摘要:

AbstractIn order to realize light and small power supplies, this paper proposes a film‐shape transformer called film transformer. The basic operating principle of this transformer is the skin effect similar to those of the coreless transformer previously exploited by the authors. Both the primary and secondary coils composed of thin‐film conductors are arranged coaxially on the one‐layer film base, and the film transformer is constructed by the lamination of these films.In this paper, experimental as well as numerical studies are carried out about basic characteristics of the film transformer in order to examine possibilities in practical use. As a result, it is shown that the film transformer may be applicable to high‐frequency switching power s

ISSN:0424-7760    

DOI:10.1002/eej.4391170401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractUnder the current deregulation of the electric utility industry, power system planning has become more complex. System planners are required to study how to use available resources to meet customer's demand economically with acceptable reliability and quality. Integrated resource planning has emerged recently as one effective approach for this problem, and the approach has been expanded to include the value of reliability, that is, power interruption cost.This paper is aimed at developing a flexible decision method to select a favorable plan among various transmission system expansion alternatives, not only from a power supplier's viewpoint, but also from the customer's perspective, including cost of interruption.Bellman‐Zadeh's maximizing decision using a fuzzy decision set is applied as a flexible decision method which is able to reflect the planner's intentions. Numerical examples are given to ascertain the effectiveness of the proposed metho

ISSN:0424-7760    

DOI:10.1002/eej.4391170402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractApplication of controlled series capacitors with anti‐parallel thyristor combination across the capacitor segment is one of the new and promising countermeasures for enhancement of power system stability. The line reactance can be directly controlled by the controlled series capacitors, hence, it is very effective to apply the capacitors for damping power system disturbances.In this paper, we describe the following.(1) The design method of control system for the segmented series capacitors with thyristor switches is proposed.(2) The effectiveness of the controlled capacitors proposed for power system stabilization is shown with the results of EMTP analysis.(3) The possibility of zero passing missing phenomena of capacitor voltage is indicated by EMTP simulation, and a countermeasure is proposed in order to avoid the phenomena. The effects of the countermeasure is indicated by the results of EMTP simulatio

ISSN:0424-7760    

DOI:10.1002/eej.4391170403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractA stable power supply is required from power systems as the importance of electrical energy increases. Particularly, in the case of high‐voltage systems (500‐, 275‐, 154‐kV bulk power systems), this requirement is high. However, there are cases when power system faults cannot be avoided. Accordingly, it is very important to restore power systems quickly and safely if these failures occur. The characteristics of the power system restoration (its combinatorial aspects, use of knowledge from a wide variety of origins and of different types, number of criteria to satisfy) make it a difficult problem, for which the use of expert systems to generate restoration plans is being considered by many researchers, and promising results have already been obtained. However, most systems are still in the prototype stage [1]. One reason seems to be the lack of studies of a support system for knowledge‐based behavior (unable to describe with any rule).This paper analyzes first power system restoration based on the human performance model [6] and discusses the knowledge‐based behavior that is a high conceptual level of human performance to solve the problem from the combinatorial viewpoint. Then the application for the trunk line dispatching center is reported. Finally, the relations between knowledge‐based behavior and the designed human interfaces are verified with a power networks restorati

ISSN:0424-7760    

DOI:10.1002/eej.4391170404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe authors proposed a nonlinear adaptive generator control system with neutral networks for improving damping of power systems, and showed its effectiveness in a one‐machine infinite bus test power system in a previous paper. The proposed neurocontrol system adaptively generates appropriate supplementary control signals to the conventional controllers such as the automatic voltage regulator and speed governor so as to enhance transient stability and damping of the power system.In this paper, the applicability of the proposed neurocontrol system to multimachine power systems is discussed. Digital time simulations are carried out for a 4‐machine test power system, where one or several synchronous generators is equipped with the neurocontrol system. As a result, also in the multimachine power system, the proposed adaptive neurocontrol systems improve the system damping effectively and they work adaptively against the wide changes of the operating conditions and the network configurat

ISSN:0424-7760    

DOI:10.1002/eej.4391170405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractA new transient stability controller system (TSC) based on on‐line transient stability calculation has been developed. The TSC system prevents the power system from wide‐area blackout by shedding generators optimally when a serious fault occurs. This system consists of a central processing unit (TSC‐P), and four local units for fault detection (TSC‐C), and seventeen units for generator shedding (TSC‐T). The TSC‐P selects optimal generators to be shed for stabilization based on on‐line transient stability calculation for contingencies at 500 kV lines and buses every five minutes. The results are transmitted to the TSC‐Cs periodically. Should any fault occur, only one TSC‐C will detect the fault occurrence and send control signals to the TSC‐Ts which actually generate shedding signals. To realize the TSC system, essential are fast stability evaluation methods for a large number of contingencies and effective selection methods of optimal generators to be shed for stabilization.This paper presents total algorithms applied in the TSC‐P, the results of algorithm verification tests using a prototype system combined with a large‐scale analog simulator, and the characteristi

ISSN:0424-7760    

DOI:10.1002/eej.4391170406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper proposes a method of analyzing the three‐dimensional magnetic field of a system containing coil currents and magnetic substances using virtual currents. Various methods have been presented for analysis of a three‐dimensional static field in an open boundary space; however, in a large‐scale problem, the computational size easily exceeds the acceptable limit of computing time and machine capacity. The basic idea of the proposed method is to divide the whole region into interior and exterior regions with an artificial boundary and to substitute virtual currents for source currents and magnetic substances within the boundary. The use of virtual currents reduces the number of elements to be analyzed and shortens computing time while maintaining accuracy of analysis. In this paper, a method of determining virtual current is proposed and principal parameters of virtual currents that affect accuracy of analysis are examined. The conditions under which the virtual current method can be applied are examined through analysis of errors introduced by the virtual current method. This method has been applied to analyze magnetic shielding of a magnet for magnetic resonance imaging. This example proves that the proposed method is effective in reducing the scale of analysis and computing

ISSN:0424-7760    

DOI:10.1002/eej.4391170407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractSuper‐high‐speed and high‐power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high‐power drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet‐type synchronous motors is proposed. High‐power factor and high efficiency can be expected in permanent magnet‐type bearingless motors. The proposed bearingless motor is a 4‐pole permanent magnet synchronous motor, in which additional 2‐pole windings are wound together with 4‐pole motor windings in stator slots. With currents of 2‐pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface‐mounted permanent magnet bearingless motors are analyzed mathematically. The relationships between radial forces and the permanent magnet thickness were derived. From these relationships, the optimal permanent magnet thickness to produce radial forces efficiently is found. A test machine was built to confirm the relationships of radial forces

ISSN:0424-7760    

DOI:10.1002/eej.4391170408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractRecently, the V/F control drive system of the induction motor has been applied widely to the drive of compressors, pumps, etc., because it is very simple and basically requires no speed sensors. However, if the V/F controlled induction motor drives a pulsating load such as the compressors, the rotational speed of the motors is fluctuated considerably and the motor frame vibrates due to the pulsating load torque. When frequency of the torque pulsation is especially close to the resonant frequency of the mechanical system, large vibration and acoustic noise are produced.In this paper the authors propose a method to reduce the vibration of the V/F controlled induction motor with a fluctuated load by repetitive control using an acceleration sensor. The acceleration sensor is easy to install on the motor or load frame. The repetitive control is considered effective for reduction of the vibration, as the load torque varies periodically. Effectiveness of the proposed method is confirmed by approximate analysis and experiments.

ISSN:0424-7760    

DOI:10.1002/eej.4391170409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY