Analysis of an optimised single-phase UPS inverter based on a six-pack transistor module

The paper shows how a six-pack transistor inverter module can favorable be applied to a single-phase UPS application. Two fast switching parallel operating inverter legs are controlled by a phase shifted sinusoidal PWM pattern. The third inverter leg is switched with the fundamental frequency only. This leads to a circuit performance similar to that of 5-level PWM inverter. As a result the harmonic effects are minimized. Moreover, the losses in the six-pack module can be equally distributed to all semiconductors since the inverter legs are either stressed by higher conducting losses or by high switching losses. Within the paper all PWM harmonic effects of the inverter are described by analytical formulas