Abstract: This paper proposes an improved flux observer based on a series structure of a first order low-pass filter and a high pass filter to solve the DC offset problem of grid voltage sensorless strategy using the virtual flux algorithm, by utilizing this improved flux observer to derive the virtual flux, the precision of observation is enhanced. Based on the virtual flux obtained, a calculation structure of grid angular frequency is proposed using the idea of phase locked loop for different grid frequency operating conditions, and the grid voltage is reconstructed from the relationship between the virtual flux and voltage. In addition, the proposed grid voltage sensorless strategy is applied to the grid side converter system, and a virtual synchronous control structure is designed in a two-phase static coordinate system.Compared to a rotating coordinate system, the decoupling process of the control inner loop can be omitted, while the coordinate transformation process can be simplified, avoiding the instability factors caused by inaccurate angles in coordinate transformation.Finally, simulation and experiments verify the effectiveness and reliability of the proposed control strategy and flux observer.