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This paper proposes a back electromotive force estimation error compensation method for accurate rotor position estimation of surface mounted permanent magnet synchronous motors. When estimating the rotor position of surface mounted permanent magnet synchronous motor sensorless drives, a direct current offset error component occurs in the voltage sensor. As a result, the rotor position is distorted and the sensorless control in surface mounted permanent magnet synchronous motor is degraded. In addition, the dq-axis voltages in the synchronous reference frame have the direct current offset error component, ripples compared with the motor frequency under the distorted rotor position. In this paper, the effects of the direct current offset errors are analyzed based on the synchronous reference frame phase locked loop. To remove this direct current offset error component, a d-axis voltage is converted into a synchronous reference frame again to compensate. In other words, it is a dual synchronous coordinate conversion compensation method. The compensator utilizes a proportional-integral controller that compensates by estimating the direct current offset error component. The proposed method is useful for the improvement of surface mounted permanent magnet synchronous motor sensorless control and operating performance. The effectiveness of the proposed algorithm is verified through PSIM simulation and experimental results.

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The aim of the study was to investigate the ability of sperm derived from the epididymis in regard to sperm motility, sperm penetration to oocyte and subsequent development of the embryo. Frozen-thawed sperm from epididymis showed similar percentage of motile sperm (VSL ≥ 25 μm/sec) as compared to that of commercial sperm (control).Sperm penetration of frozen-thawed epididymal and commercial sperm was not significantly different. Moreover, cleavage and blastocyst rates were similar in both epididymal and control. Sperm derived from the epididymis also showed fertilizability and subsequent embryonic development

-This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.