bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability analysis of a controlled‐current source‐fed induction motor vector control system without a speed sensor
Authors: Tsuji Mineo , Yamada Eiji , Izumi Katsuhiro , Oyama Jun 
Published: July 2007

AbstractOne of the representative vector‐controlled induction motor drive systems without a speed sensor is composed of a rotor flux estimator, a PI torque current controller and a conventional vector‐controlled current source. However, the stability analysis of this system has not been reported.In this paper, the flux estimator is interpreted as a flux observer. Then a linear model of the system is proposed by deriving the equations of the flux estimator in a synchronously rotating reference frame. By computing the trajectories of the poles and zeros and the transient responses, the following results are obtained.(1) If the rotor flux is estimated using only the stator equations (voltage model), the system becomes unstable when the actuator stator resistance is smaller than the value used by the controller.(2) By choosing a small time constant of the first‐order lag element in the flux estimator (reciprocal number of observer gain), the poles and zeros on the imaginary axis move to the stable region. However, another pair of poles has reverse performance.(3) From the viewpoint of stability, the gain of the PI torque current controller should be chosen as large as possible and the stator and rotor resistances in the controller should be set to values smaller than their actual values.
Practical design of superconducting generator—electrical characteristics equations
Authors: Maki Naoki 
Published: July 2007

AbstractA superconducting generator (SCG) consists of a nonmagnetic cryogenic rotor, which contains a super‐conducting field winding cooled by liquid helium, and an airgap armature winding, which makes it possible to obtain a high magnetic field in the airgap. Since the SCG construction differs from that of the conventional generator, practical application requires that its electrical and mechanical design methods be established.This paper describes electrical characteristics equations of the SCG, electromagnetic shield characteristics of double dampers and proof test results of a 50‐MVA experimental SCG. Equations for the generator parameters (voltages, output capacity, reactances, time constants, flux densities), which are useful for the practical design of the SCG, are derived from two‐dimensional electromagnetic analysis considering winding thickness and the edge effect. From comparison with measured and calculated values of no‐load, sudden 1–3 phase short‐circuit and slip extended tests, these equations were confirmed as valid.
A new voltage control equipment using fuzzy inference
Authors: Takahashi Tsuyoshi , Kitou Masahito , Asai Michio , Kido Mitsuyasu , Chiba Tomio , Kawakami Junzou , Matsui Yoshiaki 
Published: July 2007

AbstractPower system control equipment needs higher sensitivity and operational reliability. Advanced voltage control equipment is needed for reducing the frequency of tap changes and improving the characteristics (the relationship between the actual voltage and reference voltage) of the voltage to meet today's power system requirements. However, these objectives are in a trade‐off relationship. Studies of voltage control derived from a knowledge base suitable for electric power systems can satisfy these objectives using fuzzy inference. Compared with corresponding conventional equipment, the new equipment improved the deviation of 30 min average voltage of 30 percent.This paper describes the design concept of new voltage control equipment using fuzzy inference. In addition, field test results are described along with rules of fuzzy inference, membership functions, and the deviation of 30 min average voltage through detailed simulation.
A rapid solution for the maximum loading point of a power system
Authors: Kataoka Yoshihiko 
Published: July 2007

AbstractThis paper presents a new solution method for computing the maximum loading point of a bulk power system under the condition where the loads of the nodes can be parameterized by a scalar which is the loading level of the system.A special loading model, in which the loading level of the system depends on the voltage magnitude of a loading node, is adopted for the purpose of releasing the load‐flow computation from the ill‐condition near and at the maximum loading point. The loading level of the system is unknown in the aforementioned loading model. The maximum loading point is obtained by adjusting the operating parameter so as to achieve the maximum loading.The operating parameter is adjusted in the converging process of the Newton‐Raphson iterative computation. The adjustment is computed based on the least squares estimation using the data set which is obtained from its own iteration process.It is shown in numerical examples that the proposed method is satisfactorily rapid, stable, and accurate.
IR detectors using Pb(Mg1/3Nb2/3)O3 and Pb(Sc1/2Ta1/2)O3 ceramics under DC bias
Authors: Fukushima Toshihiro , Kato Kazuaki , Ohsumi Shuzo , Takenaka Tadashi 
Published: July 2007

