Compressor control method

Abstract

To propose a compressor control method capable of suppressing vibration of the compressor in a specific operation area.SOLUTION: A compressor control method is for controlling vibration amplitude of a compressor provided with a motor by using the motor. The compressor is a device driven by the motor, and the compressor control method controls the vibration amplitude so that the vibration amplitude is substantially constant in a specific operation area regardless of changes in a load on the motor and in a rotation speed of the motor. On the basis of, for example, data read out from a preset table, the vibration amplitude is controlled so as to be substantially constant regardless of the changes.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This disclosure relates to a compressor control method.

Background Art

[0002] Techniques for suppressing the vibration of a compressor are known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] This disclosure proposes a compressor control method capable of suppressing the vibration of a compressor in a specific operation area.

Means for Solving the Problems

[0005] A compressor control method according to a first aspect is a compressor control method for controlling the vibration amplitude of a compressor provided with a motor by the motor, where the compressor is a device driven by the motor, and in a specific operation area, the vibration amplitude is controlled to be substantially constant regardless of changes in the load received by the motor and the rotational speed of the motor.

[0006] According to the compressor control method according to the first aspect, in a specific operation area, the vibration amplitude is controlled to be substantially constant regardless of changes in the load received by the motor and the rotational speed of the motor, so that the vibration of the compressor can be suppressed.

[0007] A compressor control method according to a second aspect is, in the first aspect, Based on data read from a pre-configured table, the vibration amplitude is controlled to remain approximately constant regardless of the aforementioned changes.

[0008] According to the compressor control method of the second embodiment, the vibration amplitude is controlled to be substantially constant regardless of the changes, based on data read from a preset table, thereby suppressing the vibration of the compressor.

[0009] A compressor control method according to a third embodiment is, in the second embodiment, When the load on the motor decreases to below a first threshold set for each rotational speed of the motor, the vibration amplitude is controlled to a first level. When the load on the motor rises above a second threshold set for each rotational speed of the motor, the vibration amplitude is controlled to a second level. The first threshold is less than or equal to the second threshold. The aforementioned second level is lower than the aforementioned first level.

[0010] The greater the load on the motor, the greater the vibration amplitude of the compressor tends to be. According to the compressor control method of the third embodiment, when the load on the motor rises above the second threshold, the vibration amplitude of the compressor is controlled to a second level lower than the first level, thereby suppressing the increase in the vibration amplitude of the compressor.

[0011] A compressor control method according to the fourth embodiment is, in the third embodiment, The system has a mode for controlling the vibration amplitude between the first level and the second level.

[0012] According to the compressor control method of the fourth embodiment, even if the vibration amplitude of the compressor cannot be controlled to the second level due to some factor, the vibration amplitude of the compressor is controlled between the first level and the second level, so the vibration of the compressor can be suppressed.

[0013] The compressor control method according to the fifth embodiment is, according to any one embodiment of the first to fourth, Based on a variable that increases or decreases according to the vibration amplitude, the vibration amplitude is controlled to be substantially constant regardless of the change.

[0014] According to the compressor control method according to the fifth aspect, since the vibration amplitude is controlled to be substantially constant regardless of the change based on a variable that increases or decreases according to the vibration amplitude, the vibration amplitude of the compressor can be suppressed.

[0015] The compressor control method according to the sixth aspect is, in the fifth aspect, when the load received by the motor drops below a first threshold value set for each rotation speed of the motor, the vibration amplitude is controlled to a first level, when the load received by the motor rises above a second threshold value set for each rotation speed of the motor, the vibration amplitude is controlled to a second level, the first threshold value is not more than the second threshold value, the second level is lower than the first level.

[0016] As the load received by the motor increases, the vibration amplitude of the compressor tends to increase. According to the compressor control method according to the sixth aspect, when the load received by the motor rises above the second threshold value, the vibration amplitude of the compressor is controlled to a second level lower than the first level, so an increase in the vibration amplitude of the compressor can be suppressed.

[0017] The compressor control method according to the seventh aspect is, in the sixth aspect, has a mode of controlling the vibration amplitude between the first level and the second level.

[0018] According to the compressor control method according to the seventh aspect, even if the vibration amplitude of the compressor cannot be controlled to the second level for some reason, the vibration amplitude of the compressor is controlled between the first level and the second level, so the vibration of the compressor can be suppressed.

[0019] The compressor control method according to the eighth aspect is, in any one of the fifth to seventh aspects, The variable is the vibration torque generated by the difference between the load torque received by the motor and the motor torque generated by the motor, the magnitude of the fluctuation of the magnetic pole position of the motor, or the magnitude of the fluctuation of the rotational speed of the motor, The vibration torque, the magnitude of the fluctuation of the magnetic pole position, or the magnitude of the fluctuation of the rotational speed changes according to the rotational speed of the motor.

[0020] According to the compressor control method according to the eighth aspect, the variable is the vibration torque, the magnitude of the fluctuation of the magnetic pole position, or the magnitude of the fluctuation of the rotational speed, and since they change according to the rotational speed of the motor, the vibration of the compressor can be suppressed.

Brief Description of Drawings

[0021] [Figure 1] It is a diagram for explaining control for suppressing vibration of a compressor (vibration suppression control). [Figure 2] It is a diagram illustrating the relationship between the amplitude of the vibration torque and the vibration amplitude of the compressor at each rotational speed of the motor. [Figure 3] It is a diagram illustrating the relationship between the rotational speed of the motor and the amplitude of the vibration torque for controlling the vibration amplitude of the compressor to a substantially constant level. [Figure 4] It is a diagram for explaining the compressor control method in the first embodiment. [Figure 5] It is a diagram for explaining the compressor control method in the second embodiment. [Figure 6] It is a diagram for explaining the compressor control method in the third embodiment. [Figure 7] It is a block diagram illustrating the configuration of the motor control device and its peripheral devices. [Figure 8] It is a block diagram showing a first configuration example of the γc-axis current correction unit in the first embodiment. [Figure 9] It is a block diagram illustrating the configuration of the correction amount calculation unit. [Figure 10] It is a block diagram showing a second configuration example of the γc-axis current correction unit in the first embodiment. [Figure 11] This is a block diagram showing a third configuration example of the γc axis current correction unit in the first embodiment. [Figure 12] This is a block diagram showing a fourth configuration example of the γc axis current correction unit in the first embodiment. [Figure 13] This is a block diagram showing a first configuration example of the γc axis current correction unit in the second embodiment. [Figure 14] This is a block diagram showing a second example of the configuration of the γc axis current correction unit in the second embodiment. [Figure 15] This is a block diagram showing a first configuration example of the γc axis current correction unit in the third embodiment. [Figure 16] This is a block diagram showing a second example of the configuration of the γc axis current correction unit in the third embodiment. [Modes for carrying out the invention]

[0022] The embodiments will be described below.

[0023] Figure 1 illustrates a control system for suppressing compressor vibration (vibration suppression control). A compressor is a device that compresses refrigerant. Compressors are driven by motors and are used, for example, in air conditioners. During the refrigerant compression process, the load on the compressor motor (e.g., load torque) fluctuates significantly, as shown in Figure 1. Excitation torque represents the torque generated by the difference between the torque output by the motor (motor torque) and the load torque on the motor. This excitation torque causes the compressor to vibrate.

