IEEJ Transactions on Power and Energy
Online ISSN : 1348-8147
Print ISSN : 0385-4213
ISSN-L : 0385-4213
Volume 118 , Issue 7-8
Showing 1-25 articles out of 25 articles from the selected issue
  • Masayuki Kamimoto
    1998 Volume 118 Issue 7-8 Pages 749
    Published: July 01, 1998
    Released: December 19, 2008
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  • Takeshi Kubo
    1998 Volume 118 Issue 7-8 Pages 750-753
    Published: July 01, 1998
    Released: December 19, 2008
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  • Kosuke Kurokawa
    1998 Volume 118 Issue 7-8 Pages 754-757
    Published: July 01, 1998
    Released: December 19, 2008
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  • Longyun Kang, Yoshitaka Inui, Motoo Ishikawa, Tetsuji Matsuo, Juro Umo ...
    1998 Volume 118 Issue 7-8 Pages 758-766
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The authors numerically investigate the behavior of the Ar-Cs nonequilibrium disk MHD generator connected to the electric power system through the line conunutated inverter. At first, numerical simulations are performed in the case the generator has two electrodes of the anode and cathode and a single 12-phase inverter is connected as the load circuit. The generator is stable and functions as designed at the nominal operating condition. The generator output voltage and current, gas velocity and temperature distributions largely fluctuate due to the ionization instability when the phase-control angle is near 90°. Since this fluctuation has bad effects on the operation of the interconnecting system, some device is needed to reduce its period and amplitude. Next, numerical simulations are performed in the case the load circuit of the generator is divided into two segments by the mid-electrode and two 12-phase inverters are connected individually in these segments. The generator is stable and functions as designed also in this case at the nominal operating condition. It is made clear that the load segmentation is effective to suppress the fluctuation which occurs when the phase-control angle is near 90°.
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  • Yoshitaka Inui, Motoo Ishikawa
    1998 Volume 118 Issue 7-8 Pages 767-774
    Published: July 01, 1998
    Released: December 19, 2008
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    The authors newly develop a two-dimensional design calculation code of supersonic nonequilibrium disk MHD generators which takes the effects of the boundary layer into consideration. Since the electric field strength usually takes almost the same value in both the main flow and the boundary layer, constant electric field strength is adopted as a supplementary condition and the design calculation on the plane including the boundary layer without dividing the flow into the main flow and the boundary layer is realized by applying this condition all over the generator. It can determine the actual generator configuration and detailed two-dimensional quantity distributions including the boundary layer. As an example, a supersonic nonequilibrium disk MHD generator with 50 MW thermal input and 15 MW electrical output is designed by the new two-dimensional design calculation code. Accuracy and necessity of the code are confirmed by comparing the results with the two-dimensional time-dependent simulation results and with the quasi-one-dimensional design calculation results.
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  • Ryuji Matsuhashi, Hisashi Ishitani
    1998 Volume 118 Issue 7-8 Pages 775-780
    Published: July 01, 1998
    Released: December 19, 2008
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    Degradation of the global environment and depletion of resources are threatening sustainable development of humankind In particular, climate change caused by increasing greenhouse gases is one of the most serious issues in analyzing energy systems. This paper aims at proposing frameworks to investigate the sustainability and at estimating technologies to realize sustainable energy systems For this purpose, we first defined the index of sustainability limitations on resource depletion and emissions. Sustainability of mineral and energy resources were evaluated based on the index Estimation indicated that energy resources and CO2 are judged to be unsustainable, and that we should introduce technologies to reduce energy consumption and CO2 emissions Then life cycle energy requirements were assessed on solar power generation systems as representatives of the technologies. Through the life cycle assessment, we quantitatively evaluated measures to improve life cycle energy requirements and capital costs At the same time, we clarified the direction of research and development required for the technologies to realize sustainable energy system.
