JP3748560B2 - Inverter control device - Google Patents

Description

  The present invention relates to an inverter control device that converts a DC voltage into an AC voltage having a variable frequency and a variable voltage to drive an AC motor at a variable speed.

  When an AC motor is driven by an inverter device, there is a so-called turbulence phenomenon in which an applied voltage distortion due to a dead time of a PWM signal that drives an inverter unit, an impedance of an AC motor, an inertia moment, etc. are intertwined in a complex manner and current waveforms periodically oscillate. May occur. This is a phenomenon that occurs frequently particularly in a low load and low frequency range because the AC motor becomes large in size.

  Occurrence of this turbulence causes vibration in the AC motor itself, and depending on the degree of vibration, it may be difficult to continue operation. As a method for suppressing such a turbulence phenomenon, there is a method for correcting an output voltage error due to a dead time of an inverter PWM signal, which is one of the causes of turbulence. As an example of this, the following method is known (for example, Non-Patent Document 1).

  In this method, a current sensor for detecting the current of the AC motor is provided, and the distortion of the applied voltage is suppressed by correcting the inverter PWM signal in accordance with the current phase of the AC motor detected by the current sensor. This suppresses the occurrence of turbulence and suppresses vibration of the AC motor.

Further, the following method is known as a method for detecting and suppressing the occurrence of turbulence (see, for example, Patent Document 1). As shown in FIG. 12, a current sensor 103 for detecting a current value flowing in the compressor 102 driven by the inverter unit 101 of the inverter device is provided. The alternating-current unit turbulence determination unit 104 determines the state of turbulence based on the current fluctuation rate detected by the current sensor 103. When it is determined that the AC unit turbulence generating unit 104 is in a turbulent state, the output voltage change commanding unit 105 works to increase the voltage command value. The waveform calculation unit 106 calculates the necessary PWM pulse width from the output voltage value and the output frequency command value from the output voltage change command unit 105 to drive the inverter unit 101. With this configuration, the compressor 102 is restrained from turbulence and vibration.

Nikkan Kogyo Shimbun “Inverter Drive Handbook”, page 512 “Dead Time Correction Method” Japanese Patent Laid-Open No. 10-23789 ([0018], FIG. 1)

  However, the above-mentioned Non-Patent Document 1 has a problem that although a turbulence is suppressed by correcting the voltage distortion due to dead time, a current sensor is required, and the inverter device is increased in size and cost.

  Similarly, Patent Document 1 also requires a current sensor, resulting in an increase in the size and cost of the device, and also when a resistor is used as the current sensor, an amplifier circuit is required, increasing the number of parts and increasing the size of the device. Furthermore, this configuration has a problem that accurate control is difficult due to the influence of fluctuations in the power supply voltage.

The present invention solves such conventional problems, and an object of the present invention is to provide a control device for an inverter device that can detect turbulence with a simple configuration and can reliably suppress turbulence. And

  The inverter device receives a DC voltage as input and supplies AC power to an AC motor serving as a load. As a control device for the inverter device, in the present invention, voltage detection means for detecting the DC voltage separately from the drive signal calculation means for calculating and outputting a drive signal for the inverter unit that converts to an AC voltage of variable frequency and variable voltage. And a turbulence state detection means for detecting the turbulence state of the AC motor from the magnitude of the pulsation component included in the detected DC voltage. When the turbulence state is detected by the turbulence state detection means, the drive signal calculation means corrects the drive signal so as to increase the output voltage of the inverter unit.

  With the above-described configuration, it is possible to suppress the occurrence of turbulence and reduce the vibration of the AC motor, and it is possible to provide a control device for the AC motor that has a simple configuration and is inexpensive and highly reliable.

As will be apparent from the following embodiments, the invention according to claim 1 is characterized in that, in addition to the drive signal calculation means, the control device includes a voltage detection means for detecting the DC voltage, and a pulsation component included in the detected DC voltage. of a hunting state detection means for detecting a hunting state of the AC motor from the magnitude, when the hunting state is detected, the output voltage is raised to the inverter is obtained by so as to suppress the hunting, the The turbulence state detection means detects the maximum value Vppmax and the minimum value Vppmin by the voltage detection means during a predetermined period, repeats this detection N times, and further determines the maximum value Vppmax, max obtained from the N maximum values Vppmax. And the difference between the minimum value Vppmax, min and the minimum value Vppmin, min, or the difference between the maximum value Vppmin, max further determined from the N minimum values Vppmin and the minimum value Vppmin, min A turbulent state is detected when the value is equal to or greater than a predetermined value. As a result, there is an effect that it is possible to provide an AC motor control device that is inexpensive, simple in configuration, and high in reliability.

