JP7042028B2 - Motor control device and air conditioner - Google Patents

Description

The present invention relates to a motor control device and an air conditioner.

Conventionally, a motor control device that controls an inverter to drive a motor has been known. In a motor that obtains field magnetic flux with a permanent magnet, the counter electromotive force increases as the rotation speed increases, so when a certain rotation speed is exceeded, the torque drops sharply due to a decrease in the armature current and magnetic flux. In order to prevent such a decrease in torque, for example, Patent Document 1 discloses a motor control device that performs weakening magnetic flux control (weakening field control) that weakens the applied voltage in a high rotation range.

Japanese Patent No. 5056106

As the weakening magnetic flux control, there is a method of determining and outputting the d-axis current command value corresponding to the q-axis current command value calculated according to the rotation speed command according to the theoretical formula of the weakening magnetic flux control. However, as shown in FIG. 10A, when the calculated q-axis current command value varies (see ΔIq *), the d-axis is calculated according to the theoretical formula for weakening magnetic flux control (formula representing curve C2). Unexpected fluctuations (see ΔId *) occur in the current command value.

Further, since the theoretical formula for weakening magnetic flux control includes the maximum voltage Vam (upper limit value of the terminal voltage of the motor) and the rotation speed ω of the motor as variables, the d-axis current command value calculated based on the theoretical formula is these. It also depends on the variables of. Therefore, as shown in FIG. 10B, even if the input values of the maximum voltage Vam and the rotation speed ω vary, the d-axis current command value calculated according to the weakening magnetic flux control theory unexpectedly fluctuates ( ΔId *) occurs.

Due to these factors, the calculated d-axis current command value may fluctuate to the extent that stable operation of the motor becomes difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device and an air conditioning device capable of stably operating a motor.

In order to achieve the above object, the motor control device according to the first aspect of the present invention is
A motor control device that drives the motor via an inverter according to the d-axis current command value and the q-axis current command value determined according to the target rotation speed of the motor.
A d-axis current control means that acquires the determined q-axis current command value and determines the d-axis current command value based on the acquired q-axis current command value.
A discriminating means for determining whether or not the motor is driven by weakening magnetic flux control, and
It is provided with a correction means capable of executing torque control for correcting the q-axis current command value in order to suppress the rotation speed fluctuation of the motor.
The discrimination means determines that the motor is driven by the weakening magnetic flux control when the rotation speed of the motor is equal to or higher than a predetermined switching rotation speed.
The correction means executes the torque control when the deviation between the target rotation speed and the rotation speed of the motor exceeds an allowable value regardless of whether or not the discrimination means determines that the motor is driven by weakening magnetic flux control. However, if the deviation does not exceed the permissible value, the torque control is not executed and the torque control is not executed.
The d-axis current control means has acquired the q-axis current command value when the correction means executes the torque control even when the discriminating means determines that the motor is weakened and driven by the magnetic flux control. The d-axis current command value is determined as a predetermined value obtained based on a specific function, which is a value obtained regardless of the above.
The specific function is a function that does not depend on the q-axis current command value and is derived from the function of the current limiting curve and the function of the curve according to the weakening magnetic flux control theory.
The predetermined value is a value at which the motor does not saturate the voltage, and is a value corresponding to the intersection of the current limiting curve and the curve according to the weakening magnetic flux control theory.

Further, the d-axis current control means may gradually change the d-axis current command value from the current value to the predetermined value when the d-axis current command value is determined to be the predetermined value.

In order to achieve the above object, the air conditioner according to the second aspect of the present invention is
With the motor control device
It includes the inverter, the motor, a compressor driven by the motor, and an air conditioning unit that adjusts the room temperature by using the refrigerant compressed by the compressor.

According to the present invention, the motor can be operated stably.

It is a schematic diagram which shows the structure of the air conditioner which concerns on one Embodiment of this invention. (A) to (d) are sectional views of a compressor at each angle of a motor. It is a graph which shows the fluctuation of the load torque with respect to the angle of a motor. It is a block diagram which shows the structure of the motor control part which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the torque control part which concerns on one Embodiment of this invention. When torque control is not executed, (a) is a graph showing the fluctuation of the load torque with respect to the angle of the motor, (b) is a graph showing the fluctuation of the output torque with respect to the angle of the motor, and (c) is the graph showing the fluctuation of the output torque with respect to the angle of the motor. It is a graph which shows the fluctuation of the rotation speed with respect to. When torque control is executed, (a) is a graph showing the fluctuation of the load torque with respect to the angle of the motor, (b) is a graph showing the fluctuation of the output torque with respect to the angle of the motor, and (c) is the graph showing the fluctuation of the output torque with respect to the angle of the motor. It is a graph which shows the fluctuation of the rotation speed with respect to. It is a graph which shows the control range of a current vector. It is a flowchart which shows the d-axis current control processing which concerns on one Embodiment of this invention. (A) and (b) are diagrams for explaining the fluctuation factor of the d-axis current command value generated at the time of weakening magnetic flux control.

