A Mode Switching-Based Decentralized Secondary Control for Microgrids With Hybrid Droop and Master-Slave Structure

Abstract

The hybrid droop and master-slave structure studied in existing work complements the advantages of droop control and master-slave control, at the cost of frequency and voltage deviations in microgrids. To eliminate these deviations and maintain accurate power sharing among distributed generators, this paper proposes a decentralized secondary control method based on mode switching, where the secondary controller switches among three modes. In the first mode, a feedback strategy is applied to maintain accurate power sharing among slave distributed generators, and then the load demand is estimated and redistributed among distributed generators to calculate new secondary control commands in the second mode, which are further updated in the third mode to eliminate frequency and point-of-common-coupling bus voltage deviations. The proposed method is communication-free and is able to eliminate the influence of triggering delay among slave distributed generators during the mode switching. The effectiveness of the proposed method is verified through hardware experiments.