An integrated inverter for a single-phase single-stage grid-connected PV system based on Z-source

摘要

An integrated Z-source inverter for the single-phase single-stage grid-connected photovoltaic system is proposed in this paper.The inverter integrates three functional blocks including maximum-power-point-tracking,step-up/down DC-side voltage and output grid-connected current.According to the non-minimum-phase characteristic presented in DC-side and the functional demands of the system,two constant-frequency sliding-mode controllers with integral compensation are proposed to guarantee the system robustness.By using two controllers,the effects caused by the non-minimum-phase characteristic are mitigated.Under the circumstance of that the input voltage or the grid-connected current changes suddenly,the notches/protrusions following the over-shoot/ under-shoot of the DC-bus voltage are eliminated.The quality of grid-connected current is ensured.Also,a small-signal modelling method is employed to analyze the close-loop system.A 300W prototype is built in the laboratory.A solar-array simulator(SAS)is used to verify the systematic responses in the experiment.The correctness and validity of the inverter and proposed control algorithm are proved by simulation and experimental results.