JPH02179297A - Controller of inverter for driving ac motor - Google Patents

Abstract

PURPOSE:To eliminate a noisy electromagnetic vibration sound developed from an AC motor by controlling a PWM inverter, and varying the frequency of a ripple component contained in the motor current corresponding to a desired information sound. CONSTITUTION:When an accident occurs at a time t0, a current detection value if or a speed detection value omegaf exceeds a current limiting value iLIM or a speed limiting value omegaLIM to detect the overcurrent of the output current or the overspeed of a motor. Control periods TS1, TS2, TS3,..., TSn of abnormal operation state and data of continuing times L1, L2, L3,..., Ln are stored correspondingly in the data table 11 of a control period controller 10. When an abnormal operation state is detected, these data are called from an abnormal state detection processor 12, it is converted from a control period TSO in a normal operation state to control periods TS1, TS2,... in an abnormal operation state, and output. Thus, an electromagnetic sound can be controlled without altering the characteristics of the motor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for driving an AC motor such as an induction motor or a synchronous motor using a pulse width modulation inverter.
In particular, the present invention relates to a control device for an inverter for driving an AC motor, which is suitable for a motor drive system where motor noise is a problem.

[Conventional technology] As concerns about living and working environments increase, there is a strong desire to suppress noise in systems that use electric motors. The current noise countermeasures were to modify the electric motor itself and reduce the level of noise generated by it.

The results were far from satisfactory.

However, in recent years, pulse width modulation inverters (hereinafter referred to as PW
Motor systems using AC motors such as induction motors and synchronous motors driven by M inverters are becoming widely used. , P.W.
A method has been proposed in which the control frequency of the M inverter is increased to an inaudible frequency range, and a method in which the control frequency of the PWM inverter is changed so that it does not concentrate on the same frequency, thereby turning the motor noise into white noise. As an example, regarding the former, see Proceedings of the 1986 National Conference of the Institute of Electrical Engineers of Japan, No. 53.
5,536. It is described on pages 625 to 626, and the latter method is described, for example, in 1988 Institute of Electrical Engineers of Japan National Conference Lecture Proceedings No. 523, pages 619 to 620.

By the way, in such a system, if an overcurrent flows in the motor, overspeed occurs, or an abnormal condition occurs in the motor, this abnormal condition is detected and displayed on a display device, or an alarm is issued. It is common to have a device notify you.

[Problems to be Solved by the Invention] As the conventional noise countermeasures mentioned above, the former method does not take into consideration the generation of high-frequency electromagnetic noise caused by increasing the control frequency, resulting in the problem of radio interference. However, the latter method has the problem that even if the noise is turned into white noise, the total sound pressure level of the noise does not change, so a harsh sound still remains.

Furthermore, in the case of notifying an abnormal state of a motor, conventionally it is necessary to provide a display device or an alarm device, which poses a problem in that the device becomes expensive.

Therefore, one of the objects of the present invention is to make electromagnetic vibration noise generated from an AC motor less harsh on the ears.

Another object of the present invention is to use electromagnetic vibration noise generated from the AC motor to notify abnormal conditions of the AC motor.

[Means for Solving the Problems] Each of the objects of the present invention described above is to supply the output of an AC power source to an AC motor via a PWM inverter.
This is achieved by changing the frequency of the current ripple component included in the motor current in accordance with the information sound that is desired to be generated as the electromagnetic sound of the AC motor.

[Even if the ripple frequency included in the working motor current is changed, it is possible to prevent the motor's waste characteristics from changing much.

On the other hand, changing the ripple frequency included in the motor current changes the frequency of the electromagnetic sound generated by the motor.

Therefore, by controlling the PWM inverter and changing the frequency of the ripple component included in the motor current in response to the desired information sound, the motor can generate electricity without affecting the basic characteristics when driving the motor. It is possible to change electromagnetic sound into a desired information sound, and as a result, it is possible to prevent the electromagnetic sound of the electric motor from being perceived as harsh noise, suppressing the Ii sound, and converting this electromagnetic sound into one, for example, an alarm sound. It can be used as.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a control device for an AC motor inverter according to an embodiment of the present invention.

