DC-DC nonisolated boost converter with high voltage gain adequate for split-capacitor inverter applications

This paper presents a dc-dc boost converter with high voltage gain based on three-state switching cell for split-capacitor neutral-point clamped inverters. The proposed converter is analyzed considering the operation in continuous conduction mode and duty cycle higher than 0.5, which corresponds to overlapping mode. The main characteristics of the topology are: operation at high switching frequency, while the input inductor is designed for twice such frequency; in order to minimize weight and volume, the voltage stress across the switches is lower than half of the output voltage and naturally clamped by one output capacitor, allowing the use of transistors MOSFETs with reduced intrinsic on-resistance; the input current presents small ripple; the output voltage can be further step up by increasing the transformer turns ratio without compromising the voltage stress across the switches; the output voltage is balanced thus making the converter suitable for supplying split-capacitor inverters. Several topologies where high voltage step up is possible are initially investigated in literature. Then the principle of operation, the design methodology, and experimental results for a 1kW prototype are presented to validate the theoretical analysis and demonstrate the converter performance.