bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controllability of arc jet from arc horns with slits
Authors: Sunabe Kinya , Inabe Tsuginori , Fukagawa Hiromasa , Kito Yukio 
Published: July 2007

AbstractUltrahigh‐voltage transmission lines must be protected from lightning surges and the large‐current fault arcs which follow. Horns which are installed at the jumpers on the strain towers have a role in protecting the insulators from the fault arcs by coordinating insulation strength and holding large‐current fault arcs between the horns. Although a flat surface of the electrode tip with a small diameter effectively meets these requirements, it results in the deterioration of corona discharge depressing capabilities in a steady state on power transmission lines. To improve corona discharge depressing capabilities and to reduce deflection of arc jets, finally two types of hemispherical‐shaped arc horn electrodes with slits are developed. The arc jet control performance of those horns was disclosed experimentally as follows:
Two types of arc horn electrodes with our or six slits show remarkable arc jet control performance in the current of larger than 5 kA.
The addition of a rod‐type central electrode at the center of the hemispherical‐shaped electrodes results in the considerable extension of arc jet controllability in the wider current zone by containing the arc spot within the tip area of the central electrodes.
Based on the foregoing results, arc horn electrodes with slits have been designed and utilized for practical application.
High efficiency a‐Si//poly‐Si tandem solar cell
Authors: Horiuchi Toshikazu , Ma Wen , Lim C. C. , Yoshimi Masashi , Hattori Kiminori , Sada Chitose , Okamoto Hiroaki , Hamakawa Yoshihiro 
Published: July 2007

AbstractA series of experimental trials has been carried out to realize the high efficiency a‐Si//Poly‐Si tandem solar cell. Employing p‐type μc‐SiC as a wide‐gap heterojunction window, a‐SiC as an interface buffer layer and n‐type μc‐Si as a back ohmic contact layer, 17.2 percent conversion efficiency has been achieved with the structure of ITO/p μc‐SiC/n Poly‐Si/n μc‐Si heterojunction.Utilizing an optically transparent a‐Si p‐i‐n cell as a top cell and inserting an optical coupler between the top and the Poly‐Si bottom cell, a high total efficiency of 21.0 percent has been obtained so far on the four‐terminal tandem cell. This conversion efficiency value represents a world record for a‐Si basis tandem solar cells.
Current distribution in parallel‐connected YBCO high‐temperature superconducting elements with different critical currents
Authors: Yokomizu Yasunobu , Ito Koji , Matsumura Toshiro , Okubo Hitoshi , Kito Yukio 
Published: July 2007

AbstractA high‐temperature superconductor is investigated for application to a fault‐current limiter. However, the current‐carrying capacity of a single element is too low for practical use. This parallel connection of superconducting elements is required to increase the current capacity. This paper discusses an ac current distribution between two YBa2Cu3O7‐x superconducting elements connected in parallel that differ in electrical aspects such as a critical current level and voltage‐current characteristic.As the instantaneous value of the current rises from zero to peak, the following processes are observed: (1) the transition from superconducting to normal conducting state is initiated in the element with the smaller critical current; (2) the current value in the element is kept constant until the other element with the larger critical current level becomes normal conducting state; and (3) only when the instantaneous value of the ac current exceeds the summation of the individual critical current values of each element does the voltage across parallel‐connected elements appear. These results are caused by the quick recovery characteristic of YBCO superconductors from the normal conducting state to the superconducting state.
Active vibration control of a motor system by using H∞ control theory
Authors: Ouchi Shigeto , Mita Tsutomu , Yano Koji 
Published: July 2007