[0024] Vibration suppression control varies the controllable motor torque to follow changes in load torque. This reduces the excitation torque, thereby suppressing compressor vibration. However, varying the motor torque to reduce the excitation torque increases the current flowing through the motor, which can increase motor losses and potentially reduce the efficiency of both the compressor and the motor.

[0025] The compressor control method in this embodiment suppresses compressor vibrations within a range where the vibrations do not pose a practical problem, by performing vibration suppression control of the compressor in a specific operating area, and also suppresses a decrease in the efficiency of the compressor and other components.

[0026] Figure 2 illustrates the relationship between the amplitude of the excitation torque and the vibration amplitude of the compressor at various motor speeds (18, 28, 40, 47, 57 rps). rps stands for revolutions per second and represents the number of times the motor rotates per second. -1 It is also written as [this]. Note that the specific numerical values ​​shown in Figure 2, etc., are merely examples, and the technology of this disclosure is not limited to these values.

[0027] Controlling the compressor's vibration amplitude to a constant level (300 μm in the case of Figure 2) is preferable in order to achieve both suppression of compressor vibration and suppression of efficiency degradation. The amplitude of the excitation torque that controls the compressor's vibration amplitude to a nearly constant level varies depending on the motor's rotational speed, as shown in Figure 2.

[0028] Figure 3 illustrates the relationship between motor speed and excitation torque amplitude for controlling the compressor vibration amplitude to a nearly constant level. Based on the relationship shown in Figure 3, vibration suppression control is performed by changing the excitation torque amplitude value to match the amplitude value corresponding to the motor speed, thereby controlling the compressor vibration amplitude to a nearly constant level. For example, a command value for the excitation torque corresponding to the motor speed is derived based on the table representing the approximate straight line (approximation curve) shown in Figure 3, and the motor torque is adjusted according to the manipulated variable corresponding to the derived command value. By performing such vibration suppression control in a specific operating area, the compressor vibration amplitude is controlled to a nearly constant level regardless of changes in the load on the motor and the motor speed, thus achieving both compressor vibration suppression and suppression of efficiency degradation in a specific operating area.

[0029] The specific operating area refers to an area determined by at least one of a predetermined load fluctuation region in which the load on the motor can fluctuate, and a predetermined rotational speed region in which the rotational speed of the motor can fluctuate. The specific operating area may be set appropriately depending on the region in which it is desired to suppress compressor vibration and efficiency degradation.

[0030] Furthermore, the variable that increases or decreases in accordance with the vibration amplitude of the compressor is not limited to the excitation torque; it could also be the magnitude of the fluctuation in the magnetic pole position of the motor, or the magnitude of the fluctuation in the rotational speed of the motor. The magnitude of the fluctuation represents the difference (amount of fluctuation) between the maximum and minimum values. Similar to the case of excitation torque, the magnitude of the fluctuation in the magnetic pole position (or the magnitude of the fluctuation in rotational speed) that controls the vibration amplitude of the compressor to a nearly constant level differs depending on the motor's rotational speed. In other words, the excitation torque on the vertical axis of Figure 3 can be replaced with the magnitude of the fluctuation in the magnetic pole position or the magnitude of the fluctuation in rotational speed.

[0031] Therefore, based on the relationship between the motor speed and the magnitude of the fluctuation in magnetic pole position, the vibration amplitude of the compressor can be controlled to a substantially constant level by changing the magnitude of the fluctuation in magnetic pole position to a value corresponding to the motor speed. Similarly, based on the relationship between the motor speed and the magnitude of the fluctuation in rotational speed, the vibration amplitude of the compressor can be controlled to a substantially constant level by changing the magnitude of the fluctuation in rotational speed to a value corresponding to the motor speed.

[0032] Next, several embodiments will be described in more detail.

[0033] Figure 4 is a diagram illustrating the compressor control method in the first embodiment. In the compressor control method in the first embodiment, the vibration amplitude of the compressor is controlled to a first level regardless of the load on the motor and changes in the motor's rotational speed in a specific operating area. This makes it possible to suppress compressor vibration and efficiency degradation in a specific operating area.

[0034] In the first embodiment, the compressor control method controls the vibration amplitude of the compressor to a first level regardless of changes in the load on the motor and the rotational speed of the motor when the compressor is operating in a first operating area determined by the load on the motor and the rotational speed of the motor. On the other hand, in the first embodiment, the compressor control method prohibits controlling the vibration amplitude of the compressor to a first level when the compressor is operating in a second operating area where the vibration amplitude of the compressor is smaller than that of the first operating area. This makes it possible to suppress vibration deterioration caused by controlling (increasing) the vibration amplitude of the compressor to a first level in the second operating area.

[0035] Figure 5 is a diagram illustrating the compressor control method in the second embodiment. The compressor control method in the second embodiment has a first mode in which, when the load on the motor falls below a first threshold (consisting of thresholds L1a, L2a, and L3a in Figure 5) set for each motor rotation speed, the vibration amplitude of the compressor is controlled to a first level. On the other hand, the compressor control method in the second embodiment has a second mode in which, when the load on the motor rises above a second threshold (consisting of thresholds L1b, L2b, and L3b in Figure 5) set for each motor rotation speed, the vibration amplitude of the compressor is controlled to a second level lower than the first level. The first threshold is set to be below the second threshold. The vibration amplitude of the compressor tends to increase as the load on the motor increases. According to the compressor control method in the second embodiment, when the load on the motor rises above the second threshold, the vibration amplitude of the compressor is controlled to a second level lower than the first level, thus suppressing the increase in the vibration amplitude of the compressor.

[0036] Figure 5 illustrates thresholds L2a and L2b set for the rotational speed range from R1 to R2, thresholds L1a and L1b set for the rotational speed range from R2 to R3, and thresholds L3a and L3b set for the rotational speed range from R3 to R4. The number of thresholds and the relative magnitudes of the multiple thresholds are arbitrary and can be set as appropriate. In Figure 5, threshold L1a is lower than threshold L1b, threshold L2a is lower than threshold L2b, and threshold L3a is lower than threshold L3b. By providing such hysteresis between the first and second thresholds, even if the load on the motor moves up and down near the first or second threshold, it is possible to suppress frequent switching between the first and second levels at which the vibration amplitude is controlled. Note that hysteresis does not need to be provided if the first and second thresholds are set to the same value. A single threshold L2 (L2a=L2b) may be set for the rotational speed range from R1 to R2, a single threshold L1 (L1a=L1b) for the rotational speed range from R2 to R3, and a single threshold L3 (L3a=L3b) for the rotational speed range from R3 to R4.

[0037] Furthermore, according to the compressor control method in the second embodiment, in the operating area where the load on the motor is below the first threshold, the vibration amplitude of the compressor is allowed to be at the first level, which is higher than the second level, thus reducing the degree of vibration suppression. Therefore, in the operating area where the load on the motor is below the first threshold, the efficiency of the compressor and other components can be increased compared to the operating area where the load on the motor is greater than the second threshold, while suppressing the vibration amplitude of the compressor.

