Current control device of synchronous motor

Patent metadata

Field	Value
Publication number	US-9225270-B2
Application number	US-201414332887-A
Country	US
Kind code	B2
Filing date	Jul 16, 2014
Priority date	Jul 18, 2013
Publication date	Dec 29, 2015
Grant date	Dec 29, 2015

Abstract

A current control device of a synchronous motor comprises a provisional d-phase current command calculation unit; a voltage amplitude calculation unit calculating a magnitude of a voltage command vector in a previous sampling period; a voltage ratio calculation unit determining a voltage ratio between the magnitude of the voltage command vector and a maximum output voltage of an amplifier; a target d-phase current calculation unit obtaining a d-phase current command in the previous sampling period, and calculating a target d-phase current command from the voltage ratio and the d-phase current command; a correction value calculation unit determining a correction value by passing a difference between the provisional d-phase current command and the target d-phase current command through a low-pass filter; and an adder adding the correction value to the d-phase current command in the present sampling period to calculate a new d-phase current command.

First claim

What is claimed is:

1. A current control device of a synchronous motor, generating a current command in a predetermined sampling period on the basis of an orthogonal dq coordinate system, the current control device comprising:
a provisional d-phase current command calculation unit calculating a provisional d-phase current command on the basis of a torque command, a current at no load, and a current at maximum load;
a voltage amplitude calculation unit obtaining a voltage command vector, which is an output of a current control in a previous sampling period, that is one cycle prior to the present sampling period, and calculating a magnitude of the voltage command vector;
a voltage ratio calculation unit determining a voltage ratio between the magnitude of the voltage command vector and a maximum output voltage of an amplifier;
a target d-phase current calculation unit obtaining a d-phase current command in the previous sampling period, and calculating a target d-phase current command from the voltage ratio and the d-phase current command;
a correction value calculation unit determining a correction value by passing a difference between the provisional d-phase current command in the present sampling period and the target d-phase current command through a low-pass filter; and
an adder adding the correction value to the provisional d-phase current command in the present sampling period in order to calculate a new d-phase current command.

2. The current control device of a synchronous motor according to claim 1 , further comprising
a current command limiting value calculation unit calculating a d-phase current command limiting value and a q-phase current command limiting value,
wherein a maximum value of the new d-phase current command is limited by √((set maximum current) 2 −(the q-phase current command limiting value) 2 ).

3. The current control device of a synchronous motor according to claim 1 , wherein
the voltage amplitude calculation unit removes a high frequency component of obtained voltage command vector by using a low-pass filter.

4. The current control device of a synchronous motor according to claim 1 , wherein
the target d-phase current calculation unit calculates the target d-phase current command on the basis of the following formula;
(target d -phase current command)=(voltage ratio)×(previous d -phase current command)+(voltage ratio−1)×(short-circuit current).

5. The current control device of a synchronous motor according to claim 1 , wherein
when neither a first condition by which the synchronous motor is at a no-load base speed or above, nor a second condition by which the synchronous motor is at a maximum-load base speed or above and also surpasses a magnitude of a predetermined voltage command vector, is met, the correction value is set to zero.

Assignees

• Fanuc Corp

Inventors

• Takahashi Kenji

Classifications

• H02P21/0089

  using field weakening · CPC title

• H02P6/10

  Arrangements for controlling torque ripple, e.g. providing reduced torque ripple · CPC title

• H02P21/10 Primary

  Direct field-oriented control; Rotor flux feed-back control · CPC title

• H02P6/002 Primary

  Electricity · mapped topic