bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of primary‐on‐slider ultrasonic piezoelectric actuators and experiments on multidegree of motion freedom plane actuator
Authors: Hoshi Nobukazu , Kawamura Atsuo
Published: July 2007

Recently, various machines and tools have been miniaturized, and with this trend, the size of an actuator becomes a very important factor. An ultrasonic actuator is different from other actuators using electromagnet force in the driving principle. The structures of an ultrasonic piezoelectric actuator is simple. An ultrasonic actuator converts the ultrasonic mechanical energy to mechanical thrust force by a friction force. Based on this idea, various ultrasonic actuators have been proposed and experimentally constructed.

In this paper, the basic characteristics of a piezoelectric actuator are analyzed theoretically. The relationship between the thrust force and the weight force is clarified and verified by experiments. Various prototypes of plane ultrasonic piezoelectric actuators are constructed experimentally, and the fundamental characteristics are measured.
Inertia moment identification in the average speed‐type instantaneous speed observer
Authors: Okamura Yusaku , Chun Yeonghan , Hori Yoichi
Published: July 2007

In recent servomotor control systems using highspeed microprocessors, it is difficult to obtain accurate speed information by using a low‐resolution shaft encoder because encoder pulses are very sparse in the low‐speed range. To overcome this problem, the instantaneous speed observer is proposed, system stability is improved, and strong disturbance rejection control is realized. However, when the inertia moment changes, the estimated instantaneous speed has error because the observer uses the nominal value of the inertia moment to calculate the instantaneous speed. For this reason, the identification method of the inertia moment for the “position input‐type” speed observer is proposed but it operated at about 50 rpm speed command. This paper proposes some novel identification methods for the “average speed‐input type” instantaneous speed observer and identifies the inertia moment in the very low speed range below 1 rpm.
Research on synchronous type and induction type levitated rotating motor
Authors: Ohishi Tetsuo , Shimura Seiji , Okada Yohji
Published: July 2007

A general solution of levitation control applicable to PM synchronous and induction type rotating motor is presented. It is intended for a single rotor to have both magnetic bearing and rotating motor. The rotational control is achieved with the traditional P pole magnetic flux, while the radial force is controlled with either P + 2 or P ‐ 2 pole magnetic flux in the stator. In the previous work, the proposed general theory of levitated motor is successfully confirmed with no load experiments.

In this paper, the load capability of the levitated motor is tested using a horizontal‐type experimental setup. The stator has eight concentrated wound electromagnets, each of which is controlled individually by a DSP and power amplifier. The radial load is the gravity of the rotor, while the produced rotating torque is measured with a variable torque load system. The results obtained are discussed in detail.
Stabilization of inter‐area and/or oscillatory modes in large‐scale power system by voltage impedance power system (VIPS) apparatus based on decentralized control scheme
Authors: Nagata Masaki , Yokoyama Akihiko , Sekine Yasuji
Published: July 2007

New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high‐speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors.

This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter‐area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large‐scale power system based on a Lyapunov function.

Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large‐scale power system.
An analysis of generation mechanisms of transitional peak current in sense‐emitter current for IGBTs with current sense and techniques to remove it
Authors: Hagino Hiroyasu , Yamada Tomihisa , Uenishi Akio , Tomomatsu Yoshifumi
Published: July 2007

It is important to remove the transitional peak current in sense‐emitter current which is due to dynamic current‐sharing during turn‐on for a design of IGBTs with current‐sense used protection against overcurrent and short circuit. But this analysis has been scarcely investigated.

This paper clarifies generation mechanisms of the transitional peak current by simulations and experiments using a parallel operation model and reports on techniques to remove it.

The following results were obtained.

(1) In the two paralleling devices model which consists of a sense cell and main cells, the transitional peak current occurs during turn‐on when a sense cell turns on faster than main cells. In this case, the main parameters that effect dynamic currents imbalance are gate resistance (Rg) and gate threshold voltage (Vth).

(2) In dynamic currents imbalance based on individual Rg and Vth among main cells, it may be treated as a two‐paralleling devices model which consists of a sense cell with Rgs and Vths, and main cells with average values Rgm and Vthm.

