An Improved Amplitude-Domain PWM Technique With Minimum Inductor Current Ripple for Three-Phase Quasi-Z Source Inverter

An improved amplitude-domain (IAD-PWM) technique with minimum inductor current ripple for a three-phase quasi-Z-source inverter (qZSI) is proposed in this paper. The existing amplitude-domain technique expresses the three-phase voltage in a two-dimensional Cartesian coordinate system and divides the shoot-through time into several equal parts and inserts them in the switching sequence. However, this limits the scope and requires two large inductors to limit the inductor current ripple, resulting in a large volume and weight of the qZS inverter. The proposed IAD-PWM for the qZS inverter performs shoot-through behavior based on the geometric representation of the three-phase output voltage ranges in coordinate axes. Then, the shoot-through state time is divided into six unequal parts based on the discharging inductor current ripple, to achieve the minimum qZS inductor current ripples. The advantages of the proposed IAD-PWM lie in its extreme simplicity, as there is no shoot-through reference, and it avoids the complexity of vector and trigonometric functions calculations, while also having the capability to reduce qZS inductor current ripples or use smaller inductor in the qZSI, resulting in increasing of the whole system's power density. Moreover, the relationship among
v
_a
,
v
_b
and
v
_c
could be presented visually. The principle and the derivation of the proposed IAD-PWM are presented in detail, and the inductor current ripple under the proposed IAD-PWM and traditional ZSVM-6 are compared. Simulation and experimental results verify the outstanding features of the proposed IAD-PWM.