Improved one-cycle-control scheme for three-phase active rectifiers with input inductor-capacitor-inductor filters

This study presents an improved one-cycle-control (OCC) scheme that can be applied to a three-phase active rectifier with a third-order input LCL filter. In brief, the proposed OCC active rectifier is not burdened by even harmonic generation problems faced by existing OCC schemes when applied to three-phase systems. With an appropriate damping technique used together with its non-linear control core, the presented OCC scheme can promptly damp off all resonant modes, allowing the higher order LCL filter to be connected at the rectifier three-phase input for better ripple suppression without introducing instability problems. It is also shown that active rectifiers controlled by the proposed OCC may exhibit significant loss reduction under passive damping and much lower total harmonic distortion of input currents under active damping mode. Furthermore, implementation issues such as selection of feedback variables, tuning of damping gain and over-modulation avoidance in three-phase OCC control are also discussed with their practicalities verified experimentally on a 1 kW laboratory prototype.