(3) The transitional peak current can be removed by the design of Rgs and Vths in a sense cell are larger than average values of Rgm and Vthm in main cells.

(4) On trial IGBTs with current sense Vths in a sense cell is different from the average‐value Vthm in main cells to change impurity concentrations of each channel. It was confirmed that the transitional peak current in sense‐emitter current can be removed by the design that Vths in a sense cell is larger than average value Vthm in main cells.
Substation simulation system using virtual reality technology
Authors: Mizukami Yuichi , Morita Shigeru , Asano Kunihiro , Kamiji Noboru
Published: July 2007

An indoor distribution substation simulation system based on virtual reality technology has been developed. The system is designed to give the user the feeling of actually touring a substation for routine inspection. Various states of the substation facilities, such as the opening and closing of the doors and the disconnectors as well as the relocation and extension of the installations, can be simulated. In the event the user approaches the energized components of the equipment and fails to keep the specified insulation distance from them, the system first sounds an alarm, and then a flashing red light on the display warns of passage beyond the safety point and that the operation has suffered an electric shock. Validation of equipment operating procedures, training of unskilled workers and work‐schedule preparation can be upgraded by using this system.
The principle and fundamental characteristics of brushless three‐phase synchronous induction motor with two stators
Authors: Inoue Kenji , Ohnogo Yukio , Yamashita Hideo
Published: July 2007

Brushless three‐phase synchronous motor involving a rotating ac exciter on the same shaft as the motor and with the windings linked through a shaft‐mounted rectifier is widely used as medium and large capacity machines. However, the motor needs to fit with damping windings for self‐starting outside of the field winding in the rotor and needs to equip discharge resistance with complex electronic device to dispose of electromagnetic force induced in the field winding at starting. Therefore, the rotor structure is very complex, and there are disadvantages, especially for the robust and highly reliable motor that is desired.

To solve the problem found in traditional motors, the authors proposed a brushless three‐phase synchronous induction motor with two stators and one wound rotor. This problem is solved because the proposed motor is of two‐stators structure: the rotor winding operates as a secondary winding of induction motor at starting and as the field winding at synchronous operation.

The motor can self‐start as a wound‐rotor induction motor without external secondary resistance. Therefore, discharge resistance is not necessary; the starting equipment is very simple and the rotor structure is robust. It is possible to start with high torque.

In this paper, the basic constitution of the proposed motor and the principles of operation are described in detail. The experimental results at starting and pulling into synchronism are shown for confirming the principles of operation and the experimental and numerical results of the starting characteristics. The load ones and the generating ones are shown and then the practical use of the proposed motor is confirmed.
A new method for discrimination of ground faults causes in distribution lines
Authors: Watanabe Makoto , Kotanishi Kazuji , Nakamura Osamu , Kurioka Hideaki , Hukui Sukenori , Tuji Katunori
Published: July 2007

Since most problems in distribution lines are ground faults, the technology to distinguish the causes in the distribution lines will be very useful in preventing faults beforehand or, at least finding any problems at an early stage.

The waveforms of ground faults which were collected from data concerning problems in the distribution lines and ground fault experiment are analyzed. The technology which could predict classified groups drawn from the scale of I0 (the waveform of ground fault current) and V0 (the waveform of ground fault voltage), and both of them in the ground faults is studied.

The results demonstrated that I0 could be classified into three groups, that is, leaking ground faults are sine curve shaped, gap discharge ground faults are triangular, and intermittent discharge ground faults are needle shaped.

Also, simulated equivalent impedance of the causes of ground faults by EMTP is calculated. Furthermore, the influence caused by the condition of the distribution lines is investigated. With these results, a technique is proposed which could predict the cause of problems in ground faults.
Optimization of failure diagnosis procedure based on diagnosis error loss
Authors: Kohda Takehisa , Inoue Koichi
Published: July 2007

Based on the results of its inspection items, the failure diagnosis system identifies the cause of system failure. The role of failure diagnosis is to identify the system state correctly. However, diagnosis errors may be caused by sensor failure or operator errors, which lead to serious damage or unnecessary protective actions. The effect of an error depends on the system condition. In the design of a failure diagnosis procedure, not only diagnosis error probabilities, but also the effect of diagnosis error on the system must be considered.

