Research on VSG Control of Three-Phase Four-Leg Power Conversion System Considering Power Oscillation Suppression under Unbalanced Fault

In this paper, we explore the challenges associated with power oscillation and active support in four-leg inverters during unbalanced fault conditions. To address these issues, we propose a Virtual Synchronous Generator (VSG) control strategy specifically designed to suppress power oscillations while providing active support to the grid. The key innovation of this strategy lies in the control of zero-sequence current, which plays a crucial role in ensuring that power oscillations are effectively mitigated. Simultaneously, the strategy guarantees that the output current from the four-leg inverter does not exceed safety thresholds, thereby protecting the system from potential damage. Furthermore, when an unbalanced fault occurs within the power grid, leading to frequency disturbances, the proposed Automatic Generation Control (AGC) function is activated. This function ensures the continued suppression of power oscillations even amidst these disruptions. The effectiveness of our proposed control strategy has been thoroughly validated through comprehensive simulations, demonstrating its potential for real-world applications in enhancing grid stability.