Power maximization control of variable‐speed wind generation system using permanent magnet synchronous generator

This paper proposes sensorless output power maximization control of a wind generation system. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. The generator torque is suitably controlled according to the generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control method, where the information on wind velocity is not required. Moreover, the maximum available generated power is obtained by the optimum current vector control. The current vector of PMSG is optimally controlled according to the generator speed and the required torque in order to minimize the losses of PMSG considering the voltage and current constraints. The proposed wind power generation system can be achieved without mechanical sensors such as wind velocity detector and a position sensor. Several experimental results show the effectiveness of the proposed control method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 11–19, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20043     

Position and speed sensorless control system of permanent magnet synchronous motor with parameter identification

The model parameters of a permanent magnet synchronous motor (PMSM) are required for high‐performance control and a model‐based sensorless control. This paper proposes a sensorless control system of PMSM that does not need parametric information beforehand. The parameters of a PMSM drive system, including the inverter, are identified at standstill and under operating conditions. At first, the initial rotor position is estimated by a signal injection sensorless scheme in which the machine parameters are not required. After the initial position has been estimated, the resistance, including the on resistance of the IGBT, the voltage error caused by dead time in the inverter, and d‐axis and q‐axis inductances, are identified at standstill. After the motor starts by the signal injection sensorless control, the sensorless scheme changes to an extended EMF estimation scheme. The estimated parameters for the resistance, and daxis and q‐axis inductances are used in such sensorless control. The magnet flux‐linkage, which cannot be estimated at standstill, is identified under the sensorless operation at medium and high speeds. The effectiveness of the proposed method is verified by several experimental results. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 68–76, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ eej.20548     

A permanent magnet‐assisted synchronous reluctance motor

Permanent magnet motors have attracted a lot of attention recently for their potential for saving energy. However, they are only used for certain applications because the magnets are expensive. This paper discusses the optimum design of the low‐cost, highly efficient magnet‐ assisted reluctance motors with a minimum amount of magnets. The motor considered in this study is a multi‐flux barrier reluctance motor. The configuration by which permanent magnets are embedded to the innermost side of the rotor to obtain maximum output with the minimum amount of magnets was evaluated through simulation and experiments with a prototype motor. As a result, we established a method for designing motors capable of realizing the same efficiency as permanent magnet motors with only one‐fourth the amount of magnets. In our experiments, we achieved a high efficiency of 94.5% with a 750‐W motor. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 66–74, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10123     

Determination of the π-charge distribution of the DMe-DCNQI molecule in (DMe-DCNQI)2M, M=Li, Ag, and Cu

Solid state high-resolution NMR of¹H and¹³C along with¹⁵N is analyzed to investigate the electronic states of the charge transfer salts, (DMe-DCNQI)₂M, (M=Li, Ag, and Cu). We determined the spin/charge distribution in a DMe-DCNQI molecule of the Li-salt from the Knight shifts at each atom on the molecule. It is found that the obtained charge distribution is similar to the theoretical prediction. The charge density on the DCNQI molecules of the Ag-salt is found to be smaller by 20% than the Li-salt, which could be an origin of differences from the Li-salt. This result is consistent with the first principle calculations (T. Migazaki and K. Terakura, Phys. Rev. B 54, 10452 (1996)).     

Structure and Characteristics of High‐Performance PMASynRM with Ferrite Magnets

Recently, the use of permanent magnet (PM) motors has risen markedly because of improvements in the performance of rare earth PM motors. However, the use of rare earth materials, which is an important aspect of the high‐performance PM motor, should be reduced because of the high cost and unpredictability associated with procuring such materials. The performance of motors that use rare earth materials has reached a very high level, one that will not be easy to match without such materials. In this paper, we propose a structure for a high‐power‐density PM‐assisted synchronous reluctance motor involving the use of a ferrite PM. The structure prevents irreversible demagnetization of the PM even in the presence of heavy flux‐weakening excitation or an inverter fault. It is shown that the proposed structure achieves high‐power and high‐efficiency performance. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 42–50, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22362     

Two Major Bile Acids in the Hornbills, (24R,25S)-3α,7α,24-Trihydroxy-5β-cholestan-27-oyl Taurine and Its 12α-Hydroxy Derivative

