A Novel DROGI Algorithm for Non-linear Unbalanced Load Compensation using Four-leg Converter

Abstract

This paper proposes a novel control algorithm for a four-leg converter to compensate unbalanced non-linear loads in three-phase four-wire system. The detection and compensation for unbalanced non-linear load currents is implemented using double reduced order generalized integrators (DROGI) with proportional resonant (PR) controller. One integrator of DROGI is used to extract the reference compensation harmonics, and the second integrator is applied to decompose compensation currents and rectification currents at the converter side. The compensation currents are regulated by multi-PR controller, and the rectification currents are controlled by proportional controller. As a result, the compensation mode (DC-AC) and rectification mode (AC-DC) of converter are decoupled. More flexibility and selectivity in terms of control methods are achieved. The effectiveness of the control algorithm is verified by simulation and experiment.