Dead-Time Interval Controlled and its Impact in THD Parameter

To eliminate the so-called “shoot-through” incident in inverters many solutions have been proposed. However, a large number of them incur additional costs due to the number of circuits used for the elimination of this issue. A time interval, known as the “dead-time,” is applied to prevent circuit damage. This requires additional circuitry for switching, through which the pulse modulation width would change. The wider the “dead-time” interval, the greater the safety; however, this will also result in signal distortion at the inverter output, potentially increasing the Total Harmonic Distortion (THD) value. A method for eliminating the shoot-through effect by increasing and decreasing the amplitude of the carrier signal using a unipolar pulse modulation technique presented. The impact of this interval change on the THD factor is also analyzed. The carrier signal, which takes the form of a triangular waveform, has an amplitude <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A_{c}$</tex> that is shifted to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A_{c}+\xi \_$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A_{c}-\xi$</tex>, from which pulses of different lengths are derived. This approach controls the interrupters for earlier turn-off or later turn-on, respectively, by comparing the harmonic spectra for these cases and comparing the THD values. This paper presents a simple solution using unipolar modulation for single-phase inverters with a Voltage Source Inverter (VSI) configuration.