This paper proposes the optimization of failure diagnosis procedures based on diagnosis error loss. The optimal procedure that minimizes the expected loss caused by inspection errors is developed for two cases: one where all results of inspection items are given simultaneously, and one where an inspection item is examined sequentially. In the former case the optimal failure diagnosis logic is obtained, while in the latter case the optimal test sequence is developed. Illustrative examples show the merits and details of the proposed method.
The development of bi‐based high‐temperature superconductor and coil
Authors: Ogiwara Hiroyasu , Horigami Osamu , Yamada Yutaka , Satou Masako , Kitamura Tasuku , Hasegawa Takayo
Published: July 2007

Ag‐sheathed Bi‐2223 superconducting oxide conductors with a critical current density of 66,000 A/cm2 at 77 K and coils that have generated magnetic fields of approximately 1.5 Tesla at 4.2 K have been successfully developed. The conductors consist of piled‐up bundles of four to six sheets of element tapes with transport currents of approximately 200 Amps. The core size limit (CSL) prevented the production of single conductors that had the capacity to transport a current as high as 200 Amps at 4.2 K. Until now, it was difficult to develop a conductor having both high critical current density and the capability of transporting a large amount of current simultaneously. The role of CSL in large scale applications of high temperature superconducting oxides is discussed.
Quick and precise position control of ultrasonic motor using hybrid control
Authors: Senjyu Tomonobu , Miyazato Hiroshi , Uezato Katsumi
Published: July 2007

The 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

A 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

To 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

This 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

In 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

An 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

For 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

A 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

In 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

A 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

This 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

It 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

Research 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

When 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

Insulation 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

This 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

Application 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

A 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

A 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

With 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.
Development of partial discharge measurement method for pre‐mold cable accessories with separated‐shielding layers
Authors: Nakatani Youichi , Adachi Mikio , Miyazaki Toshihiro , Noma Takashi
Published: July 2007

Most of the accidents on XLPE cable line are caused by defective construction of cable accessories. Thus the authors developed a method to measure partial discharges in pre‐mold cable accessories. The authors provided separated‐shielding layers as detection electrodes in accessories, and discriminate between partial discharge pulse and noise pulse using realtime comparison of pulse current magnitudes from both detection electrodes.

This paper describes the principle of the noise discrimination method, portable partial discharge measurement apparatus, and the results of field test.
Compensation for light intensity variation by superposing AC magnetic field in optical measurement of DC current
Authors: Higaki Masaru
Published: July 2007

Optical voltage and current measurement generally necessitates the compensation of light intensity variation which occurs in the optical measuring system, because it is possible the light intensity variation may give rise to a measuring error. Therefore, such compensation methods as dividing the ac component by the dc component of the light intensity are usefully introduced in optical ac voltage and current measurement, but those methods are not useful exactly for the optical measurement of the quantities including dc components.

This paper deals with a new useful compensation method for light intensity variation in the optical dc current measurement. Linearly polarized light passes through two kinds of Faraday sensors, in which one detects dc magnetic field caused by dc current and the other detects externally applied constant ac magnetic field. Then, the compensation of the light intensity variation is carried out by measuring the dc and ac components of the beam. The principle of the compensation method using the ac component is described in the paper. Experimental results of this method using flint glass as the Faraday effect cells are reported and it is clarified that this method can decrease the measuring error of the modulation depth for dc current and compensate light intensity variation validity.
Ultrasonic motor‐actuated direct drive positioning servo control system using fuzzy‐reasoning controller
Authors: Izuno Yuji , Nakaoka Mutsuo
Published: July 2007

