CN101479928B - Inverter control device and its operation method - Google Patents

Abstract

The present invention provides an inverter controller and a method for operating the inverter controller that enable continuous operation during momentary power outages or during regenerative operation without requiring difficult regulation and during overvoltage or undervoltage Depression does not cause tripping or unnecessary torque ripple. An inverter controller (20) equipped with a voltage detection circuit (5) for detecting a terminal voltage of a smoothing capacitor (2) and a speed command selection circuit (6) for detecting a momentary power failure in an AC power supply has A power calculation circuit (36) for calculating its power output and a speed command calculation circuit (7) for calculating a power output target value and a speed command value during momentary power failure.

Description

Inverter controller and method of operation thereof

technical field

The present invention relates to an inverter controller for controlling an AC motor in a variable speed manner, and more particularly, to an inverter controller and a method for operating the inverter controller such that the Capable of continuous operation during electrical periods and capable of handling regenerative energy during deceleration of the AC motor, and the AC motor operates under regenerative load.

Background technique

In the case of the first conventional inverter controller, according to its operation method during momentary power failure, when the terminal voltage (intermediate voltage) of the smoothing capacitor drops to level 1 or lower, the AC motor is decelerated, when due to With regenerative power obtained by deceleration, when the intermediate voltage rises to level 2 or higher, the AC motor accelerates, and then repeats the acceleration/deceleration control according to the increase or decrease of the intermediate voltage as described above, whereby the rate of decrease of the intermediate voltage is reduced (for example, refer to Patent Document 1).

In the case of the second conventional inverter controller, the inverter controller starts deceleration using the power-off detection signal, calculates a deceleration rate 1 based on the target value and the detected value of the DC intermediate voltage so that the DC intermediate voltage becomes Constant, the deceleration rate 2 is calculated based on the rate of change of the DC intermediate voltage, and the deceleration time is controlled by proportionally integrating the value obtained by multiplying these two deceleration rates, whereby when the DC intermediate voltage reaches Deceleration is stopped when the previous voltage or rises during deceleration (for example, refer to Patent Document 2).

In the case of the third conventional inverter controller, when the output frequency decreases and the motor decelerates, the voltage value of the main circuit (corresponding to the terminal voltage value of the smoothing capacitor) rises; according to the detected voltage value of the main circuit The deceleration time of the motor is controlled so that when the voltage detection value is higher than a predetermined first voltage value, the deceleration time is extended, and thus when the voltage detection value reaches a second voltage value higher than the first voltage value, the deceleration is stopped (for example, Refer to Patent Document 3).

In the case of the fourth conventional inverter controller, when the regenerative load is applied during motor operation and the detected DC voltage (corresponding to the terminal voltage value of the smoothing capacitor) exceeds the reference value, by The difference between the DC voltage value and the reference value is multiplied by a constant proportional gain to obtain an output frequency to be raised, and control is performed to raise the output frequency (for example, refer to Patent Document 4).

8 is a view showing the operation of a fourth conventional inverter controller for driving when an AC motor is used, for example, under a load condition in which regenerative energy rises at the bottom dead center of the press machine. The AC motor. In the figure, f represents the output frequency, Vdc represents the DC bus voltage, Vdc0 represents the DC bus voltage stall level, and Vdc2 represents the overvoltage level.

When the output frequency f is reduced (at p1 ) using the deceleration command and the motor is decelerated, the DC bus voltage Vdc is boosted by regenerative energy from the motor. When the DC bus voltage Vdc becomes the DC bus voltage stall level Vdc0 or higher (at p2 and p4), the output frequency f is raised to prevent overvoltage tripping. Since the output frequency f is raised, regenerative energy is lowered; when the DC bus voltage Vdc is lowered and becomes the DC bus voltage stall level Vdc0 or lower (at p3 and p5), the deceleration command is executed again.

In the operation method used for conventional inverter controllers during momentary power failure, by adjusting the speed command or by determining the deceleration rate based on the level of the terminal voltage (intermediate voltage) of the smoothing capacitor or the operation of the power failure detection circuit, for regeneration Operate the drive motor.

Further, in the operation method for the conventional inverter controller when the DC bus voltage is boosted to a predetermined voltage or higher by regenerative energy during deceleration of the AC motor and operation of the AC motor under a regenerative load, the deceleration time is repeatedly extended , Stop the step of decelerating or increasing the output frequency according to the level of the DC bus voltage to suppress the increase of the DC bus voltage, thereby preventing an overvoltage trip.