[0038] In operating areas where the load on the motor is below a predetermined threshold L (for example, the first threshold), an operating area is set in which the air conditioner exhibits the capacity defined by the Japanese Industrial Standards (JIS). More specifically, it is preferable that at least one of the eight capacities defined in JIS B8616:2015 (rated cooling standard capacity, intermediate cooling standard capacity, intermediate cooling medium temperature capacity, minimum cooling medium temperature capacity, rated heating standard capacity, intermediate heating standard capacity, minimum heating standard capacity, and maximum heating low temperature capacity) is set in the operating area where the load on the motor is below a predetermined threshold L. This makes it possible to increase the efficiency of the compressor, etc., while suppressing the vibration amplitude of the compressor in a specific operating area, thereby increasing the annual performance factor (APF) defined in JIS B8616:2015.

[0039] Figure 6 is a diagram illustrating the compressor control method in the third embodiment. The compressor control method in the third embodiment has a third mode that controls the vibration amplitude of the compressor between a first level and a second level. According to the compressor control method in the third embodiment, even if the vibration amplitude of the compressor cannot be controlled to the second level due to some factor (for example, a hardware constraint of the inverter), the vibration amplitude of the compressor is controlled between the first level and the second level, so the vibration of the compressor can be suppressed.

[0040] Next, we will describe examples of the configuration of the electric motor control device in each embodiment of the compressor control method.

[0041] Figure 7 is a block diagram illustrating the configuration of an electric motor control device and its peripheral equipment. The electric motor control device 1 shown in Figure 7 controls a synchronous motor 3, which is an example of a motor that drives a compressor, a device that compresses refrigerant.

[0042] The synchronous motor 3 is a three-phase rotary motor and comprises an armature and a rotor, which is the field (neither of which is shown). As is common technical knowledge, the armature has armature windings, and the rotor rotates relative to the armature. The field comprises, for example, magnets that generate field flux (field magnets: not shown), and a recessed magnet type is used.

[0043] The voltage supply source 2 includes, for example, a voltage-controlled inverter and its control unit, and applies a three-phase voltage to the synchronous motor 3 based on a three-phase voltage command value [V*] (the symbol [] indicates a vector). As a result, a three-phase current [I] flows from the voltage supply source 2 to the synchronous motor 3.

[0044] The motor control device 1 controls the primary magnetic flux and rotational speed (rotational angular velocity in the following example) of the synchronous motor 3. The primary magnetic flux is the sum of the field magnetic flux Λ0 generated by the field magnets and the armature reaction flux generated by the armature current (which is also the three-phase current [I]) flowing through the synchronous motor 3 (more specifically, through the armature). The primary magnetic flux command Λδ* is the command value of the actual magnitude Λδ of the primary magnetic flux.

[0045] The motor control device 1 controls the synchronous motor 3 by controlling the primary magnetic flux of the synchronous motor 3 to match the primary magnetic flux command Λδ* on the δc axis, which is the control axis of the primary magnetic flux. The δc axis leads the d axis, which indicates the phase of the field magnetic flux Λ0 in the rotating coordinate system, by a predetermined phase difference. The actual primary magnetic flux has a δc axis component λδc on the δc axis and a γc axis component λγc on the γc axis. The γc axis leads the δc axis by an electrical angle of 90 degrees. Hereafter, the terms primary magnetic flux λδc and λγc may be used simply.

[0046] Typically, the commanded value of the primary magnetic flux has a γc-axis component of zero and a δc-axis component set to the primary magnetic flux command Λδ* as described above. In other words, the motor control device 1 performs control to make the γc-axis component λγc of the actual primary magnetic flux zero to obtain a predetermined phase difference. Such control is commonly called primary magnetic flux control and is well known. Typically, the controllable quantities used in primary magnetic flux control are primary magnetic flux and rotational speed.

[0047] In this embodiment, the primary magnetic flux may be an estimated value or an observed value. Techniques for estimating the primary magnetic flux are also known.

[0048] The motor control device 1 comprises a first coordinate transformation unit 101, a magnetic flux control unit 102, a second coordinate transformation unit 104, and a speed command correction device 12. The functions of each of these parts of the motor control device 1 are realized by the operation of a processor (e.g., a CPU (Central Processing Unit)) based on a program stored in memory in a readable format.

[0049] The first coordinate transformation unit 101 performs a three-phase / two-phase conversion based on the electrical angle θe of the synchronous motor 3, which is determined as described later. Specifically, it converts the three-phase current [I] into the δc-axis current iδc and γc-axis current iγc in the δc-γc rotating coordinate system used for primary magnetic flux control. In this case, the sum of the three phases of the three-phase current is zero, so if two phases are obtained, the other phase can be estimated from those two phases. "3(2)" in Figure 7 indicates that the detected current may be either three-phase or two-phase. The δc-axis current iδc and γc-axis current iγc can be said to be the δc-axis component and γc-axis component of the current flowing through the synchronous motor 3, respectively.

[0050] The second coordinate transformation unit 104 performs two-phase / three-phase conversion based on the electrical angle θe. Specifically, it converts the δc-axis voltage command value vδ* and the γc-axis voltage command value vγ* in the δc-γc rotating coordinate system to three-phase voltage command value [V*].

[0051] Alternatively, instead of the three-phase voltage command value [V*], the δc-axis voltage command value vδ* and the γc-axis voltage command value vγ* may be converted to voltage command values ​​in other coordinate systems, such as the dq rotating coordinate system. Other coordinate systems that can be used include the αβ fixed coordinate system, the uvw fixed coordinate system, and the polar coordinate system.

[0052] The magnetic flux control unit 102 obtains a rotation speed command ωm* (for mechanical angles) corresponding to the rotation speed command ωeo* (for electrical angles). Since this function can be easily implemented using publicly known technology, the details are omitted.

[0053] The magnetic flux control unit 102 is equipped with, for example, an integration function. This integration function integrates the rotational speed command ωe* to obtain the electrical angle θe. From the obtained electrical angle θe and the load angle φ of the primary magnetic flux with respect to the d-axis, the rotational angle θm as the mechanical angle is obtained by equation (1). However, the number of pole pairs P of the synchronous motor 3 is introduced.

[0054] θm = (θe - φ) / P ... (1)

[0055] The load angle φ may be an estimated or observed value. Techniques for estimating the load angle φ are publicly known. Furthermore, other publicly known techniques besides equation (1) can be used to determine the rotation angle θm.

[0056] The magnetic flux control unit 102 generates the δc-axis voltage command value vδ* and the γc-axis voltage command value vγ* based on the δc-axis current iδc, the γc-axis current iγc, the primary magnetic fluxes λδc and λγc, the primary magnetic flux command Λδ*, and the rotational speed command ωe*. Since this function, the configuration for realizing this function, and the method for estimating the primary magnetic fluxes λδc and λγc are well known, their details are omitted here.