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  • Mitsuhiro Shiono, Katsuyuki Suzuki, Seiji Kiho
    1998 Volume 118 Issue 7-8 Pages 781-787
    Published: July 01, 1998
    Released: December 19, 2008
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    The Darrieus turbine was developed for wind mill at first. An example of its application to water turbine is found in the Darrieus turbine installed in duct for a low head power generation, but no example is known for application in natural water channel. The anther has developed the Darrieus type turbine, that is suitable for the tidal current power generation with an aim at establishing the tidal current power generation technology through demonstration at test channels and oceans. The efficiency of the tidal current power generation is in fluenced by the characteristic of the turbine. The characteristic of the Darrieus type turbine is mainly affected by a solidity, and a number of blades. So we experimented the Darrieus type turbine at test channels, to find the most suitable values of the rotor solidity and the number of blades. This paper describes and inspects those test results.
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  • Tatsuji Tanaka, Tatsumi Toumiya, Takayuki Suzuki
    1998 Volume 118 Issue 7-8 Pages 788-793
    Published: July 01, 1998
    Released: December 19, 2008
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    Wind mills are important in places like agricultural areas in bad spots, distant islands, mountain divisions and so on which needs power supply . The propeller type wind mill and direct current generator can be used as a small wind force electric generator in such areas. Most of the wind mills used in the present needs a good wind supply without much changers in the speed. But we can not use this kind of systems everywhere, because of the wind environment dose not satisfy these standard. But we have developed a system that functions efficiently according to wind environment of the place. We have used Hill-Climbing method to control the system. So we can set the system to the highest efficiency without knowing the basic input data like wind velocity and system constants. However, in this method it takes time to find the right settings and even could be end up without find the precious settings which gives the maximum output. In order to Settle this problem we have developed a controlling system that can change it's controlling interval according to the changing rate of the electric generator output. The simulation of this system shows the electric energy generation has increase approximately by 12% comparing to the systems with constant controlling intervals.
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  • Tatsumi Toumiya, Eiji Sakaguchi, Tatsuji Tanaka, Takayuki Suzuki
    1998 Volume 118 Issue 7-8 Pages 794-801
    Published: July 01, 1998
    Released: December 19, 2008
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    One of the expected sources of natural energy for the future is wind energy, which has been actively studied as a substitute sources of energy for the world. Not only about wind energy, natural energies of ocean, sun, etc. are clean and safe, but fluctuation of properties are large and has poor reproducibility, so that most important subject is to find out methods to take out those energies effectively. To simulate and control windmill power system by control sequence, we need to obtain the accurate model of the wind power generating system previously.
    It is well-known that neural networks are useful for many problems in nonlinear system because of the ability of learning and nonlinear representation. We apply the neural network method to model a small-scale windmill power system which has a propeller type windmill with a dc generator. We manifested the validity of the proposed method by simulation results from both the simulated results for sinusoidal change of wind speed and natural wind speed by random sequence. Finally, the simulation results are illustrated to show the effectiveness of the modeling method used here for field data of wind speed and windmill speed.
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  • Yasuhiko Hori, Tetsuo Ito, Yasukuni Kuzuma
    1998 Volume 118 Issue 7-8 Pages 802-810
    Published: July 01, 1998
    Released: December 19, 2008
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    For utilizing waste heat effectively, a thermoelectric generation system that can directly convert heat energy into electric power has much possibility. In order to estimate the output power density and the efficiency of the system, it is needed to develop a simulation method of the thermoelectric generation mechanism and heat flow in the system.
    First we made a thermal equivalent circuit in a thermoelectric generation unit as the basic unit of the thermoelectric generation system.
    Second we developed a calculation program that can easily calculate the electric output power density and the efficiency. The radiation and the air conduction in the thermoelectric module also were considered. It was proved that the simulation method was appropriate, since the error by this method was in the range of 7% in electric power.
    According to the above simulation, it can be made the several types of thermoelectric generator (ex. high efficiency-low power density type, high power density-low efficiency type) depending on thermal source conditions by changing the shape of module.
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  • Jongho Lee, Masakazu Wada, Zen-Ichiro Kawasaki, Kenji Matsuura, Makoto ...
