bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quick and precise position control of ultrasonic motor using hybrid control
Authors: Senjyu Tomonobu , Miyazato Hiroshi , Uezato Katsumi 
Published: July 2007

AbstractThe ultrasonic motor has an excellent level of performance and many useful features, including high torque, low speed, compactness in size, and absence of electromagnetic interference. This motor has an especially large holding torque and a high response characteristic, making it ideal for use as a servomotor. The drive principle of the ultrasonic motor is, however, different from that of electromagnetic motors and its mathematical model has not been developed yet. Its speed characteristics, moreover, vary with the driving conditions. Consequently, it is difficult to control the ultrasonic motor while maintaining performance. In this paper, a position control scheme using adaptive control is proposed. The utility and validity of the proposed control scheme is tested in experiment.
Frequency response function of magnetic bearings using high‐temperature superconductor
Authors: Higasa Hiromasa , Takahata Ryoichi , Imaizumi Hiroshi , Miya Kenzo 
Published: July 2007

AbstractA high‐temperature superconductor YBa2Cu3O7‐x with strong pinning force has allowed stable magnetic suspension with no control to be developed. Two types of superconducting magnetic bearings (SMB) using YBCO and permanent magnet were assembled. The two types are radial and axial. The dynamic stiffness of each SMB as it was cooled down under a magnetic field by liquid nitrogen was measured both radially and axially. As a result, it was found that the spring constants of these SMBs were almost as large as a practically desirable value; however, their damping coefficients were lower than the practical level. These findings are useful as one of the data bases for development of an optimum SMB design to support the weight of rotors in an axial direction.
Deterioration characteristics of insulating spacer model in repeating impulse voltage
Authors: Okabe Shigemitsu , Ono Takahiro , Zaima Eiichi , Aoyagi Hirokuni , Murase Hiroshi , Oshima Iwao 
Published: July 2007

AbstractTo discuss the UHV GIS test voltage, the deterioration characteristics of the GIS insulating spacer model were studied by repeating lightning or switching impulse voltage. The deterioration factor indicating the decrease of lightning or switching impulse breakdown voltage applied up to 1000 times was found to be 35.7/45.5. The relationship between the partial discharge inception voltage and the breakdown voltage after 1000 impulse applications was also studied. It was found that the partial discharge inception voltage increases despite a decrease in breakdown voltage due to the impulse voltage.In addition, to elucidate the deterioration phenomenon, a study was made of the breakdown characteristics of models with various boundary conditions between the electrode and epoxy resin, as well as the relationship between the boundary conditions.Microdischarge was also studied. The results of the investigation suggest that the deterioration by repeating voltage is caused by microdischarge due to electric field intensification on microprotrusions of the electrode surface.
Visualization of results of load flow calculation and dynamic simulation
Authors: Kobayashi Naoki , Yamada Takeshi , Okamoto Hiroshi , Tada Yasuyuki , Kurita Atsushi , Sekine Yasuji 
Published: July 2007

AbstractThis paper proposes graphical representation methods of static and dynamic characteristics of power systems. The methods use the computed results of load flow calculation and dynamic stability calculation. This work develops three kinds of representation methods using maps and animation which are sequential graphical representation of maps based on dynamic stability calculation.Conventionally the results of load flow calculation and dynamic stability calculation are represented and comprehended using load flow maps or dynamic swing curve. However, quick and effective comprehension of power system characteristics by such conventional representation methods is becoming more difficult as power systems to be analyzed are becoming larger and more complicated, especially in power systems with many loops or grids. Graphical representation using the proposed methods makes it easy to understand the static and dynamic characteristics of power systems quickly and comprehensively.In addition to these methods, this paper proposes a heuristic logic that makes it possible to draw maps automatically. It is very convenient to apply these methods to arbitrary power systems even if their constitutions or characteristics are not well known.
Speed control system and design of resonant system with disturbance observer
Authors: Morimoto Shigeo , Kameyama Hiroyuki , Takeda Yoji 
Published: July 2007

