A high voltage gain switched-coupled-inductor quasi-Z-source inverter

Abstract

Impedance-source (Z-source) inverters are widely used to overcome the drawbacks of traditional voltage-source inverters (VSIs) such as no boost ability, waveform distortion because of dead time to avoid shoot-through, and less immunity to EMI noise. Shortcomings associated with the Z-source inverters like discontinuous input current, high voltage stress on capacitors and no common ground point between the dc-source and inverter bridge has been addressed with the development of the quasi-Z-source (qZSI) inverters. This paper proposes design of an improved high voltage gain quasi-Z-source inverter by adopting a combination of switched-capacitor and switched-coupled-inductor (SCL). Use of the coupled-inductor to charge switched-capacitor can effectively enhances the voltage gain and reduces the turns ratio of the coupled-inductor. The proposed SCL-qZSI due to its higher voltage gain, utilizes smaller shoot-through duty ratio and consequently larger modulation index, thus having lower voltage stress on switching devices as compared to the traditional ZSIs and qZSIs. A detailed theoretical analysis of the proposed converter and its comparison with QZSI is given, and followed by simulation and experimental results.