AbstractThis paper considers the vibration control of a motor system which has a motor and a load connected with a flexible shaft. However, this system often generates a shaft torsional vibration. Traditional methods of treating this problem to adjust the PID controller so that the closed‐loop frequency response is slower than that of the vibration mode. On the other hand, one method has already been proposed in which the vibration is suppressed by a disturbance observer.This paper proposes a new approach based on H∞ control theory. For comparison, a PI control system based on classical control theory also is constructed.The results of several experiments show that compared with the PI control system, the H∞ control system is effective in suppressing the vibration. Further, the H∞ controller obtained in the study consists of a PI controller and a series compensator that functions as an active vibration controller.
Lightweight type linear induction motor and its characteristics
Authors: Osawa Satoru , Yoshimuro Makoto , Karita Mitsuji , Ebihara Daiki , Yokoi Toshiaki 
Published: July 2007

AbstractAt the Institute for Posts and Telecommunications Policy, a postal transportation system has been studied. This system would make use of linear induction motor (LIM)‐driven vehicles for transporting mail between post offices in the Tokyo Metropolitan area. The system would connect the main post offices in the Tokyo area with tunnels circularly constructed underground and would transport mail with linear induction motor‐driven vehicles.In this study, it is found that if vehicle weight is reduced, climbing capability could be considerably improved. Accordingly, the potential for reducing the weight of vehicle‐mounted LIMs has been explored, and a prototype lightweight LIM has been manufactured. This paper reports on the lightweight LIM and its characteristics.
Impedance frequency characteristics of MAGLEV power feed circuits
Authors: Ema Satoshi , Ajiki Koji 
Published: July 2007

AbstractIn Japan, the MAGLEV (magnetically levitated train) is now well along in development testing. The MAGLEV power source must supply a variable voltage and variable frequency source, and contains many higher harmonics which cause many problems such as inductive interference. Thus it is necessary to clarify the impedance frequency characteristics of the MAGLEV power feed circuit.In view of this situation, experiments and investigations concerning the impedance frequency characteristics of the coils for propulsion and the power feeding circuit at the Miyazaki Test Track have been performed but no theoretical analysis has been done.Thus a theoretical analysis was performed in this paper by applying the inverted L equivalent circuit to the coil for propulsion, from which the characteristics of the coils for propulsion were analyzed.In addition, the characteristics of the power feeding circuit could be clarified by assuming the equivalent circuit of the power feeder line.As a result, the measured values and calculated values were almost equal in both the characteristics of the coils for propulsion and those of the power feeding circuit.
Effect of lightning overvoltages on low‐voltage power distribution lines due to direct lightning hits to overhead ground wire
Authors: Imai Yasutomo , Fujiwara Nobuyuki , Yokoyama Hiroshi , Shimomura Tetsuro , Yamaoka Koichi , Ishibe Shinji 
Published: July 2007

AbstractOverhead ground wires and surge arresters have been installed to protect high‐voltage power distribution lines and apparatus from overvoltages induced by nearby lightning strokes. The effects of surge arresters for protection of high‐voltage distribution lines against direct lightning strokes have already been investigated using the digital simulation program EMTP (Electromagnetic Transients Program). With regard to the protection of low‐voltage distribution lines from overvoltages induced by lightning strokes, experimental analyses using a scale model line have been reported.This paper reports on the comparison between the experimental analyses and EMTP simulation of power distribution lines, including low‐voltage lines, and the validity of EMTP simulation. Furthermore, this paper analyzes the overvoltages on low‐voltage power distribution lines against direct lightning strokes to overhead ground wire using the digital simulation.
Hybrid‐type stability control method based on combination of conventional PSS and fuzzy control
Authors: Iskandar Marzan Aziz , Satoh Masashi , Mizutani Yoshibumi , Suzuki Akio , Ishizeki Mitsuo 
Published: July 2007

AbstractThis paper presents a hybrid‐type stability control method based on fuzzy control to improve power system stability. The proposed method consists of a speed deviation input fuzzy controller (F1), an electrical power deviation input analog‐type PSS (ΔP‐type PSS), and a fuzzy judgment mechanism (F2). By using the membership function of the magnitude of speed deviation/acceleration of the generator, the following control schemes are considered. If the magnitude is large, then the supplementary stabilizing signal computed by F1 is used to damp oscillations as fast as possible. Otherwise, the output signal of ΔP‐type PSS is used to avoid undesirable noise effect due to noisy input signal of the speed deviation of F1. The proposed control method increases the power system stability greatly, and it is simple to implement. The effectiveness of the method is demonstrated by one‐machine infinite‐bus and multi‐machine model systems.
Optimal planning of cogeneration systems under time‐of‐use rates
Authors: Asano Hiroshi , Imamura Eiichi , Sogai Shigeio 
Published: July 2007

