Stabilization of Input Filter/DC-to-DC Converter

Thanks to the impedance criteria, details of an analytical method allowing the stability analysis of an electric system constituted by a resonant LfCf input filter connected to a controlled dc-to-dc buck converter is presented. The considered system is analyzed by using small-signal linearization around the operating point of the converter and presented in frequency domain. Based on the resonant LfCf input filter, three basic structures of passive damping input filters are investigated. It is shown that the stability problem can be avoided by forcing the magnitude of minor loop gain Z(m)(s) to be less than one. However, in some application of electric system, it is sometime impossible to change neither input filter structure nor any input filter components value so an active damping control technique for stabilize the cascade connection between the small damping LfCf input filter/dc-to-dc buck converter is proposed. The simulation results show the validation of the analysis.