In view of three-phase power unbalanced caused by the output power difference of each phases microsource of the modular multilevel converter half-bridge series microgrid (MMC-MG) operating in the islanded mode

a balance control method of inter-phase power is proposed. The MMC-MG topology and three inter-phase power dispatching modes are introduced. The system three-phase output power mathematical model is established

and the mechanism of the dc circulating current to realize the inter-phase power flow is described. A dc circulating current controller based on arm virtual voltage is designed. Its output signal is superimposed on each phase modulation indices as power balance control variable. According to the output power of each microsource and the load power

the inter-phase power regulation is distributed

and the regulation is compensated by the state of charge of the energy storage device. Simulation and experiments show that the proposed control strategy can achieve inter-phase power balance control

which has no effect on the output voltage and frequency of the system. Compared with general three-phase microgrid

MMC-MG can realise inter-phase power balance by its own circulating current control

without additional investment of power balance equipment.