Dc current balancing control of a three-phase five-level bidirectional buck+boost-type converter

This work proposes a dc current balancing control for a three-phase high-power factor five-level buck+boost-type converter. The converter act as both a rectifier or as an inverter interfacing residential dc power distribution systems to the ac grid. A pulse width modulation with two symmetrically phase-shifted carriers drives the converter in an interleaved operation with interphase transformers (IPT´s). The modulation pattern ideally leads to null average voltages across the IPT´s at each switching period, but if an imbalance occurs the IPT´s saturation must be avoided. Novel feedback control scheme and modulation strategy that allows dc current balancing are described in this work. The effectiveness of the dc current balancing is verified in an experimental prototype.