JPH11308894A - Process for power failure of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend in the maximum extent the time required until the control is disabled, by reducing the rotating speed of motor until a DC voltage becomes lower than the lower limit voltage in the preset reduction rate when the detected DC voltage becomes lower than the power failure detection level voltage, and until voltage control returns to the ordinary control when the DC voltage exceeds the lower limit value voltage. SOLUTION: An AC voltage supplied from an AC power supply 1 is rectified to a DC voltage, a PN voltage thereof is smoothed via a DC capacitor 3 and is then applied to an inverter 6. This voltage is then detected by a PN voltage detecting means 4 and is then applied to a controller 5. Here, the lower limit allowable voltage of a DC voltage and the power failure detecting level voltage are set. When a detected value of DC voltage from the PN voltage detecting means 4 becomes lower than the power failure detecting level voltage during the motor operation, the motor is reduced in rotating speed until it exceeds the lower limit allowable voltage in the preset reduction rate. When the DC voltage exceeds toe lower limit allowable voltage, voltage control is returned to the ordinary control. As a result, the time required until the control is disabled during the power failure can be extended during the operation of motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the operation of an electric motor at the time of an instantaneous blackout (instantaneous blackout).

[0002]

2. Description of the Related Art Conventionally, a converter for converting a supply voltage from an AC power supply to a DC voltage, a DC capacitor for smoothing the converted DC voltage, and a DC voltage for detecting the magnitude of the smoothed DC voltage Detecting means, an inverter unit for switching the smoothed DC voltage and converting it to an AC voltage of a required frequency, a conversion circuit for regenerating the electric power of the electric motor to the AC power supply, and generating a switching pattern of the inverter. In a motor control device provided with a control circuit for controlling the driving of the motor, the smoothed DC voltage V
_PN is monitored, and when the DC voltage _VPN becomes lower than the limit value / low voltage level _VU1 , the semiconductor base block or gate block of the inverter section is performed. Or decelerated at a set deceleration rate is when it becomes lower than the low voltage warning level V _U0 higher than the previous low voltage level V _U1, so as to regenerate the electric power of the electric motor to the power supply, the DC voltage V _PN is low voltage warning When the level exceeds the level V _U0 , it is determined that recovery has been made, and normal control is performed [this is referred to as “conventional example 1”].

[0003] Also, Japanese Patent Application Laid-Open No. 8-19286 (hereinafter referred to as "Conventional Example 2") discloses a motor control device that decelerates a motor when an external power supply fails and prevents a dangerous free-run state of the motor. is there. That is, the external power supply is also connected to the control power supply circuit, generates a drive level voltage of the circuit, and supplies it to the power storage circuit. The power storage circuit supplies the drive voltage to the power supply monitoring circuit, the brake control circuit, and the logic generation unit. The power supply monitoring circuit monitors the voltage of the external power supply, and outputs a stop detection signal to the brake control circuit when the external voltage goes into a power failure state.The brake control circuit outputs a logic signal while the drive voltage is being supplied from the power storage circuit. A stop control signal is output to the generation unit, and while this signal is being input, the logic generation unit outputs a drive control signal for decelerating the motor to the inverter unit. This is a device that outputs a drive signal that stops and decelerates at a speed pattern of.

Further, as a third conventional example, there is JP-A-6-165579. This is a method for extending the continuation time of the motor during a momentary power failure without increasing the capacity of the DC intermediate capacitor at the moment of a power failure of an AC motor driven by a voltage source inverter. If the voltage drops to the set voltage, the operation command is decelerated, regenerative power is obtained, the inversion of the intermediate voltage is increased, and the intermediate voltage rises and recovers to the first stage set voltage (first stage set voltage> second stage set voltage). This is a means for increasing the speed and repeating this.

[0005]

However, the prior art 1
If the power is restored when the motor is rotating at high speed and the power is restored to the base block state, and control is started, the motor is in the power generation state. May be destroyed. Therefore, it is necessary to make the best use of the control during the power failure, and to compensate for the fact that the speed is sufficiently reduced even if the control is interrupted by the power failure. When performing deceleration processing, depending on the setting of the deceleration rate, power regeneration cannot catch up with the decrease in power supply voltage and control cannot be continued to the level of power failure, or regenerative energy increases during deceleration and rises to the power return level Then, the control is shifted to the normal control, the acceleration is started, the voltage drops sharply, the voltage drops to the power failure level, or the deceleration process is executed again, and the acceleration and deceleration are repeatedly performed.

