Patent ID: 8659918

Claim:
A method of controlling a power conversion device for converting alternating current into direct current or direct current into alternating current, wherein the power conversion device is configured to output a gate signal to a semiconductor switching element provided in the power conversion device, wherein the gate signal is obtained by a gate-signal generating section configured to apply a pulse-width modulation to a voltage command value, the method comprising steps of: comparing a maximum value among the voltage command values of multiple phases with an absolute value of a minimum value among the voltage command values of the multiple phases in a correction-term adder provided in the gate-signal generating section; calculating a first correction amount in the correction-term adder by selecting a signal obtained by subtracting the maximum value among the voltage command values from a maximum value of a triangular-wave carrier if the maximum value among the voltage command values is larger than the absolute value of the minimum value, and selecting a signal obtained by subtracting the minimum value among the voltage command values from a minimum value of the triangular-wave carrier if the absolute value of the minimum value is larger than the maximum value among the voltage command values; producing a triangular-wave-shaped signal in the correction-term adder by multiplying a gain by an addition signal of the maximum value among the voltage command values and the minimum value, wherein the triangular-wave-shaped signal is synchronized with the first correction amount; producing a second correction amount in the correction-term adder by selecting smaller one in absolute value between the triangular-wave-shaped signal and the first correction amount; calculating corrected voltage command values in the correction-term adder by adding the second correction amount respectively to the voltage command values of the multiple phases; obtaining the gate signal by the pulse -width modulation of each of the corrected voltage command values; and outputting the gate signal to the semiconductor switching element.