Hierarchical voltage imbalance control for single-/three-phase hybrid multimicrogrid

Abstract

With the rapid development of distributed generation (DG), microgrids and multimicrogrids (MMGs) appear at the end of distribution networks. For the islanded operation of a single-/three-phase hybrid MMG, a hierarchical coordinated control scheme is proposed in this study that includes primary and secondary levels. A compound control strategy based on quasiproportional resonant and robust control is proposed for the primary voltage/frequency control to suppress voltage fluctuations caused by sudden changes in load power and DG output power; a coordinated strategy regarding tie-line power at the point of common coupling (PCC) is proposed for the secondary control to simultaneously improve voltage imbalance at the terminal of the master power supply, PCC, and load terminal. The proposed hierarchical coordinated control scheme is compared with conventional proportional-integral control and a control method based on the PCC to verify its performance. Test studies verify the superior robustness and voltage imbalance control performance of the proposed control scheme in coping with a sudden change in power and unbalanced loads.