JP6232580B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor drive device having a current feedback control function.

  In general, in current control, a three-phase voltage command is generated so that the motor's three-phase current is detected and followed by the current command value, and output to an inverter composed of a plurality of semiconductor switches. A desired three-phase AC voltage is applied to the motor by a combination of ON / OFF of a plurality of semiconductor switches.

  PWM control, which generates a three-phase AC voltage from a DC voltage using a plurality of semiconductor switches, outputs a semiconductor switch ON / OFF signal based on a carrier signal and a voltage command value, and generates a pulsed voltage between motor lines. To be applied. By controlling the pulse width by ON / OFF of the semiconductor switch, the effective voltage value applied to the motor can be made sinusoidal.

In the current control using the PWM method, the switching noise of the semiconductor switch is superimposed on the current, and a pulsed voltage is applied between the motor lines, so that the carrier frequency is relative to the electric time constant of the motor. If the current is not sufficiently high, current ripple occurs, so that an accurate current detection value cannot be obtained, and the current control is adversely affected.
Thus, a method has been proposed in which a current detector of a ΣΔ method that detects an average current value in a certain section is used to match the section with the time of a mountain valley that is a half cycle of a carrier signal (for example, Patent Document 1). reference).

  According to this method, the current ripple component in the detected current value can be reduced by detecting the average current value in the half cycle section of the carrier signal, which is the current ripple period.

1372052738262_0.fnAnchor ('anNo11999264102')

  However, the above-described technique has a problem in that an influence when switching noise is superimposed on a current cannot be completely removed, and an accurate current detection value cannot be obtained.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a motor drive device that can obtain a current detection value that is small in current ripple component and is not affected by switching noise, and that can suppress the occurrence of vibration. To do.

In a motor drive device using a current detector for detecting motor current and having current feedback control by PWM control, a carrier signal generator for outputting a carrier signal, and a current for outputting a current detection trigger signal from the carrier signal and the PWM signal A detection timing generator; a current detector that detects an average current value in a current detection section derived from a current detection trigger signal and a PWM signal; and outputs a current detection value; and a current control trigger signal based on the carrier signal A current control timing generator for generating a current, a current controller for performing current control so that the detected current value follows a current command value, and outputting a voltage command, and an inverter for converting a PWM signal from the carrier signal and the voltage command A PWM controller for outputting to the section, wherein the current detection section is centered on a peak or valley of the carrier signal. Then, the period from the peak or valley of the carrier signal to the current detection trigger signal is doubled, and the current detection trigger signal changes the output timing in accordance with switching of each phase of the motor, and the current detection trigger signal Is the carrier signal corresponding to the switching timing of each phase of the motor before and after the peak or valley of the carrier signal, and the period from the peak or valley of the carrier signal to the peak or valley of the carrier signal. A motor driving device characterized in that the output is delayed from a peak or a valley of the motor and the switching timing is a period from switching to a predetermined switching noise remaining time.

  According to the motor driving apparatus of the first to third aspects, a current detection value that is small in current ripple component and is not affected by switching noise can be obtained, and generation of vibration can be suppressed.

Block diagram of main parts of motor drive apparatus according to Embodiment 1 of the present invention Timing chart of current detection and current control in Embodiment 1 of the present invention Explanatory drawing of the carrier signal and motor current in Embodiment 1 of this invention

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram of the main part of a motor drive device, which is a carrier signal generator 1 that outputs a carrier signal 11 and a current detection timing generator 2 that outputs a current detection trigger signal 12 from the carrier signal 11 and PWM signal 16. A current detector 3 that detects an average current value in a current detection section derived from the current detection trigger signal 12 and the PWM signal 16 and outputs a current detection value 13; and outputs a current control trigger signal 14 from the carrier signal 11 Current control timing generator 4 that outputs, current controller 5 that outputs voltage command 15 from current detection value 13 when current control trigger signal 14 is input, and PWM signal 16 that outputs carrier signal 11 and voltage command 15 PWM controller 6 is provided.

  First, current control and current detection timing will be described with reference to FIG. The current control trigger signal 14 is output at regular intervals once every half cycle of the carrier signal 11. The current detection trigger signal 12 is output once every half cycle of the carrier signal 11. The output timing of the current detection trigger signal 12 is a timing in which the switching noise remaining time is added to the change timing of the U-phase PWM output, the V-phase PWM output, and the W-phase PWM output before and after the peak or valley of the carrier signal 11. The carrier signal 11 is output at a timing delayed from the peak or valley of the carrier signal 11 by the period from the peak and valley to the closest timing.

  The switching noise remaining time can be defined by measuring in advance a period in which the current value is disturbed during switching.

