不同负载条件下光伏接口MPPT变换器的小信号建模及实验验证

在分布式光伏发电系统中，光伏电池一般通过DC-DC变换器与后级相连，以实现输出最大功率跟踪（MPPT）.由于光伏电池的本质电流源特性，使得输入电压反馈控制光伏接口MPPT变换器为电流源变换器，会呈现出与常见电压源变换器截然不同的动态特性.以前置电容Boost变换器为研究对象，重点探讨电流源MPPT变换器的频率响应特性.首先，建立了开环和输入电压闭环两种控制方式下系统的小信号模型，并揭示不同负载类型对于系统频率响应的影响；其次，对MPPT变换器的端口阻抗进行了建模分析，指出影响闭环输入、输出阻抗特性的重要因素，为接口电路的后续稳定性设计提供理论指导；最后，搭建实验室电路样机，通过频域和时域测试结果验证了理论分析的正确性.

Small-Signal Modeling and Experimental Verification of PV-Interfacing MPPT Converter Under Different Load Conditions

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.