AbstractIn industrial motor drive systems such as industrial plants and industrial robots, a torsional vibration often is generated because of the elastic elements in torque transmission. This vibration makes it difficult to achieve quick responses of speed and may result in damage to the plant. Such systems simply are modeled as a two mass system. The shaft torque feedback system with the disturbance observer, which is called “resonance ratio control,” is proposed to suppress the vibration for the two‐mass system.In this paper, the design of controller gains in the shaft torque feedback system is examined considering not only the control performance such as the vibration suppression and dynamic responses, but also the robust stability against the noise and the model uncertainties. This paper shows the validity of the control system and the examinations by several experiments.
Performance improvement of active filter for power distribution line using current source PWM inverter
Authors: Matsunami Shinya , Yamamura Naoki , Tsunehiro Yuzuru 
Published: July 2007

AbstractAn active filter (AF) is a device to eliminate switches. There are two types of AF, the voltage source type and the current source type. The voltage source type is common in practical use today. But we have studied and already reported that the AF of the current‐source type has the characteristics of rapid and precise controllability of the output current and little interference between the AF and the distribution line.In this paper, we propose two schemes to improve its performance and to reduce its capacitance.To improve the performance of AF, we changed the PWM carrier from the triangular wave used in a previous paper to the sawtooth wave. However, the switching rates remain the same. By using the 5 [kHz] sawtooth carrier (corresponding to 2.5 [kHz] triangular wave) and the multiplexed connection of AF, harmonic currents of less than 19‐th order can be eliminated in the distribution line.To reduce the capacitance of the AF, we proposed an AF which eliminates only harmonic currents. By using other apparatus for fundamental reactive power compensation, a more economical system can be achieved.The experimental results on the tested apparatus show that these methods are useful for realization of a current‐source type AF.
Fundamentals of a new absolute magnetic scale using nonrepeated codes
Authors: Mikoshiba Takashi , Yamasawa Kiyohito 
Published: July 2007

AbstractFor the linear displacement measurement in industrial machines, a linear scale using a magnetic phenomenon is superior to environment‐resistance. An absolute‐type magnetic scale has the feature of providing safety of a position information with high reliability. Until now, an absolute‐type magnetic scale writes a position information at plural parallel tracks. The scale becomes large‐sized for a long measuring length. Furthermore, a fine magnetic pattern of the scale is needed for a high resolution. From the practical viewpoint, however, the fine pattern makes the clearance of detecting head and scale small. For the solution of these problems, a new magnetic scale is proposed where an absolute position information is written at series on one track accompanying a parallel incremental track. The scale is expected to be small‐sized and to show a high efficiency having a long measurement range without decreasing accuracy and resolution. from the above, the new absolute‐type magnetic scale with absolute track is made where the position‐information is written in at series by using nonrepeated codes and with a parallel incremental track.Furthermore, the operation and structure, performance characteristic are clarified. The operation characteristics of the scale are measured, and the response speed and the position accuracy are discussed.
A decentralized control system for stabilizing multimachine power systems
Authors: Ohtsuka Kei , Nishida Makoto , Morioka Yasuo , Yachida Kenji 
Published: July 2007

AbstractA decentralized control system is studied for stabilizing multimachine power systems. A longitudinal power system with three areas, each having one machine, is considered in this study. A decentralized control design method is proposed, which is based on the optimal regulator theory. First a centralized control system is designed without any consideration on whether state variables are all available or not. Second a pseudo‐decentralized control system is designed by omitting control gains corresponding to state variables which give hardly any effects on the power system stability. It is found that only one variable of phase angle of each machine is absolutely necessary for the pseudo‐decentralized control system. This leads to an idea based on power system engineering, that is to say, new variables of tieline power flow are introduced in the decentralized control system design to substitute for the phase angle of each machine. Thus a decentralized control system for power system stability can be designed using the new variables of tieline power flow. It is demonstrated from simulation studies that the decentralized control system improves even longitudinal power system stability as well as the centralized control system.
Development and practical application of fully split core for power transformers
Authors: Isaka Susumu , Yagisawa Takeshi , Tokumasu Tadashi , Kase Toshio , Menju Shin‐Ichi 
Published: July 2007