[0057] The speed command correction device 12 includes a γc axis current correction unit 105 (labeled "iγc correction unit" in Figure 7), an adder 107, a subtractor 109, and a high-pass filter 110.

[0058] The γc-axis current correction unit 105 determines a first γc-axis current correction value Δiγc1 based on the rotation angle θm, rotation speed command ωm*, primary magnetic fluxes λδc, λγc, δc-axis current iδc, γc-axis current iγc, and order n. The first γc-axis current correction value Δiγc1 is a quantity that reduces the nth-order component (where n is a positive integer) of the fundamental frequency of the rotation angle θm, and its specific significance and method of calculation will be described later.

[0059] The adder 107 adds a first γc-axis current correction value Δiγc1 to the γc-axis current iγc to obtain a first corrected γc-axis current iγc1. The high-pass filter 110 functions as a DC component removal unit that removes the DC component from the first corrected γc-axis current iγc1 to determine the angular velocity correction amount Δωe*. As shown in the figure, the speed command correction device 12 may further include a constant multiplier unit 108, and the angular velocity correction amount Δωe* may be determined by multiplying the output of the high-pass filter 110 by a predetermined gain Km in the constant multiplier unit 108.

[0060] The subtractor 109 subtracts the angular velocity correction amount Δωe* from the rotational speed command ωeo* for the electrical angle to obtain the corrected rotational speed command ωe*.

[0061] Figure 8 is a block diagram showing a first example configuration of the γc-axis current correction unit in the first embodiment. The γc-axis current correction unit 1105A shown in Figure 8 is an example of the γc-axis current correction unit 105 (see Figure 7). The γc-axis current correction unit 1105A includes an excitation torque extraction unit 105A, an output torque extraction unit 105B, an adder 105g, and a correction amount calculation unit 105h.

[0062] The vibration torque extraction unit 105A includes an angular pulsation extraction unit 105a, an nth-order component extraction unit 105b, a torque conversion unit 105i, and a proportional coefficient multiplication unit 105c.

[0063] The angle pulsation extraction unit 105a calculates the rotation angle difference Δθm from the rotation angle θm and the rotation speed command ωm*. The rotation angle difference Δθm represents the pulsation component of the rotation angle θm with respect to the rotation angle θm when the synchronous motor 3 is rotating at a constant speed.

[0064] The nth-order component extraction unit 105b extracts the nth-order components Δθms(n) and Δθmc(n) of the rotation angle difference Δθm, which are the fundamental frequencies of the rotation angle θm. The nth-order component extraction unit 105b separates the components of the rotation angle difference Δθm to be extracted into a sinusoidal component Δθms(n) and a cosine component Δθmc(n). The specific operation of the nth-order component extraction unit 105b will be described later.

[0065] The torque conversion unit 105i converts the nth-order components Δθms(n) and Δθmc(n) into torque. Specifically, it calculates the nth-order components τvs(n) and τvc(n) of the estimated excitation torque τv of the synchronous motor 3 at a rotation angle θm. For example, the torque conversion unit 105i calculates the product of the moment of inertia J of the mechanical load, the square of the rotation speed command ωm*, and the square of the order n (= -n 2 ·J·ωm* 2 By multiplying by ), the nth-order component of the excitation torque τv is obtained. Specifically, the nth-order sinusoidal component τvs(n) and the cosine component τvc(n) of the excitation torque τv are obtained.

[0066] The excitation torque τv is the value obtained by subtracting the load torque τd of the mechanical load (not shown) driven by the synchronous motor 3 from the output torque τe of the synchronous motor 3.

[0067] τv = τe - τd ···(2)

[0068] The load torque τd is periodic; in other words, the synchronous motor 3 drives a periodic load. An example of this mechanical load is the compression mechanism (compressor) used to compress the refrigerant in an air conditioner.

[0069] The excitation torque τv has components (the "nth-order components" mentioned above) that fluctuate with a period of 1 / n of the period of the rotation angle θm, each with an independent amplitude for its order. For example, if the mechanical load is a single-cylinder compressor, the amplitude of the first-order component corresponding to n=1 will be dominant, and if it is a two-cylinder compressor, the amplitude of the second-order component corresponding to n=2 will be dominant.

[0070] The output torque extraction unit 105B includes an output torque estimation unit 105d, an nth-order component extraction unit 105e, and an apportionment coefficient multiplication unit 105f.

[0071] The output torque estimation unit 105d uses the primary magnetic fluxes λδc and λγc, and the δc-axis currents iδc and γc-axis currents iγc to estimate the output torque τe using equation (7).

[0072] τe=P·(λδc·iγc-λγc·iδc) ···(7)

[0073] Here, we will not deal with the difference between the estimated and actual values ​​of the output torque τe, so for convenience, we will use the expression "output torque τe" for both the output torque τe and its estimated value.

[0074] The nth-order component extraction unit 105e extracts the nth-order components τes(n) and τec(n) of the output torque τe at the fundamental frequency of the rotation angle θm, in the same manner as the nth-order component extraction unit 105b.

[0075] Specifically, the nth-order component extraction units 105b and 105e both use the Fourier transform to obtain the sinusoidal and cosine components of the input quantity. The rotation angle difference Δθm and the output torque τe are both functions of the rotation angle θm, and if both are expressed as a function F(θm), then equation (8) holds.

[0076]

number

[0077] Here, the value a0 is the DC component (0th order component) of the function F(θm), the value an is the amplitude of the cosine value of the nth order component of the function F(θm), and the value bn is the amplitude of the sine value of the nth order component of the function F(θm). In order to perform the Fourier transform described above, the order n and the rotation angle θm are input to the nth order component extraction units 105b and 105e. Note that in equation (8), time t may be used as the integration variable instead of the rotation angle θm. In the calculations performed by the Fourier transform, the rotation angle θm can be substituted with the angle θmf (=ωma·t). ωma represents the average value of the angular velocity (mean angular velocity).

[0078] The nth-order component extraction unit 105b adopts the rotation angle difference Δθm as the function F(θm), outputs the value bn as the sinusoidal component Δθms(n) of the rotation angle difference Δθm, and outputs the value an as the cosine component Δθmc(n) of the rotation angle difference Δθm.

[0079] The nth-order component extraction unit 105e adopts the output torque τe as a function F(θm), outputs the value bn as the sinusoidal component τes(n) of the output torque τe, and outputs the value an as the cosine component τec(n) of the output torque τe.

[0080] The proportional coefficient multiplier unit 105c multiplies either the sinusoidal component τvs(n) or the cosine component τvc(n) by the proportional coefficient K(n) set for each order n. The proportional coefficient multiplier unit 105f multiplies either the sinusoidal component τes(n) or the cosine component τec(n) by the proportional coefficient [1-K(n)]. However, for each order n, 0≦K(n)≦1 holds. Therefore, the proportional coefficient multiplier units 105c and 105f function as proportional units that proportionally divide the sinusoidal component τvs(n) and the sinusoidal component τes(n) by a predetermined proportionality ratio K(n) / [1-K(n)], and proportionally divide the cosine component τvc(n) and the cosine component τec(n) by the same proportionality ratio. The apportionment coefficients K(n) and [1-K(n)] may be provided externally to the apportionment coefficient multipliers 105c and 105f. In this case, the apportionment coefficient multipliers 105c and 105f are implemented using simple multipliers.

