This paper is focused on a voltage-detection-based shunt active filter for installation on a power distribution system. A main objective of the active filter is to achieve damping of harmonic propagation coming from series/parallel resonance between capacitors for power factor correction and line inductors in the distribution system. The active filter installed at the end terminal of a distribution feeder is controlled in such a way as to present infinite impedance to the external circuit for the fundamental frequency, and to exhibit low resistance for harmonic frequencies. As a result, the active filter acts as a damping resistor for the harmonic propagation, like a 50-Ω terminator installed at the end of a signal transmission line. It is verified by experiment that the active filter intended for harmonic termination has the capability of harmonic damping throughout the distribution feeder. © 2000 Scripta Technica, Electr Eng Jpn, 133(2): 1–10, 2000
Since the late 1950s, power electronics has been developing by leaps and bounds without saturation to become the key technology essential to modern society and human life as well as to electrical engineering. This paper mainly focuses on the state-of-the-art of power electronics technology and its medium to high-power applications because the author cannot survey the whole spectrum of power electronics ranging from a 5 W switching regulator to a 2.8 GW high-voltage DC transmission system now under construction in Japan. This paper also presents prospects and directions of power electronics in the 21st Century, including the personal views and expectations of the author.
This paper deals with a 50‐MW self‐commutated BTB (Back‐To‐Back) system intended for power flow control between transmission networks. It focuses on the dynamic behavior of the BTB system during single‐line‐to‐ground (SLG) faults. During an SLG fault, a DC magnetic deviation appears in the converter transformers used for the BTB system just after the occurrence and restoration of the fault. It is indispensable to understand the magnitude of the deviation, because it may bring about magnetic saturation as well as subjecting the transformers to a large magnetizing current. This paper derives theoretical equations related to the deviation during the SLG fault. The theoretical analysis developed in this paper may make significant contributions to designing the transformers. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(2): 48–59, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20805
This paper describes transient characteristics of a UPFC and its performance of suppressing power flow variation in a power transmission system having two parallel lines. The UPFC is installed in series with the two parallel lines and it controls the total power flow of the lines. Dynamic performance caused by a single line trip is theoretically and experimentally discussed. Experimental results reveal that a conventional control may produce an excessive power flow variation at the instant of the trip. On the other hand, the fast control scheme, which has been proposed by the authors, shows good performance of power flow control without any variation not only in steady state but also in transient state. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 65–75, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.2011
This paper deals with a 50-MW self-commutated back-to-back (BTB) system intended for power-flow control between two ac transmission networks. It focuses on the dynamic behavior of the BTB system during single-line-to-ground and double-line-to-ground faults. Attention is particularly paid to the dc magnetic flux deviation in the grid and converter transformers, and the circulating current inside the grid transformers, which would produce undesirable effects on the system. Theoretical equations related to the amount of circulating current and the dc magnetic flux deviation are derived. The theoretical results developed in this paper are confirmed by computer simulation.
No abstract is provided for this article.
We proposed the following indication criteria for tonsillectomy in patients with IgA nephropathy. (1) IgA nephropathy has been definitively diagnosed by an evaluation of the renal glomeruli during renal biopsy. (2) Tonsillectomy is indicated for patients who demonstrate grade I–III renal pathology and a serum creatinine level of 2.0 mg/dl or less during renal biopsy. However, even among patients who demonstrate grade IV disease or a serum creatinine level higher than 2.0 mg/dl during renalbiopsy, surgery should be considered in the absence of contraindications for tonsillectomy, such as renal hypofunction, providing the patient wants to undergo surgery and informed consent is obtained. (3) The patient's medical history includes deterioration of urine findings during tonsillitis or acute upper respiratory inflammation.(4) Buried tonsils and the attachment of pus plugs to the tonsillar crypt are observed as local findings of the palatine tonsil. (5) Positive findings, especially positive urine findings (hematuria), are detected on the tonsillar provocation test. Items (1) and (2) are essential. Items (3) to (5) are indicative, as their inclusion has not been supported by previous studies.
This paper provides an experimental discussion on dynamic braking for an induction motor driven by a modular multilevel double-star chopper-cell (DSCC) inverter, intended for applications to large-capacity fans and compressors. Each chopper cell consists of a bidirectional chopper and a braking chopper connecting a single small-rated braking resistor in series with a single IGBT (Insulated-Gate Bipolar Transistor). Thus, this configuration leads to a “distributed” dynamic-braking system that provides the practical welcome byproduct of overvoltage protection to each chopper cell. This paper describes a unified control method of the DSCC inverter and all the braking choppers. An experimental induction-motor-drive system rated at 400V and 15kW is designed, constructed, and tested to verify the dynamic-braking performance. Experimental waveforms, along with simulated waveforms, confirm that the distributed dynamic-braking system is feasible and effective in a medium-voltage high-power DSCC inverter for an electric motor drive having large-capacity fans and compressors.
This paper proposes a small‐sized passive EMI filter for the purpose of eliminating high‐frequency shaft voltage and ground leakage current from an AC motor. The motor is driven by a general‐purpose PWM inverter connected to a three‐phase grounded voltage source. The passive EMI filter requires access to the ungrounded neutral point of the motor. This unique circuit configuration makes the common‐mode inductor effective in reducing the high‐frequency common‐mode voltage generated by the PWM inverter with a carrier frequency of kHz. As a result, both high‐frequency shaft voltage and ground leakage current can be eliminated very efficiently. However, the common‐mode inductor may not play any role in reducing the low‐frequency common‐mode voltage generated by the diode rectifier, so that a low‐frequency component still remains in the shaft voltage. Such a low‐frequency shaft voltage may not produce any bad effect on motor bearings. The validity and effectiveness of the EMI filter are verified by experimental results obtained from a 200‐V 5‐kVA laboratory system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 80–87, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20243
This paper provides a theoretical and experimental discussion on a modular multilevel triple-star bridge-cell (TSBC) converter with focus on mitigating the capacitor-voltage fluctuation contained in each bridge cell. This paper assumes that the TSBC converter drives an interior permanent magnet synchronous motor rated at 75Hz loaded at the rated torque. A new control method proposed in this paper is characterized by properly superimposing both common-mode voltage and circulating currents in the whole speed range from 0 to 75Hz. Moreover, this paper optimizes the amplitude and frequency of the superimposed common-mode voltage with the help of theoretical analysis, thus resulting in minimizing the voltage fluctuation. This optimized control method can reduce both the voltage fluctuation and the cluster-current amplitude to values below those of existing methods. Experimental waveforms obtained from a three-phase downscaled model verify good start-up performance from a standstill to the rated speed.
No abstract is provided for this article.
This paper considers the control of a series active filter integrated with a double-series diode rectifier. It is shown that, as result of delays introduced by digital control, current-mode control is preferred to voltage-mode control for digital implementations. A Fourier-based method for generating balanced current references with optimized power factor is presented. The advantage of current-mode control is illustrated by simulation and the Fourier-based method is verified by experiment.
Oncocytes are characterized by a remarkable number of mitochondria as demonstrated by electron microscopy. Oncocytomas are very rare tumors that are usually benign and typically occur in the parotid gland. Oncocytic carcinomas are exceedingly rare in the salivary glands. We describe a 69‐year‐old Japanese man with an oncocytic carcinoma of the submandibular gland. We reviewed 38 articles describing oncocytic carcinoma of the head and neck that included clinicopathologic features. Oncocytic carcinomas appear to arise from benign oncocytomas, or may also arise de novo . In oncocytic carcinoma of the head and neck, the presence of distant, rather than local lymph node, metastasis is the most important prognostic indicator.
