JP7471896B2 - INVERTER CONTROL DEVICE, INVERTER CONTROL METHOD, AND INVERTER CONTROL PROGRAM - Google Patents

Description

This disclosure relates to an inverter control device, an inverter control method, and an inverter control program.

The compressor motor installed in the air conditioner is controlled by an inverter. The inverter is controlled by a PWM signal generated using a carrier wave (PWM control).

Patent document 1 discloses switching the carrier frequency depending on the voltage of the commercial power supply, etc.

Patent No. 4352883

However, when a PWM signal is generated using a carrier wave, the current output from the inverter contains high-frequency ripple components due to the frequency of the carrier wave. This can cause electromagnetic or vibrational sounds (carrier sounds) to be generated in the motor into which the current flows. In particular, the carrier frequency is often on the order of a few kHz, which is known to be easily detectable by humans.

In Patent Document 1, the carrier frequency is switched depending on the commercial power supply voltage, etc., but because a constant carrier frequency is used under certain operating conditions (for example, when the commercial power supply voltage is constant), the carrier sound still cannot be sufficiently suppressed, which may cause discomfort to the user.

In addition, in motors driven by inverters, there are frequencies at which resonance can occur depending on the motor rotation speed, and if the carrier frequency is an integer multiple of that frequency, a humming noise caused by resonance can occur.

The present disclosure has been made in consideration of these circumstances, and aims to provide an inverter control device, an inverter control method, and an inverter control program that can improve audibility.

An inverter control device according to a first aspect of the present disclosure includes a setting unit that sets a carrier period based on the rotation speed of a motor driven by an inverter, a carrier wave generating unit that combines a plurality of waveform elements having different periods to form a waveform corresponding to the carrier period and generates a carrier wave formed by repeating the waveform, and a PWM signal generating unit that uses the carrier wave and a predetermined modulated wave to generate a PWM signal for the inverter by a comparison method , and the carrier wave generating unit generates the carrier wave by combining each of the waveform elements according to a predetermined occurrence probability .

An inverter control method according to a second aspect of the present disclosure includes the steps of: setting a carrier period based on the rotation speed of a motor driven by an inverter; combining a plurality of waveform elements having different periods to construct a waveform corresponding to the carrier period and generating a carrier wave constructed by repeating the waveform; and using the carrier wave and a predetermined modulated wave to generate a PWM signal for the inverter by a comparison method, wherein the carrier wave generating step is performed by a computer, which combines each of the waveform elements according to a predetermined occurrence probability to generate the carrier wave .

An inverter control program according to a third aspect of the present disclosure includes a process for setting a carrier period based on the rotation speed of a motor driven by an inverter, a process for combining a plurality of waveform elements having different periods to construct a waveform corresponding to the carrier period and generating a carrier wave constructed by repeating the waveform, and a process for generating a PWM signal for the inverter by a comparison method using the carrier wave and a predetermined modulated wave, wherein the process for generating the carrier wave combines each of the waveform elements according to a predetermined occurrence probability to generate the carrier wave and is executed by a computer.

This disclosure has the effect of improving hearing.

1 is a diagram showing a schematic configuration of a motor drive device in an air conditioner according to a first embodiment of the present disclosure. 2 is a diagram illustrating an example of a hardware configuration of a motor drive device in the air conditioner according to the first embodiment of the present disclosure. FIG. 1 is a functional block diagram showing functions of an inverter control device according to a first embodiment of the present disclosure. FIG. FIG. 11 is a diagram illustrating an example of a change in the carrier period according to the first embodiment of the present disclosure. 1 is a diagram showing a schematic configuration of a motor drive device in an air conditioner according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a carrier wave according to the first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a carrier wave according to the first embodiment of the present disclosure. 4A to 4C are diagrams illustrating an example of a state of a PWM signal according to the first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a carrier wave according to the first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a carrier wave according to the first embodiment of the present disclosure. FIG. 2 is a diagram showing a flowchart of a PWM signal generation process performed by the inverter control device according to the first embodiment of the present disclosure. 6A to 6C are diagrams illustrating an effect of a PWM signal generation process according to the first embodiment of the present disclosure. FIG. 13 is a diagram showing an example of setting occurrence probabilities according to the second embodiment of the present disclosure. FIG. 11 is a diagram illustrating an example of the configuration of a carrier wave according to a second embodiment of the present disclosure. FIG. 13 is a diagram illustrating an example of the configuration of a carrier wave according to a third embodiment of the present disclosure. FIG. 13 is a diagram illustrating an example of resonance characteristics according to a fourth embodiment of the present disclosure.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of an inverter control device, an inverter control method, and an inverter control program according to the present disclosure will be described with reference to the drawings.

(Configuration of the motor drive device)
Fig. 1 is a diagram showing a schematic configuration of a motor drive device 1 in an air conditioner according to a first embodiment of the present disclosure. Note that, although Fig. 1 illustrates a case in which a compressor motor is driven by an inverter 8, the inverter control device 20 in this embodiment is not limited to the above and can be applied to any device that drives a load by PWM controlling the inverter 8.

Figure 1 shows the schematic configuration of a motor drive device 1 that drives a compressor motor (motor that drives a compressor) 9.

The motor drive device 1 drives the compressor motor based on power supplied from an AC power source 4. Specifically, the motor drive device 1 has a converter and an inverter 8 connected to the AC power source 4. The converter is a device that rectifies the AC voltage supplied from the AC power source 4 and converts it to a DC voltage. For this reason, the converter has, for example, a rectifier circuit 5, an inductance section 6, and a capacitor section 7.

