Publications

A Position-Sensorless IPM Motor Drive System Using a Position Estimation Based on Magnetic Saliency

This paper describes position-sensorless control of an interior permanent magnet synchronous motor (IPM motor), which is characterized by real-time position estimation based on magnetic saliency. The real-time estimation argorithm proposed in this paper determines the inductance matrix including rotor position information from current harmonics produced by switching operations of an inverter driving the IPM motor, and then estimates the rotor position every period of pulse-width modulation (PWM). Position estimation without any special signal injection is achieved with a satisfactory response and accuracy even at a standstill and at low speed. An experimental system consisting of an IPM motor and a voltage-source PWM inverter has been implemented and tested to confirm the effectiveness and versatility of the approach. Some experimental results show that the experimental system has the function of electrically locking the loaded motor, along with a position response of 20rad/s and a settling time of 300ms.

A speed-sensorless startup of an induction motor driven by a modular multilevel cascade inverter (MMCI-DSCC)-Applications to quadratic-torque loads like fans, blowers, and compressors

A modular multilevel cascade inverter based on double-star chopper-cells (MMCI-DSCC) has been expected as one of the next-generation multilevel PWM inverters for medium-voltage high-power motor drives. This paper has theoretical and experimental discussions on a speed-sensorless startup of an induction motor driven by the MMCI-DSCC, especially when this motor drive is applied to fans, blowers, and compressors, the torque of which is proportional to a square of a motor mechanical speed. A theoretical analysis focusing on ac-voltage fluctuation of each dc capacitor indicates that the ac-voltage fluctuation can be kept within an acceptable level over a wide range of motor mechanical speeds by controlling the three-phase stator currents. Experimental steady-state waveforms obtained from a downscaled motor drive verify operating performance with a quadratic-torque load.

High-dose Administration of Levofloxacin (LVFX) in the Treatment of Acute Exacerbation of Chronic Otitis Media.

Thirty-two adult cases of acute exacerbation of chronic otitis media (COM) were treated by high-dose (600mg/day) oral administration of levofloxacin (LVFX). Clinically, 27COM cases (84.4%) were effectively treated, and no apparent side effects were noted during this study protocol. Among 31 clinically isolated strains whose therapeutic outcomes were bacteriologically confirmed, 28 (90%) strains were not detectable after high-dose LVFX treatment. Bacteriological therapeutic failures in the treatment were observed in three COM patients with MRSA and a patient with coagulase-negative staphylococci. High-dose administration of LVFX was effective in the treatment of acute exacerbation of COM except in cases that were caused by drug resistant staphylococci.

Control strategy and dynamic performance of a doubly-fed flywheel generator-motor; Koryu reiji flywheel hatsudenki no seigyoho to kato tokusei

A doubly-fed flywheel generator-motor consists of a wound-rotor induction machine and a cycloconverter or a voltage-source PWM rectifier-inverter which is used as an ac exciter. Adjusting the rotor speed makes the generator-motor either release the kinetic energy to the power system or absorb it from the power system. Thus, the generator-motor has the capability of achieving, not only reactive power control, but also active power control based on a flywheel effect of the rotor. A 200-MJ flywheel generator-motor for the purpose of line-frequency regulation on a 132-kV bus has been installed and commissioned by the Okinawa Electric Power Company. However, little literature has been published on control strategy and dynamic performance analysis of doubly-fed flywheel generator-motors. This paper proposes a new control strategy for a doubly-fed flywheel generator-motor, which is characterized by the combination of vector control and decoupling control. The control strategy enables the flywheel generator-motor to perform active power control independent of reactive power control even in transient states. The validity of the theory developed in this paper; along with the effectiveness of the control strategy, is confirmed by computer simulations using EMTDC. In addition, this paper discusses the transient behavior of a magnetizing current of the flywheel generator-motor. The flywheel generator-motor based on leading edge power electronics and electric machine technologies shows promise as a versatile power conditioner, in particular, being capable of repetitively absorbing or releasing electric energy for a short period of time less than a minute. 18 refs., 9 figs., 1 tab.