Patent Document 1: Unexamined Japanese Patent Application Publication No. Hei 6-165579

Patent Document 2: Japanese Patent No. 3201460

Patent Document 3: Japanese Patent No. 3095083

Patent Document 4: Japanese Patent No. 3536695

Contents of the invention

Problem to be solved by the present invention

In the operation method used for the conventional inverter controller, the terminal voltage level of the smoothing capacitor is detected, and the deceleration time and output frequency are controlled according to the voltage level; In the case of a system where the load of an AC motor changes, it is difficult to determine the control quantity of the output frequency; if the change of the output frequency is slow, a trip occurs under undervoltage or overvoltage, or such a problem occurs in which deceleration and acceleration are repeated And generate vibration in the motor. In particular, in the case where the method is applied to a system with low mechanical stiffness or an inverter controller provided with a smoothing capacitor with reduced capacitance, the up/down variation in the DC bus voltage (Vpn) is steep; thus, the above-mentioned problem occurs significantly.

In view of these problems, it is an object of the present invention to provide an inverter controller and a method for operating an inverter controller that enable continuous operation without requiring difficult adjustments, and even when the present invention is implemented In the case of being applied to a system with low mechanical rigidity or an inverter controller provided with a smoothing capacitor with reduced capacitance, it will not occur during momentary power failure or during deceleration of the AC motor and operation of the AC motor under a regenerative load Causes a trip on overvoltage or undervoltage.

The method used to solve the problem

In order to solve the above-mentioned problems, the present invention is configured as described below.

According to one aspect of the present invention, it relates to an inverter controller, comprising:

AC motor as load,

a rectification circuit for converting AC power from an AC power source into DC power,

a smoothing capacitor for smoothing the DC voltage from the rectification circuit,

an inverter circuit for converting the DC power supplied via the smoothing capacitor into a desired frequency,

a current detection circuit for detecting an output current from the inverter circuit,

a voltage detection circuit for detecting the terminal voltage Vpn of the smoothing capacitor,

a speed command calculation circuit that calculates a power-off time speed command used in a case where the AC power supply is judged to be power-off,

an output voltage command calculation circuit that calculates a voltage command to the AC motor based on a power failure detection signal, a normal time speed command, and a power failure time speed command;

Wherein, the speed command calculation circuit includes:

a power calculation circuit, using the output current and the voltage command to calculate a power output value;

a power target calculation circuit that calculates a power output based on (C×Vpnc ² )/2 using the terminal voltage Vpn, a preset target value Vpnc of the terminal voltage at power-off time, and the capacitor capacitance C of the smoothing capacitor target value,

The power-off time speed command is calculated based on the power output target value and the power output value.

According to one aspect of the present invention, it relates to an inverter controller, comprising:

AC motor as load,

a rectification circuit for converting AC power from an AC power source into DC power,

a smoothing capacitor for smoothing the DC voltage from the rectification circuit,

an inverter circuit for converting the DC power supplied via the smoothing capacitor into a desired frequency,

a current detection circuit for detecting an output current from the inverter circuit,

a voltage detection circuit for detecting the terminal voltage Vpn of the smoothing capacitor,

a frequency command calculation circuit for calculating a frequency command used when the terminal voltage Vpn is equal to or greater than a set value,

an output voltage command calculation circuit for use based on whether or not the terminal voltage Vpn is above a set value, a normal time frequency command, and when the terminal voltage Vpn is above a set value of the frequency command to calculate a voltage command to the AC motor,

Wherein, the frequency command calculation circuit includes:

a power calculation circuit, using the output current and the voltage command to calculate a power output value;

The power target calculation circuit uses the terminal voltage Vpn, a preset target value Vpnc of the terminal voltage at the time of overvoltage prevention operation, and the capacitor capacitance C of the smoothing capacitor, according to (C×Vpnc ² )/2 Calculate the power output target value,

The frequency command is calculated based on the power output target value and the power output value.

According to another aspect of the present invention, it relates to an operation method for solving fluctuations or momentary power failures of AC power for an inverter controller, the inverter controller comprising:

AC motor as load;

A rectification circuit for converting AC power from an AC power source into DC power;

a smoothing capacitor for smoothing the DC voltage from the rectification circuit;

an inverter circuit for converting DC power supplied via the smoothing capacitor into a desired frequency;

a current detection circuit for detecting the output current of the inverter;

and a voltage detection circuit for detecting a terminal voltage Vpn of the smoothing capacitor;

a speed command calculation circuit that calculates a power-off time speed command used in a case where the AC power supply is judged to be power-off,

an output voltage command calculation circuit that calculates a voltage command to the AC motor based on a power failure detection signal, a normal time speed command, and a power failure time speed command;

The method of operation comprises the following steps:

calculating a power output value by using the output current and the voltage command;

Using the terminal voltage Vpn, the preset target value Vpnc of the terminal voltage at power-off time, and the capacitor capacitance C of the smoothing capacitor, the power output target value is calculated according to (C×Vpnc ² )/2;

The power-off time speed command is calculated based on the power output target value and the power output value.

Effect of the present invention

Utilize the present invention,

A loop for controlling the power output of the inverter controller is configured inside a loop capable of determining a deceleration command based on the target voltage and the detected voltage along the terminals of the smoothing capacitor 2, and the target value of the terminal voltage of the smoothing capacitor can be rapidly converged .

