Research on size reduction of magnetic components in grid-connected converters

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Dadkhah, Jalal
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The rapid pace of electrification and adoption of renewable energy sources necessitate the development of efficient, cost-effective, and compact power electronic converters. Among the essential components in modern converters, magnetic components play a crucial role, with their size and quantity varying depending on the application, power rating, and converter topology. Reducing the size and number of magnetic components lead to higher converter efficiency, lower cost, and higher power density. This thesis presents two distinct methods for reducing the size and quantity of magnetic components in single-phase and three-phase grid-connected converters. In single-phase converters, an innovative interleaving method is proposed, which effectively increases the power rating of a commercial Gallium Nitride (GaN)-based Power Factor Correction (PFC) converter. The proposed interleaving method along with GaN transistor and an advanced controller operating in Discontinuous Conduction Mode (DCM) lead to substantial inductor size reduction in the PFC converter and Electromagnetic Interference (EMI) filter. For three-phase converters, a novel set of topologies known as "reconfigurable filter" is introduced, minimizing the number of magnetic components. These reconfigurable filters construct LCL filters using only three inductors, a notable reduction compared to the conventional LCL filters requiring six inductors. The key components of the reconfigurable filters are a set of low-frequency bidirectional switches which lead to full utilization of existing magnetic components by changing their roles from the grid side to the converter side. The proposed topologies achieve comparable Total Harmonic Distortion (THD) performance compared to conventional LCL filters while utilizing three fewer inductors. Additionally, the reconfigurable filters suppress leakage current and offer reactive power support, making them versatile for diverse applications. The proposed topologies are applied in two different applications including PFC converters and Photovoltaic (PV) inverters. All proposed solutions are characterized through equivalent circuits and mathematical models, accompanied by practical design guidelines. To validate the proposed methods and topologies, experimental prototypes are constructed and rigorously tested, yielding promising results. Detailed comparisons highlight the significant advancements achieved through the proposed solutions.
Magnetic component, Photovoltaic, Power factor correction, PFC, Inverter, Gallium Nitride, GaN, Power electronic