The rectifier circuit 5 is connected in parallel to the AC power supply 4, and rectifies the AC voltage supplied from the AC power supply 4. For example, the rectifier circuit 5 is configured as a bridge rectifier circuit using diodes, and full-wave rectifies the AC voltage supplied from the AC power supply 4. Note that the rectification method may be other rectification methods such as half-wave rectification.

The inductance unit 6 is connected in series to the positive DC circuit on the output side of the rectifier circuit 5. The inductance unit 6 may also be connected in series to the negative DC circuit on the output side of the rectifier circuit 5. The capacitor unit 7 is connected in parallel to the rectifier circuit 5 via the inductance unit 6. Although the voltage output from the rectifier circuit 5 is rectified, it is pulsating (contains high-frequency components). Therefore, by providing the inductance unit 6 and the capacitor unit 7 on the output side of the rectifier circuit 5, the pulsating components are suppressed and smoothed.

In the converter, a DC voltage is generated by the rectifier circuit 5, the inductance section 6, and the capacitor section 7, and output to the inverter 8.

The inverter 8 generates a three-phase AC voltage based on the DC voltage supplied from the converter, and drives the compressor motor (load) 9. The inverter 8 is, for example, a bridge circuit composed of six switching elements, and each switching element is switched based on a PWM signal input from the inverter control device 20 described later. The inverter 8 may be a single-phase type or a multi-phase type depending on the load to be driven.

The inverter control device 20 generates a PWM signal and controls the inverter 8.

(Hardware configuration diagram of inverter control device)
FIG. 2 is a diagram showing an example of a hardware configuration of the inverter control device 20 according to the present embodiment.
2, the inverter control device 20 is a computer system including, for example, a CPU 11, a ROM (Read Only Memory) 12 for storing programs and the like executed by the CPU 11, a RAM (Random Access Memory) 13 that functions as a work area when each program is executed, a hard disk drive (HDD) 14 as a large-capacity storage device, and a communication unit 15 for connecting to a network, etc. These units are connected via a bus 18.

The inverter control device 20 may also include an input unit such as a keyboard or mouse, and a display unit such as a liquid crystal display device for displaying data.

The storage medium for storing the programs executed by the CPU 11 is not limited to the ROM 12. For example, it may be other auxiliary storage devices such as a magnetic disk, a magneto-optical disk, or a semiconductor memory.

A series of processing steps for realizing the various functions described below are recorded in the form of a program on the hard disk drive 14, etc., and the CPU 11 reads this program into the RAM 13, etc., and executes information processing and arithmetic processing to realize the various functions described below. The program may be pre-installed in the ROM 12 or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

(Functional configuration diagram of inverter control device)
Fig. 3 is a functional block diagram showing functions of the inverter control device 20. As shown in Fig. 3, the inverter control device 20 includes an acquisition unit 21, a setting unit 25, a carrier wave generation unit 23, and a PWM signal generation unit 22.

The acquisition unit 21 acquires the current at a predetermined position in the inverter 8. Specifically, the acquisition unit 21 acquires current information detected by the current sensor 24. FIG. 1 illustrates an example in which the one-shunt method is used as the current detection method. That is, in FIG. 1, the current flowing through the inverter 8 (composite current of each phase current) is detected by the current sensor 24 and output to the acquisition unit 21. That is, the acquisition unit 21 acquires the composite current of each phase current. In this embodiment, since the inverter 8 is a multi-phase type, the acquisition unit 21 acquires the composite current of each phase current, but if the inverter 8 is a single-phase type, the acquisition unit 21 detects the current of that phase itself using the current sensor 24.

The acquisition unit 21 calculates the current of each phase (Iu, Iv, Iw) from the detection result of the composite current of each phase current. Specifically, the acquisition unit 21 calculates the current of each phase (Iu, Iv, Iw) based on the acquired composite current and a PWM signal generated by the PWM signal generation unit 22 described later, and outputs the current to the PWM signal generation unit 22. Note that as long as the current of each phase can be calculated from the composite current, it does not have to be based on the PWM signal.

When the three-shunt method is used as the current detection method, the motor drive device 1 is configured as shown in FIG. 5. That is, the current corresponding to each phase at the output position of the inverter 8 is detected by the current sensor 24 and output to the acquisition unit 21. That is, the acquisition unit 21 can acquire each phase current. Therefore, the acquisition unit 21 outputs the acquired phase current to the PWM signal generation unit 22.

The method of acquiring the current is not limited to the one-shunt or three-shunt method described above, as long as it is possible to acquire the current of each phase.

The setting unit 25 sets the carrier period based on the rotation speed of the compressor motor 9 driven by the inverter 8. Specifically, the setting unit 25 sets the carrier period so that the ratio between the period of the fundamental wave component of the current flowing through the compressor motor 9 according to the rotation speed and the carrier period is not within a predetermined numerical range including integers.

The carrier wave (frequency spread carrier wave) is a periodic waveform that repeats a certain waveform at a certain cycle, as described below. For example, as described below, when each of the waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe) is configured three times in succession (Figure 7), one cycle of the carrier wave is (0.317 msec x 3) + (0.25 msec x 3) + (0.2 msec x 3) + (0.159 msec x 3) + (0.125 msec x 3) = 3.153 msec.

On the other hand, if the compressor motor 9 driven by the inverter 8 has a rotation speed of N [rpm] and a number of poles of P [-], then the frequency fe of the fundamental wave component of the current flowing through the compressor motor 9 is fe = (N x P) / 120. Note that the period Te is the reciprocal of the frequency fe, so Te = 120 / (N x P). For example, if the rotation speed is 1600 [rpm] and the number of poles is 6, then the period Te = 120 / (1600 x 6) = 12.5 msec.