AbstractRecently, one type of thermal‐type IR detector, the pyroelectric sensor, has become of great interest in commercial applications, because of its ability to operate without cooling, its constant detectivity independent of wavelength, and its low cost. The conventional pyroelectric materials are usually normal ferroelectric materials with a first and second phase transition. The working temperatures are sufficiently below the Curie temperature Tc for stable responsivity to temperature. Electric field induced‐type pyroelectric sensors have also been proposed. Relaxor ferroelectric materials such as Pb(Mg1/3Nb2/3)O3 (PMN) and Pb(Sc1/2Ta1/2)O3 (PST), which have a glassy Curie temperature near room temperature, are used in this type of sensor.This paper describes the sensor properties of electric field induced‐type pyroelectric sensors prepared by using PMN and PST ceramics as compared with the conventional type sensors. Material evaluations of PMN and PST ceramics were made to determine their dielectric and pyroelectric properties. PMN shows excellent induced pyroelectric properties for the sensors over a wide range of temperatures. On the other hand, PST seems to be inadequate for an IR detector because of a very narrow high‐response temperature range. The sensors with PMN and PST ceramics show enhanced pyroelectric activities under dc bias field. The measured sensor voltage responsivities agree with the calculated values for the PMN case. The electric field induced‐type infrared sensor with thick or thin film materials seems to be satisfactory as linear array IR detectors for thermal imaging, with application of a higher electric field.
Design of single‐sided linear induction motors using a nonlinear optimization technique
Authors: Higuchi Tsuyoshi , Nonaka Sakutaro 
Published: July 2007

AbstractBoth low‐speed wheel‐on‐rail and the medium‐speed Maglev transport system with single‐sided linear induction motor (SLIM) propulsion have been in practical application.This paper presents the method of optimizing the design parameters of SLIMs using the nonlinear optimization method. The optimization problem is formulated by the use of the design formulas taking into account the end effect, skin effect and airgap leakage, and the transformation method and the simplex method are applied to solve the problem.Seven parameters, such as the number of poles, the pole pitch and the stack height, are chosen as the independent variables. The output kW/input kVA, the maximum flux density in the core teeth, the temperature increase, the primary length, the stack height and the maximum thrust are selected as the constraint functions. The performance characteristics are estimated using space harmonic analysis as well as the approximate equations.The method is applied to the SLIM design for urban transit, and the maximum speed is about 70 km/h. As the transformation methods, the interior point transformation and the exterior point transformation are compared from the viewpoints of accuracy and CPU time. The design is analyzed under several objective functions, the primary weight, the input kVA and the cost of secondary materials.
Realization of the powering/regenerative operation of the induction motor by the parallel resonant power converter and proposal of a novel circuit topology
Authors: Yang Seung Hak , Harashima Fumio , Takizawa Satoki , Kondo Seiji 
Published: July 2007

AbstractA resonant power converter for the low switching loss power conversion must be achieved for high‐frequency zero voltage switching or zero current switching. The important matters of the continuation of resonant phenomena are the control strategy of resonant initial current and the clamp circuit for suppressing the resonant link voltage.The control strategy of the resonant initial current is discussed and the powering and regenerative operation are shown successfully in the steady state and transient state by experimental test.Finally, a new resonant dc link dual converter system is proposed and it is confirmed that the voltage stress of the resonant capacitor and the rms value of electrolytic capacitor current are decreased with experimental test also.
Effect of the stator slot opening on the electromagnetic vibration in a squirrel‐cage induction motor
Authors: Onodera Satoru , Yamasawa Kiyohito 
Published: July 2007

AbstractField harmonics produce a radial electromagnetic force in a squirrel‐cage induction motor with a particular number of rotor slots corresponding to the number of poles. The radial force causes vibration and acoustic noise.In this paper, a simplified equation for the radial force at no‐load is introduced, and the relation between the width of the stator slot opening and the radial force is discussed quantitatively. The field harmonic component produced by the interaction between the fundamental magnetomotive force due to the stator current and the pulsation of air‐gap permeance dominates for the radial force.Furthermore, the vibration of the stator core due to the radial force is calculated under a simple assumption. The calculated results are verified by experiments.
Water mist formation in vapor‐mist dielectrics and its effect
Authors: Nagaki Yasunari , Itabashi Satoru , Mitsui Hideo , Sone Mototaka 
Published: July 2007

AbstractIt has been proposed that vapor‐mist dielectrics in which mixing liquid droplets such as tetrachloroethlene in a gas have the ability of increasing flashover, impulse voltage, and of suppressing partial discharge. Vapor‐mist methods have been performed on other materials and the effect of the mist can also be obtained on benzene, hexane, and even water as general materials. Although these studies have been carried out, neither the discharge mechanism on vapor‐mist nor the reason for the increase of the discharge voltage is understood fully because the mist is of various sizes. On the other hand, agglomeration of water molecules can be studied with the FR‐IR method, and are classified into monomer, dimer, trimer (including polymer). Water gives mist stats which are significant in discussing effects.This paper describes states of water mist and their effect under nonuniform field with positive and negative polarities. Water mist in vapor exists as dimer and trimer, and their amount decreases with the reduction of temperature. These mists have no effect on discharge suppression. However, when the mists are formed by space charges, the inception voltage is increased by these mists in the negative polarity.
Residential solar‐powered air conditioners
Authors: Tanaka Kunio , Makino Yasuhiro , Sakoguchi Etsuo , Takeoka Akio , Kuwano Yukinori 
Published: July 2007

