Robust Power Decoupling Based on Feedforward Decoupling and Extended State Observers for Virtual Synchronous Generator in Weak Grid

Virtual synchronous generator (VSG) can provide inertia support for a more renewable-energy-integrated power system. However, there are power couplings between active power and reactive power in a weak grid. To solve this issue, the dynamic models of active power and reactive power are established first to better reflect the characteristics of power coupling. Then, the feedforward decoupling method using virtual power angle and virtual voltage is designed under the nominal system, which can suppress the power couplings well. Furthermore, considering the variation of line impedance, a power decoupling strategy based on extended state observers (ESOs) is proposed, which can estimate the power couplings as the internal disturbances of the system and output compensations for the feedforward decoupling method. Consequently, the robustness of the proposed strategy is improved greatly, and good decoupling performance can be achieved under different line impedance conditions. Finally, the effectiveness of the proposed method is verified by both simulation and experimental results.