JPH0947026A - Pwm waveform generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise of air-conditioner by switching the carrier frequency at an interval shorter than one period of output voltage from a PWM control circuit thereby suppressing the carrier noise. SOLUTION: Upon receiving a timing signal T, a carrier frequency selecting section 6e selects a carrier frequency data among carrier frequency data fe1-fe4 according to a data select signal N and delivers the selected carrier frequency data to a carrier generating section 6c. The carrier generating section 6c delivers a carrier signal fc to a PWM waveform generating section 6d where the carrier signal fc is compared with a basic wave signal (f) based on a frequency command signal to and delivers a signal to a PWM control inverter circuit 3 through a transistor drive circuit 5. In this regard, the period of timing signal T being fed to the carrier frequency selecting section 6e is set at an appropriate value shorter than the period of output power from a current PWM control inverter circuit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on an air conditioner and uses PWM based on a carrier wave signal and a fundamental wave signal.
The present invention relates to a PWM control inverter device using a controlled PWM control inverter circuit, and in particular, by improving the tone of a carrier sound without extremely increasing the carrier frequency, it is possible to reduce the unpleasant sensation of hearing and equivalently. The present invention relates to a PWM waveform generation device capable of reducing noise in the entire air conditioner.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a configuration of a conventional PWM control inverter device. Here, there are various types such as a three-phase full bridge and a single-phase half bridge in the main circuit configuration of the inverter circuit, but since the present invention is not particularly affected by these various main circuit configurations, in the figure, A three-phase full-bridge voltage source inverter circuit commonly used for air conditioners is shown.

In the figure, 1 is an AC power supply, 2 is a rectifying circuit (converter), 3 is a PWM control inverter circuit, 4
Is a three-phase induction motor, 5 is a transistor drive circuit, and 6 is P
It is a WM waveform generator. The rectifier circuit 2 is composed of a diode bridge 2a, a reactor 2b, and a smoothing capacitor 2c, and the PWM control inverter circuit 3 is composed of a transistor which is a switching element and a flywheel diode (all signs are omitted). Also, PWM
The waveform generation device 6 includes a fundamental wave generation unit 6a, a storage unit 6b that stores carrier frequency data, and a carrier generation unit 6
c, a PWM waveform generator 6d.

Next, the operation will be described. In FIG. 9, a converter 2 forward-converts the AC power supply 1 into DC,
The M control inverter circuit 3 inversely converts the AC into an AC having an arbitrary frequency and an arbitrary voltage, and supplies the AC to the induction motor 4.

Here, the operation of the PWM waveform generator 6 will be described in detail. The carrier wave signal fc is generated by the carrier generator 6c based on the carrier frequency data stored in advance in the storage means 6b. The carrier wave signal fc may be a triangular wave or a sawtooth wave. Further, the fundamental wave signal f is generated by the fundamental wave generator 6a based on the frequency command signal fo. The PWM waveform generation unit 6d compares the carrier wave signal fc with the fundamental wave signal f to generate a PWM control signal. The PWM control signal is supplied to the PWM control inverter circuit 3 via the transistor drive circuit and drives the six transistors included in the PWM control inverter circuit 3.

In this way, the U-phase and V-phase of the induction motor 4
The PWM control inverter circuit 3 is provided at each phase terminal of the W phase and the W phase.
A pulsed phase voltage that is Vdc when the upper arm transistor is on and the lower arm transistor is off, and is 0 when the upper arm transistor is off and the lower arm transistor is on, corresponding to each phase of Waveform is applied. Therefore, the line voltage Vuv applied between the U-phase terminal and the V-phase terminal of the induction motor 4 also has a pulse voltage waveform, and the waveform of the fundamental wave component of this pulse-shaped line voltage waveform Vuv is the fundamental wave signal f. The waveform is almost the same. The same applies to the line voltage Vvw applied between the V-phase terminal and the W-phase terminal and the line voltage Vwu applied between the W-phase terminal and the U-phase terminal.

However, in principle of the PWM control inverter,
AC voltage Vuv, Vvw, V supplied to the induction motor 4
wu has almost the same waveform as the fundamental wave component f generated by the fundamental wave generation unit 6a as a fundamental wave component, but in addition, the frequency component of the carrier wave signal fc generated by the carrier generation unit 6c, that is, the carrier frequency Is a pseudo sine wave voltage waveform in which a harmonic component having a fundamental wave is superimposed.

