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This paper proposes a control strategy for matrix converters to reduce the torque ripple in the overmodulation range. In the overmodulation range, motor drive performance of matrix converters is deteriorated because of the output voltage saturation. In particular, the torque ripple which has lower frequency components than the input voltage frequency is remarkable. This paper presents a theoretical analysis of the causes of the torque ripple and the effect of the proposed control strategy. Experimental examinations including performance comparison with a trapezoidal wave modulation are carried out using a 400-V, 22-kW experimental system. The experimental results verify the validity of the theoretical analysis and confirm the effectiveness of the proposed control strategy for reducing the torque ripple. Furthermore, the harmonic distortion of the output current is also reduced compared with the trapezoidal wave modulation. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(4): 40–48, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20829 [ABSTRACT FROM AUTHOR]

In this paper, a novel control method for a matrix converter is proposed. The proposed method is a PAM (Pulse Amplitude Modulation) control method based on a virtual AC/DC/AC conversion method. Output voltage amplitude is controlled by controlling a virtual DC link voltage with a virtual rectifier. Output frequency is controlled by a virtual inverter. First, the proposed method is explained. Next, the validity of the proposed method is confirmed through simulation and experiment using a 750-W prototype matrix converter. Moreover, various characteristics of the proposed method and conventional virtual AC/DC/AC method are compared through experiment. As a result of the experiment, it has been understood that total harmonic distortion of output current and common-mode voltage can be reduced compared with the case of using a conventional virtual AC/DC/AC conversion method. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 88–96, 2009; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20601 [ABSTRACT FROM AUTHOR]

This paper deals with the hybrid shunt active filter for harmonic compensation of a three-phase diode rectifier in a 480-V adjustable-speed motor drive system. The hybrid filter is formed by a three-phase LC filter tuned around the seventh harmonic frequency and a small-rated three-phase voltage-source PWM inverter. The LC filter and PWM inverter are directly connected in series. As a result, the DC capacitor voltage of the PWM inverter in the hybrid filter is much lower than that of a conventional pure shunt active filter. This results in higher efficiency, less switching ripple, and less EMI emission. Computer simulation is carried out to compare the hybrid filter with the pure filter in terms of circuit configuration and filtering performance. Simulation results indicate that the hybrid filter is superior in effectiveness and viability to the pure filter. In addition, theoretical analysis based on vector loci confirms the validity of the simulation results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(2): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20145 [ABSTRACT FROM AUTHOR]

This paper proposes a transformerless shunt hybrid filter for harmonic compensation of a three-phase six-pulse diode rectifier, where the AC line-to-line voltage is 3.3 or 6.6 kV. The hybrid filter consists of a single tuned LC filter per phase and an active filter with a DC capacitor voltage as low as 300 or 600 V. The two filters are directly connected in series with each other without a transformer. The passive filter absorbs harmonic currents produced by the rectifier, whereas the active filter improves the filtering characteristics of the passive filter. The required rating of the active filter is much smaller than that of a conventional shunt active filter used alone. Another advantage is that no additional switching-ripple filter is required for the active filter because the LC filter acts not only as a tuned LC filter around the seventh-harmonic frequency but also as a switching-ripple filter around 10 kHz. A feedforward control scheme is also proposed to improve the active filter performance. Experimental results obtained from a 200-V, 5-kW laboratory system and simulation results of a 3.3-kV, 300-kW system confirm the validity and effectiveness of the system. The hybrid filter gives satisfactory compensation performance, thus allowing us to put it into practical use. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 54–65, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10236 [ABSTRACT FROM AUTHOR]

PACE4 (paired basic amino acid cleaving enzyme) is a member of a family of the mammalian kexin-like proprotein convertases containing a subtilisin-like catalytic domain. Previously we reported seven isoform mRNAs of PACE4 that vary in size and 3′-coding sequence [A. Tsuji et al. (1994) Biochem. Biophys. Res. Commun. 200, 943–950; K. Mori et al. (1997) J. Biochem. 121, 941–948]. To determine the origin of these isoforms, the entire human PACE4 gene has been isolated as a set of overlapping genomic DNA fragments, and analyzed by restriction enzyme digestion and nucleotide sequence determination. The human PACE4 gene spans at least 250 kb and is distributed over 25 exons that range in size from 39 to 1,422 base pairs. Human PACE4 gene is the largest kexin-like proprotein convertase gene reported to date. The most striking feature of its genomic structure is the size of the introns and the number of exons, although the general organization of signal peptide, propeptide, and catalytic domains, which are conserved in this family, is very similar to that reported for other kexin-like protease genes. The structural analysis of PACE4 genomic DNA indicates that multiple PACE4 transcripts are produced as a consequence of alternative RNA splicing events, including exon skipping, and differences in the usage of the inner 5′-splicing donor and polyadenylation sites. A major transcriptional start site was detected 314 bp upstream from the ATG translational start site by primer extension analysis. Sequence analysis of the 5′ -flanking region revealed that PACE4 gene lacks TATA and CCAAT boxes in the proximal upstream region of the start site, although potential binding sites for several transcription factors including SP1, AP1, AP2, PEA3, Ets-1, GHF (growth hormone factor)-1, CREB (cyclic AMP response element binding protein), and basic helix-loop-helix proteins, were present. An unusual sequence of six tandem repeats of a nonadecamer (GGCCTGGGGGTTCACCTGC) containing an E box is found in the 5′ -flanking region. These results suggest that PACE4 is not a constitutive gene product and its expression is regulated by various transcription factors. [ABSTRACT FROM AUTHOR]