CN1285168C - Controller for inverter device - Google Patents

Abstract

A control apparatus for inverters is provided to suppress a chattering in an output voltage of an inverter portion by raising an output voltage when a chattering is detected in a chattering state detector. A control apparatus(4) for inverters(1) having a DC(Direct Current) voltage as an input and operates an AC(Alternating Current) motor as a load. The control apparatus includes a driving signal calculator(43), a voltage detector, and a chattering state detector(42). The driving signal calculator calculates a driving signal for an inverter portion(41) which converts a DC source to a variable frequency-variable voltage AC voltage. The voltage detector detects the DC voltage. The chattering state detector detects a chattering state of the AC motor from a magnitude of a pulsation included in the detected DC voltage.

Description

Control device for inverter unit

technical field

The invention relates to a control device for an inverter (inverter) that drives an AC motor at a variable speed after converting a DC voltage into an AC voltage of variable frequency and voltage.

Background technique

When using an inverter device to drive an AC motor, the distortion of the applied voltage due to the dead time of the PWM (puleswidth modulation) signal driving the inverter, and the impedance (impedance) and moment of inertia of the AC motor, etc. Interaction, sometimes the current waveform periodically vibrates this so-called "disharmony phenomenon". this phenomenon. It occurs quite frequently especially in large AC motors, and in low load, low frequency bands.

After this kind of imbalance occurs, the AC motor itself will vibrate, and when the vibration is severe, it will make it unable to continue its operation. As a method of suppressing this out-of-tuning phenomenon, there is a method of correcting an error in the output voltage caused by the dead time of the PWM signal of the inverter, which is one of the main causes of the out-of-tuning occurrence. As an example thereof, the following method has been disclosed (refer to Non-Patent Document 1).

In this method, a current sensor (sensor) for detecting the current of the AC motor is provided, and the PWM signal of the inverter is corrected according to the current phase of the AC motor detected by the current sensor, thereby suppressing the distortion of the applied voltage. In this way, the occurrence of imbalance is suppressed, and the vibration of the AC motor is suppressed.

In addition, as another method for detecting and suppressing the occurrence of imbalance, the following method has also been disclosed (refer to Patent Document 1). In this method, as shown in FIG. 12 , a current sensor 103 for detecting the value of the current flowing into a compressor 102 driven by an inverter unit 101 of an inverter device is provided. The AC unit imbalance determination unit 104 determines an imbalance state based on the rate of change of the current detected by the current sensor 103 . When the AC unit imbalance judging unit 104 determines that it is in an imbalance state, the output voltage change command unit 105 operates to increase the voltage command value. Then, the waveform calculation unit 106 obtains a required PWM pulse width based on the output voltage value and the output frequency command value from the output voltage change command unit 105 , and drives the inverter unit 101 . With this configuration, the occurrence of out-of-adjustment and vibration of the compressor 102 is suppressed.

[Non-Patent Document 1] Nikkan Kogyo Shimbun "Inverter Drive Handbook" page 512 "Dead Time Correction Method"

[Patent Document 1] Japanese Unexamined Patent Publication No. 10-23789 ([0018], FIG. 1)

However, the method of the above-mentioned Non-Patent Document 1 can correct the voltage deformation caused by the dead time and suppress the imbalance, but there is a problem that a current sensor is required, which leads to an increase in the size and cost of the inverter device.

In addition, the method of Patent Document 1 also has the problem of requiring a current sensor (sensor), which increases the size of the device and increases the cost; in addition, when using a resistor as a current sensor, there is also the need for an operational amplifier ( Amplifier), increase the number of components, and increase the volume of the device; and, after adopting this structure, there is also the problem that it is difficult to accurately control due to the influence of power supply voltage fluctuations.

Contents of the invention

The present invention is to solve such problems in the prior art, and an object of the present invention is to provide a control device for an inverter device capable of detecting out-of-tuning with a simple structure and reliably controlling the out-of-tuning.

