JP2872210B1 - Servo drive - Google Patents

Abstract

An object of the present invention is to prevent a distortion in a voltage and a current of a three-phase AC power supply when a three-phase AC power supply voltage exceeding a DC voltage value of a smoothing capacitor is input. A diode D1 of a three-phase bridge rectifier circuit 3 is provided.
D6 rectify the input AC voltage and supply it to the smoothing capacitor 4. The transistors Q1 to Q6 are turned on and off by the transistor control circuit 13 to regenerate the DC voltage to the three-phase AC power supply. The difference detection circuit 9 detects a difference between the DC voltage value Vd detected by the DC voltage detector and a predetermined voltage value Vs.
, A difference Vpd between the peak value Vp of the three-phase AC power supply and the DC voltage value Vd is detected. The switch 12 selects the output of the difference detection circuit 10 if the comparison result of the comparison circuit 11 is Vs ≦ Vp. The transistor control circuit 13 controls the DC voltage Vd to follow the peak value Vp of the three-phase AC power supply voltage according to the difference Vpd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo drive device for variably driving and controlling an AC motor, and more particularly to a servo drive device having a power regeneration function for returning regenerative energy from the AC motor to a power source.

[0002]

2. Description of the Related Art Generally, such a servo drive device is
For example, as shown in FIG. 3, a three-phase bridge rectifier circuit 3 for rectifying a three-phase AC supplied from a three-phase AC power supply 1 via a reactor 2, and a smoothing capacitor 4 for smoothing a rectified output and generating a DC voltage. And an inverter circuit 5 that converts a DC voltage into an AC voltage to drive-control the rotational speed and torque of an AC motor 6 (induction motor or synchronous motor).

A three-phase bridge rectifier circuit 3 includes a diode D
1 to D6 and transistors Q1 to Q6 in anti-parallel connection. The diodes D1 to D6 function as rectifying elements for converting an AC voltage to a DC voltage, and the transistors Q1 to Q6 function as switching elements for regenerating the DC voltage to a three-phase AC power supply.

The inverter circuit 5 includes diodes D7 to D12 and a transistor Q like the three-phase bridge rectifier circuit 3.
The transistors Q7 to Q12 are controlled by a control circuit (not shown) and function as switch elements for converting a DC voltage into an AC voltage and supplying the AC voltage to the AC motor 6. . The diodes D7 to D12 function as rectifying elements that convert a voltage induced when the AC motor 6 decelerates to a DC voltage and supply the DC voltage to the smoothing capacitor 4 as regenerative energy.

When the regenerative energy of the AC motor is supplied to the smoothing capacitor 4, the DC voltage Vd of the smoothing capacitor 4 increases. Smoothing capacitor 4
DC voltage V across the smoothing capacitor 4 to return the regenerative energy of the AC motor supplied to the
d, a DC voltage detector 7 for detecting the difference d, a difference detection circuit 9 for detecting a difference between the specified voltage value Vs and the DC voltage Vd specified in advance, and a transistor Q1 of the three-phase bridge rectifier circuit 3 based on the detected difference. And a transistor control circuit 13 for turning on and off Q6 to perform regenerative control.

[0006] The transistor control circuit 13 includes transistors Q1 to Q2 in accordance with the difference output from the difference detection circuit 9.
6 is turned on and off. That is, when the DC voltage Vd becomes higher than the specified voltage value Vs, the regenerative control is performed so that the DC voltage Vd decreases, and the DC voltage Vd becomes the specified voltage value Vs.
When it becomes lower than s, regenerative control is performed so that the difference becomes minimum so that the DC voltage Vd increases.

[0007] By performing the regenerative control in this manner, FIG.
As shown in the figure, the DC voltage Vd (broken line) can be held at a specified voltage value Vs with respect to the fluctuation of the three-phase AC power supply voltage (solid line), and this DC voltage Vd is inversely converted into an AC voltage by an inverter circuit. By doing so, it is possible to drive and control the AC motor with constant controllability. The specified voltage value Vs is set higher than the normal peak value of the input three-phase AC power supply voltage.

