Research of seamless transfer control strategy of microgrid system

Microgrid has two typical working modes: grid-connected mode and islanded mode. The transfer between these two modes should be seamless. In a microgrid that uses master-slave strategy to avoid circumfluence in the islanded mode, to control the master converter´s voltage is to control the microgrid voltage. Considering this, the master converter in this paper works as a voltage-controlled inverter when the microgrid is disconnecting from the utility grid while working as a current-controlled rectifier when the microgrid is in the grid-connected mode. Besides, by gradually adjusting the master converter´s output voltage to equal that of the utility grid when the microgrid is going to connect the utility grid and by setting an appropriate initial phase of the converter voltage when the microgrid needs to work alone, the seamless transfers between these two modes are accomplished. Experiment has been done to validate the accuracy, rapidity and reliability of this strategy.