Eisuke Masada

A novel combined lift and propulsion system for a steel plate conveyance by electromagnets

A novel lift and propulsion system using alternating-current electromagnets is proposed. The proposed system can simplify the configuration of a non-contacting conveyance system for a steel plate by magnetic force. Both finite element analysis and experiments were carried out. After investigating the basic characteristics of the proposed electromagnetic linear actuator, magnetic levitation experiments with four controlled electromagnets were performed and stable levitation was realized though about 65% of the total mass of the steel plate was supported by uncontrolled alternating-current electromagnets. The results indicate that the proposed system can produce not only the strong levitation force but also the propulsion force on a steel plate.

Effective application of superconducting magnetic energy storage (SMES) to load leveling for high speed transportation system

The consecutive pulse power demand of the high speed transportation systems like Shinkansen, gives deteriorative influences to the power supply system and increases its operational costs. To cope with this problem, it has been studied to install the superconducting magnetic energy storage system (SMES) in railway substations. However, the scale of installation becomes too large because of low space factor of SMES, and hampers its realization. Then, it is considered to use SMES only for suppression of the high frequency component of load fluctuation, and to combine with a large capacity battery storage (BEMS), which can not follow fast fluctuation and covers its low frequency component. A novel control scheme of this combined energy storage system is proposed. The fluctuation of power demand caused by high speed train operations in a railway substation is measured separately in the frequency range and used to regulate both SMES and BEMS to suppress fluctuation. With simulation studies based on the load model of high speed train operation at a certain substation, this hybrid approach and its control scheme are verified effective. The system configuration is compact enough to be installed at a substation.

A combined lift and propulsion system of a steel plate by transverse flux linear induction motors

To realize a non-contacting conveyance of a steel plate, a combined lift and propulsion system of a steel plate by transverse flux linear induction motors (LIMs) is proposed. By introducing the DC biased AC feeding to the LIM, a steel plate is supported stably and efficiently. In this paper, after showing the advantages of the system, the magnetic levitation experiments are carried out to investigate the feasibility of the system.

Avoiding chaotic processes in current control of AC drive

The main objective of the paper is to highlight the strange and complex behaviour of a motor drive consisting of a three-phase induction machine fed by a voltage source inverter (VSI) and controlled by a hysteresis current controller (HCC). This system exhibits either periodic, subharmonic or chaotic trajectory movements, and shows bifurcation phenomena. The paper presents simulation results to introduce some astonishing properties, and applies two techniques in reaching them: continuous trajectory; and trajectory with discrete time steps. The first approach is theoretically significant while the second one represents the model of practical hardware implementation. Maps showing the chaotic and periodic regions are presented. After convincing maps regarding the chaotic nature of the system the influence of such important variables as the load torque or the speed command and parameters as the stator resistance and transient inductance is investigated. It could help either in stabilizing the periodic motions or inducing chaos. It can be concluded that periodic process cannot be maintained in wide range of change in system variables without additional measures.

A single-phase PCS with a novel constantly sampled current-regulated PWM scheme

The error-tracking mode (ETM) is a novel constantly sampled pulsewidth modulation (PWM) scheme for a voltage-source power conversion system (PCS) interconnecting with a utility network to regulate its AC current waveform. It guarantees, theoretically, the AC actual current to be settled within an arbitrary target allowable error. Generated current harmonics can be restricted by a relatively small filter. Both the minimum on- and off-duration times of switching commands are assured by the PWM scheme itself. A four-quadrant 1-kVA PCS in which gate commands are produced by the novel PWM scheme has been successfully experimented upon for the first time, and it has justified the ETM-PWM theory. This paper describes the design procedure and experimental results of the trial setup.

Characteristics of an electromagnetic levitation system using a bulk superconductor

It is beneficial to apply a high-Tc bulk superconductor as a large flux source to an electromagnetic levitation system, which needs large amounts of levitation force. We made an attractive-type electromagnetic levitation system using a hybrid magnet that mainly consisted of bulk superconductor and control coils to confirm the principle of the levitation, and obtained characteristics of its system by both experiment and numerical analysis with magnetic circuit calculation.

Magnetic gradient levitation using high-Tc bulk superconductors

Magnetic gradient levitation systems using high-T/sub c/ bulk superconductors and iron rails have been studied by numerical analysis of their electromagnetic field. This system enables stable levitation, even at standstill, without active control, by the flux pinning of the superconductors. Emphasis is put on the analysis of the dependence of the levitation characteristics on the critical current density in the superconductor. Numerical analysis results show that levitation characteristics are strongly dependent on the critical current density. Bulk superconductors with a critical current density higher than 2/spl times/10/sup 8/ A/m/sup 2/ are required for stable levitation and sufficient force can be generated in the case of the system model considered in this paper.

Combined power supply method for micro grid by use of several types of distributed power generation systems

A power control method to compensate power fluctuation of the load in the microgrid systems is proposed and discussed. Active power responses of several kinds of distributed power generation systems (DGs) such as gas engine, micro gas turbine, etc., energy storage system, and load fluctuation of a site have been measured. Based on the measurements, combination control method for several kinds of DGs and an energy storage system has been made and experiments have been carried out by use of small scale micro grid model system. It is shown that the load fluctuation has been compensated by the proposed method

Magnetic levitation of a flexible steel plate with a vibration suppressing magnet

A magnetic levitation system that has a vibration suppressing electromagnet which use only the velocity of the levitated object for the control has been studied. The proposed system has advantages of the stable levitation of a flexible steel plate which moves with time under the fixed electromagnets. The simulation of levitated plates response using finite element method and the magnetic levitation experiments using such a vibration suppressing magnet were carried out. The results show the vibration suppressing magnet is able to control the low frequency natural vibration effectively, and a notch filter is able to avoid the excitation of the high frequency natural vibration.

Application of unified power flow controller for improvement of power quality

The control scheme and characteristics of the unified power flow controller (UPFC) installed at the substation connecting the transmission system with the distribution network, are studied in relation with the power quality improvements for the loads. A simplified model of UPFC with network is introduced on the basis of the instantaneous power and reactive power function to design the control system and evaluate the effect to improve power quality in the load system. The effectiveness of UPFC is concluded for the power quality control in the substation connected to the distribution network both for the voltage dip and harmonics distortion. It would function with the same principle to suppress the interaction between the distant high power supply and the distributed small power generator in the load network.