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In order to measure friction coefficients of tire grounding surfaces in car running, a simple cantilever-type tactile sensor that can detect the vertical load and friction force applied to the sensing part as well as direction of the friction force, simultaneously, has been proposed. The present study equips the proposed sensor to a tire and confirms that the sensor can measure the friction coefficient of the tire grounding surface. For this purpose, measurements in this study were conducted using a sensor under a similar load as that of a common automobile travelling in an arbitrary direction. In order to perform the experiments under a high load in an arbitrary direction, we developed a parallel mechanism-type tire-driving device. The developed device can apply a high load to the tire in an arbitrary direction and can measure the vertical load, friction force, and the direction of the friction force applied to the tire involving the sensor. Thus, the measurement accuracy of the proposed sensor can be verified by comparing the output of the sensor to that of the driving device. As a result of this study, we clarified that the measurement values of the sensor are affected by the deformation of the tire, and proposed a method for correcting the effect of the tire deformation. By introducing the proposed correction method to the measurement of the sensor, it was confirmed that the friction coefficients of various surfaces can be measured with sufficient accuracy under a practical high-load condition.

When a greatly varying load is connected to a weak system, stability of the system becomes a problem. In these days, because the use of renewable energy is accelerating, not only the loads but also the distributed power sources can be critical factors in destabilizing the system. The virtual synchronous generator (VSG) control allows a static inverter to behave similar to a synchronous generator (SG). Using this VSG technology, we can decrease the introduction ratio of SGs with fossil fuels, and thus, we can combine various types of power sources. At the same time, if the combination of governor and rotor inertia is represented in a first-order lag element, the VSG can suppress the frequency fluctuations in microgrids. In this paper, we present a design guideline of a VSG. The simulation results by EMTP-RV confirmed that the parallel-connected VSG can suppress the frequency fluctuation. In addition, the results were almost consistent with the experimental test results.

DC microgrid is suitable for dc output type distributed generations and energy storages. In this paper, dc microgrid for residential houses is described. Electrical power through dc distribution line (± 170 V) can be converted into some proper ac or dc voltages by converters placed near loads. Each house has a cogeneration system such as gas engine or fuel cell. The outputs of those distributed generations are connected to dc distribution line, and the power from generations can be shared among residences. We constructed a small scale experimental system in our laboratory, and examined the fundamental characteristics of dc microgrid. The experimental results demonstrated that high quality power was supplied even when voltage sag occurred in the utility grid.

Several converter/inverter circuit topologies using silicon controlled rectifier (SCR) and gate turn off (GTO) devices have been developed for operating a superconductive magnetic energy storage (SMES) coil with an electric utility. Control of real and reactive power and shorting switch and current bypass techniques have been investigated. Experimental tests of independent real and reactive power control have been successfully performed using an 8-h superconducting coil and 10-kVA power conditioning circuits. In typical studies, the real power was cycled from zero to a peak charging power of 7 kW and then the discharging power was held constant at 3 kW, while the reactive power was independently held constant at various values between 0 and +or-5 kvar. A technique for zero current opening of a mechanical bypass switch using converter control to cancel the coil current in the closed bypass switch was also successfully demonstrated using the 8-h coil.

The on-resistance of a power MOSFET has a minimum value at around 80 K. This characteristic was utilized in order to operate a power converter circuit using power MOSFETs in a cryostat with a superconducting coil. As a result, it was confirmed that power losses of the chopper circuit and the size of the current leads can be greatly reduced. The power loss of the circuit was half of that at room temperature, and the loss can be reduced further by using diodes with lower on-voltages at low temperatures. The size of the current leads was reduced by using the chopper circuit as a DC transformer.

Power supply for the large scale accelerator magnets draws a large amount of power from the utility network. For example, the pulse power amplitude and the dissipation power of J-PARC 50 GeV synchrotron magnet power are estimated to be about 170 MW and 30 MW, respectively. Superconducting magnetic energy storage (SMES) is one of candidates to compensate these large pulse load and line voltage fluctuation. Study on circuit configuration of the power supply with SMES has been continued. Present status of the R&D for the SMES system and the laboratory scale experiment results will be discussed.