[0008]

In this case, in a drive circuit of an induction motor which is generally used in an air conditioner, it is necessary to suppress the leakage current to a certain value or less and to suppress the switching loss of the PWM control inverter circuit. ,
The carrier frequency is several kHz to 10 kHz for reasons such as cost reduction of expensive switching elements and sharing of control of the PWM control inverter circuit and other air conditioner components with one control circuit. At present, it is unavoidable to set within the audible frequency range.

As described above, when the conventional PWM control inverter device shown in FIG. 9 is used to drive the induction motor with the pseudo sine wave voltage having the harmonic component of the carrier frequency, the influence of the harmonic component is generated. , The PWM control inverter circuit or the stator of the induction motor, or the power transmission line connecting the PWM inverter circuit and the induction motor is excited,
Generates electromagnetic noise (hereinafter referred to as carrier sound). The frequency component of this carrier sound is mainly composed of the fundamental wave component of the carrier frequency and its overtone component, and there are almost no other frequency components. Therefore, particularly when the frequency band of the carrier sound falls within the audible frequency range, as in the case of the PWM control inverter circuit mounted on the air conditioner, the sound becomes very offensive to the ear.

In order to prevent the annoyance of the carrier sound, recently, particularly in the field of general-purpose inverters, a high-speed switching element such as an IGBT is used to drive the carrier frequency from about 15 KHz to outside the audible frequency range. Although a carrier sound is generated, a noiseless inverter that is inaudible to the human ear has been put into practical use. However, in the case of the PWM control inverter circuit installed in the air conditioner, there are restrictions as the PWM inverter circuit for the air conditioner as described above,
It is difficult to simply set the carrier frequency outside the audible frequency range.

If the PWM control inverter circuits mounted on the air conditioner are classified according to the relationship between the carrier frequency and the frequency of the fundamental wave signal f, the carrier frequency is constant regardless of the frequency of the fundamental wave signal f. Can be classified into an asynchronous type and a synchronous type in which the carrier frequency is in an integral multiple of the frequency of the fundamental wave signal f. Incidentally, in the synchronous system, it is general to appropriately switch the magnification according to the frequency of the fundamental wave signal f so that the carrier frequency falls within the appropriate range described above.

At this time, in the synchronous system, the fundamental wave signal f
When the frequency changes, the carrier frequency changes stepwise, but the change occurs at a time interval sufficiently longer than the period of the fundamental wave signal f. Further, when operating at a constant frequency, the carrier frequency becomes constant. On the other hand, in the asynchronous system, the carrier frequency is constant regardless of the frequency of the fundamental wave signal f. That is, in any case, a constant carrier frequency is connected for a sufficiently long time as compared with the cycle of the fundamental wave signal f.

At this time, paying attention to the noise of the entire air conditioner, the frequency components of the noise generated by other than the PWM control inverter circuit, such as the mechanical noise emitted from the compressor and the wind noise of the blower, are All of them have a relatively low frequency and a wide range of frequency components, and are sounds close to so-called white noise. On the other hand, the frequency component of the carrier sound is composed of the carrier frequency and its overtone frequency, and each frequency component has a steep frequency characteristic with a high peak and a narrow tail. Moreover, the frequency component hardly changes for a long time as described above.

Therefore, the frequency distribution of the noise of the entire air conditioner has a sharp peak 9 of the carrier sound in the frequency distribution 8 close to the white noise due to the noise other than the carrier sound, as shown in the schematic diagram of FIG. , 10, 11 stand out. With respect to the noise of the air conditioner having such a frequency distribution, a carrier sound that does not fluctuate with time and has a sharp peak is particularly offensive to human hearing. In addition, even if the sound pressure level of the mechanical noise or wind noise generated from the compressor or blower becomes small, the sound pressure level of the carrier sound does not change so much. Is emphasized.

The present invention has been made to solve the above-mentioned problems of the prior art, and is mounted on an air conditioner, and PWM is performed based on a carrier wave signal and a fundamental wave signal.
Regarding a PWM control inverter device using a controlled PWM control inverter circuit, the frequency components of the carrier sound are dispersed to improve the timbre of noise including the carrier sound generated from the entire air conditioner to a timbre closer to white noise. By doing so, it is possible to reduce the uncomfortable feeling of the carrier sound, which was particularly offensive to the noise generated in the actual use state of the air conditioner, to a necessary and sufficient level, and equivalently, for the entire air conditioner. An object of the present invention is to provide a PWM waveform generation device capable of achieving low noise.

