Limit Induced Bifurcation of Grid-Connected VSC Caused by Current Limit

This letter demonstrates a new instability scenario of grid-connected voltage source converter (VSC) - limit induced bifurcation (LIB) caused by the current reference limit from the outer control loop. When the current reference reaches limit, the control structure of the VSC and the equations of the system switch. The outer control loop is actually removed from the equations. The eigenvalues of the system change as well. When the current limit exceeds a critical value, the system may immediately become oscillatorily unstable when encountering the limit and LIB occurs. Eigenvalue analysis is conducted and time-domain simulation is utilized to verify the results.