Small-Signal Modeling and Experimental Verification of PV-Interfacing MPPT Converter Under Different Load Conditions
LIU Su-cheng1, TANG Yun-ze1, LIU Xiao-dong1, LI Qing-qing2
1. School of Electrical and Information Engineering, Anhui University of Technology, Ma'anshan, Anhui 243002, China;
2. Nanjing ZG Power Supply CO, LTD, Nangjing, Jiangsu 211100, China
Abstract: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.
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