Abstract
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.
Highlights
Uninterruptible power supplies (UPSs) are employed to protect critical loads from a short or long interruption [1,2,3,4,5]
The digital signal processor (DSP) board contains a 4-channel digital-to-analog converter (DAC), so that the control variables can be monitored via an oscilloscope
This paper proposes a single-loop voltage control strategy based on active damping control for
Summary
Uninterruptible power supplies (UPSs) are employed to protect critical loads from a short or long interruption [1,2,3,4,5]. It has been found that the capacitor current feedback method in multi-loop voltage control strategies has better transient characteristics using the inductor current feedback scheme [7]. A single-loop structure can be a good candidate for voltage control as long as the resonant peak can be properly damped, and its stability margin can be secured. Repetitive controllers have been employed in UPS and grid-tied inverter applications, because periodic voltage have popularly been proposed. In periodic [14], the voltage single-loop repetitive control strategy was grid-tied inverter applications, because errordirect can be significantly reduced [10,11,12,13]. The capacitor voltage feedback based active damping technique was single-loop repetitive control scheme with reduced sampling numbers.
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