Furthermore, with the present invention, the power loss value of the inverter controller can be considered, and with the present invention, the power loss value of the machine including the AC motor can be considered; therefore, even in it along the terminals of the smoothing capacitor Even in a state where the target voltage and the detection voltage of the target voltage coincide with each other, smooth deceleration operation can be performed, and unnecessary deceleration stops and decelerations are not repeated.

Furthermore, with the present invention, by limiting the torque target value, excessive torque can be prevented from being generated, thereby enabling the protection of the machine used.

Further, with the present invention, in the case where the AC motor serving as the used load is an induction motor, the difference frequency can be compensated, whereby the delay time until scheduled regenerative power is obtained can be shortened.

Description of drawings

FIG. 1 is a schematic configuration diagram showing the whole of an inverter controller according to a first embodiment of the present invention;

2 is a block diagram of a speed command selection circuit 6 for selecting a speed command during power failure detection according to a first embodiment of the present invention;

FIG. 3 is a block diagram of a speed command calculation circuit 7 according to a first embodiment of the present invention;

Figure 4 is a timing diagram when a power outage occurs;

5 is a schematic configuration diagram showing the whole of an inverter controller according to a second embodiment of the present invention;

FIG. 6 is a block diagram of a sequential circuit 70 according to a second embodiment of the present invention;

FIG. 7 is a block diagram of a frequency command calculation circuit 71 according to a second embodiment of the present invention; and

FIG. 8 is a timing chart illustrating the operation of the related art.

reference sign

1 rectifier circuit

2 smoothing capacitor

3 inverter circuit

4 Current detection circuit

5 voltage detection circuit

6 Speed command selection circuit

7 Speed command calculation circuit

8 Voltage command calculation circuit

9 PWM control circuit

10 base drive circuit

11 Electromagnetic contactor

12 Speed command setter

13 AC motors

20, 20’ inverter controller

21 switch circuit

22 soft starter

23 OR circuit

24 Comparators

25, 31, 32, 61, 62, 63 Coefficient multipliers

34 Energy target value calculation circuit

35 Energy Calculation Circuit

36 power calculation circuit

37, 60 Subtractor

40 Adder-subtractor

49 delay circuit

52 Divider

53 Torque limit circuit

58 difference frequency calculation circuit

59, 64 adder

70 sequential circuit

71 Frequency instruction calculation circuit

72 Frequency command setter

73 switch circuit

74 Comparator

75, 76, 77, 82, 85, 88 coefficient multiplier

78 Energy target value calculation circuit

79 Energy Calculation Circuit

80, 91 Subtractor

81 power calculation circuit

83 Limiting circuit

84 Adder-subtractor

86 divider

87 Torque limit circuit

89, 90 adder

92 difference frequency calculation circuit

93 delay circuit

a power failure detection contact signal

b power-off time speed command

c speed command

d output voltage command

e output current detection

f power failure detection signal

g Usually time speed command

Detailed ways

Embodiments according to the present invention and specific examples of the method according to the present invention will be described based on the drawings.

Example 1

FIG. 1 is a schematic configuration diagram showing the whole of an inverter controller according to the present invention. In Fig. 1, numeral 1 represents a rectifying circuit for converting AC power from an AC power source into DC power, numeral 2 represents a smoothing capacitor for smoothing the DC voltage from rectifying circuit 1, and numeral 3 represents a The DC power supplied by the capacitor 2 is converted into an inverter circuit 3 of a desired frequency, numeral 4 represents a current detection circuit for detecting an output current of the inverter circuit, and numeral 5 represents a circuit for detecting a terminal voltage of the smoothing capacitor 2 A voltage detection circuit, numeral 6 represents a speed command selection circuit for selecting a speed command according to whether a power-off state has occurred, numeral 7 represents a speed command calculation circuit for calculating a speed command during power-off detection, and numeral 8 for An output voltage command calculation circuit that calculates an output voltage command based on a speed command issued from the speed command selection circuit 6, numeral 9 denotes a PWM control for PWM-controlling the inverter circuit 3 based on an output signal from the speed command selection circuit 6 circuit, and numeral 10 denotes a base drive circuit for driving the inverter circuit 3 based on an output signal from the PWM control circuit 9; the inverter controller includes these components.

Numeral 11 denotes an electromagnetic contactor on the AC power supply side, numeral 12 denotes a speed command setter for setting a speed command during normal operation, and numeral 13 denotes an AC motor driven by the output of the inverter circuit 3; these members is connected to the inverter controller 20.