AbstractIn a three‐phase, three‐leg core of a core‐type power transformer, the yokes are magnetically connected to all three phases so as to ease the flow of the magnetic flux (generally by means of lap joints of yokes and legs), and at the same time to smooth the magnetic flux between phase legs through yokes. It has generally been assumed that a split core with full separation at the center of the leg including yokes is unsuitable for use in power transformers owing to core losses, local heating, and noise resulting from the imbalance and distortion of magnetic flux, even though it can be used in distribution transformers with wound cores. But since the split core has many advantages from the manufacturing viewpoint, the magnetic characteristics of small core models were studied in detail. Studies with a full‐scale 1500/3 MVA model transformer core indicate that the degradation of magnetic characteristics compares favorably with conventional cores.
Insulation characteristics of perfluorocarbon liquid/solid insulation for nonflammable large power transformer
Authors: Miyagi Katsunori , Horii Shigenobu , Sugimoto Toshiro 
Published: July 2007

AbstractA new type nonflammable large power transformer system is proposed in which the excellent cooling characteristics and insulation properties of nonflammable perfluorocarbon (PFC) liquid is utilized. In the system, transformer windings are put in an insulating cylinder filled with PFC liquid. The core includes cooling panel through the liquid. The space between the insulating cylinder and tank is filled with compressed SF6 gas.This paper describes the insulation characteristics of main insulation and inter‐winding insulation models which simulate the transformer. It is found that (1) higher withstand voltage is expected by means of insulation barriers in the main insulation model; (2) partial discharge in inter‐winding insulation model is beginning to behave in a constant electric field strength on the point of 0.1 mm liquid gap length.
Robust control with pole assignment in a specified region for systems under parameter perturbations; application to a nonlinear system
Authors: Obayashi Masanao , Hirasawa Kotaro , Murata Jun'Ichi , Kajiwara Akio , Sagara Setsuo 
Published: July 2007

AbstractThis paper deals with the problem of determination of feedback gains in order to achieve required performances under linear time invariant perturbations. Based upon the Lagrange multiplier method, the proposed method determines feedback gains that ensure both robust stability and robust performance for a linear uncertain system. It is applied to a nonlinear crane system control design. The nonlinear system is first partitioned into some uncertain linear systems. Then the proposed method is applied to each uncertain linear system. Application is easily demonstrated and, consequently, a nonlinear crane control system can be easily designed. Finally, it is shown in a numerical example that the proposed method is effective.
Use of the homotopy method for excitation control of generators for multimachine power system
Authors: Matusita Kunio , Omatu Sigeru 
Published: July 2007

AbstractIt is important to consider the stabilization problem for a large‐scale power system. This paper uses a dynamic compensator based on observer theory such that desired poles are placed for a closed‐loop multimachine power system. Since the system dimension is large, it is difficult to apply a conventional dynamic compensator method to an excitation control problem for a multimachine power system.The homotopy method is introduced to solve fundamental nonlinear equations which are required for observer synthesis. To show the effectiveness of the proposed method an excitation control of generators for a multimachine power system is considered. From the simulation result, it is shown that the present method is useful in stabilizing a multimachine power system.
Decentralized system identification for electric power system
Authors: Kawamoto Shunji , Kanetaka Iwao 
Published: July 2007

