Design and implementation of a grid-connected solar micro-inverter using a single-stage galvanically isolated topology with integrated magnetics
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Solar panels have been steadily increasing in capacity and decreasing in cost over the past few years. Given this context, and other incentives designed to increase renewable energy penetration, residential solar adoption is becoming more economically attractive. The solar AC module stands out amongst alternative residential solar technologies, for better modularity, higher efficiency, and ease-of-use. The Micro-Inverter (MI) topology bundled with the AC module then becomes a key factor in the overall cost, safety, and capacity of the system. The Flyback (FB) MI topology is a popular choice, thanks to its low component count and enhanced safety, but as modern residential solar panels trend towards 400 W and up, non-interleaved FB MIs, typically rated around 200 W, must become interleaved. Conventional FB MI interleaving is High Frequency (HF) interleaving, which adds a potentially bulky magnetic device to the topology. This thesis proposes and tests the application of an alternate topology, called the Isolated Manitoba Inverter (ISOMBI). The ISOMBI uses integrated magnetic devices and Low Frequency (LF) interleaving, to match the power rating of HF-interleaved FB MIs, without the extra bulky component. ISOMBI operating principles and analyses are disclosed, and an experimental prototype is constructed to test its ability as a grid connected power generator. The results show near unity Power Factor (PF), acceptable DC current levels and promising Total Demand Distortion (TDD). Overall, these results indicate that the LF-interleaved ISOMBI can be considered as a viable alternative to the HF-interleaved FB MIs in AC modules.