Design and comparison of full-size converters for large variable-speed wind turbines

The full-size converters for wind turbine systems can flexibly realize variable-speed control and meet power system operational requirements. The designs of two-level, three-level neutral point clamped and three-level flying capacitor converter as full-size back-to-back converters for large wind turbine system are discussed in this paper. The harmonic standard and power system operation requirements for the converters are considered. And SVPWM with the on-off control is proposed to suppress the neutral point potential or fly-capacitor voltage deviation and drift for the three-level converters. The simulation models made by Simulink and Matlab are used to verify the designs and analyze power losses of the converters. And the performance and costs of three types of the converters are compared.