The present invention is different from the prior art in that it provides a speed command selection circuit 6 for selecting a speed command according to whether a power-off state has occurred and a speed command calculation circuit 7 for calculating a power-off time speed command; The circuit 7 is provided with a loop for controlling the power output of the inverter controller 20 inside a loop for determining a deceleration command based on the target voltage Vpnc and the detected voltage Vpn of the smoothing capacitor 2, and is further provided with a circuit for limiting the torque target value. Torque limiting circuit 53 and other circuits.

FIG. 2 is a block diagram of a speed command selection circuit 6 for selecting a speed command according to whether a power-off state has occurred. In Fig. 2, the speed command selection circuit 6 has a switch circuit 21 for setting UV level 1, a soft starter 22, an OR circuit 23, a comparator 24 and a coefficient multiplier 25, and the output signal of the OR circuit 23 is sent to The speed instruction calculation circuit 7, the OR circuit 23 is used to calculate the logic OR of the power-off detection contact signal from the electromagnetic contactor 11 and the output signal of the comparator 24 described later as the power-off detection signal, and, further, to the speed The command calculation circuit 7 and the voltage command calculation circuit 8 send the speed command by starting the switch circuit 21 and by passing through the soft starter 22 at the power-off time speed command of the speed command calculation circuit 7 and the normal time speed command from the speed command setter 12 Switch between and select the speed command.

The comparator 24 compares the terminal voltage Vpn of the smoothing capacitor 2 from the voltage detection circuit 5 with the output of the coefficient multiplier 25, and when the terminal voltage Vpn is lower than the output of the coefficient multiplier 25, the comparator 24 outputs a UV (undervoltage) signal "1".

FIG. 3 is a block diagram of a speed command calculation circuit 7 for calculating a power-off time speed command. In FIG. 3, the speed command calculation circuit 7 has coefficient multipliers 31 and 32 for setting the target voltage Vpnc on the terminal of the smoothing capacitor 2 and the capacitance C of the smoothing capacitor 2, and for calculating the value stored in the smoothing capacitor 2. Energy target value calculation circuit 34 of target value of energy, energy calculation circuit 35 for calculating energy stored in smoothing capacitor 2, power calculation circuit 36, subtractor 37, adder-subtractor 40, delay circuit 49, division device 52, torque limiting circuit 53, difference frequency calculation circuit 58, adder 59, subtractor 60, coefficient multipliers 61, 62 and 63, and adder 64; energy target value calculation circuit 34 uses coefficient multipliers 31 and 32 The output is calculated by (C×Vpnc ² )/2, and the energy calculation circuit 35 calculates (C×Vpn ² )/2 using the output of the coefficient multiplier 31 and the terminal voltage Vpc of the smoothing capacitor 2 sent from the voltage detection circuit 5, and the power The calculation circuit 36 calculates the power output P based on the inverter output current detection value obtained at the current detection circuit 4 and the voltage command value sent from the voltage command calculation circuit 8 .

A proportional gain for making the target value of stored energy sent from the energy target value calculation circuit 34 and the energy calculation circuit 35 coincide with each other and the current value is set in the coefficient multiplier 61, and the output of the coefficient multiplier 61 becomes a power output Target value Pref. The total value of the power loss in the machine including the inverter controller 20 and the AC motor 13 is set in the coefficient multiplier 62, and the value corresponding to the torque used to convert the torque into an acceleration value is set in the coefficient multiplier 63. The torque is obtained by using the inverse of the moment of inertia J of the entire load including the AC motor 13 as a guideline.

Next, the operation for calculating the power-off time speed command in the speed command calculation circuit 7 will be described.

The difference between the above-mentioned target value (C×Vpnc ² )/2 of stored energy and the current value is obtained using the subtractor 37, and the difference is multiplied by a gain to obtain the power output target value Pref. This power output target value Pref is corrected using the power loss value in the machine including the inverter controller 20 and the AC motor 13 using the adder-subtractor 40, and the correction value and the power are obtained by calculation of the power calculation circuit 36. Output the difference between P. The difference is divided by the speed information ωr^ of the AC motor 13 using the divider 52 to obtain the torque target value Tref. This torque target value Tref is limited using the torque limiting circuit 53, converted into an acceleration command using the gain set in the coefficient multiplier 63 and added to the current speed command ωr^ using the adder 54 to obtain the power-off time speed command.

Although in the above description, the power loss value of the machine including the inverter controller 20 and the AC motor 13 is set as a set value in the coefficient multiplier 62, the power loss value may be strictly expressed as the inverter function of the output current etc. and are combined.

Furthermore, in the case where the motor used is an induction motor, it is also possible to calculate the difference frequency with the difference frequency calculation circuit 58 using the output value of the torque limiter circuit 53, and use the adder 59 and the subtractor 60 to calculate the difference frequency for the speed command. compensation, and the input/output speed command of the speed command calculation circuit 7 is used as the basic frequency command of the induction motor so that the delay time until the planned regenerative power is obtained is shortened.

Also, although the speed information ωr of the AC motor 13 is obtained using the speed command output last time, in the case of incorporating a circuit for detecting or estimating the speed, a detected or estimated value of the speed may also be used.

