LCL filter design for grid-connected voltage-source converters in high power systems

This paper deals with an LCL filter for the grid-connected converter. Active and passive damping methods are compared in a resonance suppression point of view and necessity of the passive damping is claimed, especially for high power systems in which switching frequency is limited lower than 2.5 kHz. Based on the analysis, LCL filter design procedure with passive damping for a two level voltage source converter is introduced. The filter components are optimally selected by investigating stored total energy in the filter and capacity of the converter. Then the resistors are inserted at several locations and comparisons are made to determine the most proper way of passive damping by examining the losses. The effectiveness of the study is supported by simulation and laboratory scale experiment.