[0016]

In order to achieve the above-mentioned object, the present invention provides an air conditioner constructed by connecting a compressor, a condenser, a throttle device, an evaporator and the like with a refrigerant pipe,
A converter that is connected to an induction motor that is used as a power source for a compressor or a blower for a condenser or a blower for an evaporator, and a converter that converts AC power to DC power, and the output from the converter is variable voltage and variable by pulse width modulation control. A PWM control inverter circuit is configured together with a PWM control inverter circuit that converts the frequency to AC power and supplies the induction motor with a pulse width modulation waveform for controlling the PWM control inverter circuit. In the PWM waveform generation device for generating the carrier wave signal based on the signal, first carrier frequency switching means for appropriately switching the carrier frequency of the carrier wave signal at a time interval shorter than one cycle of the output power from the PWM control inverter circuit. It is equipped with a configuration.

Further, the first carrier frequency switching means in the above-mentioned structure has a carrier frequency setting means for presetting a plurality of carrier frequencies related to the carrier wave signal and a plurality of carrier frequencies for the carrier frequency setting means. The second carrier frequency switching means appropriately selects and switches the carrier frequency from the inside by open-loop feedforward control.

The second carrier frequency switching means in the above-mentioned configuration has a plurality of carrier frequency setting means and a selection order setting means for presetting a selection order of a plurality of carrier frequencies of the carrier frequency setting means. The third carrier frequency switching means for selecting and switching the carrier frequency at an appropriate timing from among the carrier frequencies according to the selection order of the selection order setting means.

Further, the third carrier frequency switching means in the above-mentioned configuration, from among the plurality of carrier frequencies of the phase angle calculation means for calculating the phase angle of the waveform relating to the fundamental wave signal and the carrier frequency setting means, It comprises fourth carrier frequency switching means for selecting and switching carrier frequencies at the timing for each phase angle calculated by the phase angle calculating means and in accordance with the selection order of the selection order setting means.

Further, the second carrier frequency switching means in the above-mentioned structure comprises a random order setting means for randomly setting the selection order of a plurality of carrier frequencies of the carrier frequency setting means, and a plurality of carrier frequency setting means. It comprises a fifth carrier frequency switching means for selecting and switching the carrier frequency from the carrier frequencies at an appropriate timing in accordance with the random selection order set by the random order setting means.

Further, the fifth carrier frequency switching means in the above-mentioned configuration is a weighted carrier frequency setting means for presetting a plurality of carrier frequencies weighted with respective selection frequencies for each carrier frequency, Timing calculation means for randomly calculating the carrier frequency switching timing, and random switching timing calculated by the timing calculation means from among the plurality of carrier frequencies of the weighted carrier frequency setting means, and by the random order setting means. And a sixth carrier frequency switching means for selecting and switching the carrier frequency according to the set random selection order.

Further, the first carrier frequency switching means in the above-mentioned configuration is the carrier frequency setting means for presetting a plurality of carrier frequencies related to the carrier wave signal, and the phase of the output power from the PWM control inverter circuit. The power phase angle detection means for detecting the angle, and the carrier frequency is appropriately adjusted by closed-loop feedback control based on the phase angle of the output power detected by the power phase angle detection means from among the plurality of carrier frequencies of the carrier frequency setting means. It comprises a seventh carrier frequency switching means for selecting and switching.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described in more detail with reference to the drawings. However, FIG. 1 and FIG.
In each of the embodiments shown in FIG. 7, the same components as those of the conventional PWM control inverter device shown in FIG.
It is shown using the same symbols as in FIG.

Embodiment 1 FIG. 1 is a configuration diagram of a PWM control inverter device according to a first embodiment of the present invention. The PWM control inverter device shown in FIG. 1 is a blower for a compressor or a condenser or a blower for an evaporator of an air conditioner configured by connecting a compressor, a condenser, a throttle device, an evaporator and the like with a refrigerant pipe. A converter 2 that is connected to a three-phase induction motor 4 that is used as a power source of each of the above (all of which are not shown) and that converts the AC power supply 1 into a DC power supply; It is composed of a PWM control inverter circuit 3 that converts the AC power of a variable frequency and supplies the AC power to the induction motor, a PWM waveform generation device 6-1 described later, and a transistor drive circuit 5. The PWM waveform generation device 6-1 generates a pulse width modulation waveform for controlling the PWM control inverter circuit 3 based on the calculated carrier wave signal fc and the fundamental wave signal f. Then, the PWM waveform generation device 6
-1 is a fundamental wave generator 6a, a carrier generator 6c,
In addition to the PWM waveform generator 6d, the preset 4
Types of carrier frequency data fc1, fc2, fc3
It is composed of a storage unit 6b that stores fc4 and a carrier frequency selection unit 6e. The carrier frequency related to the carrier wave signal is set to the output power (here, for example, voltage output) from the PWM control inverter circuit 3. The switching is appropriately performed at a time interval shorter than one cycle.

