Operational Analysis and Comparative Evaluation of Embedded Z-Source Inverters

This paper presents various embedded Z-source (EZ-source) inverters broadly classified as shunt or parallel embedded Z-source inverter. Being different from the traditional Z-source inverter, EZ-source inverters are constructed by inserting dc sources into the X-shaped impedance network so that the dc input current flows smoothly during the whole switching period unlike the traditional Z-source inverter. This feature is interesting when PV panels or fuel cells are assumed to power load since the continuous input current flow reduces control complexity of dc source and system design burden. Carefully analyzing the operational principles for shoot-through and nonshoot-through switching, it is first revealed that the shunt-embedded Z-source inverters with capacitors partially or fully replaced by dc sources can appropriately perform buck-boost operation with rear-end current source inverter (CSI) circuitry connected instead of the generic voltage source inverter (VSI) circuitry. Further proceeding on to the topological variation, parallel embedded Z-source inverters are presented with the detailed analysis of topological configuration and operational principles showing that they are the superior options among Z-source variants for clean energy harnessing without any loss of voltage buck-boost capability and with the inserted filtering capability for dc source. All theoretical findings are finally verified by PLECS simulations and constructed laboratory prototypes.