AbstractFor commercial customers with a cogeneration system (CGS), a mixed integer programming model is used to examine effects of time‐of‐use (TOU) rate structure on the optimal operation of the system as well as its optimal capacity. Three case studies are performed for a hotel, a hospital, and an office building (20,000 m2 in total floor space, respectively). The optimal capacity of the generator under the flat rate is 50 to 70 percent of peak power demand. Effects of the on‐peak/off‐peak energy charge ratio are saturated at a ratio of 5. It is not until an energy charge ratio of between 2 and 5 that the purchase of off‐peak power increases in summer when price reduction is applied to city gas. As the energy charge ratio is raised, cheaper off‐peak power is substituted for city gas and the sum of electricity energy charge and gas energy charge decreases. The simulation results indicate that properly designed TOU rates may provide commercial customers an incentive to operate a cogeneration system with an appropriate mix of the self‐generation and commercial power.
Use of multifield induction machine to determine the characteristics of self‐excited generator systems at variable speed, constant voltage and constant frequency
Authors: Taka Koji , Shibata Fukuo 
Published: July 2007

AbstractThis paper considers a generator system using variable energy such as wind power. The variable energy influences the voltage and frequency of a generator system. However, the load requires constant voltage and frequency. Therefore, this paper proposed that a generator system have the following good points:This generator is a brushless system which makes use of the multifield induction machine;Frequency converter of small capacity which is used for constant voltage and frequency in load at variable speed;The PWM inverter can supply reactive power to the self‐excited generator; andVoltage wave of load is sine wave byLCfilter of the frequency converter.The multifield induction machines of this generator system have 4 poles and 8 poles similar to stator winding. The rotor of the multifield machine is especially cage type. This rotor can transform among the 4‐pole field and 8‐pole field on the stator.In this paper, an experimental study of the brushless, self‐excited, constant voltage, constant frequency, variable speed and sine wave generator system by multifield induction machine is described. The component of this generator system, operation of multifield induction machine, characteristics of generator system, and the effect ofLCfilter in frequency converter are described.
Improvement of partial discharge (PD) resistance of epoxy resin by using sulfur‐containing additives
Authors: Kako Yasuhiko , Watanabe Shigetaka , Higashimura Yutaka , Matsunobu Kenji 
Published: July 2007

AbstractIn the field of high‐voltage engineering, it has been desired for a long time to improve the internal PD resistance of epoxy resin without lowering other properties. Recently, the authors discovered that some sulfur compound as curing agents or simple additives improved the PD resistance of rubber markedly, and here an attempt has been made to apply this fact to the case of epoxy resin.As was expected, some sulfur compounds containing SS‐bond suppress the deterioration of epoxy resin due to internal partial discharges, and the larger the molecular weight of organic group combining the SS‐bond, the longer the effective life of additives. Moreover, to make full use of these additives, it is very important to restrict moisture in the insulation systems.From this study, the authors have proposed the chemical formulation of the suppressive effect of additives for deterioration of epoxy resin due to internal partial discharges.
Fuzzy inference application to planning of distribution network switching
Authors: Imamura Yuzuru , Kanoi Minoru , Kawakami Junzo 
Published: July 2007