[0081] The adder 105g adds the sinusoidal products τvs(n)·K(n),τes(n)·[1-K(n)] for each order n, and adds the cosine products τvc(n)·K(n),τec(n)·[1-K(n)], and outputs the sum of the pairs.

[0082] In the nth-order component extraction units 105b and 105e, multiple order n values ​​may be selected for extraction. For example, if only value 1 is selected as the order n, adder 105g outputs a pair of sums τvs(1)·K(1)+τes(1)·[1-K(1)],τvc(1)·K(1)+τec(1)·[1-K(1)]. Alternatively, if two values ​​1 and 2 are selected as the order n, adder 105g outputs two pairs: the pair τvs(1)·K(1)+τes(1)·[1-K(1)],τvc(1)·K(1)+τec(1)·[1-K(1)] and the pair τvs(2)·K(2)+τes(2)·[1-K(2)],τvc(2)·K(2)+τec(2)·[1-K(2)]. In Figure 8, the slanted " / " attached to the arrows indicates such pairs of inputs and outputs.

[0083] By introducing the nth-order sinusoidal component τds(n) and cosine component τdc(n) of the load torque τd, equation (9) is obtained from equation (2).

[0084] τvs(n)=τes(n)-τds(n) τvc(n)=τec(n)-τdc(n) ···(9)

[0085] Therefore, adder 105g can output the paired values ​​τes(n)-K(n)·τds(n) and τec(n)-K(n)·τdc(n).

[0086] Figure 9 is a block diagram illustrating the configuration of the correction amount calculation unit 105h. The correction amount calculation unit 105h includes a PI control unit 11h and a composite value calculation unit 11y. For simplicity, the case where the order n is 1 is illustrated here.

[0087] The PI control unit 11h is equipped with PI controllers 11hs and 11hc, both of which perform proportional-integral control. PI controller 11hs performs proportional-integral control over the sinusoidal component, while PI controller 11hc performs proportional-integral control over the cosine component.

[0088] The PI controller 11hs takes the value τes(n)-K(n)·τds(n) as input and outputs the result of proportional-integral control applied to it. The PI controller 11hc takes the value τec(n)-K(n)·τdc(n) as input and outputs the result of proportional-integral control applied to it.

[0089] The composite value calculation unit 11y calculates the composite value by combining the results of proportional-integral control of the sinusoidal component obtained by the PI controller 11hs and the results of proportional-integral control of the cosine component obtained by the PI controller 11hc as follows.

[0090] The composite value calculation unit 11y includes multipliers 11j, 11k, and 11p, a sine value generation unit 11q, a cosine value generation unit 11r, and an adder 11s.

[0091] The multiplier 11p takes the order n and the rotation angle θm as input and obtains the product n·θm. The sine value generator 11q takes the product n·θm as input and obtains the sine value sin(n·θm). The cosine value generator 11r takes the product n·θm as input and obtains the cosine value cos(n·θm).

[0092] The multiplier 11j obtains the product of the result obtained by the PI controller 11hs and the sine value sin(n·θm). The multiplier 11k obtains the product of the result obtained by the PI controller 11hc and the cosine value cos(n·θm). The adder 11s performs trigonometric function synthesis to obtain the composite value. Specifically, the adder 11s obtains the composite value as the sum of the product obtained by the multiplier 11j and the product obtained by the multiplier 11k. This composite value is output from the composite value calculation unit 11y as the first γc axis current correction value Δiγc1. This corresponds to using the results obtained by the PI controllers 11hs and 11hc as coefficients of a Fourier series, and determining the first γc axis current correction value Δiγc1 from the result of that Fourier series.

[0093] The first γc-axis current correction value Δiγc1, obtained based on the nth-order components of the excitation torque τv and output torque τe, is reflected in the γc-axis current iγc by the adder 107 (see Figure 7). As a result, the subtractor 109 corrects the rotational speed command ωeo* in a direction that increases in response to the increase in excitation torque τv and / or output torque τe. Thus, since the first γc-axis current correction value Δiγc1 is obtained by performing proportional-integral control over the pulsation of the excitation torque τv and output torque τe, the corrected rotational speed command ωe* is controlled to suppress the pulsation of the excitation torque τv and output torque τe.

[0094] Before performing proportional-integral control in the correction amount calculation unit 105h (see Figure 8), the influence of the excitation torque τv and output torque τe on the rotational speed command ωeo* is apportioned using apportionment coefficients K(n) and [1-K(n)]. This is preferable from the viewpoint that the apportionment ratio can be maintained regardless of the gain of proportional-integral control, and from the viewpoint that a frequency band corresponding to the rotational speed of the machine angle is unnecessary in proportional-integral control.

[0095] When multiple orders n are set, the correction amount calculation unit 105h is provided with a PI control unit 11h and a composite value calculation unit 11y (excluding the adder 11s) for each order. The adder 11s then sums all the outputs of the composite value calculation units 11y provided for each order and outputs the first γc axis current correction value Δiγc1.

[0096] Assume that the apportionment coefficient K(n) is 1 at a certain order n. In this case, the output of the apportionment coefficient multiplier 105f becomes 0, and the output torque τe does not contribute to the first γc axis current correction value Δiγc1, and only the excitation torque τv contributes to the correction of the rotational speed command ωeo*. In this case, the correction of the rotational speed command ωeo* contributes solely to the suppression of the excitation torque τv.

[0097] Assume that the apportionment coefficient K(n) is 0 at a certain order n. In this case, the output of the apportionment coefficient multiplier 105c becomes 0, and the excitation torque τv does not contribute to the first γc axis current correction value Δiγc1, and only the output torque τe contributes to the correction of the rotational speed command ωeo*. In this case, the correction of the rotational speed command ωeo* contributes solely to suppressing the pulsation of the output torque τe, making it easier to keep the amplitude of the current [I] constant.

[0098] Based on the above, the adder 105g, output torque extraction unit 105B, and apportionment coefficient multiplication unit 105c may be omitted, and the γc axis current correction unit 105 may be configured accordingly. In this configuration, the correction amount calculation unit 105h calculates the first γc axis current correction value Δiγc1 using the sinusoidal component τvs(n) and cosine component τvc(n) (more specifically, by applying proportional-integral control to these components) instead of the sinusoidal component τes(n) and cosine component τec(n). Even with this configuration, the excitation torque τv can be suppressed by correcting the rotational speed command ωeo*.

[0099] Similarly, the γc-axis current correction unit 105 may be configured by omitting the adder 105g, the excitation torque extraction unit 105A, and the apportionment coefficient multiplication unit 105f. In this configuration, the correction amount calculation unit 105h calculates the first γc-axis current correction value Δiγc1 by using the sinusoidal component τes(n) and the cosine component τec(n) (more specifically, by applying proportional-integral control to these components) instead of the sinusoidal component τvs(n) and the cosine component τvc(n). Even with this configuration, the pulsation of the output torque τe can be suppressed by correcting the rotational speed command ωeo*.

