Comparison of Voltage Sag Generators for Wind Power System

Low voltage ride through (LVRT) capability is required by new power system operating codes, then voltage sag generator (VSG) is generally used to simulate different voltage sag faults. The work principles of transformer and bidirectional switches based VSG and full-power converter based VSG are explained and discussed, the former can choose relay, thyristor or IGBT as bidirectional switches, and the comparison research of several VSG solutions is carried out by analysis and experiment. The experiment results make out that the full-power converter based VSG is powerful but its control is complex; the transformer and bidirectional switches based VSG has simple structure and high reliability, can simulate various types of voltage sag faults, and the voltage transition between normal and fault operation is smooth, then provide favorable conditions to verify the LVRT capability of wind power system.