Hitachi Industrial Equipment Systems Co., Ltd.

Yuusuke Arao

Shigehisa Aoyagi

Koichiro Nagata

Yoichiro Arakawa

In a power conversion device that includes a PWM converting means for generating a PWM pulse by comparing three-phase voltage commands with a triangular wave carrier signal, a power converter for converting between a DC voltage and a three-phase AC voltage by driving a switching element according to the PWM pulse, a current detecting means for detecting a pulsed current flowing through a DC bus conductor of a main circuit, and a voltage command correcting means for correcting three-phase voltage commands, which corrects the three-phase voltage commands so that a line voltage value between the maximum phase and an intermediate phase and a line voltage value between the intermediate phase and the minimum phase are each equal to or larger than a predetermined value, the maximum phase, intermediate phase, and minimum phase being determined in correspondence to momentary values of the three-phase voltage commands arranged in descending order, if the voltage command is outside an allowable upper limit or lower limit, not only the voltage command for the maximum phase and/or the minimum phase but also the voltage command for the intermediate phase are corrected. Accordingly, the inability to detect a current due to a restriction imposed by an upper limit or a lower limit for an output voltage is eliminated, and highly precise control of the power conversion device is achieved independently of the situation.

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Narashino, Japan

Yuusuke Arao