Next, the operation of this embodiment will be described in detail. The four types of carrier frequency data fc1, fc2, fc3, fc4 stored in the storage means 6b are input to the carrier frequency selection unit 6e, respectively. Further, the timing signal T and the data select signal N are input to the carrier frequency selection unit 6e.

The carrier frequency selecting section 6e (an example of first carrier frequency switching means) selects from among the carrier frequency data fc1, fc2, fc3, fc4 according to the data select signal N when the timing signal T is input. , Certain carrier frequency data is selected and switched, and is input to the carrier generator 6c.

Finally, the carrier generator 6c creates a carrier wave signal fc based on the carrier frequency data selected by the carrier frequency selector 6e, and the PWM waveform generator 6d.
To enter. The PWM waveform generation unit 6d compares the carrier wave signal fc described above with the fundamental wave signal f generated by the fundamental wave generation unit 6a based on the frequency command signal fo, and outputs the PWM control signal (PWM waveform signal). It is generated and output to the PWM control inverter circuit 3 via the transistor drive circuit 5.

At this time, the cycle of the timing signal T input to the carrier frequency selector 6e is set shorter than one cycle of the output power from the current PWM control inverter circuit 3,
And set it at an appropriate time interval. Further, the data select signal N input to the carrier frequency selection unit 6e may be data that is switched in a preset order,
Alternatively, the data may be switched in random order. FIG. 2 shows the relationship between one cycle of the output power from the PWM control inverter circuit 3 and the time interval for switching the carrier frequency in this case. As shown in the figure,
Time intervals for switching carrier frequencies t ₁ , t ₂ , ...
, T ₅ (or t ₆ , t ₇ , ..., T ₉ ) is
The output power is set to be extremely shorter than one cycle TO (or TO ₁ ). That is, even if the cycle of the output power changes, the carrier frequency is always switched at a time interval shorter than one cycle of the output power.

As described above, the PWM according to the first embodiment
The waveform generation device outputs the carrier frequency, which is an important factor for determining the tone color of the carrier sound generated in principle when the induction motor is driven using the PWM control inverter device, from the PWM control inverter circuit 3. By configuring to switch appropriately at a time interval shorter than one cycle of the output power, as shown in FIG. 3, as a harmonic component of the pseudo sine output of the PWM control inverter device,
By controlling a certain carrier frequency by dispersing and controlling it so that it is not continuously superimposed for a long time, the frequency distribution 9, 10, 11 of the carrier sound can be made closer to white noise and can be heard. It is intended to reduce the discomfort of. In this embodiment, the control mode for switching the carrier frequency may be an open loop feed forward method or a closed loop feedback method.

Example 2. FIG. 4 is a configuration diagram of a PWM control inverter device according to the second embodiment of the present invention. The PWM waveform generator 6-2 shown in FIG.
In addition to the carrier generator 6c and the PWM waveform generator 6d,
Three types of preset carrier frequency data fc
1, fc2, fc3, a preset data selection table, and a storage unit 6b (an example of a carrier frequency setting unit and a selection order setting unit) respectively storing preset timing data, and carrier frequency selection The section 6e, the data selector 6f for generating the data select signal N based on the data selector table stored in the storage means 6b, and the timer 6 for generating the timing signal T based on the timing data stored in the storage means 6b.
g. In this case, the control mode for switching the carrier frequency is based on the closed loop feedforward method.

Next, the operation of this embodiment will be described in detail. The three types of carrier frequency data fc1, fc2, fc3 stored in the storage unit 6b are input to the carrier frequency selection unit 6e. Further, the timing signal T and the data select signal N are input to the carrier frequency selection unit 6e.

Here, the data selector 6f repeatedly calls up the data select table stored in the storage means 6b, thereby, for example, fc1, fc2, fc.
3, fc1, fc2, fc3, ..., And the data select signal N that changes in a preset order is generated. The timer 6g also generates a timing signal T at regular time intervals based on the timing data stored in the storage means 6b.

Next, the carrier frequency selector 6e (second,
And an example of the third carrier frequency switching means),
When the timer 6g receives the timing signal T generated at regular intervals, the carrier frequency data is sequentially selected and switched according to the data select signal N generated by the data selector 6f and changing in a preset order.