AbstractOptimal switching pattern planning is the main subject of distribution network reconfiguration to recover from a blackout or to avoid a blackout due to maintenance and construction. This is a combinatorial optimization problem, and an enumerative check of every pattern is necessary to obtain the optimal solution.In practice, successive heuristic search methods are adopted to obtain the quasi‐optimal solution within a limited computation time. However, a very long computing time is still required when the problem size becomes slightly larger. The step‐by‐step nature of the methods results in many iterations, although it ensures satisfaction of the constraints. Reduction of the iterations is considered to be necessary to enhance processing speed.In this paper, “supply adequacy” is introduced as a new criteria index to guess the solution, which is obtained by fuzzy inference for each possible pair of source and load zone. The reconfiguration pattern is obtained at once or in a few processing steps by assigning to each zone the source with the highest adequacy. Numerical examples show that the proposed method can obtain the solution faster than the ordinary method, more remarkably with the increase of problem size.
Characteristics of discharge induced by laser‐generated plasmas in atmospheric air
Authors: Honda Chikahisa , Muraoka Katsunori , Takuma Tadasu , Akazaki Masanori , Kinoshita Fumihiro , Katahira Osamu 
Published: July 2007

AbstractThe possibility of laser‐induced lightning has been investigated for the future application in the protection of electric power systems from lightning strokes. This technique induces lightning strokes artificially along a laser‐produced breakdown plasma channel and conducts them to a harmless place on the ground.To clarify the plasma formation mechanism and the discharge (sparkover) induction process, sparkover induction experiments are performed for two types of long‐gap electrode configurations, plate‐to‐rod and plate‐to‐plate, with a 50‐J TEA CO2 laser.In the present paper, the sparkover voltage characteristics and interferometric measurement on laser‐produced plasma mainly are described, together with sparkover induction for a series of metal beads arranged equidistantly which simulate a plasma channel.
Power system dynamic equivalence based on a new model reduction technique
Authors: Takimoto Akira 
Published: July 2007

AbstractPower system dynamic equivalents play an important role in the effort to reduce the computational burden of the transient stability analysis of power systems. This paper proposes a new efficient practical algorithm for forming linear dynamic equivalents for power systems based on modal analysis. The main feature of the proposed method is that the accuracy of the equivalent model is greatly improved by converting a coordinate system representing the subsystem from the R‐J coordinate system of the main system to the reference generator D‐Q coordinate system of the subsystem. The order reduction is based on aggregation of similar modes and elimination of the inferior modes without significant effect on the frequency response of the subsystem. Thus the equivalent obtained by the proposed method can be used for both steady‐state and transient stability analysis studies.To verify the dynamic equivalent performance stability simulation results for a model power system composed of 16 generators also are shown.
More intelligent DC railway electrical power systems with traction power control
Authors: Takagi Ryo , Sone Satoru 
Published: July 2007

AbstractThe load of a dc railway has very large peaks while the average power is low. This makes the capacity of wayside power equipment larger. Recently, the ratio of peak power to average power has become even higher because of the introduction of a large number of electric multiple units with a regenerative brake system. This has also made the contact system unreceptiveness of the regenerated energy a significant problem. To solve these problems, researchers are attempting to add intelligence to the power system.This paper describes a novel method of intelligently controlling the traction power of trains. In this system the trains reduce their accelerating power to cut current peaks in wayside substations. With the proposed method the load peaks can be reduced by up to 31 percent, which means that the characteristics of the railway load have been changed drastically. The delays of the trains involved are negligible. Also, the unreceptiveness of the regenerated power can almost be eliminated.In the first part of this paper, the idea of traction power control is described. Then a description is given of how the idea is applied to wayside substation load peak suppression or receptiveness improvement, with some simulation results to prove the method. Finally, the possibility is discussed of further improvement of the system by adding communication capability between trains and wayside equipment.
Reluctance control magnetic suspension system—suspension system with permanent magnet and linear actuator
Authors: Higuchi Toshiro , Oka Koichi 
Published: July 2007