[0100] As shown above, the amount of vibration suppression of the compressor can be controlled by adjusting the magnitude of the apportionment coefficient K(n) according to the γc-axis current correction unit 1105A shown in Figure 8. The γc-axis current correction unit 1105A determines the nth-order component (excitation torque command) of the excitation torque command value according to the detected or commanded value of the rotational speed of the synchronous motor 3. Then, according to the determined excitation torque command, the γc-axis current correction unit 1105A determines the magnitude of the apportionment coefficient K(n) that controls the vibration amplitude of the compressor to a substantially constant level.

[0101] The γc axis current correction unit 1105A includes a table 23, a subtractor 22, and a PI controller 21.

[0102] Table 23 contains a preset relationship between the rotational speed of the synchronous motor 3 and the excitation torque, which is used to control the vibration amplitude of the compressor to a nearly constant level in a specific operating area. Table 23 corresponds to the table representing the approximate straight line (approximation curve) shown in Figure 3 above. Table 23 is defined by a regression equation or map data representing the approximation curve. The γc-axis current correction unit 1105A determines an excitation torque command based on Table 23 to control the vibration amplitude of the compressor to a nearly constant level, according to the detected or commanded value of the rotational speed of the synchronous motor 3. This excitation torque command is an example of data read from a preset table. By using a preset table, the computational load can be reduced.

[0103] The subtractor 22 calculates the error between the nth-order component of the command value of the excitation torque and the nth-order component of the estimated value of the excitation torque. The nth-order component of the estimated value of the excitation torque is, for example, the sinusoidal component τvs(n) and the cosine component τvc(n).

[0104] The PI controller 21 derives an apportionment coefficient K(n) by PI control that brings the error calculated by the subtractor 22 closer to zero. The apportionment coefficient K(n) may also be calculated by PID control. In PI control or PID control, P represents proportionality, I represents integral, and D represents derivative.

[0105] By deriving the apportionment coefficient K(n) in this way, the vibration amplitude of the compressor is controlled to a nearly constant level in a specific operating area, regardless of the load on the synchronous motor 3 and the change in the rotational speed of the synchronous motor 3. Therefore, it is possible to suppress both compressor vibration and efficiency degradation in a specific operating area.

[0106] Figure 10 is a block diagram showing a second configuration example of the γc-axis current correction unit in the first embodiment. The γc-axis current correction unit 1105B shown in Figure 10 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configuration of the second configuration example (Figure 10) that is the same as the first configuration example (Figure 8) will be omitted by referring to the explanation above.

[0107] The γc-axis current correction unit 1105B determines the nth-order component (magnetic pole position fluctuation amount command) of the command value for the magnitude of the fluctuation in the magnetic pole position of the synchronous motor 3, according to the detected or commanded value of the rotational speed of the synchronous motor 3. Then, according to the determined magnetic pole position fluctuation amount command, the γc-axis current correction unit 1105B determines the magnitude of the apportionment coefficient K(n) that controls the vibration amplitude of the compressor to a substantially constant level.

[0108] The γc axis current correction unit 1105B includes a table 24, a subtractor 22, and a PI controller 21.

[0109] Table 24 is a set of relationships between the rotational speed of the synchronous motor 3 and the magnitude of the fluctuation in magnetic pole position, which are used to control the vibration amplitude of the compressor to a nearly constant level in a specific operating area. Table 24 corresponds to the table representing the approximate straight line (approximation curve) shown in Figure 3 above. Table 24 is defined by a regression equation or map data representing the approximation curve. The γc-axis current correction unit 1105B determines a magnetic pole position fluctuation amount command based on Table 24, according to the detected or commanded value of the rotational speed of the synchronous motor 3, to control the vibration amplitude of the compressor to a nearly constant level. This magnetic pole position fluctuation amount command is an example of data read from a pre-set table.

[0110] The subtractor 22 calculates the error between the nth-order component of the command value for the magnitude of the magnetic pole position fluctuation and the nth-order component of the estimated magnitude of the magnetic pole position fluctuation. The nth-order component of the estimated magnitude of the magnetic pole position fluctuation is, for example, a sinusoidal component Δθms(n) and a cosine component Δθmc(n). The PI controller 21 derives an apportionment coefficient K(n) that brings the error calculated by the subtractor 22 closer to zero, using PI control or the like. By deriving the apportionment coefficient K(n) in this way, vibration suppression of the compressor and suppression of efficiency reduction can be achieved in a specific operating area, similar to the configuration example described above.

[0111] Figure 11 is a block diagram showing a third configuration example of the γc-axis current correction unit in the first embodiment. The γc-axis current correction unit 1105C shown in Figure 11 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configuration of the third configuration example (Figure 11) that is the same as the first configuration example (Figure 8) will be omitted by referring to the explanation above.

[0112] The γc-axis current correction unit 1105C determines the nth-order component (rotational speed fluctuation command) of the command value for the magnitude of the fluctuation in the rotational speed of the synchronous motor 3, according to the detected or commanded value of the rotational speed of the synchronous motor 3. Then, according to the determined rotational speed fluctuation command, the γc-axis current correction unit 1105C determines the magnitude of the apportionment coefficient K(n) that controls the vibration amplitude of the compressor to a substantially constant level.

[0113] The γc-axis current correction unit 1105C includes a table 25, an nth-order component extraction unit 26, a subtractor 22, and a PI controller 21.

[0114] Table 25 is a set of relationships between the rotational speed of the synchronous motor 3 and the magnitude of rotational speed fluctuations, which are used to control the vibration amplitude of the compressor to a nearly constant level in a specific operating area. Table 25 corresponds to the table representing the approximate straight line (approximate curve) shown in Figure 3 above. Table 25 is defined by a regression equation or map data representing the approximate curve. The γc axis current correction unit 1105C determines a rotational speed fluctuation command based on Table 25, according to the detected or commanded value of the rotational speed of the synchronous motor 3, to control the vibration amplitude of the compressor to a nearly constant level. This rotational speed fluctuation command is an example of data read from a pre-set table.

[0115] The nth-order component extraction unit 26 extracts the nth-order component of the estimated magnitude of rotational speed fluctuations based on the detected or commanded value of the rotational speed of the synchronous motor 3. The subtractor 22 calculates the error between the nth-order component of the commanded magnitude of rotational speed fluctuations and the nth-order component of the estimated magnitude of rotational speed fluctuations. The PI controller 21 derives an apportionment coefficient K(n) that brings the error calculated by the subtractor 22 closer to zero, using PI control or the like. By deriving the apportionment coefficient K(n) in this way, vibration suppression of the compressor and suppression of efficiency degradation can be achieved in a specific operating area, similar to the configuration example described above.

[0116] Figure 12 is a block diagram showing a fourth configuration example of the γc-axis current correction unit in the first embodiment. The γc-axis current correction unit 1105D shown in Figure 12 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configuration of the fourth configuration example (Figure 12) that is the same as the first configuration example (Figure 8) will be omitted by referring to the explanation above.