Although the configuration is realized taking into account the power loss in the inverter controller 20, the power loss in the machine comprising the AC motor 13 and the compensation of the difference frequency in the case where the motor used is an induction motor, But any one or any combination of more of these considerations may be added. Even in this case, the respective effects remain unchanged.

As described above, a loop for controlling the power output of the inverter controller 20 to control the terminal voltage of the smoothing capacitor 2 is formed inside the loop for determining the deceleration command based on the target voltage Vpnc and the detected voltage Vpn of the smoothing capacitor 2; and , the power output target value is calculated in consideration of the power loss value of the machine including the inverter controller 20 and the AC motor 13 , and the torque target value is limited using the torque limit circuit 53 .

With the above operation, the terminal voltage of the smoothing capacitor 2 can quickly converge to the target value; even in a state where the target voltage of the smoothing capacitor 2 and the detected voltage coincide with each other, smooth deceleration operation can be performed, and unnecessary deceleration stops and deceleration does not occur. is repeated. Furthermore, since excessive torque can be prevented from being generated, the equipment used can be protected.

Next, using FIGS. 1 , 2 and 3 and FIG. 4 (timing chart when power failure occurs), continued operation during power failure detection in the inverter controller 20 according to this embodiment will be described.

Fig. 4(a) shows the on/off state of the AC power supply, Fig. 4(b) shows the on/off state of the power failure detection contact, and Fig. 4(c) shows the state of the operation command, Fig. 4 (d) shows changes in the terminal voltage Vpn of the smoothing capacitor 2 , and FIG. 4( f ) shows the speed command of the inverter controller 20 .

If a momentary power failure occurs in the AC power supply, the terminal voltage Vpn of the smoothing capacitor 2 detected using the voltage detection circuit 5 falls to undervoltage detection level 1 (UV level 1) or lower, or the electromagnetic contactor 11 opens. Power failure is detected at the moment of voltage drop or open operation (whichever is earlier). When a power outage is detected, the speed command selection circuit 6 switches the speed command from the normal time speed command to the power off time speed command using the switch circuit 21 .

Since the terminal voltage Vpn of the smoothing capacitor 2 becomes lower than the preset value of the coefficient multiplier 31, that is, the target voltage Vpnc due to power-off, a power-off time speed command calculated using the speed command calculation circuit 7 is issued to perform deceleration, And the AC motor 13 starts to decelerate; the regenerative energy depending on the deceleration rate and the moment of inertia J of the load charges the smoothing capacitor 2 via the inverter circuit 3 and raises the terminal voltage Vpn. At this time, strictly speaking, there is a reduction corresponding to the power loss in the inverter controller 20 and the power loss in the machine including the AC motor 13 .

On the other hand, the speed command selection circuit 6 sends a power-off signal to the speed command calculation circuit 7 when the power-off detection signal, that is, the output signal of the OR circuit 23, becomes "1". The speed command calculation circuit 7 calculates the power-off time speed command by performing the above calculation operation, sends the speed command to the voltage command calculation circuit 8 to decelerate the AC motor 13 .

Furthermore, in the case where the deceleration rate is moderate and the terminal voltage Vpn of the smoothing capacitor 2 becomes lower than the target voltage Vpnc, or conversely, in the case where the terminal voltage Vpn becomes higher, the power output target value Pref and the power output P A deviation is generated between them; the speed command is quickly controlled based on the deviation, and the control is performed so that the terminal voltage Vpn becomes equal to the target voltage Vpnc.

If the momentary power failure of the AC power supply is recovered before the AC motor 13 decelerates and stops, the terminal voltage Vpn of the smoothing capacitor 2 rises to the undervoltage detection level 1 (UV level 1) or higher, and the electromagnetic contactor 11 is turned off , the power-off detection signal shown in Fig. 2 becomes "0" and the speed command is switched to the speed command for normal operation; Acceleration or deceleration is performed during the acceleration/deceleration time.

With the above configuration, when a momentary power failure occurs in the AC power supply, the power failure time speed command is selected, the deceleration operation is performed, and the regenerative energy generated by this operation charges the smoothing capacitor 2 and raises the terminal voltage Vpn; therefore, the AC motor 13 is decelerated and can be continuously operated until it stops while preventing the voltage from becoming low; when the momentary power failure of the AC power supply is restored, the speed command is switched to the speed command for normal operation, thereby issuing The speed command for acceleration or deceleration is executed while operating the required acceleration/deceleration time until the speed command set value is reached; as a result, operation can be continued stably even if a momentary power failure occurs.

A second embodiment according to the present invention will be described below with reference to the drawings.