In this figure, 1 is a commercial three-phase AC power supply, 2 is an inverter device consisting of an inverter section 2a and a converter section 2b, and this inverter device 2 uses the output of the commercial three-phase AC power supply 1 as an input to generate voltages V o HVv, Vw. , frequency f1
outputs three-phase alternating current to drive a three-phase induction motor 3. 4
is a speed generator directly connected to the electric motor 3, 5 is a current detector,
6 is a base drive circuit, and 7 is a control circuit, and this control circuit 7 is composed of a PWM processing section 8, a command value generation processing section 9, a control period control section 10 consisting of a data table 11 and an abnormal state detection processing section 12. ing.

In the control unit circuit 7, when a driving command is input, a command value generation processing unit 9 generates a voltage command value v1 and an inverter voltage command value based on the current detection value i detected by the current detector and the speed generator 4, and the speed detection value ω1. Calculates the frequency command value f% and outputs these. In response to these open command values, the PWM processing section 8 generates a PWM signal. This PWM signal is applied via the base drive circuit 6 to each switching element constituting the inverter section 2a.

Figure 2 is a circuit configuration diagram of the inverter section 2a, Figure 3 (a)
-(d) are diagrams explaining the operation of the inverter section 2a, and the method of generating the PWM signal will be explained with reference to these diagrams.

The switching states of each of the switching elements 81 to S of the inverter section 2a are (0, O, O).

(1,O,O), (1,1,O), (0,1,O).

(0,1,1), (0,0,1), (1,0,1).

(1, 1, 1), where 1: Positive side switching element conduction state, 0: Negative side switching element conduction state, Left side: U
There are eight types of phases, center: V phase, right side: W phase, and voltage vectors v0 to v corresponding to each of these states.
7 becomes as shown in FIG. 3(a). When the output voltage is a sine wave, the vector φ of the magnetic flux generated from the fixed and secondary windings of the three-phase induction motor 3 and interlinked with the rotating secondary winding or the rotating squirrel cage groove is shown in Figure 3(b). Draw a circle rotating with an angular velocity ω as shown in .

Angle Δθ at which the flux linkage vector φ advances during the control period T3
For example, as shown in FIG. 3(c), voltage vectors v0 to 7 are selected along the circle drawn by the flux linkage vector φ.

When -V, -V, and -V7 are selected, the relationship between the control pulse and the voltage vector is as shown in FIG. 3(d). Therefore, the PWM signal corresponding to the switching state corresponding to each voltage vector is transmitted to the PWM processing unit 8.
is output from.

FIGS. 4(a) to 4(d) are waveform diagrams showing control pulses, voltage vectors, output voltages, and output currents.

In the inverter operation cycle, if a voltage vector as shown in FIG. 4(b) is selected, the output phase voltage Vu,
Vv, Vw and output line voltage Vov are shown in Figure 4 (C),
It becomes as shown in (d). therefore.

The U-phase current of the electric motor 3 is as shown in FIG. 4(d), and the period of the current ripple is approximately proportional to the control period T1.

This current ripple electromagnetically vibrates the stator core of the electric motor 3 and generates noise, so noise is generated at a frequency that substantially matches the frequency of the current ripple, that is, the control frequency (1/T8).

On the other hand, the period T of the control pulse is determined by the control period control section 10. The abnormal state detection processing unit 12 constantly monitors the detected current value 11 and the detected speed value ω by comparing them with respective set limit values. , constant control period T5
Output.

Here, as shown in FIG. 5, an accident occurs at time t0, and the detected current value ir or the detected speed value ω1 changes at time t0.
When the current limit value i c+u or the speed limit value ω1 is exceeded at i, and an overcurrent in the output current or overspeed of the motor is detected, the subsequent control cycle is changed. Control period T in the operating state. Control cycle in abnormal operating state Ts1+ Tsxe T□,・
..., and the duration of each control cycle is set to L3M.... therefore,
The frequency of electromagnetic sound generated by an electric motor is 1/T s
From those that almost match o, 1/Tsx, 1/Ts
x, 1/Tss, . . . , the electromagnetic sound changes sequentially to substantially match x, 1/Tss, .

