A variable speed generator-motor apparatus comprising a power converter connected to a DC power supply and a three-phase AC rotating electric machine connected to an AC side of the power converter, wherein the power converter includes six two-terminal arms (104RP, 104SP, 104TP, 104RN, 104SN, 104TN), each of which is formed by serially connecting k two-terminal unit converters that are able to output an arbitrary voltage via an energy storage element having a voltage source characteristic, where k is a natural number equal to one or larger, the AC rotating electric machine includes an armature winding with a 60-degree phase zone formed from a double layer coil, the armature winding being divided into a first pole side and a second pole side to form a double star connection by binding neutral terminals and to be drawn out as two sets of three-phase terminals (RP, SP, TP, RN, SN, TN), the three-phase terminals (RP, SP, TP) on the first pole side of the armature winding are respectively connected to first terminals (a) of the three two-terminal arms (104RP, 104SP, 104TP) of the power converter, and second terminals (b) of the three two-terminal arms (104RP, 104SP, 104TP) are star-connected to a first terminal of the DC power supply, the three-phase terminals (RN, SN, TN) on the second pole side of the armature winding are respectively connected to second terminals (b) of remaining three two-terminal arms (104RN, 104SN, 104TN) of the power converter, and first terminals (a) of the remaining three two-terminal arms (104RN, 104SN, 104TN) are star-connected to a second terminal of the DC power supply, and the variable speed generator-motor apparatus further comprises a control device configured to trisect direct current of the DC power supply to cause the trisected direct current (IDC/3) to flow through the three two-terminal arms (104RN, 104SN, 104TN) connected to the second terminal of the DC power supply, the three-phase terminals (RN, SN, TN) on the second pole side of the armature winding, the three-phase terminals (RP, SP, TP) on the first pole side of the armature winding, and the three two-terminal arms (104RP, 104SP, 104TP) connected to the first terminal of the DC power supply, in this order, for each phase, such that DC magnetomotive force generated by current of the double layer coil is cancelled, wherein the control device comprises a direct current adjustment unit configured to perform a control operation such that a command of the direct current (IDC*), obtained by dividing an output command value (P*) of an active power by an output voltage command (VDC*) of the DC power supply, corresponds with a measured/calculated value, and further comprises DC voltage command correction computing units (511P, 511N) configured to output output voltage commands (VRP*, VSP*, VTP*, VRN*, VSN*, VTN*) corresponding to the arms, based on phase voltages (+VR*, -VR*, +VS*, -VS*, +VT*, -VT*) of the rotating electric machine and a bisected output voltage (VDC/2) of the DC power supply. the power converter includes six two-terminal arms (104RP, 104SP, 104TP, 104RN, 104SN, 104TN), each of which is formed by serially connecting k the AC rotating electric machine includes an armature winding with a 60-degree phase zone formed from a double layer coil, the armature winding being divided into a first pole side and a second pole side to form a double star connection by binding neutral terminals and to be drawn out as two sets of three-phase terminals (RP, SP, TP, RN, SN, TN), the three-phase terminals (RP, SP, TP) on the first pole side of the armature winding are respectively connected to first terminals (a) of the three two-terminal arms (104RP, 104SP, 104TP) of the power converter, and second terminals (b) of the three two-terminal arms (104RP, 104SP, 104TP) are star-connected to a first terminal of the DC power supply, the three-phase terminals (RN, SN, TN) on the second pole side of the armature winding are respectively connected to second terminals (b) of remaining three two-terminal arms (104RN, 104SN, 104TN) of the power converter, and first terminals (a) of the remaining three two-terminal arms (104RN, 104SN, 104TN) are star-connected to a second terminal of the DC power supply, and the variable speed generator-motor apparatus further comprises a control device configured to trisect direct current of the DC power supply to cause the trisected direct current (IDC/3) to flow through the three two-terminal arms (104RN, 104SN, 104TN) connected to the second terminal of the DC power supply, the three-phase terminals (RN, SN, TN) on the second pole side of the armature winding, the three-phase terminals (RP, SP, TP) on the first pole side of the armature winding, and the three two-terminal arms (104RP, 104SP, 104TP) connected to the first terminal of the DC power supply, in this order, for each phase, such that DC magnetomotive force generated by current of the double layer coil is cancelled,