1999.11b
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This paper deals with the effect on the stress and deformation of the rotor bar of a cage induction motor by the thermal stress, centrifugal force and electromagnetic force. We use both the thermal network method(TNM) and the finite element method(FEM) to analyze the temperature and stress of the rotor.
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This paper presents a method to analyze a forward converter. A transformer is coupled with the forward converter electric circuit and then the finite element analysis considering a hysteresis phenomenon of magnetic core is carried out when the primary or the reset winding conducts current. The analytical method is used to reduce the computation time when the reset winding circuit of the transformer turns off. As a result, the simulation results show a good agreement with experimental ones.
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This paper presents the problems of design and theoretical model of electrostatically driven axial-gap type wobble motor. The motor design benefits from large axial rotor-to-stator overlap and large gear ratios, and motor designs with rotor radii of 50 and
$100{\mu}m$ are capable of generating torques in the [nNm] range at high electrostatic fields. Because of the large gear ratio, smaller angular steps and lower rotational speed are obtained, compared to radial-gap motor design. Aspects like gear ratio, torque generation, excitation schemes and torque coverage, normal forces, friction are addressed. -
The paper is described about the characteristics analysis of Axial Fluk Reluctance Motor(AFRM) with nonlinear analytical modeling. The parameter of the modeling is computed by the finite element method as functions of input current and angular displacement. To investigate the dynamic characteristics of AFRM, the current, torque, back EMF and output power wave is simulated from the motion equation by MATLAB/Simulink.
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This paper proposes that optimal design using GA of BLDC motor. To estimate this optimal design method, the performance characteristics of BLDC motor is computed by the equivalent magnetic circuit network method and FEM. To estimate especially the dynamic characteristics of BLDC, we compute the parameter of electrical circuit using FEM.
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In this paper, the space mapping algorithm is proposed for the design of electric machines. By the algorithm, we can combine the magnetic equivalent circuit and the finite element models mathematically and got the final design parameters with a few iterations while preserving the accuracy offered by the finite element model. The finite element model is generated by parametric techniques. For the validity of this algorithm, a simple permanent magnet device with fringing and leakage flux is dealt as a numerical example.
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In this paper, the analysis of the electric field in the chamber of high voltage
$SF_6$ GCB(Gas Circuit Breaker) is presented by using C-1 FEM. For this purpose, pre-processing program and post-processing program were developed for axisymmetirc 3 dimensional analysis and the electric field in cylindric chamber was analyzed. Important problem is that electric analysis must be considered coronal due to break-down of$SF_6$ when it is cutted off. To solve this problem, a procedure is needed to verify that the solution of Poisson's equation for scalar potential satisfy charge continuos condition because of using first order element os not satisfy the electric continuous condition, C-1 FEM is introduce to obtain electirc potential and electric field at the same time. Analysis of the distribution of electric field on model was done. It is confirmed that the developed program in this paper applicable to design and to analyze of characteristics in total program as electric characteristics analysis routine. -
In this paper, the conceptual design and FE analysis results of salient pole type alternator under no load condition are described. The designed alternator's rating is 180kW, 3-phase, 4pole, 380/220V, 0.8pf, 60Hz. The conceptual design is described by the process of designing the armature, field, and obtaining some of equivalent circuit parameters. The comparison of FE analysis to the designed results of alternator's output voltage value shows a good agreement.
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The starting characteristics of induction motors strongly depend on the leakage reactance and resistance of stator winding and rotor circuits. The magnetic field saturation in the rotor bridge of closed slot rotor makes it very difficult to compute the leakage reactance of rotor bars. This paper describes a comparison between timestep finite element analysis, time-harmonic analysis and experimental results for a test model which can represent the nonlinear behaviour of the rotor bridge.
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This paper describes the test results of the single phase 3kVA high temperature superconducting power trans-former. The tapes are made with Bi-2223 and have silver alloy as the matrix. Four double pancake windings are used in total. Among them two double pancake windings are connected in series for high voltage winding and two double pancake windings are connected in parallel for low voltage winding. The rated voltages of each winding are 220/110 V. Fundamental characteristics are obtained through short circuit and no load tests. The over load capability and characteristics are investigated.
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In this paper, light-weight system of linear induction motor(LIM) for light railway train is presented, and is compared with former type of LIM. For the light-weight system without modification of motor size the material of primary core(silicon steel) is changed with iron-cobalt alloy and the material of primary winding(copper) is changed with aluminium. The characteristics of LIM are analyzed. Specially, the air gap magnetic flux density distribution due to end effect is showed with motor velocity, we will present papers continuously through designing and testing a trial product.
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This paper is presented about the development of magnetic levitation conveyor with a transverse flux linear synchronous motor (TFLSM). The TFLSM is proposed as the new type linear motor for the conveyor driving system. The flux density distribution. the thrust and etc. of TFLSM are analyzed by the finite element method. To analyze the dynamic characteristics of TFLSM, the parameter of equivalent circuit is calculated by the analytical method.
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This paper presents the design and characteristics analysis of a linear induction motor applied to molten metals. A linear induction motor is designed to increased to thrust and is applied to the experimental instrument. The experiment shows the availability of the LIM for transferring the molten metals.
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The direct thrust control of permanent magnet linear synchronous motor using digital signal processor (DSP) is presented. The motor self inductance, the initial flux linkage by the permanent magnet is calculated in advance by the finite element analysis. The equivalent circuit method and the digital signal processor are used for the simulation and experiment, respectively. The simulation and experimental results such as, thrust, current and speed responses to the commands are examined.
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This paper presents the results of monitoring for measuring characteristics of Linear induction motor. The results is divided into three parts, that is part for electrical quantity caculation, thrust caculation and speed decting part. Also, for the purpose of measuring the characteristics of LIM, LabVIEW software is used.
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To control induction motor we have to know about dynamic characteristics including torque characteristic. Simulation and test were made to get dynamic characteristics using LabVIEW and Matlab. We got experimental results(e.g current, torque, speed etc) from starting to steady state with changing of load.
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In the industrial field the necessity of the linear motion is increasing. We selected a moving magnet coreless type LDM, which have the advantages, such as long stoke, brushless, no cogging force. Actually, the design is accomplished using FEM analysis for the basic configuration of a magnetic circuit, and characteristic equations for coil design. In the course of design, we have estimated airgap flux density and thrust. We fabricated coreless type LDM and experimented static test. We compared measurement values with FEM analysis values.
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This paper reports analysis and test results on the new type Linear Oscillatory Actuator(LVDT actuator) which has been expected to be applied not only to measure position but also to drive as an actuator at the same time.
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High-speed motors using permanent magnet have various merits; high efficiency, high power density, and small size. While they have merits, we have to solve some problems. First of all, we have to reduce loss, cause of heat, to realize high speed operation. The loss be composed of copper loss, iron loss, and parasitic rotor loss. Iron loss and parasitic rotor loss is proportional to frequency, square of frequency, respectively.
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Choi, T.I.;Kong, Y.K.;Kim, H.C.;Kim, C.L.;Song, J.H.;Hong, S.Y.;Kim, B.S.;Jung, Y.B.;Choi, K.H. 67
ADD is under development for the high speed motor. This paper describes the test results for obtaining the maximum output by leading angle of encoder. So we carried out the test for obtaining the optimum leading angle of encoder. Maximum output 80[Kw] at 20,000[rpm] was obtained at leading angle of encoder at near$22^{\circ}$ . We confirmed the maximum output 106[kw] of 25,000[rpm] at leading angle of encoder at$34.6^{\circ}$ . -
Actuator (chopper) and sensors failures resulting from electric shock and mechanical vibration generating by rail irregularities are the serious problem deteriorating the performance in the electromagnetic suspension systems. Thus, this paper proposes the reliable output feedback controller for the electromagnetic levitation systems against actuator, air-gap sensor and acceleration sensor failures. The designed controller is an extend version of a novel design technique which has the design method of the output feedback controller using dynamic compensator. The benefits of this scheme are demonstrated through the experimental results for the proposed controller against chopper, air-gap sensor and acceleration sensor failures of electromagnetic levitation system.
