Three-Level PWM Floating H-Bridge Sinewave Power Inverter for High-Voltage and High-Efficiency Applications

This paper presents a topology of a single-phase floating full-bridge three-level pulse width modulation (PWM) power inverter suitable for high-voltage/high-power dc-ac conversion. High power efficiency is obtained thanks to the slow (50/60 Hz) biasing of the H-bridge power supply terminals, allowed by a particular arrangement and control of two complementary active neutral point clamped voltage-source converters. As result, the main PWM switching voltage as well as the maximum drain-source voltage V-DSS of related transistors are reduced to one-half of the input V-DD voltage. This is allowed by the internally generated and accurately balanced middle-node voltage V-DD/2. Consequently, advantageous r(DS(on)) of the low-voltage transistors, along with reduced switching PWM voltage result in considerable decreasing of power losses inwhole output power range. This paper introduces the main concept of the floating H-bridge topology, and presents in detail the circuit realization. The performances are demonstrated on 450V(DC)/230V(AC) 2 kWpower inverter exhibiting 98.6% peak efficiency and realized in very small 100 x 60 x 30 mm(3) volume.