In the valley portion of the carrier signal 11 in the figure, the timing obtained by adding the switching noise remaining time to the change timing of the U-phase PWM output before the valley is closest to the valley of the carrier signal 11 in T1 to T6. The current detection trigger signal 12 is output at a timing delayed from the trough of the carrier signal 11 by the period T1 from the trough to the trough of the carrier signal 11. In the peak portion of the carrier signal 11 in the figure, the change timing of the W-phase PWM output in front of the peak is closest to the peak of the carrier signal 11 from T7 to T12, and from the timing to the peak of the carrier signal 11 The current detection trigger signal 12 is output at a timing delayed from the peak of the carrier signal 11 by the period T12.

  The change timing of the U-phase PWM output, V-phase PWM output, and W-phase PWM output can be obtained from the past PWM signal 16 output from the PWM controller 6.

  The change timings of the U-phase PWM output, the V-phase PWM output, and the W-phase PWM output in the period P1 in the figure are the voltage command 15 that is the output of the current control process C0 one cycle before the current control process C1 (not shown). The change timing of the U-phase PWM output, the V-phase PWM output, and the W-phase PWM output obtained from the PWM signal 16 output from the PWM controller 6 as an input is the voltage command 15 that is the output of the current control process C1. Is obtained from the PWM signal 16 output from the PWM controller 6, and the change timing of the U-phase PWM output, the V-phase PWM output, and the W-phase PWM output in the period P3 is a voltage command that is an output of the current control process C2. 15 is obtained from the PWM signal 16 output from the PWM controller 6. As a result, current detection that is not affected by switching noise is possible.

  Next, the current detection section will be described with reference to FIG. The current detection section is centered on the peaks and valleys of the carrier signal 11 and has a period twice as long as the period from the peak and valley of the carrier signal 11 to the current detection trigger signal 12. In the valley portion of the carrier signal 11 in the figure, the current detection interval Z1 is twice as long as T1 around the valley of the carrier signal 11, and in the peak portion of the carrier signal 11, the current detection interval Z2 is The period is twice as long as T12 around the mountain.

  The current detection value 13 that is an input to the current controller 5 is an average value of the current values in the current detection section. When the current detector 3 is of the ΣΔ method, normal current detection is always performed, and when the current detection trigger signal 12 is input, an average current value from that point to the previous section set by decimation is detected. Therefore, it can be realized by switching the decimation so that the average current value in the current detection section can be obtained.

  When the current detector 3 is a CT system, it can be realized by sampling the current value a plurality of times at regular intervals during a half cycle of the carrier signal and taking the average of the current values sampled in the current detection section. The reason why the center of the current detection section is the peak and valley of the carrier signal 11 will be described with reference to FIG. FIG. 3 shows the relationship between the carrier signal 11 and the motor current. In the vicinity of the middle of the peak and valley of the carrier signal 11, the motor current changes greatly due to switching. The average value of the motor current in the half cycle of the carrier signal 11 can be obtained at the timing of the peak and valley of the carrier signal 11. By setting the center of the current detection section as the peak and valley of the carrier signal 11, Current detection that is not affected is possible.

  In this embodiment, the current detection process and the current control process are described to be executed at the peak and valley of the carrier signal. However, the present invention is also applicable to the case where the current detection process and the current control process are executed only at the peak of the carrier signal or only at the valley of the carrier signal. Is possible.

  The motor drive device of the present invention is also useful for applications that require high-speed response and low vibration.

1: Carrier signal generator 2: Current detection timing generator 3: Current detector 4: Current control timing generator 5: Current controller 6: PWM controller 11: Carrier signal 12: Current detection trigger signal 13: Current detection value 14: Current control trigger signal 15: Voltage command 16: PWM signal

Claims (3)

In a motor drive device having a current feedback control by PWM control using a current detector for detecting a motor current,
A carrier signal generator for outputting a carrier signal;
A current detection timing generator for outputting a current detection trigger signal from the carrier signal and the PWM signal;
A current detector that detects an average current value in a current detection section derived from the current detection trigger signal and the PWM signal and outputs a current detection value;
A current control timing generator for generating a current control trigger signal based on the carrier signal;
A current controller for controlling the current detection value to follow the current command value and outputting a voltage command; and
A PWM controller that outputs a PWM signal from the carrier signal and the voltage command to an inverter unit;
The current detection section is centered on a peak or valley of a carrier signal, and is twice the period from the peak or valley of the carrier signal to the current detection trigger signal,
The motor driving apparatus characterized in that the current detection trigger signal changes an output timing in accordance with switching of each phase of the motor. The current detection trigger signal is the difference between the switching timing of each phase of the motor before and after the peak or valley of the carrier signal, and the period from the peak or valley of the carrier signal to the peak or valley of the carrier signal. The motor drive device according to claim 1, wherein the motor drive device outputs only a delay from a peak or valley of the carrier signal. The motor driving device according to claim 2 , wherein the switching timing is a period from switching to a predetermined switching noise remaining time.

Images