Modular hysteresis current control of hybrid multilevel inverters

The cascading of H-bridges, with different DC-link potentials and power devices, to implement modular hybrid binary, quasilinear and trinary multilevel inverters has been a recent research area. To achieve true modular implementation of a hybrid inverter, it is important to design each H-bridge as a stand-alone power bridge with its own integrated controller. Various three-level hysteresis controllers suitable for integrating with an H-bridge inverter to form a stand-alone power bridge are presented. The hysteresis current controllers on multiple power bridges can be co-ordinated to implement a modular hysteresis-controlled hybrid multilevel inverter with robust reference tracking and fast dynamic performance. Digital logic synthesised to ensure equal switch utilisation within each of the power bridges is also presented. Simulation and experimental results verify the performance and practicality of the proposed modular hysteresis control of hybrid multilevel inverters.