Optimal Virtual Impedance-based Power Decoupling Control Strategy for Grid-Forming Inverter

Recently, as the proportion of power converter-based distributed energy resources (DERs) increases, grid-forming inverters (GFMIs) have been receiving a lot of attention to improve the stability of the power system. However, unlike grid-following inverters (GFLIs), GFMIs introduce unintended coupling phenomena in the power control loop, making control parameter design difficult and reducing stability and dynamic performance. To solve this problem, this paper proposes an optimal virtual impedance (VI)-based power decoupling control strategy. The proposed power decoupling control strategy simultaneously implements the optimal VI, obtained through small-signal analysis, and transient virtual resistance (TVR) to achieve steady-state power decoupling and ensure power oscillation damping to improve stability. Moreover, the proposed power decoupling control strategy is very practical, as the optimal VI value can be easily calculated mathematically online. Finally, the effectiveness of the proposed strategy is verified through hardware-in-the-loop (HIL) test results.