An output voltage command signal for outputting a specified three-phase ac output voltage is generated by a line voltage control command signal generating section, and a signal representing a current flow ratio is generated by a current flow ratio generating section based on a specified input current command signal. The output voltage command signal is corrected by a command signal computing section based on the output voltage command signal generated by the line voltage control command signal generating section and the signal representing the current flow ratio generated by the current flow ratio generating section. A PWM conversion signal is generated by a PWM conversion signal generating section based on the corrected output voltage command signal and a carrier signal. Based on the generated PWM conversion signal, a three-phase ac input voltage is converted into a specified three-phase ac input voltage by a conversion section.