An ideal PWM-VSI inverter with feedforward and feedback compensation

This paper presents different compensation techniques based on feedforward and feedback techniques for obtaining an ideal PWM-VSI inverter for AC machines. Linearities like blanking time, voltage drop across the power devices and DC link voltage ripple cause torque and speed fluctuations in the AC machine. Different techniques are proposed and tested for eliminating these nonlinearities. The blanking time compensation is done by both a phase current feedforward and a voltage vector feedback. The voltage drop compensation is realized with a current feedforward and finally the DC link voltage ripple is compensated by a feedforward of the measured DC link voltage. A comparison and the influence of the different compensation techniques are done on a 16-bit microcontroller based PWM-VSI inverter. Test results show a significant improved performance of the AC machine at no load and at low speed when the compensation techniques are used