Example 2

Fig. 5 is a schematic configuration diagram showing the whole of an inverter controller 20' according to Embodiment 2 of the present invention. In Figure 5, numeral 1 represents the rectifier circuit, numeral 2 represents the smoothing capacitor, numeral 3 represents the inverter circuit, numeral 4 represents the current detection circuit, numeral 5 represents the voltage detection circuit, numeral 8 represents the voltage command calculation circuit, and numeral 9 represents the PWM control circuit, and numeral 10 represents a base drive circuit; these circuits perform operations similar to those of the circuit of the inverter controller 20 shown in FIG. 1 ; numeral 81 represents a power calculation for calculating the power output of the inverter circuit, numeral 71 represents a frequency command calculation circuit for calculating frequency command 2 (fref2) based on the outputs of voltage detection circuit 5 and power calculation circuit 81, and numeral 70 represents a circuit for checking that the output of voltage detection circuit 5 has exceeded the reference value. A sequential circuit is detected and used to set the output (fref2) of the frequency command calculation circuit 71 as the frequency command (fref).

Further, numeral 72 denotes a frequency command setter for outputting a frequency command 1 (fref1) serving as a frequency command during normal operation, and numeral 13 denotes an AC motor (hereinafter described as an induction motor) serving as a load. The frequency command setter 72 incorporates a soft start function for converting the frequency command into a command with an acceleration/deceleration rate.

The present invention is different from the prior art in that the present invention is provided with a sequence circuit 70 and a frequency command calculation circuit 71; the frequency command calculation circuit 71 is inside a loop for determining a deceleration command based on the target voltage Vpnc and the detection voltage Vpn of the smoothing capacitor 2 There is a loop for controlling the power output of the inverter controller 20', and a torque limiting circuit 87 for limiting the torque target value is also provided.

FIG. 6 is a block diagram of the sequential circuit 70 . In FIG. 6, numeral 73 represents a switch circuit, numeral 74 represents a comparator, and numeral 75 represents a coefficient multiplier.

Based on the terminal voltage of the smoothing capacitor, the coefficient multiplier 75 sets a threshold value for determining whether a normal operation or an overvoltage prevention operation is performed. This set value is a value larger than the terminal voltage value of the smoothing capacitor that can be obtained during normal operation.

FIG. 7 is a block diagram of a frequency command calculation circuit 71 . In Fig. 7, numerals 76 and 77 represent coefficient multipliers, numeral 78 represents an energy target value calculation circuit, numeral 79 represents an energy calculation circuit, numeral 80 represents a subtractor, numeral 81 represents a power calculation circuit, and numeral 82 represents a coefficient multiplier, The number 83 represents the limiting circuit, the number 84 represents the adder-subtractor, the number 85 represents the coefficient multiplier, the number 86 represents the divider, the number 87 represents the torque limiting circuit, the number 88 represents the coefficient multiplier, and the numbers 89 and 90 represent the adder , numeral 91 represents a subtractor, numeral 92 represents a difference frequency calculation unit, and numeral 93 represents a delay circuit.

In this figure, the target value Vpnc of the terminal voltage of the smoothing capacitor 2 is set in the coefficient multiplier 76, the capacitance C of the smoothing capacitor 2 is set in the coefficient multiplier 77, and the target value Vpnc for the smoothing capacitor 2 is set in the coefficient multiplier 82. The output value of the subtractor 80 is controlled to a control gain of zero, the sum of the loss value in the inverter controller 20' and the loss value in the machine including the AC motor 13 is set in the coefficient multiplier 85, and 1/J (J is the moment of inertia of the entire load including the AC motor 13 ) is set in the coefficient multiplier 88 .

In addition, a value equal to or greater than the reference value of the terminal voltage of the smoothing capacitor (the setting value of the coefficient multiplier 75 ) is set as Vpnc (the setting value of the coefficient multiplier 76 ).

The operation of the inverter controller 20' according to the present invention will be described using Figs. 5 to 7 .

When the output frequency f is lowered using a deceleration command or when a regenerative load is applied, the terminal voltage of the smoothing capacitor 2 is raised by regenerative energy obtained from the AC motor 13 .

The sequence circuit 70 compares the voltage detection value Vpn of the smoothing capacitor detected by the voltage detection circuit 5 with the set value of the coefficient multiplier 75; when Vpn>(the set value of the coefficient multiplier 75), the switch circuit 73 is switched from A The side is switched to the B side, thereby switching the frequency command from frequency command 1 (fref1, the output of frequency command setter 72) to frequency command 2 (fref2, the output of frequency command calculation circuit 71), and frequency command 2 (fref2) Output as a frequency command (fref).

The voltage command calculation circuit 8 calculates an output voltage command based on the frequency command (fref) sent from the sequential circuit 70, the PWM control circuit 9 outputs a signal to the base drive circuit 10 based on the output signal sent from the voltage command calculation circuit 8, and the base drives The circuit 10 drives the inverter circuit 3 based on the output signal from the PWM control circuit 9 .

