IAHO: Integrated Andronov-Hopf oscillator for providing ancillary services with single-phase grid-forming inverters

• Unified AHO control integrates inertia, damping, and voltage-independent droop. • Proposed IAHO improves RoCoF, frequency nadir, and active-power dynamics. • Voltage-independent droop ensures accurate power support during disturbances. • IAHO provides superior transient stability under severe grid-voltage sags. • Experimental 2.5 kVA tests validate analytical and stability improvements. The increasing deployment of renewable energy sources is reducing system inertia and challenging grid stability. Meanwhile, the growing penetration of grid-forming(GFM) inverters offers opportunities to enhance frequency and voltage support. Among GFM techniques, virtual oscillator control (VOC) has emerged as a promising approach due to its superior dynamic performance, yet existing VOC strategies exhibit limitations in inertia emulation, damping, and droop accuracy. This paper proposes a control strategy based on the integrated Andronov–Hopf oscillator (IAHO) that, for the first time, unifies virtual inertia, enhanced damping, and voltage-independent droop control into a single framework. A comprehensive small-signal analysis is conducted to design the damping controllers, while a large-signal analysis evaluates transient stability under severe grid disturbances. Theoretical insights are experimentally validated on a 2.5 kVA single-phase inverter. Results demonstrate that the proposed IAHO delivers a lower rate of change of frequency (RoCoF), higher frequency nadir, well-damped power dynamics, and enhanced active power support compared to conventional VOC-based strategies. Moreover, the IAHO ensures positive reactive power droop during voltage sags, providing superior transient stability.