Large-signal stability conditions for semi-quasi-Z-source inverters: switched and averaged models

TL;DR

This paper analyzes the stability of semi-quasi-Z-source inverters under large-signal conditions, providing theoretical conditions for stable operation using averaged and switched models, especially for linear resistive loads.

Contribution

It offers new stability criteria for semi-quasi-Z-source inverters with large signals, bridging theoretical analysis with practical operation strategies.

Findings

Boundedness of state trajectories is guaranteed under certain duty cycle conditions.

Stability depends on avoiding extreme duty cycle values and limiting PWM switching period.

Results support the inverter operation strategy proposed by Cao et al.

Abstract

The recently introduced semi-quasi-Z-source in- verter can be interpreted as a DC-DC converter whose input- output voltage gain may take any value between minus infinity and 1 depending on the applied duty cycle. In order to generate a sinusoidal voltage waveform at the output of this converter, a time-varying duty cycle needs to be applied. Application of a time-varying duty cycle that produces large-signal behavior requires careful consideration of stability issues. This paper provides stability results for both the large-signal averaged and the switched models of the semi-quasi-Z-source inverter operating in continuous conduction mode. We show that if the load is linear and purely resistive then the boundedness and ultimate boundedness of the state trajectories is guaranteed provided some reasonable operation conditions are ensured. These conditions amount to keeping the duty cycle away from the extreme values 0 or 1 (averaged and switched models), and limiting the maximum PWM switching period (switched model). The results obtained can be used to give theoretical justification to the inverter operation strategy recently proposed by Cao et al. in [1].