In J-PARC 50 GeV synchrotron, peak active power and the dissipation power of main magnets are estimated to be about 135 MW and 37 MW, respectively. Super Conducting Magnetic Energy Storage (SMES) is one of candidates to compensate these large load and line voltage fluctuation. Study on circuit configuration of the power supply with SMES will be discussed. Plan of experiment is also described.

A novel low loss technology of thin film layered electrode and its application to dielectric filter in 2 GHz band is described. We confirmed that the surface resistance of thin film layered electrode is reduced in proportion to the approximately square root of the number of conductor layers, compared to a bulk metal.

The superconductive magnetic energy store (SMES) approach to utility-load leveling has the potential for very high energy conversion efficiency and fast response to changes in load demands. It can be used to improve utility system operation economics and system stabilities. The power-conditioning circuit interfacing an SMES and a utility network consists of thyristor or gate-turn-off (GTO) device bridges of the combinations of thyristor bridges and GTO bridges. The special requirements for power-conditioning circuits are discussed, and an experimental model system for testing the performance of the proposed circuits is described. The experimental studies concern power transfer of the model system, current balance control, independent real (P) and reactive (Q) power control, online numeric P-Q measurement, and protection of the SMES system. The proposed GTO circuit topology appears to satisfactorily provide independent real and reactive power control and maintain the high efficiency and fast response properties of the SMES system. >

The authors discuss the circuit configurations and design of two AC-to-DC power converters for superconducting magnetic energy storage (SMES) using gate-turn-off (GTO) thyristors. The circuits are current-source rectifiers, so that suppressing the overvoltage on the GTOs during commutation is an important consideration. Moreover, to get high conversion efficiency it is necessary to handle the commutation energy properly. Two circuits are presented for this purpose, and the detailed computer simulation of these circuits is discussed. The resulting design policies and characteristics for both circuits are described, and the best choice of converter circuit for SMES is determined. >

Two-dimensional device model based simulation of power MOSFETs and of power electronics circuits are presented. In order to develop MOSFETs with lower on-resistance at the low temperature region around 80 K device characteristics of a MOSFET for various temperature were examined. Simulated drain characteristics showed good agreement with experimental results. Circuit simulation using two-dimensional device models needs more computation time and memories than the simulation using equivalent circuit models for switching devices such as SPICE type device models. >

Unbundled power quality service is paid much attention under the circumstances of deregulation and diversification of needs of customers for quality and price of electric power. Characteristics of one possible and simple circuit, which enables us to deliver different power quality level to single-phase loads, are presented. The system can supply three levels of power quality to single-phase loads by use of three-phase four-wire AC system, one inverter and a battery. Finally, for a practical usage of the proposed system, location of the system at some places such as factories and individual houses is presented.

This paper presents a new control strategy for parallel active filters. The instantaneous positive sequence extraction of load current and utility voltage is combined with the p-q theory. This method is able to control a four leg active filter for compensation of reactive power, current harmonics, three-phase imbalance and neutral current cancellation simultaneously in 3-phase 4-wire distribution systems. The presented method can operate in harmonic polluted and/or imbalance utility voltage case. The simulation results prove the considerable ability of control strategy to suppress the above-mentioned subjects with a very fast dynamic response. This method is also usable in 3-wire systems.

The transfer switch is one of the most useful devices for power quality improvement. The authors have been studying about the control scheme of a solid state transfer switch for faster and stabler operation, and a hybrid configuration with mechanical and semiconductor switch for lower conduction losses. On the other hand, distributed generators such as wind turbines, photovoltaic generators, micro turbines and fuel cells are coming into the load side. As a new power delivery system with such distributed generations, the Flexible, Reliable and Intelligent Electrical eNergy Delivery System (FRIENDS) is proposed. These situations make the fault current level of distribution networks higher and some fault current limiting devices are required in distribution systems. The authors propose to combine the fault current limiter with the hybrid transfer switch. Configuration of the system, detection method of faults, and experimental results to show the principle are presented.

