Comparison of Two-level and Three-level Converters in Permanent Magnet Direct-drive Wind Power Generation System

Paralleled two-level converters are widely used in low-voltage permanent magnet direct-drive wind power generation systems,while three-level converters are more suitable in medium-voltage systems.The output performances and power losses are compared between two-level and three-level converters in permanent magnet direct-drive wind power generation systems.Loss models of power device and filtering inductance are established for evaluating the power losses of the converters.Based on the operating principle of two-level and three-level converters,a practical loss calculation method is derived.Simulation and experiment results show that,comparing with two-level converter,the three-level one features lower grid-side current harmonic components and less power losses.