Ineffectiveness of orthogonal axes cross-coupling decoupling technique in dual sequence current control

Proportional-integral (PI) controllers in a single synchronous reference frame (SRF) are popular for current control in voltage source converters. The most common technique to decouple the cross-coupling between its axes is to add/subtract at the output of the PI controller in each axis the current of the orthogonal axis, multiplied by the plant reactance. In case of imbalance, the single SRF is usually replaced by PI controllers in a pair of SRFs rotating with opposite sequences, which is known as double SRF control (DSRFC). It is generally assumed that, to decouple the axes cross-coupling in each SRF of DSRFC, the same decoupling strategy as for a single SRF structure can be applied. This paper proves that in DSRFC this approach does not produce any improvement.