The electric-drive-reutilized onboard charger (EDROC) system, which reuses the electric drive system to propel the motor winding, large-rated inverter device, and control circuit, can both implement charging and electric drive and has significant advantages in cost, power level, and power density. In this paper, virtual synchronous machine (VSM) control is introduced to address the issue of instability of three-phase AC interface under the condition of power network fluctuation, which ensures the safe and stable operation of EDROC system. Firstly, the circuit topology and basic working principle of the six-phase EDROC are introduced. Secondly, the torque generation component of the fundamental plane is mapped to the x-y harmonic subplane using the multi-control degrees of freedom of the six-phase motor, achieving no electromagnetic torque during charging. Then, a mathematical model of VSM control is established for the three-phase AC/DC interface to simulate synchronous motor operation. Finally, a prototype is built and tested. The result is that the total harmonic distortion (THD) is 2.91%, which meets the national standard and the system can make corresponding adjustments to the frequency change in time. The results show that the proposed method has ideal power adjustment and zero electromagnetic torque performance under the condition of frequency fluctuation.