[0117] The γc-axis current correction unit 1105D determines the magnitude of the apportionment coefficient K(n) that controls the vibration amplitude of the compressor to a substantially constant level, based on the table 27, according to the detected or commanded value of the rotational speed of the synchronous motor 3. The γc-axis current correction unit 1105D has a table 27.

[0118] Table 27 is a set of relationships between the rotational speed of the synchronous motor 3, the excitation torque, and the apportionment coefficient K(n) for controlling the vibration amplitude of the compressor to a substantially constant level in a specific operating area. Table 27 corresponds to a table obtained by combining the apportionment coefficient K(n) with the table representing the approximate straight line (approximation curve) shown in Figure 3 above. Table 27 is defined by a regression equation or map data representing the approximation curve. By controlling the excitation torque as per the command values ​​for excitation torque with respect to rotational speed shown in Figure 3, the vibration amplitude can be controlled to a substantially constant level regardless of the load on the motor and changes in the motor's rotational speed. Therefore, in the embodiment shown in Figure 12, the detected or commanded value of the rotational speed of the synchronous motor 3 and the nth-order component of the estimated excitation torque are input to Table 27, and a controllable variable is output from Table 27. In this embodiment, the controllable variable is the apportionment coefficient K(n), and the motor torque is adjusted according to the apportionment coefficient K(n). Furthermore, as mentioned above, the excitation torque on the vertical axis of Figure 3 can be replaced with the magnitude of the fluctuation in magnetic pole position or the magnitude of the fluctuation in rotational speed, but in this embodiment, a more desirable excitation torque is used. The γc-axis current correction unit 1105D determines an apportionment coefficient K(n) based on Table 27 that controls the vibration amplitude of the compressor to a substantially constant level according to the detected or commanded value of the rotational speed of the synchronous motor 3 and the nth-order component of the estimated excitation torque. This apportionment coefficient K(n) is an example of data read from a pre-set table. By deriving the apportionment coefficient K(n) in this way, vibration suppression of the compressor and suppression of efficiency reduction can be achieved in a specific operating area, similar to the configuration example described above.

[0119] In addition, in Table 27, the excitation torque may be replaced with the magnitude of the fluctuation in the magnetic pole position or the magnitude of the fluctuation in rotational speed. Even in this case, the apportionment coefficient K(n) can be derived using Table 27, thereby achieving suppression of compressor vibration and suppression of efficiency degradation in a specific operating area.

[0120] Figure 13 is a block diagram showing a first configuration example of the γc-axis current correction unit in the second embodiment. The γc-axis current correction unit 2105A shown in Figure 13 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configuration of the first configuration example of the second embodiment (Figure 13) that is the same as the first configuration example of the first embodiment (Figure 8) will be omitted by referring to the explanation above.

[0121] The γc-axis current correction unit 2105A determines the nth-order component of the excitation torque command value in the first mode described above (the first excitation torque command) based on Table 35, according to the detected or commanded value of the rotational speed of the synchronous motor 3. Similarly, the γc-axis current correction unit 2105A determines the nth-order component of the excitation torque command value in the second mode described above (the second excitation torque command) based on Table 36, according to the detected or commanded value of the rotational speed of the synchronous motor 3.

[0122] The γc axis current correction unit 2105A includes tables 35 and 36, subtractors 33 and 34, a switching unit 32, a switching determination unit 37, and a PI controller 31.

[0123] Table 35 contains a set relationship between the rotational speed of the synchronous motor 3 and the excitation torque for controlling the compressor vibration amplitude to a first level in a specific operating area in the first mode. The γc-axis current correction unit 2105A determines a first excitation torque command to control the compressor vibration amplitude to a first level based on Table 35, according to the detected or commanded value of the rotational speed of the synchronous motor 3.

[0124] Table 36 shows a preset relationship between the rotational speed of the synchronous motor 3 and the excitation torque for controlling the compressor vibration amplitude to a second level in a specific operating area in the second mode. The γc-axis current correction unit 2105A determines a second excitation torque command to control the compressor vibration amplitude to a second level based on Table 36, according to the detected or commanded value of the rotational speed of the synchronous motor 3.

[0125] The subtractor 33 calculates the first error between the nth-order component of the command value of the excitation torque in the first mode and the nth-order component of the estimated value of the excitation torque. The subtractor 34 calculates the second error between the nth-order component of the command value of the excitation torque in the second mode and the nth-order component of the estimated value of the excitation torque.

[0126] The switching unit 32 switches the error input to the PI controller 31 to either the first error or the second error, according to the determination result by the switching determination unit 37. The switching determination unit 37 determines to input the first error to the PI controller 31 when the load on the synchronous motor 3 falls below a first threshold set for each rotational speed of the synchronous motor 3, and determines to input the second error to the PI controller 31 when the load on the synchronous motor 3 rises above a second threshold set for each rotational speed of the synchronous motor 3. The load on the synchronous motor 3 includes, for example, pressure and temperature. Load information such as pressure and temperature is supplied from outside the compressor.

[0127] The PI controller 31 derives an apportionment coefficient K(n) through PI control or the like, which brings the error input from the switching unit 32 closer to zero. Because the apportionment coefficient K(n) is derived in this way, when the load on the synchronous motor 3 rises above the second threshold, the vibration amplitude of the compressor is controlled to a second level lower than the first level, thereby suppressing the increase in the vibration amplitude of the compressor.

[0128] In addition, in tables 35 and 36, the excitation torque may be replaced with the magnitude of the fluctuation in the magnetic pole position or the magnitude of the fluctuation in rotational speed. Even in this case, if the load on the synchronous motor 3 rises above the second threshold, the vibration amplitude of the compressor is controlled to a second level lower than the first level, thereby suppressing the increase in the vibration amplitude of the compressor.

[0129] Figure 14 is a block diagram showing a second configuration example of the γc-axis current correction unit in the second embodiment. The γc-axis current correction unit 2105B shown in Figure 14 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configurations in the second configuration example of the second embodiment (Figure 14) that are the same as the fourth configuration example of the first embodiment (Figure 12) and the first configuration example of the second embodiment (Figure 13) will be omitted by referring to the explanation above.

[0130] The γc-axis current correction unit 2105B determines the magnitude of the apportionment coefficient K(n) that controls the vibration amplitude of the compressor to a first level, based on table 38, according to the detected or commanded value of the rotational speed of the synchronous motor 3. Similarly, the γc-axis current correction unit 2105B determines the magnitude of the apportionment coefficient K(n) that controls the vibration amplitude of the compressor to a second level, based on table 39, according to the detected or commanded value of the rotational speed of the synchronous motor 3. The γc-axis current correction unit 1105D has tables 38 and 39.