Finally, the carrier generator 6c creates a carrier wave signal fc based on the carrier frequency data selected by the carrier frequency selector 6e, and the PWM waveform generator 6d.
To enter. The PWM waveform generation unit 6d compares the carrier wave signal fc described above with the fundamental wave signal f generated by the fundamental wave generation unit 6a based on the frequency command signal fo, generates a PWM control signal, and drives the transistor. PWM via circuit 5
Output to the control inverter circuit 3.

As described above, the PWM according to the second embodiment
As shown in FIG. 3, the waveform generation device is configured to sequentially switch the carrier frequency from among a plurality of preset carrier frequencies at a fixed timing in a preset order. As a harmonic component of the pseudo sine wave output of the PWM control inverter device, a specific carrier frequency is controlled so as not to be continuously superimposed for a long time. In the above embodiment, the carrier frequencies are switched according to a preset fixed order. However, the second carrier frequency switching means according to the present invention switches carrier frequencies according to a randomly set selection order. It doesn't matter.

Example 3. FIG. 5 is a configuration diagram of a PWM control inverter device according to the third embodiment of the present invention. The PWM waveform generator 6-3 shown in FIG.
In addition to the carrier generator 6c and the PWM waveform generator 6d,
Three types of preset carrier frequency data fc
1, fc2, fc3, a storage unit 6b that stores a preset data selection table, a carrier frequency selection unit 6e (an example of a fourth carrier frequency switching unit), and a data selection stored in the storage unit 6b. A data selector 6f that generates a data select signal N based on a table and a current phase angle of the fundamental wave signal f generated by the fundamental wave generator 6a based on the frequency command signal fo are calculated to set a preset constant angle. Timing signal T for each
Phase angle calculation unit 6h for generating (an example of phase angle calculation means)
It is composed of Here, the storage unit 6b and the data selector 6f constitute the selection order setting means according to the present invention. In this case, the control mode for switching the carrier frequency is based on the open loop feedforward method.

Next, the operation of this embodiment will be described in detail. The three types of carrier frequency data fc1, fc2, fc3 stored in the storage unit 6b are input to the carrier frequency selection unit 6e. Further, the timing signal T and the data select signal N are input to the carrier frequency selection unit 6e.

Here, the data selector 6f repeatedly calls the data select table stored in the storage means 6b in a fixed order, for example, fc1, f
A data select signal N that changes in a preset order, such as c2, fc3, fc1, fc2, fc3, ... Is generated. Further, the phase angle calculator 6h calculates the current phase angle of the fundamental wave signal f generated by the fundamental wave generator 6a based on the frequency command signal fo, and generates the timing signal T for each predetermined angle. .

Next, the carrier frequency selecting section 6e generates the data selector 6f at the time when the timing signal T generated by the timer 6g is input at a constant time interval.
Data select signal N that changes in a preset order
The carrier frequency data is sequentially switched in accordance with.

Finally, the carrier generator 6c creates a carrier wave signal fc based on the carrier frequency data selected by the carrier frequency selector 6e, and the PWM waveform generator 6d.
To enter. The PWM waveform generation unit 6d compares the carrier wave signal fc described above with the fundamental wave signal f generated by the fundamental wave generation unit 6a based on the frequency command signal fo, generates a PWM control signal, and drives the transistor. PWM via circuit 5
Output to the control inverter circuit 3.

As described above, the PWM according to the third embodiment
The waveform generator is a voltage-type PWM control inverter circuit 3
Calculate the phase angle of the output voltage waveform from, and for each constant phase angle, from among the preset multiple carrier frequencies,
Since the carrier frequencies are sequentially switched according to the preset order, as shown in FIG. 3, as a harmonic component of the pseudo sine wave output of the PWM control inverter device, a specific carrier frequency is The control is performed so as not to be continuously superimposed for a long time.

As a modification of the third embodiment, a carrier frequency is sequentially selected and switched from a plurality of preset carrier frequencies at random timing according to a preset order. At a constant timing, from among a plurality of preset carrier frequencies, a carrier frequency weighted with a preset occurrence frequency is sequentially selected and switched according to a preset order, or , At a random timing, from among a plurality of preset carrier frequencies, a carrier frequency weighted with a preset occurrence frequency is sequentially selected and switched according to a preset order. It is also possible to apply.

