Dynamics and THD Improvement in AC Programmable Power Supplies

This paper presents improvement of THD in an AC programmable power source. The AC source contains 2 parts, an AC to DC converter which functions as a power factor correction, and a DC to AC PWM inverter with multi loop control strategy. The AC/DC converter can change the DC bus voltage and provide load to line isolation. The PWM inverter controller is designed using deadbeat theory to achieve fast dynamics, and it has an output voltage decoupling mechanism to improve performance of the inner current loop. But at low output voltage, The PWM inverter can't provide low THD. It happens as a result of decreasing pulse width of the output PWM, and these are neglected by dead band effect. By decreasing the DC voltage, both THD and overall efficiency improves, which is investigated in this paper