bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composite power systems reliability evaluation based on demand‐side reserve
Authors: Mottate Yasunori , Saitoh Hiroumi , Toyoda Junichi 
Published: July 2007

AbstractThis paper proposes new demand‐side reliability indices and useful computational methods for reliability evaluation of composite power systems. These new indices are based on the active power which can reach each demand spot under generating and transmission network constraints. This conception is defined as “reachable power,” and it leads the reserve margin on each demand spot, which is called as “demand‐side reserve.” If the reachable power is insufficient to satisfy the demand, load curtailment is required.In the proposed approach, the conception of the load curtailment area is defined, and the estimate method of load curtailment area is indicated. In case the reachable power exceeds the demand, system reliability is evaluated by the demand‐side reserve, and the power system is divided into several reliability zones according to the demand‐side reserve levels. Small system examples are used to illustrate principles of the proposed approach, and middle system examples show the effectiveness and practicality.
Method for analyzing eddy currents in moving conductors
Authors: Muramatsu Kazuhiro , Nakata Takayoshi , Takahashi Norio , Fujiwara Koji 
Published: July 2007

AbstractWhen magnetic fields in electrical machines with moving conductors such as linear induction motors are analyzed, eddy currents due to the movement of conductors should be taken into account. Although two kinds of coordinate systems (moving and fixed coordinate systems) can be applicable to the analysis of eddy currents in moving conductors, the advantages and disadvantages of both coordinate systems are obscure.In this paper, methods for analyzing magnetic circuits with moving conductors are classified systematically, and the moving and fixed coordinate systems are compared with each other from the standpoints of accuracy, memory requirement, and CPU time. It is shown that the moving coordinate system is superior to the fixed coordinate system for transient analysis.
Steady‐state characteristics of matrix converter
Authors: Oyama Jun , Higuchi Tsuyoshi , Tsukamoto Ryuta , Haraguchi Takehisa , Yamada Eiji , Koga Takashi 
Published: July 2007

AbstractThe matrix converter proposed by Venturini is very simple in structure and has powerful controllability. However, there are few applications especially in power electronics fields. This seems to be caused mainly by the fact that such power devices that were fast enough to suppress ringing oscillations in the supply lines and large enough to pay for more devices and more complicated control circuits than in conventional dc‐link converter‐inverter systems were not available. At present, static induction thyristors (SIThs) have been introduced and a new possibility for the matrix converter has been raised.This paper describes a new control strategy which is simple and practical and allows the output voltage of 0.866 times the supply voltage to be generated. Also, the new firing sequences which eliminate voltage and current spikes are proposed. Steady‐state and distortion characteristics of the prototype PWM matrix converter with SITh are shown.
Neural‐network steering control of an automated guided vehicle
Authors: Funabiki Shigeyuki , Mino Michio 
Published: July 2007

AbstractWith the progress in factory automation in industry has come the demand for higher speed drive and performance for an AGV (automated guided vehicle). A new steering control of the AGV by fuzzy control has been proposed to replace the PI control. However, much time is required to investigate the regulations and to adjust the scaling factors for excellent performance in the fuzzy control.In this paper, a new steering control for an AGV based on the neural network using the backpropagation method is proposed. The good steering control results by the fuzzy control are adopted for the teaching signal of the neural network. First, the effect of the number of learning and the learning errors on the steering control results are discussed by computer simulation using the AGV model. Further, the ability of generalization in the turning radius and the traveling speed also are investigated. It becomes clear that the AGV can travel along a designated route provided the neural network learns both the right and left turning at the maximum traveling speed and the minimum turning radius. Then it is proved by an experiment using the AGV constructed for the test that the proposed steering control method is very affective.
Performance evaluation of solar‐powered air conditioner
Authors: Tanaka Kuniho , Ding Lu , Makino Yasuhiro , Sakoguchi Etsuo , Takeoka Akio , Yamada Eiji 
Published: July 2007

AbstractWith present‐day global environmental and energy problems, high expectations exist for solar power generation to reduce carbon dioxide generated by the consumption of fossil fuels.On the other hand, power consumption in residential homes is increasing every year. Among the many household appliances, the power demand for air conditioners increases dramatically during the summer, particularly in the afternoons. Since this pattern closely matches the output pattern of solar cells, it should be possible to combine a photovoltaic array with an air conditioner to decrease the energy consumption within the home.In this paper a residential solar‐powered air conditioner is developed that operates through a combination of photovoltaic array and commercial power. Also, the configuration and specification of the solar‐powered air conditioner are described, and its performance characteristics are examined by analysis of the characteristics of the solar cell.
Long‐term load forecasting using improved recurrent neural network
Authors: Hayashi Yasuhiro , Iwamoto Shinichi 
Published: July 2007