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The performance of a SRM in terms of torque and power factor depends on the two-axis inductances (Ld and Lq) and iron loss of the machine. Finite element method has been used to determine these parameters for a motor with segmented rotor structure. Fock and Hart Method has been conducted to compare to verify the accuracy of proposed analysis method.
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In this paper, the 2-phase excitation method is proposed to reduce vibration and noise. This excitation method produces reluctance torque by mutual action between two phases as well as conventional-reluctance torque due to two phases excitation at a time. The vibration and acoustic noise is reduced thought the sequential phase excitation. This is because that the scheme reduces abrupt change of excitation level by distributed. balanced excitation.
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In this paper, STATCOH(static synchronous compensator : one of the custom power equipment) is proposed for balancing unbalanced loads. Compensation current references are given by the analysis of the unbalanced 3-phase currents. And for detecting negative-sequence components, digital Butterworth LPF(low pass filter) is used. The predicted current controller in the synchronous rotating coordinates is also proposed. Finally, the effectiveness of STATCOM is verified by the simulations for unbalanced loads.
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Recently, a rapid increase of electricity demands have made Transmission & Substation device large-sized. complicated and diverse. Moreover, a rising level of customer's requirement and high growth of industry increase the reliability of electricity service. Therefore on the basis of the case study on the occurrence of fault, the prevention of defects for each device and the analyzing of the outbreak and prevention of systematic breakdown in Sin-Incheon Power Transmission Branch Office, this paper presents some important matters and suggests the method of improvement in design, construction, maintenance, and repairing the Transmission & Substation device.
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We investigated the current limiting characteristics of resistive and inductive SFCLs with
$100{\Omega}$ of quench impedance for a line-to-line fault in the 154 kV transmission system. The fault simulation at the phase angles$0^{\circ}$ ,$45^{\circ}$ , and$90^{\circ}$ showed that the resistive SFCL limited the fault current less than 15 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppressed the current below 13 kA, but with$2{\sim}3\;kA$ of DC component which decreased to zero in 6 cycles. We concluded that the inductive SFCL had higher performance in current limiting but the resistive SFCL was better from the view point of DC components. -
The use of electronic power unit essentially result in serious problems by harmonics. To reduce the effect by harmonics, we propose passive filter system which can control each harmonic filters individually. So, additional devices to detect and analyze harmonics were installed to filter system. According to measured data in the field, we calculated the values of filter components and verified them by computer simulation. After installation of filter system in the field, we could reduce harmonics and improve power factor.
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This paper describes axial magnetic field characteristics of multipolar axial magnetic field type electrodes for vacuum interrupter used in vacuum circuit breaker. It was distinguished that axial magnetic field distribution in consideration of eddy current effect between electrodes by finite element method. Throughout experiment of magnetic field measurement, confirmed validity of numericla analysis.
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This paper describes electromagnetic repulsion force of multipolar axial magnetic field type electrodes for vacuum interrupter used in vacuum circuit breaker. It was distinguished that repulsion force of multipolar axial magnetic field type electrode in consideration of eddy current effect between upper electrode and lower electrode by finite element method. And it was found out that suitable contact weight of multipolar axial magnetic field type electrode for vacuum circuit breaker from repulsion force analysis results by finite element method.
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A thermal analysis was performed for the electromagnet which is installed in the control element drive mechanism(CEDM) of the integral reactor SMART. A model for the thermal analysis of the electromagnet was developed and theoretical bases for the model were established. It is important that the temperature of the electromagnet windings be maintained within the allowable limit of the insulation, since the electromagnet of CEDM is always supplied with current during the reactor operation. So the thermal analysis of the winding insulation which is composed of polyimide and air were performed by finite element method. The thermal properties obtained here will be used as input for the optimization analysis of the electromagnet.
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This paper presents an analysis of 2-dimensional(2-D) multi-regions problem using boundary integral equation method(BIEM). When compared with finite element method(FEM), there are only a few unknown variables in BIEM because it implements numerical analysis only for the surface or boundary of a model. As a result, a lot of computational memory and time can be saved. Procedure to analyze 2-D multi-regions problem using potentials and its derivatives in a boundary as unknown variables, first, numerical analysis is performed for each of subregions. And then interface continuity condition is applied to the interface between them and Gauss Quadrature Formula are adopted to solve singular integral in a boundary in this paper.
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In the point of view protective relay, the selectivity and sensitivity is very important in its performance. The correct setting of the relay parameter is required. The verification of accurate setting for the protective relay is very difficult before a actual fault occurs. In this paper, we proposed the diagnosis expert system as a method to verify the correctness of the relay setting. The developed system proved effectiveness through the tests on the real systems.
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Recently the substation automation is actively researched at each country. Since the substation automation is an integrated system that consist of electrical, electronic and computer technologies, performance evaluation is very important to inspect the developed system's applicable possibility for real power system. Most studies are verified using computer simulation, because it is hard to apply them to real power systems. Therefore development of a substation simulator is necessary for the performance evaluation of many application systems such as operator aid system. This paper introduces a substation simulator. An intelligent fault diagnosis and restorative control expert system is also introduced UDP/IP is applied as a protocol for data transport between expert system and SC(station computer). As to the Graphic User Interface, C++ Language and Visual Basic is used in the Windows NT operating system together with four Pentium II systems.
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A more reliable relaying algorithm for detecting a high impedance fault (HIF) requires fault currents at the relaying point containing information of various HIF characteristics as well as load conditions. As HIF characteristics, there are buildup, shoulder, nonlinearity and asymmetry. This paper presents a modeling method of a HIF in a distribution system using EMTP. In order to represent HIF characteristics, the proposed method uses two time-varying resistances. The first TVR models nonlinearity and asymmetry using voltage as the input. The second TVR models buildup and shoulder using time information as the input. The proposed method is implemented in EMTP.
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A fault location algorithm that is suitable for parallel transmission line which contains a teed circuit is presented. The method uses only the local end voltage and current signals. Zero sequence currents of other lines are calculated by distribution factors, and distance equations are solved by recursive calculation.
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송전선의 고장은 다양한 형태를 가지며 전체 계통의 안정적인 운용을 위하여 신속하고 정확한 고장제거가 요구된다. 송전선로용 보호제어유니트는 계측, 감시, 보호, 제어, 통신, 자기진단, 기록 등의 기능을 종합 수행하는 디지털 보호계전장치이다. LG산전에서는 축적된 기술을 바탕으로 장기적인 투자와 시행착오를 거쳐 선진 외국제품과 경쟁할 수 있는 제품을 개발하였다. 개발된 보호제어유니트는 VME BUS를 기반으로 한 프로세서부, 입출력부, 표시조작부, 전원부로 구성되며, 사변형 거리계전요소를 기본으로 과전류요소, 자동재폐로요소, 동기탈조 보호요소와 같은 기본기능 외에 많은 기능을 내장하였고, 자기진단기능, 이벤트/고장기록기능 등과 같은 기타기능들로 구비하였다.
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현형 가공배전선로의 가선공법은 많은 인력이 동원되어 매전선마다 롤러에서 푸는 연선과정과 이도를 조정하는 긴선과정을 거쳐 설치된다. 따라서 이 같은 공법은 원시적이고 비효율적인 방법이므로 이를 개선하여 일시에 다선을 신설 또는 철거시공할 수 있는 공법을 개발하여 신기술로 지정받은 바 있어 이의 개요 및 작업과정과 예상효과를 소개하고자 한다.
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We generally use Yes-No algorithms for feeder automation algorithm. This logic determines the faulty section by fault current detection information of the fault indicators of each switches in distribution feeder. This paper presents the data acquisition method such as breaker's open status in fault and the determination method of faulty section using fault indicator's information of each switches.
