF)
Song, Hwachang ; Vovos, Panagis N. ; Cho, Kang-Wook ; Kim, Tae-Sun ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 76~85
DOI : 10.5370/JEET.2016.11.1.076
This paper presents a method of decision on where bus splitting is needed to reduce fault current level of power systems and to satisfy the fault current constraints. The method employs a modified fault current constrained optimal power flow (FCC-OPF) with X variables for the candidate locations of splitting and for decision making on whether to split or not, it adopts soft-discretization by augmenting inversed U-shaped penalty terms. Also, this paper discusses the procedure on the adequate selection of bus splitting locations based on the results of the modified FCC-OPF, to reduce the total number of the actions taken.
Hybrid Reference Function for Stable Stepwise Inertial Control of a Doubly-Fed Induction Generator
Yang, Dejian ; Lee, Jinsik ; Hur, Kyeon ; Kang, Yong Cheol ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 86~92
DOI : 10.5370/JEET.2016.11.1.086
Upon detecting a frequency event in a power system, the stepwise inertial control (SIC) of a wind turbine generator (WTG) instantly increases the power output for a preset period so as to arrest the frequency drop. Afterwards, SIC rapidly reduces the WTG output to avert over-deceleration (OD). However, such a rapid output reduction may act as a power deficit in the power system, and thereby cause a second frequency dip. In this paper, a hybrid reference function for the stable SIC of a doubly-fed induction generator is proposed to prevent OD while improving the frequency nadir (FN). To achieve this objective, a reference function is separately defined prior to and after the FN. In order to improve the FN when an event is detected, the reference is instantly increased by a constant and then maintained until the FN. This constant is determined by considering the power margin and available kinetic energy. To prevent OD, the reference decays with the rotor speed after the FN. The performance of the proposed scheme was validated under various wind speed conditions and wind power penetration levels using an EMTP-RV simulator. The results clearly demonstrate that the scheme successfully prevents OD while improving the FN at different wind conditions and wind power penetration levels. Furthermore, the scheme is adaptive to the size of a frequency event.
3D Magnetic Analysis of Permanent Magnets in Spherical Configuration
Oner, Yusuf ; Kesler, Selami ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 93~99
DOI : 10.5370/JEET.2016.11.1.093
The present study aims to increase the amount of surface flux by changing the magnetic directions of a spherical magnet (NdFeB) consisting of four poles. For this purpose, the magnetic directions of quartile spherical slices constituting the spherical magnet are manipulated and their three-dimensional analyses are carried out by using finite-element method via Maxwell environment. The analysis of the magnetic quartile spheres with four different magnetic directions are compared to the each other, and then the quartile sphere with the best surface flux distribution is suggested for rotor structure. It is clear emphasized that the induced torque of the spherical motor, in which such a rotor is used, will be improved as well.
Simple High Efficiency Full-Bridge DC-DC Converter using a Series Resonant Capacitor
Jeong, Gang-Youl ; Kwon, Su-Han ; Park, Geun-Yong ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 100~108
DOI : 10.5370/JEET.2016.11.1.100
This paper presents a simple high efficiency full-bridge DC-DC converter using a series resonant capacitor. The proposed converter achieves the zero voltage switching of the primary switches under a wide range of load conditions and reduces the high circulating current in the freewheeling mode using the leakage resonant inductance and the series resonant capacitor. Thus, the proposed converter overcomes the drawbacks of the conventional full-bridge DC-DC converter and improves its overall system efficiency. Its structure is simplified by using the leakage inductance of the transformer as the resonant inductance and omitting the DC output filter inductance. Also it can operate over a wide range of input voltages. In this paper, the operational principle, analysis and design example are described in detail. Finally, the experimental results from a 650W (24V/27A) prototype are demonstrated to confirm the operation, validity and features of the proposed converter.