AbstractIn general, electric power companies must prepare power supply capability for maximum electric load demand because it is very difficult at present to store electric power. It takes several years and requires a great amount of money to construct power generation and transmission facilities. Therefore, it is necessary to forecast long‐term load demand exactly in order to plan or operate power systems efficiently. Several methods have been investigated so far for the long‐term load forecasting. However, because the electric loads consist of many complex factors, good forecasting has been very difficult.This paper proposes a long‐term load forecasting method using a recurrent neural network (RNN). This is a mutually connected network that has the ability of learning patterns and past records. In general, when interpolation is used for unlearned data sets, the neural network provides reasonably good outputs. However, when extrapolation is used, such as in long‐term load forecasting, some kind of tunings have been necessary to obtain good results. Therefore, to solve the problem, a method is proposed in which growth rates are used as input and output data. Using the proposed method, successful results have been obtained and comparisons have been made with the conventional methods.
Characteristics analysis of superconducting power transformer without iron core
Authors: Yamaguchi Hiroshi , Sato Yukihiko , Kataoka Teruo 
Published: July 2007

AbstractWith the progress of superconducting wires for ac power use, research on superconducting power transformers is increasing. These transformers can be divided into two types: the iron‐core type [1, 2]; and the air‐core type [3–9]. The latter type has such advantages as absence of iron losses and magnetic saturation, and greater possibility of reduction of size and weight. However, the air‐core transformer has a large magnetizing current due to the absence of iron core. Hence, research has been carried out on the possibility of using the air‐core transformer also as a shunt reactor in a power transmission system. However, the operating characteristics of the air‐core transformer, such as voltage regulation and reactance voltage, are not clear at present.In this paper, the equivalent circuit without losses is proposed first. Since this equivalent circuit is expressed by means of the magnetic coupling factor and self‐inductances of windings, the effect of these parameters on the transformer characteristics can easily be investigated. Then, based on this equivalent circuit, the per‐unit expressions for the air‐core transformer characteristics are derived and the characteristics are analyzed in detail. The validity of the theoretical results are confirmed by experimental results obtained by the use of an experimental superconducting transformer.
Low torque pulsation and high‐power control of permanent magnet motor with distributed electromotive force
Authors: Osawa Hiroshi , Hashii Makoto , Matsuda Naotaka , Endoh Kenji 
Published: July 2007

AbstractThis paper describes low torque pulsation and high‐power control of permanent magnet synchronous motor (PM motor) with distorted electromotive force (emf).The experimental model of PM motor is a 40‐kW, 190 r/min, salient‐pole, six‐phase machine. An individual single‐phase transistor inverter is connected to each phase of PM motor as a power source. By adopting full pitch and concentrated winding in the armature of the motor, the rate of flux utilization and output torque per mass can be increased. This winding causes trapezoidal distortion in the phase voltage waveform at no load. For realization of high‐performance control of PM motor, the current waveform should be determined so as to minimize torque pulsation and to maximize the output torque of the motor under the rated current.This paper proposes also the method to determine the optimum current waveform. The currents and emfs are expressed as N‐dimensional vectors (N: the number of phases). Due to the characteristics of the particular structure of the motor, the armature reaction is small enough to be neglected. In this case, the optimum current vector can be derived under two conditions: (1) the direction of the current vector always agrees with that of the emf vector; and (2) the scalar product of the two vectors is held constant. Supplying the optimum current vector provides no torque pulsation and the nearly maximum output torque under the rated current. This method also can derive the new optimum current corresponding to open‐phase operation.The validity of the method is confirmed experimentally. The characteristics of the experimental model of PM motor also are described in this paper.
Chaotic behavior in parametric oscillations
Authors: Tatsuta Fujio , Tadokoro Mutsuo 
Published: July 2007