Further, the conventional example 2 is merely a means for preventing free running of the motor at the time of a power failure, and the conventional example 3 is based on the same concept as the conventional example 1 and has a drawback of repeated acceleration / deceleration. Here, the present invention overcomes the disadvantages of each of the conventional examples, provides hysteresis for the power failure detection level and the recovery level, and furthermore, when a power failure is detected, changes in the DC voltage [the voltage across the smoothing capacitor and the voltage between PN]. The deceleration rate was changed to change the voltage around the power failure detection level.
An object of the present invention is to provide a method of processing at the time of a power outage of a motor, which can maintain the voltage between N and extend the time until the control becomes impossible.

[0007]

In order to solve the above-mentioned problems, a first aspect of the present invention is to provide a converter for converting a supply voltage from an AC power supply to a DC voltage, and for smoothing the converted DC voltage. A DC capacitor to be converted, a DC voltage detecting means for detecting the level of the smoothed DC voltage, an inverter unit for switching the smoothed DC voltage and converting it to an AC voltage of a required frequency, A conversion circuit for regenerating the AC power supply, and a control circuit for generating a switching pattern of the inverter and controlling the driving of the motor, the method for processing at the time of power failure of the motor, wherein the DC voltage of the normal operation is possible. Voltage lower limit V
_U1, and a lower limit allowable voltage V _U0 of the DC voltage when a lower limit voltage allowable as a power supply is input, and a power failure detection level voltage V _U2 lower than the lower limit allowable voltage V _{U0 and} higher than the voltage value lower limit V _U1. the set each, the said lower limit deceleration rate alpha _d which is set the electric motor when the detected value V _PN is lower than the power failure detecting level voltage V _U2 of the DC voltage from said DC voltage detecting means during the motor operation allowable voltage decelerated to over V _U0, a power failure processing method of an electric motor, characterized in that return to the normal control when exceeding the lower allowable voltage V _U0.

[0008] The invention of claim 2 of the present invention, when the detection value V _PN of the DC voltage is lower than the power failure detecting level voltage V _U2, and decelerating the motor in the deceleration rate alpha _d, the DC The voltage detection value _VPN is equal to the lower limit allowable voltage _VU0.
And acceleration / deceleration is stopped between the power failure detection level voltage _VU2 and the speed of the motor is kept constant. When the detection value _{VPN of the} DC voltage exceeds the power failure detection level voltage _VU0 , normal control is performed. 2. The method according to claim 1, wherein the electric motor recovers from a power failure.

According to a third aspect of the present invention, when the detected value V _{PN of the} DC voltage becomes lower than the power failure detection level voltage V _U2 , the initial value α ₀ of the set deceleration rate and the DC voltage Using the detected value V _PN , the power failure detection level voltage V _U2, and an appropriate gain K, the deceleration rate α _d becomes α _d = α ₀ −
The motor is controlled by decelerating at a rate represented by K · (V _U2 −V _PN ), and normal operation is performed when the detection value V _{PN of the} DC voltage exceeds the power failure detection level voltage V _U0. A method according to claim 1 or 2, wherein the electric motor is processed during a power failure.

The invention of claim 4 of the present invention measures the time t _UV from the time when the detection value V _{PN of the} DC voltage becomes lower than the power failure detection level voltage V _U2 , and detects the detection value V of the DC voltage. _{Even when PN} exceeds the power failure detection level voltage V _U0 ,
3. The method according to claim 2, wherein the acceleration / deceleration is stopped within a set time t to keep the speed of the motor constant.

According to a fifth aspect of the present invention, when the detected value V _{PN of the} DC voltage becomes lower than the power failure detection level voltage V _U2 , the torque is determined by using S (ω) as a symbol indicating the rotation direction. The command _Tr is _Tr = −S (ω) · K · (V _U2 −V
_PN ) where S (ω) is a (+) sign when the motor rotates forward with respect to the load, and a (-) sign when the motor rotates reversely. The method according to claim 1, wherein the normal operation is performed when the detected value _{VPN of the} DC voltage exceeds the power failure detection level voltage _VU0 .

