A Control Method for Flexible Transfer Converter to Enable Autonomous Control of AC Microgrids

For grid-connected or interconnected microgrids, the transition to an autonomous and decentralized architecture was hampered by two perplexing issues: how to guarantee voltage supporting capacity while fully and controllably utilizing local power generation, and how to switch between islanded and grid-connected modes flexibly and efficiently. Through a combination the benefits of interlinking converter and switch, flexible transfer converters (FTCs), positioned at the interfaces between the utility grid and microgrids, are offered as a solution in this study. This paper proposes a control method for FTC and a universal control strategy for distributed generations, which contribute to proper power flow and flexible mode transfer in a communication-free design. They are convenient to control, easy to install based on existing assets, and hence promising in distributed microgrid applications. Also, an FTC for grid-connected microgrid system is analyzed and designed through small-signal modeling. Finally, comprehensive case studies in simulations and experiments are provided to validate its effectiveness.