AbstractParametric oscillations which occur in a nonlinear two‐phase circuit with nonlinear reactors and capacitors are applied to many kinds of power devices. When the devices are operating under light load, the output voltage of these devices exhibits unstable oscillations, i.e., subharmonic oscillations, quasi‐periodic oscillations or chaotic oscillations. This paper analyzes the abnormal oscillations and confirms the validity of the analysis experimentally.In this paper, new circuit equations are presented that can be applied to the analysis of a two‐phase nonlinear circuit in which reactor saturation curves are sharp. It is clarified by this analysis that the parametric oscillations of the circuit which contains reactors of moderate saturation characteristics become subharmonic or quasi‐periodic with the existence of resistances of the power supply side. Also, when the nonlinearity of the reactors in the circuit is sharp, the parametric oscillations may change into chaotic oscillations in addition to the aforementioned oscillations.
A numerical integration method for long‐term power system dynamic simulation
Authors: Inoue Toshio , Taniguchi Haruhito , Ichikawa Tatsumi 
Published: July 2007

AbstractLarge power system frequency/voltage fluctuations due to severe faults in trunk transmission lines or major generating units may trip‐off other facilities and result in large‐scale power system blackout. To prevent such blackout, development of an accurate and fast long‐term power system dynamic simulation tool is required. With respect to the development stage, selection of a numerical integration method available for step‐size adjustment, and the development of a scheme for the adjustment are principal subjects.The trapezoidal and the second‐order Gear methods were selected as possible candidates for the step‐size adjustment from the viewpoint of numerical stability. The trapezoidal method is selected from the viewpoint of accuracy and applicability to power system dynamic simulations.A new scheme for the automatic step‐size adjustment is proposed for the trapezoidal method to achieve fast simulation of the long‐term power system dynamics. The validity of the proposed scheme is verified through simulation studies on a single‐machine‐to‐infinite bus system.
Improvement in stabilization of launching performance and launching velocity using linear accelerator
Authors: Ebihara Daiki , Watada Masaya , Nagashima Kenji 
Published: July 2007

AbstractThis paper describes the improvements in launching stability and launching velocity of the linear accelerator (LAC).The authors have designed and produced a railgun using the LAC for weaving loom shuttles. The LAC is an electromagnetic launcher which enables a projectile to be launched at a speed of more than 50 m/s. Basically, it consists of a unipole linear dc motor and operates the same principle as dc rotary motors, the most difficult problem in this system being the stabilization of the current collection on the projectile.Then, various launch experiments have been conducted. As a result, the carbon projectile was launched at a speed of 73 m/s using double‐state‐type LAC.
Gas discrimination method for detecting transformer faults by neural network
Authors: Nogami Takeki , Yokoi Yoshihide , Ichiba Hideo , Atsumi Yoshihiro 
Published: July 2007

AbstractThis paper describes a method available for early detection of abnormality in an oil‐filled transformer. In this method, four gas sensors having different characteristics and neural network are used to identify gas species (H2, CH4, C2H4, C2H2 and mixture of two species). To improve the selectivity of gas sensors, the time response patterns induced by changing sensor temperature and the stationary sensor output are identified by neural network. Furthermore, the mixture ratio of gases is derived by using the stationary sensor output in response to the changing sensor temperature.Gas species are well discriminated, and the mixture ratio derived from the sensor output agrees well with the measurement by gas chromatography. Therefore, it is confirmed that our method is applicable to the transformer diagnostic technology.
Three‐phase and zero‐phase current sensors using hall ICs
Authors: Hara Kazuhiro , Kawamorita Satoshi 
Published: July 2007

AbstractThree‐phase current sensors are required in power‐line distribution systems to monitor currents and protect systems from possible failures. Zero‐phase current sensors also are required to detect leakage currents between power lines and the earth, thus preventing accidents such as a fire.This paper describes new three‐phase and zero‐phase current sensors which are based on a zero method. The sensors consist of Hall ICs, coils, and electronic circuits; no magnetic cores are used. The three‐phase current sensor provides measurements of currents from 0.8 A to 720 A with excellent accuracy, while the zero‐phase current sensor provides measurements from 90 mA to 20 A. The output signal levels are suitable for microprocessor‐based metering and control systems. The sensors are relatively small and lightweight compared to a conventional current transformer (CT). Moreover, they withstand excess currents and do not yield burning or deterioration. They do not require expensive components so they have an advantage in cost compared to an optical‐fiber current transformer.
Fundamental design and electrical characteristics of superconducting commutatorless motor
Authors: Muta Itsuya , Hoshino Tsutomu , Hayashi Kenichiroh 
Published: July 2007

