JP3456005B2 - Inverter device and control method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for controlling the speed of an AC motor such as an induction motor and a control method thereof.

[0002]

2. Description of the Related Art FIG. 17 is a circuit diagram showing a conventional inverter device. In the figure, 1 is a converter circuit (rectifier circuit) for converting an AC voltage of an AC power supply 9 into a DC voltage.
Is an inverter circuit (inverse conversion circuit) for converting a DC voltage into an AC voltage having a predetermined frequency by turning on / off a switching element at a predetermined timing. 4 is an arithmetic control for controlling the inverter circuit 3. Microcomputer 5 as means is an inverter circuit 3
, A direct current voltage detection circuit for detecting the voltage across the smoothing capacitor 2, a current detector 7 and a current detection circuit 8, which constitute an inverter device 150. . Reference numeral 10 is an induction motor driven by the AC voltage of the inverter circuit 3.

The inverter device 15 configured as described above
The operation when the induction motor 10 is operated at 0 and the DC voltage decreases during acceleration will be described. FIG. 18 is a flowchart showing the operation when the rotation speed of the induction motor 10 is being increased, and FIG. 19 is a flowchart showing the operation when the DC voltage is decreasing. 20
It is a time chart which shows a change when direct-current voltage decreases during acceleration. The flowcharts of FIGS. 18 and 19 are executed at every arbitrary time during rotation of the induction motor. In order to increase the rotation speed of the induction motor 10, the acceleration amount Δf is calculated from the predetermined acceleration time and the elapsed time (step 17
a) The frequency currently output from the inverter device is increased by Δf (step 17b).

When the induction motor 10 has a small power supply capacity,
When attempting to accelerate in a shorter time or a heavier load than a normal load, the inverter device 15
The input current to 0 increases, the voltage drop due to the power supply and the wiring impedance increases, and when the power supply situation is bad even with the same load and the fluctuation of the power supply voltage is large, the DC voltage of the inverter device 150 greatly decreases. . If the DC voltage is too low, normal operation of the inverter device cannot be guaranteed, so the DC voltage value is detected (step 18
a) If the DC voltage value is lower than the undervoltage protection level Vu set higher than the DC voltage value V1 which is the limit of normal operation shown in FIG. 20, the base is shut off and the output of the inverter device is stopped (step 18b). , 18c).

[0005]

Since the conventional inverter device 150 is constructed as described above, when the power supply capacity is small, it is attempted to accelerate the induction motor 10 in a shorter time or at a constant speed. If the load is light, but the application requires fast acceleration (for example, an inverter for a loom), or if you try to accelerate with a heavier load than normal, the power supply situation will be If there is a large fluctuation in the power supply voltage, there is a problem that the undervoltage protection operation is activated due to the decrease in the DC voltage. Further, as a means for detecting the load current and reducing the gradient of the acceleration time when the load current during acceleration exceeds a predetermined value, JP-A-1-252183 and JP-A-4-289 are available.
Although there is one disclosed in Japanese Laid-Open Patent Publication No. 262, since the control by the DC voltage value is not included, the problem for the undervoltage protection operation has not been solved. Further, JP-A-4-289
In the one disclosed in Japanese Patent Laid-Open No. 62-62, the gradient of the acceleration time is increased when the direct current voltage rises, but this is a countermeasure when the load suddenly changes from the power load to the regenerative load. The challenges to operation have not been resolved.

The present invention has been made in order to solve the above problems, and when the power supply voltage fluctuates greatly or is used in a power supply with a small capacity, the operation is stopped by the protection operation due to the undervoltage. It is an object of the present invention to obtain an inverter device and a control method thereof.

[0007]

An inverter device according to the present invention converts an input from an AC power supply into a DC voltage and converts the DC voltage into an AC voltage having a predetermined frequency to control the speed of an AC electric motor. the apparatus detects the direct current voltage, an arithmetic control unit for calculating control the frequency of the AC voltage in response to the detected DC voltage value, at the time of acceleration of the AC motor, the DC voltage, under voltage protection Les
When the first set voltage value set higher than the bell is decreased, the frequency of the alternating voltage is increased until the direct current voltage becomes equal to or higher than the second set voltage value set higher than the first set voltage value. It will stop.

Also, in the control method of the inverter device according to the present invention, the input from the AC power source is converted into a DC voltage, the DC voltage is converted into an AC voltage of a predetermined frequency, and the speed control of the AC motor is performed. Detecting a DC voltage, and including arithmetic control means for arithmetically controlling the frequency of the AC voltage according to the detected DC voltage value, and recovering the DC voltage when the DC voltage decreases below a first set voltage value. A method of controlling an inverter device for performing so-called undervoltage suppression processing, comprising: detecting the DC voltage during acceleration of the AC motor; determining whether the undervoltage suppression processing is being performed; If not being, the DC voltage is, when greater than a first set voltage value provided higher than the undervoltage protection level, the predetermined acceleration time, the elapsed time, frequency of the AC voltage The calculation to determine the DC voltage, when: the first set voltage value, the DC voltage is the first
When the undervoltage suppression process is in progress, the frequency of the AC voltage is stopped from increasing until the voltage becomes equal to or higher than a second set voltage value higher than the set voltage value of When it becomes larger, the frequency of the AC voltage is calculated and determined according to predetermined acceleration time and elapsed time. When the DC voltage is equal to or lower than the second set voltage value, the DC voltage is set to the second set voltage value. Until the above, the step of stopping the rise of the frequency of the AC voltage is included.

Further, in an inverter device for converting an input from an AC power supply into a DC voltage, converting the DC voltage into an AC voltage having a predetermined frequency to control the speed of an AC motor,
Detecting the direct current voltage, within a predetermined time, comprising a calculation control means for calculating and controlling the frequency of the alternating voltage according to the rate of change of the direct current voltage, during acceleration of the alternating current motor, within a predetermined time, When the rate of decrease of the DC voltage reaches the first predetermined value, the rate of decrease of the DC voltage is
The increase of the frequency of the AC voltage is stopped until it becomes smaller than the second predetermined value which is set smaller than the first predetermined value.