Analytic Model of Four-switch Inverter-fed Driving System for Wye or Delta-connected Motor with Current Ripple Reduction Scheme
Lee, Dong-Myung ; Jung, Jin-Woo ; Heo, Seo Weon ; Kim, Tae Heoung ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 109~116
DOI : 10.5370/JEET.2016.11.1.109
This paper proposes an analytic model for four-switch inverter (FSI)-driven wye (Y) or delta (Δ)-connected motors with a current ripple reduction algorithm. FSIs employ four switches in controlling three-phase load instead of using six switches. They have split dc-link stage, and due to this inherent structure there exists the voltage difference between upper and lower capacitors, which results in distortion of the inverter output voltage. To study characteristics of FSIs, this paper presents an advanced simulation models of FSI-driven control system for 3-phase motor that can has a wire connection either Y or Δ. In addition, this paper introduces a current ripple reduction scheme that mitigates degradation of control performance due to the voltage difference between the dc-link capacitors. The validity of the proposed method and the analytic model is verified by simulations and experiments carried out with 1-HP induction machine with Y or Δ-connection
Study and Control of Photovoltaic Water Pumping System
Khlifi, Mohamed Arbi ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 117~124
DOI : 10.5370/JEET.2016.11.1.117
Solar photovoltaic pumping system is one of most important of renewable energy applications especially in rural areas. Besides, the control strategy for standalone solar pumping system based on induction motor and without DC/DC converter has been widely studied and discussed in the literature. This topology is of great concern due its economic issues, especially when a standard frequency converter (SFCs) with scalar control is used instead of a dedicated PV inverter. This paper proposes an external control module to generate SFCs frequency reference in order to ensure both maximum power point tracking (MPPT). We present method of modeling and control of photovoltaic pumping system based centrifugal pump controlled by new improved incremental conductance in order to optimize the price and operation of pumping system this MPPT algorithm have many advantages like can be eliminate proportional integral controller It is a low cost solution since it requires no additional power equipment. The induction motor driven pump that is powered by a solar array is controlled by the indirect field oriented control (IFOC). The effectiveness of the proposed approach is illustrated by simulations carried out under Matlab Software. The experimental results are compared with simulation results.
An Efficient High Voltage Level Shifter using Coupling Capacitor for a High Side Buck Converter
Seong, Kwang-Su ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 125~134
DOI : 10.5370/JEET.2016.11.1.125
We propose an efficient high voltage level shifter for a high side Buck converter driving a light-emitting diode (LED) lamp. The proposed circuit is comprised of a low voltage pulse width modulation (PWM) signal driver, a coupling capacitor, a resistor, and a diode. The proposed method uses a property of a PWM signal. The property is that the signal repeatedly transits between a low and high level at a certain frequency. A low voltage PWM signal is boosted to a high voltage PWM signal through a coupling capacitor using the property of the PWM signal, and the boosted high voltage PWM signal drives a p-channel metal oxide semiconductor (PMOS) transistor on the high side Buck converter. Experimental results show that the proposed level shifter boosts a low voltage (0 to 20 V) PWM signal at 125 kHz to a high voltage (370 to 380 V) PWM signal with a duty ratio of up to 0.9941.
Analysis of Slot Leakage Reactance of Submersible Motor with Closed Slots during Starting Transient Operation
Bao, Xiaohua ; Di, Chong ; Fang, Yong ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 135~142
DOI : 10.5370/JEET.2016.11.1.135
Generally, closed slots are adopted to reduce the water friction loss in both the stator and the rotor of water filling submersible motor due to the special environment of operation. One of the obvious differences between the traditional induction motors and water filling submersible motors is that the submersible motors only need relatively smaller starting torque. This paper aims to analyze the slot leakage reactance of water filling submersible motor during starting transient operation. An improved analytical method which considered the magnetic saturation of the slot bridge and the skin effect of rotor bars is proposed. The slot permeance factor which has a direct impact on the slot leakage reactance is calculated. Then finite element models with different stator slot types are constructed and search coils are introduced to measure the slot flux linkage. Moreover, the starting performances of the models with two typical stator slots are compared and the flux leakage characteristics are obtained. Finally, the results obtained by finite element method are very close to the results obtained by analytical method.
Half Load-Cycle Worked Dual SEPIC Single-Stage Inverter
Chen, Rong ; Zhang, Jia-Sheng ; Liu, Wei ; Zheng, Chang-Ming ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 143~149
DOI : 10.5370/JEET.2016.11.1.143
The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.
Performance Comparison of PM Synchronous and PM Vernier Machines Based on Equal Output Power per Unit Volume
Jang, Dae-Kyu ; Chang, Jung-Hwan ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 150~156
DOI : 10.5370/JEET.2016.11.1.150
This paper compares the performances of permanent-magnet synchronous (PMS) and permanent-magnet vernier (PMV) machines for low-speed and high-torque applications. For comparison with the PMS machines, we consider two types of the PMV machine. The first one has surface-mounted permanent magnets (PMs) on the rotor and the other has PMs inserted on both sides of the stator and rotor. The PMS and PMV machines are designed to meet the condition of equal output power per unit volume. We analyze the magnetic fields of the machines using a two-dimensional finite element analysis (FEA). We then compare their performances in terms of the generated torque characteristics, power factor, loss, and efficiency.