An embodiment of the motor control device and the air conditioner according to the present invention will be described with reference to the drawings.
As shown in FIG. 1, the air conditioner 1 includes a control unit 10, an inverter 20, a motor 30, a compressor 40, a power supply 50, a shunt resistance 19, current sensors 35v, 35w, and an air conditioning unit 60. , Equipped with.

The power supply 50 generates a DC voltage from a commercial power supply (not shown), and applies the generated DC voltage to the inverter 20.

The shunt resistor 19 is inserted in the connection line between the power supply 50 and the inverter 20 for overcurrent detection. The shunt resistor 19 outputs a current detection signal Sp1 for detecting the current flowing through the connection line to the inverter 20.

The inverter 20 transfers the DC current supplied from the power supply 50 to the three-phase, that is, the U-phase, V-phase, and W-phase alternating currents Iu, Iv, and Iw based on the PWM signals Su, Sv, and Sw from the control unit 10. It is converted, and the converted AC currents Iu, Iv, and Iw are supplied to the motor 30. The inverter 20 is composed of, for example, an IPM (Intelligent Power Module). The inverter 20 receives the current detection signal Sp1 from the shunt resistor 19 and outputs an overcurrent detection signal Sp2 indicating the presence or absence of an overcurrent to the control unit 10.

The motor 30 is a three-phase brushless motor. The motor 30 rotates by receiving alternating currents Iu, Iv, and Iw from the inverter 20, thereby driving the compressor 40.

The current sensor 35v detects the value of the V-phase current Iv flowing through the motor 30, and outputs a signal indicating the detected value to the control unit 10. The current sensor 35w detects the value of the W-phase current Iw flowing through the motor 30, and outputs a signal indicating the detected value to the control unit 10. Each of the current sensors 35v and 35w is composed of, for example, a CT (current transformer) sensor or a Hall element.

The compressor 40 is driven by the motor 30 to compress the sucked refrigerant and discharge the compressed refrigerant. The specific configuration of the compressor 40 will be described later.

The air conditioning unit 60 adjusts the room temperature by using the refrigerant compressed by the compressor 40. Specifically, the air conditioning unit 60 is compressed by an indoor heat exchanger 63 that exchanges heat with the indoor air, an outdoor heat exchanger 64 that exchanges heat with the outdoor air, an expansion valve 65 that reduces the pressure of the refrigerant, and a compressor 40. A four-way valve 66 for switching the flow path of the generated refrigerant to either the outdoor heat exchanger 64 or the indoor heat exchanger 63 is provided.

Explaining the cooling operation, the four-way valve 66 sends the refrigerant compressed by the compressor 40 to the outdoor heat exchanger 64. The outdoor heat exchanger 64 functions as a gas cooler for cooling the refrigerant during cooling operation, and discharges the heat of the refrigerant to the outside by exchanging heat between the outdoor air and the refrigerant. After that, this refrigerant is decompressed and expanded by the expansion valve 65, and then sent to the indoor heat exchanger 63. The indoor heat exchanger 63 functions as an evaporator during the cooling operation, and by evaporating the refrigerant, heat is exchanged between the indoor air and the refrigerant, and the temperature of the indoor air is lowered. As a result, the room temperature is adjusted. Then, the refrigerant that has passed through the indoor heat exchanger 63 returns to the compressor 40 via the four-way valve 66.

Explaining the heating operation, the four-way valve 66 sends the refrigerant compressed by the compressor 40 to the indoor heat exchanger 63. The indoor heat exchanger 63 functions as a gas cooler for cooling the refrigerant, and raises the temperature of the indoor air by exchanging heat between the indoor air and the refrigerant. As a result, the room temperature is adjusted. Then, the expansion valve 65 decompresses and expands the refrigerant that has passed through the indoor heat exchanger 63, and then sends the refrigerant to the outdoor heat exchanger 64. The outdoor heat exchanger 64 functions as an evaporator and evaporates the refrigerant to exchange heat between the outdoor air and the refrigerant. After that, the four-way valve 66 returns the heat-exchanged refrigerant to the compressor 40.

In this example, the compressor 40 is a single rotary type, slide vane type compressor. Specifically, as shown in FIGS. 2A to 2D, the compressor 40 includes a cylindrical cylinder 41, a cylindrical rotor 42 that is eccentrically rotated in the cylinder 41 by a motor 30, and a rotor 42. A vane 43 that divides the inside of the cylinder 41 into a suction chamber 46a and a compression chamber 46b with eccentric rotation is provided.

The vane 43 penetrates the peripheral wall of the cylinder 41, and its tip is located inside the cylinder 41. The tip of the vane 43 is pressed against the peripheral surface of the rotor 42 by an urging member such as a spring (not shown). The cylinder 41 is formed with an discharge port 41o and a suction port 41i located across the vane 43. The suction port 41i is a hole for sucking the refrigerant into the cylinder 41. The discharge port 41o is a hole for discharging the compressed refrigerant from the inside of the cylinder 41. The discharge port 41o is provided with a discharge valve 47o that opens and closes the discharge port 41o. The suction port 41i is provided with a suction valve 47i that opens and closes the suction port 41i. The rotor 42 revolves along the inner peripheral surface of the cylinder 41 while rotating on its axis as the motor 30 rotates.

