Analysis of Power Coupling Characteristics and Decoupling Control Strategy for GFC Under Active Frequency and Voltage Support

Renewable energy is integrated into the grid through a grid-forming converter (GFC). The GFC can emulate synchronous generator (SG) characteristics. It can improve the stability and reliability of renewable power systems. However, the GFC has inherent coupling paths in its control structure. The mutual interaction between active and reactive power control loops is especially significant. It limits the power output of the GFC. It also limits the transient voltage support capability for the grid. Therefore, this paper first analyzes the effects of the active power control loop and the reactive power control loop on the power coupling characteristics of the GFC. A mathematical representation model is established. Second, this paper considers the active transient voltage support target of the GFC for the grid under large disturbance conditions. A power decoupling control strategy is proposed. It uses an improved power loop based on adaptive reactive power compensation (ARC). The equivalent active power difference and voltage deviation adaptively adjust the coefficient DqF. This coefficient dynamically adjusts the reactive loop gain. Then transient voltage support and power decoupling are achieved. Finally, simulations and experiments verify the correctness of the proposed strategy.