In other words, when the compressor motor 9 is in an operating state with a period Te = 12.5 msec, if the carrier period is 3.153 msec, the ratio of the period of the fundamental wave component of the current flowing through the compressor motor 9 to the carrier period is approximately an integer multiple (12.5 msec / 3.153 msec ≒ 4). In this way, when the ratio of the period of the fundamental wave component of the current flowing through the compressor motor 9 to the carrier period is approximately an integer multiple, a humming noise may occur due to resonance operation.

The ratio of the period of the fundamental wave component of the current flowing through the compressor motor 9 to the carrier period is the ratio of the larger of the period of the fundamental wave component of the current flowing through the compressor motor 9 and the carrier period to the smaller of the two. In other words, the ratio of the period of the fundamental wave component of the current flowing through the compressor motor 9 to the carrier period may be 1:n (n is an integer) or n:1 (n is an integer). In addition, since the frequency is the reciprocal of the period, the same applies when considered as a frequency.

When the ratio between the period of the fundamental wave component of the current flowing through the compressor motor 9 and the carrier period is close to an integer, there is a possibility that a beat noise will occur due to resonance operation. Therefore, the setting unit 25 sets the carrier period, which is the period of the carrier wave generated by the carrier wave generating unit 23 described later, so that a beat noise will not occur.

To set the carrier period, the setting unit 25 acquires the rotation speed of the compressor motor 9. The number of poles is preset according to the specifications of the configured compressor motor 9. The setting unit 25 then calculates the period of the fundamental wave component of the current flowing through the compressor motor 9 using a predetermined formula (Te = 120/(N x P)).

Then, the setting unit 25 sets the carrier period so that the ratio between the period of the current fundamental wave component flowing through the compressor motor 9 according to the rotation speed and the carrier period is not within a predetermined numerical range including integers. That is, the carrier period is set so that the ratio between the period of the current fundamental wave component and the carrier period is not an integer multiple (a multiple of a value close to an integer). The predetermined numerical range includes integers and is a numerical range set by adding a predetermined margin to the integers. That is, the numerical range is set for each integer and is a range indicating the vicinity of each integer. For example, the predetermined margin is set to 0.3. In this case, the numerical range is set to a range obtained by adding or subtracting 0.3 from the integers. Specifically, if the integers are 1, 2, 3, 4, 5, etc., the numerical range is set to a range of 0.7 to 1.3, a range of 1.7 to 2.3, a range of 2.7 to 3.3, a range of 3.7 to 4.3, a range of 4.7 to 5.3, etc. In other words, the carrier period is set so that the decimal part of the ratio is around 0.5.

The margin in the numerical range can be set appropriately as long as it is a value smaller than 0.5, and may be set to 0.1 or the like depending on the resonance characteristics. Furthermore, the numerical range for integers is not limited to a method of adding or subtracting a predetermined margin, and may be set to include integers.

The setting unit sets a carrier period that does not fall within a numerical range for the period of the calculated fundamental wave component of the current. For example, carrier periods corresponding to a plurality of waveform patterns that combine each waveform element are prepared, and a carrier period that does not fall within a numerical range for the period of the fundamental wave component of the current is set from among the plurality of carrier periods. The setting unit may also set a range of carrier periods (carrier period range) that does not fall within a numerical range for the period of the fundamental wave component of the current.

The method for setting the carrier period is not limited to the above, as long as the carrier period is set so that it is not within the numerical range for the period of the fundamental wave component of the current.

Figure 4 shows an example of changing the carrier period. In Figure 4, the vertical axis represents the frequency and ratio, and the horizontal axis represents the rotation speed of the compressor motor 9. In Figure 4, the carrier period is shown as the carrier frequency (the reciprocal of the carrier period) fh. Also, the period of the current fundamental wave component is shown as the frequency fi. Also, in Figure 4, integers are exemplified as N1 and N2 for the ratio. As shown in Figure 4, since the number of poles is constant due to the specifications of the compressor motor 9, the frequency fi of the current fundamental wave component changes depending on the rotation speed. When the frequency fi of the current fundamental wave component changes in this way, when the carrier frequency fh is constant, the ratio (in this case, the ratio of the carrier frequency to the frequency of the current fundamental wave component) R decreases and approaches an integer (N1 in Figure 4). Then, when the ratio R reaches a predetermined numerical range, there is a possibility that a humming sound will occur, so the carrier frequency (carrier period) fh is changed. Since the carrier period is set appropriately in this way, the ratio R can be outside a predetermined numerical range (i.e., the area between a numerical range corresponding to a certain integer and a numerical range corresponding to an integer that is one value larger). This helps to suppress the occurrence of humming noises.

The carrier wave generating unit 23 combines multiple waveform elements with different periods to form a waveform corresponding to the carrier period, and generates a carrier wave (frequency spread carrier wave) formed by repeating the waveform. That is, the carrier wave generating unit 23 combines each waveform element with a different period to form a waveform whose length (period) is the set carrier period, and repeats the waveform as a waveform for one period to generate a carrier wave that is a periodic waveform. That is, the carrier wave is a waveform in which the combined waveform of each waveform element is repeated in the carrier period. Note that it is preferable that the length of the waveform formed by combining each waveform element matches the carrier period, but it is also possible to set the value close to the carrier period as long as the ratio is within a predetermined numerical range including integers. The carrier wave is a signal that is compared with a modulating wave, which will be described later, when generating a PWM signal. In this embodiment, a case where a triangular wave is used as the carrier wave will be described, but a carrier wave of another waveform, such as a sawtooth wave, may also be used.

