S. Ogasawara

Hokkaido University, Sapporo, Hokkaidō, Japan

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Publications (79)48.17 Total impact

  • Kotaro Tagami, Satoshi Ogasawara
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    ABSTRACT: Advances in power semiconductor devices have contributed to the realization of high‐performance power converters and high‐precision motor positioning. However, high‐speed switching of power devices leads to a high‐frequency leakage current and/or electromagnetic interference (EMI). On the other hand, it has been considered that the leakage current has no relation to motor position control in servo drive systems. This paper analyzes the influence of high‐frequency leakage current on motor positioning and describes its mechanism. Experimental and simulation results show that high‐frequency leakage current may cause variations in the motor position with a frequency that is twice the line frequency. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 33–43, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22479
    Electrical Engineering in Japan 01/2013; 185(4). · 0.10 Impact Factor
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    ABSTRACT: Authors has proposed a new method to decrease high-frequency noise at specific frequency band with modification of switching transient slope. In this paper, new voltage feedback type VDS controller (gate driver) has proposed to realize modified switching transient to increase stability. In the step-down converter applied propose VDS controller, harmonics reduction effect is obtained about 10 dB in AM radio band. Then, output voltage and switching loss characteristics was measured on the step-down converter applied proposed method. It is verified that these characteristics are same to conventional converter. In addition, the proposed method was applied to H-bridge step-down converter for DC motor drive application. It is verified that MT-PWM is able to realize in H-bridge step-down converter without any major modification through simulations.
    Renewable Energy Research and Applications (ICRERA), 2012 International Conference on; 01/2012
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    ABSTRACT: Recently, high performance power switching device realize high performance power converter. However, high speed turn-on and turn-off cause electromagnetic interference (EMI). EMI filters or wire shields decrease EMI. However, they take over space of automotive, and cost is expense. Authors have proposed a new method to decrease high-frequency noise at specific frequency band with modification of switching transient slope. In order to realize a step-down converter with modified switching slope, there are several problems such as generating PWM signal with modified slope, feasibility in a real chopper circuit, switching loss and so on. In this paper, a step-down converter applied proposed modified switching slope was successfully realized using MT (Modified Transient)-PWM generator. The operational characteristics were analyzed for resistive load.
    01/2011;
  • Kotaro Tagami, Satoshi Ogasawara
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    ABSTRACT: Progress of power semiconductor devices has contributed to realizing high-performance power converters and precise servo drives. However, high-speed switching of the power devices may cause high-frequency leakage current and/or electromagnetic interference (EMI). On the other hand, it has been considered that the leakage current has no relation to motor position control in servo drive systems. This paper analyzes an influence of the high-frequency leakage current to motor positioning and describes its mechanism. Some experimental and simulated results show that the high- frequency leakage current may cause motor position variation at twice of line frequency. I. INTRODUCTION In recent years, power semiconductor devices such as insulated gate bipolar transistors (IGBTs) and power metal- oxide-semiconductor field-effect transistors (MOSFETs) are widely used in various fields. Replacement of conventional hydraulic systems with motor drive system is rapidly spread in the automotive field. In industrial field, these power devices have made factory automation equipment high speed and high precision. The widespread use of these devices and systems has resulted in the reduction of CO2 emission, thereby contributing to global environmental protection.
    IEEJ Transactions on Industry Applications 01/2011; 132(7).
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    ABSTRACT: Recently, high performance power switching devices realize high performance power converters. High speed turn-on and turn-off switching causes Electro Magnetic Interference (EMI). EMI filters or shieldings will reduce EMI, however, they usually increase the cost and size of power modules. Authors proposed a new method to reduce high-frequency noise at specific frequency bands with modification of switching transient slopes. In this paper, the characteristics of power converter applying the proposed switching transient will be analyzed from the viewpoint of output voltage, controllability.
    Power Electronics Conference (IPEC), 2010 International; 07/2010
  • Hirohito Funato, Tomoyuki Sakurai, Satoshi Ogasawara
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    ABSTRACT: Recently, global warming has become a major problem. Therefore, the development of technologies for generating clean energy without producing CO2 is required. Micro-hydroelectric power generation is one of the promising options as it requires small simple facilities, and a stable output. The authors have proposed a new system for generating micro-hydroelectric power. The proposed system has a simple mechanism and high efficiency. The proposed system was tested in a real river; however, it was very difficult to study all the characteristics of the system, including those of the hydraulic turbine, because it was very difficult to vary the water flow in a real river. In this paper, the authors propose a new test facility for micro-hydroelectric generation systems. In this system, water flow is generated using a general-purpose pump that can be used to increase pressure of the water flow in order to simulate a head. The fundamental characteristics of the proposed system are determined using the proposed facility and a water head between 1m and 10m and water flow of up to 500L/s. The study of the test facility is very useful in developing high-efficiency micro-hydroelectric generation system.
    IEEJ Transactions on Industry Applications 01/2010; 130(12):1283-1289.
