Patent ID: 11923759
Assignee: TOSHIBA MITSUBISHI—ELECTRIC INDUSTRIAL SYSTEMS CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A power conversion device comprising:
an inverter which includes switching elements, and which receives DC voltage of a DC voltage source and converts the DC voltage to variable-voltage variable-frequency AC voltage, to output the AC voltage to a load;
a controller configured to perform PWM control for ON/OFF driving the switching elements on the basis of an output voltage command value and an output frequency command value; and
a series unit of a positive-side capacitor and a negative-side capacitor, the series unit being connected on an input side of the inverter between a positive side and a negative side of the DC voltage, wherein
the inverter has, as output potentials, at least a positive-side potential and a negative-side potential of the DC voltage source and a potential of a neutral point which is a connection point between the positive-side capacitor and the negative-side capacitor,
the controller configured to execute a program stored in a memory that stores the program which, when executed by the controller, results in performance of steps comprising,
calculating a modulation factor for the inverter on the basis of the DC voltage of the DC voltage source and the output voltage command value,
determining a number of pulses per half cycle of a fundamental wave in the PWM control on the basis of the output frequency command value,
calculating a switching pattern for specifying switching phases which are timings of ON/OFF driving the switching elements on the basis of the calculated modulation factor and the determined number of pulses, so as to satisfy conditions for
ensuring the modulation factor,
eliminating harmonic components for respective orders of output voltage of the inverter,
ensuring a predetermined value for a phase difference between predetermined adjacent two of the switching phases, and
balancing voltage of the positive-side capacitor and voltage of the negative-side capacitor, and

generating a gate signal for ON/OFF driving the switching elements on the basis of the calculated switching pattern.