Virtual Impedance Control for Enhanced Current Limitation in Grid-Forming Inverters

Grid-forming inverters (GFM) are a promising solution for increasing renewable energy penetration in power system networks. Adapting to dynamic changes in grid conditions, ensuring coordination with other inverters, and tuning and calibrating current-limiting parameters are crucial issues in GFM-based systems. GFM-based systems must ensure fault current contribution, current magnitude limitation, and fault recovery capability to support the grid and protect power semiconductor devices under strict disturbances. Various methods are described in the literature to limit the current, i.e., virtual impedance, current limiters, and voltage limiters. This paper suggests a virtual impedance-based approach that adjusts the internal induced voltage to maintain system synchronization and track system voltage changes. The technique inhibits phase angle change by regulating the current and avoids grid instabilities. The paper addresses challenges like temporary transient overcurrent and current saturation. Simulations are conducted to demonstrate performance. Results ensure the control scheme's robustness and reliability.