This paper proposes a novel control theory and architecture based on a microgrid central controller (MGCC) and single-loop grid-forming inverters to address two key challenges: the voltage surge induced during grid-connected to islanded transitions

and the difficulty in achieving stable parallel operation among multiple islanded microgrids for lateral power support. Firstly

a mathematical model of voltage dynamics during the transition process is established. The relationship between voltage phasors and synchronized switching operations during the transition and parallel operation is analyzed. Based on the inherent physical characteristics and operational principles of grid-forming inverters

the proposed architecture is explained

and its rationality is justified. The MGCC is implemented using an embedded chip

and hardware-in-the-loop(HIL) simulations are conducted on a real-time digital simulation(RTDS) platform. Experimental results confirm that the proposed architecture can effectively manage grid-to-island transitions and flexible grid connection

while it also exhibits advantages in voltage stabilization and parallel operation stability over existing architectures.