AbstractThe power demand in Japan increases yearly especially in summer, and peaks in the daytime. The main cause is the drastically increased load of air conditioners used widely in general residences. The load pattern of air conditioners is very similar to the output pattern of a photovoltaic (PV) array.Therefore, Sanyo has been developing two types of residential solar‐powered air conditioners. One is a unidirectional system by using a dc/dc converter which controls the voltage of a PV array at its optimal operation point and boosts the voltage up to the dc voltage of an inverter‐type air conditioner. The other is a bi‐directional system by using a bi‐directional current‐control converter, which regenerates surplus power into a commercial system from a PV array, and suppresses the input current distortion of an air conditioner.In this paper, the configurations and experimental results are described and discussed.
An evaluation of the optimal generation mix for controlling carbon dioxide emissions
Authors: Tanabe Ryuya , Yasuda Keiichiro , Yokoyama Ryuichi 
Published: July 2007

AbstractThis paper presents an efficient computational algorithm for selecting the optimal generation mix considering CO2 emissions. To demonstrate the effectiveness and feasibility of the proposed method, a fundamental study of the evaluation of the optimal generation mix for controlling CO2 emissions is indicated. Furthermore, by using a parametric analysis which considers load characteristics as parameters, a general trend for the optimal generation mix which is affected by controlling CO2 can be derived.The proposed method is based on an optimization method known as simulated annealing. In the method, solutions in a generation mix problem are equivalent to state of a physical system, and the cost of a solution is equivalent to the energy of a state. The proposed method can easily accommodate not only CO2 emissions but also many practical constraints of generation expansion planning, such as integer solutions of unit capacities, condition of existing units, and so on.Case studies with various annual load patterns (combinations of annual load factors and the shapes of annual load duration curve) are presented and discussed. Consequently, a general trend for selecting generation technologies that should be added to a power system is derived, i.e., a useful guideline for studying generation expansion planning under controlling CO2 emissions can be provided.
Configuration optimization for a coupled 200‐MWe MHD channel and magnet coil system
Authors: Nishimura Ryo , Aoki Yoshiaki , Kayukawa Naoyuki 
Published: July 2007

AbstractThis paper reports on the results of the optimization of the cross‐sectional shape of a magnet coil system including an MHD channel. This optimization was carried out for a 200‐MWe supersonic Faraday‐type MHD generator. It was shown that the channel length can be shortened more than 30 percent, without the decrease of the enthalpy extraction by the optimization of the coil shape from the crescent shape coil producing a uniform magnetic field. It was estimated also that the capital cost for a commercial MHD/steam combined plant can be decreased more than 6 percent by this coil shape optimization.
Investigation of impedance and line parameters of a finite length multiconductor system
Authors: Ametani Akihiro , Ishihara Akiko 
Published: July 2007

AbstractThe earth‐return impedance and capacitance formulas of a finite parallel multiconductor with arbitrary positions have been proposed. A comparison with measured results has proved that the accuracy of the impedance formula is satisfactory. By applying the formulas, the characteristics of the finite line parameters such as a propagation constant and a characteristic impedance are investigated in comparison with those given by the conventional assumption of an infinite line. The impedance of the infinite line is greater and the capacitance is smaller than those of the finite line. The difference increases as the line length and source frequency decrease, and the height, radius and separation distance increase. According to the foregoing, the attenuation constant and the characteristic impedance of the infinite line are greater and the propagation velocity is smaller than those of the finite line.
Development of unbalanced load flow program for large power systems
Authors: Suzuki Mamoru , Ishii Takahiro , Kamio Mitsukazu , Suzuki Hiroshi , Iba Kenji 
Published: July 2007

AbstractThe idea of unbalanced load flow calculation was proposed many years ago. At that time, however, the needs for such techniques was not urgent. Modern power system networks are comprised of long untransposed transmission lines. Therefore, for some kinds of analysis, it is now almost impossible to treat a system as though it were a symmetrical network. The aims of most previous studies were oriented to solve voltage/current imbalance in local or small systems, as local imbalance was a serious concern. This is still an important issue, but more recently needs have become concentrated on practical bulk power systems, since principal EHV lines are entirely untransposed.In this paper, the development of practical unbalanced load program and practical experience with it are reported. This program was developed for steady‐state analysis of large‐scale practical networks under many possible unbalanced conditions. The Newton‐Raphson method in polar coordinates is used, since fast and moderate convergent characteristics are suitable for solving solutions. The program was applied to practical case studies. The models contain all of the 500‐kV and most of the 275‐kV overhead transmission lines in TEPCO. Since the density of the Jacobian matrix is higher than in single‐phase load flows, the number of nonzero elements is extremely large. Convergent characteristics are excellent in all cases. The fear of numerical instability has been allayed.
Active‐passive power circuit
Authors: Funato Hirohito , Kawamura Atsuo 
Published: July 2007

