Understanding the operation of a Z-source inverter for photovoltaic application with a design example

Traditional voltage source inverter (VSI) and current source inverter (CSI) technology has advanced to the new Z-source inverter (ZSI) with a built-in impedance network, with modification to the traditional pulse width modulated (PWM) signal. Modified PWM signal accommodates the shoot-through (ST) signal (which would destroy the traditional inverters) in order to buck or boost the DC input voltage from a value between zero and infinity. The unique impedance network of passive elements, which gives a single-stage conversion, needs to be understood in detail in order to design a ZSI. The study compares traditional inverters against the ZSI and discusses the detailed operation modes involved. Circuit calculations, self-boost phenomenon, ST, inductor and capacitor design calculations, boost control methods and device selection procedures are discussed. Photovoltaic source (PV) being one of the most promising DC sources of the future, a design example involving PV and all the circuit calculations along with matching simulation results, are provided in this study.