Further, when the rate of decrease of the DC voltage reaches a first predetermined value within a predetermined time when the AC motor is accelerated, the rate of decrease of the DC voltage is reduced to the first value. The rate of increasing the frequency of the AC voltage within a predetermined time is decreased until it becomes smaller than a second predetermined value that is set smaller than the predetermined value.

Further, in an inverter device for converting an input from an AC power source into a DC voltage and converting the DC voltage into an AC voltage having a predetermined frequency to control the speed of an AC motor,
Detecting the DC voltage, comprising arithmetic control means for arithmetically controlling the frequency of the AC voltage according to the detected DC voltage value, when accelerating the AC motor, the DC voltage is reduced to a predetermined value, The output current of the inverter device is stored, and when the output current becomes larger than a stored value of the output current, the frequency of the AC voltage increases until the output current decreases to a current value set smaller than the stored value. Is to stop.

In addition, in an inverter device for converting an input from an AC power source into a DC voltage and converting the DC voltage into an AC voltage having a predetermined frequency to control the speed of an AC motor,
Detecting the DC voltage, the arithmetic control means for arithmetically controlling the frequency of the AC voltage according to the detected DC voltage value, the frequency of the AC voltage is preset to a predetermined value according to the DC voltage. Every other time, when the AC motor is accelerated, the rate of increasing the frequency is changed according to the value of the DC voltage that decreases.

Further, the frequency is reduced at a predetermined rate at the stage of stopping the increase of the frequency of the AC voltage.

[0014]

The inverter device according to the present invention comprises means for detecting the DC voltage in the preceding stage of the inverse conversion circuit, reads this DC voltage, judges the acceleration amount of the AC motor, and protects the DC voltage value from undervoltage protection. Set higher than level
If was reduced to the first set voltage value, the arithmetic and control means for stopping the increase of the output frequency until the DC voltage becomes equal to or higher than the second set voltage value provided hysteresis amount greater than the predetermined value, the AC motor It reduces the supply of electric power to the device and suppresses the drop in DC voltage.

Also, in the control method of the inverter device according to the present invention, the input from the AC power supply is converted into DC, the DC voltage is converted into the AC voltage of a predetermined frequency to control the speed of the AC motor, and the DC voltage is converted into the DC voltage. A step of detecting the DC voltage when accelerating the AC motor and determining whether or not undervoltage suppression processing is being performed. And the DC voltage is equal to or less than a first set voltage value provided higher than the undervoltage protection level , the DC voltage is equal to or less than the DC voltage when the undervoltage suppression process is in progress. 2 is less than or equal to the set voltage value of 2, the step of stopping the rise of the frequency of the AC voltage until the DC voltage is equal to or more than the second set voltage value, thereby reducing the DC voltage of the inverter device. To suppress.

Further, it is provided with a means for detecting the direct current voltage in the preceding stage of the inverse conversion circuit, reads this direct current voltage, judges the acceleration amount of the alternating current motor, and at the same time, the rate of decrease of the direct current voltage is the first predetermined value. When the value is reached, the arithmetic control means for stopping the increase of the output frequency until the value becomes smaller than another second predetermined value which is provided smaller than the first predetermined value, Supply is reduced and DC voltage drop is suppressed.

Further, it is provided with a means for detecting a direct-current voltage in the preceding stage of the inverse conversion circuit, reads this direct-current voltage, judges the acceleration amount of the alternating-current motor, and at the same time, the slope at which the direct-current voltage decreases is the first predetermined value. When the value is reached, the calculation control means for decreasing the slope for increasing the output frequency reduces the electric power to the AC motor until it becomes smaller than another second predetermined value which is set smaller than the first predetermined value. The supply of electricity is reduced and the decrease in DC voltage is suppressed.

Further, it is provided with means for detecting a direct current voltage in the preceding stage of the inverse conversion circuit and means for detecting an output current. The direct current voltage is read, the acceleration amount of the alternating current motor is judged, and the direct current voltage is a predetermined value. If the output current at this time is memorized and the output current is reduced to a value smaller than the stored value by only the amount of hysteresis, the arithmetic control means for stopping the increase of the output frequency is applied to the AC motor. It reduces the supply of electric power and suppresses the drop in DC voltage.

Further, there is provided means for detecting a direct current voltage in the preceding stage of the inverse conversion circuit, the direct current voltage is read, the acceleration amount of the alternating current motor is judged, and when the value of the direct current voltage becomes a predetermined value or less. The calculation control means for reducing the inclination of increasing the output frequency according to the value reduces the supply of electric power to the AC motor and suppresses the decrease in the DC voltage.

Further, in the step of stopping the rise of the AC voltage of the inverter device according to each of the first, third and fifth aspects of the invention, the frequency is reduced by a predetermined ratio to thereby increase the frequency of each of the above. The invention operates more efficiently.

[0021]

【Example】

Example 1. Hereinafter, an inverter device according to a first embodiment of the present invention will be described with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. Since the operation of the undervoltage protection is the same as that of FIG. 19 shown in the prior art, the description of this part will be omitted and the operation during acceleration will be described. FIG. 1 is a flowchart showing the operation of the inverter device according to the first embodiment of the present invention. The flowchart of FIG. 1 is assumed to be executed at every arbitrary time during the induction motor 10 is accelerating. Further, FIG. 2 is a diagram showing changes in the DC voltage in the inverter device during acceleration. First, the DC voltage starts to decrease with acceleration, but the acceleration process when the DC voltage is not below the undervoltage suppression level that is the first set voltage value (section a in FIG. 2) will be described. Here, the undervoltage suppression level is a voltage level that is lower than the rectified voltage of the commercial power supply and is higher than the undervoltage protection level by a predetermined value. First, the current DC voltage value is read (step 1a). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 1b). If it is off, go to step 1c. Here, when the undervoltage suppression processing flag is OFF, it is further determined whether or not the DC voltage value is equal to or lower than the DC voltage suppression level. If so, go to Step 1f. If the process proceeds to 1e, the undervoltage suppression processing flag is turned off (step 1e), and the predetermined acceleration time (the time required to reach the target speed) and the elapsed time (the time elapsed from the previous processing to the current processing) are calculated. Acceleration amount Δf
The value obtained by adding is used as the output frequency this time (step 1
g, 1h).

