An LCL-LC power filter for grid-tied inverter

This paper presents a new topology of higher order power filter for grid-tied voltage-source inverters, named the LCL-LC filter, which inserts an extra capacitor connected in parallel to the Lf-Cf series resonant circuit of LLCL filter Particularly, it can strongly attenuate the harmonic currents around the switching frequency, and the attenuation rate become -60dB at high frequency which leading to a decrease in the total inductance and volume of the filter. The parameters design criteria of the proposed LCL-LC filter is also introduced. The comparative analysis and discussions regarding the traditional LCL filter, LLCL filter and the proposed LCL-LC filter have been presented and evaluated through simulation on a 5-kW-single-phase grid-tied inverter prototype.