| Summary: | 碩士 === 國立彰化師範大學 === 電機工程學系 === 102 === Variable frequency drives (VFD) which can be considered as a bidirectional frequency converter. In recent years, VFD has been widely used in AC motor speed control. However, VFD was caused power quality problem such as three-phase unbalance, voltage flicker by users, but interharmonic and harmonic also can be caused from VFD which is connected with AC motor in grid side. As a result, interharmonic from VFD is regard as a major source of light flicker. The major purpose of paper is to measure the interharmonic in realistic VFD circuit and according to IEC standard measurement. As a result, this paper also proves a limit on the measurement interharmonics which valid range based on the IEC 61000-4-15 standards. We also can see that interharmonics can be amplified which is almost equal to system resonance frequency. For harmonic measurement of the six-pulse VFD model, the FFT method is used to calculate the frequency spectrum of the voltage and current waveform THD from AC source side by this paper.
Meanwhile, this paper also considered to measure interharmonic from AC/DC/AC power converter of DFIG wind turbine model, and we also fix the proposal procedure which is according with IEC 61400-21 and IEC 61000-4-7 standard by wind turbines connected to the grid of distributions system model. In the other hand, we also find out how much interharmonic component in IEC measurement range.
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