Enhanced Power Decoupling Strategy for VSG With Power Control Based on Virtual Power Angle

The adoption of virtual synchronous machines can enhance the system inertia of a "double high" power grid. However, the strong reactive power coupling inherent in the virtual synchronous machines can introduce power steady-state errors, significantly restricting the power transmission capacity of the converter, and potentially leading to system instability. Therefore, this paper conducts a detailed analysis of the power coupling mechanism of the VSG, and identifies the line impedance ratio (R/X) and phase angle (θ) as the two major factors that affect power coupling. The impact of the power coupling on stability is evaluated in this paper. Then, based on the virtual inductance control, a power control strategy based on virtual power angle is proposed, which takes into account both R/X and θ. The virtual power angle value is calculated using theoretical formulas for power loop reshaping, which can eliminate power coupling in multiple scenarios of the VSG, suppress reactive power fluctuations, and evaluate the stability of the system using the amplitude-phase motion equation criterion. Finally, the effectiveness of the proposed decoupling control strategy is validated through theoretical analysis and experimental results.