An Enhanced Inertial Droop Control for Minimal Sensitivity of Grid-Forming Inverter Interface to Dynamic Grid Conditions

This paper proposes a control framework for a gridforming (GFM) voltage source converter (VSC) to ensure resilient dynamic grid interface. The proposed control architecture is a modified version of the existing inertial droop control intended to regulate the voltage at the VSC terminal instead of at the point of common coupling (PCC). The study commences with a detailed analysis of the structure of the proposed controller compared to the conventional inertial droop control method. The full-order time-averaged linearized GFM VSC test system models are then constructed. Eigenvalue analysis is employed to investigate the instability of VSC incorporating conventional controllers for higher grid strengths. It is observed that the performance of this controller further deteriorates in the presence of power coupling challenges. Subsequently, the small-signal stability analysis of the linearized system with the proposed controller is conducted, showing its effectiveness in stabilizing the VSC even in strong grids with significant coupling. Eigenvalue sensitivities to variations in grid parameters are found to be negligible. The analytical conclusions are corroborated through numerical simulation results. Experimental findings from the power-hardware-in-the-loop (PHIL) setup further substantiate the efficiency of the proposed over the prevalent GFM power controller in mitigating challenges of varying grid stiffness and coupling.