A seamless transfer strategy based on indirect current control and droop control

The distributed generation (DG) should supply continuous power to local critical load, even in the condition of utility outage. This paper proposes a novel seamless transfer control strategy, which combines indirect current control and droop control. A microgrid structure of multi-masters and multi-slaves is also proposed, which based on the master-slave control and droop control. The master DGs are controlled by the novel control strategy and the slave DGs are controlled as conventional current sources based on PQ control. The advantages of this proposed strategy and microgrid structure are as follows. Firstly, the quality of critical load voltage can be maintained when utility outage occurs, Secondly, the reliability of microgrid in islanding mode can be improved because of the existence of multiple master DGs. The simulation results are provided to verify the effectiveness of this proposed control method.