Impedance Network Design of the Quasi-Z-Source Inverter

The z-source inverter (ZSI) has been widely used for single-stage power conversion since its inception. There are just a few limitations to the ZSI, viz., the input current to the inverter is discontinuous because of the presence of the diode at the front, and the capacitors in the impedance network sustain high voltage stress. With the quasi-Z-source inverter (qZSI), these problems have been resolved. Like the ZSI, the qZSI has three operating states: traditional zero, active, and shoot-through. Along with the above desired dynamic states, three static states that may occur are being discussed. The impedance network should be appropriately designed to prevent these static states. In this paper, the impedance network of the qZSI is illustrated using a design example. Computer simulations utilizing MATLAB/SIMULINK and laboratory experiments are used to validate the design data.