[0131] Table 38 shows the pre-set relationship between the rotational speed of the synchronous motor 3, the excitation torque, and the apportionment coefficient K(n) for controlling the compressor vibration amplitude to a first level. The γc-axis current correction unit 2105A determines the apportionment coefficient K(n) for controlling the compressor vibration amplitude to a first level based on Table 38, according to the detected or commanded value of the rotational speed of the synchronous motor 3 and the nth-order component of the estimated excitation torque. Table 39 shows the pre-set relationship between the rotational speed of the synchronous motor 3, the excitation torque, and the apportionment coefficient K(n) for controlling the compressor vibration amplitude to a second level. The γc-axis current correction unit 2105A determines the apportionment coefficient K(n) for controlling the compressor vibration amplitude to a second level based on Table 39, according to the detected or commanded value of the rotational speed of the synchronous motor 3 and the nth-order component of the estimated excitation torque.

[0132] The switching unit 32 switches the apportionment coefficient K(n) to either a coefficient for controlling to the first level or a coefficient for controlling to the second level, according to the determination result by the switching determination unit 37. The switching determination unit 37 selects the apportionment coefficient K(n) for controlling to the first level when the load on the synchronous motor 3 falls below a first threshold set for each rotational speed of the synchronous motor 3, and selects the apportionment coefficient K(n) for controlling to the second level when the load on the synchronous motor 3 rises above a second threshold set for each rotational speed of the synchronous motor 3. With the apportionment coefficient K(n) derived in this way, when the load on the synchronous motor 3 rises above the second threshold, the vibration amplitude of the compressor is controlled to a second level lower than the first level, thus suppressing the increase in the vibration amplitude of the compressor.

[0133] In addition, in Tables 38 and 39, the excitation torque may be replaced with the magnitude of the fluctuation in the magnetic pole position or the magnitude of the fluctuation in rotational speed. Even in this case, if the load on the synchronous motor 3 rises above the second threshold, the vibration amplitude of the compressor is controlled to a second level lower than the first level, thereby suppressing the increase in the vibration amplitude of the compressor.

[0134] Figure 15 is a block diagram showing a first configuration example of the γc-axis current correction unit in the third embodiment. The γc-axis current correction unit 3105A shown in Figure 15 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configuration of the first configuration example of the third embodiment (Figure 15) that is the same as the first configuration example of the first embodiment (Figure 8) and the first configuration example of the second embodiment (Figure 13) will be omitted by referring to the explanation above.

[0135] The γc-axis current correction unit 3105A has a control unit 41 that determines the apportionment coefficient K(n) in the third mode described above, according to the voltage value applied to the synchronous motor 3 and the current value flowing through the synchronous motor 3.

[0136] The control unit 41 controls the voltage or current supplied from the inverter in the voltage supply source 2 to the synchronous motor 3 so as to suppress the vibration amplitude of the compressor to a first level or lower. For example, if the control unit 41 detects that the vibration amplitude of the compressor cannot be maintained at the second level for a predetermined time or longer in the second mode, it generates a proportional coefficient K(n) to suppress the vibration amplitude of the compressor to a first level or lower, and switches the operating mode of the compressor from the second mode to the third mode using the switching unit 42. The control unit 41 adjusts the proportional coefficient K(n) so that the voltage or current supplied to the synchronous motor 3 is limited to a predetermined value or lower that suppresses the vibration amplitude of the compressor to a first level or lower.

[0137] Because the apportionment coefficient K(n) is derived in this way, even if the compressor vibration amplitude cannot be controlled to the second level by some factor, the compressor vibration amplitude is controlled between the first and second levels, thus suppressing the compressor vibration.

[0138] Figure 16 is a block diagram showing a second configuration example of the γc-axis current correction unit in the third embodiment. The γc-axis current correction unit 3105B shown in Figure 16 is an example of the γc-axis current correction unit 105 (see Figure 7). The explanation of the configuration of the second configuration example of the third embodiment (Figure 16) that is the same as the first configuration example of the first embodiment (Figure 8) and the first configuration example of the third embodiment (Figure 15) will be omitted by referring to the explanation above. The configuration of Figure 16 is obtained by replacing tables 35 and 36 of Figure 15 with tables 38 and 39 of Figure 14. In the configuration of Figure 16, as in the case of Figure 15, even if the vibration amplitude of the compressor cannot be controlled to the second level for some reason, the vibration amplitude of the compressor is controlled between the first level and the second level, so the vibration of the compressor can be suppressed.

[0139] Thus, according to the compressor control method of this disclosure, in a specific operating area, the vibration amplitude of the compressor is controlled to be substantially constant regardless of changes in the load on the motor and the rotational speed of the motor, thereby suppressing compressor vibration.

[0140] Conventionally, there are technologies (Patent No. 3874865, Patent No. 4596906) that limit speed fluctuations to a constant level or 2-50% in order to reduce vibration and suppress efficiency degradation. However, in both cases, controlling speed fluctuations to a constant level can lead to excessive vibration suppression control, potentially reducing efficiency. There is also a technology (Patent No. 6364463) that changes the limit based on both rotational speed and load magnitude. However, if the limit range of speed fluctuations is changed not only by rotational speed but also by load magnitude, it is not possible to control the vibration amplitude of the compressor to a nearly constant level, and similarly, efficiency may decrease. The present invention is characterized by controlling the vibration amplitude to be nearly constant rather than the speed fluctuation. The excitation torque for controlling to a certain vibration amplitude with respect to rotational speed can be linearly and easily tuned, and vibration suppression and efficiency improvement can be achieved without applying excessive vibration suppression control.

[0141] Although embodiments have been described above, it will be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims. Various modifications and improvements are possible, such as combinations or substitutions with parts or all of other embodiments. [Explanation of Symbols]

[0142] 1. Electric motor control device 3 Synchronous motor 12 Speed ​​command correction device 1105A~1105D,2105A,2105B,3105A,2105B γc axis current correction section

Claims

1. A compressor control method for controlling the vibration amplitude of a compressor equipped with a motor using the motor, The compressor is a device driven by the motor, A compressor control method that controls the vibration amplitude to be substantially constant in a specific operating area, regardless of changes in the load on the motor and the rotational speed of the motor, This includes controlling the vibration amplitude to a substantially constant level by performing vibration suppression control, which involves changing the variable that increases or decreases according to the vibration amplitude to a value corresponding to the motor rotation speed, based on the relationship between the motor rotation speed and a variable that increases or decreases according to the vibration amplitude, thereby controlling the vibration amplitude to a substantially constant level. In the aforementioned specific operating areas, in the operating area where the load on the motor decreases to below a first threshold set for each rotational speed of the motor, the vibration amplitude is controlled to a first level. In the aforementioned specific operating areas, in the operating area where the load on the motor rises above a second threshold set for each rotational speed of the motor, the vibration amplitude is controlled to a second level. The first threshold is less than or equal to the second threshold. A compressor control method wherein the second level is lower than the first level and higher than zero.

2. The aforementioned variables are the excitation torque generated by the difference between the load torque received by the motor and the motor torque generated by the motor, the magnitude of the fluctuation in the magnetic pole position of the motor, or the magnitude of the fluctuation in the rotational speed of the motor. The compressor control method according to claim 1, wherein the excitation torque, the magnitude of the fluctuation of the magnetic pole position, or the magnitude of the fluctuation of the rotational speed changes according to the rotational speed of the motor.

Images