Novel three-phase Y-rectifier cyclic 2 out of 3 DC output voltage balancing

A three-phase Y-rectifier is formed by the star connection of single-phase unity power factor rectifier systems and represents a highly interesting concept for the realisation of the input stage of high-power telecommunications power supply modules using established single-phase technology. However, for stable operation, control and balancing of the independent DC output voltages of the phase rectifier systems is required. A novel, easy to implement DC output voltage control concept is proposed in this paper. There, the mean value of all three DC output voltages is controlled and, in addition, always 2 out of the 3 DC voltages are compared and balanced. The basic operating principle of the control is described and the theoretical limit for the admissible asymmetric loading of the DC voltages is calculated. Finally, the theoretical considerations are verified by measurements on a 3times1 kW Y-rectifier prototype.