A power conversion system includes first and second voltage sources for driving a multiple-phase AC motor and a control unit. The control unit is configured to compute first and second output voltage command values used to drive the multiple-phase AC motor based on a first output voltage command vector corresponding to the voltage source that is charged and a second output voltage command vector corresponding to the voltage source that is discharged. The first and second output voltage command vectors are determined so that a resultant vector of the first and second output voltage command vectors is coincident with a motor voltage command vector corresponding to a motor voltage command value, and a motor current command vector corresponding to the motor current command value is positioned within an included angle formed between the second output voltage command vector and a negative vector of the first output voltage command vector.