The multiple waveform elements with different periods are waveforms for one period in multiple types of periodic waveforms selected in advance. That is, the waveform elements are provided corresponding to multiple periods (frequencies). For example, when the periodic waveform is a triangular wave, a triangular waveform is repeated at a constant period, and the triangular waveform (one period) becomes a waveform element corresponding to the period (frequency). In this embodiment, the carrier wave generating unit 23 is set with waveform elements of five types of frequencies (carrier frequencies) corresponding to 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe). Note that carrier sound (electromagnetic noise generated due to the frequency of the carrier wave) is generated due to the frequency of the carrier wave. For this reason, the period of the waveform elements that constitute the carrier wave may be selected based on the resonance characteristics of a structure (e.g., a compressor or a compressor motor 9) provided on the output side of the inverter 8.

The carrier wave generating unit 23 generates a carrier wave by combining waveform elements corresponding to multiple types of cycles. In other words, the carrier wave is no longer a waveform in which a fixed waveform shape is repeated at a fixed cycle, so that it is possible to suppress the carrier sound from becoming louder at a certain frequency.

In order to avoid generating a large carrier sound at a specific frequency, it is preferable that the carrier wave is a combination of waveform elements corresponding to as many periods as possible in a dispersed manner. In other words, it is preferable that adjacent waveform elements have different periods. However, even when multiple consecutive waveform elements of the same period are configured, the frequency dispersion of the carrier sound can be achieved by setting the number of consecutive elements to a small number.

The number of consecutive waveform elements with equal periods is affected, for example, by current value acquisition. In this embodiment, current acquisition is described as an example, but any factor that affects the number of consecutive waveform elements with equal periods is not limited to current acquisition. Specifically, current acquisition is a one-shunt method or a three-shunt method. The configuration shown in FIG. 1 is a one-shunt method. And the method shown in FIG. 5 is a three-shunt method. That is, the three-shunt method is a method that can directly acquire each phase current, and the one-shunt method is a method that acquires a composite current of each phase current.

6 and 7 are examples of the configuration of the carrier wave when the current detection method corresponds to the one-shunt method (FIG. 1). In the one-shunt method, since the composite current of each phase current is detected, it may take more time to detect than the three-shunt method. Specifically, in the one-shunt method, the timing to read the current is first determined (first period), the current is read (second period), and then, for example, control (PWM control) is performed based on the read current (third period). FIG. 8 is a diagram illustrating the change state of the PWM signal of each phase. In FIG. 8, the vertical axis represents the value (voltage value) of each signal, and the horizontal axis represents time. As shown in FIG. 8, the PWM signal of each phase changes during one period of the carrier wave, and the current that can be obtained by the one-shunt method differs depending on the signal state. FIG. 8 illustrates a case (mode) in which the u-phase current (Iu) and the w-phase current (-Iw) appear during one period, and the mode differs depending on the relationship between the carrier wave and the modulation wave, so it changes during each period (FIG. 8 is an example of a mode). That is, Iu can be obtained from the current sensor 24 at timings A and D, and -Iw can be obtained from the current sensor 24 at timings B and C. Therefore, in the one-shunt method, the mode in the next period (at what timing the current of which phase can be detected) is first determined (first period), and the current is detected at the determined timing in the next period (second period). Then, in the next period, control is performed based on the obtained current (third period). Then, in the next period, the processing of the first period is performed again. In this way, in the one-shunt method, the first period, the second period, and the third period (three periods) are required to perform everything from current acquisition to control. Therefore, when generating a carrier wave in the one-shunt method, it is possible to secure the first period, the second period, and the third period (three periods) and perform processing by configuring waveform elements of the same period three times in succession. In addition, since the same period is used for three periods, the complexity of control can be suppressed.

Figure 6 shows an example of a carrier wave constructed using waveform elements of 3.15 kHz (fa) and 4 kHz (fb). Three waveform elements of 3.15 kHz (fa) and 4 kHz (fb) are consecutively constructed. In Figure 6, the carrier period of the carrier wave is T1. That is, a waveform is constructed by combining waveform elements of 3.15 kHz (fa) and 4 kHz (fb) corresponding to the carrier period T1, and the carrier wave is constructed by repeating this waveform.

Figure 7 shows an example of a carrier wave constructed using waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe). Three consecutive waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe) are constructed. In Figure 7, the carrier period of the carrier wave is T2. That is, the waveform is constructed by combining waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe) corresponding to the carrier period T2, and the carrier wave is constructed by repeating this waveform.

When the one-shunt method is applied, the third period as described above may be unnecessary if only the current is acquired and no control that affects each phase current based on the current is performed, or if control can be performed within the second period. That is, to ensure the first and second periods for the carrier wave, waveform elements of equal periods may be configured twice in succession. Even when the one-shunt method is applied, if it is not necessary to configure waveform elements of equal periods in succession, the waveform elements may be combined as shown in Figures 9 and 10.

Figures 9 and 10 are examples of carrier wave configurations when the current detection method corresponds to the three-shunt method. In the three-shunt method, each phase current can be directly acquired. Therefore, it is possible to configure waveform elements with different periods adjacent to each other without consecutive waveform elements with the same period. Figure 9 is an example of a carrier wave configured using waveform elements of 3.15 kHz (fa) and 4 kHz (fb). Since adjacent waveform elements can have different periods, the waveform elements of 3.15 kHz (fa) and 4 kHz (fb) are configured adjacent to each other. In Figure 9, the carrier period of the carrier wave is T3. In other words, the waveform is configured by combining waveform elements of 3.15 kHz (fa) and 4 kHz (fb) corresponding to the carrier period T3, and the carrier wave is configured by repeating the waveform.

