Power Conversion Device

Abstract: An inverter (10) includes a multilevel circuit having a plurality of switching elements (Q1 to Q4), converts first to third DC voltages supplied from a DC positive bus (L1), a DC neutral point bus (L2), and a DC negative bus (L3) into AC voltages, and supplies the AC voltages to a load. A control device superimposes, on a sinusoidal voltage command value, a third harmonic of the voltage command value to generate a reference AC voltage. The control device compares the reference AC voltage with a carrier signal having a peak-peak value corresponding to the DC voltage between the DC positive bus and the DC negative bus and generates a gate signal for turning on and off the plurality of switching elements (Q1-Q4). The control device detects the load factor of the power conversion device from the detection value of output current by a current detector (11). In a first case where the load factor is larger than a predetermined threshold value, the control device increases the amount of superimposition of the third harmonic wave with respect to the voltage command value as compared with a second case where the load factor is equal to or less than the threshold value.

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