Decoupling Control of Input Voltage Balance for Diode-clamped Dual Buck Three-level Inverter

In multilevel inverter, it is a key problem that how to balance voltages of input capacitors. Because of the coupling of multilevel modulation and input voltage balance, no matter hardware circuit or control method of multilevel inverters are always complex, and speed of voltage balance is low. Dual Buck circuit which composed by two Buck DC/DC converter bridges, works in current half-period mode. A novel diode-clamped multilevel dual Buck inverter is presented, which inherits those features. At any moment, one Buck bridge works for inverter, another works as a reverse Boost circuit and charges up input capacitors. So inverter and voltage balance control are completely decoupled. If multilevel number is not small, this method is conducive to reduce the number of devices and the system complexity, and improve reliability of the system. Simulation and experiment of a diode-clamped three-level inverter verifies these analyses.