According to a third aspect of the present invention, in addition to the drive signal calculation means, the control device is preliminarily provided with a voltage detection means for detecting the DC voltage, and an output voltage value necessary for suppressing the turbulent state of the AC motor. Output voltage storage means for setting and storing, and when the detected DC voltage value fluctuates, the output voltage value preset and stored in the output voltage storage means is output. Therefore, it is possible to provide an AC motor control device that is highly stable, inexpensive, easy to configure and control, strong against disturbance, and highly reliable.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block 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 alternating voltage of variable frequency and variable voltage. An induction motor or a synchronous motor is used as the three-phase motor 2 driven by the output of the inverter unit 1. The DC power supply 3 supplies power to the inverter unit 1, and here, the pulsating voltage obtained by full-wave rectification of the single-phase AC power supply 3a through the reactor 3b by the diode bridge 3c is smoothed by the electrolytic capacitor 3d. It is realized by doing.

The control device 4, an A / D converter 41 for converting the output voltage of the DC power source 3 into a digital signal, A / D converter of the pulsating component contained in the signal from the 41 magnitude than detecting a hunting state of the AC motor And a drive signal calculation unit 43 for calculating a PWM signal for driving the inverter unit 1.

  When the turbulence state detection unit 42 detects turbulence, a signal for increasing the voltage applied to the motor 2 by one step is sent to the drive signal calculation unit 43. The turbulence state detection unit 42 and the drive signal calculation unit 43 are realized using a microcomputer. The drive signal calculation unit 43 that generates the PWM signal has a well-known configuration, and a detailed description thereof is omitted.

  Hereinafter, the operation of the inverter device of FIG. 1 will be described. The output voltage of the DC power supply 3 (the voltage across the electrolytic capacitor 3d) obtained by full-wave rectification of the single-phase AC power supply 3a includes an AC component (hereinafter, ripple voltage) having a frequency component twice the AC power supply frequency. It is. FIG. 2 shows a waveform of a current flowing through the motor 2 and a pulsating voltage waveform included in the voltage across the electrolytic capacitor 3d. As shown in 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 is a diagram illustrating a waveform of a current flowing through the motor 2 and a pulsating voltage waveform of the electrolytic capacitor 3d when turbulence occurs in the motor 2. As can be seen from FIG. 3, a low-frequency pulsating component caused by current waveform distortion of the motor 2 caused by the turbulence is superimposed on the voltage across the electrolytic capacitor 3d when the turbulence occurs in addition to the ripple voltage of 100 Hz. A pulsating voltage waveform is obtained.

  Therefore, the presence / absence of turbulence in the motor 2 can be detected by detecting the presence / absence of the low-frequency pulsating voltage component included in the voltage across the electrolytic capacitor 3d. Hereinafter, detection of turbulence and suppression of turbulence in the turbulence state detection unit 42 will be described in detail with reference to the flowchart of FIG.

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

In step S4, the value of n is incremented by 1, and in step S5, it is determined whether the value of n has become 10, and the flow of steps S2 to S4 is repeated until the value of n becomes 10. When the value of n reaches 10, that is, when the flow from step S2 to step S4 is repeated 10 times and data is detected for a period of 100 mS (10 mS × 10 times), the maximum value detected by 10 A maximum value Vppmax, max and a minimum value Vppmax, min are further selected from Vppmax. Similarly, a maximum value Vppmin, max and a minimum value Vppmin, min are further selected from the ten detected minimum values Vppmin .

  The period for determining the turbulence is set to, for example, 100 mS (that is, the count value of n is 10) as the low-frequency pulsating flow period or more generated by the turbulence, but is not limited thereto.

  In step S7, the difference between the maximum value and the minimum value of Vppmax (Vppmax, max−Vppmax, min) or the difference between the maximum value and the minimum value of Vppmin (Vppmin, max−Vppmin, min) is calculated. Then, it is determined whether one of these differences is a predetermined value or more.

  If the difference is less than the predetermined value, it is determined that no turbulence has occurred, the process returns to step S1, and the above-described operation is repeated. On the other hand, when the difference between them is equal to or greater than a predetermined value, it is determined that a turbulence has occurred, and a predetermined control signal for increasing the voltage applied to the motor 2 by one step is sent to the drive signal calculation unit 43. As a result, in step S8, the PWM signal from the drive signal calculation unit 43 is corrected, and a voltage increased by one step from the inverter unit 1 is output.

  Thereafter, the process returns to step S1, and the above-described control of steps S1 to S7 is repeated. Even in this case, if turbulence is determined in step S7, the applied voltage is further increased by one step in step S8. The control in steps S1 to S8 is repeated until such irregularity is suppressed.