A vector control system using a neutral‐point‐clamped voltage‐source pwm inverter

This paper describes a vector control system of an induction machine using a neutral‐point‐clamped voltage‐source inverter (NPC‐VSI) that is one of the double series‐connected inverters. The NPC‐VSI is able to output five‐level step‐shaped line‐to‐line voltage without output transformers or reactors, and it may reduce harmonic currents corresponding to torque ripples. However, the NPC‐VSI has a problem in that excessive high voltage is applied to switching devices when a neutral point of two dc capacitors of the NPC‐VSI varies from the center of the dc link voltage, because the neutral point is floating. This paper proposes also a current controller to which the space vector theory is applied. This can reduce harmonic currents to one‐fourth those of a conventional voltage‐source inverter using six switching devices, and regulate the neutral point potential within a preset range. To simplify the current controller, information about voltage space vectors is given from the vector controller to the current controller. The validity of the current controller is confirmed by a prototype using an induction machine of 2.2 kW.

Development of a 500-kW Modular Multilevel Cascade Convertor for battery energy storage systems

Natural energy sources such as wind turbines and photovoltaic power generators cause instability of the power grid due to their output fluctuations. Battery energy storage systems (BESSs) are being considered as a countermeasure for this issue. A Modular Multilevel Cascade Convertor (MMCC) is one suitable circuit topology for BESSs, because each cell can control each battery's state-of-charge independently, and the level of generated harmonics is low enough to eliminate the AC filter normally installed in conventional two level converters. This paper describes the development of a real-scale (500 kW) H-bridge MMCC for BESSs and reports successful test results of the control functions with a scale down grid model and a 6.6-kV real-scale distribution line.

<title>Dynamic observation of facial movements by moire topography video</title>

The moire topography video visualizes the facial movement dynamically in three dimensions. By using the digital video, we analyze facial movements in expression more precisely, because we can handle dynamic images as the series of static images with time axis. This technique reveals several special features on the facial expression.

Transient analysis of a unified power flow controller, and its application to design of the DC-link capacitor

This paper presents a transient analysis of a unified power flow controller (UPFC), and design of capacitance of the DC-link capacitor based on that analysis. Active power flowing out of the series device in transient states is theoretically discussed to derive what amount of electric energy the DC link capacitor absorbs or releases through the series device. As a result, it is clarified that the active power flowing out of the series device is stored in the line inductance as magnetic energy during transient states. Design of capacitance of the DC-link capacitor is also presented in this paper, based on the theoretical analysis. Experimental results obtained from a 10 kVA laboratory setup are shown to verify the analytical results.

Active and hybrid filters for power conditioning

This paper describes principles, system configurations, control strategies and implementations, and filtering characteristics of active and hybrid filters for power conditioning. Their practical applications are expanding not only into office-buildings, hospitals, water supply utilities and rolling stock but also into electric power utilities. For example, a hybrid filter consisting of a 5 MVA series active filter and a 25 MVA shunt passive filter has been installed at the Yamanashi test line for high-speed magnet-levitation trains. The series active filter makes a great contribution to damping of harmonic resonance between the supply inductor and the shunt passive filter.

Osteoma with cholesteatoma in the external auditory canal

We report an unusual case of a 13-year-old girl with a benign osteoma associated with a cholesteatoma in the external auditory canal and serous otitis media. The osteoma was located in the antero-inferior wall of the right external auditory canal. A cholesteatoma was present between the osteoma and the tympanic membrane. Computed tomography revealed a soft tissue density within the external auditory canal and in the middle ear cleft. The shadow in the middle ear cleft was considered to represent the serous otitis media. Surgical removal of the osteoma and cholesteatoma proved successful, and no recurrences or complications have occurred in the first year postoperatively.

Experimental Verification of a Virtual Medium-Voltage High-Speed Synchronous-Motor Drive Test System Based on Two Modular Multilevel DSCC Converters

This paper discusses the experimental verification of a virtual synchronous-motor drive test system. This test system consists of two identical modular multilevel double-star chopper-cell (DSCC) converters characterized by a front-to-front (FTF) connection. One converter acts as an inverter under test, while the other acts as a part of the virtual motor and load. The experimental waveforms obtained from the test system designed and constructed in this paper confirm satisfactory electrical and mechanical dynamics of the virtual three-phase 200-V, 10-kW, two-pole, 18,000-r/min synchronous motor with a virtual quadratic-torque-to-speed load an as a high-speed compressor. The driving performance of the test system shows that the DSCC inverter under test is applicable to high-speed synchronous motor drives.

