Abstract
A feedback control seems to be useful to improve regulation and accuracy of an inverter. However, it has been pointed out that a feedback around a triangular wave carrier PWM inverter may cause a switching of output signal independent of the carrier frequency.
An analysis of a voltage-output PWM inverter with an integral feedback loop suggests that, if a dead time element is incorporated in the pulse transfer path of the inverter and if the dead time is adjusted depending on the reference input value, then the output pulse can be synchronized to the carrier even at a higher loop gain.
This was verified in a series of experiments conducted with a three-phase transistor inverter. As the dead time was adjusted properly, the three output pulse sequences were synchronized to the carrier signal when the reference input value was within 78% of full range. Outside this range, the output pulse frequency lowered. Sinusoidal disturbances up to half the carrier frequency were reduced by the increased-gain feedback control.