AbstractThe recent development of a semiconductor device technology realizes small‐size, lightweight, high performance power switching devices. However, reactive elements such as an inductor or a PWM inverter achieves high‐performance current control, which is applied to the active filter, and so on [2, 4]. If a compact and high efficient reactive component is developed, the power converter technology may drastically change the application field.In this paper, the concept of variable active‐passive reactance (VAPAR) which consists of an inverter and passive elements is proposed. The VAPAR behaves like a two‐terminal reactive element and the produced active reactance component works as a passive reactive component, including in transient state.The principle of VAPAR and two possible control schemes to realize VAPAR are realized. Through simulations and experiments, it is verified that VAPAR shows reactive characteristics not only in steady state, but also in transient state, as proposed, and basic characteristics of both control schemes are clarified.
Degradation diagnosis and estimation of residual life of insulating material using pattern recognition of phase‐angle resolved partial‐discharge pulse‐occurrence distribution
Authors: Komori Fumitaka , Nishiguchi Noriaki , Hikita Masayuki , Mizutani Teruyoshi 
Published: July 2007

AbstractA prototype of partial discharge (PD) pulse measurement and degradation diagnosis expert system (PDM/ES‐I) is constructed using a personal computer for insulation degradation diagnosis of materials experiencing PDs. For 0.1‐mm‐thick low‐density polyethylene (LDPE) with CIGRE Method II electrode system, temporal change of phase‐angle‐resolved PD pulse occurrence distribution was measured with PDM/ES‐I.The so‐called “pattern recognition” of the PD pulse distribution is applied to diagnosis of insulation degradation and assessment of residual life. Experimental results revealed that in spite of large scattering of time to breakdown, i.e., life, from 5 to 43 hours, all the tested samples exhibited similar evolution of the profile of PD pulse occurrence compared with five standard normalized PD patterns which had been registered in advance as five representative degradation stages from the initial degradation category to the final one.The degradation stage determined by the pattern recognition (PR) method proved to vary from the initial degradation category to the final one in a correct turn. Consequently, the PR method permitted an exact determination of the degree of degradation at a given aging time. In other words, the PR method was capable of predicting the residual life of LDPE with a CM‐II electrode system.
Electrical resistance of electroconductive plastic composite with carbon fiber filler
Authors: Katsumata Makoto , Endo Morinobu , Yamanashi Hidenori , Ushijima Hitoshi 
Published: July 2007

AbstractTo obtain a new electroconductive composite, the vapor‐grown carbon fiber (VGCF) has been applied to the thermoplastic resin composite as a conductive filler. The stability of electrical conductivity of the composite is investigated.The resistivity of VGCF composite is 1.7 × 10−1 Ω·cm at room temperature which is one order smaller than that of commercial grade composites with carbon filler. The stability of electrical conductivity, under temperature change (−35 to +60°C) and for exposure tests (at room temperature and at 60°C), the VGCF composites have high degree of stability. The stability of electrical conductivity of the present composites are superior to those of conventional carbon fibers such as PAN‐based, under tensile stresses and bending stresses. It is suggested that the fine conductive networks in the present composites give rise to these desirable performances.
Quenching current level coordination in superconducting power transmission systems
Authors: Tang Yue‐Jin , Yokomizu Yasunobu , Hayakawa Naoki , Goto Yasuyuki , Matsumura Toshiro , Okubo Hitoshi , Kito Yukio 
Published: July 2007

AbstractIn the present power transmission system, electric power devices are equipped under the concept of insulation coordination and are protected from lightning overvoltage and switching surge by the arrester. However, the future superconducting power transmission system is characterized by the heavy current transmission capability, the lower transmission loss and lightning‐surge‐free circumstances. Thus, in the superconducting power transmission system, superconducting devices should be protected rather from quenching by the overcurrent of a short‐circuit fault than from the breakdown by over‐voltage.In this paper, a new concept of the coordination for the superconducting transmission system is proposed as a “quenching current level coordination” instead of the insulation coordination. Furthermore, it is pointed out that the quenching current level coordination has the duality relationship with the present insulation coordination. A superconducting fault current limiter should play an important part of the quenching current level coordination to prevent the other superconducting devices from quenching.