The inverter device receives a DC voltage and supplies AC power to an AC motor as a load. As a control device for such an inverter device, the present invention has, in addition to a drive signal calculation unit that calculates and outputs a drive signal for an inverter unit that converts an AC voltage of variable frequency and variable voltage, to: a voltage detection unit for detecting the DC voltage; and an imbalance state detection unit for detecting an imbalance state of the AC motor based on the magnitude of a ripple component included in the detected DC voltage. When an out-of-adjustment state is detected by the out-of-adjustment state detection means, the drive signal calculation means corrects the drive signal so as to increase the output voltage of the inverter unit.

After adopting the above structure, the occurrence of imbalance can be suppressed, the vibration of the AC motor can be reduced, and a control device for the AC motor with simple structure, low price and high reliability can be provided.

In the invention described in claim 1, in the control device, in addition to the drive signal calculation unit, further includes: a voltage detection unit that detects the DC voltage; The out-of-adjustment state detecting part of the out-of-adjustment state of the AC motor. When an out-of-tuning state is detected, the output voltage of the inverter unit is increased to suppress out-of-tuning, thereby providing an AC motor control device with a simple structure, low cost, and high reliability.

In the invention described in claim 4 of the present invention, the control device further includes, in addition to the drive signal calculation means: a voltage detection means for detecting the DC voltage; An output voltage storage unit that stores the desired output voltage value. When the value of the detected DC voltage changes, the output voltage value preset and stored in the output storage unit can be output, which can provide low price, simple structure and control, high stability for voltage changes, and resistance to voltage changes. The effect of the control device of the AC motor with strong interference and high reliability.

Description of drawings

FIG. 1 is a block configuration diagram of a control device according to a first embodiment of the present invention.

FIG. 2 is a graph showing the waveform of the current flowing into the motor 2 and the voltage waveform across the electrolytic capacitor 3d.

FIG. 3 is a graph showing the waveform of the current flowing into the motor 2 and the voltage waveform across the electrolytic capacitor 3d.

4 is a block configuration diagram of a control device according to a second embodiment of the present invention.

FIG. 5 is a graph showing the waveform of the current flowing into the motor 2 and the voltage waveform across the electrolytic capacitor 3h.

FIG. 6 is a graph showing a waveform of a current flowing into the motor 2 and a waveform of a voltage across the electrolytic capacitor 3h.

7 is a block configuration diagram of a control device according to a third embodiment of the present invention.

Fig. 8 is a block configuration diagram showing another mode in the third embodiment.

9 is a block configuration diagram of a control device according to a fourth embodiment of the present invention.

Fig. 10 is a block configuration diagram showing another mode in the fourth embodiment.

Fig. 11 is a flowchart showing the operation of the control device in Fig. 1 .

Fig. 12 is a block diagram showing a conventional AC motor control device.

In the figure: 1—inverter; 2—motor; 3—DC power supply; 3a—single-phase AC power supply; 3b—reactor; 3c—single-phase diode bridge; 3d—electrolytic capacitor; 3e—three-phase AC power supply ; 3f—three-phase diode bridge; 3g—reactor; 3h—electrolytic capacitor; 4—control device; 41—A/D converter; Storage unit; 45—DC average calculation unit.

Detailed ways

Next, referring to the drawings, the embodiments of the present invention will be described.

(first embodiment)

FIG. 1 is a block configuration diagram of an inverter device to which the control device 4 according to the first embodiment is applied. In FIG. 1 , an inverter unit 1 is composed of a plurality of switching elements, and outputs an AC voltage of variable frequency and variable voltage. As the three-phase motor driven by the output of the inverter unit 1 , there are widely used induction motors, synchronous motors, and the like. The DC power supply 3 supplies power to the inverter unit 1, and here, it passes a reactor (reactor) 3b, uses an electrolytic capacitor (condenser) 3d, and passes the single-phase AC power supply 3a through a diode bridge (diode bridge) ) 3c is realized after obtaining the pulsating current and voltage smoothing after full-wave rectification.