Example 4. 6 is a configuration diagram of a PWM control inverter device according to a fourth embodiment of the present invention. The PWM waveform generator 6-4 shown in FIG.
In addition to the carrier generation unit 6c, the PWM waveform generation unit 6d, and the carrier frequency selection unit 6e (an example of fifth and sixth carrier frequency switching means), three types of preset carrier frequency data fc1, fc2 are set. fc
3, a storage unit 6b that stores a data select table that gives a predetermined weight to the frequency of occurrence of the carrier frequency data fc1, fc2, and fc3, and a timing table that includes a plurality of preset timing data.
A data selector 6f for generating a data select signal N by calling data select data corresponding to the random number generated by the random number generator 6i from (an example of weighting carrier frequency setting means) and the data select table stored in the storage means 6b. And a timer 6g for generating timing signal T by calling timing data corresponding to the random number generated by random number generator 6j from the timing table stored in storage means 6b. That is, the random number generator 6i and the data selector 6f constitute the random order setting means according to the present invention. Further, the timer 6g and the random number generator 6j constitute timing calculation means based on this generation. In this case, the control mode for switching the carrier frequency is based on the open loop feedforward method.

Next, the operation of this embodiment will be described in detail. The three types of carrier frequency data fc1, fc2, fc3 stored in the storage unit 6b are input to the carrier frequency selection unit 6e. Further, the timing signal T and the data select signal N are input to the carrier frequency selection unit 6e.

Here, the data selector 6f calls the data select data corresponding to the random number generated by the random number generator 6i from the data select table stored in the storage means 6b, and generates the data select signal N. However, as described above, this data selection table is such that the frequency of occurrence of carrier frequency data is given a certain weight in advance.

Further, the timer 6g calls a timing chart corresponding to the random number generated by the random number generator 6j from the timing table stored in the storage means 6b, and generates a timing signal T.

Next, the carrier frequency selector 6e generates random and carrier frequency data generated by the data selector 6f at the time when the timing signal T generated by the timer 6g at random time intervals is input. The carrier frequency data is selected and switched according to the data select signal N having a certain weight in the frequency.

Finally, the carrier generator 6c creates a carrier wave signal fc based on the carrier frequency data selected by the carrier frequency selector 6e, and the PWM waveform generator 6d.
To enter. The PWM waveform generation unit 6d compares the carrier wave signal fc described above with the fundamental wave signal f generated by the fundamental wave generation unit 6a based on the frequency command signal fo, generates a PWM control signal, and drives the transistor. PWM via circuit 5
Output to the control inverter circuit 3.

As described above, the PWM according to the fourth embodiment
The waveform generation device is configured to randomly select a carrier frequency from a plurality of preset carrier frequencies at random timing and according to preset weighting of the occurrence frequency. As a result, as shown in FIG. 3, as a harmonic component of the pseudo sine wave output of the PWM control inverter device, control is performed so that a specific carrier frequency is not continuously superimposed for a long time. To do.

As a modified structure of the fourth embodiment, a carrier frequency is randomly selected from a plurality of carrier frequencies set in advance and switched. The carrier frequency is preset at a fixed timing. A configuration for randomly selecting and switching a certain carrier frequency from among a plurality of carrier frequencies, a configuration for randomly selecting and switching a certain carrier frequency from a plurality of preset carrier frequencies at random timing, A configuration in which a certain carrier frequency is randomly selected and switched from among a plurality of preset carrier frequencies according to preset weighting of the occurrence frequency, or a voltage-type PWM control inverter device Output voltage waveform (or output current from current source PWM control inverter device) Calculates the phase angle of the waveform), for each predetermined phase angle, from among a plurality of carrier frequencies are set in advance, it is possible to use a construction for switching to select a carrier frequency randomly.

Embodiment 5 FIG. 7 is a configuration diagram of a PWM control inverter device according to a fifth embodiment of the present invention. The PWM control inverter device shown in the figure includes an output current detection unit 7 for detecting the current output current waveform at the output unit of the PWM control inverter circuit 3.

The PWM waveform generator 6-5 shown in the figure has a fundamental wave generating section 6a, a carrier generating section 6c, and P.
In addition to the WM waveform generator 6d, four types of preset carrier frequency data fc1, fc2, fc3, fc
Storage means 6b storing 4 and carrier frequency selection section 6e (an example of seventh carrier frequency switching means)
And a phase angle calculator 6h that calculates the current phase angle of the output current waveform based on the output current waveform input from the output current detector 7 and generates the timing signal T for each preset angle. Composed. Here, the output current detector 7
And the phase angle calculator 6h constitute the power phase angle detecting means according to the present invention. Further, in this case, the control mode for switching the carrier frequency is based on the closed loop feedback system.

Next, the operation of this embodiment will be described in detail. The four types of carrier frequency data fc1, fc2, fc3, fc4 stored in the storage means 6b are input to the carrier frequency selection unit 6e, respectively. In addition, the carrier frequency selection unit 6e receives the data selection signal N
Then, in the phase angle calculation unit 6h, the output current waveform from the PWM control inverter circuit 3 is emitted every time a predetermined fixed angle advances (for example, every 30 ° of phase angles as shown in FIG. 8). The timing signal T is input.

