Three-Phase Y-Rectifier Cyclic 2 Out of 3 DC Output Voltage Balancing Control Method

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 realization 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. Here, the mean value of all three dc output voltages is controlled, and, in addition, always two out of the three dc voltages are compared and balanced. The basic operating principle of the control is described, the theoretical limit for the admissible asymmetric loading of the dc voltages is calculated, and numeric results for a 10-kW system are given. Finally, the theoretical considerations are verified by measurements on a $3 \times 1$ kW Y-rectifier prototype.