The circulating current type cycloconverters have been applied to large capacity motor drive systems. A coupling of load current exists in the circulating current control loop, and deteriorates the control performance. In this paper, the circulating current control using rotational reference frame is proposed to suppress the coupling. The frequency of the fundamental component of the coupling is twice that of load. In addition, the circulating current is usually regulated to a constant do current. Authors have, therefore, applied the rotational reference frame synchronized with twice frequency of load to the circulating current control for a three-phase cycloconverter. The main component of the coupling can be compensated by the feedback control without the decoupling control. The effect of the proposed control scheme is confirmed by the digital simulation of an induction motor drive system.
