Robust Power Decoupling Controller Design for Grid-Forming Inverters

Unlike grid-following inverters (GFLIs) that serve as current sources, grid-forming inverters (GFMIs) act as voltage sources, capable of providing voltage support and inertia support to the power grid. By controlling the magnitude and angle of voltage, it is possible to achieve active (P) and reactive (Q) power transmission along the line. However, conventional algorithm such as virtual synchronous generator (VSG) exhibits coupling between P and Q loops. To address this issue, this article first establishes dynamic models for active and reactive power, which indicate that coupling becomes severe when the grid impedance or the power angle increases. Subsequently, a hybrid control method based on active disturbance rejection control (ADRC) and H∞ control is proposed to decouple the P and Q loops in GFMIs. This strategy employs a data-driven H∞ controller as the inner loop for preliminary decoupling of the system, and uses ADRC control as the outer loop, with an extended state observer (ESO) to treat the undecoupled part as a disturbance for secondary decoupling of the system. As a result, the robustness of system decoupling is significantly enhanced. The decoupling performance of this controller has been verified through experiments, which demonstrates the effectiveness and superiority of this method.