Akihiro Ametani

Bio: Akihiro Ametani is an academic researcher from École Polytechnique de Montréal. The author has contributed to research in topics: Emtp & Transient (oscillation). The author has an hindex of 29, co-authored 293 publications receiving 3686 citations. Previous affiliations of Akihiro Ametani include Doshisha University.

A General Formulation of Impedance and Admittance of Cables

Abstract: Interest in the analysis of wave propagation characteristics and transients associated with cable systems has rapidly increased. In order to answer the need of the analyst, impedances and admittances of various cables have to be known. This paper describes a general formulation of impedances and admittances of single-core coaxial and pipe-type cables. The formulation presented here can handle a coaxial cable consisting of a core, sheath and armor, a pipe-type cable of which the pipe thickness is finite and an overhead cable, which has not been discussed in the literature heretofore.

A method of a lightning surge analysis recommended in Japan using EMTP

Abstract: EMTP has been widely used in Japan to analyze switching and lightning overvoltages to design power stations and substations from the viewpoint of insulation coordination. The Japanese standard of high voltage testing, JEC-0102-1994, and the insulation design and the coordination of an 1100-kV line of Tokyo Electric Power Company were mostly based on EMTP simulations. This paper presents a method of a lightning surge analysis using the EMTP recommended in the Japanese standard and related guidelines, and suggests further work to be done based on discussions of applicable limits and problems of the recommended models.

Phase domain modeling of frequency-dependent transmission lines by means of an ARMA model

Abstract: This paper presents a method for time-domain transient calculation in which frequency-dependent transmission lines and cables are modeled in the phase domain rather than in the modal domain. This avoids convolution due to the modal transformation, and possible numerical instability due to mode crossing. In the new approach, time domain convolutions are replaced by an ARMA (auto-regressive moving average) model that minimizes computation and is EMTP-compatible. A fast and stable method to produce the ARMA model is developed, and results are shown to agree well with both rigorous frequency-domain simulations and also field tests.

Experimental evaluation of a UHV tower model for lightning surge analysis

Abstract: An experimental investigation was performed on a UHV tower model for the EMTP multiconductor calculation of lightning overvoltage at substations associated with back-flashover at an adjacent transmission tower. The various lightning surge response characteristics were measured on an actual UHV tower, and parameters of a multistory transmission tower model that can reproduce voltages across the insulator strings, voltages of the crossarms, and voltages of the power lines were determined. A value of 120 /spl Omega/ was determined as the surge impedance at each section of the multistory tower model, which closely agreed with the tower surge impedance measured for the UHV tower alone. >

Modeling of thin wires in a lossy medium for FDTD simulations

Abstract: An equivalent radius of a thin wire in a lossy medium, represented by the finite-difference time-domain method, is derived using the concept that was proposed to derive an equivalent radius of a thin wire in air. Then, a simple technique to specify an arbitrary radius of a thin wire in a lossy medium is proposed. The proposed technique does not employ locally fine or nonuniform subgrids, but is based on an orthogonal and uniform-spacing Cartesian grid. The validity of the proposed technique is investigated in a transient state, as well as in a quasisteady state, and shown to be satisfactory.

A review of active filters for power quality improvement

Abstract: Active filtering of electric power has now become a mature technology for harmonic and reactive power compensation in two-wire (single phase), three-wire (three phase without neutral), and four-wire (three phase with neutral) AC power networks with nonlinear loads. This paper presents a comprehensive review of active filter (AF) configurations, control strategies, selection of components, other related economic and technical considerations, and their selection for specific applications. It is aimed at providing a broad perspective on the status of AF technology to researchers and application engineers dealing with power quality issues. A list of more than 200 research publications on the subject is also appended for a quick reference.

New trends in active filters for power conditioning

Abstract: Attention has been paid to active filters for power conditioning which provide the following multifunctions: reactive power compensation; harmonic compensation; flicker/imbalance compensation; and voltage regulation. Active filters in a range of 50 kVA-60 MVA have been practically installed in Japan. In the near future, the term "active filters" will have a much wider meaning than it did in the 1970s. For instance, active filters intended for harmonic solutions are expanding their functions from harmonic compensation of nonlinear loads into harmonic isolation between utilities and consumers, and harmonic damping throughout power distribution systems. This paper presents the present status of active filters based on state-of-the-art power electronics technology, and their future prospects and directions toward the 21st Century, including the personal views and expectations of the author.

Active Harmonic Filters

Abstract: Unlike traditional passive harmonic filters, modern active harmonic filters have the following multiple functions: harmonic filtering, damping,isolation and termination, reactive-power control for power factor correction and voltage regulation, load balancing, voltage-flicker reduction, and/or their combinations. Significant cost reductions in both power semiconductor devices and signal processing devices have inspired manufactures to put active filters on the market. This paper deals with general pure active filters for power conditioning, and specific hybrid active filters for harmonic filtering of three-phase diode rectifiers.

Accuarte Modelling of Frequency-Dependent Transmission Lines in Electromagnetic Transient Simulations

Abstract: The parameters of transmission lines with ground return are highly dependent on the frequency. Accurate modelling of this frequency dependence over the entire frequency range of the signals is of essential importance for the correct simulation of electromagnetic transient conditions. Closed mathematical solutions of the frequency-dependent line equations in the time domain are very difficult. Numerical approximation techniques are thus required for practical solutions. The oscillatory nature of the problem, however, makes ordinary numerical techniques very susceptible to instability and to accuracy errors. The, methods presented in this paper are aimed to overcome these numerical difficulties.

Control Strategy of Active Power Filters Using Multiple Voltage-Source PWM Converters

Abstract: The control strategy of active power filters using switching devices is proposed on the basis of the instantaneous reactive power theory. This aims at excellent compensation characteristics in transient states as well as steady states. The active power filter is developed, of which the power circuit consists of quadruple voltage-source PWM converters. As the result, interesting compensation characteristics were verified experimentally which could not be obtained by the active power filter based on the conventional reactive power theory.