  As a result, when the turbulence of the motor 2 is suppressed, the current waveform of the motor 2 and the voltage waveform across the electrolytic capacitor are as shown in FIG. 2, and the operation of the motor 2 is continued in this state.

  As described above, according to the control apparatus for an AC electric motor of the present embodiment, the occurrence of turbulence can be detected with a simple configuration and can be reliably suppressed, so that vibration of the motor 2 can be reduced. . Therefore, since the vibration of the motor 2 can be reliably reduced with a simple configuration, it is possible to provide an AC motor control device with a simple configuration and high reliability.

(Embodiment 2)
FIG. 4 is a block configuration diagram of an inverter device to which the control device 4 according to the second embodiment is applied, and is different from FIG. 1 in that the DC power source 3 is obtained from a three-phase AC power source 3e. . In FIG. 4, a DC power supply 3 is realized by smoothing a pulsating voltage obtained by full-wave rectification of a three-phase AC power supply 3e by a diode bridge 3g by a reactor 3f and an electrolytic capacitor 3h.

  FIG. 5 is a diagram showing a waveform of a current flowing through the motor 2 and a voltage waveform across the electrolytic capacitor 3h when no turbulence occurs. As can be seen from comparison with FIG. 2, when the power source is three-phase, almost no ripple voltage is generated by selecting the reactor 3f to an appropriate value.

  FIG. 6 is a diagram illustrating a waveform of a current flowing through the motor 2 and a voltage waveform across the electrolytic capacitor 3h when turbulence occurs. In this case as well, a pulsating voltage waveform in which a low-frequency pulsating component due to current waveform distortion of the motor 2 caused by turbulence is superimposed is obtained as in FIG.

  Also in the inverter apparatus of FIG. 4, by adopting the control apparatus 4 according to the second embodiment, it is detected whether or not the turbulence has occurred, and the turbulence is detected as described in the first embodiment. Then, the voltage applied to the motor 2 is increased by one step.

  The control device 4 of FIG. 4 is basically the same as that of FIG. 1, but the inverter device of FIG. 4 does not include a ripple voltage in the DC output voltage as shown in FIG. Is not required to be equal to the ripple period, that is, it is not necessary to fix the data acquisition period in step S2 of FIG. 11 to 10 mS.

  In this inverter device as well, in the same way as in the first embodiment, the occurrence of turbulence can be detected with a simple configuration and can be reliably suppressed, so that the vibration of the motor 2 can be reduced.

(Embodiment 3)
FIG. 7 is a block diagram of an inverter device to which the control device 4 according to the third embodiment is applied. An output voltage storage unit 44 is provided in place of the turbulence state detection unit 42 in FIG. The signal is taken into the drive signal calculation unit 43 via the A / D converter 41. The output voltage storage unit 44 sets and stores in advance the output voltage value at the inverter unit 1 necessary for the inverter unit 1 to suppress the turbulent state of the motor 2.

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

Here, when the voltage value of the single-phase AC power supply 3a decreases, the DC voltage value of the DC power supply 3 also decreases. The drive signal calculation unit 43 corrects the PWM signal to increase its duty so that the inverter unit 1 always outputs the output voltage value set in the output voltage storage unit 44 to the motor 2. Conversely, when the DC voltage value of the DC power supply 3 increases, the drive signal calculation unit 43 corrects the PWM signal so that the voltage output from the inverter unit 1 becomes the set value of the output voltage storage unit 44. Reduce the duty.

  As a result, since a voltage that does not always cause turbulence is applied to the motor 2, the occurrence of turbulence can always be suppressed without being affected by fluctuations in the DC power supply 3.

  The inverter device of FIG. 8 is a block configuration diagram showing a case where the AC power supply has three phases as in FIG. 4. In this case as well, the occurrence of turbulence can be suppressed by the same control as the inverter device of FIG. it can.

  As described above, according to the control device for an AC electric motor of Embodiment 3, the occurrence of turbulence can be reliably suppressed with a simple configuration and control regardless of the fluctuation of the DC voltage. Can be reduced. Therefore, since the vibration of the motor 2 can be reliably reduced by a simple configuration and control even when the power supply voltage fluctuates, the configuration and control of the device is simple, resistant to disturbance, and highly reliable AC motor control device. be able to.

(Embodiment 4)
FIG. 9 is a block configuration diagram of an inverter device to which the control device 4 according to the fourth embodiment is applied. Compared with the configuration of FIG. 7, a DC average value calculation unit 45 is added. This detects a DC voltage of the DC power source 3 at a predetermined timing, calculates the detected M average values, and supplies them to the drive signal calculation unit 42. The control content in the drive signal calculation unit 43 is the same as that in FIG. 9, but the provision of the DC average value calculation unit 45 provides the following advantages.