Figure 10 shows an example of a carrier wave formed using waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe). Since adjacent waveform elements can have different periods, the waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe) are adjacent to each other. In Figure 10, the carrier period of the carrier wave is T4. That is, the waveform is formed by combining waveform elements of 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe) corresponding to the carrier period T4, and the carrier wave is formed by repeating the waveform. Note that even in the case of the three-shunt method, waveform elements of the same period may be consecutive.

The PWM signal generating unit 22 generates a PWM signal for the inverter 8 by a comparison method using a carrier wave and a predetermined modulating wave. The carrier wave is a carrier wave generated by the carrier wave generating unit 23. The modulating wave is a signal to be compared with the carrier wave, and in this embodiment, it is a three-phase voltage modulating wave (reference signal) to generate a PWM signal corresponding to three phases. In other words, one carrier wave is compared with three modulating waves (modulating waves corresponding to each of the three phases) to generate a PWM signal corresponding to each phase. The inverter 8 is driven by the generated PWM signal, which outputs a three-phase voltage signal and drives the compressor motor 9.

Specifically, the PWM signal generating unit 22 includes a command calculation unit 31, a modulated wave generating unit 32, and a comparison unit 33.

The command calculation unit 31 calculates a voltage command based on the phase currents output from the acquisition unit 21. Specifically, the command calculation unit 31 generates three-phase voltage commands, which are voltage commands corresponding to each phase, from the phase currents input from the acquisition unit 21, and outputs the three-phase voltage commands to the modulated wave generation unit 32.

The modulated wave generating unit 32 generates a modulated wave based on the three-phase voltage command. Specifically, the modulated wave generating unit 32 generates a three-phase modulated wave, which is a modulated wave corresponding to each phase, from the three-phase voltage command input from the command calculation unit 31, and outputs the three-phase modulated wave to the comparison unit 33.

The comparison unit 33 compares the carrier wave generated by the carrier wave generation unit 23 with the modulated waves corresponding to each phase generated by the modulated wave generation unit 32, and generates a three-phase PWM signal. Specifically, the comparison unit 33 generates a PWM signal by a PWM signal generation method using a comparison method (triangular wave comparison method). For example, the PWM signal corresponding to the u phase is generated with the PWM signal corresponding to the u phase in the ON state (High) while the carrier wave has a value equal to or greater than the modulated wave corresponding to the u phase. While the carrier wave has a value less than the modulated wave corresponding to the u phase, the PWM signal corresponding to the u phase is generated with the PWM signal corresponding to the u phase in the OFF state (Low). PWM signals corresponding to the other phases are generated in the same manner.

The PWM signal is generated as described above and input to the switching elements of each phase in the inverter 8. Each switching element of the inverter 8 is controlled by the PWM signal, and a three-phase voltage is output to drive the compressor motor 9.

(Processing flow by inverter control device)
Next, an example of the PWM signal generation process by the above-mentioned inverter control device 20 will be described with reference to Fig. 11. Fig. 11 is a flowchart showing an example of the procedure of the PWM signal generation process according to this embodiment. The flow shown in Fig. 11 is repeatedly executed at a predetermined control period, for example, when the air conditioner is operating.

First, the current at a predetermined position in the inverter 8 is acquired (S101). Note that the acquisition position for current acquisition differs depending on the acquisition method, such as the one-shunt method or the three-shunt method.

Next, the current of each phase is calculated (S102). S102 can be omitted in the case of the three-shunt system.

Next, a voltage command is calculated based on each phase current, and a modulated wave is generated based on the voltage command (S103).

Next, the rotation speed of the compressor motor 9 is obtained and the carrier period is set (S104).

Next, the carrier wave output from the carrier wave generating unit 23 is compared with the modulated wave to generate a three-phase PWM signal, which is output to the inverter 8 (S105).

By processing in this way, a PWM signal is generated based on a carrier wave that combines waveform elements corresponding to multiple types of cycles, making it possible to improve the audibility.

(Effect of PWM signal generation processing)
Next, the effect of the above-mentioned PWM signal generation process will be described with reference to Fig. 12. In Fig. 12, the vertical axis represents the intensity of the carrier sound, and the horizontal axis represents the frequency. Fig. 12 also shows an example of the carrier sound characteristic in a reference example (L1 in Fig. 12) and the carrier sound characteristic in this embodiment (L2 in Fig. 12). The reference example is a case where a PWM signal is generated based on a carrier wave in which the same waveform is repeated at a constant cycle.

As shown in Figure 12, in the reference example (L1 in Figure 12), the carrier wave repeats the same waveform at a fixed cycle, so the carrier sound stands out at frequency f1 corresponding to the cycle. In other words, the carrier sound at a specific frequency f1 is loud, which may reduce the audibility.

On the other hand, in this embodiment (L2 in FIG. 12), a carrier wave that combines waveform elements corresponding to multiple types of cycles is used, so the intensity characteristics of the carrier sound can be spread in the frequency domain. Specifically, as shown in FIG. 12, the convex points where the carrier sound becomes loud can be distributed to multiple frequencies (f2, f3, f4, f5). This makes it possible to prevent carrier sounds of specific frequencies from standing out, improving the audibility.

As described above, according to the inverter control device, inverter control method, and inverter control program of this embodiment, the carrier wave for generating a PWM signal is composed of a combination of multiple waveform elements with different periods, so that the carrier sound, which is electromagnetic noise generated due to the frequency of the carrier wave, can be frequency-spread. In other words, it is possible to suppress the generation of a loud carrier sound at a specific frequency. This makes it possible to improve the audibility. In addition, the motor driven by the inverter 8 may resonate depending on the rotation speed depending on the carrier period of the carrier wave, but since the carrier period is set based on the rotation speed of the motor, the generation of a humming sound due to the resonant operation can be suppressed.

