Modified Staircase Modulation for Extending Unbalanced Loads Range of Cascaded H-Bridge Rectifier

In this paper, the relations among the active power distribution, modulation wave and unbalanced loads range are analyzed. A maximum unbalanced loads range is proposed by modifying modulation waveforms under the unity power factor. And a modified staircase modulation, which is easy to realize, is proposed for a single-phase cascaded H-bridge multilevel rectifier to extend the range of unbalanced loads. The control method has been fully investigated with theoretical analysis, simulation with two cascaded H-bridges. Simulation results are presented to support this strategy.