Magnetic Integration of LCL Filters

An LCL filter has two individual inductors. In order to reduce the volume of magnetic components, magnetic integration of these two inductors is introduced in this chapter. First, the integration method of the two inductors of an LCL filter is proposed, and the magnetic circuit model of integrated inductors is built. Then, based on this model, the coupling caused by the nonzero reluctance of the common core is analyzed, and the coupling effect on the ability of attenuating high-frequency harmonics of LCL filter is evaluated. According to the harmonic limits of the grid current, the maximum allowable coupling coefficient is derived, which provides the guidelines for selecting cross-sectional area and magnetic material of the common core. Finally, with the help of Ansoft Maxwell software, design examples of integrated magnetics for both single-phase and three-phase LCL filters are presented, and experiments are performed to verify the proposed method.

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