This paper describes a traveling‐wave ultrasonic motor (USM)‐actuated positioning servo driver, suitable for direct‐drive motion systems, which incorporates a fuzzy‐reasoning software controller with speed and position‐variable feedback schemes. The experimental results of this USM position servo driver operating at two‐phase high‐frequency resonant inverter are illustrated and evaluated using a one‐axis servo motion drive system. The results show that the new system using a compact USM that incorporates a microprocessor‐based two‐input and one‐output fuzzy‐reasoning controller is cost effective and suitable for special purposes in the industrial, medical, automotive, space and consumer fields.
A study of the electromagnetic vibration of a capacitor induction motor caused by time‐harmonic voltages
Authors: Hirotsuka Isao , Tsuboi Kazuo , Itoh Yuuichi , Ueda Fukashi , Matsui Keiju
Published: July 2007

In recent years, power source voltage waveform distortion has become noticeable, as electrical appliances with rectifier circuits have become widely used. Connecting capacitor inductor motor (CRM) to such distorted supply, or controlling CRM by simple controller with a switching device (such as triacs), harmonic voltage is supplied to CRM. In that case, CRM produces electromagnetic vibrations caused by not only the fundamental voltage but also time‐harmonic voltages in the distorted voltage. In addition, CRM produces electromagnetic vibration due to backward magnetic fields. Thus, it is difficult to clarify a relationship between electromagnetic vibration of CRM and harmonic voltages.

In this paper, the causes of the electromagnetic vibration of CRM operating under distorted wave supply voltage are discussed. First, a general equation of dominant electromagnetic force waves is shown considering not only forward magnetic fields but also backward magnetic fields. Using a general equation, causes of dominant electromagnetic vibration can be clarified. Next, by discussing in detail some examples of the dominant vibration, the relationship between the vibration and harmonic voltages becomes evident. Furthermore, the relationship between the vibration and backward magnetic field is clarified.
Soft‐switching PWM DC‐DC converter with reduced circulating current
Authors: Hamada Satoshi , Nakaoka Mutsuo
Published: July 2007

Soft‐switching phase‐shifted PWM converters have attracted much attention because of their low switching losses, constant frequency operation and simple control. However, a circulating current flows through the transformer and the primary bridge circuit during the free‐wheeling interval, resulting in relatively high current stresses on the transformers and switching devices compared with those of conventional hard‐switching PWM converters.

This paper presents an improved soft‐switching phase‐shifted PWM DC‐DC converter that can substantially reduce the circulating current by employing a tapped inductor for the output low‐pass filter. The principle of operation and the role of the tapped inductor are illustrated. The effectiveness of the tapped inductor is evaluated through simulation analysis. Moreover, a 500 W‐100 Hz prototype converter is implemented to demonstrate the excellent performances of both low switching and low conduction losses.
Two‐electron integral evaluation on the graphics processor unit
Authors: Yasuda Koji
Published: July 2007

We propose the algorithm to evaluate the Coulomb potential in the ab initio density functional calculation on the graphics processor unit (GPU). The numerical accuracy required for the algorithm is investigated in detail. It is shown that GPU, which supports only the single‐precision floating number natively, can take part in the major computational tasks. Because of the limited size of the working memory, the Gauss‐Rys quadrature to evaluate the electron repulsion integrals (ERIs) is investigated in detail. The error analysis of the quadrature is performed. New interpolation formula of the roots and weights is presented, which is suitable for the processor of the single‐instruction multiple‐data type. It is proposed to calculate only small ERIs on GPU. ERIs can be classified efficiently with the upper‐bound formula. The algorithm is implemented on NVIDIA GeForce 8800 GTX and the Gaussian 03 program suite. It is applied to the test molecules Taxol and Valinomycin. The total energies calculated are essentially the same as the reference ones. The preliminary results show the considerable speedup over the commodity microprocessor. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
Insights into the mechanisms of flavoprotein oxidases from kinetic isotope effects
Authors: Fitzpatrick Paul F.
Published: July 2007