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This paper proposed the technique of the fault-types classification using Adaptive Network Fuzzy Inference System in the distribution system. Fault and fault-like data in the linear RL load, arc furnace load and converter load were extracted by EMTP. These were characterized into 5 input variables and fuzzified automatically by learning. This technique was tested using another fault data unused learning.
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Not much work has been carried out on the load flow analysis of distribution networks. This paper introduces Newton-Raphson method using Distflow equation and Forward Sweeping method in the distribution networks. And that efficient solution scheme in a radial distribution network is presented. Also, simulation results of both Newton-Raphson method and Forward Sweeping method applied to a 22.9kV distribution system model with 120 load buses are analized and evaluated.
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This paper presents an application of the Genetic Algorithms(GA) to solve the optimal routing problem(ORP) in power distribution system planning. Since the ORP is, in general, modeled as a mixed integer problem with some various mathematical constraints, it is hard to solve. In this paper, a new approach was made using the GA method for the ORP to overcome the disadvantages which many conventional methods generally have. For this approach, proposed was in this study a appropriately designed fitness function suited for the ORP. The proposed algorithm has been tested in sample network and the results are presented.
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Jeong, S.H.;Kim, D.K.;Choi, S.B.;Bae, J.H.;Ha, T.H.;Lee, H.G.;Jang, Y.S.;Kang, S.C.;Kim, T.H. 141
This paper has studied on a calculating method of a current carrying capacity considering the temperature-dependent factors in underground distribution cables and proved its efficiency of the temperature equation. -
This paper provides an analysis of the effect of input signals, such as acceleration power and generator shaft speed for improving Power System Stabilizer(PSS) efficiency. We consider a single machine and infinite bus system which is modeled by PSCAD/EMTDC. We choose an optimum stabilizer gain with respect to eigenvalue analysis and transient stability analysis to each input signal.
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This paper deals with the determination of generator/exciter model parameters for a Cheju Hanlim steam turbine unit. Using the recorded data from the generator characteristic tests, the model parameters have been derived and verified by comparing the simulation results and recorded data. In addition to it, the closed-loop performance of voltage control on no-load condition has been assessed in the frequency domain by taking advantage of derived generator/exciter model parameters.
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This paper presents a new generator grouping method for speed-up of transient stability evaluation in SIME. The critical generators are grouped by new indices in the early stage of time domain simulation. And the simulation can be early terminated by fast stability evaluation using the time trajectory of equivalent one machine infinite bus. The main advantage of the proposed method is that it can be applied to stable cases as well as unstable ones. The effectiveness of the proposed method is tested on the PSS/E test system.
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In this paper, we design a GA-fuzzy precompensated PID controller for the load frequency control of two-area interconnected power system. Here, a fuzzy precompensated PID controller is designed as a fuzzy logic-based precompensation approach for PID controller. This scheme is easily implemented simply by adding a fuzzy precompensator to an existing PID controller. And we optimize the fuzzy precompensator with a genetic algorithm for complements the demerit such as the difficulty of the component selection of fuzzy controller, namely, scaling factor membership function and control rules.
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This paper presented design of an
$H_{\infty}$ controller for TCSC to enhance the damping of an inter-area oscillation in KEPCO power system. TCSC location is selected by using eigne sensitivity and frequency response. Nonliner time simulation and eigenvalue analysis show that the proposed TCSC$H_{\infty}$ controller can suppress the inter-area oscillations efficiently with induced reduction model correctly. -
This paper presents an optimal design method for fuzzy controllers of HVDC system using adaptive evolutionary algorithm(AEA). We have proposed an adaptive evolutionary algorithm which uses a genetic algorithm and an evolution strategy in an adaptive manner in order to take merits of two different evolutionary computations. AEA is used for tuning fuzzy membership functions, scaling constants and PD gains. The simulation results show that the disturbances are well damped by both controllers and the dynamic performances of fuzzy controllers have better responses than those of PD controllers when mechanical torque changes suddenly.
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This work presents the performance characteristic of digital watthour meter under the harmonics of voltage and current. Each waveform involved is different in magnitude phase, and THD(Total Harmonic Distortion). It is possible to generate harmonics and control those waveforms using RTDS(Real Time Digital Simulator). Tests were performed on a selected sample of three-phase digital watthour meter which is coupled with data acquisition system via RS 485/232 converter. The percentage error rate of the watthour meter is compared for both sinusoidal and nonsinusoidal cases and the results are given.
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본 논문은 End-Use 모델의 개념을 정립하고 정화한 데이터를 얻기 위한 설문 조사를 통하여 1999년의 실제 하계 냉방부하를 End-Use 모델을 이용하여 예측하였다. 본 연구를 통하여 에어컨 부하 및 소비행태의 조사에 의한 냉방부하의 특성을 분석하고 합리적인 수요관리를 위한 냉방기기 및 부하 데이터를 축적하고자 한다.
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This paper presents a new demand control technique using fuzzy logic. Generally, predictive demand control method often brings about a large number of control actions and undesirable alarm during the beginning stage of the demand period. To solve this problem, a fuzzy predictive algorithm is proposed. The main idea of the method is the determination of sensitivity factor by using fuzzy logic. The performance of the proposed algorithm is tested through a case study.
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In Korea, the consumption of renewable energy among primary energies has marked only 1.03%, composed of mostly hydro power facilities, as of 1998. This situation has been basically due to the market limit and high generation cost of renewable energies. Furthermore, the policies and strategies for promoting the renewable energy have been insufficient in comparison with that of the developed countries. This paper mainly focuses on the economic feasibility and sensitivity analysis for renewable energies.
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This paper presents a prototype of visualization MMI of the Power System Phenomenon, specially synchronous machine dynamics and frequency deviations of power system for KEPCO's Enhanced Power System Simulator(KEPS)[1]. And some visualization designs of the Power System Phenomenons such as voltage stability, transient stability, SSR, Line overflow, and voltage deviations are presented. The prototype MMI has included the animations & 3D graphics presentations for synchronous machine rotor deviations and frequency deviations. So, a user can intuitively acquire the basic concepts of the power system oscillations. Finally, it will be scheduled to development of the various visualization MMI of the power system phenomenons for development and installation of KEPS.
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본 연구는 발전소의 신뢰도 산정을 보다 정확히 하기 위한 기초를 마련하기 위해 수행되었다. 많은 설비들로 구성된 발전소의 전체 신뢰도 계산에 대한 정확한 이론체계가 아직까지 확립되지 않았고 고장의 발생빈도도 적어 신뢰도 분석의 정확도에 한계가 있다. 또한 발전소의 기기수리 및 정기적인 전체정비가 신뢰도에 미치는 영향도 신뢰도 산정시 고려해야한다. 본 연구에서는 전형적인 국내발전소의 실제 고장정지와 수리 데이터에 기초하여 발전소의 고장시간 분포와 수리시간 분포 분석의 예를 보였고 적은 표본수로도 분포 parameter들의 계산이 가능한 Weibull 분포의 적용 가능성을 제시하였다. 또한 고장수리 및 전체정비가 신뢰도에 미치는 영향을 반영하기 위해 stochastic renewal process에 기초한 availability의 적용을 제안하고 그 예를 보였다.
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As one of ancillary services, voltage support and reactive power service should be compensed properly for its contribution. In this paper, a cost-based reactive power planning is presented. which minimizes the total cost of reactive power support of generators and VAR compensation facility installation. Reactive power support of generator is evaluated by the opportunity costs of reduced energy sale considering the varying SMP(system marginal price) in power market, Gradient projection method is applied to solve this reactive power planning using IEEE14 bus system.
