Comparative study of bifurcation boundry in parallel-connected buck converters under democratic current-sharing control

This paper studies the effects of the presence of a current-sharing loop in a system of parallel-connected dc/dc buck converters under democratic current-sharing control. Under this control scheme, the reference current is generated by a typical proportional- integral (PI) controller for voltage regulation and the currents in individual converters are programmed by a built-in interleaving switching control. Comparisons are made for the configurations without and with the current-sharing loop. Generally, we find that the current-sharing loop is helpful in widening the stability range even though it increases the complexity of the system. Simulations are performed to capture the Hopf bifurcation boundary which is the first instability boundary of practical importance. Unlike those in some previous studies which use abstract system parameters, the results in this paper are presented in terms of practical parameters and hence can be directly used for comparison of operating ranges for practical parallel-connected converters.