A fundamental challenge in modern power systems is enabling inverters to operate flexibly across different grid conditions while maintaining stability. Traditional approaches require discrete switching between grid-forming (GFM) and grid-following (GFL) control modes, which can create operational discontinuities and limit grid resilience.
Researchers have now proposed a unified control framework that eliminates the need for discrete mode switching by integrating dispatchable virtual oscillator control with reference-following synchronization. The approach supports five distinct operating modes—voltage and frequency following (PQ mode), voltage-forming with frequency-following (PV mode), voltage-following with frequency-forming (Qf mode), voltage and frequency forming (Vf mode), and a hybrid mode combining GFM and GFL characteristics.
The key innovation lies in achieving smooth transitions between these modes through continuous adjustment of a small set of control parameters rather than abrupt controller reconfiguration. This eliminates pre-synchronization delays and maintains stability during mode transitions—a critical requirement for grid stability during dynamic events.
The framework provides several advantages for grid operators and renewable energy integrators. It offers physically interpretable control that adapts inverter dynamics to real-time grid requirements, enabling faster frequency response during disturbances and improved voltage support. The flexibility to operate in hybrid modes allows inverters to contribute grid-forming characteristics when needed while reverting to grid-following operation during normal conditions.
Validation included comprehensive electromagnetic transient simulations and hardware-in-the-loop experiments, demonstrating robust performance across various operating scenarios. Small-signal stability analysis confirmed the framework's effectiveness under different control parameter settings.
This development has significant implications for grid modernization. As renewable energy penetration increases, the ability to seamlessly transition between control modes without discontinuities becomes essential for maintaining system stability. The framework could enable more efficient integration of distributed energy resources and reduce the need for specialized high-capacity grid-forming resources, potentially lowering system costs while improving resilience.