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This paper presents a method for security constrained optimal reactive power planning in electric power systems. This method deals with corrective mode optimal reactive power dispatch in each (n-1)contingency system state and determination of the location and amount of reactive sources in preventive mode. In this paper the proposed scheme uses Benders decomposition method to determine the proper amount and location of reactive support in order to maintain a proper voltage profile and minimize active power transmission losses. This method is tested on IEEE 30 bus test system to prove effectiveness.
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Accurate load models allow more precise calculations of power system stability, This paper presents new static voltage stability index considering the load models. Also, We apply the load models for the existent voltage stability indices, and evaluate them.
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This paper presents an algorithm for optimal reactive power dispatch problem based on genetic algorithm. Optimal reactive power dispatch is particularized to the minimization of transmission line losses by suitable selection of generator reactive power outputs and transformer tap settings. To attain for the objective, in this paper, loss re-distribution algorithm(LRDA) is applied to ORPD. The proposed method has been evaluated on the IEEE 30 bus system. Results of the application of the method are compared with a simple genetic algorithm.
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This paper presents a new systematic contingency selection and screening method for transient stability. The variation of modal synchronizing torque coefficient(MSTC) is computed using eigen-sensitivity analysis of the electromechanical oscillation modes in small signal stability model and contingencies are ranked in decreasing order of the sensitivities of the MSTC(SMSTC). The relevant clusters are identified using the eigenvector or participating factor. The proposed algorithm is tested on the KEPCO system. Ranking obtained by the SMSTC is consistent with the time simulation results by PSS/E.
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This paper deals with optimal power flow, which is optimal problem with equality constraint and inequality constraint. A algorithm of changing two constraints problem to one constraint - equality constraint problem - that make it analytical access for optimal power flow is presented.
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This paper describes the optimization problem of real power rescheduling and present an algorithm based linear programming for studying the load-shedding and generation reallocation problem when a portion of the transmission system is disabled and at power flow solution cannot be obtained for the overload of some lines. And in case initial is infeasible, solution could not be converge. So this paper gives an algorithm being lie infeasible quantities within limit. The paper describes a LP-based algorithm to obtain the solution in power dispatch related to overload situations in power system and it is easily extened under various objective. The optimization procedures is based in linear programming with bounded variables and use the multi-segment curve method for a objective function and the validity of the algorithm is verified with two examples : 10-bus system and 57-bus system.
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The unit commitment is an important problem of production scheduling which determines the generating unit to in service(on/off) during scheduling period, to meet system demand and reserve requirement at minimum cost. This paper presents an box type crossover to improve searching ability of GA, to solve unit commitment problem. Satisfactory results are obtained by GA with the proposed crossover operator.
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This paper presents an improved method of calculating the penalty factors for economic load dispatch based on B-coefficient and AC load flow and their performance comparison. The algorithm for calculating B-coefficients by Meyer is improved and its performance is compared with that of AC load flow. The B-coefficient method is superior to the load flow method in its simplicity and computation speed. However accuracy of the B-coefficient method is not satisfactory when it is applied to the ill-conditioned systems where generators produce excessive reactive power.
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This paper proposes a novel wavelet transform based technique for prediction of System Marginal Price(SMP). In this paper, Daubechies D1(haar), D2, D4 wavelet transforms are adopted to predict SMP and the numerical results reveal that certain wavelet components can effectively be used to identify the SMP characteristics with relation to the system demand in electric power systems. The wavelet coefficients associated with certain frequency and time localisation are adjusted using the conventional multiple regression method and then reconstructed in order to predict the SMP on the next scheduling day through a five-scale synthesis technique. The outcome of the study clearly indicates that the proposed wavelet transform approach can be used as an attractive and effective means for the SMP forecasting.
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This paper presents a transmission cost allocation through application of a new reliability index in transmission pricing in competitive electric industry. The proposed method allocates a fair use of transmission system charge given separately to individual generator by capacity usage, based on the contribution of individual generator considering N-1 contingency in reliability margin of transmission capacity, and offers more alternatives of pricing in using transmission capacity and transmission margin.
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This paper presents an advanced virtual lecture system for power system which is based on web. So far, conventional web-based virtual lecture systems which simply would use hyper-text couldn't use characteristics of multimedia in web. Comparing with printed publication, such conventional virtual lecture systems as only display on monitor couldn't be superior in validity and effectiveness. So, in this paper the proposed virtual lecture system uses web-based multimedia functions, including lecture-note and AOD(Audio on Demand), in order to overcome an individual difference of learning efficiency and suggests simple simulation programs for lecture contents which can be performed directly in on-line.
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HVDC(High Voltage Direct Current) transmission system was constructed between Cheju island and mainland Haenam and has been operating commercially since 1998. But research activities in this area are not so much. That is caused by the facts that HVDC is large scale system and it is not so easy to implement and to test. Though such simulation tools as RTDS(Real Time Digital Simulator) and EMTDC can be useful, these have limitations for actual control and protective system design. Therefore scaled-down HVDC model was developed for the purpose of researches at operating technique, control and protection methods. The design of this model was based on real Cheju-Haenam HVDC system. And additionally faults simulator such as ground fault, short-circuit and change of impedance in transmission line is equipped for analysis of these faults. Control system of the model was implemented fully digitally. So it is very easy for the researchers to develope control and protection algorithm and to test the performance.
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This paper presents the surges response of the grounding systems using frequency domain electromagnetic field analysis software package. The frequency and time domain performance of a building grounding systems subjected to a lighting strike is described and discussed. The computed scalar potentials is presented graphically as a function of spatial coordinates. A double exponential lighting surge current is injected at one corner or the building grounding systems. Time-variant response of rod, mesh and kit grounding systems under impulse currents have been obtained. This paper deals with the results of studies on the time variation of ground resistance in three grounding systems.
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This paper presents a dynamic simulation algorithm for studying the effect of Unified Power Flow Controller(UPFC) on the low frequency power system oscillations and transient stability studies. The algorithm is a Newton-type one and gives a fast convergence characteristics. The algorithm is applied to inter-area power oscillation damping regulator design of a sample two-area power system. The results show that UPFC is very effective for damping inter-area oscillations.
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This paper deals with electromagnetic transient modelling of wind power system embedded in distribution networks. Wind power system consists of induction generator link reactor, distribution line, and controlled load unit. The introduction of embedded wind power system presents a new set of conditions to networks both with respect to power quantify needed to be transported and power quality such as sag swell, very short interruption, and flicker. This paper investigates the transient behavior of voltage, frequency, and load flow in wind driven induction generation system embedded in distribution networks.
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This paper presents a HNN(Hopfield Neural Network) model to solve the ORP(Optimal Routing Problem) in DSP(Distribution System Planning). This problem is generally formulated as a combinatorial optimization problem with various equality and inequality constraints. Precedent study[3] considered only fixed cert, but in this paper, we proposed the capability of optimization by fixed cost and variable cost. And suggested the corrected formulation of energy function for improving the characteristics of convergence. The proposed algorithm has been evaluated through the sample distribution planning problem and the simmulation results are presented.
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This paper presents a model and analysis results of 3 phase utility interactive photovoltaic power generation system. The control system is composed of feed forward, feedback and PID system. The voltage source inverter system provides sinusoidal PWM at current for the loads of utility system. A phase to ground fault and 3 phase fault are analyzed, and the results are discussed.
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This paper proposes a novel wavelet transform and Kohonen neural network based technique for short-time load forecasting of power systems. Firstly. Kohonen Self-organizing map(KSOM) is applied to classify the loads and then the Daubechies D2, D4 and D10 wavelet transforms are adopted in order to forecast the short-term loads. The wavelet coefficients associated with certain frequency and time localisation are adjusted using the conventional multiple regression method and then reconstructed in order to forecast the final loads through a four-scale synthesis technique. The outcome of the study clearly indicates that the proposed composite model of Kohonen neural network and wavelet transform approach can be used as an attractive and effective means for short-term load forecasting.