Power compensation effect of an adjustable-speed rotary condenser with a flywheel for a large capacity magnet power supply

Direct connection of the synchrotron magnet power supply to the utilities causes the effect of pulsed reactive and active power in the AC line. Conventionally, Static Var Control system compensates the reactive power generated by the thyristor converter to reduce the flicker in the power line. However, it is necessary to control not only a reactive power but also an active power for the future large scale synchrotron magnet power supply in order to reduce the dissipation power and to realize the stabilization in the AC line. An adjustable-speed rotary condenser is capable of not only reactive power control but also active power control since it utilize a flywheel effect of the rotor. Research and development on these problems are now under going using a model system of 7.5 kW rotary condenser with flywheel (GD/sup 2/=3kg-m/sup 2/). Control and characteristic of an adjustable-speed rotary condenser and the experiment results will be presented.

A zero-current-switching based three-phase PWM inverter having resonant circuits on AC-side

The authors present a zero-current-switching (ZCS)-based three-phase PWM (pulse-width-modulated) inverter having small resonant circuits on the AC side, whose resonant frequency is 50 kHz. The ZCS inverter can greatly reduce the switching losses and electromagnetic noise. The principle of ZCS operation, the design of the resonant circuits, and the control sequence are described from theoretical and practical points of view. Experimental results obtained from a ZCS PWM inverter driving an induction motor of 2.2 kW are shown to verify the practicability of this device.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Which is more suitable for MMCC-based medium-voltage motor drives, a DSCC inverter or a TSBC converter?

This paper provides theoretical, numerical, and experimental comparisons in electrical-drive performance between a double-star chopper-cells (DSCC) inverter and a triple-star bridge-cells (TSBC) converter. The inverter and converter are two of the most promising members of the modular multilevel cascade converter (MMCC) family. Two sets of downscaled electrical drives using the DSCC inverter and the TSBC converter are designed, constructed, and tested, along with the common three-phase four-pole induction motor rated at 380 V, 15 kW, and 50 Hz. This paper presents experimental waveforms of the electrical drives loaded with a quadratic torque-to-speed profile and at the rated torque.

A Novel Control Scheme for Current-Controlled PWM Inverters

A high-performance current-controlled inverter must have a quick current response in transient state and low harmonic current content in steady state. However, in general, these requirements contradict each other. A novel control scheme is proposed which is based on the current deviation vector and satisfies both requirements. Experimental results showed good agreement with the anticipated performance.

モジュラー・マルチレベル・カスケード変換器 (MMCC) ―III. DSCC (Double-Star Chopper-Cells)方式BTBシステムの基礎実験―

Low-Voltage-Ride-Through (LVRT) Control of an HVDC Transmission System Using Two Modular Multilevel DSCC Converters

This paper presents an intensive discussion on a high-voltage direct-current (HVDC) long-distance transmission system combining two modular multilevel double-star chopper-cells (DSCC) converters with dc power cables. Hereinafter, each converter is referred to simply as a DSCC converter, or just as a DSCC for more simplicity. Such an HVDC transmission system is required to provide low-voltage-ride-through (LVRT) capability to enhance system availability. This paper proposes a practical LVRT control characterized by the use of power-line communications between the two DSCC converters. The validity and effectiveness of the LVRT control is verified not only by simulated waveforms obtained from the software package "PSCAD/EMTDC" but also by experimental waveforms from a three-phase 200-V, 400-Vdc, 10-kW, 50-Hz downscaled system with 300-m-long dc power cables.

A robust modified model predictive control (MMPC) based on Lyapunov function for three-phase active-front-end (AFE) rectifier

This paper proposes a robust modified model predictive control (MMPC) algorithm based on Lyapunov function for a three-phase active-front-end (AFE) rectifier in order to improve the system performance as well as ensure the stability, robustness, and fast dynamic response. The proposed control technique utilizes the discrete behavior of the converter considering the unavoidable quantization errors between the controller and the control actions selected from the finite control set of the AFE rectifier. The proposed MMPC method increases the dynamic response by avoiding the calculation of future current for every switching states. Moreover, the nonlinear system stability of the proposed MMPC technique is ensured by a 2.5 kW experimental system and the direct Lyapunov method. Detailed robustness analysis with experimental parameter variations are provided to show the efficacy of the proposed Lyapunov function based MMPC technique.