PLL-Reinforced Damping for Interoperability Enhancement of Independently Designed Grid-Forming Wind Turbines in Weak Grids

Abstract. Interoperability of grid-forming (GFM) converters is crucial for the stability and efficiency of modern power systems, particularly when two independently designed GFM converters with different control architectures are connected to a common weak AC network. In this context, the interoperability of such GFM-based generation sources is examined in this paper in terms of power and frequency oscillations during both steady-state and transient cases. Based on this analysis, a novel method of oscillation mitigation via frequency-power reference (ω − P^*) droop-based feedback control in the power control loops is proposed. This method significantly improves the interoperability of grid-connected GFM converters during both steady-state and fault conditions. Furthermore, due to the generality of the control structures, the proposed method benefits different applications irrespective of the generation sources, such as offshore wind power plants (OF WPPs), GFM-HVDC converters, and battery energy storage systems (BESS). Additionally, the proposed method could reinforce standard power controller designs, such as virtual synchronous machines (VSM) or PI-controller-based power control loops.