Stability and Resynchronization of Current-Constrained VOC-Based GFM Inverters Through Revisiting Traditional Power System Criteria

As inverter-based resources and renewable energy systems continue to increase their penetration in modern power grids, maintaining system stability has become a critical challenge. To address this challenge, advanced control strategies are required for grid-forming (GFM) inverters that can operate reliably. This paper proposes a control strategy for grid-forming (GFM) inverters based on Virtual Oscillator Control (VOC), a novel approach grounded in power electronics and nonlinear dynamics. A key contribution of this work is the revisiting and employment of classical power system analysis techniques, such as the Equal Area Criterion (EAC) and synchronization-based stability evaluation, to derive stability criteria for VOC-based grid-forming (GFM) inverters operating under current-limiting conditions. Through detailed time-domain simulations, the validity of the derived stability criteria is systematically verified, demonstrating their applicability to the transient behavior of current-constrained VOC inverters. Furthermore, the current-limiting control logic used in the simulations is validated through Controller Hardware-in-the-Loop (CHIL) testing with actual controller hardware, ensuring its practical feasibility in real-time environments. The findings establish that combining EAC-based classical analysis with VOC control strategies offers an effective and reliable framework for enhancing the resilience and stability of GFM inverters under fault conditions.