| 摘要 |
PURPOSE:To control an output voltage even with reference to a small voltage instruction value. CONSTITUTION:A power conversion apparatus which is provided with a neutral-point clamp-type inverter outputs a carrier-wave frequency instruction at a definite frequency by a frequency instruction operation means 27 on the basis of a function which uses the amplitude of a voltage instruction value as a variable when the detected value of the amplitude of the voltage instruction value is at a prescribed value or higher. It outputs a carrier-wave frequency instruction at a frequency which is lower the smaller the amplitude is when the detected value of the voltage instruction value is at a prescribed value or lower. Then, carrier-wave frequencies which are given to PWM modulation means 241, 242 are controlled so as to be variable by a variable- frequency generation means 30 on the basis of the carrier-wave frequency instruction of the frequency instruction operation means 27. In this manner, the number of gate turn-on operations per unit time of gate control signals which are output by the PWM modulation means 241, 242 is changed. Even when the amplitude of the voltage instruction value becomes small, the mean value of inverter output voltages does not become a definite value, and the inverter output voltages are controlled so as to be variable. |
