Balanced control of multicell AC-DC converter with cascaded H-bridge cells

The multicell converter is used to enhance the converter rating and improve the power quality on input AC side. The conventional multicell AC-DC converter with fixed hierarchy of H-bridge cells leads to unbalanced voltages across the DC side of the cells. This paper presents a hierarchal hysteresis current controlled cascaded H-bridge multicell AC-DC converter. The problem of unbalanced voltages has been addressed by hierarchal change in sequence of the converter H-bridges. The current controlled AC-DC converters with hierarchal change in sequence of the converter H-bridges will ensure balanced voltages across the DC capacitors of the cells. The input side maintains the unity power factor with sinusoidal AC current. The balanced control of converter is verified through a single-phase two cell cascaded H-bridge AC-DC converter, both using the simulation studies and laboratory experiments. Accurate synchronization for swapping of hierarchy with FPGA controller ensures equal stress on each cells and hence voltage balancing.