Second Embodiment
Next, an inverter control device, an inverter control method, and an inverter control program according to a second embodiment of the present disclosure will be described.
In this embodiment, the carrier wave is generated in consideration of the generation time of each waveform element. Hereinafter, the inverter control device, the inverter control method, and the inverter control program according to this embodiment will be described, focusing mainly on the differences from the first embodiment.

In this embodiment, the carrier wave generating unit 23 generates a carrier wave configured to equalize the generation time of each waveform element. For example, when the waveform elements are provided corresponding to 3.15 kHz (fa), 4 kHz (fb), 5 kHz (fc), 6.3 kHz (fd), and 8 kHz (fe), the time for one cycle of each waveform element is 0.317 msec, 0.25 msec, 0.2 msec, 0.159 msec, and 0.125 msec, respectively. In this way, since the cycle becomes longer as the frequency decreases, the ratio of the generation time of each waveform element is 30.2%, 23.8%, 19.0%, 15.1%, and 11.9%, respectively. In other words, when the number of times of each waveform element is used equally, the intensity of the carrier sound caused by the waveform element corresponding to the low frequency may be relatively large compared to the carrier sound caused by the other waveform elements. Therefore, by configuring the generation of the carrier wave so that the generation time of each waveform element is equalized, it is possible to further improve the frequency dispersion effect.

For this reason, the carrier wave generating unit 23 generates a carrier wave by combining each waveform element using an occurrence probability set based on the frequency corresponding to each waveform element. The frequency corresponding to each waveform element is the reciprocal of the period corresponding to each waveform element. In other words, the carrier wave generating unit 23 combines multiple waveform elements with different periods based on the occurrence probability to form a waveform corresponding to the carrier period, and generates a carrier wave composed of a repetition of the waveform. That is, the waveform elements included in one period of the waveform of the carrier wave are combined based on the occurrence probability. In other words, the occurrence time of each waveform element is equalized in one period of the waveform, and the occurrence time of each waveform element is also equalized in the carrier wave as a whole.

Specifically, in the carrier wave generating unit 23, the occurrence probability is set for each waveform element so that there is a positive correlation between the frequency corresponding to each waveform element and the probability. That is, the higher the frequency of the waveform element, the higher the occurrence probability is set. When setting the occurrence probability to have a positive correlation, for example, the probability may be set proportional to the frequency, the probability may be set proportional to the square root of the frequency, or the probability may be set proportional to the square of the frequency. That is, there are no limitations on the method of setting the occurrence probability as long as it is set so that the probability increases with an increase in frequency.

Figure 13 shows an example of setting the occurrence probability so that there is a positive correlation between frequency and probability. Figure 13 shows a case where the probability is set proportional to the frequency (S1), a case where the probability is set proportional to the square root of the frequency (S2), and a case where the probability is set proportional to the square of the frequency (S3). In this way, by setting the occurrence probability so that the probability increases with increasing frequency, the occurrence time of each waveform element is equalized.

For example, the probability of occurrence of 3.15 kHz (fa) is set to 10% (occurrence ratio 2), the probability of occurrence of 4 kHz (fb) is set to 15% (occurrence ratio 3), the probability of occurrence of 5 kHz (fc) is set to 20% (occurrence ratio 4), the probability of occurrence of 6.3 kHz (fd) is set to 25% (occurrence ratio 5), and the probability of occurrence of 8 kHz (fe) is set to 30% (occurrence ratio 6). Figure 14 shows an example of the configuration of a carrier wave when the occurrence probabilities are set as above. Note that Figure 14 is an example of the configuration of one cycle of the waveform of a carrier wave. By configuring the carrier wave based on the occurrence probability, the occurrence time of each waveform element is equalized as shown in Figure 14. This improves the frequency dispersion effect.

In this way, the carrier wave generating unit 23 generates a carrier wave by combining each waveform element based on the set occurrence probability. By generating a carrier wave based on the occurrence probability, the occurrence time of each waveform element is equalized, improving the frequency dispersion effect.

As described above, according to the inverter control device, inverter control method, and inverter control program of this embodiment, the carrier wave is configured to equalize the occurrence time of each waveform element, so that the occurrence frequency of waveform elements of a specific cycle (frequency) increases, and the carrier sound of that frequency can be prevented from becoming prominent. In other words, the volume of the carrier sound corresponding to the frequency of each waveform element can be equalized, and the frequency spreading effect can be enhanced. This makes it possible to improve the audibility.

In addition, by combining each waveform element using an occurrence probability set based on the frequency corresponding to each waveform element, the frequency of occurrence of a waveform element with a specific period (frequency) increases, preventing the carrier sound of that frequency from becoming prominent. In other words, the volume of the carrier sound corresponding to the frequency of each waveform element can be equalized, enhancing the frequency spreading effect.

Third Embodiment
Next, an inverter control device, an inverter control method, and an inverter control program according to a third embodiment of the present disclosure will be described.
In the first embodiment described above, the carrier wave is formed by combining waveform elements for one cycle, but in this embodiment, the carrier wave is formed taking into consideration the rising and falling edges. The following describes the inverter control device, inverter control method, and inverter control program according to this embodiment, focusing mainly on the differences from the first embodiment. Note that this embodiment can also be combined with the second embodiment.

