Electromagnetic Integration of Decoupled <i>LCL</i>-Filter for Grid-Tied Converters With FMLF Technique
Panbao Wang, Shiqi Jiang, Wei Wei, Wei Wang, Dianguo Xu
Abstract
<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -type filters, compared to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> - or <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -type filters, are preferred in grid-tied converters due to their better capability of harmonic suppression. Although <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -filters have the potential to reduce the total size and weight of the converter, but dispersion of the system is raised owing to the more discrete components, which is adverse to the compact design of the converter. To address this issue, in this work, an electromagnetic integration method of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> -filter is proposed using flexible multilayer foil (FMLF) technique. Based on the investigation of a common FMLF-winding, the terminal-configuration to realize the two-port circuit of an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -integration-unit is got. Following this, an electromagnetic integration unit that composed of an EE-type core and two FMLF-windings is derived for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter. In this design, the FMLF-windings are wound on the side-legs of EE-core with appropriate terminal-configurations. Each winding is equivalent to an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> -unit, and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filtering circuit is achieved through the cascade connection of the two windings. Moreover, by setting air-gaps in both side-legs, magnetic coupling between the two windings can be degraded for mitigating its negative influence on filtering performance. According to the modeling and theoretical analysis, prototypes of the proposed, discrete, and magnetically integrated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filters have been built for a 500-W SiC-MOSFET inverter, contrastive experiments have been conducted to demonstrate the feasibility and superiority of the proposed approach.