Fast Detection Algorithm for Voltage Sags and Swells Based on Delta Square Operation for a Single-Phase Inverter System
Lee, Woo-Cheol ; Sung, Kook-Nam ; Lee, Taeck-Kie ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 157~166
DOI : 10.5370/JEET.2016.11.1.157
In this paper, a new sag and peak voltage detector is proposed for a single-phase inverter using delta square operation. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on d-q transformations using an all-pass filter (APF). The d-q transformation is typically used in the three-phase coordinate system. The APF generates a virtual q-axis voltage component with a 90° phase delay, but this virtual phase cannot reflect a sudden change in the grid voltage at the instant the voltage sag occurs. As a result, the peak value is drastically distorted, and it settles down slowly. A modified APF generates the virtual q-axis voltage component from the difference between the current and the previous values of the d-axis voltage component in the stationary reference frame. However, the modified APF cannot detect the voltage sag and peak value when the sag occurs around the zero crossing points such as 0° and 180°, because the difference voltage is not sufficient to detect the voltage sag. The proposed algorithm detects the sag voltage through all regions including the zero crossing voltage. Moreover, the exact voltage drop can be acquired by calculating the q-axis component that is proportional to the d-axis component. To verify the feasibility of the proposed system, the conventional and proposed methods are compared using simulations and experimental results.
Applicability of Messenger Wire for Purpose of Lightning Protection
Seo, Hun Chul ; Han, Joon ; Choi, Sun Kyu ; Lee, Byung Sung ; Rhee, Sang Bong ; Kim, Chul Hwan ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 167~174
DOI : 10.5370/JEET.2016.11.1.167
The Korean distribution line currently consists of overhead ground wires (OHGW), overhead distribution lines, neutral wires (NW), and messenger wires (MW). The MW is installed under the NW. The lightning protection system in Korea is focused on OHGW and lightning arrester and the MW are not considered. Therefore, this paper proposes the applicability of MW for purpose of lightning protection. For this, we analyzed the effects of lightning overvoltage according to the existence of OHGW and MW and the grounding conditions of the MW in the Korean distribution system. The grounding conditions of the MW that we took into consideration were the common or separate grounding of the MW and NW. The analysis based on the equivalent circuit of the distribution pole at each condition was performed. The distribution lines and lightning were modeled using the Electromagnetic Transients Program (EMTP). For each of the installation conditions of the OHGW and MW, the various lightning conditions were simulated and analyzed for both direct and indirect lightning. The simulation results showed that, if the OHGW was not installed in the Korean distribution system, the lightning overvoltage could be reduced by the common grounding of the MW and NW.
Signal Integrity Analysis of High Speed Interconnects In PCB Embedded with EBG Structures
Sindhadevi, M. ; Kanagasabai, Malathi ; Arun, Henridass ; Shrivastav, A. K. ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 175~183
DOI : 10.5370/JEET.2016.11.1.175
This paper brings out a novel method for reducing Near end and Far end Crosstalk using Electromagnetic Band Gap structures (EBG) in High Speed RF transmission lines. This work becomes useful in high speed closely spaced Printed Circuit Board (PCB) traces connected to multi core processors. By using this method, reduction of −40dB in Near-End Crosstalk (NEXT) and −60 dB in Far End Crosstalk (FEXT) is achieved. The results are validated through experimental measurements. Time domain analysis is performed to validate the signal integrity property of coupled transmission lines.