[0008]

In the above-mentioned conventional example,
When the peak value of the input three-phase AC power supply voltage is lower than the DC voltage value of the smoothing capacitor in a normal state, perform a normal regenerative control operation so as to maintain the DC voltage Vd of the smoothing capacitor at a specified voltage value. Can be. However, when the input three-phase AC power supply voltage rises abnormally and the peak value of the three-phase AC power supply voltage exceeds the DC voltage value of the smoothing capacitor, the diode D1 of the three-phase bridge rectifier circuit 3
To D6 are intermittently short-circuited, a current for charging the smoothing capacitor 4 flows, causing a distortion in the voltage and current of the three-phase AC power supply, generating harmonics and deteriorating the power factor. Further, there is a problem in that noise interference is caused to other circuits due to harmonics.

An object of the present invention is to provide a simple circuit configuration that does not cause distortion in the voltage and current of a three-phase AC power supply when a three-phase AC power supply voltage having a peak value exceeding the DC voltage value of a smoothing capacitor is input. Accordingly, it is an object of the present invention to provide a servo drive device capable of avoiding generation of a harmonic and deterioration of a power factor, and capable of preventing noise interference with other circuits due to generation of a harmonic.

[0010]

According to the servo drive device of the present invention, the peak value of the three-phase AC power supply voltage has risen to a predetermined voltage value higher than the normal peak value of the three-phase AC power supply voltage. At this time, the DC voltage of the smoothing capacitor is made to follow the peak value of the three-phase AC power supply voltage, and the DC voltage of the smoothing capacitor is controlled so as not to fall below the peak value of the three-phase AC power supply voltage.

More specifically, a three-phase rectifying element for rectifying a three-phase AC power supply voltage and outputting the rectified voltage to a smoothing capacitor and a switch element for controlling the on / off of the DC voltage of the smoothing capacitor to regenerate the three-phase AC power supply to the three-phase AC power supply. Inverter circuit including a bridge rectifier circuit, a switch element that converts a DC voltage of a smoothing capacitor into an AC voltage and supplies the AC motor to the AC motor, and a rectifier element that rectifies a voltage induced when the AC motor decelerates and outputs the voltage to a smoothing capacitor. An AC voltage detector for detecting the peak value of the three-phase AC power supply voltage, a DC voltage detector for detecting the DC voltage value of the smoothing capacitor, and detecting a difference between the DC voltage value of the smoothing capacitor and a specified voltage value A first difference detection circuit, and a second difference detection circuit for detecting a difference between a DC voltage value of the smoothing capacitor and a peak value of the three-phase AC power supply voltage. A comparison circuit that compares a peak value of the three-phase AC power supply voltage with a designated voltage value; and a switch that selects one of the difference outputs of the first and second difference detection circuits based on a comparison result of the comparison circuit. And a control circuit for controlling on / off of the switch element of the three-phase bridge rectifier circuit according to the output of the switch.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. Here, 1 is a three-phase AC power supply, 2 is a reactor, 3 is a three-phase bridge rectifier circuit, 4 is a smoothing capacitor,
5 is an inverter circuit, 6 is an AC motor, 7 is a DC voltage V
a DC voltage detector 9 for detecting d, a difference detection circuit 9 for detecting a difference between the designated voltage value Vs and the DC voltage Vd, and a transistor control circuit 13 for turning on / off a transistor of the three-phase bridge rectifier circuit to perform regenerative control. , These are shown in FIG.
Are substantially the same as those of the conventional example shown in FIG.

That is, the three-phase bridge rectifier circuit 3 is configured by connecting the diodes D1 to D6 and the transistors Q1 to Q6 in antiparallel, and rectifies the three-phase AC supplied from the three-phase AC power supply 1 via the reactor 2. Then, the DC voltage is output to the smoothing capacitor 4, and is controlled by the transistor control circuit 13 so that the DC voltage is inversely converted and regenerated to the three-phase AC power supply.

