Robust loop-shaping H∞ control of LCL-connected grid converters

This paper proposes the use of a robust loop-shaping H_∞ procedure for the current control loop of VSCs connected to the grid through LCL filters. The proposed method yields robust controllers for systems connected to grids whose equivalent impedance is only known in a predefined range. The design procedure is based on simplified classical loop-shaping principles. The result is a discrete-time controller, suitable for being executed on a Digital Signal Processor and executable in real-time that is robust for the considered conditions. The procedure has been verified by simulation and experimental testing.