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 in whole 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 kW power inverter exhibiting 98.6% peak efficiency and realized in very small 100 × 60 × 30 mm³ volume.