The control period control section 10 is provided in order to change the control period from the period of the normal operating state to the period of the abnormal operating state as described above. In the data table 11, as shown in FIG. 6, the control periods T□, T□, Tss in the abnormal operating state are
...T5 and its duration L engineering? I'gt
L31...Ll data is stored in correspondence, and when an abnormal operating state is detected, these data are called from the abnormal state detection processing section 12 and the control cycle in the normal operating state is The output is changed from T1° to the control period T 3 L t T s x + . . . in the abnormal operating state.

The range of change in the control cycle at this time is set to a time of 175 or less of one cycle of the inverter output frequency. Alternatively, the control frequency, which is the reciprocal of the control period, may be varied within a range of five times or more the inverter output frequency.

By doing so, the influence on the fundamental wave component of the output voltage and current of the inverter is suppressed, and it becomes possible to control electromagnetic noise without changing the characteristics of the motor.

The above processing is performed using a microcomputer, and the flow of this processing is shown in FIG.

When an abnormal operating condition is detected, data T1. , is loaded from the data table 11, and the control period is changed from T, to T, . Set the duration in the counter,
The control period remains T a s until L decreases to zero. That is, the frequency of the electromagnetic vibration sound of the motor is maintained at approximately 1/T. When the counter reaches zero, the next data is loaded and the electromagnetic sound at the frequency corresponding to that sampling period is maintained for that duration. Thereafter, the frequency of the electromagnetic sound changes in the same manner according to the data stored in the data table.

According to this embodiment, when an abnormal operating state is detected,
An alarm to notify this can be transmitted as a change in sound by using electromagnetic vibration sound generated by the electric motor. Therefore, there is no need to provide a special display device or warning device for notifying abnormal operating conditions as in the past, so the device can be provided at low cost.

FIG. 8 shows still another embodiment of the present invention, and is a block diagram of a control circuit when music is used as the information sound to be conveyed in a normal driving state.

The control period control unit 10 of the control circuit 7 has a data table 11
and a scale generation processing section 13. If the data of the control period Ts stored in this data table 11 is set to be limited to the time equivalent to one period of the frequency of each interval of the musical scale that makes up the music, the electromagnetic vibration sound of the electric motor can be approximately adjusted to the frequency of each interval of the musical scale. Can be matched.

Figure 9 shows the relationship between pitch and its frequency. For example, the standard tone (U) is 4407, which is a 3-octave higher (U).
is 8807, and by dividing this interval into 12 according to the frequency ratio shown in FIG. 11, the frequency of each pitch is determined. Therefore, by setting the reciprocal of this frequency as data for the control period T8 and changing the duration of each pitch in proportion to the length of the note, the electromagnetic vibration sound of the electric motor can be made into music.

According to this embodiment, the electromagnetic noise of the electric motor, which was conventionally a harsh noise, can be turned into music.

Note that by combining this embodiment with the multiplexing inverter shown in FIG. 8, it becomes possible to generate chords as electromagnetic sound, making it possible to create even more pleasant music.

Furthermore, in this embodiment, when the voltage is constant, the power of the electromagnetic sound of the motor is large at low frequencies and small at high frequencies. On the other hand, as shown in FIG. 10, it is known that the power spectrum distribution with respect to the frequency of a sound that is felt to be pleasant has a large power in a low frequency region and a small power in a high frequency region. Therefore, making electromagnetic vibration sound music as in this example is the 10th
It can be seen that it matches the power spectrum distribution shown in the figure and feels comfortable.

Next, FIG. 11 and FIG. 12 respectively show other embodiments of the present invention, in which the ripple frequency of the motor current is directly detected, and the desired ripple frequency is determined by the detection result. This is an embodiment in which the control period is controlled as given.

For this reason, first, the abnormal state result processing section 12 is used in the embodiment shown in FIG. 11, and the scale generation processing section 13 is used in the embodiment shown in FIG. , the ripple frequency f obtained from the ripple frequency detection unit 702.
, and perform proportional/integral calculations such as the following formula.

Find the control period T.

Δf,=l/Ts”−f−1/T,=to, ΔfP+KI Δf,dt, where, and Kl are a constant of proportionality and a constant of integration, respectively.

