JP3536695B2 - Variable speed device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed device, and more particularly to a variable speed device capable of processing regenerative energy during a load regenerative operation state.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a configuration of a conventional variable speed device. In the figure, 31 is an AC power (R, S,
T) into a DC power converter, 32 is a smoothing capacitor that stores the converted DC power as a constant DC voltage, 33 is a DC power of variable frequency and variable voltage AC power (U, V, W in the figure) ), 34
Is a current detector for detecting the output current of the inverter unit 33,
35 is a voltage detector for detecting the DC bus voltage of the converter unit 31; 36 is a CPU for judging data of the current detector 34 or the voltage detector 35 and controlling the inverter unit 33
, 37 are induction motors to be controlled by the variable speed device.

FIG. 5 is a diagram showing the operation when a conventional variable speed device is used for a general variable speed control such as a transfer machine.
In the figure, f is the output frequency, Vdc is the DC bus voltage,
Vdc1 is a DC bus voltage stall level, Vdc2 is a DC bus voltage overvoltage level, and t1 is a stop time for stopping output of the output frequency f.

The output frequency f is lowered by a deceleration command (p1
1) The induction motor 37 is decelerated. At this time, the regenerative energy from the induction motor 37 causes the DC bus voltage Vdc to be reduced.
Rises. When the DC bus voltage Vdc becomes the DC bus voltage stall level Vdc1 (p12), the output frequency f is stopped for the time t1 to prevent an overvoltage trip. By stopping the output frequency f, the DC bus voltage Vdc decreases, and the DC bus voltage stall level Vdc
Since it becomes 1 or less, the deceleration command can be executed again (p13).

FIG. 6 is a diagram showing an operation when a conventional variable speed device is used under a load condition where regenerative energy at bottom dead center is large, such as a press machine. In the figure,
f is an output frequency, Vdc is a DC bus voltage, Vdc1 is a DC bus voltage stall level, Vdc2 is a DC bus voltage overvoltage level, and t1 is a stop time for stopping output of the output frequency f.

The output frequency f is lowered by a deceleration command (p2
1) When the induction motor 37 is decelerated, the DC bus voltage Vdc increases due to regenerative energy from the induction motor 37. When the DC bus voltage Vdc becomes the DC bus voltage stall level Vdc1 (p22), the regenerative energy from the induction motor 37 is large even if the process of stopping the output frequency f is performed as in FIG. However, the DC bus voltage Vdc rises to the DC bus voltage overvoltage level Vdc2 without lowering (p23), and the variable speed device can only be tripped by the overvoltage, and the operation cannot be continued. For this reason, conventionally, there has been a problem that a regenerative braking device that consumes regenerative energy by a regenerative braking resistor or a regenerative braking device that regenerates regenerative energy to a power source must be provided.

Further, as a technique for providing an inverter device capable of processing the regenerative energy of a load without providing a special regenerative energy processing device such as a dynamic braking device or a regenerative braking device, There is one described in JP-A- 8-126366 . It detects the output current of the inverter, converts the output current into coordinates, separates it into a torque current component and an excitation current component,
When the detected value of the torque current component when the load is in the regenerative state becomes equal to or more than the reference value, the output frequency of the main circuit of the inverter is increased to reduce the regenerative energy. Further, the torque component is detected by multiplying the torque current component by the exciting current component or the exciting current command value. When the load component is in a regenerative state and the detected value of the torque component exceeds a reference value, the regenerative energy is calculated. In order to reduce this, the output frequency of the inverter is increased.

[0008]

SUMMARY OF THE INVENTION Japanese Patent Application Laid- Open No. Hei 8-12636
Japanese Patent Application Laid-Open No. 6-64,087 discloses an inverter device capable of processing regenerative energy of a load without providing a special regenerative energy processing device such as a dynamic braking device or a regenerative braking device. Because the torque current component or torque component indirectly acting on the control of the DC bus voltage is handled, the reference value to be compared with the detected value of the torque current component when the load is in the regenerative state is set, and the load is regenerated. In setting a reference value to be compared with the detected value of the torque component in the state, it is necessary to grasp the relationship between the DC bus voltage and the torque, and there has been a problem that setting the reference value is difficult.

