Interacting bifurcation phenomenon in three-phase voltage source converter connected to non-ideal power grid

Three-phase voltage source converters are commonly used to convert ac power from a three-phase grid to a regulated dc voltage with controlled unity input power factor. However, the non-ideal power grid may drive the converter to enter a low-frequency instability region. As a result of the emergence of low-frequency oscillation, the stability boundary leading to a catastrophic bifurcation shrinks dramatically. Simulation results show the interaction of the low-frequency oscillation and the catastrophic bifurcation. Analytical calculations based on harmonic balance are adopted to show how the stability margin is affected.