Deuterium, solvent, and 15N kinetic isotope effects have been used to probe the mechanisms by which flavoproteins oxidize carbon–oxygen and carbon–nitrogen bonds in amines, hydroxy acids, and alcohols. For the amine oxidases D‐amino acid oxidase, N‐methyltryptophan oxidase, and tryptophan monooxygenase, D‐serine, sarcosine, and alanine are slow substrates for which CH bond cleavage is fully rate limiting. Inverse isotope effects for each of 0.992–0.996 are consistent with a common mechanism involving hydride transfer from the uncharged amine. Computational analyses of possible mechanisms support this conclusion. Deuterium and solvent isotope effects with wild‐type and mutant variants of the lactate dehydrogenase flavocytochrome b2 show that OH and CH bond cleavage are not concerted, but become so in the Y254F enzyme. This is consistent with a highly asynchronous reaction in which OH bond cleavage precedes hydride transfer. The results of Hammett analyses and solvent and deuterium isotope effects support a similar mechanism for alcohol oxidase. Copyright © 2007 John Wiley & Sons, Ltd.
Utility of ionic liquids in analytical separations
Authors: Shamsi Shahab A. , Danielson Neil D.
Published: July 2007

Ionic liquids (ILs), as separation media, have made significant contributions in the past decades in advancing research in gas chromatography (GC), liquid chromatography (LC), and capillary electrophoresis (CE). This review, covering reports published from the mid 1980s to early 2007, shows how ILs have been used so far in separation science, originally primarily as GC stationary phases and later as mobile phase additives (both millimolar and major percent levels) for LC and CE. Representative GC and LC chromatograms as well as CE electropherograms are shown. In addition, the very recent findings on the development of ionic liquids with surfactant properties and its applications for chiral and achiral analysis are discussed.
Is the metabolic syndrome a useful concept?
Authors: Stanley John
Published: July 2007

The scientific literature is full of references to the metabolic syndrome. At present there are three separate sets of criteria for diagnosing this syndrome. While the same criteria are used in all three definitions the importance assigned to each is different. The WHO definition makes insulin resistance an essential criterion, the ATP III definition gives it equal weight to the other four criteria while the IDF definition makes it a non‐essential criterion. In addition, the role of body weight, body fat and body fat distribution is not clear. These three definitions of the metabolic syndrome have rather lost sight of Gerald Reaven's original formulation of syndrome X which was very clear that insulin resistance and its compensating hyperinsulinaemia are the causes of a variety of metabolic abnormalities which increase the risk of developing cardiovascular disease. Despite its popularity the metabolic syndrome is not a helpful concept.
Non‐invasive measurement of brain viscoelasticity using magnetic resonance elastography
Authors: Sack Ingolf , Beierbach Bernd , Hamhaber Uwe , Klatt Dieter , Braun Jürgen
Published: July 2007

The purpose of this work was to develop magnetic resonance elastography (MRE) for the fast and reproducible measurement of spatially averaged viscoelastic constants of living human brain. The technique was based on a phase‐sensitive echo planar imaging acquisition. Motion encoding was orthogonal to the image plane and synchronized to intracranial shear vibrations at driving frequencies of 25 and 50 Hz induced by a head‐rocker actuator. Ten time‐resolved phase‐difference wave images were recorded within 60 s and analyzed for shear stiffness and shear viscosity. Six healthy volunteers (six men; mean age 34.5 years; age range 25–44 years) underwent 23–39 follow‐up MRE studies over a period of 6 months. Interindividual mean ± SD shear moduli and shear viscosities were found to be 1.17 ± 0.03 kPa and 3.1 ± 0.4 Pas for 25 Hz and 1.56 ± 0.07 kPa and 3.4 ± 0.2 Pas for 50 Hz, respectively (P ≤ 0.01). The intraindividual range of shear modulus data was 1.01–1.31 kPa (25 Hz) and 1.33–1.77 kPa (50 Hz). The observed modulus dispersion indicates a limited applicability of Voigt's model to explain viscoelastic behavior of brain parenchyma within the applied frequency range. The narrow distribution of data within small confidence intervals demonstrates excellent reproducibility of the experimental protocol. The results are necessary as reference data for future comparisons between healthy and pathological human brain viscoelastic data. Copyright © 2007 John Wiley & Sons, Ltd.