Analysis and Design of Non-isolated LC Full-bridge Grid-connected Inverter

In the face of increasingly severe energy shortage and environmental protection pressure, countries around the world have continuously increased the proportion of clean energy supply, and distributed power generation technology has gradually become a hot research field. As a power conversion device, inverter is the key element of the grid-connected power generation system, and its reliable and high-efficient operation is an important area of research at present. This paper takes the non-isolated single-phase grid-connected system as the research object, analyzes the working principle of the grid-connected inverter, analyzes and designs the hardware parameters of the full-bridge grid-connected system including drive circuit, filter circuit, etc; on the basis of unipolar modulation, the inverter voltage-current control system design is carried out with the consideration of grid voltage feed-forward; Utilizing the rotating coordinate system, the PLL control design is carried out by adding signal filtering; through the frequency offset method (AFD), the offset angle is set to carry out the measurement and control of the islanding state. Combined with the dead time mechanism of action, the dead time effect is suppressed by constructing deadband compensation amount with the same polarity as the current to reduce the harmonic content of the output current. Based on the above program to build a grid-connected inverter prototype, measured inverter output waveforms with low harmonic content, frequency amplitude comply with the rules of grid-connected, the experiment proves the reasonableness, feasibility and effectiveness of the design program.