The most distinct advantage of electric vehicle (EV) is in its quick and precise torque generation. This remarkable feature gives EV a high performance vehicle dynamics control, which is absolutely impossible for internal combustion engine vehicle (ICV). To this aim, we made two electric vehicles: UOT Electric March I and II. In this paper, I would like to show you the attractiveness of EV and invite you all to this exciting field.

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This article describes the recent progress and prospect in the high-brightness light-emitting diodes (LEDs) and its applications to lighting technologies. Basically, there exist three methods which can generate white light using LED and phosphor material combination. The white LED lighting array devices consisting of blue LED and YAG: Ce³⁺ yellow phosphor have already been applied to the energy-saving type luminaire for street light and sign panel.

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The power generating systems of variable speed and constant frequency using rotor excitation of the wound-rotor induction machines have been used for such applications as variable speed pump generators and flywheel energy storage systems. However, the stand-alone generating system of this type, has only been reported and has not yet been practically used.
On the other hand, the stand-alone generating systems using diesel engines have been widely used for emergency supplies of plants or isolated islands and so on. However, in these cases, the synchronous generators are usually used. If the output frequency is to be kept constant, there is the need to control the speed of the engine using a high performance governor. Even then, the output frequency changes in case of a sudden load change.
This paper proposes a new stand-alone power generating system. In this system, the constant frequency output voltage can be obtained even though rotor speed changes by several percent.

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We have developed a new power conditioner of solar energy system for residences. We have named it “the multi-dc input power conditioner” which equips dual input of photovoltaic arrays. One input called “standard input” connects to arrays which generate higher voltage than the other arrays, and another input called “multi-input” connects to arrays which generate lower voltage. The output voltage of arrays on the “multi-input” side is boosted up to the output voltage of arrays on the “standard input” side by the built-in boost converter. That circuitry enables to control MPPT for each array independently. Consequently, this new power conditionercan improve the efficiency of the system in the case of irregular configuration of photovoltaic modules on the roof.

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This paper proposes a novel PWM method of a single phase bridge inverter, which decreases the temperature rise of the power semiconductor devices and improves utilization factor of devices. In case of conventional modulation methods, there is a temperature difference between the power devices of the four arms. This comes from unequal conducting and switching losses of the devices.
Our proposed method eliminates the temperature difference by interchanging the lead and lag arms of the inverter every few cycles. The features of the proposed PWM method have been studied by MATLAB simulation, In addition, the usefulness of the new modulation method has been verified by the experiments.

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In recent years, various measures to cope with global environment problems have been strongly focused. And it has been said that energy saving of electric-use apparatus would be one of the potential solutions. On the other hand, a low-speed elevator with a diode rectifier input consumes the regenerated power from the electric motor as heat with resistors, which results in the remarkable energy loss in the whole elevator system.
This paper proposes an energy-saving elevator which can store the regenerated energy and discharge the stored energy at the power running of the machine. Therefore, a very high efficient elevator system can be achieved. Furthermore, this paper also focuses on three types technical possibilities of the elevator systems: a load-leveling type, an accumulation type, and an energy-saving type. Those technical possibilities were successfully verified with prototypes. Especially with the energy-saving type which utilized nickel hydoride batteries, 31% of the energy saving was attained.

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In power stations and substations of electric power companies, power semiconductor devices such as diodes and thyristors have been used in control power supplies and emergency power supplies since the 1970s. Such equipments designed on the assumption that power semiconductor devices arc semi-pemmancnt, since their service life is much longer than those of capacitors and resistors. Therefore, it is hard to find studies that systematically examine the long-term reliability of semiconductor devices. However it is, such studies arc very important from the viewpoint of assuring reliability and of improving the renewal period by proper equipment maintenance. This paper presents the long-term reliability of power semiconductor devices used in power station exciters and substation rectifiers.

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Multilevel converter is suited for high power application, since it is able to reduce harmonics and switching loss at the same time. We propose multilevel converter configuration to suppress harmonic, without increasing switching loss. In this paper, suppressing ability of higher harmonics of 9lovol 9level-3pulse and 11level converter is described. 9level-3pulse converter is preferable than 11level converter in good reduction of harmonics.

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Energy storage devices with high energy density as well as high power density are expected to be developed from the point of view of compensation of fluctuating load and generated power by wind turbines and photo voltaic generation. SMES (Superconducting Magnetic Energy Storage) has higher power density than other energy storage methods, and secondary batteries have higher energy density than SMES. The hybrid energy storage method using SMES and secondary batteries is proposed, and the computation method of power reference value for each device and the simulation method is presented in this paper. Experimental results are also presented.

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Recently, many power electronic equipments are successfully employed in various field for their high efficiency operation, saving energy, etc. However, these produce some harmonic current, which flow into electric power system. As a result, it is clear that these harmonic current makes the quality of electric power inferior. Then it is important to estimate of harmonic source of power system. Then we propose a new approach to utilize active filter, installed in it on purpose to suppress the harmonic current. Our proposed methods are able to estimate harmonic source of power system by manipulating the active filter and analyzing the operating data. The usefulness of the proposed approach is confirmed by experiments.

