부산대학교 도서관

The paper presents a concept of the current-fed bidirectional quasi-Z-source converter with modified impedance network. In a standard topology the voltage across the input diode becomes very high during the rectifier mode, which causes very high losses and increases cost of the device. Structure of a proposed impedance network is designed to limit the voltage of the capacitors by a factor of two and, in consequence, voltage stress of the input diode is also lower. The modified current-fed quasi Z-source converter connected to the standard grid $(3 \times 400\mathrm{V}$ RMS) is able to operate with SiC Schottky diodes rated at 1200 V. Circuit analysis and simulation study of the standard and modified topology are provided in this paper to show differences and improved performance of the proposed solution. The system is simulated with models of real power devices-SiC MOSFETs and Schottky diodes and is clearly seen that voltage across the diodes is less than 800 V. Then, the 6 kVA SiC-based laboratory model is also presented and, finally, experiments performed at nominal conditions during the inverter mode are shown. The current-fed bidirectional quasi-Z-source converter supplied from 400 V DC reaches peak efficiency of 97.6 % operating at 100 kHz.