The carrier frequency selection unit 6e receives the timing signal T and, in accordance with the data selection signal N, the carrier frequency data fc1, fc2, fc3.
A certain carrier frequency data is selected from fc4 and input to the carrier generator 6c. The data select signal N input to the carrier frequency selection unit 6e may be data that changes in a preset order or data that changes randomly.

Finally, the carrier generator 6c creates a carrier wave signal fc based on the carrier frequency data selected by the carrier frequency selector 6e, and the PWM waveform generator 6d.
To enter. The PWM waveform generation unit 6d compares the carrier wave signal fc described above with the fundamental wave signal f generated by the fundamental wave generation unit 6a based on the frequency command signal fo, generates a PWM control signal, and drives the transistor. PWM via circuit 5
Output to the control inverter circuit 3.

As described above, the PWM according to the fifth embodiment
The waveform generator detects the output current from the PWM control inverter circuit 3, calculates the phase angle of the output current, obtains the timing for switching the carrier frequency, and switches the carrier frequency appropriately according to this timing. As shown in FIG. 3, as a harmonic component of the pseudo sine wave output of the PWM control inverter device, a specific carrier frequency is controlled so as not to be continuously superimposed for a long time. .

However, as a modified configuration of the fifth embodiment,
The timing at which the carrier frequency is switched is determined by detecting the phase angle of the output current waveform from the voltage-type PWM control inverter device (or the output voltage waveform from the current-type PWM control inverter device), and a plurality of preset multiples are set. From the carrier frequencies, the carrier frequency is sequentially selected and switched according to a preset order, or the output current waveform from the voltage source PWM control inverter device (or the output voltage waveform from the current source PWM control inverter device). It is also possible to adopt a configuration in which the timing for switching the carrier frequency is determined by detecting the phase angle of), and a certain carrier frequency is randomly selected and switched from among a plurality of preset carrier frequencies. .

Note that, in FIGS. 1 and 4 to 7 showing each of the above-described embodiments, the number of carrier frequency data stored in the storage means 6b is three or four for simplification. It goes without saying that any number of carrier frequency data may be used in the embodiment as long as the number is two or more.

Further, in each of the above embodiments, the present invention is
Although the case where it is mainly applied to the voltage type PWM control inverter device has been described, it is needless to say that the present invention can also be applied to the current type PWM control inverter device having a dual relationship with this voltage type PWM control inverter device.

[0060]

As described above, according to the present invention, P
Since the PWM waveform generation device is configured to appropriately switch the carrier frequency at time intervals shorter than one cycle of the output power from the WM control inverter circuit, the frequency components of the carrier sound are dispersed. Therefore, among the noises generated by the air conditioner, the carrier sound, which is particularly audible depending on the conventional technology, is improved to a timbre that is easy to hear, and the noise of the entire air conditioner can be equivalently reduced. it can.

Further, since it is not necessary to increase the carrier frequency particularly as in the conventional case, it is not necessary to increase the speed of the switching element and the control circuit of the PWM control inverter circuit, and the PWM control inverter device accompanying the noise reduction can be realized. Higher prices can be prevented.

In addition, since it is not necessary to increase the carrier frequency to a high frequency as in the conventional case, it is possible to prevent an increase in leakage current due to noise reduction.

Further, according to the inventions of claims 2 to 6, it is not necessary to add a new circuit configuration to the conventional PWM control inverter device, and the function of the PWM waveform generating device (feedforward control function). Therefore, if the PWM waveform generation function is realized by using a microcomputer, the conventional PWM control inverter device can be diverted and the operation can be easily and inexpensively realized.

According to the seventh aspect of the invention, the carrier frequency is appropriately adjusted at a time interval shorter than one cycle of the output power from the PWM control inverter circuit by the feedback control based on the detected real-time output power waveform. Since the switching is performed, it is possible to properly follow the fluctuation of the output power waveform, and improve the timbre of the carrier sound at all times to make it easy to hear.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a PWM control inverter device showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a relationship between a cycle of output power from the PWM control inverter circuit according to the present invention and a time interval for switching the carrier frequency.

FIG. 3 is a schematic diagram showing a frequency distribution and a sound pressure level of a carrier sound according to the present invention.

FIG. 4 is a configuration diagram of a PWM control inverter device showing a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a PWM control inverter device showing a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a PWM control inverter device showing a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram of a PWM control inverter device showing a fifth embodiment of the present invention.

