Virtual flux has the advantages of simple calculation and easy to digital operation, which has attracted much attention in the application of alternating measurement. But due to the defect of the calculation, the directcurrent bias and the integrator saturation phenomenon caused by the integration of the grid voltage are seriously affecting the space vector orientation. In the process of the voltage measurement, the control method is added to the virtual flux technology. A virtual flux observer is designed, which is used to replace the traditional PhraseLock technology. The directcurrent bias and the initial integration error are effectively eliminated. Besides, the virtual flux optimization algorithm is derived, and the extended Kalman filtering in imitation system is used to imitate the sampling voltage. The method can effectively reduce the harmonic distortion and the time of single cycle control. The simulation of the observer and the algorithmic demonstration show that the observer optimized by algorithmic can eliminate the phenomenon of integral saturation, and the influence of directcurrent bias on the precision orientation, and improve the dynamic performance and control precision of the system.