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    ABSTRACT: Recently, harmonic current flowing into power system is increasing due to power electronics equipments. In addition, harmonic voltage is also increasing according to the increase of harmonic current. Harmonic current and voltage may cause increase of loss in receiving power transformers. However, systematic analysis of the loss of receiving power transformers has not been studied. The authors has been tried to analyze the relationship between loss in receiving transformers and harmonics. A 20kVA power system simulator was developed in order to achieve this study. There are however several problems to be solved to get enough date to establish the equation between loss and harmonics. In this paper, experimental results of loss of receiving transformer after some improvements will be reported. The obtained data is accurate enough to analyze loss caused by harmonics. In addition, the reduction effect of the losses using a power-factor improving capacitor at low-voltage side will be discussed through theoretical analysis and experiments.
    01/2010;
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    ABSTRACT: Recently, high performance power switching device realize high performance power converter. However, high speed turn-on and turn-off cause Electro Magnetic Interference (EMI). EMI filters or wire shields decrease EMI. However, they take over space of automotive, and cost is expense. Authors proposed a new method to decrease high-frequency noise at specific frequency band with modification of switching transient slope. In this paper, the improvement of transient wave calculation is described to obtain more effective waveform. In addition experimental verifications are done to show the feasibility of the proposed method.
    Electrical Machines and Systems, 2009. ICEMS 2009. International Conference on; 12/2009
  • T. Sakurai, H. Funato, S. Ogasawara
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    ABSTRACT: This paper proposes a test facility for micro hydraulic generation system. Micro hydraulic generation system is very difficult to exam their characteristics including hydraulic turbine because water flow in various conditions is necessary but it is very difficult to realize in laboratory. In this paper water flow is realized using general purpose pump that can add pressure to water flow to simulate water drop. Fundamental characteristics can be obtained using the proposed facility toward high efficiency micro hydraulic generation system.
    11/2009;
  • S. Ogasawara, T. Igarashi, H. Funato, M. Hara
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    ABSTRACT: Recently, high performance power switching devices realize high performance power converters. High speed turn-on and turn-off however cause electromagnetic interference (EMI). EMI filters composed of inductors and capacitors are widely used to reduce EMI. Inductor is heavy and large so that it is better to reduce use of passive filters. There are several studies to reduce harmonics by modifying switching transient slope. In this paper, a new method of modifying switching transient slope is proposed using optimization of performance index derived from amplitude of harmonics.
    Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
  • Jo Kamada, Hirohito Funato, Satoshi Ogasawara
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    ABSTRACT: High efficiency and low noise in output voltage and current are required in audio-video equipment, medical apparatus, and many other applications. This paper proposes a power amplifier in which a PWM inverter is used as the main circuit. In the proposed power amplifier, a hybrid filter consisting of a simple conventional type LC filter and a small-capacity linear amplifier is connected to the inverter output. The linear amplifier is inserted in series to the filter capacitor to improve the filtering effect of the LC filter. Switching ripples and LC resonances are considerably suppressed by controlling the amplifier using the proposed method, thus implementing a low-distortion switching power amplifier. The effects of the proposal circuit are verified by simulation and experiments. As a result, the proposed circuit achieves low noise about THD=0.68% in simulation and THD=1.5% in experiment. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 91(10): 1–10, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10161
    Electronics and Communications in Japan 10/2008; 91(10):1-10. · 0.18 Impact Factor
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    ABSTRACT: The current paper is dedicated to present browser-based multimedia-rich software tools and e-learning curriculum to support the design and modeling process of power electronics circuits and to explain sometimes rather sophisticated phenomena. Two projects will be discussed. The so-called Inetele project is financed by the Leonardo da Vinci program of the European Union (EU). It is a collaborative project between numerous EU universities and institutes to develop state-of-the art curriculum in Electrical Engineering. Another cooperative project with participation of Japanese, European and Australian institutes focuses especially on developing e-learning curriculum, interactive design and modeling tools, furthermore on development of a virtual laboratory. Snapshots from these two projects will be presented.
    IEEJ Transactions on Industry Applications 01/2008;
  • Source
    Y. Yamamoto, H. Funato, S. Ogasawara
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    ABSTRACT: This paper proposes a method of improving the stability in sensor-less control of permanent magnet synchronous motors. The control method for low-speed region is divided into two: One is a high frequency method, which involves a problem of reverse rotation once misdetection of the permanent magnet polarity should occur, and another one is a current drive method, which has a problem that phase and speed oscillations are caused by quick speed changes. Hence, authors propose adoption of the current drive method for the basic control system with added compensation of stabilization by means of the high frequency method. This combination secures stable control with no risk of reversal and less vibration. In addition, authors have also considered a frequency separation filter of a shorter delay time so that current control performance will not lower even when high frequencies are introduced. This filter has achieved simplified compensation using repetitive characteristic through the utilization of the periodicity of high frequency current. Simulation and experiment have been conducted to verify that the stable performance of this system is improved.
