A Novel Decentralized Control for Cascaded-Type AC Microgrids Operating in Grid-Connected and Islanded Modes

The cascaded-type microgrid is proposed to promote the application of microgrids at the high-voltage level. The conventional P-f droop control method cannot perform a unified characteristic to guarantee stable operation in both grid-connected and islanded modes. A novel Q-f droop control is proposed in this paper to realize a unified power control for cascaded-type AC microgrids operating in grid-connected and islanded modes in a fully decentralized manner. The power transmission characteristics of the cascaded system in two modes are analyzed, respectively. Then the steady-state performance and small-signal stability are discussed in this paper. This method has a simple control structure and satisfactory power control performance, which greatly improves reliability, and flexibility and reduces costs. Finally, the feasibility and effectiveness of the proposed control strategy are verified.