Abstract: An electric power conversion apparatus includes a converter 1 for rectifying ac electric power, a series-connected set, of capacitors 2A and 2B, connected to the dc side of the converter, an inverter 3 for, by setting one end of the series-connected capacitor set to a high-potential level, the other end of the set to a low-potential level, and a connection point between the capacitors to a medium-potential level, selecting any one of the levels and outputting three-phase ac, an inverter control unit 4 for controlling the inverter 3, and a voltage measurement device 8 for measuring a capacitor voltage Vdc as a voltage between both ends of the series-connected set, of the capacitors 2A and 2B; and the inverter control unit 4 further includes a beatless control unit 21 for controlling a modulation factor ? in response to the capacitor voltage Vdc, and a frequency fixing unit 22 for fixing to a command value the frequency of an ac voltage outputted from the inverter 3.

Abstract: A power converter includes: a converter (1) which rectifies an AC power; capacitor series assemblies (2A, 2B) connected to the DC side of the converter; an inverter (3) which assumes that one end of the capacitor series assemblies is at a high potential, the other end is at a low potential, and a series connection point is at an intermediate potential and selects one of the high potential, the intermediate potential, and the low potential for output of a 3-phase AC; an inverter control unit (4) which controls the inverter (3); and a voltage measuring device (8) which measures a capacitor voltage Vdc as a voltage between the both ends of the capacitor series assemblies (2A, 2B). The inverter control unit (4) has a beatless control unit (21) which controls the modulation ratio ? in accordance with a capacitor voltage Vdc and a frequency fixation unit (22) which fixes the frequency of the AC voltage outputted by the inverter (3) to an instruction value.