Evaluation on the Lightning Breakdown Voltages of Palm Oil and Coconut Oil under Non-Uniform Field at Small Gap Distances
Thien, Yee Von ; Azis, Norhafiz ; Jasni, Jasronita ; Kadir, Mohd Zainal Abidin Ab ; Yunus, Robiah ; Ishak, Mohd Taufiq ; Yaakub, Zaini ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 184~191
DOI : 10.5370/JEET.2016.11.1.184
In recent years, there are a number of studies that have been carried out to explore the alternative for Mineral Oil (MO) as dielectric insulating fluid in transformers due to the increasing tight regulation on safety and environment. Vegetable oils have been identified as suitable candidate since it is biodegradable, non-toxic and high flash/fire points which ensure more in-service safety. Among the types of vegetable oils considered for transformers application are Palm Oil (PO) and Coconut Oil (CO). This paper presents an experimental study on the lightning breakdown voltages of PO and CO under non-uniform electric field based on needle-sphere electrodes configuration at 3 small gap distances. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The main focus of this study is to examine the lightning breakdown performance of RBDPO and CO under different test conditions and assess its suitability as dielectric insulating fluid in transformers. The effect of voltage polarities (positive and negative) and testing methods (rising-voltage, up-and-down and multiple-voltage) were investigated. The data obtained from all tests were analysed by Weibull distribution in order to determine the withstand voltages for each type of oils. It was found that the breakdown voltages of RBDPO and CO are comparable with MO under positive lightning impulse. Under negative lightning impulse, the breakdown voltage of MO is slightly higher than RBDPO and CO. There is no significant effect of testing methods and voltage polarities on lightning breakdown voltages of RBDPO and CO. Based on the statistical analysis, it is found that the breakdown voltages of RBDPO and CO at 1% probability are slightly lower than MO.
Application of SA-SVM Incremental Algorithm in GIS PD Pattern Recognition
Tang, Ju ; Zhuo, Ran ; Wang, DiBo ; Wu, JianRong ; Zhang, XiaoXing ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 192~199
DOI : 10.5370/JEET.2016.11.1.192
With changes in insulated defects, the environment, and so on, new partial discharge (PD) data are highly different from the original samples. It leads to a decrease in on-line recognition rate. The UHF signal and pulse current signal of four kinds of typical artificial defect models in gas insulated switchgear (GIS) are obtained simultaneously by experiment. The relationship map of ultra-high frequency (UHF) cumulative energy and its corresponding apparent discharge of four kinds of typical artificial defect models are plotted. UHF cumulative energy and its corresponding apparent discharge are used as inputs. The support vector machine (SVM) incremental method is constructed. Examples show that the PD SVM incremental method based on simulated annealing (SA) effectively speeds up the data update rate and improves the adaptability of the classifier compared with the original method, in that the total sample is constituted by the old and new data. The PD SVM incremental method is a better pattern recognition technology for PD on-line monitoring.
Stability and Robust H
Control for Time-Delayed Systems with Parameter Uncertainties and Stochastic Disturbances
Kim, Ki-Hoon ; Park, Myeong-Jin ; Kwon, Oh-Min ; Lee, Sang-Moon ; Cha, Eun-Jong ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 200~214
DOI : 10.5370/JEET.2016.11.1.200
This paper investigates the problem of stability analysis and robust H
controller for time-delayed systems with parameter uncertainties and stochastic disturbances. It is assumed parameter uncertainties are norm bounded and mean and variance for disturbances of them are known. Firstly, by constructing a newly augmented Lyapunov-Krasovskii functional, a stability criterion for nominal systems with time-varying delays is derived in terms of linear matrix inequalities (LMIs). Secondly, based on the result of stability analysis, a new controller design method is proposed for the nominal form of the systems. Finally, the proposed method is extended to the problem of robust H
controller design for a time-delayed system with parameter uncertainties and stochastic disturbances. To show the validity and effectiveness of the presented criteria, three examples are included.
Trajectory Tracking Control of a Real Redundant Manipulator of the SCARA Type
Urrea, Claudio ; Kern, John ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 215~226
DOI : 10.5370/JEET.2016.11.1.215
Modeling, control and implementation of a real redundant robot with five Degrees Freedom (DOF) of the SCARA (Selective Compliant Assembly Robot Arm) manipulator type is presented. Through geometric methods and structural and functional considerations, the inverse kinematics for redundant robot can be obtained. By means of a modification of the classical sliding mode control law through a hyperbolic function, we get a new algorithm which enables reducing the chattering effect of the real actuators, which together with the learning and adaptive controllers, is applied to the model and to the real robot. A simulation environment including the actuator dynamics is elaborated. A 5 DOF robot, a communication interface and a signal conditioning circuit are designed and implemented for feedback. Three control laws are executed in: a simulation structure (together with the dynamic model of the SCARA type redundant manipulator and the actuator dynamics) and a real redundant manipulator of the SCARA type carried out using MatLab/Simulink programming tools. The results, obtained through simulation and implementation, were represented by comparative curves and RMS indices of the joint errors, and they showed that the redundant manipulator, both in the simulation and the implementation, followed the test trajectory with less pronounced maximum errors using the adaptive controller than the other controllers, with more homogeneous motions of the manipulator.