AbstractSince there are no iron cores in the rotor and stator windings of superconducting synchronous motors, some reactances are intrinsically smaller than those of conventional motors. Thus the low synchronous reactance would be expected to improve the torque‐ampere ratio stability and the overload capacity in case of the variable‐speed drive system of a load‐commutated inverter due to the small armature reaction. Moreover, the low subtransient reactance may contribute to lessen the voltage stress during the shortened commutating period, especially in current source‐type inverter (CSI) systems.In this paper, after presenting analytical formulas needed for a machine design, one design algorithm is described, citing one example of an experimental CSI‐fed superconducting motor of 30 kVA which will be fabricated. Further, the distinguished features in its operation, as expected in the foregoing, are verified by the computer simulation study in comparison with a conventional machine in terms of a high specific power density, an extension of stable power limit, and so on.
Expert system for dispatch control in restoration of ehv power system after complete blackout
Authors: Kakimoto Naoto , Lin Bunpin , Sugihara Hiroaki 
Published: July 2007

AbstractPresent‐day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely.This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start‐up, parallel, follow‐up, stand‐by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.
Application of genetic algorithms to service restoration in distribution systems
Authors: Fukuyama Yoshikazu , Ueki Yoshiteru 
Published: July 2007

AbstractService restoration in distribution systems can be formulated as a combinatorial optimization problem to determine power sources for each load considering radial network constraints and power source limits. Until now, the problem has been considered using conventional methods, e.g., the branch‐and‐bounds method, expert system, neural networks, and fuzzy reasoning.Recently, Genetic Algorithms (GA) have been recognized as one of the efficient methods for solving large combinatorial optimization problems. The method can perform parallel search, and can more easily search optimal solutions.This paper presents an application of GA to service restoration in distribution systems. The feasibility of the proposed method is demonstrated on a typical distribution system model. The result shows that the method can solve the problem efficiently, and this tendency becomes dominant by increasing problem dimensions.
Loop power system control by high‐speed phase shifter
Authors: Fujita Hideki , Kurebayashi Hisayuki , Nohara Haruo , Goto Masuo , Kito Yukio 
Published: July 2007

AbstractRecently, power systems have become larger and more complex. Particularly, the looping of power systems is becoming highly desirable to improve the stability. The main features of such looped power systems are: (i) comparatively fewer losses; and (ii) improved angle stability as well as voltage stability. However, these systems have demerits, such as, in case of route off fault in a loop power system, power disturbances increase more and more, etc. If these demerits are overcome, the loop power systems are going to be more beneficial. In an attempt to obtain a solution to such problems, this paper describes several results of applying a high‐speed phase shifter in the control system of a loop power system.
Technology for highly dependable large capacity uninterruptible power supply system
Authors: Matsuzaki Kaoru 
Published: July 2007

AbstractPowerful information networks comprising computers and communication equipment are a modern fact of life. Our dependence upon them requires that they function with no problems. System safety is crucial. Uninterruptible power supply (UPS) systems are commonly equipped to supply stable power regarding critical loads, e.g., large computer centers, telephone and telecommunication centers, aviation control systems, etc. Several types of UPS systems are now used in many of these important fields. However, there has been to date little numerical evaluation vis‐a‐vis system reliability.This paper evaluates mean time between failures (MTBF) of parallel redundant UPS systems, and reports that the MTBF of two sets of parallel redundant UPS systems is lower than that of 3 sets of parallel redundant UPS systems under some circumstances. Continuous power supply reliability of the UPS system with bypass and uninterruptible transfer switch is much higher than is the case for other UPS systems lacking bypass circuit and uninterruptible transfer switch. Highly reliable parallel operation technology is also shown.
A suitable single‐phase pulse width modulation current source inverter for utility interactive photovoltaic generation system
Authors: Nonaka Sakutaro 
Published: July 2007

AbstractA suitable single‐phase inverter for the utility interactive photovoltaic generation system is proposed. The single‐phase Pulse Width Modulation (PWM) current source inverter has a novel circuit configuration in which an auxiliary branch is added to the normal single‐phase bridge circuit. To reduce the size and weight of the dc reactor, a double frequency parallel resonance circuit (LC tank circuit) is inserted in the dc side of the inverter. As a result, the double frequency voltage appearing in the dc side of the inverter due to the pulsation of the single‐phase instantaneous power is perfectly suppressed by the tank circuit. The constant dc current without pulsation is supplied from PV array to the inverter. The inverter provides a sinusoidal ac current for domestic loads and the utility line with unity power factor.The virtual maximum power of the PV array can be obtained without any feedback control. In the system, the PV array can play an important role as a current‐limiter due to itsV‐Icharacteristics. Computed waveforms by simulation are shown. Excellent inverter equipment will be realized that is smaller in size and lighter in weight than is usual for a conventional inverter.