Input filter design for multiple-module DC power systems

When multiple DC-DC converters are operated from a DC bus with a nonzero source impedance, the possibility exists for undesirable interactions between each 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 the entire system operates reliably. Proper filter design decouples 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 improves the performance of the individual regulators. A specific example, the buck current mode controlled converter, is examined in detail. Extensive experimental evidence is presented to verify the analytical results