A Soft Switched Three Level Quasi Z-Source Converter With Coupled Inductor Based High Conversion Ratio and Continuous Input Current for Renewable Energy Application

In this article, a fully soft switched high step up three level converter based on a Quasi-impedance source is introduced for use in photovoltaic applications. In the proposed converter, since an active switch is used instead of the diode in the impedance network, conduction loss associated with the diode is reduced, and zero-voltage-switching characteristics are provided in a wide range of output power for power switches, resulting in the improvement of efficiency. The proposed converter takes advantage of three level structure and it experiences much lower voltage stress on semiconductor elements compared to existing high step-up structures. This allows the use of mosfets with lower on the resistance, leading to reduced conduction losses and cost. Furthermore, the boost inductor in the input section not only maintains continuous input current, avoiding the need for bulky input capacitors, but also significantly optimizes power density and reduces cost. Other advantages of the proposed converter include high voltage gain with low duty cycle and the ability to turn off all diodes under ZCS condition. Experimental results from a 200-W laboratory prototype are provided to validate the proposed converter’s performance.