Analysis and Suppression of the Beat Frequency Oscillation in Buck-Derived Front-End Cascaded Power Supply System

In cascaded DC power supply systems, if the switching frequency of the source converter differs from the load converter, the interaction between the two converters would cause the beat frequency oscillation in the output of the system. In terms of the cascaded power supply system with buck-derived frontend dc-dc converter, this paper has a detailed analysis of its generating mechanism of the beat frequency oscillation and then we proposed the bus current feed-forward control method to suppress the oscillation. By simplification, we finally get a simple and easy-to-be-realized expression of the feed forward transfer function as well as its practical circuit. Since the transfer function is irrelevant to the parameters of load converters, this method has well adaptive ability to the load converters. Finally, the correctness of the theory is verified by simulation.