Next, the DC voltage is higher than the undervoltage suppression level →
When changing to the following (point d in FIG. 2), first, the DC voltage value is read (step 1a), and it is determined whether the undervoltage suppression processing flag is on or off. In this case, the previous operation is performed. Since the flag is off, the process proceeds to step 1c.
Here, it is determined whether or not the DC voltage value is below the undervoltage suppression level, but since it is below the undervoltage suppression level, the routine proceeds to step 1f. Next, the undervoltage suppression processing flag is turned on (step 1f), the previous output frequency is set as the current output frequency (step 1i), and the rise of the output frequency is stopped up to the second set voltage at which the DC voltage increases by the hysteresis. . (Section b in FIG. 2)

Next, when the increase of the output frequency is stopped, the direct current voltage increases and becomes equal to or higher than the direct current voltage value which is the second set voltage which is set large by the hysteresis (e in FIG. 2).
Point), the output frequency is restarted again, but since the previous undervoltage suppression processing flag was turned on, the process proceeds to step 1d, and the DC voltage value becomes larger than the value obtained by adding the hysteresis amount to the undervoltage suppression level. 1e, the undervoltage suppression processing flag is turned off, and the acceleration amount Δf is calculated from the predetermined acceleration time and elapsed time (step 1
e, 1g), and the acceleration amount Δf is added to the previously output frequency (step 1h) to restart the frequency increase as the current output frequency. (Section c in FIG. 2) Therefore, the value of the hysteresis is a value in which the DC voltage decreases again when acceleration is resumed, but does not fall to the undervoltage protection suppression level again during the software control cycle time. Make settings so that vibration is not applied to the load by repeating acceleration stop → restart. As described above, the power supply to the induction motor is reduced when the DC voltage drops during acceleration without increasing the number of parts, and the DC voltage is prevented from falling below a predetermined value. Can be used efficiently.

Example 2. An inverter device according to a second embodiment of the present invention will be described with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. Since the operation of the undervoltage protection is the same as that of FIG. 19 shown in the prior art, the description of this part will be omitted and the operation during acceleration will be described. FIG. 3 is a flowchart showing the operation of the inverter device according to the second embodiment of the present invention. The flow chart of FIG. 3 shows the induction motor 1
0 shall be executed at some arbitrary time during acceleration. Further, FIG. 4 is a diagram showing changes in the DC voltage in the inverter device during acceleration. In FIG. 4, a certain time ta ← → tb, tb ← → tc, tc ← → t
The time differences between d are all the same and are denoted by Δt. First, the DC voltage starts to decrease with acceleration, but the ratio x1 of the change in the DC voltage that decreases during a predetermined time Δt from a certain time ta to a certain time tb in FIG. 4 is smaller than the first predetermined value A. The acceleration process when the value is small (point a in FIG. 4) will be described. First, the current DC voltage value is read (step 3a). Next, the change rate of the DC voltage is calculated from the previous DC voltage value, the current DC voltage value, and the elapsed time (step 3j). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 3).
b). If it is off, proceed to step 3k. Here, when the undervoltage suppression processing flag is OFF, further step 3j
It is judged whether or not the rate of change of the DC voltage calculated in step 3 is a predetermined first predetermined value A or more (step 3k). If it is not A or more, go to step 3e. If it is A or more, go to step 3f. When the process proceeds to 3e, the undervoltage suppressing process flag is turned off (step 3e), and the value obtained by adding the acceleration amount Δf from the predetermined acceleration time and elapsed time is set as the current output frequency (step 3h).

Next, in FIG. 4, the rate x2 of the change in the DC voltage that decreases during the predetermined time Δt from tb to tc.
Is the first predetermined value A or more (point b in FIG. 4), the DC voltage value is first read (step 3).
a), the ratio of the change in the DC voltage is calculated from the previous DC voltage value, the current DC voltage value, and the elapsed time (step 3).
j). Next, it is determined whether the undervoltage suppression processing flag is on or off. In this case, since the flag was off in the previous operation, the process proceeds to step 3k. Here, it is determined whether the inclination calculated in step 3j is equal to or larger than a predetermined inclination A (step 3k). If it is equal to or larger than A, the process proceeds to step 3f.
Then, the undervoltage suppression processing flag is turned on, the previous output frequency is set as the current output frequency, and the change rate of the DC voltage is set to be smaller than the first predetermined value A. The increase of the output frequency is stopped until the value becomes B or less. (Section b in FIG. 4)

Next, when the increasing rate of the output frequency is stopped and the changing rate of the decreasing DC voltage becomes equal to or less than the second predetermined value B (point c in FIG. 4), the output frequency is again set. In the case of resuming the increase of the voltage, the process proceeds to processing step 3l when the undervoltage suppression processing flag is turned on last time, and the changing rate of the decreasing DC voltage value becomes smaller than the second predetermined value B, so the processing proceeds to processing step 3e. , The undervoltage suppression processing flag is turned off, and the acceleration amount Δf is calculated from the predetermined acceleration time and elapsed time.
Is calculated (steps 3e and 3g), and the acceleration amount Δf is added to the previously output frequency (step 3h) to start the frequency increase again as the current output frequency (section c in FIG. 4). From the above, without increasing the number of parts, the DC voltage changes according to the rate of decrease of the DC voltage during acceleration.
There is an effect that the power supply to the induction motor 10 is reduced before the undervoltage protection operation level is reached, and the inverter device 150 that does not perform the undervoltage protection operation is obtained.

