Single-Phase PWM Control of qZSIs for Switching-Loss and Capacitor Reduction Utilizing Accurate DC-Side Current Reference

This paper proposes a single-phase PWM control method for qZSIs that utilizes an accurate dc-side current reference, and that can reduces the number of the switching to 1/3. The proposed method regulates the average voltage of the dc-link in the impedance source so as to follow the highest line-to-line voltage of the ac mains. In this case, only one of three legs in qZSI operates under a high-frequency PWM and the other legs operate under the line-frequency switching in the proposed method. This paper also theoretically discusses the inductor current of the impedance source. As a result, this paper reveals that the capacitance of the impedance source strongly affects to the inductor current ripple and that the qZSI should minimize its capacitance in the impedance source to achieve its best performance. The proposed single-phase PWM are verified in experiments. The experimental results exhibit its highest efficiency of 97.6% at 1.1 kW by using a fabricated full-Si-based qZSI. The proposed single-phase PWM can reduce the power loss in the qZSI to less than half compared to a conventional modulation method. It is confirmed the validity of the theoretical analysis of the proposed method.