Half-bridge and full-bridge cell based multilevel PWM inverter with cascaded transformers

A new multilevel PWM inverter using half-bridge and full-bridge cells is presented to obtain high quality output voltage minimizing the number of switching devices. It is divided into two inverter modules according to functional purposes; one is a PWM inverter, and another is a level inverter assembly. The basic configuration is similar to that of a prior (3^n-1+2) level shaped PWM inverter. For the use of the PWM inverter, a half-bridge cell is substituted for a full-bridge one. Owing to this simple compositional alteration, the proposed inverter has several promising merits. It produces nearly sinusoidal output voltage waves by an effective increasing of output voltage level; nevertheless, it reduces two power switches due to a half-bridge configuration. By applying for an effective switching function, it reduces the size of the transformer connected with the PWM inverter. The validity of the proposed multilevel PWM inverter scheme is verified through computer-aided simulations and experimental results comparing with the prior approach.