Example 3. The third embodiment of the present invention will be described below with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. still,
The operation of the undervoltage protection is shown in FIG.
Since this is the same as the above, the description of this part will be omitted and the operation during acceleration will be described. FIG. 5 is a flowchart showing the operation of the inverter device 150 according to the third embodiment of the present invention. FIG. 6 is a diagram showing changes in the DC voltage in the inverter device 150. The flowchart of FIG. 5 is assumed to be executed at every arbitrary time during the acceleration of the induction motor 10. Now, the DC voltage in the inverter device 150 begins to decrease with acceleration, but at a certain time ta in FIG.
The acceleration process in the case where the rate of change of the DC voltage that decreases during the predetermined time Δt from t to tb is smaller than the first predetermined value A (point a in FIG. 6) will be described. First, the current DC voltage value is read (step 5a). Next, the rate of change in the DC voltage is calculated from the previous DC voltage value, the current DC voltage value, and the elapsed time (step 5j). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 5b). If it is off, proceed to step 5k. Here, when the undervoltage suppression flag is OFF, it is further determined whether the rate of change in the DC voltage calculated in step 5j is equal to or higher than the first predetermined value A (step 5k). Go to step 5e, and if A or more, go to step 5f. If the rate of change of the DC voltage is not more than A, the undervoltage suppression processing flag is turned off (step 5e), and the value obtained by adding the acceleration amount Δf from the predetermined acceleration time and elapsed time is set as the current output frequency ( Step 5h).

Next, referring to FIG. 6, a certain time tb to tc
It is when the rate of change of the DC voltage that decreases with respect to the predetermined time Δt reaches up to the first predetermined value A (point b in FIG. 6). First, the DC voltage value is read ( In step 5a), the slope of the change in the DC voltage is calculated from the DC voltage values of the previous time and this time (step 5j). Next, it is determined whether the undervoltage suppression processing flag is on or off. In this case, since the flag was off in the previous operation, the process proceeds to step 5k. Here, it is determined whether the change rate of the DC voltage calculated in step 5j is equal to or larger than the first predetermined value A (step 5k). Since the change rate of the DC voltage is equal to or larger than A, the process proceeds to step 5f. . Here, the undervoltage suppression processing flag is turned on (step 5f), the acceleration amount Δf is calculated from the acceleration time set longer than the predetermined acceleration time and the elapsed time (step 5m), and the acceleration amount Δf is set to the previous output frequency.
Is used as the output frequency of this time, and the change rate of the decreasing DC voltage is reduced until the rate of change of the DC voltage becomes smaller than another second predetermined value B which is set smaller than the first predetermined value A. The rate of increase in frequency is reduced (section b in FIG. 6).

Next, by decreasing the increasing rate of the output frequency, the decreasing rate of the DC voltage becomes smaller than the second predetermined value B (point c in FIG. 6), and the increasing rate of the output frequency is changed again. In the case of returning to the original state, the process proceeds to processing step 5l when the undervoltage suppression processing flag is turned on last time, and since the changing rate of the decreasing DC voltage value becomes smaller than the second predetermined value B, the processing step 5e is performed. By proceeding to turn off the undervoltage suppression processing flag, calculate the acceleration amount Δf from the predetermined acceleration time and elapsed time (steps 5e, 5g), and add the acceleration amount Δf to the previously output frequency (step 5h). The frequency starts increasing again as the current output frequency (section c in FIG. 6). From the above, without increasing the number of parts, the DC voltage gradually decreases according to the rate of decrease of the DC voltage during acceleration before the DC voltage drops to the undervoltage protection operation level, and the undervoltage protection operation is performed. It is possible to obtain an inverter device that does not have such a problem, and it is effective to use the inverter device efficiently because the time to reach the target frequency is reached quickly.

Example 4. Embodiment 4 of the present invention will be described below with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. still,
The operation of the undervoltage protection is shown in FIG.
Since this is the same as the above, the description of this part will be omitted and the operation during acceleration will be described. FIG. 7 is a flowchart showing the operation of the inverter device 150 according to the fourth embodiment of the present invention. FIG. 8 is a diagram showing changes in the DC voltage and the output current in the inverter device 150. The flowchart of FIG. 7 is assumed to be executed at every arbitrary time during the induction motor 10 is accelerating. Now, the DC voltage in the inverter device 150 starts to decrease with acceleration and the output current starts to increase, but the acceleration process in the case where the DC voltage in FIG. 8 is larger than a certain predetermined voltage value (section a in FIG. 8) will be described. To do. Here, the undervoltage suppression level is lower than the rectified voltage of the commercial power source and is a predetermined value from the undervoltage protection level,
Use a large voltage level. First, the current DC voltage value is read (step 7a). Next, the current output current value is read (step 7s). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 7b). If it is off, go to step 7c. Here, when the undervoltage suppression processing flag is OFF, it is further determined whether or not the DC voltage value is equal to or lower than the DC voltage suppression level.
If the voltage is below the undervoltage suppression level, the process proceeds to step 7o. Here, when the process proceeds to 7e, the undervoltage suppressing process flag is turned off (step 7e), and the value obtained by adding the acceleration amount Δf calculated from the predetermined acceleration time and the elapsed time is set as the current output frequency (step 7g). , 7h).

Next, referring to FIG. 8, when the DC voltage in the inverter device 150 changes from a predetermined voltage value to a predetermined voltage value or more (point a in FIG. 8), the DC voltage value is first read (step 7a). It is determined whether the preset undervoltage suppression processing flag is on or off (step 7).
b). In this case, since the flag has been turned off in the previous operation, the process proceeds to step 7c. Here, it is determined whether the DC voltage value is equal to or lower than the undervoltage suppression level. If it is equal to or lower than the undervoltage suppression level, the process proceeds to step 7o. The output current value read in here is stored, then the undervoltage suppression processing flag is turned on, the previous output frequency is set as the current output frequency, and the current for the given hysteresis is calculated from the stored output current. The increase of the output frequency is stopped until the current value is subtracted (section b in FIG. 8).

