On the effects of voltage loop in paralleled converters under master-slave current sharing

This paper studies the effects of the presence of voltage loops in parallel connected buck switching converters under master-slave current sharing scheme. The system employs a typical proportional-integral (PI) controller for regulation. Comparisons are made for the cases where the slave modules are controlled with and without a voltage loop. Generally, we find that the voltage loop in the slave is helpful in widening the stability range though it is theoretically redundant for the purpose of controlling the output voltage in the small-signal sense. Such a loop provides stable current reference for the slave modules. Effectively, each slave module is under current-mode control by virtue of the current sharing loop, making it a current source. Simulation results under different control configurations are presented to demonstrate the phenomenon.