An Efficient High-power-density Integrated Trap-LCL Filter for Inverters

Trap filters have been proved to increase the power density of the voltage-source converters. Using a trap filter in series with the well-known LCL filters can significantly decrease the required inductance to meet the grid requirements. This paper proposes a new integration method to magnetically couple the trap and converter-side inductances in an LCL structure. The trap winding does not carry the fundamental current component, which further reduces the filter volume and loss. The proposed approach also enables the use of multiple trap filters coupled on one magnetic core. The magnetic and electrical equivalent circuits of the proposed integrated filter are derived and the effectiveness of this method compared with the LCL filter and the conventional integration methods is shown using Ansys Maxwell simulations and experimental results for a 500W/110V grid-connected inverter.