Improved LCL Filter Design Procedure for Grid-Connected Voltage-Source Inverter System

rid-connected voltage-source inverters (VSI) have evolved in the past years for the interconnection of renewable energy sources with the grid to satisfy the increased electrical load demand and to utilize the use of clean, carbon-free energy. However, VSIs suffer from a major drawback of switching harmonics caused by the inverter switches. To reduce the amount of current distortion injected into the utility grid and meet harmonic constraints as defined by power quality standards, an LCL filter is often used. Although there is an extensive amount of literature describing the design procedures of an LCL filter, all these methods cannot guarantee an optimal solution because no direct mathematical function between LCL filter parameters and total harmonic distortion (THD) exists. This paper proposes an improved LCL filter design procedure for a grid-connected voltage-source inverter system. The THD of the current entering the utility grid for various LCL filter parameter combinations is generated through computational iterations. Using this data, the goal is to choose LCL filter parameters with less overall inductance value and lower manufacturing cost, while maintaining the same performance level compared to the conventional design procedure. The performance of the proposed procedure is verified by a case study, with simulation and experimental results, in which a 40 % reduction in overall inductance was achieved.