Next, the detection of the ripple frequency in the embodiments shown in FIGS. 11 and 12 is carried out using a method such as fast Fourier transform on current waveform data sampled at a frequency that is at least twice as abnormal as the ripple frequency expected in advance. This is done by frequency analysis using . As for the sample frequency at this time, the lowest audible frequency of the sound is 201
(Since it is about z, at least 40 Hz or higher (sampling period of 25 milliseconds) is required.

According to the embodiments shown in FIGS. 11 and 12.

The setting precision of the ripple frequency of the motor current is increased, and the frequency of the electromagnetic sound generated from the motor can be set with high precision to a value corresponding to desired information.

Next, FIGS. 13 and 14 show still other embodiments of the present invention. In these embodiments, first, the control period control section 1o
The command value of the current ripple frequency which is the output of x, s (
= 1. /'rs'') is input to the function generation processing section 705, and the allowable variation range Δi'' of the current ripple is outputted.

A PWM signal is obtained by comparison calculation processing from the instantaneous current command value 10 which is the output of the instantaneous current command generating section 704, the detected value if of the motor current, and the permissible change width Δ10 of the current ripple.

Now, as shown in Fig. 15, for the instantaneous current command value i°, the allowable change width Δ1 of the current ripple at the time of 1=10.
When changing 1 from Δi to Δ11, the frequency f of the current ripple changes from frl to fri.

Generally, if ∆i @ ∆i 1, then there is a relationship such as f, , > f, and therefore, the allowable change range of current ripple ∆1
1, the ripple frequency f1 of the motor current if can be made to match the desired value f%.

FIG. 16 shows another embodiment of the present invention, and is a circuit configuration diagram when applied to a multiplex inverter.

The inverter device 2o is composed of a plurality of unit inverters 20a to 2On having different operating phases, and their output voltages are combined by a multiplexing transformer 30 and supplied to the three-phase induction motor 3 to drive it. Although not particularly shown, each unit inverter has a first
A circuit corresponding to the control circuit shown in the figure is provided. Data tables 40a to 40n attached to each unit inverter 20a to 2On store control cycles and their durations as shown in FIG. The sound is a synthesis of frequencies that almost match the control frequency of the unit inverter.

According to this embodiment, the information sound generated as an electromagnetic sound when an abnormal operating state is detected can be made more complex than the above embodiment. For example, if the combination of frequencies to be synthesized matches the frequency components of the voice, the information sound can be converted into a voice message, such as ``There is a fire in the car'', making it easier to identify abnormal driving conditions. can be conveyed to.

By combining the embodiment shown in FIG. 16 with the embodiment shown in FIG. 8, it is possible to generate a chord as electromagnetic sound, and it is also possible to generate electromagnetic sound as more pleasant music.

On the other hand, when operating multiple AC motors in parallel, the
The embodiment shown in FIG. 8 may be used, that is, the outputs of the plurality of unit inverters 20a to 20n are independently supplied as they are to the plurality of three-phase induction motors 3a to 3n.

Furthermore, the present invention may be applied to equipment such as household goods that uses a PWM inverter domestic electric motor system, and by doing so, it is possible to generate an alarm, play various messages, or use BGM. (Bsck Grown
It is possible to easily obtain a device that can be effectively used as a sound source for D Music, etc., has no motor noise, and is easy to use.

Similarly, the present invention may be applied to a plant system using a PWM inverter-driven electric motor system, and in this case, it can be effectively used particularly for issuing an alarm when the system is abnormal.