AbstractResearch on decentralized control of an electric power system is important for stabilizing control problems. In particular, since an electric power system is a large‐scale nonlinear control system, decentralized (not divided) systems with cooperation should be constructed.This paper presents ways to construct decentralized systems for an electric power system. In section 2, swing data of a three‐machine model system are obtained, in section 3, coefficient parameters of the model equation based on one‐machine infinite‐bus system with AVR and GOV are estimated by the least square method. In section 4, the equivalence calculated using estimated values is discussed, and the effect of conditions on fault is considered. Finally, section 5 is devoted to summarizing results of decentralized system identification.
Power system restoration by joint usage of expert system and mathematical programming approach
Authors: Nagata Takeshi , Sakaki Hiroshi , Kitagawa Minoru 
Published: July 2007

AbstractWhen electric power supply interruption is caused by a fault, it is imperative to restore the power system promptly to an optimal target configuration after the fault. The problem of obtaining a target system is referred to as power system restoration. Both mathematical programming (MP) and expert systems (ES) have been used to solve restoration problems. However, existing approaches based on either MP and ES alone have inherent limitations stemming from their own paradigms. Mathematical progressing can obtain an optimal configuration under specified operational constraints, but requires a relatively long solution time. Although ES are effective in that they can utilize expert knowledge, maintenance of large‐scale ES requires inordinate effort.This paper proposes a new approach to power system restoration that utilizes both methodologies so as to exploit both systems' advantages. That is, a system under study is decomposed into a set of subsystems based on the knowledge of restoration experts, which is realized as an expert system. Then, MP is applied to each decomposed subsystem to obtain an optimal target configuration. A feasible operation sequence leading to the target configuration is generated by ES. This approach reduces significantly the computation time required to obtain target systems and is far less than would be the case if the total system is solved (as a unity). Moreover, the number of rules in the knowledge‐base are greatly decreased.
Temporary overvoltage capability of surge arresters for 1000 kV power systems
Authors: Nakada Yasuhiko , Yamada Seiichi , Oishi Kazuya , Shirakawa Shingo 
Published: July 2007

AbstractInsulation level (LIWV 2250 kV) of 1000 kV gas insulated switchgear will be adopted by installing high performance 1000 kV surge arresters. But when temporary overvoltage (TOV) is generated in power systems at line faults and load rejection including Ferranti effects, high performance surge arresters flow discharge current according to the value of TOV. Therefore, it is important to check TOV discharge capability of surge arresters. This paper describes the screening of zinc oxide elements using thermography (thermal uniformity factor) obtained by an infrared radiation camera, with discharge capability of surge arresters for 1000 kV power system.
Application of genetic algorithm to speed servo system and positioning system
Authors: Yoshida Susumu , Kamano Takuya , Suzuki Takayuki , Harada Hironobu 
Published: July 2007

AbstractThis paper considers a genetic algorithm application to feedforward controllers of speed servo and positioning systems. The system consists of a conventional feedback controller and a feedforward controller. The parameters of the feedforward controller are regarded as the chromosome on a gene. The genetic algorithm is used to tune the parameters of the feedforward controller, the objective of which is to make the feedforward controller a dynamic inverse of the plant. The tracking error between the desired output and the actual output at every sampling period is used to calculate the fitness of one gene. The range of mutation is dependent on the magnitude of the tracking error, which ensures parameter convergence. The effect of fitness function and the width of mutation on tracking performances is investigated. The experimental results demonstrate the effectiveness of the proposed genetic algorithm in improving tracking performances.
Improvement of power system stability by on‐off discrete control of series capacitors
Authors: Hara Tsukushi , Kobayashi Naoki , Takei Akihisa , Tanomura Ken'Ichi , Koyanagi Kaoru , Komukai Toshihiko 
Published: July 2007

