12-pulse auto-transformer rectifier with harmonic current injection for non-grid-connected wind power applications

Harmonics in input currents caused by three-phase rectifiers are harmful to wind turbines generators, and multi-pulse rectifiers can be used to reduce the harmonics. Multi-pulse diode rectifiers are of the property that the total harmonic distortion (THD) of input currents and the ripples of output voltage are getting lower with growing pulses, while more complex connected transformer and more diode bridges are needed. A method that connecting a resistor or power factor correction (PFC) converter to the added windings of inter-phase transformers (IPTs) of 12-pulse rectifier, injects a current to the rectifier, so as to reduce the THD of input currents. Theoretical investigation of the method is presented, and the results of simulation and experiment verify the analysis.