A novel integrated three-phase, switched multi-winding power electronic transformer converter for wind power generation system

In this paper, a novel wind power generation system is proposed which uses an intermediate high frequency (few kHz) ac link for power conversion. The high frequency ac link is achieved by using a reduced switch-count three-phase power electronic transformer (PET). There are two primary windings and one secondary winding in each phase of the PET. The primary windings are coupled in exact phase opposition. A 3x3 matrix converter is used to convert the high frequency secondary voltage to the desired low frequency voltage to be applied at the generator terminals. Two modulation modes as a part of the PWM of the matrix converter are described. In the first mode of operation, the common-mode voltage is eliminated at the generator terminals however, the output voltage transfer ratio of the matrix converter is limited to 0.75. The other modulation mode has higher output voltage transfer ratio equal to 0.866 with finite high-frequency common-mode voltage at the generator terminals. A method for smooth transition between the two modes of operation is described.