Next, by stopping the increase of the output frequency, when the output current decreases below the current value obtained by subtracting a certain amount of hysteresis current from the stored output current value, the increase of the output frequency is restarted again. In some cases (b in FIG. 8)
Point), the previous undervoltage suppression processing flag is turned on and step 7
If the current output current value is less than or equal to the current value obtained by subtracting the hysteresis from the output current memory value, the process proceeds to step 7e. If not, the process proceeds to step 7f. Since the output current value is the value obtained by subtracting the amount of hysteresis, the process proceeds to step 7e, the undervoltage suppression processing flag is turned off (step 7e), the acceleration amount Δf is calculated from the predetermined acceleration time and elapsed time, and the previous value is calculated. The value obtained by adding the acceleration amount Δf to the output frequency is set as the current frequency (steps 7g and 7h), and the frequency starts to increase again (section c in FIG. 8). As described above, at the time of accelerating the induction motor, more than the electric power corresponding to the capacity of the power supply is not supplied to the induction motor, so that there is an effect that the decrease in the DC voltage is suppressed and the inverter device that does not perform the undervoltage protection operation is obtained.

Example 5. Embodiment 5 of the present invention will be described below with reference to the drawings. The circuit configuration and the undervoltage protection operation are the same as in the conventional example, and the description thereof will be omitted and the operation during acceleration will be described. FIG. 9 is a flowchart showing the operation of the inverter device 150 according to the fifth embodiment of the present invention. Figure 9
It is assumed that the flowchart of 1 is executed at every arbitrary time during the induction motor 10 is accelerating. Further, FIG. 10 is a diagram showing changes in the operating frequency with respect to changes in the DC voltage in the inverter device 150 during acceleration. As shown in FIG. 10, the rate of increasing the frequency with respect to the DC voltage level, that is, the acceleration is set to an arbitrary value in advance. Normally, when the DC voltage drops, the acceleration is increased by α1>α2>α3> α4 in order to reduce the power supplied to the load.
Set as follows. Now, the sequential operation will be described. First, the DC voltage begins to decrease with acceleration,
The acceleration process when the DC voltage is higher than the undervoltage suppression level V _A (section a in FIG. 10) will be described. First, the current DC voltage value is read (step 9a). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 9b). If it is off, the process proceeds to step 9c. Here, when the undervoltage suppression processing flag is OFF, it is further determined whether or not the DC voltage value is equal to or lower than the DC voltage suppression level. If so, the process proceeds to step 9f. If the process proceeds to 9e, the undervoltage suppression processing flag is turned off (step 9e), and the value obtained by adding the acceleration amount Δf from the acceleration α1 and the elapsed time is set as the current output frequency (step 9h).

Next, the DC voltage is higher than the undervoltage suppression level →
When changing to the following (point c in FIG. 10), first, the DC voltage value is read (step 9a), and it is determined whether the undervoltage suppression processing flag is on or off. In this case, the previous operation is performed. Since the flag is off, the process proceeds to step 9c. Here, it is determined whether the DC voltage value is equal to or lower than the undervoltage suppression level V _A, but if it is equal to or lower than the undervoltage suppression level, the process proceeds to step 9f. Next, turn on the undervoltage suppression processing flag,
The process is executed to achieve the acceleration α2 set in advance (step 9p). Further, when the DC voltage becomes V _C or V _D or less, the acceleration is changed by the same route (section b in FIG. 10). Next, when the load becomes lighter at a certain time t4, the DC voltage increases as shown by the dotted line. t
When the DC voltage becomes V _C or more at 5, the acceleration returns to α2. As described above, if the DC voltage decreases during acceleration without increasing the number of parts, the power supplied to the induction motor is reduced according to the decreased value, and the effect of providing an inverter device that does not operate undervoltage protection is obtained. is there.

Example 6. Embodiment 6 of the present invention will be described below with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. still,
The operation of the undervoltage protection is shown in FIG.
Since this is the same as the above, the description of this part will be omitted and the operation during acceleration will be described. FIG. 11 is a flowchart showing the operation of the inverter device 150 according to the sixth embodiment of the present invention. The flowchart of FIG. 11 is assumed to be executed at every arbitrary time during the acceleration of the induction motor 10. Further, FIG. 12 is a diagram showing changes in the DC voltage in the inverter device 150 during acceleration. First, the DC voltage begins to decrease with acceleration, but when the DC voltage is not below the undervoltage suppression level that is the first set voltage value (see FIG. 1).
The acceleration process in the section 2a) will be described. here,
The undervoltage suppression level is a voltage level that is lower than the rectified voltage of the commercial power supply and is higher than the undervoltage protection level by a predetermined value. First, read the current DC voltage value (Step 1
1a). Next, it is determined whether the preset undervoltage suppression processing flag is on or off (step 11).
b). If it is off, the process proceeds to step 11c. Here, when the undervoltage suppression processing flag is OFF, it is further determined whether or not the DC voltage value is equal to or lower than the DC voltage suppression level. If so, the process proceeds to step 11f. When the process proceeds to 11e, the undervoltage suppression processing flag is turned off (step 11e), and the value obtained by adding the acceleration amount Δf from the predetermined acceleration time and elapsed time is set as the current output frequency (step 11h).

Next, the DC voltage is higher than the undervoltage suppression level →
When changing to the following (point d in FIG. 12), first, the DC voltage value is read (step 11a), and it is determined whether the undervoltage suppression processing flag is on or off. In this case, the previous operation is performed. Since the flag is off, the process proceeds to step 11c. Here, it is determined whether or not the DC voltage value is below the undervoltage suppression level. If it is below the undervoltage suppression level, step 1
Go to 1f. Next, the undervoltage suppression processing flag is turned on (step 11f), and the deceleration amount Δf is calculated from the predetermined deceleration time and the elapsed time (step 11q). Then, Δf is subtracted from the previous output frequency to obtain the current output frequency (step 11r), and the output frequency is reduced to the second set voltage at which the DC voltage increases by the hysteresis (FIG. 12).
Section b).

