The paper presents a control method for the three phase power converter operating under unbalanced grid voltage conditions. The method uses a new transformation to the non-Cartesian frame, which makes the controlled current vector components balanced in this frame even if originally the three phase current is referenced as unbalanced. Further Park’s transformation makes the controlled variables constant, which allows to apply proportional-integral terms as current controllers independently of the required control target. Several control targets known from literature have been analyzed with regard to the required new transformation parameters, and the transformation parameters for all targets have been found. Simulation results are shown to prove the theoretical analysis, and the experimental tests results are presented as practical validation of the proposed use of the non-Cartesian frame in control.