    1998 Volume 118 Issue 7-8 Pages 811-817
    Published: July 01, 1998
    Released: December 19, 2008
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    Lightning activity during a winter thunderstorm season around Hokuriku Coast was observed by SAFIR. The SAFIR system has been operating with three detection stations since 1991, and to improve the operation and detection efficiency an additional detection station was installed at the end of November, 1996. Thirty five thunderstorm days and 4427 flashes were recorded during last winter thunderstorm season, from December through late February, and the statistics on lightning activity are derived from the various aspects. The total number of cloud to ground flashes (CG) are 975 of which 42.3 percents are of positive polarity. The diurnal variation of lightning flashes are obtained, and its periodicity is revealed. The maximum of the lightning activity just before dawn is noticed, and perhaps in coincidence with the nighttime land-breeze convergence along the coast. The relation between the thunderstorm occurrence and the meteorological condition is investigated, and it is noticed the stronger monsoon accompanies the higher lightning activity. It is also noticed that both multiplicity and multi point strike-ness show the feature of log-normal distributions with their average 1.4 for multiplicity and 1.2 multi point strike-ness. Futhermore, this is the first paper that statistically discusses the multi point strike-ness.
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  • Toshiaki Ueda, Nobutaka Takeuchi, Toshirou Sugimoto, Toshihisa Funabas ...
    1998 Volume 118 Issue 7-8 Pages 818-824
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    As a generator model to simulate the transfer voltage of a power transformer, surge impedance model has been used so far. This model is representing measured surge impedance of generator as a resistance. The analyzed peak voltage well agrees with measured one, but analyzed time period disagrees with measured one. Other models of generator exist such as Park model and sub-transient reactance model, However, peak voltage and time period of analyzed results has no sufficient agreement with the measurement, because transfer voltage of tested result has significant frequency characteristic when the transformer is connected to a generator.
    This paper proposes a new generator model based on sub-transient reactance model. By this new model the frequency characteristic of transfer voltage can be taken into account, By comparing the calculated results using EMTP with the tested results, the accuracy of the proposed model is confirmed to be satisfactory.
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  • Hisashi Aichi, Toshiro Matsumura, Iwao Miyachi
    1998 Volume 118 Issue 7-8 Pages 825-830
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The temperature rise of the contact spot by Joule's heat under high current flow may result in the softening or welding of the contact materials. Contact resistances of Ag, Cu and Al spot contacts have been observed under the current flow of up to 300A DC. The contact resistances of Ag and Cu with clean surfaces were revealed to be kept constant independent of the magnitude of the applied current flow. On the other hand, contact resistances of Al and Cu with oxidized surfaces were greatly reduced with the increasing current flow.
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  • T. Yamada, T. Takahashi, T. Toda, H. Okubo
    1998 Volume 118 Issue 7-8 Pages 831-836
    Published: July 01, 1998
    Released: December 19, 2008
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    SF6 gas is the most commonly used for insulating gas in the electric power apparatus like GIS, because of its superior dielectrics properties. On the other hand, it is said that the breakdown characteristics in SF6gas under nonuniform electric field is extremely susceptible leading to be lower breakdown voltage. Thus, it is needed to develop the alternate dielectric gas and gas mixture having better insulating characteristics.
    This paper describes the characteristics of partial discharge inception and breakdown strength of gas mixtures in order to substitute pure SF6 gas. As a result, we made it clear that the inception characteristics of the partial discharge in SF6/N2, SF6/CO2, and SF6/CF4 gas mixture show small dependency of mixture rate of SF6 gas, however the breakdown voltages show the significant influence of SF6 mixture rate. This means that the PDIV characteristics mainly depend on the gas having lower PDIV properties, but the breakdown characteristics strongly depend on the PD behavior, that is, the corona stabilizing characteristics. Then, only 1% of SF6 mixture drastically enhances the breakdown voltage of N2, CO2, and CF4 gases. These results show that the N2 based SF6 gas mixture will be one of the substitute candidate of SF6 gas for H.V. power apparatus insulation.
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  • T. Yamada, T. Takahashi, T. Toda, H. Okubo
    1998 Volume 118 Issue 7-8 Pages 837-842
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    SF6 is the most commonly used insulating gas for the electric power apparatus, because of its superior dielectric and chemical properties. On the other hand, it is said that breakdown voltage in SF6 under nonuniform electric field would be significantly decreased. So, gas mixtures with SF6 have been investigated as substitutes for SF6 nowadays.
