PROBLEM TO BE SOLVED: To implement overmodulation PWM control by preventing wind-up when generating a voltage command from a current command under PI control.SOLUTION: In the case where a result obtained by multiplying a DC bus voltage eby a bus voltage utilization rate η is smaller than a terminal voltage command v1*, a wind-up prevention control unit 12 calculates an ACR variable integration gain Kia=0. Current controllers 13 and 14 stop integration functions, and a d-axis voltage command and a q-axis voltage command are calculated by proportional functions. The integration functions of the current controllers 13 and 14 are stopped, thereby preventing integration control due to the current controllers 13 and 14 from being brought into a wind-up state. An AC motor 2 may then be brought into an appropriately controllable state and overmodulation PWM control can be implemented for performing PWM control in a state of overmodulation.SELECTED DRAWING: Figure 1
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