Motor drive system and its control method

Abstract

A ripple detection unit (310) detects a ripple current width (Irp) of a motor current controlled according to PWM control. A ripple reference setting unit (320) sets a reference value (Irp#) of the ripple current width. A frequency adjusting unit (350) sets a control signal (Vfq) indicating a carrier frequency of the PWM control according to a ripple current width deviation. A carrier generation unit (360) generates a carrier (Vcr) of the frequency based on the control signal (Vfq). Thus, it is possible to realize feedback control of the carrier frequency for maintaining the ripple current width at an appropriate level.

Description

technical field [0001] The present invention relates to a motor drive system and its control method, in particular to a motor drive system with a pulse width modulation (PWM) controlled power converter and its control method. Background technique [0002] Among power converters that perform PWM control, there is known a configuration that variably controls the frequency of a carrier wave (carrier frequency) used in PWM control. For example, Japanese Unexamined Patent Publication No. 1-321868 (Patent Document 1) discloses a configuration in which a series resonant circuit is provided in parallel with a smoothing capacitor in a power conversion device that performs PWM control, and the carrier frequency of PWM control is variable. , so that the resonant frequency of the series resonant circuit coincides with the frequency of the pulsating component included in the DC current of the power conversion device accompanied by PWM control within a predetermined range. [0003] In ad...

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Problems solved by technology

In addition, in the PWM power conversion device of Patent Document 1, it is necessary to additionally arrange a series resonant circuit, so the cost increases due to an increase in the number of components.

[0012] In addition, in the current control device of the VVVF converter disclosed in Patent Document 2, the following feedback control is performed, but it is not disclosed that the magnitude of the AC component (ripple current) in each phase current is controlled to an appropriate level. It is to increase the carrier frequency when the deviation from the command value of each phase current is large, and to reduce the carrier frequency when the difference is small

[0013] On the other hand, in the power conversion device disclosed in Patent Document 4, the ripple current can be minimized even when the carrier frequency is changed by properly controlling the phase difference of the carrier signal between the two converters. Controlling the magnitude of the pulsating current to an appropriate level is not disclosed

In addition, the AC motor control device described in Patent Document 5 is a device for controlling a permanent magnet synchronous motor, but does not disclose changing the carrier frequency according to the ripple current.

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