High-power direct-driven wind power system topologies

DDVSCF (Direct-Driven Variable Speed Constant Frequency) WEGS (Wind Energy Generation System) needs high power converter, which may have different topological structures. The system control methods are different due to different topological characteristics. The basic topologies of DDVSCF WEGS are compared, while some high power converter structures are emphasized such as diode-clamped direct-driven type, cascaded H-bridge type, flying-capacitor direct-driven type and so on. Their advantages and disadvantages, key techniques, and existing problems are compared. Comparison results show that, for the flying-capacitor multi-level converter, voltage balance is difficult for its inconsistent switch load; for the cascade H-bridge multi-level converter, independent power source is needed, with high cost; for the diode clamp multi-level converter, appropriate control can solve the neutral point potential balance problem. Therefore, the diode clamp three-level PWM rectifier with low cost and simple control becomes a hot issue in the study of direct drive wind-power generation rectifier.