Critical Parameter Analysis and Design of the Quasi-Z-Source Inverter

The quasi-Z-source inverter (qZSI) can operate as a single-stage buck-boost converter with continuous input currents for renewable energy applications. Generally, the inductances and capacitances in the quasi-Z-source networks (qZSn) are assumed to be large enough to obtain constant inductor currents and capacitor voltages. However, the values of the capacitors and inductors may vary in practical applications. Meanwhile, the load conditions and switching frequency can also affect the operation of the qZSI. This paper presents more operation states of the quasi-Z-source inverter (qZSI) in addition to the three desired normal states (i.e., shoot-through states, active states and null states). Through analyzing various operating modes, the critical values of capacitance and inductance considering the load condition and switching frequency for the qZSI in the continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are analyzed. Simulation results are provided to verify the analysis.