Space vector modulated four-wire unidirectional three-phase/level/switch (VIENNA) rectifier with an additional leg for DC link voltage balancing

This paper studies two different methods for the partial DC link voltage balancing of the three-level unidirectional rectifier having supply neutral connection at DC link midpoint. In the first balancing method an additional balancing inductor leg is used to control the partial DC link voltages. The other method balances the voltages by drawing asymmetrical, quasi-sinusoidal phase currents from the utility. The analysis and the functioning of the balancing methods are verified with measurements from 10 kW 230 V / 400 V 50 Hz laboratory prototype. The control system and the modulator are realized with Freescale MPC563 single-chip microcontroller.