The control device 4 uses an A/D (Analog-Digital) converter 41 that converts the output voltage of the DC power supply 3 into a digital signal, and detects the imbalance of the AC motor based on the magnitude of the ripple component contained in the signal from the A/D converter 41. The out-of-adjustment state detection unit 42 of the state and the drive signal calculation unit 43 for calculating the PWM signal for driving the inverter unit 1 are constituted.

When the out-of-tuning detection unit 42 detects the out-of-tuning, it sends a signal to the drive signal computing unit 43 to increase the applied voltage supplied to the motor 2 by one step. The out-of-adjustment state detection unit 42 and the drive signal calculation unit 43 are implemented using a microcomputer. In addition, the drive signal calculation unit 43 for generating the PWM signal has a well-known structure, so it will not be described in detail.

Next, the operation of the inverter device shown in FIG. 1 will be described. In the output voltage of the DC power supply 3 (voltage across the electrolytic capacitor 3d) obtained by full-wave rectification of the single-phase AC power supply 3a, an AC component (hereinafter referred to as "ripple") of a frequency component twice the frequency of the AC power supply is included. (ripple voltage"). The current waveform flowing into the motor 2 and the pulsating current-voltage waveform included in the voltage across the electrolytic capacitor 3d are as shown in FIG. 2 . As can be seen from FIG. 2, when the frequency of the AC power supply 3a is 50 Hz, the terminal voltage of the electrolytic capacitor 3d includes a ripple voltage of 100 Hz.

FIG. 3 shows the current waveform of the current flowing into the motor 2 and the ripple current-voltage waveform of the electrolytic capacitor 3d when the motor 2 is out of tune. As can be seen from FIG. 3 , the voltage across the electrolytic capacitor 3d when an imbalance occurs has a pulsating current-voltage waveform in which a low-frequency pulsating current component caused by distortion of the current waveform of the motor 2 due to the imbalance is superimposed on the 100 Hz ripple voltage. .

Therefore, by detecting the presence or absence of such a low-frequency pulsating current-voltage component contained in the voltage across the electrolytic capacitor 3d, it is possible to detect the presence or absence of an imbalance in the motor 2. Next, using the flow chart of FIG. 11 , the detection and control of the occurrence of the imbalance by the imbalance state detection unit 42 will be described in detail.

First, in step S1, the value of n is initialized to 0. In step S2, data for 10 ms is obtained from the signal obtained by the A/D converter 41, and this 10 ms is one period (1000 ms/100) of the 100 Hz ripple voltage. In step S3, the maximum value (Vppmax) and the minimum value (Vppmin) are detected and stored from these acquired data.

In step S4, increase the value of n by 1; in step S5, determine whether the value of n becomes 10? Until the value of n becomes 10, the flow (flow) of step S2 - step S4 is repeated. When the value of n becomes 10, that is, the process of step S2 to step S4 is repeated 10 times, and the detected data is selected from the detected 10 maximum values Vppmax during the period of 100mS (10mS×10 times). Output the maximum value Vppmax.max and the minimum value Vppmin.min. Similarly, the maximum value Vppmax.max and the minimum value Vppmin.min are selected from the detected 10 minimum values Vppmin.

The period for judging the out-of-tuning is set to be longer than the period of the low-frequency pulsating current caused by the out-of-tuning, for example, 100 mS (that is, the count value (count) of n is set to 10). But it is not limited to this.

In step S7, calculate the difference (Vppmax.max-Vppmax.min) between the maximum value of Vppmax and the minimum value, or the difference (Vppmin.max-Vppmin.min) between the maximum value and the minimum value of Vppmin; In step S7, It is judged whether any of these differences is above a predetermined value.