[Effects of the Invention] As explained above, according to the present invention, the harsh electromagnetic vibration sound generated from an AC motor driven by a PWM inverter can be converted into various informational sounds such as pleasant music or an alarm sound to notify of abnormal conditions. Since it can be changed, the electromagnetic vibration sound can be made to stop being perceived as harsh noise, or can be used as an alarm sound.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a control device for an inverter for driving an AC motor according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram of an inverter section, and FIGS. Operation explanatory diagram, Figures 4 (a) to (d) are waveform diagrams showing control pulses, voltage vectors, output voltage and output current, Figure 5
Fig. 6 is an explanatory diagram of the operation when an abnormal operating state occurs, Fig. 6 is an explanatory diagram showing that there is no data table, Fig. 7 is a flowchart showing the processing contents when an abnormal operating state occurs, and Fig. 8 is an explanatory diagram of the operation when an abnormal operating state occurs. FIG. 9 is an explanatory diagram showing the relationship between pitch and frequency, FIG. 10 is a characteristic diagram of power spectrum distribution with respect to frequency of sound, and FIG. 12, 13, and 14 are block diagrams showing other embodiments of the present invention, FIG. 15 is a waveform diagram for explaining operation, and FIG. 16 is a diagram showing the present invention applied to a multiplex inverter. FIG. 17 is an explanatory diagram showing the contents of a data table, and FIG. 18 is a configuration diagram showing another embodiment in which the present invention is applied to a multiplex inverter. 1... Commercial three-phase AC power supply, 2... Inverter device, 3... Three-phase induction motor, 4...
...Speed generator, 5...Current detector, 7...
... Control circuit, 10 ... Control period control section, 1
1... Data table, 12... Abnormal state detection processing section, 13... Scale generation processing section. Figure 1 Figure 2: Imper 7M, 1. 5-Yukiwara Gokenrobutai 3: Totsuki Setsudo 7; Kari Juri Circuit 4: No fight and J Mei 1 Shoulder country 41 Mu, -a 10:
~Mori transfer fl morning'jt's 14 Tsuboi to f1 fig. (a) Katanobu) 8 enemy 4 (b) (c) (d) fig. fig. fig. Fig.4 illuura 675 arrogant guard 19 Fig.16 Fig.16

Claims (28)