The inverter circuit 5 includes diodes D7 to D7.
12 and an inverse parallel connection of the transistors Q7 to Q12, and is controlled by a control circuit (not shown) to convert a DC voltage back to an AC voltage and supply the AC voltage to the AC motor 6, and when the AC motor 6 decelerates. The induced voltage is converted into a DC voltage and supplied to the smoothing capacitor 4.

The difference from the conventional example shown in FIG.
An AC voltage detector 8 for detecting a peak value Vp of the input three-phase AC power supply voltage, a peak value Vp of the AC power supply voltage and a DC voltage value V
d, a difference detection circuit 10 for comparing the specified voltage value Vs and the peak value Vp, and a difference output of the difference detection circuit 9 and the difference output of the difference detection circuit 10 based on a comparison result of the comparison circuit 11. That is, the switch 12 for selecting one of them and outputting the selected signal to the transistor control circuit 13 is provided to perform the regenerative control.

Next, the operation of the regeneration control will be described.

If the comparison result between the designated voltage value Vs and the peak value Vp is Vs> Vp, the switch 12 outputs the difference output Vsd of the difference detection circuit 9, that is, the designated voltage value Vs
And a difference between the DC voltage and the DC voltage Vd is selected and output to the transistor control circuit 13. If Vs ≦ Vp, the difference output Vpd of the difference detection circuit 10, that is, the difference between the peak value Vp of the AC power supply voltage and the DC voltage value Vd is selected and output to the transistor control circuit 13. The transistor control circuit 13 performs on / off control of the transistors Q1 to Q6 according to the difference output from the switch 12 so that the difference is minimized.

For example, as shown in FIG. 2, if the peak value Vp of the input three-phase AC power supply voltage changes with time as shown by the solid line, first, in the period Ta, the input three-phase AC power supply voltage Since the peak value Vp is lower than the specified voltage value Vs and Vs> Vp, the comparison circuit 11 outputs a plus value to the switch 12, and the switch 12 selects the difference output Vsd of the difference detection circuit 9 and selects the transistor Control circuit 1
Output to 3. The transistor control circuit 13 turns on / off the transistors Q1 to Q6 based on the difference output Vsd,
The regenerative control is performed so that the DC voltage Vd (shown by a broken line) is maintained at the specified voltage value Vs.

In the period Tb, the input three-phase AC power supply voltage rises and the peak value Vp exceeds the specified voltage value Vs (Vs ≦
Vp), the comparison circuit 11 outputs a negative value to the switch 12, and the switch 12
The differential output Vpd of the transistor control circuit 13
Output to The transistor control circuit 13 outputs the difference output V
The transistors Q1 to Q6 are turned on / off based on pd.

In this case, the DC voltage Vd is controlled so as to follow the peak value Vp of the input three-phase AC power supply voltage.
The peak value of the three-phase AC power supply voltage does not exceed the DC voltage value of the smoothing capacitor, and the diodes D1 to D6 of the three-phase bridge rectifier circuit 3 do not short-circuit. Therefore,
Distortion does not occur in the voltage and current of the three-phase AC power supply, generation of harmonics and deterioration of the power factor can be avoided, and noise disturbance to other circuits due to generation of harmonics can be prevented.

Thereafter, during the period Tc during which the input three-phase AC power supply voltage drops, Vs> Vp, so that the comparison circuit 11 outputs a positive value to the switch 12 and the switch 1
2 selects the difference output Vsd of the difference detection circuit 9. The transistor control circuit 13 controls the transistors Q1 to Q6 based on the difference output Vsd so as to maintain the DC voltage Vd at a specified voltage value.

[0023]

As described above, according to the present invention, by controlling the peak value of the input three-phase AC power supply voltage not to be higher than the DC voltage of the smoothing capacitor, the diode of the three-phase bridge rectifier circuit is reduced. The short-circuit state can be prevented, the distortion of the voltage and current of the three-phase AC power supply does not occur, and the generation of harmonics and the deterioration of the power factor can be avoided with a simple circuit configuration. Noise disturbance to the circuit can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a regeneration control operation of the servo drive device shown in FIG.

FIG. 3 is a block diagram of a conventional servo drive device.

4 is a diagram showing a regeneration control operation of the conventional example shown in FIG.

