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Transition between grid-connected mode and islanded mode in VSI-fed microgrids


This paper investigates the behaviour of a microgrid system during transition between grid-connected mode and islanded mode of operation. During the grid-connected mode the microgrid sources will be controlled to provide constant real and reactive power injection. During the islanded mode the sources will be controlled to provide constant voltage and frequency operation. Special control schemes are needed to ensure proper transition from constant PQ mode to constant fV mode and vice versa. Transition from one mode to other will introduce severe transients in the system. Two kinds of transition schemes based on the status of the off-line controller are discussed and a comparative study is presented for various step changes in the load. An additional-pole-placement-based output feedback controller augmentation during transition between the modes is proposed to reduce the transients. A static output feedback compensator design is proposed for the grid connected to island mode transition and a dynamic output feedback compensator design is proposed for resynchronisation. The performance of the output feedback controllers is tested under various operating conditions and found to be satisfactory for the tested conditions.

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This work was supported by CPRI, Ministry of Power, Government of India, within the framework of the project Power Conversion, Control and Protection Technologies for Micro-Grid.

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Correspondence to Dibakar Das.

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Das, D., Gurrala, G. & Shenoy, U.J. Transition between grid-connected mode and islanded mode in VSI-fed microgrids. Sādhanā 42, 1239–1250 (2017).

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  • Distributed generation
  • dq axis current control
  • droop control
  • output feedback controller