Next, when the output voltage is decreased and the direct current voltage is increased and becomes equal to or higher than the direct current voltage value which is the second set voltage which is set large by the hysteresis (e in FIG. 12).
Point), the output frequency is restarted again. Since the previous undervoltage suppression processing flag is turned on, the process proceeds to step 11d, and the DC voltage value becomes larger than the value obtained by adding the hysteresis component to the undervoltage suppression level. 11
In step e, the undervoltage suppression processing flag is turned off, the acceleration amount Δf is calculated from the predetermined acceleration time and the elapsed time (steps 11e and 11g), and the acceleration amount Δf is added to the previously output frequency (step 11h) As the output frequency this time, the frequency starts to increase again (section c in FIG. 12). As described above, without increasing the number of parts, when the DC voltage decreases during acceleration, the electric power supplied to the induction motor is reduced by quickly reducing the slip of the induction motor, and the DC voltage is suppressed from falling below a predetermined value. There is an effect that an inverter device that does not perform an undervoltage protection operation is obtained.

Example 7. Embodiment 7 of the present invention will be described with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. Since the operation of the undervoltage protection is the same as that of FIG. 19 shown in the prior art, the description of this part will be omitted and the operation during acceleration will be described. FIG. 13 is a flowchart showing the operation of the inverter device 150 according to the seventh embodiment of the present invention. The flowchart of FIG. 13 is assumed to be executed at every arbitrary time during the induction motor 10 is accelerating. Also,
FIG. 14 is a diagram showing changes in the DC voltage in the inverter device 150 during acceleration. In FIG. 14, the time differences between certain times ta ← → tb, tb ← → tc, and tc ← → td are all the same, and are set to Δt. First, the DC voltage starts to decrease with acceleration, but the changing rate x1 of the DC voltage that decreases during a predetermined time Δt from a certain time ta to a certain time tb in FIG. 14 is smaller than a first predetermined value A. The acceleration process in the case (point a in FIG. 14) will be described. First, the current DC voltage value is read (step 13a). Next, the slope of the change in the DC voltage is calculated from the previous DC voltage value, the current DC voltage value, and the elapsed time (step 13j). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 1
3b). If it is off, the process proceeds to step 13k. here,
When the undervoltage suppression processing flag is OFF, it is further determined whether or not the rate of change in the DC voltage calculated in step 13j is equal to or higher than a first predetermined value A (step 13k), and if not equal to or higher than A, proceed to step 13e. , A or more, proceed to Step 13f. If the process proceeds to 13e, the undervoltage suppressing process flag is turned off (step 13e), and the value obtained by adding the acceleration amount Δf from the predetermined acceleration time and elapsed time is set as the current output frequency (step 13h).

Next, in FIG. 14, the changing rate x of the DC voltage which decreases during a predetermined time Δt from tb to tc
2 becomes larger than the first predetermined value A (see FIG. 4).
As for point b), first, the DC voltage value is read (step 13a), and the rate of change of the DC voltage is calculated from the previous DC voltage value, the current DC voltage value, and the elapsed time (step 13j). Next, it is determined whether the undervoltage suppression processing flag is on or off. In this case, since the flag was off in the previous operation, the process proceeds to step 13k. Step 1 here
It is judged whether the rate of change of the DC voltage calculated in 3j is equal to or larger than the first predetermined value A (step 13k).
If it is A or more, proceed to Step 13f. Then, the undervoltage suppression processing flag is turned on, the subtraction amount Δf is calculated from the predetermined deceleration time and the elapsed time (step 13q), and the subtraction amount Δf is subtracted from the previous output frequency to obtain the current output frequency, and then decrease. The output frequency is reduced until the rate of change of the DC voltage becomes equal to or less than another second predetermined value B which is set smaller than the first predetermined value A (section b in FIG. 14).

Next, by decreasing the output frequency, when the changing rate of the decreasing DC voltage becomes equal to or less than the second predetermined value B (point c in FIG. 14), the output frequency is changed again. In the case of restarting the increase, the process proceeds to step 13l when the undervoltage suppression processing flag is turned on last time, and since the rate of decrease of the DC voltage value becomes smaller than the second predetermined value B, the process proceeds to step 13e to suppress the undervoltage. The in-process flag is turned off, the acceleration amount Δf is calculated from the predetermined acceleration time and the elapsed time (steps 13e and 13g), and the acceleration amount Δf is added to the previously output frequency (step 13h) to obtain the current output frequency. The frequency starts increasing again. (Section c in FIG. 14) As described above, without increasing the number of parts, the DC voltage quickly reduces the slip of the induction motor before the DC voltage falls to the undervoltage protection operation level according to the rate of decrease of the DC voltage during acceleration. As a result, the power supplied to the induction motor can be reduced, and an inverter device that does not easily perform the undervoltage protection operation can be obtained.

Example 8. Embodiment 8 of the present invention will be described with reference to the drawings. Since the circuit configuration is the same as that of the conventional example, the description thereof will be omitted and only the operation will be described. Since the operation of the undervoltage protection is the same as that of FIG. 19 shown in the prior art, the description of this part will be omitted and the operation during acceleration will be described. FIG. 15 is a flowchart showing the operation of the inverter device 150 according to the eighth embodiment of the present invention. FIG. 16 is a diagram showing changes in the DC voltage and the output current in the inverter device 150. The flowchart of FIG. 15 is assumed to be executed at every arbitrary time during the induction motor 10 is accelerating. Now, the inverter device 150
Although the DC voltage in the inside begins to decrease with acceleration and the output current starts to increase, the acceleration process when the DC voltage in FIG. 16 is higher than a predetermined voltage value (section a in FIG. 16) will be described. Here, the undervoltage suppression level is a voltage level that is lower than the rectified voltage of the commercial power supply and is higher than the undervoltage protection level by a predetermined value. First, the current DC voltage value is read (step 15a). Next, the current output current value is read (step 15s). Next, it is determined whether a preset undervoltage suppression processing flag is on or off (step 15b). If it is off, the process proceeds to step 15c. Here, when the undervoltage suppression processing flag is OFF, it is further determined whether or not the DC voltage value is equal to or lower than the DC voltage suppression level. If so, go to step 15o. If the process proceeds to 15e, the undervoltage suppressing process flag is turned off (step 15e), and the value obtained by adding the acceleration amount Δf calculated from the predetermined acceleration time and the elapsed time is set as the current output frequency (steps 15g, 15).
h).

