Three-level power conversion device, three-level power conversion device control method, and storage medium

2:

• The three-level power conversion device according to claim 1, wherein, for the pulse of which pulse width is controlled, the control unit causes a width of a region that defines a period in which a capacitor with a higher charging voltage between the first capacitor and the second capacitor is charged to be reduced and causes a width of a region that defines a period in which a capacitor with a lower charging voltage between the first capacitor and the second capacitor is discharged to be reduced.

4:

• The three-level power conversion device according to claim 3, wherein the pulse of which pulse width is controlled in the fixed pulse pattern is a pulse that maximizes conduction widths of the first switching element and the fourth switching element among a plurality of pulses of the fixed pulse pattern.

5:

• The three-level power conversion device according to claim 1, further comprising at least one three-level inverter,
• wherein when an active current of an output current output from the three-level inverter is greater than or equal to a threshold value, the control unit causes the three-level inverter to perform control for reducing the difference between the charging voltage of the first capacitor and the charging voltage of the second capacitor and does not control the pulse width of the pulse in the fixed pulse pattern.

6:

• The three-level power conversion device according to claim 5, further comprising at least one three-level inverter,
• wherein when a sum of active currents of output currents of the three-level inverter is greater than or equal to a threshold value, the control unit causes the three-level inverter to perform the control for reducing the difference between the charging voltage of the first capacitor and the charging voltage of the second capacitor and does not control the pulse width of the pulse in the fixed pulse pattern.

7:

• The three-level power conversion device according to claim 5, further comprising at least one three-level inverter,
• wherein when a maximum value of active currents of output currents of the three-level inverter is greater than or equal to a threshold value, the control unit causes the three-level inverter to perform the control for reducing the difference between the charging voltage of the first capacitor and the charging voltage of the second capacitor and does not control the pulse width of the pulse in the fixed pulse pattern.

8:

• The three-level power conversion device according to claim 1, further comprising at least one three-level inverter,
• wherein when a value related to a current value of a DC current output by the three-level converter is greater than or equal to a threshold value, the control unit causes the three-level inverter to perform control for reducing the difference between the charging voltage of the first capacitor and the charging voltage of the second capacitor and does not control the pulse width of the pulse in the fixed pulse pattern.

9:

• The three-level power conversion device according to claim 1, further comprising at least one three-level inverter,
• wherein when an active current of an input current input to the three-level inverter is greater than or equal to a threshold value, the control unit causes the three-level inverter to perform control for reducing the difference between the charging voltage of the first capacitor and the charging voltage of the second capacitor and does not control the pulse width of the pulse in the fixed pulse pattern.

10:

• The three-level power conversion device according to claim 1, further comprising at least one three-level inverter,
• wherein when an active current of an output current of the at least one three-level inverter is less than a threshold value, the control unit outputs, to the three-level converter, a control instruction for causing a predetermined reactive current that is delayed or advanced with respect to an AC voltage supplied to the three-level converter to flow and performs charging or discharging of the first capacitor and charging or discharging of the second capacitor by changing the pulse width.

11:

• The three-level power conversion device according to claim 1, further comprising at least one three-level inverter,
• wherein when a value related to a current value of a DC current output by the three-level converter or a DC current input to the three-level inverter is less than a threshold value, the control unit outputs, to the three-level converter, a control instruction for causing a predetermined reactive current that is delayed or advanced with respect to an AC voltage supplied to the three-level converter to flow and performs charging or discharging of the first capacitor and charging or discharging of the second capacitor by changing the pulse width.

12:

• The three-level power conversion device according to claim 1, wherein when an active current of an input current of the three-level converter is less than a threshold value, the control unit outputs, to the three-level converter, a control instruction for causing a predetermined reactive current that is delayed or advanced with respect to an AC voltage supplied to the three-level converter to flow and performs charging or discharging of the first capacitor and charging or discharging of the second capacitor by changing the pulse width.

14:

• The three-level power conversion device according to claim 10, wherein the control unit corrects a DC voltage reference value set as a control target for charging voltages with which the first capacitor and the second capacitor are charged so as to correspond to the control instruction for causing the predetermined reactive current to flow to generate a corrected DC voltage reference value, and controls a basic phase of an AC voltage of the three-level converter so that the charging voltage of the first capacitor and the charging voltage of the second capacitor approach the corrected DC voltage reference value.

15:

• The three-level power conversion device according to claim 1, wherein the control unit lengthens a time period from a time when the voltage difference between the charging voltage of the first capacitor and the charging voltage of the second capacitor becomes less than a threshold value to a time when control for reducing the voltage difference stops with respect to a time period from a time when the voltage difference becomes greater than or equal to the threshold value to a time when the control for reducing the voltage difference starts.

16:

• A control method of a three-level power conversion device comprising a three-level converter including a positive electrode terminal, a neutral point terminal, and a negative electrode terminal as output terminals, a first capacitor connected between the positive electrode terminal and the neutral point terminal, and a second capacitor connected between the neutral point terminal and the negative electrode terminal, the control method comprising:
• causing a switching element of the three-level converter to be operated using a fixed pulse pattern and, when a voltage difference between a charging voltage of the first capacitor and a charging voltage of the second capacitor is greater than or equal to a threshold value that has been set in advance, controlling a pulse width of at least one gate pulse included in the fixed pulse pattern and controlling charging and discharging of the first capacitor and the second capacitor.

17:

• A non-transitory storage medium that is readable by a computer and stores a computer program used in control of a three-level power conversion device that comprises a three-level converter including a positive electrode terminal, a neutral point terminal, and a negative electrode terminal as output terminals, a first capacitor connected between the positive electrode terminal and the neutral point terminal, and a second capacitor connected between the neutral point terminal and the negative electrode terminal, the computer program when executed by the computer causing the computer to:
• cause a switching element of the three-level converter to be operated using a fixed pulse pattern and, when a voltage difference between a charging voltage of the first capacitor and a charging voltage of the second capacitor is greater than or equal to a threshold value that has been set in advance, control a pulse width of at least one gate pulse included in the fixed pulse pattern and control charging and discharging of the first capacitor and the second capacitor.