A PWM ZVS High-Frequency-Link Three-Phase Inverter With T-Type NPC Unfolder

In this article, a pulsewidth modulated single-stage high frequency link three-phase dc-ac converter is proposed for grid integration of solar and fuel cell-based energy sources. On the dc side, the converter has three half-bridge legs which are zero-voltage switched over the entire line cycle without using any additional snubber circuit. On the ac side, two diode bridge rectifiers and one neutral point clamped (NPC) T-type three-level inverter are employed. The active switches in NPC inverter are switched either at line frequency or twice of it, incurring negligible switching loss. Modulation ensures soft commutation in the diode bridges. The intermediate three-level dc bus is pulsating and does not require any dc-filter capacitor and thus reduces overall filtering requirements. The high frequency galvanic isolation provides high power density, low-cost converter solution. The converter operation is analyzed in detail and verified on a 2-kW hardware prototype.