In this embodiment, the carrier wave generating unit 23 generates a carrier wave using a modified waveform element composed of the rising and falling edges of waveform elements with different periods. That is, the carrier wave generating unit 23 generates a carrier wave by using a modified waveform element composed of the rising edge of a waveform element of one period and the falling edge of a waveform element of another period, in addition to each of the waveform elements described above. In other words, the carrier wave is composed by combining each waveform element with the generated modified waveform element. For example, the modified waveform element is composed of the rising edge of a waveform element of 3.15 kHz (fa) and the falling edge of a waveform element of 8 kHz (fe).

Figure 15 shows an example of the configuration of a carrier wave in this embodiment. As shown in Figure 15, the carrier wave is composed of a waveform element having a constant period and a modified waveform element. Specifically, W1 and W2 are modified waveform elements, and W3, W4, and W5 are waveform elements. W3 corresponds to 5 kHz (fc), W4 corresponds to 6.3 kHz (fd), and W5 corresponds to 8 kHz (fe). W1 has a rising edge corresponding to the rising edge of the waveform element of 3.15 kHz (fa), and a falling edge corresponding to the falling edge of the waveform element of 8 kHz (fe). W2 has a rising edge corresponding to the rising edge of the waveform element of 4 kHz (fb), and a falling edge corresponding to the falling edge of the waveform element of 8 kHz (fe). The period of the carrier wave is T5.

In this way, by associating the rising and falling edges with waveform elements of different periods, the frequency dispersion effect can be enhanced. In addition, by configuring the rising and falling edges of the modified waveform elements based on the occurrence probability described in the second embodiment, it is also possible to equalize the occurrence time of each waveform element (frequency). In addition, the rising and falling edges of the modified waveform elements may be configured based on the occurrence probability described in the fourth embodiment described below.

As described above, the inverter control device, inverter control method, and inverter control program according to this embodiment generate a carrier wave using modified waveform elements composed of rising and falling edges of waveform elements with different periods, thereby enhancing the frequency spreading effect and improving the audibility.

Fourth Embodiment
Next, an inverter control device, an inverter control method, and an inverter control program according to a fourth embodiment of the present disclosure will be described.
In this embodiment, the occurrence probability is set in consideration of the resonance characteristics of the structure. The following describes the inverter control device, the inverter control method, and the inverter control program according to this embodiment, focusing mainly on the differences from the first embodiment. Note that this embodiment can also be combined with the second and/or third embodiments.

When a carrier sound occurs at a specific frequency and this frequency coincides with or is close to the resonance point (natural frequency) of a structure such as a compressor that is provided on the output side of the inverter 8, the carrier sound may stand out. For example, if the natural frequency of the compressor is 4 kHz (fb), the carrier sound of 4 kHz (fb) may stand out even if the number of occurrences of the waveform element corresponding to 4 kHz (fb) is small.

The carrier wave generating unit 23 in this embodiment generates a carrier wave in which each waveform element is combined according to the occurrence probability set based on the resonance characteristics of a structure (e.g., a compressor) provided on the output side of the inverter 8. In other words, based on the resonance characteristics of the structure, the occurrence probability is set low for waveform elements that correspond to or are close to the resonance frequency (a specified bandwidth including the resonance frequency).

Figure 16 shows an example of resonance characteristics (sweep characteristics). In Figure 16, the vertical axis represents the intensity (sound pressure level) of the carrier sound, and the horizontal axis represents the frequency, showing the resonance characteristics (C1 in Figure 16). Figure 16 also shows the probability on the vertical axis, showing the occurrence probability (P1 in Figure 16) corresponding to the resonance characteristics.

In the example of Figure 16, fc1, fc2, fc3, and fc4 are resonant frequencies, and the intensity of the carrier sound is high. If the occurrence probability is set in accordance with such resonance characteristics, it becomes P1 in Figure 16. In other words, the occurrence probability is set so that the occurrence probability of frequencies whose intensity increases according to the resonance characteristics is low.

In this way, by setting the occurrence probability based on the resonance characteristics and combining each waveform element based on the set occurrence probability to generate a carrier signal, it is possible to more effectively prevent carrier sounds of specific frequencies from standing out. In other words, it is possible to perform frequency spreading more efficiently by taking into account the resonance characteristics, thereby further improving the listening experience.

As described above, the inverter control device, inverter control method, and inverter control program according to this embodiment can set the probability of occurrence of frequencies at which resonance is likely to occur low due to the resonance characteristics, and can suppress carrier sounds of specific frequencies from becoming prominent due to resonance. It is also possible to enhance the frequency spreading effect and improve the audibility.

The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the invention. It is also possible to combine the various embodiments. In other words, the above-described first, second, third, and fourth embodiments can be combined with each other.

For example, in each embodiment, a case has been described in which the compressor motor 9 is driven using the inverter 8, but the target driven by the inverter 8 is not limited to the above. Accordingly, it becomes possible to appropriately set the waveform elements and occurrence probability in consideration of the resonance characteristics of the target structure driven by the inverter 8.

The inverter control device, the inverter control method, and the inverter control program according to the above-described respective embodiments can be understood, for example, as follows.
The inverter control device (20) according to the present disclosure includes a setting unit (25) that sets a carrier period based on the rotation speed of a motor driven by an inverter (8), a carrier wave generating unit (23) that combines a plurality of waveform elements with different periods to configure a waveform corresponding to the carrier period and generates a carrier wave configured by repeating the waveform, and a PWM signal generating unit (22) that uses the carrier wave and a predetermined modulated wave to generate a PWM signal for the inverter (8) by a comparison method. The specific waveform shape of the waveform elements is, for example, a triangular wave, but may be a sawtooth wave or the like and is not limited to a triangular wave.

