Modular single-stage, three-phase full-bridge converter with inherent power factor correction and isolated output

The modular development of a three-phase, single-stage AC-DC power converter based on single-phase AC-DC full-bridge converters is described. Three-wired and four-wired modular converter systems are examined and compared. The three-wired system is found to have inherent power factor correction and is better than the four-wired system in terms of harmonic content. The fluctuation of the converter neutral voltage in the three-wired system and the voltage stress on the power switches are analysed. A simulation based on a PSPICE model is included. The modular converter does not have a minimum component count when compared with non-modular converters. But the modular converter offers attractive features such as simple DC-DC switching control, electrically isolated output, inherent power factor correction and single-stage power conversion without using power devices with excessively high voltages and current ratings. It also has flexible power expandability and the potential to simplify the design and production of high-power AC-DC power converter products. The operation of the modular full-bridge converter has been confirmed with a 1.5kW prototype. Both predictions and measurements show that the power quality of three-wired modular converter system is good and well above IEC-1000 standards.