Next, a method for calculating the frequency command 2 (fref2) selected when Vpn>(the setting value of the coefficient multiplier 75) will be described.

The energy target value calculation circuit 78 calculates the energy target value (C×Vpnc ² )/2 stored in the smoothing capacitor 2 using the set values of the coefficient multipliers 76 and 77, and the energy calculation circuit 79 uses the output value of the coefficient multiplier 77 The energy value actually stored in the smoothing capacitor 2 (C×Vpn ² )/2 is calculated from the terminal voltage detection value Vpn of the smoothing capacitor 2 sent from the voltage detection circuit 5 .

The subtractor 80 subtracts the output value of the energy target value calculation circuit 78 from the output value of the energy calculation circuit 79 and outputs the energy deviation, the limit circuit 83 limits the output value of the subtractor 80 to the lower limit value zero, and the output value of the limit circuit 83 The value is multiplied by the set value of the coefficient multiplier 82 to obtain the power output target value Pref. The reason why the limitation circuit 83 limits the energy deviation described above to the lower limit value zero is to prevent operation in the deceleration direction from being performed, for example, due to fluctuations in the terminal voltage of the smoothing capacitor.

The power calculation circuit 81 calculates the power output value P of the inverter controller using the inverter output current detection value, and obtains the inverter controller using the current detection circuit 4 and the output voltage command value sent from the output voltage command calculation circuit 8. Output current detection value. The adder-subtractor 84 subtracts the above-mentioned power output value P from the above-mentioned power output target value Pref and also subtracts the set value of the coefficient multiplier 85 and then outputs the power deviation ΔP.

The divider 86 calculates a torque target value by dividing the above-mentioned power deviation ΔP by the speed f of the AC motor 13 described later. The torque limiting circuit 87 limits the torque target value with a value determined in consideration of machine protection. The output value of the torque limiting circuit 87 is multiplied by the set value of the coefficient multiplier 88, and an acceleration target value is obtained.

Furthermore, the beat frequency calculation circuit 92 calculates the beat frequency using the output value of the torque limiting circuit 87 . The subtractor 91 subtracts the difference frequency from the frequency command (fref) output from the delay circuit 93 at the last time and outputs the speed f of the AC motor 13 . The adder 89 adds the speed f of the AC motor 13 to the acceleration target value output from the coefficient multiplier 88 and also adds the beat frequency output from the beat frequency calculation circuit 92, thereby obtaining a frequency command (fref2).

As described above, the power output target value Pref is calculated using the target voltage Vpnc of the terminal voltage of the smoothing capacitor 2 and its detection value Vpn, and the power is corrected in consideration of the power loss value of the machine including the inverter controller 20' and the AC motor 13. The target value Pref is output, thereby calculating the frequency command 2 ( fref2 ) at which the deviation ΔP between the power output target value Pref and the power output P becomes 0.

When Vpn<(the setting value of the coefficient multiplier 75), the switch circuit 73 is switched from the B side to the A side; Switches to frequency command 1 ( fref1 ) output by frequency command setter 72 , and normal operation resumes.

Since a small loop for controlling power output is configured, the torque target value is limited to a predetermined value, and beat frequency compensation is performed as described above, the terminal voltage of the smoothing capacitor is quickly and reliably converged to the target value, and it is possible to avoid Performing smooth operation repeating unnecessary acceleration/deceleration and deceleration to stop can protect the machine used by preventing excessive torque from being generated, and can shorten the delay time until the planned power output is obtained.

Depending on the sign of the energy deviation between the power output value P and the value output from the coefficient multiplier 82, the AC motor 13 can perform not only a regenerative operation but also an electric (power) operation. In the case of calculating the power output value P for electric (power) operation, the present invention can be more effectively implemented by performing an operation such that the adder-subtractor 84 adds the output of the coefficient multiplier 85 .

In addition, although the loss value of the machine including the inverter controller 20' and the AC motor 13 is set to a constant value used as the setting value of the coefficient multiplier 85, it is obvious that the loss value is strictly expressed as an inverter function of the output current etc. and is incorporated.

Furthermore, although the speed f of the AC motor 13 is obtained using the frequency command (fref) output at the last time, in the case of incorporating a circuit for detecting or estimating the speed, a detected or estimated value of the speed may also be used.

Also, although the AC motor is described as an induction motor in the above description, the present invention can be similarly implemented even if an AC motor such as a synchronous motor is used instead of the induction motor. In this case, the output of the beat frequency calculation circuit 92 should simply be set to zero.

Furthermore, although the configuration has been described taking into account losses in the inverter controller and in machines including AC motors, machine protection and, in the case of using an induction motor, compensation for difference frequency , but any one or any combination of these considerations may be used. Even in this case, the respective effects remain unchanged.