According to the inverter control device (20) of the present disclosure, the carrier wave for generating the PWM signal is composed of a combination of multiple waveform elements with different periods, so that the carrier sound, which is electromagnetic noise generated due to the frequency of the carrier wave, can be frequency spread. In other words, it is possible to suppress the generation of a loud carrier sound at a specific frequency. This makes it possible to improve the audibility. In addition, the motor driven by the inverter (8) may resonate depending on the rotation speed depending on the carrier period of the carrier wave, but since the carrier period is set based on the rotation speed of the motor, the generation of the humming sound due to the resonant operation can be suppressed.

In the inverter control device (20) according to the present disclosure, the setting unit (25) sets the carrier period so that the ratio between the period of the fundamental wave component of the current flowing through the motor according to the rotation speed and the carrier period is not within a predetermined numerical range including integers.

According to the inverter control device (20) of the present disclosure, the carrier period is set so that the ratio of the period of the fundamental wave component of the current flowing through the motor to the carrier period is not within a predetermined numerical range including integers, so that the ratio of the carrier period to the period of the fundamental wave component of the current or the ratio of the period of the fundamental wave component of the current to the carrier period becomes an integer multiple (or a multiple close to an integer), thereby suppressing the generation of a humming noise.

In the inverter control device (20) disclosed herein, the numerical range is an integer plus or minus 0.3.

According to the inverter control device (20) of the present disclosure, by setting the numerical range as a range obtained by adding or subtracting 0.3 from an integer, it becomes possible to set the carrier period more appropriately.

The motor drive device (1) according to the present disclosure includes an inverter (8) that drives a compressor motor (9) and the inverter control device (20) described above.

The inverter control method according to the present disclosure includes a step of setting a carrier period based on the rotation speed of a motor driven by an inverter (8), a step of combining a plurality of waveform elements having different periods to form a waveform corresponding to the carrier period, and a step of generating a carrier wave formed by repeating the waveform, and a step of generating a PWM signal for the inverter (8) by a comparison method using the carrier wave and a predetermined modulation wave.

The inverter control program according to the present disclosure causes a computer to execute the following processes: setting a carrier period based on the rotation speed of a motor driven by an inverter (8); constructing a waveform corresponding to the carrier period by combining multiple waveform elements with different periods, and generating a carrier wave composed of repeated waveforms; and generating a PWM signal for the inverter (8) by a comparison method using the carrier wave and a specified modulation wave.

1: Motor drive device
4: AC power supply 5: Rectifier circuit 6: Inductance section 7: Capacitor section 8: Inverter 9: Compressor motor 11: CPU
12: ROM
13: RAM
15: Communication section 18: Bus 20: Inverter control device 21: Acquisition section 22: PWM signal generation section 23: Carrier wave generation section 24: Current sensor 25: Setting section 31: Command calculation section 32: Modulated wave generation section 33: Comparison section

Claims (9)

a setting unit that sets a carrier period based on the rotation speed of a motor driven by an inverter;
a carrier wave generating unit that combines a plurality of waveform elements having different periods to form a waveform corresponding to the carrier period and generates a carrier wave formed by repeating the waveform;
a PWM signal generating unit that generates a PWM signal for the inverter by a comparison method using the carrier wave and a predetermined modulated wave;
Equipped with
The carrier wave generating unit is an inverter control device that generates the carrier wave by combining each of the waveform elements according to a predetermined occurrence probability . 2. The inverter control device according to claim 1, wherein the carrier wave generating unit uses the occurrence probability, the probability of which is set based on a frequency corresponding to each of the waveform elements, to generate the carrier wave configured to combine each of the waveform elements to equalize the occurrence time of each of the waveform elements. 2. The inverter control device according to claim 1, wherein the carrier wave generating unit generates the carrier wave using a modified waveform element composed of rising and falling edges of the waveform elements having different periods, based on the occurrence probability set based on a frequency corresponding to each of the waveform elements, or based on the occurrence probability set based on a resonance characteristic of a structure provided on the output side of the inverter. 2. The inverter control device according to claim 1, wherein the carrier wave generating unit generates the carrier wave by combining each of the waveform elements in accordance with the occurrence probability set based on the resonance characteristics of a structure provided on the output side of the inverter. 5. The inverter control device according to claim 1, wherein the setting unit sets the carrier period so that a ratio between a period of a fundamental wave component of a current flowing through the motor in accordance with the rotation speed and the carrier period is not within a predetermined numerical range including integers . 6. The inverter control device according to claim 5 , wherein the numerical range is a range obtained by adding or subtracting 0.3 from the integer. an inverter that drives a compressor motor;
An inverter control device according to any one of claims 1 to 6 ,
A motor drive device comprising: setting a carrier period based on the rotation speed of a motor driven by an inverter;
A step of combining a plurality of waveform elements having different periods to form a waveform corresponding to the carrier period, and generating a carrier wave formed by repeating the waveform;
generating a PWM signal for the inverter using the carrier wave and a predetermined modulating wave in a comparison manner;
having
A computer-executed inverter control method, wherein the step of generating the carrier wave generates the carrier wave by combining each of the waveform elements according to a predetermined occurrence probability . A process of setting a carrier period based on the rotation speed of a motor driven by an inverter;
A process of combining a plurality of waveform elements having different periods to form a waveform corresponding to the carrier period, and generating a carrier wave formed by repeating the waveform;
A process of generating a PWM signal for the inverter by a comparison method using the carrier wave and a predetermined modulating wave ,
The process of generating the carrier wave generates the carrier wave by combining each of the waveform elements according to a predetermined occurrence probability.
An inverter control program to be executed by a computer.

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