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This paper proposes a novel wavelet transform based algorithm for the seasonal load forecasting. In this paper, Daubechies DB2, DB4 and DB10 wavelet transforms are adopted to predict the seasonal loads and the numerical results reveal that certain wavelet components can effectively be used to identify the load characteristics in electric power systems. The wavelet coefficients associated with certain frequency and time localization are adjusted using the conventional multiple regression method and then reconstructed. In order to forecast the final loads through a four-scale synthesis technique. The outcome of the study clearly indicates that the wavelet transform approach can be used as an attractive and effective means of the seasonal load forecasting.
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The problem of small-signal stability is usually one of insufficient damping of system oscillations. The use of power system stabilizers to control generator excitation system os the most cost effective method of enhancing the small-signal stability of power system. This paper presents the fuzzy type stabilizing controller to damp out the sustained oscillation, which is observed in normal operation. through the comparative simulation with PI type power stabilizer under various system operating condition, the efficiency of fuzzy stabilizing controller with respect to nonlinear power system is verified.
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본 논문에서 제안된 조류계산 알고리즘은 Jacobian의 off-diagonal 부 행렬을 완전히 무시하는 Decoupled Load Flow(DCL) 알고리즘들의 유연한 대안으로 반복(iteration)당 최소한의 추가 계산 부담으로 Jacobian의 off-diagonal 부분의 효과를 부분적으로 반영함에 의해 수렴 특성을 향상시킬 수 있다. 제안된 방법들은 특히 Fast Decoupled Load Flow(FDL)로 대표되는 DCL들의 수렴특성이 불안정해질 경우, 효과적으로 수렴특성을 향상시킬 수 있다. 제안된 알고리즘들은 Newton-Raphson Load Flow(NRL) 방법에서 Jacobian의 off-diagonal 부분의 효과를 점진적으로 제거하는 방법으로 유도하였고, 간략화 과정에서는 Neuman series expansion을 사용하였다. 실험결과 제안된 알고리즘들은 반복횟수와 전반적인 수렴 속도에서 확실한 성능향상을 보여주었다. 제안된 알고리즘들은 특히 DCL의 수렴성능이 문제가 있을 시 full NRL 대신에 적용할 수 있는 가능성이 있어 조류계산 시간을 단축해 줄 수 있을 것으로 기대된다.
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This paper presents the basic tuning method for PSS control parameters. This method includes the phase compensation and root-locus based gain tuning for one machine with infinite bus system. At the tuning condition and least stable condition, the effect of gain tuning is also discussed.
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Fault location algorithms based on the current distribution factors under the one-phase to earth fault condition of a double-circuit line are presented. The derivation method for current distribution factors is showed, to calculate fault current, fault resistance and the zero sequence current of other parallel circuit which are unknown. As the proposed algorithms 1,2,3 embodies an accurate location by the voltage and the current of the relaying point.
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The Single Machine Equivalent(SIME) is a hybrid method resulting from the coupling of a time-domain program with the equal-area criterion. This paper presents the efficient filtering algorithm using improved SIME for Transient Stability Assessment. The main feature of the method is cascading contingency filtering. First contingency filtering is conducted by using the first-swing stability of equivalent One Machine Infinite Bus(OMIB) system. This stability is evaluated by checking its time trajectory. Selected cases through the first step are assessed on the second step using SIME under the detailed model of power systems. The efficiency of the algorithm is tested on PSS/E test system.
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This paper presents approaches for optimum rebate level of DSM programs to improve the rebate system and establish the systematic DSM plans. For an effective supply of DSM programs, it is very important to determine the rebate level of DSM programs. Customer's adoption of DSM programs is changed according to the rebate level. The case study shows the approaches and analysis methods to determine the optimum rebate level of the efficient lamp apparatus(electronic ballasts) in commercial sector.
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본 논문에서는 한전의 전력 계통 시뮬레이터(KEPS)에서 수행되어질 2010년 한전 계획 계통의 축약 계통을 자동으로 구성하는 프로그램의 개발에 대한 연구를 기술하였다. 먼저 한전 계통의 계통 데이터의 효율적인 관리를 위하여 데이터베이스를 구축하였고, 이를 이용하여 원계통의 데이터를 입력받아서 축약 계통의 데이터를 생성해내는 동적 축약 프로그램을 개발하였다. 동적 축약 프로그램은 각 발전기들의 특성을 분석하여 그룹화하는 식별부분과 이러한 식별과정을 거쳐서 구성된 발전기 그룹을 합쳐서 등가발전기로 구성하는 통합부분으로 이루어져 있으며 식별과정의 결과를 파일로 출력해내고 이를 수정할 수 있도록 하였다. 생성된 축약 계통과 원계통에 대해 조류 계산 및 동적 모의를 시행하여 그 응답특성을 비교하였다.
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One of the main jobs of the operators is to make it sure to have a service continuity in a fault situation. This paper proposes a restoration index which indicates the restoration capability of the feeder in case of a fault. A necessary and sufficient condition for a feeder to have 100% restoration of the outage is also described.
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As the power system automation, especially the substation automation is currently a major issue, it has been widely studied. Since a measured value usually has an error that results in the communication process and the characteristics of a measurement device mainly depending on the reliability. The accuracy and reliability of measured values at a substation is an important factor for substation automation. In this paper, a state estimation algorithm is proposed for domestic 154kV/22.9kV distribution substations, and the results showed promising application.
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This paper presents a dynamic equivalencing method in large electric power system for stability analysis. This method of modeling simplified equivalents for parts of the network outside the study area is to evaluate the stability of a study area modeled in detail. Generators are closely coupled in an electrical sense tend to swing together in groups during disturbances, and this behavior can be exploited to reduce the size of the power system model. The characteristics of generators swing together are referred to as coherency Coherency groups whose generators state trajectory are similar to the other generators state trajectory in the same coherency group by a certain disturbance. In this paper, procedures for forming dynamic equivalents of control devices of coherency-based generating units are proposed and the aggregation of the control devices such as excitation system and governor-turbine system is accomplished by this method. This method can deal with the aggregation of the same type of control devices and combination of hydro and steam unit or the many types of excitation systems. etc. This method is shown to be efficient in reducing the number of control device of generating units with small error in the study group by result of case study presented latter part of this paper.
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In this paper, we analyze customers' working electric energy (kWh) which is served pole-transformer in order to reduce peak load current error which is generated in application load correlation equation. The characteristic of electric load which customers are using is classified by customer's working electric energy (kWh) and ratio of cooling equipment possession. For the input data of fuzzy model, we used to kWh on April which represents basic load and kWh which is increased from April to August. The April kWh is used to classify into large, medium, small customer. Also, the increased kWh is used to know information of cooling equipment possession. For the output value of fuzzy model, we can determined peak load current limit in application load correlation equation.
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This paper addresses the issues of the parameter error detection and identification in power system. The parameter error identification is carried out as part of the state estimation procedure. The weighted least absolute value(WLAV) estimation method is used for this procedure. The standard formulation of the state estimation problem is modified to include the effects of the parameter errors as well. A two step procedure for the detection and identification of faulted parameters is proposed. Supporting examples are given using IEEE 14 bus system.
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This paper presents an accurate algorithm for fault location of a single phase to earth fault on a two-parallel transmission line using only one-terminal data. It is impossible to calculate the accurate fault distance, because of the unknown fault resistance and fault current at the fault point. The faulted line circuit and the zero-sequence circuit of two-parallel line are used as a fault location model, which the source impedance of the remote end is not involved. The algorithm can eliminate the effect of load flow and the fault resistance in calculating the fault location.
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Power System Stabilizer is designed to improve dynamic stability and umdamped power angle oscillations through the application of supplementary stabilizing of excitation control. The object of this paper is to describe the design considerations of microprocessor based Power System Stabilizer especially in hardware design.
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In view of the importance of DFT(Discrete Fourier Transform) in spectrum analysis, its computation efficiency is a topic. This paper presents calculation time to extract the power frequency at a fault signal using DFT. Furthermore, it is tested a relaying algorithm based on modified DFT and its application to Micro-controller.