Two major bile acids were isolated from the gallbladder bile of two hornbill species from the Bucerotidae family of the avian order Bucerotiformes Buceros bicornis (great hornbill) and Penelopides panini (Visayan tarictic hornbill). Their structures were determined to be 3α,7α,24‐dihydroxy‐5β‐cholestan‐27‐oic acid and its 12α‐hydroxy derivative, 3α,7α,12α,24‐tetrahydroxy‐5β‐cholestan‐27‐oic acid (varanic acid, VA), both present in bile as their corresponding taurine amidates. The four diastereomers of varanic acid were synthesized and their assigned structures were confirmed by X‐ray crystallographic analysis. VA and its 12‐deoxy derivative were found to have a (24R,25S)‐configuration. 13 additional hornbill species were also analyzed by HPLC and showed similar bile acid patterns to B. bicornis and P. panini. The previous stereochemical assignment for (24R,25S)‐VA isolated from the bile of varanid lizards and the Gila monster should now be revised to the (24S,25S)‐configuration.     

Recent technical trends in permanent magnet synchronous motors

This paper presents an overview of the recent technical trends in permanent magnet synchronous motors (PMSMs), especially the rare earth (RE)‐less PMSMs that have been developed in Japan. The RE‐less PMSMs, along with PMSMs with reduced RE permanent magnets (PMs), PM‐assisted synchronous reluctance motors (PMASynRM) with ferrite PMs, spoke‐type interior PMSMs (IPMSMs) with ferrite PMs, and axial‐gap PMSMs with ferrite PMs, are reviewed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

REVIEW

The exponential growth of research activities in nanotechnologies, as well the rapidly increasing utilization of microscale technologies in societal applications, is affecting directly the development and implementation of corresponding numerical methodologies in many scientific and technological areas, including heat transfer. Of particular interest are length scales at which the continuum approach ceases to be valid. Molecular Dynamics (MD) simulation is a very promising, general method to study such scales, allowing for the direct simulation of the motion and interaction of particles (atoms or molecules). This paper reviews recent works on molecular dynamics in heat transfer, focusing on, but not limited to, challenging interfacial and phase change phenomena to demonstrate the advantages, potential, and the current limitations of this methodology.     

Diameter-controlled and nitrogen-doped vertically aligned single-walled carbon nanotubes

Diameter controlled and vertically aligned single-walled carbon nanotubes were synthesized from pure and mixed ethanol/acetonitrile feedstock. With increasing acetonitrile concentration in the feedstock, nitrogen incorporation into the sp² carbon network increased until saturating at approximately one atomic percent. The incorporation of nitrogen correlates with a significant diameter reduction from a mean diameter of 2.1 nm down to 0.7 nm. Heteroatom-mediated diameter control is independent of catalyst preparation and represents a versatile tool for the direct synthesis of tailored single-walled carbon nanotubes.     

Evaluation of protein adsorption on hydrogenated amorphous carbon films by surface plasmon resonance phenomenon

To develop an anti-thrombogenic coating, hydrogenated amorphous carbon (a-C:H) and related films were studied in terms of their protein adsorption during the initial process in thrombogenesis by surface plasmon resonance (SPR) phenomenon using a multilayer device consisting of an a-C:H layer on Au. Two a-C:H films with different hydrogen contents, a nitrogenated a-C:H (a-C:N:H) and a fluorinated amorphous carbon (a-C:F) film were prepared on the Au layer in the multilayer device. Human serum albumin (HSA) in a phosphor buffer (PB) was used as a protein. Na₂HPO₄·12H₂O, NaH₂PO₄·2H₂O and deionized water were mixed to coordinate PB. From the attenuation of reflected light, the SPR angle was determined to the angle at minimum reflection intensity. The observed behavior of the SPR angle indicated that HSA was adsorbed on all films. The SPR angle was analyzed to estimate the multilayer index of the HSA-adsorbed layer on each film. The HSA adsorption ability of both a-C:H and a-C:N:H films was similar, and the absorption ability of the a-C:F film was lower than that of the other films. Hence, the surface polarization dominates the adsorption ability of HSA on a-C:H films and related film.