Furthermore, Embodiment 1 has been described using a speed command calculation circuit that calculates a speed command from a state during an instantaneous power failure or an output value of a voltage detection circuit based on a power output target value and a power output value, and has been used for calculating Frequency Command Calculation Circuit for Frequency Command Embodiment 2 has been described in place of using a speed command calculation circuit; however, even if a calculation circuit for calculating a frequency command is used in Embodiment 1 and a speed command for calculating computing circuit, the present invention can also be similarly implemented.

Industrial applicability

The present invention is applicable to all inverter controllers for driving motors in which a momentary power failure may occur and regenerative operation may be performed and also to a method of operating the inverter controller.

Claims (8)

1. An inverter controller, comprising: AC motor as load, a rectification circuit for converting AC power from an AC power source into DC power, a smoothing capacitor for smoothing the DC voltage from the rectification circuit, an inverter circuit for converting the DC power supplied via the smoothing capacitor into a desired frequency, a current detection circuit for detecting an output current from the inverter circuit, a voltage detection circuit for detecting the terminal voltage Vpn of the smoothing capacitor, a speed command calculation circuit that calculates a power-off time speed command used in a case where the AC power supply is judged to be power-off, an output voltage command calculation circuit that calculates a voltage command to the AC motor based on a power failure detection signal, a normal time speed command, and a power failure time speed command; Wherein, the speed command calculation circuit includes: a power calculation circuit, using the output current and the voltage command to calculate a power output value; a power target calculation circuit that calculates a power output based on (C×Vpnc ² )/2 using the terminal voltage Vpn, a preset target value Vpnc of the terminal voltage at power-off time, and the capacitor capacitance C of the smoothing capacitor target value, The power-off time speed command is calculated based on the power output target value and the power output value. 2. The inverter controller according to claim 1, wherein The speed command calculation circuit performs calculation to correct the power output target value by adding or subtracting a power loss value of the inverter controller based on the sign of the power output value. 3. The inverter controller according to claim 1, wherein The speed command calculation circuit performs calculation to correct the power output target value by adding or subtracting the power loss value of a machine including an AC motor based on the sign of the power output target value. 4. The inverter controller according to claim 1, wherein The speed command calculation circuit performs calculation to correct the torque target value by calculating a torque target value using a deviation between the power output target value and the power output value and a speed command output at the last time. 5. The inverter controller according to claim 1, wherein The speed command calculation circuit limits a torque target value obtained based on the power output target value and speed information of the AC motor. 6. The inverter controller according to claim 1, wherein In the case where the AC motor is an induction motor, the speed command calculation circuit corrects the slip speed command by calculating a slip speed command using a torque target value obtained based on the power output target value and speed information of the AC motor. Slip speed command. 7. An inverter controller, comprising: AC motor as load, a rectification circuit for converting AC power from an AC power source into DC power, a smoothing capacitor for smoothing the DC voltage from the rectification circuit, an inverter circuit for converting the DC power supplied via the smoothing capacitor into a desired frequency, a current detection circuit for detecting an output current from the inverter circuit, a voltage detection circuit for detecting the terminal voltage Vpn of the smoothing capacitor, a frequency command calculation circuit for calculating a frequency command used when the terminal voltage Vpn is equal to or greater than a set value, an output voltage command calculation circuit for use based on whether or not the terminal voltage Vpn is above a set value, a normal time frequency command, and when the terminal voltage Vpn is above a set value of the frequency command to calculate a voltage command to the AC motor, Wherein, the frequency command calculation circuit includes: a power calculation circuit, using the output current and the voltage command to calculate a power output value; The power target calculation circuit uses the terminal voltage Vpn, a preset target value Vpnc of the terminal voltage at the time of overvoltage prevention operation, and the capacitor capacitance C of the smoothing capacitor, according to (C×Vpnc ² )/2 Calculate the power output target value, The frequency command is calculated based on the power output target value and the power output value. 8. An operation method for addressing fluctuations or momentary power outages of AC power for an inverter controller, the inverter controller comprising: AC motor as load; A rectification circuit for converting AC power from an AC power source into DC power; a smoothing capacitor for smoothing the DC voltage from the rectification circuit; an inverter circuit for converting DC power supplied via the smoothing capacitor into a desired frequency; a current detection circuit for detecting the output current of the inverter; and a voltage detection circuit for detecting a terminal voltage Vpn of the smoothing capacitor; a speed command calculation circuit that calculates a power-off time speed command used in a case where the AC power supply is judged to be power-off, an output voltage command calculation circuit that calculates a voltage command to the AC motor based on a power failure detection signal, a normal time speed command, and a power failure time speed command; The operation method comprises the following steps: calculating a power output value by using the output current and the voltage command; Using the terminal voltage Vpn, the preset target value Vpnc of the terminal voltage at power-off time, and the capacitor capacitance C of the smoothing capacitor, the power output target value is calculated according to (C×Vpnc ² )/2; The power-off time speed command is calculated based on the power output target value and the power output value.

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