According to a sixth aspect of the present invention, when the detected value V _PN of the DC voltage is between the power failure detection level voltage V _U2 and the lower limit allowable voltage V _U0 of the DC voltage, a torque command to the motor is provided. 6. The method according to claim 5, wherein the power failure is set to zero.

According to the present invention having the above means, the first means is to provide a difference (hysteresis) between the low voltage warning level and the voltage level at which the power supply returns and shifts to the normal operation. Furthermore, since the energy regenerated by the motor fluctuates depending on the magnitude of the load applied to the motor, the deceleration time is changed in accordance with the voltage fluctuation. Alternatively, in order to prevent the voltage from accelerating suddenly when shifting to normal control, acceleration is prohibited for a certain period after the power failure and repeated at a constant speed and deceleration so that the power supply voltage does not drop to the power failure voltage At a certain level. Alternatively, a torque command in the deceleration direction is given instead of deceleration. By these methods, at the time of a power failure, it is possible to effectively use the regenerative energy from the electric motor to maintain a long time until the voltage level becomes uncontrollable, and even if the power failure occurs, the speed is sufficiently reduced. Since the situation can be compensated, the operation can be safely restarted even after recovery from the power failure.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a general-purpose control circuit that drives an electric motor to which the present invention is applied by inverter driving. The AC voltage supplied from the AC power supply 1 is rectified into a DC voltage in the converter 1,
The DC voltage [PN voltage V _PN ] is smoothed via the DC capacitor 3 and applied to the inverter 6. Then, the DC voltage is detected by the PN voltage detecting means,
The control device 5 controls the chopper ring cycle of the inverter 6, and the control device 5 contributes the previously detected DC voltage value between the PNs to a motor operation command (not shown),
The timing of the base voltage to each semiconductor constituting the inverter 6 is adjusted.

[Embodiment 1] The present invention relates to a DC voltage lower limit _VU1 capable of normal operation and a lower limit allowable voltage V DC of the DC voltage when a lower allowable voltage is input as a power supply. and _U0, is set and the lower allowable voltage V _U0 limit voltage V higher than _U1 power failure detecting level voltage V _U2 below. During the operation of the motor, the PN voltage detection means 4
Is the DC voltage detection voltage _VPN from the power failure detection level voltage V
_When the speed drops below _U2 , the motor deceleration rate α
decelerated until it exceeds the lower limit allowable voltage lower allowable voltage V _U0 at _d, a time processing method outage of the electric motor to return to the normal control when it exceeds the lower limit allowable voltage V _U0.

FIG. 2 shows a first invention of the present invention [Claim 1].
6 is a flowchart showing the operation procedure of FIG. The DC voltage _VPN is detected by the DC voltage detecting means 4 [Step 201
]. This DC voltage _VPN is compared with the power failure detection level voltage _VU2 [step 202]. When the DC voltage _VPN is lower than the power failure detection level voltage _VU2 [yes in step 202], a flag is turned on [step 202]. Step 203]. When this flag is ON, the DC voltage V _PN is compared with the DC voltage V _UO between the PN when the minimum voltage allowed by the voltage source is input [step 204], and the DC voltage detection value V _PN between the _PNs is determined. When the PN DC voltage V _UO is _exceeded [yes in step 204],
Complete to return to the normal control set off a flag [step 206], when the DC voltage between PN when the minimum voltage DC voltage V _PN is the voltage source allowed is input does not exceed V _UO [No in step 204] sets the deceleration rate alpha _d gives a deceleration command [step 207].

