Input filter design for multiple-module DC power systems

When multiple DC/DC power converters are operated from a DC bus with a nonzero source impedance, undesirable interactions can occur between an individual regulator and the input impedance of the other regulators on the bus. Consequently, criteria for input filter design in the presence of a significant source impedance are developed, which, when used in conjunction with already-known input filter criteria, permit the input filter to be designed so that each regulator operates reliably. Proper filter design tends to decouple the negative regulator impedances from the bus, leaving only the passive input filter impedances to affect the other converters. These filter impedances appear in parallel with the source impedance and reduce the overall source impedance. Hence, the use of multiple modules on the same bus actually improves the performance of the individual regulators. An example, the buck current mode controlled power converter, is examined in detail. Extensive experimental evidence is presented to verify the analytical results.