Design of LCL Filter for Micro Inverter

Thepresence of Distributed Resources (DR) and the subject of Distributed Generation (DG) are rapidly growing in modern distribution networks. Many of these resources use renewable energies, and many of them provide electrical energy in the form of dc voltage source. Consequently, the connection of such resources to the utility grid needs a dc/ac conversion stage. Voltage Source Converters (VSC) are widely used for this application as they have a mature technology. These converters are usually connected to the utility grid through a simple L filter to reduce the current harmonics injected to the grid. However, higher order filters, like LCL filters, can provide better harmonic attenuation and reduce the filter size at the same time. This paper proposes a method for LCL type filter design, which makes the task very convenient. Step-by-step design procedure is described as a design example, which is verified by simulation.