High-gain feedback in a delta-sigma modulated inverter with carrier

It is noted that, with a high-gain feedback, a PWM (pulse-width-modulated) inverter may start oscillation uncontrolled by the carrier signal. The authors discuss how and to what degree the loop gain can be raised in a first- and second-order delta-sigma modulated PWM inverter, maintaining the synchronism to a carrier. They then report the result of an experiment on a three-phase IGBT inverter, and conclude that with an online parameter adjustment and/or higher-order integral control, high tracking ability and noise immunity over a wide frequency range are achieved.