When these differences are smaller than the predetermined value, it is judged that there is no imbalance, and the process returns to step S1, and the above-mentioned operations are repeated again. When these differences are greater than a predetermined value, it is judged that an imbalance has occurred, and a predetermined control signal for increasing the applied voltage supplied to the motor 2 by one step is sent to the drive signal calculation unit 43, thereby correcting the PWM from the drive signal calculation unit 43 in step S8. signal, the inverter unit 1 outputs a voltage raised by one stage.

Then, it returns to step S1, and the control of said step S1 - step S7 is repeated. At this time, if it is determined in step S7 that an out-of-tuning has occurred, the applied voltage is further increased by one step in step S8. The control of step S1 to step S8 is repeated until such an imbalance is suppressed.

As a result, after the imbalance of the motor 2 is suppressed, the current waveform of the motor 2 and the voltage waveform across the electrolytic capacitor become the state shown in FIG. 2, and the motor 2 continues to operate in this state.

Thus, by using the AC motor control device of this embodiment, the occurrence of out-of-tuning can be detected and reliably suppressed with a simple structure, thereby reducing the vibration of the AC motor 2 . Therefore, it is possible to reliably reduce the vibration of the AC motor 2 with a simple structure, and to provide a control device for the AC motor with a simple structure and high reliability.

(second embodiment)

FIG. 4 is a block configuration diagram of an inverter device using the control device 4 according to the second embodiment. Compared with Fig. 1, the difference lies in the structure that the DC power is obtained from the 3-phase AC power supply 3e. In FIG. 4, the DC power supply 3 is realized by smoothing the pulsating current and voltage after full-wave rectification by a diode bridge 3g by using a reactor 3f and an electrolytic capacitor 3h.

FIG. 5 shows the waveform of the current flowing into the motor 2 and the voltage waveform across the electrolytic capacitor 3h when no imbalance occurs. Compared with Fig. 2, it can be seen that when the power supply is 3-phase, after selecting an appropriate value for the reactor 3f, there is almost no ripple voltage.

FIG. 6 shows the waveform of the current flowing into the motor 2 and the voltage waveform across the electrolytic capacitor 3h when an imbalance occurs. At this time, as in FIG. 3 , the pulsating voltage waveform is superimposed with the low-frequency pulsating current component of the distortion of the current waveform of the motor 2 caused by the imbalance.

The control device 4 according to the second embodiment is also employed in the inverter device of FIG. 4 . As described in the first embodiment, the presence or absence of out-of-tuning is detected, and if out-of-tuning is detected, the voltage applied to the motor 2 is raised by one step.

This control device 4 of FIG. 4 is basically the same as the control device of FIG. 1 . However, in the inverter device shown in Fig. 4, since there is no ripple voltage in the DC output voltage as shown in Fig. The data acquisition period in S2 is fixed at 10 mS.

Also in this inverter device, as in the first embodiment, the occurrence of out-of-tuning can be detected with a simple structure and can be reliably controlled, so that the vibration of the motor 2 can be reduced.

(third embodiment)

FIG. 7 is a block configuration diagram of an inverter device using the control device 4 according to the third embodiment. An output voltage storage unit 44 is provided instead of the out-of-adjustment state detection unit 41 in FIG. The A/D converter 41 sends it to the drive signal calculation unit 43 . The output voltage storage unit 44 presets and stores an output voltage value of the inverter unit 1 necessary for the inverter unit 1 to control the out-of-tuning state of the motor 2 .

Next, the control operation of the inverter device shown in FIG. 7 will be described. The drive signal calculation unit 43 calculates a PWM signal to be output to the inverter unit 1 based on the detected DC voltage value and the output voltage value set and stored in the output voltage storage unit 44 .

Here, after the voltage value of the single-phase AC power supply 3a drops, the DC voltage value of the DC power supply 3 also drops. The drive signal calculation unit 43 corrects the PWM signal and increases its tuty so that the inverter unit 1 always outputs the output voltage value set by the output voltage storage unit 44 to the motor 2 . In addition, conversely, when the DC voltage value of the DC power supply 3 also rises, the drive signal calculation unit 43 corrects the PWM signal and reduces its function so that the voltage output by the inverter unit 1 is consistent with the setting of the output voltage storage unit 44. The values are equal.

