Summary In this paper, a new configuration of seven‐level quasi Z‐source (qZs)–based isolated inverter is introduced in the family of Z‐source–based multilevel inverters (MLIs). The proposed topology is an upgrade of qZs inverter and asymmetrical seven‐level inverter with significant advantages of high boost gain, reduced device count, and higher efficiency. In addition, the front‐end qZs converter provides wide input voltage regulation for eco‐friendly photovoltaic (PV) as well as fuel cell–based standalone/grid‐connected applications. The use of high‐frequency transformer blocks the leakage current from PV panels to the local load/grid, and the seven‐level inverter produces high quality sinusoidal output waveform, which reduces the filter size. Therefore, the working principle of the proposed configuration is tested in simulation, and an experimental verification is performed to validate the effectiveness of the model. A proportional‐integral (PI) controller is designed in field‐programmable gate array (FPGA) using Xilinx blocks, and the dynamic response of the model is evaluated for changes in input voltage and step changes in load. Moreover, a brief comparative assessment of proposed configuration with existing seven‐level qZs‐MLI is also presented.

In this paper, a new single-phase seven-level quasi-Z-source (qZs) inverter with reduced switch count for multistring photovoltaic applications is proposed, which is capable of supplying both direct current (dc) and alternating current (ac) loads simultaneously. The proposed configuration is derived from a combination of qZs networks and asymmetrical seven-level inverter. The front-end qZs converter boosts the input voltage obtained from the dc sources to the desired value, whereas the asymmetrical seven-level inverter performs dc-ac conversion with reduced switch count and provides better efficiency. The steady-state performance of the model is evaluated in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) of operation. In addition, the dynamic performance of the model is tested for the load as well as input voltage changes. A simple proportional-integral (PI) controller is implemented in FPGA Spartan-6 Processor using Xilinx system generator blocks.An experimental prototype is also developed to validate the feasibility of the proposed topology. Finally, a brief comparative assessment is formulated with other topologies to show the merits of the proposed structure.KEYWORDS multilevel inverter, power losses, quasi-Z-source (qZs) network, total harmonic distortion (THD)

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Impedance source-based multilevel inverters are becoming popular for emerging power generation technologies such as fuel cells, photovoltaic, and wind turbines. It is one of the most promising power electronic interfaces for single stage DC/AC conversion with inherent buck-boost capability. Therefore, in this paper, an extensive review of emerging impedance source-based multilevel inverter (Z-MLI) topologies is presented. These topologies are developed by the combination of impedance source network and multilevel inverter (MLI) with the merits of high voltage gain, enhanced reliability due to shoot-through immunity, improved input voltage regulation, reduced filter size, and better quality of supply. Most of the recent Z-MLI topologies are based on quasi-Z-source network which operates with continuous input current. In order to identify a suitable topology, an exhaustive comparison is made with various configurations of Z-MLIs in terms of component count, boost gain, switching stress, and control complexity.

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