AbstractApplication of controlled series capacitors with anti‐parallel thyristor combination across the capacitor segment is one of the new and promising countermeasures for enhancement of power system stability. The line reactance can be directly controlled by the controlled series capacitors, hence, it is very effective to apply the capacitors for damping power system disturbances.In this paper, we describe the following.(1) The design method of control system for the segmented series capacitors with thyristor switches is proposed.(2) The effectiveness of the controlled capacitors proposed for power system stabilization is shown with the results of EMTP analysis.(3) The possibility of zero passing missing phenomena of capacitor voltage is indicated by EMTP simulation, and a countermeasure is proposed in order to avoid the phenomena. The effects of the countermeasure is indicated by the results of EMTP simulation.
Development of restoration system based on human performance model
Authors: Shinohara Jun'Ichi , Nagata Jun'Ichi , Saitoh Hideki , Kozakai Isao , Ohuchi Azuma , Kurihara Masahito 
Published: July 2007

AbstractA stable power supply is required from power systems as the importance of electrical energy increases. Particularly, in the case of high‐voltage systems (500‐, 275‐, 154‐kV bulk power systems), this requirement is high. However, there are cases when power system faults cannot be avoided. Accordingly, it is very important to restore power systems quickly and safely if these failures occur. The characteristics of the power system restoration (its combinatorial aspects, use of knowledge from a wide variety of origins and of different types, number of criteria to satisfy) make it a difficult problem, for which the use of expert systems to generate restoration plans is being considered by many researchers, and promising results have already been obtained. However, most systems are still in the prototype stage [1]. One reason seems to be the lack of studies of a support system for knowledge‐based behavior (unable to describe with any rule).This paper analyzes first power system restoration based on the human performance model [6] and discusses the knowledge‐based behavior that is a high conceptual level of human performance to solve the problem from the combinatorial viewpoint. Then the application for the trunk line dispatching center is reported. Finally, the relations between knowledge‐based behavior and the designed human interfaces are verified with a power networks restoration case‐study.
Sensor diagnosis system combining immune network and learning vector quantization
Authors: Kayama Masahiro , Sugita Yoichi , Morooka Yasuo 
Published: July 2007

AbstractA distributed diagnosis system combining Immune Network (IN) and Learning Vector Quantization (LVQ) for detecting fault sensors accurately in industrial plants is proposed. It has two execution modes, namely, its training mode where LVQ extracts correlation between each two sensors from their outputs when they work properly, and its diagnosis mode, where LVQ contributes to testing each two sensors using the extracted correlation, while IN contributes to determining fault sensors by integrating these local testing results obtained from LVQ. Discussed here is how to improve diagnosis capability of the developed system. It is shown that the thresholds can be determined effectively by the constraint that the hyperregion corresponding to the normal sensor outputs in each quantization vector space is a single region.Diagnosis capability of the developed system is evaluated using a prototype system for detecting fault sensors of a reheating furnace plant. With the proposed method, abnormal sensors, such as aged deteriorated ones, which have been difficult to be detected only by checking each output of sensor independently, are possible to be specified.
Experimental study on harmonics reduction effects of damper windings in a synchronous generator
Authors: Katagi Takeshi , Matsuki Jun'Ya , Okada Takao 
Published: July 2007

AbstractWith the recent development of power electronics technology, thyristor‐controlled equipment has largely been introduced to the electric power system. These devices generate harmonics that cause voltage distortion and undesirable effects on the power system components. On the other hand, the damper windings of synchronous generators basically are designed to reduce harmonics as well as to damp out system oscillations. However, up to now, the effects of damper windings on harmonics have not been clarified fully in a quantitative way.In this paper, the results of experimental study on the harmonics reduction effect of damper windings have been presented. A specially designed 6‐kVA generator was connected to an infinite‐bus system to investigate the characteristics of damper windings. A new method to measure induced voltages between damper bars, damper bar currents and air‐gap flux densities in the tested generator was established. By comparing these measurements with and without the presence of damper windings, the effect of damper windings was quantified. Thus the reduction effects of the damper windings on slot ripples and harmonics caused by armature current mmf were investigated and were made clearer than before by the proposed method.