A 3-phase buck-boost converter for lowering the input current distortion of a voltage source-inverter drive

This paper presents a three-phase buck-boost switchmode power converter that lowers the input harmonics drawn by a voltage source PWM inverter drive. The buck-boost power converter examined, rated with a 0.26 per-unit current and drawing 6% of the total drive input power, is connected in parallel with the drive's main diode bridge and LC filter. 94% of the drive power is drawn through the diode rectifier. The low electrical stresses associated with the buck-boost power converter, in addition to the small number of high frequency switching components, makes the drive topology robust, conducive to soft-switching techniques and lowers the generation of EMI-RFI. The rectifier topologies are suitable for regulating the DC voltage rails for 2-level and 3-level inverters. For 3-level inverter drives using a centre-tapped capacitor DC-rail, the proposed rectifiers can compensate for load imbalances and maintain equal voltage drops across the two DC-rails. Since the buck-boost switchmode power converter is separate from the main drive diode rectifier, the drive can continue to operate satisfactorily even if the buck-boost converter fails. This same feature makes the buck-boost converter unit suitable as a drive option or for retrofitting. The drive configurations examined in the paper are verified with experimental results and Spice simulations.