    Power Electronics, 2007. ICPE '07. 7th Internatonal Conference on; 11/2007
  • Y. Nakamura, H. Funato, S. Ogasawara
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    ABSTRACT: The objective of this paper is analysis of output voltage distortion of a PWM inverter with LC filter caused by device voltage drop. The goal of this study is to find out how to compensate the output voltage distortion of PWM inverter caused by device voltage drop to realize precise output voltage. The output voltage distortion is mainly caused by dead time and device voltage drop. There are a lot of studies about distortion is mainly caused by dead time[2]. There are, however, only few studies about device voltage drop, especially considering LC filter effect. In this paper, the authors theoretically derived the output voltage distortion of PWM inverter with LC filter caused by device voltage drop in order to estimate the distortion caused by drop in advance. The distortion was analyzed from the view point of frequency analysis and Total Harmonic Distortion(THD). These results may allow appropriate design of PWM inverter with output voltage compensation. Theoretical analysis was verified through simulations and experiments. In addition, a simple method for compensation of device voltage drop proposed. The proposed method was verified through simulation.
    Power Electronics and Applications, 2007 European Conference on; 10/2007
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The current paper is dedicated to present browser-based multimedia-rich software tools and e-learning curriculum to support the design and modeling process of power electronics circuits and to explain sometimes rather sophisticated phenomena. Two projects will be discussed. The so-called Inetele project is financed by the Leonardo da Vinci program of the European Union(EU). It is a collaborative project between numerous EU universities and institutes to develop state-of-the art curriculum in electrical engineering. Another cooperative project with participation of Japanese, European and Australian institutes focuses especially on developing e-learning curriculum, interactive design and modeling tools, furthermore on development of a virtual laboratory. Snapshots from these two projects will be presented.
    Power Conversion Conference - Nagoya, 2007. PCC '07; 05/2007
  • M. Hirasawa, S. Ogasawara, H. Funato
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    ABSTRACT: This paper proposes a discretization method for real-time simulators. Real-time simulation introducing forward Euler method include the following problems. One is simulation error caused by time step limitation, and another is delay in simulated waveforms. The proposed discretization is characterized by the sophisticated modification to the original simulation model so that the response of a real-time digital system coincides with that of a simulating analog system. The proposed discretization is applicable not only to first- and second-order systems, but also to arbitrary higher order linear systems. Finally, the real-time simulation of a third-order system demonstrates appropriateness and effectiveness of the proposed discretization.
    Power Conversion Conference - Nagoya, 2007. PCC '07; 05/2007
  • Y. Nakamura, H. Funato, S. Ogasawara
    [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this paper is analysis of output voltage distortion of a PWM inverter with LC filter caused by device voltage drop. The goal of this study is to find out how to compensate the output voltage distortion of PWM inverter caused by device voltage drop to realize precise output voltage. The output voltage distortion is mainly caused by dead time and device voltage drop. There are a lot of studies about distortion is mainly caused by dead time. There are, however, only few studies about device voltage drop. especially considering LC filter effect. In this paper, the authors theoretically derived the output voltage distortion of PWM inverter with LC filter caused by device voltage drop in order to estimate the distortion caused by drop in advance. The distortion was analyzed from the view point of frequency analysis and total harmonic distortion (THD). These results may allow appropriate design of PWM inverter with output voltage compensation. Theoretical analysis was verified through simulations and experiments.
    Power Conversion Conference - Nagoya, 2007. PCC '07; 05/2007
  • Electrical Engineering in Japan 03/2007; 110(4):83 - 91. · 0.10 Impact Factor
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    ABSTRACT: In general, diode rectifiers with electrolytic capacitors on the dc side have been used as dc power supplies for voltage source inverters. This type of rectifiers, however, causes many problems such as poor power factor and harmonics. Recently, voltage source PWM rectifier-inverters have been studied to provide the following advantages; (1) harmonic-free on both ac sides; (2) unity power factor on the input ac side; (3) power flow of either direction or power regeneration; (4) reduction of the dc capacitor. It is, however, difficult for a conventional one to regulate the capacitor voltage on transient states because of having only a voltage feed-back loop.This paper describes a voltage source PWM rectifier-inverter with feed-forward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feed-forward control of instantaneous power makes a great contribution to sufficiently suppress voltage fluctuation of the dc capacitor on transient states. Transient characteristics are discussed and some interesting experimental results of a laboratory model are shown.
    Electrical Engineering in Japan 03/2007; 112(5):133 - 142. · 0.10 Impact Factor
  • Hirofumi Akagi, Satoshi Ogasawara, Akira Nabae
    Electrical Engineering in Japan 03/2007; 103(4):49 - 57. · 0.10 Impact Factor

Publication Stats

2k Citations
48.17 Total Impact Points

Institutions

  • 2009–2011
    • Hokkaido University
      • Division of Laboratory Science and Technology
      Sapporo, Hokkaidō, Japan
  • 2004–2010
    • Utsunomiya University
      • Division of Electrical and Electronic Engineering
      Totigi, Tochigi, Japan
  • 1986–2007
    • Nagaoka University of Technology
      • • Department of Electrical Engineering
      • • Faculty of Engineering
      Нагаока, Niigata, Japan
  • 1993–2004
    • Okayama University
      Okayama, Okayama, Japan
    • Seiko Epson
      Kamisuwa, Nagano, Japan
  • 2002–2003
    • Tokyo Institute of Technology
      • Electrical and Electronic Engineering Department
      Tokyo, Tokyo-to, Japan