FIG. 8 is a schematic diagram showing a relationship between an output power waveform from the PWM control inverter circuit according to the present invention and a detection signal issued at every predetermined phase angle of the output power.

FIG. 9 is a configuration diagram of a PWM control inverter device of a conventional example.

FIG. 10 is a schematic diagram showing a frequency distribution and a sound pressure level of a carrier sound according to a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC power supply, 2 converter, 3 PWM control inverter circuit, 4 three-phase induction motor, 6-1 PWM waveform generator, 6-2 PWM waveform generator, 6-3 PWM waveform generator, 6-4 PWM waveform generator, 6-5 P
WM waveform generator, 6a fundamental wave generator, 6b storage means, 6c carrier generator, 6d PWM waveform generator,
6e carrier frequency selector, 6f data selector,
6g timer, 6h phase angle calculator, 6i random number generator,
6j random number generator, 7 output current detector, f fundamental wave signal, fc carrier wave signal, TO cycle, TO ₁ cycle, t ₁ time interval, t ₂ time interval, t ₃ time interval, t ₄ time interval, t ₅ Time interval, t ₆ time interval,
t ₇ hours interval, t _8-hour intervals, t ₉ hours interval.

Claims (7)

[Claims] 1. The power of the compressor or the blower for the condenser or the blower for the evaporator of an air conditioner configured by connecting a compressor, a condenser, a throttle device, an evaporator and the like with a refrigerant pipe. A converter that is connected to each of the induction motors used as a power source and that converts an AC power supply into a DC power supply; With the control inverter circuit,
In the PWM waveform generating device that constitutes a PWM control inverter device and generates a pulse width modulation waveform for controlling the PWM control inverter circuit based on an input carrier wave signal and fundamental wave signal, the carrier wave signal A PWM waveform generation device comprising: first carrier frequency switching means for appropriately switching the carrier frequency according to (1) at a time interval shorter than one cycle of the output power from the PWM control inverter circuit. 2. The first carrier frequency switching means,
Carrier frequency setting means for presetting a plurality of carrier frequencies related to the carrier wave signal, and carrier frequency setting means for selecting and switching the carrier frequency from among the plurality of carrier frequencies of the carrier frequency setting means by open-loop feedforward control. The PWM according to claim 1, comprising a second carrier frequency switching means.
Waveform generator. 3. The second carrier frequency switching means,
From among the plurality of carrier frequencies of the carrier frequency setting means, and a selection order setting means that presets the selection order related to the plurality of carrier frequencies of the carrier frequency setting means,
3. The PWM waveform generation device according to claim 2, further comprising a third carrier frequency switching means for selecting and switching carrier frequencies at appropriate timings according to the selection order of the selection order setting means. 4. The third carrier frequency switching means,
A phase angle calculating means for calculating the phase angle of the waveform relating to the fundamental wave signal, and a plurality of carrier frequencies of the carrier frequency setting means are selected at the timing for each phase angle calculated by the phase angle calculating means. 4. The PWM waveform generating device according to claim 3, further comprising: fourth carrier frequency switching means for selecting and switching the carrier frequency according to the selection order of the order setting means. 5. The second carrier frequency switching means,
Random order setting means for randomly setting a selection order of a plurality of carrier frequencies of the carrier frequency setting means, and a random selection set by the random order setting means from a plurality of carrier frequencies of the carrier frequency setting means. The PWM waveform generation device according to claim 2, further comprising: a fifth carrier frequency switching unit that selects and switches the carrier frequency at an appropriate timing according to the order. 6. The fifth carrier frequency switching means,
Weighting carrier frequency setting means for presetting a plurality of carrier frequencies weighted with respective selection frequencies for each carrier frequency, timing calculating means for randomly calculating the switching timing of the carrier frequencies, and the weighting A carrier frequency is selected and switched from among a plurality of carrier frequencies of the carrier frequency setting means at a random switching timing calculated by the timing calculation means and in accordance with a random selection order set by the random order setting means. 6. The PWM waveform generating device according to claim 5, further comprising: 6 carrier frequency switching means. 7. The first carrier frequency switching means,
Carrier frequency setting means for presetting a plurality of carrier frequencies relating to the carrier wave signal, power phase angle detecting means for detecting a phase angle of output power from the PWM control inverter circuit, and a plurality of carrier frequency setting means. A seventh carrier frequency switching means for appropriately selecting and switching the carrier frequency from the carrier frequencies by closed-loop feedback control based on the phase angle of the output power detected by the power phase angle detecting means. The PWM waveform generation device according to claim 1.