| 摘要 |
PROBLEM TO BE SOLVED: To prevent the distortion and the instability of the output current of an inverter by adequately setting the amount of correction when the output voltage of a PWM inverter is corrected with the error voltage based on a short circuit preventing period. SOLUTION: A voltage correcting means 27A corrects the output voltage of an inverter by the error voltage, which is computed by using the short-circuit preventing period of upper and lower arms set by a short-circuits preventing- period forming means 29 for the upper and lower arms, a PWM carrier frequency and a DC voltage. When the absolute value of the output current of the inverter is larger than a specified value, the voltage correcting means 27A corrects the output voltage of the inverter in correspondence with the polarity of the output current of the inverter. When the absolute value of the output current of the inverter is smaller than the specified value, the output voltage of the inverter is corrected in correspondence with the polarity of the output voltage of the inverter. This is the PWM-controlled inverter performing these operations. Furthermore, a PWM carrier setting means 32, which sets the PWM carrier frequency, changes the PWM carrier frequency so that the ratio between the error voltage and the inverter output voltage is kept constant. |
