[Problem] To provide a device for controlling a permanent magnet synchronous motor and a method of control therefor that make it possible to estimate magnetic pole positions of a non-salient-pole permanent magnet synchronous motor even while using a q-axis voltage. [Solution] The present invention is a system for controlling a permanent magnet synchronous motor, in which a variable-voltage/variable-frequency inverter is controlled on the basis of a d-axis voltage and a q-axis voltage. The control system generates a d-axis voltage command and a q-axis voltage command, removes a direct current component from the q-axis voltage command, estimates magnetic pole positions of the permanent magnet synchronous motor on the basis of a signal obtained by removing the direct current component from the q-axis voltage command, and makes use of the estimated magnetic pole positions to control the inverter.
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