Next, referring to FIG. 16, the inverter device 150
It is the time when the DC voltage in the inside changes from a predetermined voltage value to a value lower than or equal to a predetermined voltage value (point a in FIG. 16). First, the DC voltage value is read (step 15a), and a preset undervoltage suppression flag is set. It is determined whether is ON or OFF (step 15b). In this case, since the flag has been turned off in the previous operation, the process proceeds to step 15c. Here, it is determined whether the DC voltage value is equal to or lower than the undervoltage suppression level. If it is equal to or lower than the undervoltage suppression level, the process proceeds to step 15o. The output current value read here is stored, then the undervoltage suppression processing flag is turned on, and the subtraction amount Δ is subtracted from the predetermined deceleration time and elapsed time.
f is calculated (step 15q), the subtraction amount Δf is subtracted from the previous output frequency to obtain the current output frequency, and the output current is reduced to a current value obtained by subtracting a predetermined hysteresis current from the stored output current. The output frequency is decreased to (section b in FIG. 16).

Next, when the output frequency is reduced to a value equal to or less than the current value obtained by subtracting a predetermined hysteresis current from the stored output current value, the increase of the output frequency is restarted. But (b in FIG. 16)
Point), the process proceeds to processing step 15n when the undervoltage suppression processing flag is turned on last time, and proceeds to step 15e if the current output current value is less than or equal to the current value obtained by subtracting the hysteresis from the output current memory value, otherwise proceeds to step 15f. Go to. Since the output current value is the value subtracted by the hysteresis, the process proceeds to step 15e, the undervoltage processing flag is turned off (step 15e), the acceleration amount Δf is calculated from the predetermined acceleration time and elapsed time, and the previous output frequency is set. Acceleration amount Δf
The value obtained by adding is the frequency of this time (step 15g, 1
5h), the frequency starts to increase again (section c in FIG. 16). As described above, at the time of accelerating the induction motor, more than the power corresponding to the power supply capacity is not supplied to the induction motor, so that it is possible to obtain the inverter device in which the decrease in the DC voltage is suppressed and the undervoltage protection operation is hard to occur.

[0044]

As described above, according to the present invention, when the acceleration of the AC motor is judged and the DC voltage value becomes insufficient.
When the first set voltage value set higher than the pressure protection level is decreased, the increase of the output frequency is stopped until the DC voltage becomes equal to or higher than the second set voltage value set by a hysteresis larger than the predetermined value. With this configuration, the power supply to the AC motor is reduced when the DC voltage drops during acceleration without increasing the number of parts, and it is possible to suppress the DC voltage from dropping below a predetermined value, and to prevent the undervoltage protection operation from occurring. The device can be used efficiently.

In addition, the rate at which the DC voltage decreases when the acceleration of the AC motor is judged by the arithmetic control means is the first
When the predetermined value of is reached, the increase in the output frequency is stopped until it becomes smaller than the second predetermined value which is smaller than the first predetermined value. Without increasing the DC voltage during acceleration, the DC voltage is reduced according to the rate of decrease of the DC voltage before it falls to the undervoltage protection operation level, and the inverter device that does not operate undervoltage protection is obtained. It is effective.

Further, the rate at which the DC voltage decreases when the acceleration of the AC motor is judged by the arithmetic control means is the first
When the predetermined value of is reached, the ratio of increasing the output frequency is reduced until it becomes smaller than the second predetermined value which is set smaller than the first predetermined value. It is possible to operate the undervoltage protection operation by gradually reducing the power supply to the AC motor before the DC voltage falls to the undervoltage protection operation level according to the rate of decrease of the DC voltage during acceleration without increasing the number of parts. Since it is possible to obtain an inverter device which does not exist and it takes time to reach the target frequency, it is possible to effectively use the inverter device.

Further, when the calculation control means determines the acceleration of the AC motor and the DC voltage value decreases to a predetermined value, the output current at this time is stored, and the output current is only the hysteresis portion from this stored value. Since it is configured to stop the rise of the output frequency until it decreases to a small value,
Since more than the electric power corresponding to the power supply capacity is not supplied to the AC motor at the time of acceleration, there is an effect that an inverter device can be obtained which suppresses a decrease in DC voltage and does not perform an undervoltage protection operation.

Further, the arithmetic and control unit determines whether or not the AC motor is accelerated, and when the value of the DC voltage becomes equal to or lower than a predetermined value, the rate of increasing the output frequency is reduced according to the value. Therefore, if the DC voltage decreases at the time of acceleration without increasing the number of parts, there is an effect that the power supply to the AC motor is decreased according to the decreased value, and the inverter device that does not perform the undervoltage protection operation is obtained.

Further, when the undervoltage suppression process is performed, the output frequency is configured to be reduced at a predetermined rate. Therefore, when the DC voltage decreases during acceleration, the slip of the AC motor can be quickly reduced without increasing the number of parts. There is an effect that the inverter device that reduces the power supplied to the AC motor, suppresses the DC voltage from falling below a predetermined value, and does not perform the undervoltage protection operation is obtained.

[Brief description of drawings]

FIG. 1 is an operation flowchart of an inverter device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing changes in the DC voltage and the output frequency of the inverter device according to the first embodiment of the present invention.

FIG. 3 is an operation flowchart of an inverter device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing changes in a DC voltage and an output frequency of an inverter device according to a second embodiment of the present invention.

FIG. 5 is an operation flowchart of the inverter device according to the third embodiment of the present invention.

FIG. 6 is a diagram showing changes in a DC voltage and an output frequency of an inverter device according to a third embodiment of the present invention.

FIG. 7 is an operation flowchart of the inverter device according to the fourth embodiment of the present invention.

FIG. 8 is a diagram showing changes in DC voltage, output current, and output frequency of the inverter device according to the fourth embodiment of the present invention.

FIG. 9 is an operation flowchart of the inverter device according to the fifth embodiment of the present invention.

FIG. 10 is a diagram showing changes in a DC voltage and an operating frequency of an inverter device according to a fifth embodiment of the present invention.

FIG. 11 is an operation flowchart of the inverter device according to the sixth embodiment of the present invention.