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Authors previously proposed a new simple maximum power point tracking (MPPT) control scheme for a PV system connected in parallel with the ac system line without using conventional “mountain climbing” optimum operating point searching technique. Although no information is needed on PV array, the generated output power is maximized by utilizing limit cycle phenomena occurring on equilibrium/non-equilibrium boundary of system power flow. This paper shows a parameter design procedure to determine operating period based on a theoretical model is presented. It has turned out that the operating period of limit cycle is kept constant depending on the circuit and control parameters irrespective of the insolation conditions of PV array.

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For rectifier circuits with power factor correction, boost converters are generally used, and as a result the output voltage becomes limited To expand the controlled voltage range, buck-boost or Cuk converter types should be utilized This paper presents a circuit configuration with power factor correction by a third type of buck boost converter. termed a ‘canonical switching cell’.
Single phase power factor correction using a buck boost converter can control the output voltage over a wide range, because it has the ability to step-up and step-down the output voltage. Firstly, this paper compares the mechanisms of the power transmission and the characteristics based on the switching ripple of various converters, in which the recently reported Luo converter is added in discussion.
Secondly, the canonical switching cell is applied to the single phase power factor correction. It is proposed that this converter is suitable for power factor correction.

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The linear compressor driven by linear oscillatory actuator (LOA) has the potential to reduce friction losses and achieve better efficiency. We develop the high efficiency Moving Magnet Type LOA having spring characteristics and the two piston-type linear compressor driven by the LOA. This paper presents thrust characteristics and efficiency of the LOA. Moreover, the performance test results of the linear compressor driven by the LOA are presented.

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A new utility interactive inverter for solar power generation was developed with transformer-less high impedance DC link configuration, which can realize compactness and high efficiency. The high impedance DC link structure, which reduces a value of the interstage capacitor to about 1/100, is evaluated for its waveform control of the output current. This paper describes the high impedance DC link typed circuit configuration and its operating principle. A control system delivering high quality output current is proposed. The newly developed utility interactive inverter has the maximum efficiency 95.5% or more and a compact size of 550mm×300mm×124mm.

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Cold-Crucible Furnace (CCF) is an induction-melting furnace, which consist of watercooled copper segments. Because of less contamination than the ceramic crucible, CCF is utilized as melting furnace of high purity metal for target materials. On the other hand, for recycling of Titanium or for reducing the capacity of radioactive waste, a large scale CCF is required. We developed a large scale CCF (600∅) with bottom pouring structure, and experimental work was successfully performed.

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Small scale energy storage system incorporating battery bank has attracted special interest as promising load leveling system. Because battery bank voltage of this system is low, it is important to use two-quadrant chopper suitable for large step-up/step-down ratio. In this paper we propose a circuit topology of two-quadrant chopper appropriate for small scale load leveling system and present the analytical and experimental results.

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This paper introduces a new software tool for teaching and self-learning power electronics consisting of HTML text and Java-applets for interactive animation and simulation of power electronic circuits. This tool requires only a standard web-browser, is independent of the operating system, and no installation is necessary.
This flexible tool can be used for on-line learning, can be easily integrated into an E-Learning platform for distance learning, and can be used in the classroom with note-book computer and over-head projector, via Internet or CD-ROM. This tool presented at the conference is used in courses at the ETH Zurich, Switzerland and Nihon University. The tool can be found at “http/www.ipes.ethz.ch_” in English, German and Japanese.

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This paper proposes an improved 3-level GCT converter for large capacity adjustable speed drives. The main circuit topology of the 3-level converter is also well-known as a neutral-point-clamped convener. Realizing high efficiency, a regenerative voltage clamping circuit is newly applied. And introducing a transient junction temperature analysis of power devices, the maximum output capacity is ensured. These technologies can contribute to improvement of the 3-level GCT converter especially using 6kV/6kA GCTs.

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In the three-phase PWM converter, the source phase currents have been independently controlled. But, in the unsymmetrical three phase voltage system, the source currents are distorted by the independent phase control method. If the extension pq method is applied to the three phase PWM converter, the source current will not be distorted. In this paper, the authors propose the application of the extension pq theory to the PWM converter and clarify the effectiveness by simulation.

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In the usual photovoltaic systems, the PV array cannot be grounded, as the utility grid ac line is grounded. In order to ground the PV-array and not to generate the leakage current due to stray-capacitors to the ground, the single-phase inverter circuit using a pair of chopper circuits was proposed by authors several years ago. In this paper, a novel fly-back type inverter circuit is proposed both to reduce the number of required semiconductor devices by simplifying main circuit and to improve the efficiency. As the proposed circuit can generate no var-power, the power factor of connected loads must be unity, however, it is expected that the novel circuit will be applied not only to photovoltaic systems but also AC sources for high intensity discharge lamp and others.

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