    We observed current pulse waveforms, light intensity waveforms and light images of PD in different pure gases and gases mixed with SF6. As a result, we found that PD in different pure gases had different characteristics based on the physical properties of gases themselves. In the case of gas mixture with SF6, the PD characteristics differed with that of pure gases, and approached to that of pure SF6 drastically. Moreover, we examined the PD extension length and calculated electric field on the tip of PD. As a result, the extension length of PD tends to be decreased as the content of SF6 increased. On the other hand, the electric field on the tip of PD approached to critical electric field in pure SF6. Thus, the PD characteristics in gas mixture change greatly into that of pure SF6. This is the reason why the breakdown characteristics in gas mixture with SF6 change drastically with small content of SF6.
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  • Masaru Ogawa
    1998 Volume 118 Issue 7-8 Pages 843-850
    Published: July 01, 1998
    Released: December 19, 2008
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    The pressurized 3, 600cm2 cells have been tested to survey life time under elementary practical operation patterns, which have involved start/stops and load changes in the continuos rated operation. According to test, it has been discovered that approximate formulas between voltage changing velocity and generation time can be obtained for operating temperature and operation patterns. By utilizing such formulas, we can calculate the influences of the continuous rated operation, start/stop and load change. Furthermore, we can calculate accelerate ratio of cell life to operating temperature.
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  • Hiroyuki Kikuchi, Noriyuki Okinaka, Yoshiaki Aoki, Naoyuki Kayukawa
    1998 Volume 118 Issue 7-8 Pages 851-859
    Published: July 01, 1998
    Released: December 19, 2008
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    The present paper describes a method for the visualization of the velocity field of a high speed duct flow such that encountered in a magnetohydrodynamic (MHD) channel employing the magnetic resonance imaging (MRI) based on the echo-planar imaging (EPI) pulse sequences. It has already demonstrated by several authors that the MRI using the conventional gradient echo technique could be applicable to low speed fluid flows. However, there are no reports which discuss and apply the high speed echo planar MRI to diagnose the velocity fields of sonic speed range. The one-shot EPI is essential in this case, because a multi-shot excitation and data acquisition procedure is required in the conventional MRI, where so many shots are needed as the number of pixels consisting of the image. Then, theoretical bases were briefly reviewed and the design of the EPI pulse sequences were presented. Finally, a verification experiment was carried out using a shock driven MHD channel with the numerical result which was calculated by a 3D MHD computer code, demonstrating capability of the proposed method.
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  • Tetsuya Suekane, Takayuki Hagita, Tetsuhiko Maeda, Yoshihiro Okuno, Si ...
    1998 Volume 118 Issue 7-8 Pages 860-865
    Published: July 01, 1998
    Released: December 19, 2008
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    Properties of flow field with and without the MHD interaction in a disk closed cycle MHD generator and the effect of back pressure on the performance of the generator are discussed by performing two-dimensional numerical simulations. Without the MHD interaction, for sufficiently low back pressures, an isentropic flow is realized throughout the channel except for the boundary layers. For high back pressures as observed in experiments, pseudo shock waves arise in the channel. The shock system is attached to one wall, and on the other wall a large separation region is observed. The MHD interaction makes the flow field tend to be symmetric. Higher back pressures result in the low Hall parameter and low gas velocity, as a result, the generator performance tends to be low due to the low electro-motive force.
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  • Ryo Hanaoka, Masaaki Takata, Masafumi Suzuki, Kotaro Wada, Kenji Chika ...
    1998 Volume 118 Issue 7-8 Pages 866-873
    Published: July 01, 1998
    Released: December 19, 2008
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    Effects of an area ratio on performances of closed cycle disk MHD generator with cesium seeded argon were studied experimentally. Experiments were carried out by using a shock-tube driven disk MHD generator with a small area ratio. Enthalpy extractions, radial distributions of Hall potential and static pressure, stagnation pressure loss and adiabatic efficiencies were measured. It was found that the adiabatic efficiency increases remarkably with a decrease of the area ratio although the enthalpy extraction decreases. The adiabatic efficiency of 40.5% was obtained and it was the highest compared with previous experiments with the cesium seeded argon. Relations between the adiabatic efficiency and the enthalpy extraction were also studied. Measured relations coincided well with those predicted by a simple analysis and effects of fluid-dynamical boundary layer on the relations were found small even in the present small disk MHD channel. Furthermore, it is suggested that an achievement of high Hall coefficient and a decrease of wall friction are important to improve the disk MHD generator performances.
