An Output Current based Seamless Transfer Control Strategy for Three-phase Converter with Energy Storage in Micro-grid

Abstract

Micro-grid should go into intentional islanding operation to supply power for the local critical loads in the utility outage condition. Three-phase converter with energy storage in micro-grid is used to transfer between the islanding mode and the grid-tied mode seamlessly. This paper proposes a transfer strategy based on output current of the three-phase converter with energy storage in the micro-grid, which composes of an external inductor current loop, a grid voltage loop and an inner inductor current loop. The converter is regulated as a current source just by the inner inductor current loop in the grid-tied operation. Once islanding happens, a serious transient error may be generated between the output current and the reference current. The voltage loop is fixed by the limiter, then, the converter operates as a voltage source. The quality of load voltage can be guaranteed and the continuous power supply is realized. Additionally, the parameters design of the control strategy is analyzed, and the operation principle is proposed in detail. Finally, the control strategy is verified by the simulation result.