In distributed photovoltaic(PV)generation systems

PV cells are in general connected to downstream power stage through interfacing DC-DC converters to fulfill maximum power point tracking(MPPT).Due to inherent current-source nature of the PV cell

the input voltage controlled PV-interfacing MPPT converter will become a current-fed(CF)converter which shows distinct dynamic features from those of the usual voltage-fed(VF)converters.In this regard

taking the Boost converter with an input capacitor as the case of study

this paper aims to investigate frequency responses of the CF MPPT converter.Firstly

small-signal models of the control system under both open-loop and input voltage controlled closed-loop are derived

and then the influences of load type on the system frequency responses are revealed.Secondly

the terminal impedances of the MPPT converter are modeled and analyzed

and the important factors affect the closed-loop input and output impedances are pointed out

which will provide theoretical guide for future stability design of the interfacing circuit.Finally

a laboratory prototype is built

and the analyses are verified by test results in both time-and frequency-domains.