Power conversion device

A power conversion device comprising:

• a power converter for performing power conversion between three-phase AC and DC, the power converter including a plurality of leg circuits each having a positive arm and a negative arm which are connected in series and are connected to an AC line for each phase, the plurality of leg circuits being connected in parallel between positive and negative DC buses;
• and
• a control device for controlling the power converter, wherein
• each of the positive arm and the negative arm of each leg circuit includes a converter cell composed of:
• a series unit including a plurality of semiconductor switching elements connected in series to each other;
• and a DC capacitor connected in parallel to the series unit,
• the control device includes a voltage command generation unit for generating a positive arm voltage command for the positive arm and a negative arm voltage command for the negative arm, and performs output control of each converter cell in the positive arm and the negative arm by PWM control,
• the voltage command generation unit includes:
• an AC current control unit for calculating an AC control command for controlling an AC current component flowing through the AC line for each phase;
• an arm balance control unit for, on the basis of positive capacitor voltage which is voltage of the DC capacitor in the positive arm and negative capacitor voltage which is voltage of the DC capacitor in the negative arm, calculating a first voltage adjustment value for balancing the positive capacitor voltage and the negative capacitor voltage;
• an AC-side command calculation unit for outputting an AC voltage command for AC voltage to be outputted to the AC line for each phase;
• and
• a command distributing unit for determining the positive arm voltage command and the negative arm voltage command on the basis of the AC voltage command and a DC voltage command for DC voltage between the DC buses, and
• the AC-side command calculation unit calculates the AC voltage command by adjusting the AC control command using the first voltage adjustment value.