[Claims] 1. In a device equipped with an AC motor supplied with power from an AC power supply via a pulse width modulation inverter, the pulse width modulation inverter is controlled so that the AC motor generates electromagnetic sound corresponding to desired acoustic information. A control device for an inverter for driving an AC motor, characterized by: 2. The invention according to claim 1, wherein the pulse width modulation inverter is controlled by means for controlling a ripple component of the current supplied to the alternating current motor. Inverter control device. 3. The invention according to claim 2, wherein the means for controlling the ripple component is configured to control the ripple component by changing at least one of a control period and a control frequency of the pulse width modulation inverter. A control device for an inverter for driving an AC motor. 4. The control device for an inverter for driving an AC motor according to any one of claims 1 to 3, wherein the desired acoustic information is configured to be any one of an alarm sound, a message, and music. . 5. In the invention of claim 3, the change in at least one of the control period and control frequency of the pulse width modulation inverter is performed within a range that does not affect the waveform of the fundamental wave of at least one of the inverter output voltage and output current. A control device for an inverter for driving an AC motor, characterized in that it is configured as follows. 6. In the invention according to claim 5, the control period of the inverter is within a range of 1/5 or less of one period of the fundamental wave of one of the inverter output voltage and output current, and the control frequency of the inverter is 5 times the fundamental wave frequency. A control device for an inverter for driving an AC motor, characterized by the above range. 7. In a device equipped with an AC motor that is supplied with power from an AC power source via a pulse width modulation inverter, so that a desired sound stored in advance is generated from the AC motor,
A control device for an inverter for driving an AC motor, characterized in that it is configured to control at least one of a control period and a control frequency of the pulse width modulation inverter. 8. An AC motor that is supplied with power from an AC power supply via a pulse width modulation inverter is provided with means for storing in advance a control cycle of the pulse width modulation inverter corresponding to the information sound to be generated, and the storage means stores the control cycle. A control device for an inverter for driving an AC motor, characterized in that the control period of the pulse width modulation inverter is changed according to the control period of the pulse width modulation inverter. 9. In the invention according to claim 8, the storage means is a means for storing not only the control period but also its duration,
A control device for an AC motor driving inverter, characterized in that it is configured to change the control cycle of the pulse width modulation inverter only during the duration according to the control cycle stored in the storage means. 10. In the invention according to claim 9, the storage means is means for storing a plurality of the control periods and the duration of each of these control periods, and the storage means stores the plurality of control periods and the duration of each of these control periods, and the storage means stores the plurality of control periods and the duration of each of the control periods, and 1. A control device for an AC motor inverter, characterized in that the control period of the pulse width modulation inverter is changed by each of the above-mentioned durations. 11. In the invention of claim 2, means for detecting the frequency of a ripple component included in the current supplied to the AC motor is provided, and the pulse width modulation inverter is controlled so that the frequency detected by the means becomes a desired frequency. A control device for an inverter for driving an AC motor, characterized in that it is configured to: 12. 12. The control device for an inverter for driving an AC motor according to claim 11, wherein the means for detecting the frequency of the ripple component comprises a current detector and a frequency analyzer. 13. 12. The control device for an AC motor driving inverter according to claim 11, wherein the current detection period by the means for detecting the frequency of the ripple component is 25 milliseconds or less. 14. In the invention of claim 2, means is provided for detecting the amplitude of the ripple component included in the current supplied to the AC motor, and the frequency of the ripple component is controlled by changing the allowable range of the amplitude. 1. A control device for an inverter for driving an AC motor, characterized in that: 15. 2. The control device for an inverter for driving an AC motor according to claim 1, wherein the pulse width modulation inverter is controlled by at least one of a control period and a control frequency of the inverter. 16. In a device equipped with an AC motor that is supplied with power from an AC power source via a pulse width modulation inverter, the electromagnetic noise generated by the AC motor can be used to control at least one of the operating state of the AC motor and the operating state of the load it drives. A control device for an inverter for driving an AC motor, characterized in that the control device is configured to control the pulse width modulation inverter so that it can be used as acoustic information to represent. 17. 17. The control device for an inverter for driving an AC motor according to claim 16, wherein the acoustic information is an alarm sound indicating an abnormality in at least one of the AC motor and the load. 18. 17. The control device for an inverter for driving an AC motor according to claim 16, wherein the acoustic information is a message indicating an operating state of at least one of the AC motor and the load. 19. 9. The inverter for driving an AC motor, wherein the information sound is music, and the control frequency corresponding to the control period is controlled to correspond to the frequency of each pitch of a musical scale. control device. 20. In the invention of claim 9. The information sound is music, and the control frequency corresponding to the control period and its duration are controlled in accordance with the frequency of each interval of a scale in the music and the length of the note thereof. A control device for an inverter that drives an AC motor. 21. In a device equipped with multiple units of AC motors that are supplied with power from an AC power supply via a pulse width modulation inverter, by changing the control frequency and duration of each pulse width modulation inverter of each unit, the AC motor of each unit can be 1. A control device for an inverter for driving an AC motor, characterized in that a synthesized sound of electromagnetic sounds generated from an electric motor is configured to provide desired acoustic information. 22. In the invention according to claim 21, means for detecting an abnormal state of the AC motor is provided, and the control period and duration of the pulse width modulation inverter of each of the units is changed in accordance with the abnormality detected by the means, so that the synthesis is performed. 1. A control device for an inverter for driving an AC motor, characterized in that the control device is configured to generate a sound as an alarm sound. 23. 23. The control device for an inverter for driving an AC motor according to claim 22, wherein the synthesized sound is a voice message. 24. In the invention of claim 21, the desired acoustic information is music, and the control frequencies and durations of the respective control frequencies corresponding to the control periods of the pulse width modulation inverters of the respective units are arranged in a chord relationship. 1. A control device for an inverter for driving an AC motor, characterized in that it is configured to control a pulse width modulation inverter. 25. The AC motor according to claim 3, wherein the frequency corresponding to the control period is changed in a decreasing direction in a region where the power of the electromagnetic sound is large, and in a rising direction in a region where the power is small. Control device for drive inverter. 26. 4. A control device for an inverter for driving an AC motor according to claim 3, further comprising a microcomputer that controls the control period and its duration. 27. 22. A control device for an inverter for driving an AC motor according to claim 21, further comprising a microcomputer that controls the control period and its duration in the unit. 28. 28. The control device for an inverter for driving an AC motor according to any one of claims 1 to 27, wherein the AC motor is a motor of a motor drive system that supplies power to an arbitrary load.