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  • Hisao Nishikawa, Yasuji Ogami, Masaaki Matsumoto, Koichi Harashima, Ma ...
    1998 Volume 118 Issue 7-8 Pages 874-882
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    It is desirable to establish the acceleration method for phosphoric acid fuel cell durability evaluation in order to promote the PAFC's utilization. Test method may be established through clarifying the mechanisms of deterioration on reaction part of fuel cell. Parametric survay tests were conducted using small size single cells and temperature, current density, pressure were selected as factors which effect on cell voltage deterioration. It was found that the temperature is the key factor which accelerate the cell voltage decay. Fuel cell deterioration's mechanisms and acceleration's factor are described below.
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  • Junichi Nagahara, Kiyotaka Ueno, Akihiko Yokoyama
    1998 Volume 118 Issue 7-8 Pages 883-891
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Control equipment such as automatic voltage regulator, speed governor, and power system stabilizer is designed for a linearized model of a power system around a given operating condition. Because of nonlinearity of the power system, its control performance deteriorates when the operating condition of the power system changes widely. In order to solve such a problem, many studies have been reported on application of new control methods such as H, control, fuzzy control, neuro-control, etc. to generator control and SVC control.
    In this paper, energy function-based neuro-control system (ENCS) is proposed. Furthermore, ENCS is applied to SVC control in order to verify its control performance. Numerical results and discussions based on Equalarea method make it clear that it is hard to determine what kinds of observed variables and how much values of parameters in adaptive neuro-control system (ANCS) the authors proposed before should be chosen. This is because the relation between the objective function of ANCS and the damping of the power system oscillation is not clear. As the objective function of ENCS is closely related with the damping enhancement, on the other hand, ENCS can be easily designed and suppress the oscillation effectively. Moreover, it is shown that plural operating conditions of the power system can be taken into account easily in the design of ENCS.
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  • Masahiko Amano, Masahiro Watanabe, Minoru Banjo
    1998 Volume 118 Issue 7-8 Pages 892-898
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    The objective of this paper is to present a new automatic tuning method of power system stabilizers using Prony analysis. Prony analysis is used for detecting oscillation frequency, damping, phase, and amplitude from power oscillation waveform data. By applying the method to the waveform data of stabilizing signal and internal induced voltage, exciter system phase lag and oscillation frequency can be identified, and control parameters are decided using the identified values.
    Linear combination-type power system stabilizers are effective for dampimg low frequency oscillations using two control input signals, generator power and bus voltage frequency. The control parameters can be directly derived from the oscillation frequency and the excitation system phase lag without using phase compensation.
    Simulation results show that the proposed method is effective both in one machine-infinite bus system and in a multimachine system. The method can be used for off-line controller design and also for on-line adaptive control.
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  • Koji Yamaji, Masaki Azuma, Nobuyuki Honjo, Yasuhiro Noro, Teruo Yoshin ...
    1998 Volume 118 Issue 7-8 Pages 899-905
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
    Harmonic instability is a phenomenon that occurs when the AC and DC side networks in an HVDC system have impedances which result in the amplification of voltages or currents of one particular frequency[5]. It is assumed that harmonic instabilities are caused by several reasons. A number of previous works have focus on an integer order harmonics including 2nd harmonics[6]. Some paper[8] [9] have reported concerning non-integer harmonics. But they have not fully explained mechanism and a quantitative analysis.
    In this paper, a frequency scanning method is introduced to obtain frequency characteristic for HVDC system including the effect of controls. And instability is judged by Nyquist method using locus of open loop transfer function of the AC and DC system. Our analysis shows that countermeasures to reduce static condenser and to reduce lead time constant of automatic current regulator (ACR) are effective to prevent harmonic instability. Simulator test result and digital simulation result are also shown.
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  • Michio Yamada, Shigemitsu Okabe, Tsuneo Kobayashi, Kenji Kawaguchi, Ya ...
    1998 Volume 118 Issue 7-8 Pages 906-907
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
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  • Masatake Kawada, Junichi Abe, Zen-Ichiro Kawasaki
    1998 Volume 118 Issue 7-8 Pages 908-909
    Published: July 01, 1998
    Released: December 19, 2008
    JOURNALS FREE ACCESS
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