A New Topology of Higher Order Power Filter for Single-Phase Grid-Tied Voltage-Source Inverters

In order to reduce the influence of the grid harmonic currents and voltages, harmonic compensation is regularly implemented for a grid-tied inverter. In this study, a new topology of a higher order power filter for single-phase grid-tied voltage-source inverters, named L(LCL)
₂
, is presented. The subscript is added to the name to prevent confusion with the LLCL filter. In the proposed design, the inverter side inductance is divided into three parts, and the grid side inductor is removed. Also, an additional resonant branch at the double of the switching frequency is added to the traditional LLCL filter to attenuate high-frequency harmonics. The overall inductance of the recommended filter is smaller than the LLCL filter. A comparative study and discussions on the subject of the traditional LLCL filter and the proposed L(LCL)
₂
filter have been conducted and assessed through an experimental hardware implementation on a 700 W, 120 V/60 Hz single-phase grid-tied inverter. Furthermore, a straightforward engineering design benchmark is suggested to discover parameters of the L(LCL)
₂
filter. Moreover, stability analysis, loss analysis and an optimization of the L(LCL)
₂
filter parameters have been conducted in this study. The analysis shows that in comparison with the LLCL filter, the L(LCL)
₂
filter not only has lower voltage drop and less total inductor size, but also has improved performance in decreasing high-order current harmonics.