In addition, when the answer is No in Step 202, the program jumps to Step 204, where the flag is off.
Step 204 is also No, and this operation ends. Incidentally, the deceleration rate α _d is set in advance to a value determined according to the inertia of the electric motor, the magnitude of the load applied to the electric motor, and the like. FIG. 3 shows the fluctuation of the voltage and the speed of the electric motor at the moment of an instantaneous stop according to this method. FIG. 3 (a) is a time transition diagram of the DC voltage and the voltage between PN at the time of an instantaneous power failure, and FIG. 3 (b) is a speed change diagram of the motor corresponding to FIG. 3 (a). Time t
₃₁ power outage occurs and is detected by the reduced time t ₃₂ to the power failure detecting level voltage V _U2 below, the motor speed is decelerated from time t ₃₃ to time t _35, continues to increase the DC voltage V _PN therebetween regenerative power AC power is restored after normal to release the power failure at time t _34, completely voltage is restored at time t ₃₆ and the voltage rises from the time t _34, the motor is a power failure at time t ₃₇ started to accelerate at time t ₃₅ Return to the previous speed.

Conventional method [Conventional example 1] for comparison with the present invention
FIG. 4 shows the voltage fluctuation and the speed of the electric motor at the moment of an instantaneous power failure. FIG. 4 (a) is a time transition diagram of the DC voltage and the voltage between PN at the time of an instantaneous power failure, and FIG. 4 (b) is a speed change diagram of the motor corresponding to FIG. 4 (a). However, this conventional method is the same as the conditions shown in the characteristic diagram of FIG. 3 of the present invention, except that there is no setting of the power failure detection level voltage _VU2 . The state of the load in the conventional technique, the influence of response delay when regenerated electric energy by the deceleration is large, or become repeating the processing of the return power failure [time t _44, the time t _45],
In some cases, the voltage may drop to the power failure level and control may not be able to continue.

[Third Embodiment] Next, when the inertia of the driving body, that is, the electric motor and its mechanical load is large, there is a case where the motor is largely regenerated by a slight deceleration. In this case, the above method [Claim 1] alone does not improve the problem of repeated acceleration / deceleration because the voltage rises to the return level due to deceleration. To cope with this, acceleration and deceleration are prohibited between the PN DC voltage V _UO and the power failure detection level voltage V _U2 when the minimum voltage allowed by the voltage source is input, and the speed is made constant. 2]. FIG. 5 shows a flowchart according to this method.
FIG. 6 shows the voltage fluctuation and the change in the motor speed at this time. FIG. 6 (a) is a time transition diagram of the DC voltage and the PN voltage at the time of an instantaneous power failure, and FIG. 6 (b) is a speed change diagram of the motor corresponding to FIG. 6 (a).

The flow chart of FIG. 5 is similar to the flow chart of FIG.
In the case of No in step 505, it is determined in step 506 whether the PN DC voltage detection value V _PN is higher than the power failure detection level voltage V _U2 , and if yes, the setting is made in step 508. Command is received at the reduced deceleration rate, and if No, the deceleration rate is 0 in step 509.
And deceleration command acceleration / deceleration is prohibited [time t _{64 in} FIG.
Time point t ₆₇ ]. The motor speed has a smooth change curve that is good for the load.

Further, when the load fluctuates, for example,
The deceleration rate cannot be set to an optimal value. In order to cope with this, the deceleration rate initial value α ₀ is set, and when the PN direct-current voltage detection value V _PN becomes lower than the power failure detection level voltage value V _U2 , α _d = α ₀ −K · (V _U2 -V _PN) ........................ decelerated using a deceleration rate alpha _d which is calculated by the expression (1). K
Is a conversion gain of the deceleration rate, and is determined by the size of the load and the like. As a result, the fluctuation of the voltage and the speed of the motor during the instantaneous stop become as shown in FIG. 7 [Claim 3]. Thus, it will follow a smooth change curve from time t ₇₂ to time _76. In this operation procedure, FIG. 7 (a) is a time transition diagram of the DC voltage and PN voltage at the time of an instantaneous power failure, and FIG. 7 (b) is a speed change diagram of the motor corresponding to FIG. 7 (a). .