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

  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 Vppmin, min is equal to or less than a predetermined value. That is, even if a low-frequency pulsation remains, the DC voltage value can be detected stably, so that the output voltage of the inverter 1 can be more reliably corrected to the value set in the output voltage storage unit 44. And stable operation can be performed.

  The inverter device of FIG. 10 is a block configuration diagram in which the AC power supply is three-phased in FIG. 9, and in this case as well, turbulence can be stably suppressed by the same control as in FIG.

  As described above, according to the fourth embodiment, the occurrence of turbulence can be reliably and stably suppressed with a simple configuration and control regardless of fluctuations in the DC voltage, so that the vibration of the motor 2 can be reduced. Can do. Therefore, since the vibration of the motor 2 can be reliably and stably reduced by a simple configuration and control even when the power supply voltage fluctuates, the configuration and control of the apparatus is simple, strong against disturbance, and more reliable control of the AC motor. An apparatus can be provided.

Block configuration diagram of a device to which the control device according to the first embodiment of the present invention is applied. The figure which shows the electric current waveform which flows into the motor 2, and the voltage waveform across the electrolytic capacitor 3d The figure which shows the electric current waveform which flows into the motor 2, and the voltage waveform across the electrolytic capacitor 3d The block block diagram of the apparatus to which the control apparatus by Embodiment 2 of this invention is applied. The figure which shows the electric current waveform which flows into the motor 2, and the voltage waveform of both ends of the electrolytic capacitor 3h The figure which shows the electric current waveform which flows into the motor 2, and the voltage waveform of both ends of the electrolytic capacitor 3h The block block diagram of the apparatus to which the control apparatus by Embodiment 3 of this invention is applied. The block block diagram which shows another form in Embodiment 3. FIG. The block block diagram of the apparatus to which the control apparatus by Embodiment 4 of this invention is applied. The block block diagram which shows another form in Embodiment 4. FIG. The flowchart which showed operation | movement of the control apparatus of FIG. Block configuration diagram showing a conventional AC motor control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter part 2 Motor 3 DC power source 3a Single phase AC power source 3b Reactor 3c Single phase diode bridge 3d Electrolytic capacitor 3e Three phase AC power source 3f Reactor 3g Three phase diode bridge 3h Electrolytic capacitor 4 Controller 41 A / D converter 42 Disturbance state Detection unit 43 Drive signal calculation unit 44 Output voltage storage unit 45 DC average value calculation unit

Claims (4)

A control device for an inverter device having a DC voltage as an input and an AC motor as a load,
In addition to the drive signal calculation means for calculating and outputting a drive signal for the inverter unit that converts to an AC voltage of variable frequency and variable voltage, the control device includes a voltage detection means for detecting the DC voltage, and a detected DC voltage. A turbulence state detecting means for detecting the turbulence state of the AC motor from the magnitude of the pulsation component included,
The turbulence state detecting means detects the maximum value Vppmax and the minimum value Vppmin by the voltage detecting means during a predetermined period, and repeats this detection N times, and further determines the maximum value Vppmax, When the difference between max and the minimum value Vppmax, min is greater than or equal to a predetermined value, or the difference between the maximum value Vppmin, max further determined from the N minimum values Vppmin and the minimum value Vppmin, min is greater than a predetermined value Detect a turbulent state at
The control device for an inverter device, wherein the drive signal calculation means corrects the drive signal so as to increase an output voltage of the inverter unit when a turbulent state is detected. When said DC voltage is obtained from the single-phase AC, the predetermined period, the control unit of the inverter apparatus according to claim 1, wherein the one cycle of the ripple voltage contained in the DC voltage. A control device for an inverter device having a DC voltage as an input and an AC motor as a load,
The control device includes a voltage detection means for detecting the DC voltage, and a turbulence of the AC motor separately from a drive signal calculation means for calculating and outputting a drive signal for the inverter unit for converting to an AC voltage of variable frequency and variable voltage. Output voltage storage means for presetting and storing an output voltage value necessary for suppressing the state,
When the detected DC voltage value fluctuates, the drive signal calculation means corrects the drive signal so that the inverter unit outputs the output voltage value preset and stored in the output voltage storage means. Control device for inverter device. Control device for an inverter device according to any one of claims 1 to 3, wherein the incorporation of the detected voltage at a predetermined timing by the voltage detecting means further comprises a DC average value calculating means for calculating the latest M pieces of average values taken .

Images