Comparison of Various Modulation Techniques for Conventional, Quasi and Switched Inductor Z-Source Inverter Topologies

Pulse width modulation (PWM) inverters are essential elements in various applications requiring dc-ac conversion. In PWM inverters, the rms output voltage in the range of 0-100% of the applied dc-link voltage and an increase in the rms value beyond the dc-link voltage are not possible. Z-source inverters (ZSIs) incorporate an impedance network in the conventional power structure of PWM inverters. With this they are able to provide the rms output voltage higher than the dc-link voltage. The three main ZSI topologies that are widely reported are: (i) conventional ZSI, (ii) quasi-ZSI (q-ZSI), and (iii) switched inductor ZSI (SI-ZSI). Similarly, the three commonly employed modulation techniques reported for ZSIs are: (i) simple boost control (SBC), (ii) maximum boost control (MBC), and (iii) third harmonic maximum boost control (THBMC). This paper presents the simulation-based implementation of all the above-mentioned modulation techniques for conventional ZSI, quasi ZSI (q-ZSI) and switched inductor ZSI (SI-ZSI). Based on the simulation study, the paper presents a detailed comparison of the performance of ZSI topologies using different modulation techniques. This study can help in selecting the ZSI topology and suitable modulation technique for the voltage boost requirement demanded by the application.