A Single-Loop Repetitive Voltage Controller with an Active Damping Control Technique

This paper proposes a single-loop repetitive voltage control strategy which incorporates the active damping control feature for single-phase uninterruptible power supply (UPS) applications. The proposed method reduces the effect of the LC resonant peak, which limits the control bandwidth and deteriorates the stability of the entire control loop by effectively increasing the damping component. Due to the increased stability margin, a repetitive controller working together with a proportional-resonant (PR) controller can be easily adopted. Moreover, the voltage error is minimized even under severe non-linear load conditions. It is confirmed that the proposed single-loop controller achieves excellent and stable voltage regulation performance by evaluating the entire loop-gain of the system and the output impedance. Both the simulation and the experimental results for a 1.5 kW UPS inverter show agree well with the analyses, and the excellence of the proposed method has been verified.