Influence of Z-Source output impedance on dynamic properties of single-phase voltage source inverters for uninterrupted power supply

The study presents the problem of the influence of the Z-Source circuit output impedance on the small signal control transfer function of a voltage source inverter (VSI). The previously published inverter design algorithms did not take into account the output impedance of the DC/DC voltage step-up converters. The presented considerations should estimate the necessity of taking into account the Z-Source output impedance when designing an efficient control system for a DC/AC voltage inverter. It will be shown that the influence of the Z-Source storing energy in the inductances can be notable for low damping resistances and that it introduces two additional resonant frequencies to the nominator and denominator of the VSI control transfer function that are very close to each other. The magnitude Bode plots of the control transfer function of a VSI with a Z-Source are presented. The breadboard verification is also included.