[Explanation of symbols]

 3 Three-phase bridge rectifier circuit 4 Smoothing capacitor 5 Inverter circuit 6 AC motor 7 DC voltage detector 8 AC voltage detector 9,10 Difference detection circuit 11 Comparison circuit 12 Switch 13 Transistor control circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinichi Murayama 1-1-1 Shinurashima-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside of Nippon Electric Robot Engineering Co., Ltd. (56) References JP-A-61-199481 (JP, A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 3/18 101 H02M 7/219 H02M 7/797 H02P 7/63 302

Claims (6)

(57) [Claims] 1. A three-phase bridge rectifier comprising a rectifying element for rectifying a three-phase AC power supply voltage and outputting the rectified voltage to a smoothing capacitor, and a switch element which is on / off controlled and regenerates the DC voltage of the smoothing capacitor to a three-phase AC power supply. Circuit and
An inverter circuit configured by a switch element that converts a DC voltage of the smoothing capacitor into an AC voltage and supplies the AC motor and a rectifying element that rectifies a voltage induced when the AC motor decelerates and outputs the rectified voltage to the smoothing capacitor; A regenerative control unit that controls on / off of a switch element of the three-phase bridge rectifier circuit, wherein the regenerative control unit increases a peak value of the three-phase AC power supply voltage to be equal to or higher than a DC voltage of the smoothing capacitor. And controlling the DC voltage of the smoothing capacitor so as to follow the peak value of the three-phase AC power supply voltage. 2. The regenerative control means, when the peak value of the three-phase AC power supply voltage has risen to a predetermined voltage value higher than a normal peak value of the three-phase AC power supply voltage, or more. 2. The servo drive device according to claim 1, wherein the control is performed so that the DC voltage of the capacitor does not fall below the peak value of the three-phase AC power supply voltage. 3. The regenerative control means controls the DC voltage of the smoothing capacitor to be the specified voltage value when the peak value of the three-phase AC power supply voltage is lower than the specified voltage value. 3. The servo drive device according to claim 2, wherein: 4. The regeneration control means includes: an AC voltage detector for detecting a peak value of the three-phase AC power supply voltage; a DC voltage detector for detecting a DC voltage value of the smoothing capacitor; A first method for detecting a difference from the specified voltage value;
A difference detection circuit, a second difference detection circuit for detecting a difference between the DC voltage value and the peak value, a comparison circuit for comparing the peak value with the specified voltage value, and a comparison result of the comparison circuit A switch for selecting one of the difference outputs of the first and second difference detection circuits, and a control circuit for controlling on / off of a switch element of the three-phase bridge rectifier circuit according to the output of the switch. The servo drive device according to claim 3, wherein: 5. The switch selects an output of the first difference detection circuit when the specified voltage value is higher than the peak value, and selects the output when the specified voltage value is equal to or less than the peak value. 5. The servo drive according to claim 4, wherein an output of the difference detection circuit is selected. 6. A three-phase bridge rectifier comprising: a rectifying element for rectifying a three-phase AC power supply voltage and outputting the rectified voltage to a smoothing capacitor; Circuit and
An inverter circuit configured by a switch element that converts a DC voltage of the smoothing capacitor into an AC voltage and supplies the AC motor and a rectifying element that rectifies a voltage induced when the AC motor decelerates and outputs the rectified voltage to the smoothing capacitor; An AC voltage detector for detecting a peak value of the three-phase AC power supply voltage, a DC voltage detector for detecting a DC voltage value of the smoothing capacitor, and a normal peak value of the DC voltage value and the three-phase AC power supply voltage A first difference detection circuit that detects a difference between a higher specified voltage value, a second difference detection circuit that detects a difference between the DC voltage value and the peak value, A comparison circuit for comparing the specified voltage value with a specified voltage value; a switch for selecting one of the difference outputs of the first and second difference detection circuits based on a comparison result of the comparison circuit; Servo drive, characterized in that a control circuit for turning on and off the switching elements of the three-phase bridge rectifier circuit in accordance with the output of the switch.