In this paper, many issues on a new type of power delivery system named FRIENDS (flexible, reliable and intelligent electrical energy delivery system) are discussed. FRIENDS is one of most promising future power delivery systems under deregulated circumstances. The purpose of FRIENDS is to develop a desirable structure for future power delivery systems where distributed generators and distributed energy storage systems are allocated near the demand side, and to develop reliable and energy conservation oriented operating strategies of the power systems. The future power delivery system will be more and more consumer friendly and will be a more and more essential part of the total energy delivery system.

Unbundled power quality service is paid much attention to under the circumstances of deregulation and diversification of needs of customers for quality and price of electric power. One of the features of flexible, reliable and intelligent electrical energy delivery system (FRIENDS) is the unbundled power quality service. It is required to define the power quality in order to design the hardware of quality control center (QCC) in the FRIENDS concept, which is placed in the distribution system to supply several levels of power quality to customers, because there are many aspects for power quality. This paper shows one method to define the quality of power for unbundled power quality service, assuming to supply three levels of power quality such as premium power, high quality and normal quality power. The simplest circuit of QCC for single-phase loads is also presented in this paper.

Transfer switches will play an important role in the flexible, reliable and intelligent electrical energy delivery system (FRIENDS), which is a promising distribution system in the future. Transfer switches will be used for flexible operation of the distribution system and reduction of distribution losses in the FRIENDS system. Although transfer switches using thyristors are already used for power quality improvement, following studies are still needed: (1) transfer characteristics of the switch for various phase difference between two feeders and various power factor have not been studied; and (2) reduction of losses is needed. This paper shows a proper gate control scheme for transfer without causing circulating current. From a loss point of view, a hybrid configuration with mechanical switches and semiconductor switches is studied. Experimental results from the hybrid configuration are also shown in this paper.

For SMES (Superconducting Magnet Energy Storage) composed of Superconducting Magnet (SM) and thyristor converters, the harmonic currents which are generated by SMES converter should be compensated. We have developed active filter, the output of which is adaptively controlled such that the deviation of the waveform of ac line current from the sinusoidal one can be cancelled out. SMES system composed of two sets of GTO (Gate Turn-Off) thyristor converter, 0.5 MJ pulsed SM which are controlled by a direct digital controller, and the active filter, has been developed. The SMES system has been connected to a model power transmission system together with a 10 kVA generator. The controlled characteristics of SMES in the model power transmission system and compensated characteristics of active filter have been experimentally studied. The experimental results show that harmonic currents of SMES can be successfully compensated by active filter, and simultaneous active and reactive power control of SMES can be carried out without the influence of harmonic distortion.

The authors propose the application of superconducting AC coils to superconducting magnet energy storage. The stored energy of the superconducting coil is to be supplied to the AC power line (60 Hz) via a power converter, and the pulsation of supplied power controlled in the frequency range between DC and several tens of hertz. A variable-voltage variable-frequency drive system was developed to study the possibility and characteristics of this sort of SMES system. The developed system is composed of a small superconducting AC coil and MOSFET pulse-width modulation converters. The combination of superconducting AC coil and PWM control can be utilized for SMES stabilization of a power system. >

The result of therapy of 67 cases of children with malignant testicular tumors is presented. The majority of these cases were embryonal carcinoma in which metastases had occurred in the retroperitoneal lymph nodes, lungs, and bones. Long-term survival was obtained in 89% of the cases treated by simple orchiectomy followed by retroperitoneal irradiation. Two cases with metastases benefitted from chemotherapy. The prognosis of embryonal carcinoma of the testis is correlated with the age of the patient and the histologic pattern of the carcinoma; early detection and appropriate treatment are most important for its cure.