Abstract: In many countries single-phase power is used for rural power distribution which limits the use of three phase variable frequency drives (VFDs). Three-phase VFDs are often required to operate from a single-phase ac source. The aim of this project is to design and implement a circuit that can be used for three phase VFDs operating from single phase ac source. Powering up of three-phase VFDs from single-phase ac source requires addressing many issues: higher RMS value of input diode current, higher ripple voltage across the dc bus capacitor, higher peak input current, higher input current distortion, lower power factor and poor system efficiency. All of these lead to severe derating of VFDs for single-phase applications. A new low-cost single-phase active circuit based on injecting current into the midpoint of the dc bus employing only one bidirectional switch can be used to address the aforementioned problems. This method shows that VFDs need not be derated to achieve rated output power.
Keywords: Drives for rural applications, single-phase active filter, single-phase input drives, single-phase-to-three-phase converter.