System Strength Supported Flexible Converter (I): Transient Current Safety and Electromagnetic Transient Verification

The insufficient overcurrent capability of power electronic devices is one of the key factors restricting the application of grid-forming (GFM) voltage source converter(VSC). Ensuring the transient safety of VSCs while maintaining their voltage support capability under current limiting constraints remains an outstanding issue. Therefore, this paper proposes a new control framework based on potential vector remolding (PVR) for a system strength supported flexible converter(SSS FC). The proposed method focuses on analyzing the transient overcurrent mechanism of SSS FC. It introduces a novel approach for transient current suppression through PVR control. This approach limits the current by directly modifying the internal potential of power synchronization control constraints using the voltage vector at the grid-connected port of the converter. The method includes the starting criterion, amplitude-phase compensation calculation, and phase-separated virtual coordinate construction. By utilizing theoretical models of voltage vector trajectory and transient current in the time domain, the effectiveness of amplitude-phase compensation to improve the transient characteristics of SSS FC is analyzed. Finally, electromagnetic transient simulation results show the effectiveness of the proposed method in ensuring the safety of SSS FC under various types of symmetrical and asymmetric grid faults.