When a plurality of induction motors are connected to one variable speed device, and when an induction motor having a capacity different from the capacity of the variable speed device is connected, it is more difficult to set the reference value. There was a problem.

[0010]

[0011] The present invention solves the above-mentioned problems.
In the case where a plurality of induction motors are connected to one variable speed device and an induction motor having a capacity different from the capacity of the variable speed device is connected, the output frequency of the main circuit of the inverter is adjusted. It is an object of the present invention to obtain a variable speed device in which a reference value serving as a criterion for increasing the number of slabs can be easily set.

[0012]

A variable speed apparatus according to the present invention comprises: an inverter unit for converting DC power into a variable frequency and variable voltage AC power; a detector for detecting the DC voltage of the DC power; And a control means for controlling an inverter unit, the control means comprising: a control unit configured to control the detected DC voltage value to be lower than a DC bus voltage overvoltage level that causes the variable speed device to trip as an overvoltage. If the output frequency exceeds
The difference between the detected DC voltage value and the reference value is fixed.
It is obtained by multiplying by a proportional gain, and is controlled to increase the output frequency.

[0013]

Further , the reference value can be set as a parameter.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram showing a configuration of a variable speed device according to an embodiment of the present invention.
In the figure, 31 to 35 and 37 are the same as those in FIG. 4 shown in the above-mentioned conventional example, and the description thereof is omitted. Reference numeral 1 denotes a memory for setting a DC bus voltage stall level Vdc0 as a reference value, and reference numeral 2 denotes a CPU as control means for judging data of the current detector 34 or the voltage detector 35 and controlling the inverter 33.

FIG. 2 is a diagram showing an operation when the variable speed device according to one embodiment of the present invention is used under a load condition where regenerative energy at bottom dead center is large, such as a press machine. In the figure, f is the output frequency, Vdc is the DC bus voltage, and Vdc0 is the DC bus voltage overvoltage level Vdc2.
The DC bus voltage stall level is set lower than the DC bus voltage stall level.

The output frequency f is reduced by the deceleration command (p
1) The induction motor 37 is decelerated. At this time, the regenerative energy from the induction motor 37 causes the DC bus voltage Vdc to be reduced.
Rises. When the DC bus voltage Vdc becomes equal to or higher than the DC bus voltage stall level Vdc0 (p2, p4),
The output frequency f is increased to prevent an overvoltage trip. When the output frequency f is increased, the regenerative energy is reduced, and the DC bus voltage Vdc is reduced to become equal to or less than the DC bus voltage stall level Vdc0 (p3,
In p5), the deceleration command is executed again.

FIG. 3 is a flow chart of the CPU 2 in the variable speed device according to one embodiment of the present invention. FIG.
The operation of the variable speed device according to one embodiment of the present invention will be described with reference to FIGS.

In step S11, the voltage detector 35
The DC bus voltage Vdc is taken in. In step S12, DC bus voltage stall level Vdc0 set as a fixed value or a variable value by parameter setting from memory 1.
Read. In step S13, DC bus voltage Vdc is compared with DC bus voltage stall level Vdc0. Here, if Vdc ≦ Vdc0, the process proceeds to step S14, and if Vdc> Vdc0, the process proceeds to step S17.

The DC bus voltage Vd is determined in step S13.
If c is smaller than the DC bus voltage stall level Vdc0, the difference between the target frequency and the output frequency is calculated in step S14 by the following equation. f2 = f1-f Here, f1 is a target frequency, f is an output frequency, and f2 is a determination frequency obtained from a difference between the target frequency and the output frequency.

In step S15, the judgment frequency f2 is 0H
It is determined whether or not it is z. If it is 0 Hz, it is determined that deceleration is completed. If the determination frequency f2 is not 0 Hz, the process proceeds to step S16 to continue the deceleration process (FIG. 2).
P3, p5).

