High Power Density Three-Phase Shunt Active Power Filter Design Based on Multiple Magnetic Integrations of LCL Filter

The LCL filter has been widely used in inverter design due to its excellent attenuation capability for the switching harmonics. Nevertheless, the large cost associated with the conventional three-phase LCL filter has limited its usage. This paper proposes a multiple magnetic integration strategy of the LCL filter to reduce the cost while increasing power density. In the new design, an EIE-type magnetic core is put forward for the single-phase LCL filter, where the magnetic fluxes generated by the two discrete inductors cancel out mostly and the residual flux is mainly related to the small capacitor branch current. The magnetic integration is then extended to three-phase by adopting the three-phase three-limb core. Due to the coupling among phases, the equivalent inductance is much larger than the self-inductance such that the self-inductance can be reduced dramatically. An experimental prototype is developed which demonstrates the validity of the proposed method.