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This paper proposed the optimal operational scheduling of cogeneration system for paper mill connected with several auxiliary devices. Auxiliary devices that include auxiliary boilers, waste heat boilers and sludge incinerators operate with multi-cogeneration systems. Especially environment element was considered in objective function to solve the environment problem. And GAs(Genetic Algorithms) was applied to optimize and to analyse nonlinear operational property of cogeneration system of paper mill connected with several auxiliary devices. C-language was used to GAs computation. Electricity can be purchased through power system from utility. The proposed operational strategy on cogeneration system for paper mill to increase energy efficiency can be applied to the similar cogeneration system of industrial field.
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This paper describes the transient characteristics of air-gapped CTs in EHV transmission systems. An air-gapped CT is modelled using EMTP. Air-gapped CTs with the gap of 0, 0.5, 1.0 [mm] are analysed and compared with and without consideration of auto-reclosure. From the results. even small gap improves the transient characteristics after auto-reclosure.
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The B-coefficient method is well-known and universally used method for its simplicity and computation speed. However, the B-coefficient method has a weak point of accuracy when it is applied to the ill-conditioned systems where generators produce excessive reactive power. This paper describes the developed module to be applied to commercial program package of calculating the penalty factors by Jacobian method. The effectiveness of the proposed program has been demonstrated using the IEEE 30 bus system.
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This paper presents an approach to modeling the electrical railway accurately including the autotransformers and mutual impedance. The proposed approach can enhance the capability of analyzing the railway system, and can also be applied to a simulator for extensive stability study.
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This paper introduces the MMI software for Central Control System in the Distribution Automation System. It provides remote monitoring and real-time control of distribution through the use of remote terminal units(RTUs) graphically. Our MMI software for distribution automation displays a circuit operating map based on the distribution automation database, and overlays it with outage information from the feeder Automation software.
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Recently, several developments of real-time simulators have been reported. But they are very high cost. And then they are difficult to apply for relay testing in small business. This paper presents the structure and performance of a new pc based, low cost, tester to digital protection relays. Fault transients are generated either by simulating signals using EMTP or by recorded fault signals.
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대용량의 전원단지를 포함한 전력계통에서 기간 송전선로(Route) 고장발생시 해당 계통내 동기 탈조의 불안정 현상을 보이는 발전기들의 동기탈조를 방지하기 위한 사고파급방지장치(FPPC:Fault Propagation Preventive Controller)의 기본 구성, 알고리즘 현장시험 및 적용시 설치효과에 대해 검토하였다. 전원용량이 클수록 발전기 차단 제어 완료까지 요구되는 시간은 짧아지며, 제어 요구량 또한 증가한다. 따라서 제어완료까지의 시간을 최대한 짧게 하기 위한 시스템설계 및 오동작 발생을 방지하기 위한 Fail-safe 기능을 S/W와 H/W적으로 구성하였다.
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한전에서는 1996년 제주-해남간 HVDC 설치에 이어, 1999년 서대구 S/S에 SVC를 설치하였다. 이와 관련하여 본 논문에서는 한전계통에 최초로 설치한 서대구 S/S의 SVC설비운용과 관련하여 SVC의 이론 및 제어기법과 관련된 일반이론을 소개하고, 설치된 SVC의 기기구성방식 및 특성, 제어특성, 기기사양 등에 대해 간략하게 소개하고자 한다. 서대구 SVC는 345kV/13.5kV, 100MVA급으로서 TCR 및 TSC방식의 하이브리드 방식으로 되어 있다.
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Soil resistivity has a relation with the corrosion of underground buried structures as a water pipeline, gas pipeline and power cable casing. And it's a main factor in the cathodic protection and earth design. This paper presents soil resistivity maps each depth through measuring the soil resistivity in Kwachon, Kyonggi province. Also examines the soil resistivity characteristics on a change of temperature, moisture content and ion content in the laboratory.
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This paper describes the study of the effect on real power system due to the inclusion of the MTR at Buk Che-ju TP #2. The test system in which the transformers are represented in detail and rest Che-ju systems are represented as an equivalent system on the bus is simulated by the EMTDC. Simulation results include magnitude of inrush current and voltage drop on the bus at various CB closing time, and they show the effect on Che-ju system by the inrush current of the Buk Che-ju TP #2's MTR is not considerable.
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This paper presents the methodology of measuring the 22.9[kV] bus load characteristics for verifying the bus load model developed with equivalent load aggregation of load components, and the analysis of 22.9[kV] load data.
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In this research, selection of component load and measurement device is considered for accurate component load modeling. The procedure of component load characteristic experiments is also presented.
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Jeong, S.H.;Kim, D.K.;Choi, S.B.;Bae, J.H.;Ha, T.H.;Lee, H.G.;Cho, S.B.;Kang, J.W.;Yoon, H.H. 328
This paper was studied on a recent trends for the standard of calculating the cable current-carrying capacity. -
Power supply for Nuclear Power Plant was developed, and MMI monitoring circuit was added to the main function of power supply. The developed power supply is designed to show equal or higher performance compared with the existing power supplies. Performance of the power supply is verified by simulations, experiments, and authentication test for Q-class, he status of power supply and fault waveform can be displayed and analyzed on PC by RS-232C port. By adopting the latest parts, mainly domestic models, production cost and delivery can be reduced. Replacement period of capacitor can be extended by life estimation.
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Piping systems of the power generating stations have been generally protected by hydraulic and mechanical snubbers which can allow large displacements arising from temperature change while those can reduce or absorb stresses due to vibrations. However these snubbers require amounts of budget for maintenance or replacement because of the leakage, lubrication and finally short life cycle. Recently the snubbers consisted of wire rope have been proved to reduce vibrations of piping systems. While the wire rope snubbers are free of maintenance such as leakage and lubrication imported price are so high. Now it is necessary to design. manufacture and certificate these wire rope snubbers.
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본 논문은 초 중 고등학교 교과서에 수록되어 있는 전기 분야의 내용을 분석하고 전기관련 교과서의 교육 방안을 제시하고자 한 것이다. 교과서 분석을 통하여 현재에 초 중 고등학교 학생들이 어떤 내용으로 전기를 배우고 있는가를 고찰하고 전기 분야에 대한 청소년들의 인식을 높일 수는 방법을 제시 하고자 한다. 그리고 교과 개정 작업순서를 나타내어 효과적인 앞으로의 교육방안을 제시하고자 한다. 더 나아가 초 중 고등학교 교육 과정의 전기 관련 분야에 대하여 관심을 가지는 계기가 되고자 한다.
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본 연구에서는 VHDL로 설계한 제어기를 이용하여 3상 다이오드 정류기의 입력파형 개선을 수행하였다. 일반적인 부하측에 흐르는 전류는 매 순간 3상 중에서 가장 높은 상에서 가장 낮은 상으로 흐르게 되므로 나머지 한 상의 전류가 불연속적으로 흐르게 된다. 이때 다이오드로 도통되지 않는 상의 전류는 부가한 스위치를 통하여 흐르게 되어 전류의 연속성을 얻을 수 있다. 이러한 동작을 위해 제안된 제어기는 입력신호에 맞추어 적절한 PWM 신호를 스위치에 인가함으로서 정류기의 역률 개선 및 고조파 저감의 효과를 얻을 수 있었다. FPGA제어기는 기존의 DSP를 이용한 제어기에 비해 작은 소비전력을 사용하며 제작기간을 줄일 수 있고 소형화시킬 수 있는 장점을 가짐을 확인하였다.
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최근들어 전력 사용량이 증가하고 각종 악성 부하가 증가하면서 최대전력 사용량의 증가 와 고조파 및 상 불평형 전류등에 의한 기기 오동작이나 수명 저하가 문제시 되고 있다. 본 논문에서는 이러한 문제점을 해결하기 위해서 단일 기기로 유효전력 제어, 상 불평형 및 고조파 전류 보상 그리고 무효전력 억제의 기능을 수행할 수 있는 다기능 전력공급 장치를 개발하였다. 실험을 통하여 다기능 전력공급 장치의 성능을 확인하였다.