In step S13, the DC bus voltage Vd
If c is equal to or higher than the DC bus voltage stall level Vdc0 (p2, p4 in FIG. 2), the rising output frequency f0 is calculated by the following equation in step S17. Ascending output frequency f0 = Δf × K × ΔV / Vdc0 where Δf is a frequency to be output once, K is a constant, a gain given as a fixed value or a parameter set value, and ΔV is a DC bus voltage and a DC bus voltage. The difference from the stall level (= Vdc−Vdc0).

In step S18, the rising frequency f0 is added to the output frequency f (f ← f + f0), and the output frequency f is output in step S19.

As a result, the output frequency f increases, the regenerative energy is reduced, and the DC bus voltage Vdc decreases.

In the regenerative operation state of the load, when the DC bus voltage rises above a predetermined voltage,
By increasing the output frequency of the variable speed device to reduce the regenerative energy and suppress the increase in the DC bus voltage, the above-described procedure of repeating the above procedure can appropriately deal with the increase in the DC bus voltage Vdc. Stable control is possible without overvoltage trip.

The DC bus voltage stall level Vdc0 is set to a value that does not exceed the DC bus voltage overvoltage level Vdc2 even if the increase in the DC bus voltage Vdc is added during the processing of the flowchart in FIG. Vdc0 <Vdc2−A × ΔVdc Here, ΔVdc is an increase of the DC bus voltage Vdc during one cycle of the processing described above, and A is a constant. In addition, operability can be improved by setting the DC bus voltage stall level Vdc0 as a parameter.

In the above description, the DC bus voltage stall level as a reference value is set in the memory 1 in advance and is read out at the time of the determination processing. However, the setting by an external device such as a machine side board and a sequencer is used. May be.

[0028]

Since the present invention is configured as described above, it has the following effects.

A variable speed apparatus according to the present invention includes an inverter for converting DC power into AC power having a variable frequency and a variable voltage, a detector for detecting the DC voltage of the DC power, and a control for controlling the inverter. Means, the control means, when the detected DC voltage value exceeds a reference value set lower than a DC bus voltage overvoltage level that trips the variable speed device as overvoltage, The output frequency to be raised is directly
Multiplying the difference between the flowing voltage value and the reference value by a constant proportional gain
And the output frequency is controlled to be increased , so that the output frequency to be increased can be easily changed.
When multiple induction motors are connected to one variable speed device,
An induction motor with a capacity different from that of the variable speed device is connected.
In such a case, the adjustment can be easily performed.

[0030]

Also, since the reference value can be set as a parameter, when a plurality of induction motors are connected to one variable speed device, when an induction motor having a capacity different from the capacity of the variable speed device is connected. , The reference value can be easily set.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a variable speed device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation of the variable speed device according to the embodiment of the present invention;

FIG. 3 is a flowchart of a CPU 2 in the variable speed device according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional variable speed device.

FIG. 5 is a diagram showing the operation of a conventional variable speed device.

FIG. 6 is a diagram showing the operation of a conventional variable speed device.

[Explanation of symbols]

1 memory, 2 CPU, 31 converter section,
32 smoothing capacitor, 33 inverter part, 34
Current detector, 35 voltage detector, 36 CPU,
37 Induction motor, R, S, T AC power, U,
V, W AC power, f Output frequency, Vdc DC bus voltage, Vdc0 DC bus voltage stall level, V
dc1 DC bus voltage stall level, Vdc2 DC bus voltage overvoltage level, t1 Stop time for stopping output of output frequency f.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02M 7/72 H02P 7/63

Claims (2)

(57) [Claims] 1. A variable speed control comprising: an inverter for converting DC power into AC power having a variable frequency and a variable voltage; a detector for detecting the DC voltage of the DC power; and control means for controlling the inverter. in the device, the control unit, when the detected DC voltage value, which exceeds a reference value set lower than the DC bus voltage overvoltage level to trip the variable speed device as an overvoltage, increased
The output frequency to be applied is determined by the detected DC voltage value and the
A variable speed apparatus characterized in that a difference from a quasi value is obtained by multiplying the difference by a constant proportional gain to control the output frequency to be increased. 2. The reference value can be set as a parameter.
Variable speed device according to claim 1, characterized in that the the.