FIG. 12 is a diagram showing changes in DC voltage and output frequency of an inverter device according to a sixth embodiment of the present invention.

FIG. 13 is an operation flowchart of the inverter device according to the seventh embodiment of the present invention.

FIG. 14 is a diagram showing changes in DC voltage and output frequency of an inverter device according to a seventh embodiment of the present invention.

FIG. 15 is an operation flowchart of the inverter device according to the eighth embodiment of the present invention.

FIG. 16 is a diagram showing changes in the DC voltage, the output current, and the output frequency of the inverter device according to the eighth embodiment of the present invention.

FIG. 17 is a circuit diagram showing a configuration of a conventional inverter device.

FIG. 18 is a flowchart of an acceleration process of a conventional inverter device.

FIG. 19 is a flowchart for determining an undervoltage in a conventional inverter device.

FIG. 20 is a diagram showing changes in DC voltage and operating frequency during acceleration of a conventional inverter device.

[Explanation of symbols]

1 converter circuit 2 Smoothing capacitor 3 inverter circuit 4 Microcomputer (arithmetic control means) 5 Bass amplifier 6 DC voltage detection circuit 7 Current detector 8 Current detection circuit 9 AC power supply 10 induction motor 150 inverter device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Arihiro Kozai 5107-1071, Kamiodai Sone-machi, Kita-ku, Nagoya City Mitsubishi Electric Engineering Co., Ltd., Nagoya Works (72) Inventor Tomokazu Kimura Higashi-odae, Kita-ku, Nagoya City Machigami 5-chome 1071 Mitsubishi Electric Engineering Co., Ltd., Nagoya Works (56) Reference JP-A-4-340396 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02P 5 / 408-5/412 H02P 7/628-7/632 H02P 21/00 H02P 5/00 H02P 7/00-7/01 H02P 1/00-1/58

Claims (7)

(57) [Claims] 1. An inverter device for converting an input from an AC power supply into a DC voltage, converting the DC voltage into an AC voltage of a predetermined frequency to control the speed of an AC motor, and detecting and detecting the DC voltage. Comprising arithmetic control means for arithmetically controlling the frequency of the AC voltage according to the DC voltage value,
During acceleration of the AC motor, the DC voltage, undervoltage
When the first set voltage value set higher than the protection level is reduced, the frequency of the alternating voltage increases until the direct current voltage becomes equal to or higher than the second set voltage value set higher than the first set voltage value. An inverter device characterized by stopping. 2. An input from an AC power supply is converted into a DC voltage, the DC voltage is converted into an AC voltage of a predetermined frequency to control the speed of an AC motor, the DC voltage is detected, and the detected DC voltage value is detected. an arithmetic control unit for calculating control the frequency of the AC voltage in response to the DC voltage, insufficient electrodeposition
A method for controlling an inverter device, which performs a so-called undervoltage suppression process of recovering the DC voltage when the voltage is reduced to a first set voltage value higher than a pressure protection level or lower,
Detecting the DC voltage when accelerating the AC motor, and determining whether the undervoltage suppression process is being performed;
If not in undervoltage suppression process, the DC voltage, when said <br/> greater than a first set voltage value, a predetermined acceleration time, the elapsed time, calculates the frequency of the AC voltage, determines the DC voltage but when: the first set voltage value, an increase in frequency of the AC voltage is stopped until the DC voltage becomes equal to or higher than the second set voltage value provided higher than the first set voltage value, insufficient In the voltage suppression process, when the DC voltage becomes larger than the second set voltage value, the frequency of the AC voltage is calculated based on a predetermined acceleration time and elapsed time.
And a method of controlling the inverter device, which comprises the step of stopping the rise of the frequency of the AC voltage until the DC voltage becomes equal to or higher than the second set voltage value when the DC voltage is equal to or lower than the second set voltage value. . 3. An inverter device for converting an input from an AC power supply into a DC voltage, converting the DC voltage into an AC voltage having a predetermined frequency to control the speed of an AC motor, and detecting the DC voltage to determine a predetermined voltage. In the time period, a calculation control means for calculating and controlling the frequency of the AC voltage according to the rate of change of the DC voltage is provided, and during acceleration of the AC motor, the rate of decrease of the DC voltage within a predetermined time period, When the first predetermined value is reached, the frequency of the AC voltage increases until the rate of decrease of the DC voltage becomes smaller than the second predetermined value that is set smaller than the first predetermined value. An inverter device characterized by stopping. 4. When the AC motor accelerates, when the rate of decrease of the DC voltage reaches a first predetermined value within a predetermined time, the rate of decrease of the DC voltage is changed to the first rate.
4. The rate of increasing the frequency of the AC voltage within a predetermined time is decreased until the frequency becomes smaller than a second predetermined value that is set smaller than the predetermined value of. Inverter device. 5. An inverter device for converting an input from an AC power supply into a DC voltage, converting the DC voltage into an AC voltage of a predetermined frequency to control the speed of an AC motor, and detecting and detecting the DC voltage. Comprising arithmetic control means for arithmetically controlling the frequency of the AC voltage according to the DC voltage value,
When the DC voltage is reduced to a predetermined value during acceleration of the AC motor, the output current of the inverter device is stored, and when the output current becomes larger than the stored value of the output current, the output current is the stored value. An inverter device, characterized in that the increase of the frequency of the AC voltage is stopped until the current value is set to a smaller value. 6. An inverter device for converting an input from an AC power supply into a DC voltage, converting the DC voltage into an AC voltage of a predetermined frequency to control the speed of an AC electric motor, and detecting the DC voltage in the inverter device. However, the AC motor is provided with arithmetic control means for arithmetically controlling the frequency of the AC voltage according to the detected DC voltage value, and the frequency of the AC voltage is preset to a predetermined value according to the DC voltage. The inverter device is characterized in that the rate of increasing the frequency is changed in accordance with the value of the DC voltage that decreases when the acceleration is performed. 7. The inverter according to claim 1, wherein the frequency is decreased at a predetermined rate in the step of stopping the increase of the frequency of the AC voltage. apparatus.