Nowcast of TV Market using Google Trend Data
Youn, Seongwook ; Cho, Hyun-chong ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 227~233
DOI : 10.5370/JEET.2016.11.1.227
Google Trends provides weekly information on keyword search frequency on the Google search engine. Search volume patterns for the search keyword can also be analyzed based on category and by the location of those making the search. Also, Google provides “Hot searches” and “Top charts” including top and rising searches that include the search keyword. All this information is kept up to date, and allows trend comparisons by providing past weekly figures. In this study, we present a predictive model for TV markets using the searched data in Google search engine (Google Trend data). Using a predictive model for the market and analysis of the Google Trend data, we obtained an efficient and meaningful result for the TV market, and also determined highly ranked countries and cities. This method can provide very useful information for TV manufacturers and others.
Body Segmentation using Gradient Background and Intra-Frame Collision Responses for Markerless Camera-Based Games
Kim, Jun-Geon ; Lee, Daeho ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 234~240
DOI : 10.5370/JEET.2016.11.1.234
We propose a novel framework for markerless camera-based games. By using a visual camera, our method may yield robust human body segmentation with high performance comparable to the segmentation using depth cameras. The edges of human bodies are detected by subtracting gradient backgrounds, and human body regions are segmented by the operations based on mathematical morphology. Collisions between detected regions and virtual objects are determined by finding the colliding time using intra-frame positions of virtual objects. Experimental results show that the proposed method may produce robust segmentation of human bodies, thereby and the collision responses are more accurate than previous methods. Therefore, the proposed framework can be widely used in camera-based games requiring high performance.
New Permanent Magnet Synchronous Motor Current Sensing Phase Delay Compensation Method
Park, Sei-Hun ; Kim, Il-Hwan ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 241~246
DOI : 10.5370/JEET.2016.11.1.241
This paper presents a method that can improve the performance of permanent magnet synchronous motor current control by minimizing the measured current phase delay caused by the Low Pass Filter(LPF) used to cut off the noises that flowed in when feedback currents are measured. Although existing methods that change the Cutoff Frequency of the LPF can minimize phase delays during high speed rotations, their noise cutoff effects are much lower and this may lead to the decline of control performance. Therefore, in this study, an algorithm that can compensate current phase delays through relatively simple calculations from the synchronous motor d-q axis coordinate transformation matrix and the inverse transformation matrix is proposed and the validity of the proposed method is verified by comparing the waveform of the calculated current with the waveform of actual currents through simulations and experiments.
Context-Awareness Healthcare for Disease Reasoning Based on Fuzzy Logic
Lee, Byung-Kwan ; Jeong, Eun-Hee ; Lee, Sang-Sik ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 247~256
DOI : 10.5370/JEET.2016.11.1.247
This paper proposes Context-Awareness Healthcare for Disease Reasoning based on Fuzzy Logic. It consists of a Fuzzy-based Context-Awareness Module (FCAM) and a Fuzzy-based Disease Reasoning Module (FDRM). The FCAM computes a Correlation coefficient and Support between a Condition attribute and a Decision attribute and generates Fuzzy rules by using just the Condition attribute whose Correlation coefficient and Support are high. According to the result of accuracy experiment using a SIPINA mining tool, those generated by Fuzzy Rule based on Correlation coefficient and Support (FRCS) and Improved C4.5 are 0.84 and 0.81 each average. That is, compared to the Improved C4.5, the FRCS reduces the number of generated rules, and improves the accuracy of rules. In addition, the FDRM can not only reason a patient’s disease accurately by using the generated Fuzzy Rules and the patient disease information but also prevent a patient’s disease beforehand.
Steady State Analysis for Power System of HSR with Active Transformer
Kim, Wook-Won ; Kim, Hyung-Chul ; Shin, Seung-Kwon ; Kim, Jin-O ;
Journal of Electrical Engineering and Technology, volume 11, issue 1, 2016, Pages 257~264
DOI : 10.5370/JEET.2016.11.1.257
In this paper, new electric railway feeding system which has active transformer is modeled for evaluating the steady state analysis using PSCAD/EMTDC. Equivalent models including power supply, feeder, train and transformers are proposed for simplifying the model of the feeding system in high speed electric railway. In case study, simulation results applied to proposed model are compared with the conventional and new systems through the catenary voltage, three-phase voltage of PCC (Point of Common Coupling) and the efficiency of regenerative braking energy.