Analysis of the grid side behavior of a LCL-filter based three-phase active rectifier

Three-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue or if there are other loads connected to the same point of common coupling (PCC), and sensitive to the harmonics produced by the switching of the converter, an LCL-filter has to be used. This kind of solution has been studied in theory but its sensitivity to the values of the LCL-filter passive elements employed, to the grid side stiffness and to the parameters of the controller has never been detailed. In this paper the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach. A "virtual circuit" is synthesized in role of the digital controller and of the feedback filters to have a homogenous model that allows a sensitivity analysis, which is rigorous and straightforward for the industry.