Transient Stability Analysis of Grid-Forming Converter in Current Limiting Mode Based on Hamiltonian Theory

Converters with grid-forming (GFM) control are actively involved in the establishment and regulation of grid voltage and frequency in modern power systems. However, the nonlinearity of the converter system complicates the transient stability analysis, especially considering the GFM converter employs current-limiting control, which increases the difficulty of analyzing the transient process during grid faults. In this paper, the transient stability of GFM converter is studied based on the Hamiltonian theory which alleviates the analytical difficulties caused by system nonlinearity, and the current-limiting switching process with its impact on stability of the GFM converter are especially analyzed. Firstly, the dynamic model of the GFM converter is constructed according to Hamiltonian theory, and the system energy function before and during the current-limiting mode is constructed. The process of current-limiting switching under different fault conditions is analyzed, considering the mapping relationship of the current-limiting switching process corresponding to the power angle characteristics. Then, the effects of different parameters on the system stability margin and grid strength are considered. Finally, the correctness and accuracy of the current-limiting process and stability margin analysis are verified using the MT6040 real-time simulator with StarSim-HIL.