AbstractA new type of magnetic suspension system is proposed which uses a permanent magnet. In this system, the attractive force is adjusted by controlling the reluctance of the magnetic circuit. Since no electromagnet is necessary, this system is effective for saving energy and avoiding heat generation. The composition of this paper is as follows.First, the principle of this suspension system is explained and various types of magnetic circuits are introduced for reluctance control. Second, the possibility of one of them is examined from the viewpoint of linear control theory. Third, an experimental device is developed based on the proposed suspension method. The reluctance of this device is controlled by the air gap which is between the magnet and the suspended object, and which is adjusted by driving a permanent magnet by piezoelectric actuator. Experimental results support the theoretical predictions well.
Development of XLPE insulated DC cable
Authors: Maekawa Yuichi , Yamaguchi Akio , Hara Makoto , Sekii Yasuo 
Published: July 2007

AbstractThis paper describes the development of dc XLPE cable. Through a series of material investigations, an XLPE compound containing highly purified special filler was developed.To check the dc insulation performance of the cable insulated with this new material, a prototype cable with 9 mm insulation thickness was manufactured. It was confirmed that the performance of the prototype cable was excellent. Based on the study of the prototype cable, a 250‐kV dc cable with 20 mm insulation thickness was designed and manufactured. Through a series of voltage tests, excellent dc insulation performance of the developed cable was verified.
Preventive control based on complex‐valued load‐flow technique to avoid voltage instability in power systems
Authors: Kameoka Naoki , Kita Hiroyuki , Tanaka Eiichi , Hasegawa Jun , Nishiya Ken‐Ichi 
Published: July 2007

AbstractThis paper presents a method for obtaining preventive control strategies based on nonlinear optimization for power systems which will incur voltage instability when load demand increases. An algorithm is proposed to determine an appropriate and effective control action taking into account the operating constraints to widen the margin between the present operating point and a voltage collapse point, thereby improving the system state.The method proposed here is based on a complex‐valued load‐flow technique using the Newton‐Raphson method which has been developed already by the authors. Consequently, the preventive control algorithm also can evaluate the voltage instability in the event the present operating point becomes closer to the critical point and the system state becomes unfeasible at increased loading point. Further, in optimization, two‐types of objective functions are introduced so that voltage stabilization and dissolution of constraint violation can be attained simultaneously. In addition, this paper discusses the extension of the proposed preventive control to the successive control method which carries out the control action to avoid voltage collapse while the load demand is increasing. Numerical examples for various model systems demonstrate the effectiveness of the proposed method.
Vector‐controlled induction motors using neural network
Authors: Shimane Kazuo , Tanaka Shigeru , Tadakuma Susumu 
Published: July 2007

AbstractSlip‐frequency vector control generally is used for variable speed induction motor drives due to its excellent response characteristics. However, it is sensitive to the variation of motor parameters since the flux current and slip‐frequency commands are computed using the motor parameters. As a result, the system performance will be degraded if the controller parameters do not match the motor parameters.The authors propose a new approach of vector control in which quick responses and system robustness are obtained concurrently by the learning capabilities of neural network. In the newly developed method, controller parameters are learned in real time at medium and high speeds. Using these learned parameters, the low‐speed performance of the controller can also be improved greatly.This paper describes the theoretical analysis, simulation and experimental results of the proposed method.
A parameter tuning for dynamic simulation of power plants using genetic algorithms
Authors: Miyamoto Yuichi , Miyatake Tatsuya , Kurosaka Soh , Mori Yoshinobu 
Published: July 2007

AbstractThis paper reports a method of dynamic simulation parameter tuning for a coal‐fired power plant using genetic algorithms (GA). GA is a search algorithm based on the mechanics of natural selection and natural genetics. GA also is one of the effective methods for optimization problems and it requires a formalization of problems and a fitness function definition. Because the dynamic simulation can be repeated and the error between real data and simulation results is defined by a fitness function, it is reasonable to consider genetic operations.To satisfy environmental laws and regulations, the control of NOx emission is important for the operation of power plants. Therefore, an NOx analytical model is designed and used for the dynamic simulation at the change of loads, the kind of coal, and so on. In this paper, the optimal parameters for the simulation are determined by GA.