[Embodiment 4] When the load is large, it is necessary to increase the deceleration gain K. However, due to a delay in the response of the motor, a response delay until the start of deceleration due to a power failure causes a PN DC voltage detection value to be detected. _VPN decreases rapidly, and the deceleration rate is greatly corrected accordingly. When the deceleration starts, the PN DC voltage detection value _VPN becomes the PN DC voltage when the minimum voltage allowed by the voltage source is input. The motor may be accelerated beyond V _UO , and the PN DC voltage detection value V _PN may suddenly decrease, causing a problem of repeating deceleration again at a large rate. Therefore, the time t _UV from when the PN DC voltage detection value V _PN becomes lower than the power failure detection level voltage V _U2 is measured, and if this time t _UV has not elapsed until the set time t for compensating for the power failure, even beyond the PN between the DC voltage V _UO when the minimum voltage PN between the DC voltage detection value V _PN is the voltage source allowed is input, to keep the speed constant [claim 4].

FIG. 8 shows this flowchart. FIG as 8 performs successive operations, set the count value of time t _UV corresponding to the time setting value to ensure a power failure, by subtracting counting time t _UV upon detection [Step 802], the time t _UV
There [yes in step 802] if not 0, even beyond the PN between the DC voltage V _UO when the minimum voltage PN between the DC voltage detection value V _PN is the voltage source allowed is input, the speed constant [Step 802 → Step 804 (after subtracting 1 from the set time)] → Step 806 → Step 80
7 → Step 808]. If No in step 802, the process proceeds to step 803, and if the PN direct-current voltage detection value V _PN is lower than the power failure detection level voltage V _U2 [No in step 803] This is also No in step 806, and this operation ends immediately. ,
Higher PN between the DC voltage detection value V _PN is from power failure detecting level voltage V _U2 at step 802 when the [yes in step 803, the process proceeds to step 805, check the flag and remain time t _UV set value Go to step 806.

Further, the process proceeds from step 806 to step 807, in which the PN DC voltage detection value _VPN is
_If it is higher than _U2 [No in step 803], go to step 809, determine whether the time t _UV is greater than 0, and if yes, perform control in step 810 to set the deceleration rate to 0 and inhibit acceleration / deceleration. , If No, further PN in step 811
During the DC voltage detection value V _PN is determined power failure detecting level voltage V _UO greater than or video, If No becomes control in step 810, turns off the flag moves to step 812 if yes return to the normal control I'm going to.

[Embodiment 5] If the response delay is large, it is more effective to control the torque directly than to use the above means. Instead of correcting the deceleration rate of the above means, the control is switched to torque control, and the power failure detection level voltage value V _U2 , the PN direct-current voltage detection value V _PN , an appropriate gain K, and S (ω) indicating the rotation direction are used. (2
_{Equation), T r = -S (ω} ) · K · (V U2 -V PN) ........................ ( may be performed a control by using the torque command T _r which is obtained by Expression 2) [not shown ]. However, S (ω) has a (+) sign when the motor rotates forward with respect to the load, and a (-) sign when the motor rotates reversely. In this manner, the present invention prepares various control means depending on the state of the load, and can smoothly perform processing at the time of power failure of any load.

[0026]

As described above, according to the present invention, it is possible to maintain a long time until control becomes impossible at the time of a power failure during operation of the motor, and even if the power failure occurs, the speed is sufficiently reduced. Therefore, there is a special effect that the control can be safely restarted without breaking the circuit when the power is restored thereafter.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a general-purpose control circuit for driving an electric motor to an inverter to which the present invention is applied;

FIG. 2 is a flowchart showing a steering procedure according to the first invention [Claim 1] of the present invention;

3 (a) and 3 (b) show the voltage fluctuation and the speed of the motor at the momentary power failure according to the method of FIG. 2; FIG. 3 (a) is a time transition diagram of the DC voltage and PN voltage at the momentary power failure; Motor speed change diagram corresponding to a)

FIG. 4 shows the voltage fluctuation and the motor speed at the momentary power failure according to the conventional method [conventional example 1], (a) is a temporal transition diagram of the DC voltage and PN voltage at the momentary power failure, and (b) is Fig. 4 (a)
Of speed change of motor corresponding to

FIG. 5 is a flowchart according to the present invention in a case where a large regeneration is performed with a small deceleration such as when the inertia of the load is large.

