Soft-Switching Modulation Method for Full-Bridge DC-AC HF-Link Inverter

This paper presents an improved modulation method for the cycloconverter stage of high frequency-link DC-AC inverters. By applying the quasi-resonant commutation mode during the entire operating period, the fast and reliable discharge of DC-side capacitances can be provided even if the output current is close to zero. This allows to ensure zero voltage switching (ZVS) conditions for the DC-side transistors, while applying small external snubber capacitors to reduce their turn-off losses. The proposed modulation strategy was significantly simplified and requires no external active auxiliary circuits or multi-mode operation. Moreover, two of the AC-side switches can operate at the fundamental frequency, while the rest operate with zero current switching (ZCS). The proposed modulation method is verified with mathematical analysis, simulation model and experimental prototype of full-bridge HF -link inverter.