Novel Design Algorithm for LCL Grid Filters Including Consideration of Arbitrary Grid Codes

For the connection of voltage source converters (VSC) to the low voltage grip, in addition to feasibility requirements, grid codes have to be met. Although the conditions differ depending on the area of application, the rated power or divergent regional standards, they typically specify limits regarding harmonics of the grid current. These limits are usually met by suitable passive filters. The most simple one would be a line choke, which is easy to dimension, but tend to be bulky, costly and inefficient. Higher order filters, e.g. of LCL-type, often perform better. Their design requires much more effort. Besides the harmonic attenuation, the placement of the inevitable resonances and their damping are a critical part of the process. Cost, volume, weight and losses also play an important role in optimization. Some of these properties lead to contradictions in the outcome of the design process. Although various methods for designing LCL filters have been published, filter design still is a laborious task, especially if the design is done by hand. This paper presents a design routine, which can entirely be implemented in software, generating a solution for an economic filter meeting an arbitrary grid code in a given environment. An exemplary filter is designed and analyzed regarding its performance. It is then compared to LCL filters designed with an established design method.