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This paper presents a new control algorithm for series active power filters that are applied to 3-phase 3-wire and 3-phase 4-wire systems with capacitive loads. It is difficult to reduce harmonic currents in neutral lines of the 3-phase 4-wire systems using conventional series active power filter control methods. 3-phase 4-wire series active power filter systems using the proposed method in this study lower neutral line harmonics. Simulation was carried out to verify the algorithm.
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A Switching control circuit based on a micro-controller is developed for blinking operation of fluorescent lamps, which would be suitable for use in the advertising panel. Ten modes of blinking patterns are implanted within the EEPROM. The developed circuit can handle up to 128 fluorescent lamps of 20-40W range, and the lamp life is expected to so beyond 3000 hours.
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Single-Phase multi-level AC-DC converter that is composed of diode bridge and switch is proposed. The number of the supply current level is depending on the individual current level of the converter. A converter circuit, the number of the level is equal to
$2^{M+1}-1$ , where M is the number of Switching Converter. The proposed circuit has converter with 31 current levels. When the number of current level is increased, smoother sinusoidal waveform can be obtained directly and it is possible to control the supply current almost continuously from zero to maximum without generating high voltage step changes as pulse with modulation technology. The technique illustrates its validity and effectiveness through the PSIM. -
This paper presents a new soft-switching partial series resonant DC/DC converter (PSRC) with zero-voltage on/off simultaneously, suitable for application in the high power and high frequency switching. The proposed converter has not only advantages of the conventional PSRC but also zero-voltage turn-on and turn-off of the main switches for the entire load ranges by adding the auxiliary circuit, and zero-voltage-switching (ZVS) turn-on of the auxiliary switches. The operation principles of the new converter are explained in detail and the several interesting simulation and experimental results verify the validity of the proposed circuit.
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This paper proposes an SSSC based on 3-level half-bridge inverters. The dynamic characteristic of the proposed SSSC was analyzed by EMTP simulation, assuming that the SSSC is inserted in the transmission line of the one-machine-infinite-bus power system. The proposed SSSC has six 3-level half-bridge inverters per phase, which operates in PWM mode. The proposed SSSC generates a quasi-sinusoidal output voltage by 90 degree phase shift to the line current. The proposed SSSC does not require the coupling transformer for voltage injection, and has a flexibility in operation voltage by increasing the number of series connection.
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This paper suggests switching regulator technique to overcome the drawback of conventional variable linear power supply. Switching regulator technique can eliminate the extremely lossy operation and reduce the size and weight of variable linear power supply and provide nearly constant output power over the majority of output voltage range. The topology of variable switched mode power supply is employed active clamp forward converter with a current doubler rectifier and by using control of variable-frequency together with control of fixed-frequency, output voltage can be controled. Equivalent circuits pertinent to each operational mode of converter are derived, and an experimental 20V, 50A converter was designed and built. The converter operates from an output voltage of zero to 25 V, under 100 kHz switching frequency.
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Park, Young-Min;Yun, Jae-Hak;Han, Gi-Jun;Choi, Se-Kyung;Jung, Myung-Kil;Lee, Se-Hyun;Lee, Kyo-Beum;Song, Joong-Ho 369
A torque ripple minimization technique is proposed for high power induction motors driven by 3-level inverters with switching frequency of inverter switching elements limited around 500Hz level. It is noted that conventional DTC algorithms with torque ripple minimization scheme are devised for applications with relatively high switching frequency above 2-3kHz. A new DTC algorithm, especially for low switching frequency inverter system, illustrates relatively reduced torque ripple characteristics all over the operating speed region. Simulation results show effectiveness of the proposed control algorithm, and associated experimental works will be presented in the final paper. -
AC 전동기는 전기각 주파수에 비례하는 간섭항을 가지고 있어 d-q축의 전류응답이 서로 간섭을 일으키게 된다. 이런 간섭현상은 특히 고속운전에서 크게 나타나며, 이로 인해서 토오크 응답이 영향을 받게 되어 고성능을 요하는 적용 범위에서는 문제가 될 수 있다. 이를 해결하기 위해서 지금까지 몇 가지 방법이 제안되어 왔다. 본 논문에서는 이러한 방법들에 대해서 비간섭 제어 성능을 비교하고 파라미터 변화에 따른 영향을 분석한다. 분석된 결과는 실험을 통해서 얻어진 결과와 일치함이 보여진다.
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It is necessary to obtain the high performance of the inverter system that control the output current of inverters. The dead time causes detrimental effects to the control performance of the inverter system. So we need to compensate the dead time effects. And the dead time minimization switching method can be considered as the best way to avoid the dead time effects fundamentally. In this paper, a new dead time minimization switching strategy is proposed. According to the proposed method, very short dead time is adopted in only once when the current polarity is changing. And the adopted dead time is equal to the applied dead time or shorter than it. As the proposed method can be done with the porlarity information of the reference current. it is easy to avoid some problems in comparison with the case that the real current is used to get the polarity changing time; level detection difficulty, noise problem and so on.
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Interleaved dual boost 컨버터는 전력분배 시스템에서 입력 전류 리플을 줄이고 스위칭 손실을 줄일 수 있고, 필터 없이 입력라인 고조파 성분을 줄일 수 있으며, 더불어 역률 개선의 효과를 이룰 수 있다. 본 논문에서는 Interleaved Dual Boost(IDB) 컨버터를 운전하는 경우에 있어서 상태 공간 평균화법을 사용하여 소 신호 해석을 수행하였다. 그 해석 결과로 얻진 제어 전달 함수를 바탕으로 IDB 컨버터에 적합한 수 개의 제어기를 설계하였다. 시뮬레이션을 행한 결과로 얻어진 여러 가지 제어기 타입의 각 특성을 분석하고 그 중 IDB 컨버터로 가장 적절한 제어기를 제안하였다.
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In this paper a remote monitoring and control system using SNMP(Simple Network Management Protocol) for UPS (Uninterruptible Power Supply) systems is proposed. The local remote system by RS-232 or RS-485 communication code or the wide remote system by modems is used for conventional remote monitoring & control system for UPSs. But recently because of communication cost and long distance the system is changed to remote control systems through internet and information communication network. And serial communication method by RS-232 or RS-485 is used between agent and UPSs. In this study. we designed and developed the system which is able to control UPSs and to monitor errors. statuses and actual values transmitted from UPS through internet.
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This paper presents auto-tuning to compensate the integrator windup of the current and the speed PID controller of DC motor, which suppress the overshoot of transient response without delay of rising time. The simulation results using Matlab show the validity of auto-tuning methods.
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Recently, the application of the linear machine for industrial field is remarkable increased, especially for the gantry machine. machine tool system and CNC. In these application fields. high precise position control performance is essentially required in both the steady and transient state. And linear machine is necessary for high-precision processing and manipulation when relatively high forces are involved. This paper presents the new unified PID position control algorithm which have rare sensitivity to disturbance, which the gain adjusting process is simple. Also this paper investigates the use of the New Unified PID control to design for high stiffness. Through the experimental results, it is shown that the proposed algorithm has high dynamic characteristic for the linear machine application field nevertheless of its simple structure.
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In this paper, the vector of induction motor using as sensorless is described. Controlling through the estimation of input by slip, the speed controller wit control loops of torque control constant speed operation by the feedback of slip is composed.
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This paper presents a method of improving the power factor and the waveform of A.C line currents and the out waveforms of AC to DC fully bridge converter systems which is achieved by connecting converters in series and parallel. The results of simulation show that the power factor and the source voltage and current waveforms are improved by the method of connecting converter in series, and the controlled input voltage and current waveform using a current limit controller.
