Research and design of a dual buck micro grid-connected inverter using small signals

Abstract

Smart grids have spurred the development of small-scale photovoltaic power generation, with micro inverters becoming the preferred choice for such systems due to their advantages. However, existing micro inverters have limitations, such as straight-through bridge arms and low efficiency. In light of the experiences gained from previous micro grid-connected inverters, a dual Buck micro grid-connected inverter based on a small signal model is proposed. The front stage of this inverter comprises two flyback circuits, which are connected in parallel on the primary side of the voltage apparatus in order to ensure safe isolation. Furthermore, an RCS(The circuit consists of resistors, capacitors and switches) active clamp circuit is connected in parallel to the main switch of the front-stage flyback circuit, and the voltage total harmonic distortion(THD) of <3.0 %. The rear stage employs a dual buck circuit configuration, which offers a distinctive benefit in that it eliminates the necessity for straight-through bridge arms in comparison to a full-bridge circuit. Furthermore, a small-signal model is developed to facilitate the acquisition of current loop parameters. PLECS simulation software is employed to simulate the algorithm, compare the design parameters, and verify the accuracy of the design parameters. A 600 W prototype has been constructed for the purposes of data analysis, comparison and experimental validation. The efficiency of the proposed inverter is 97.2 %. This approach is valuable for the investigation and development of micro grid-connected inverters.