As a result, since the motor 2 is always supplied with a voltage that does not cause an imbalance, the occurrence of the imbalance can be suppressed at all times without being affected by fluctuations in the DC power supply 3 .

The inverter device in FIG. 8 is a block diagram showing a three-phase AC power supply as in FIG. 4 . In this case, the occurrence of imbalance can also be controlled by the same operations as the inverter device in FIG. 7 .

In summary, the AC motor control device according to the third embodiment can reliably control the occurrence of out-of-tuning and reduce the vibration of the motor 2 with a simple structure and control regardless of fluctuations in the DC voltage. Therefore, when the power supply fluctuates, the vibration of the motor 2 can be effectively reduced by using a simple structure and control, and a control device for an AC motor with simple structure and control, strong anti-interference performance, and high reliability can be provided.

(fourth embodiment)

FIG. 9 is a block configuration diagram of an inverter device employing a control device according to a fourth embodiment, in which a DC average value calculation unit 45 is added compared to the configuration of FIG. 7 . It detects the DC voltage of the DC power supply 3 at a predetermined time, calculates the average value of the M latest data detected, and supplies it to the drive signal calculation unit 43 . The control content in the drive signal calculation section 43 is the same as the situation of Fig. 9, but after adding the DC average value calculation section 45, it has the following advantages:

When an imbalance occurs, as shown in FIG. 3 , the DC voltage value of the DC power supply 3 is superimposed on the ripple voltage by a low-frequency pulsating voltage caused by distortion of the current waveform. On the other hand, the DC average calculation unit 45 calculates the average value of the DC voltage values detected a plurality of times over a period of time longer than the low-frequency period caused by such an imbalance. That is, the average calculation period of the DC voltage value is made longer than the low-frequency pulsation period caused by the imbalance.

As a result, even if the difference between the maximum value Vppmax.max and the minimum value Vppmax.min shown in the first embodiment, or the difference between the maximum value Vppmin.max and the minimum value Vppmax.min is below a predetermined value, that is, even if the low-frequency pulsation is still Since the current and voltage values can be stably detected even when there is some residual, the output voltage of the inverter can be more reliably corrected to the value set by the output voltage storage unit 44 and stable operation can be performed.

The inverter device in FIG. 10 is a block configuration diagram when the AC power supply in FIG. 9 is used as three phases. In this case, the same control as in FIG. 9 can be used to stably control the imbalance.

As described above, according to the fourth embodiment, the occurrence of out-of-tuning can be reliably and stably controlled and the vibration of the motor 2 can be reduced with a simple structure and control regardless of fluctuations in the DC voltage. Therefore, when the power supply voltage fluctuates, the simple structure and control can also be used to effectively and stably reduce the vibration of the motor 2, providing an AC motor control device with simple structure and control, strong anti-interference performance, and high reliability.

Claims (2)

1. A control device for an inverter device, which is a control device for an inverter device that uses a DC voltage as an input and an AC motor as a load, and is characterized in that: The control device includes, in addition to a drive signal calculation unit that calculates and outputs a drive signal for an inverter unit that converts an AC voltage to a variable frequency and variable voltage, a voltage detection unit that detects the DC voltage. ; and an output voltage storage unit that pre-sets and stores a required output voltage value in order to control the unbalanced state of the AC motor, When the value of the detected DC voltage fluctuates, the drive signal calculation unit corrects the drive signal to cause the inverter unit to output an output voltage value preset and stored in the output voltage storage unit. 2. The control device of the inverter device according to claim 1, further comprising: acquiring the voltage detected by the voltage detecting means at a predetermined time, and calculating the average value of the newly acquired M pieces. DC average calculation unit.

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