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In PWM inverter fed traction motor drive systems, the switching frequency is restricted and thus the electromagnetic acoustic noise is generated. To reduce such an audible noise, we propose the modified RSF(Randomized Switching Frequency)-PWM method. In the proposed RSF-PWM method, both triangular wave and sawtooth wave are used in one period as carrier waves. Because the proposed method has inherently the same property as sinusoidal PWM method, there is no problem of linearity. To verify the validity of the modified RSF-PWM method, computer simulations are carried out.
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The model reference adaptive control(MRAC) algorithm is applied to the speed control of an inverter driven permanent magnet brushless do motor MRAC is compared to a standard PI controller. Applying this algorithm has also been proved by simulations that quick speed response without over-shoot could be obtained for the motor system with variable parameters. Simulation results show that the adaptive controller is superior to the PI controller.
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In order to reduce the overall size and cost, researchers attempted to integrate the functions of power factor correction(PFC) and isolated dc-dc conversion into single power stage. However, single-stage isolated PFC converters have higher voltage stress and heavier loss when compared with a normal dc-dc converters. In this paper, we propose to add active clamping circuit to keep the switch voltage stress low and to achieve soft switching of electronic devices.
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Usually, in many applications. high frequency resonant inverters are used and the ZVS(Zero Voltage Switching) or ZCS(Zero Current Switching) techniques are used to improve the efficiency of resonant inverters. In this paper, a new switching scheme is proposed to improve the efficiency of resonant inverters which is based on the plan to keep the unity output displacement factor under the variable resonant frequency. The detail algorithm of the proposed switching sheme and the simulation results are presented.
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The FSK demodulation module is the circuit which detects the data being transmitted from reader by FSK method. It doesn't use the PLL, and has lower power consumption and easier integration than conventional FSK detector using the PLL. So in a smart card, it is suitable to apply. In this study, the FSK demodulation module of the low power smart card is designed and analyzed.
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본 논문에서는 최근 선진국에서 활발히 연구되는 EMF 차폐 대책의 일환인 수동루프에 대한 이론적 분석 방법을 제시하고, 고속철도 금전선 주변에서의 자계 저감효과를 보이고자 한다. 그 결과 수동루프를 이용하여 자계 저감효과를 확실하게 나타낼 수 있었다.
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To improve traction effort performance and stability of Korean High-Speed Railway Train, a practical re-adhesion controller including a novel wheel slip protection control scheme is proposed. The presented method is verified by various train running simulations by induction motor vector control with PWM inverter.
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This paper describes a simulation model and a scaled hardware model to analyze the dynamic performance of Unified Power Flow Controller, which can flexibly adjust the active and reactive power flow through the ac transmission line. The design of control system was developed using vector control method. The results of simulation and scaled hardware test show that the developed control system works accurately. And both models are very effective to analyze the dynamic performance of the Unified Power Flow Controller.
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본 연구에서는 워크스테이션 상에서 최적조류계산의 효율적인 분산병렬처리 기법을 개발하였다. 본 연구의 결과를 실제로 2587개의 송전선을 포함하는 미국 ERCOT 계통에 대하여 사례 연구한 결과 성능이 뛰어남을 알 수 있었다. 본 연구는 최적 조류계산을 병렬 처리하는 일반적인 방식을 제시해 줄 수 있을 것이라 생각된다.
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Three Dimensional Dynamic Analysis of High-Tc Superconducting Revolving Field Type Synchronous MotorOne of the most important aspect in developing High-Tc Superconducting Synchronous Motor is producing high-Tc superconducting tapes that withstand the amount of currents that is needed to run the motor with stability. The purpose of this paper is to find the magnetic field distribution inside the motor in order to find out if the high-Tc superconducting tapes operate stably in actual motor operation. With this goal, magnetic field distribution in a detailed model of the actual motor was analyzed through F.E.M. By analyzing the field distribution acquired through the computer simulation, it has been observed whether the high-Tc superconducting tape maintains its superconductivity in actual motor operation. Also, the effects of the flux damper on the motor's operational characteristics and the magnetic field distribution have been analyzed. As a result, it has been proved that the high-Tc superconducting tapes can withstand 600 A turns which is required by the previous simulation aimed at developing this motor. It has also seen that the flux damper reduces armature reactance during the motor operation and change of load, helping the stable motor operation.
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In this work, to detect of hydrogen in DI water in the generator area of nuclear power plants was fabricated Pd/Pt gate MISFET sensor using Pd membrane.
$H_2$ permeation through Pd accounts for external mass transfer, surface adsorption and desorption, transitions to and from the bulk metal, and diffusion within the metal. The identification of pinholes in the generator area of plant is an important safety consideration, as hydrogen build-up gives rise to explosion. For this type of application the sensor needs to be isolated in DI water, accordingly, a Pd membrane was used to separate the DI water. The hydrogen in the DI water was then absorbed on the Pd thin film and diffused into the oil through the thin film. The Pd/Pt gate MISFET sensor, encapsulated by oil, will thereby detect permeated hydrogen. -
본 연구에서는 기존의 자성 웨지의 제조공정을 대체하여 제조 공정이 단순하고, 그의 정밀성이 우수한 tape casting-lamination법에 의한 자성 웨지의 제조 공정의 적용 가능성에 대한 연구를 수행하였다. 철 분말과 에폭시 slurry는 우수한 tape casting 특성을 보여주었으며, 이렇게 얻어진 green tape과 유리 섬유를 적층하여 자성 웨지를 얻었다. 이러한 과정을 거쳐서 얻어진 제품의 품질 특성을 평가한 결과, 기존의 제조 공정으로 얻어진 제품에 비하여 품질의 균일성이 우수하며, 제조 공정을 혁신적으로 단축하는 것이 가능한 것을 보여주고 있다.
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In order to evaluate the integrity of nuclear power plants, J-integral calculation is crucial. For this purpose, finite element method is popularly used to obtain J-integral. However, high cost time consuming preprocess should be performed to design the finite element model of a cracked structure. Also, the J-integral should be verified by alternative method since it may differ depending on the calculation method. The objective of this paper is to develop a three-dimensional elastic-plastic J-integral analysis system which is named as EPAS. The EPAS program consists of an automatic mesh generator for a through-wall crack and a surface crack, a solver based on ABAQUS program, and a J-integral calculation program which provides DI(Domain Integral) and EDI(Equivalent Domain Integral) based J-integral calculation. Using the EPAS program, an optimized finite element model for a cracked structure can be generated and corresponding J-integral can be obtained subsequently.
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용접열영향부는 최고 도달온도로부터의 거리에 따른 온도구배 변화와 급격한 열 사이 클 때문에 조직 및 물성치의 변화가 예상되는 영역이므로 인성저하등 취성이 잠재적으로 내포된 지역임을 쉽게 예상할 수 있다. 따라서 송전 철탑용 STKT 590 용접열영향부에서의 상변태 거동과 미세조직의 변화에 따른 기계적 특성을 파악하여 용접부의 안전성 확보를 위해 용접열영향부(HAZ)의 상변태거동과 미시파괴기구를 연구하고 개선안을 도출할 필요가 있다.
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액체 로켓용 충돌분사형 인젝터는 구조가 매우 간단하면서 고유량의 연료를 분사시킬 수 있기 때문에 여러 엔진에 응용된 바 있다. 본 연구에서는 이러한 인젝터의 특성을 산업용 보일러에 적용하기 위한 기초 실험 및 수치 계산을 수행하였다. 충돌분사 노즐로부터 형성되는 분무의 분포 특성을 실험적으로 측정하였고 이를 실제 조건에 모사하기 위해 수치 계산을 하여, 두 결과를 비교하여보았다. 이로부터 보일러의 효율과 공해물질 저감에 영향을 가져오는 액적의 미립화 특성을 향상시킬수 있는 연료 분사 조건을 제시하였다.