6A and 6B show a change in voltage and a change in motor speed during the operation procedure in FIG. 5, wherein FIG. 6A is a time transition diagram of DC voltage and PN voltage during an instantaneous power failure, and FIG. Motor speed change diagram corresponding to (a)

FIG. 7 shows the voltage fluctuation and the speed of the motor at the time of an instantaneous power failure according to the present invention when the load fluctuates, and (a) is a temporal transition diagram of the DC voltage and the PN voltage at the time of an instantaneous power failure; ) Is the motor speed change diagram corresponding to Fig. 7 (a).

FIG. 8 is a flowchart showing an operation procedure in the case of FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter 3 DC capacitor 4 PN voltage detection means 5 Control device 6 Inverter 7 Reflux diode 8 Motor

Claims (6)

[Claims] 1. A converter for converting a supply voltage from an AC power supply to a DC voltage, a DC capacitor for smoothing the converted DC voltage, and a DC voltage detection for detecting the magnitude of the smoothed DC voltage Means, an inverter section for switching the smoothed DC voltage and converting it to an AC voltage of a required frequency, a conversion circuit for regenerating electric power of the motor to the AC power supply, and generating a switching pattern of the inverter. In the electric power failure processing method provided with a control circuit for controlling the driving of the electric motor, the voltage value lower limit _VU1 of the DC voltage capable of normal operation, and the DC when the lower limit voltage allowable as a power supply is input a lower allowable voltage V _U0 of the voltage, the lower allowable and said limit voltage V _U1 higher power failure detecting level voltage than V _U2 sets each lower than the voltage V _U0, the motor In the deceleration rate alpha _d the detection value V _PN of the DC voltage from said DC voltage detecting means during rolling has set the electric motor when it becomes lower than the power failure detecting level voltage V _U2 to over the lower allowable voltage V _U0 A method for processing at the time of a power failure of an electric motor, characterized in that the motor decelerates and returns to normal control when the voltage exceeds the lower limit allowable voltage _VU0 . 2. When the detection value V _{PN of the} DC voltage becomes lower than the power failure detection level voltage V _U2 , the motor is decelerated at the deceleration rate α _d , and the detection value V _{PN of the} DC voltage is _Acceleration / deceleration is stopped between the lower limit allowable voltage V _U0 and the power failure detection level voltage V _U2 , the speed of the motor is kept constant, and the detection value V _{PN of the} DC voltage is the power failure detection level voltage V <sub>U
2. The</sub> method according to claim 1, wherein the control returns to the normal control when the value exceeds _U0 . 3. When the detected value V _{PN of the} DC voltage becomes lower than the power failure detection level voltage V _U2 , the initial value α ₀ of the set deceleration rate, the detected value V _{PN of the} DC voltage and the power failure detection Using the level voltage V _U2 and an appropriate gain K, the deceleration rate α _d is reduced at a rate represented by α _d = α ₀ −K · (V _U2 −V _PN ) to control the motor, and The voltage detection value V _PN is equal to the power failure detection level voltage V
_{The method according} to claim 1 or 2, wherein a normal operation is performed when _U0 is _exceeded . Wherein said detection value V _PN DC voltage measures the time t _UV from when lower than the power failure detecting level voltage V _U2, the detection value V _PN is the power failure detecting level voltage V of the DC voltage 3. The method according to claim 2, wherein the acceleration / deceleration is stopped within a set time t to keep the speed of the motor constant even when the speed exceeds _U0 . 5. When the detection value V _{PN of the} DC voltage becomes lower than the power failure detection level voltage V _U2 , the torque command _Tr is set to _Tr = − using S (ω) as a symbol indicating the rotation direction. S (ω) · K · (V _U2 −V _PN ) where S (ω) has a (+) sign when the motor rotates forward with respect to the load, and a (-) sign when the motor rotates reversely.
The motor and torque control in represented by a torque command, the detected value V _PN is the power failure detecting level voltage V of the DC voltage
_The method according to claim 1, wherein the normal operation is performed when _U0 is _exceeded . 6. The detection value V _{PN of the} DC voltage includes a power failure detection level voltage V _U2 and a lower limit allowable voltage V _{U0 of the} DC voltage.
The method according to claim 5, wherein the torque command to the electric motor is set to zero during the period between the two.