As shown in FIG. 2A, when the angle θ of the motor 30 is 0 °, the rotor 42 retracts the tip of the vane 43 to a position where it coincides with the inner peripheral surface of the cylinder 41. At this time, the cylinder 41 is filled with the sucked refrigerant.
As shown in FIG. 2B, when the angle θ of the motor 30 rotates to 120 ° with the suction valve 47i open and the discharge valve 47o closed, the rotor 42 moves to the inner peripheral surface of the cylinder 41. Rotate 120 ° counterclockwise in the figure along. At this time, the refrigerant is sucked into the suction chamber 46a through the suction port 41i, and the refrigerant in the compression chamber 46b is compressed. As shown in FIG. 2C, when the angle θ of the motor 30 is further rotated to 180 °, the refrigerant in the compression chamber 46b is further compressed, and the temperature of the refrigerant rises. As shown in FIG. 2D, when the angle θ of the motor 30 rotates to about 240 °, the pressure in the compression chamber 46b increases and the discharge valve 47o opens. As a result, the compressed refrigerant is discharged.

In this way, while the motor 30 makes one revolution, the compressor 40 performs suction, compression, and discharge. Therefore, as shown in the graph of FIG. 3, the load torque of the motor 30 fluctuates greatly during one rotation of the motor 30. This fluctuation in load torque is also called torque pulsation. This torque pulsation is remarkably generated in the slide vane type compressor among various compressors. Further, as illustrated in FIG. 3, the fluctuation patterns A1 to A3 of the load torque are different depending on the operating load and the like in the air conditioner 1. In this example, the fluctuation pattern A1 has a larger operating load than the fluctuation patterns A2 and A3, and the fluctuation pattern A2 has a larger operating load than the fluctuation pattern A3. The fluctuation patterns A1 to A3 have different peak values at which the load torque is maximized, and also have different peak positions, which are angles θ of the motors 30 that take the peak values. The fluctuation pattern due to torque pulsation is not limited to the fluctuation patterns A1 to A3, and exists innumerably due to various factors such as the discharge pressure and suction pressure of the compressor 40 and the secular variation of the compressor 40.

The control unit 10 shown in FIG. 1 controls the operation of the motor 30 via the inverter 20, is composed of a microcomputer, and has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). ) And so on. The ROM stores in advance fixed data such as an operation program (including a program for executing the d-axis current control process described later) and table data that define the processing procedure of the CPU. The RAM temporarily stores various calculation results and the like. For example, the RAM stores data indicating a discrimination result or a determination result in the d-axis current control process described later.

The control unit 10 includes an operation command unit 11 and a motor control unit 12 as functional units.
The operation command unit 11 commands the operation of the air conditioner 1 in response to, for example, the operation of the remote controller by the user. The operation command unit 11 calculates the target rotation speed ω0 (rotation speed command) of the motor 30 based on, for example, the indoor temperature and the outdoor temperature acquired by a sensor (not shown), and the target temperature set by the user, and the calculated target rotation. The rotation speed ω0 is output to the motor control unit 12.

The motor control unit 12 controls the motor 30 by vector control.
As shown in FIG. 4, the motor control unit 12 includes a three-phase current calculation unit 121, a current conversion unit 122, a position estimation unit 123, a speed control unit 124, and a d-axis current control unit 125 as functional units. , A current control unit 126, a voltage conversion unit 127, a PWM signal generation unit 128, and a torque control unit 13.

The three-phase current calculation unit 121 acquires the values of the V-phase and W-phase currents Iv and Iw through the current sensors 35v and 35w. Then, the three-phase current calculation unit 121 sets the value of the U-phase current Iu by utilizing the fact that the sum of the three-phase currents Iu, Iv, and Iw becomes zero based on the acquired current values Iv and Iw. Calculate. At this time, the three-phase current calculation unit 121 acquires the values of the currents Iv and Iw a plurality of times, and takes the average value thereof. Further, the three-phase current calculation unit 121 takes an average value without including the values of the currents Iv and Iw at that time when an overcurrent is generated based on the overcurrent detection signal Sp2 from the inverter 20, for example.

The current conversion unit 122 coordinates-converts the three-phase currents Iu, Iv, and Iw calculated by the three-phase current calculation unit 121 into the two-phase q-axis current Iq and the d-axis current Id. The q-axis current Iq is a torque component of the motor 30, and the d-axis current Id is a magnetic flux component of the motor 30.

The position estimation unit 123 has a q-axis current Iq and a d-axis current Id converted by the current conversion unit 122, and a q-axis voltage command value Vq and a d-axis voltage command value Vd calculated by the current control unit 126 described later. Based on this, the angle θ (rotational position) of the motor 30 is estimated. Further, the position estimation unit 123 estimates the rotation speed ω (rotation speed) of the motor 30, which is the rotation speed information, by differentiating the estimated angle θ of the motor 30.

The speed control unit 124 performs feedback control for calculating the q-axis current command value Iq * (target q-axis current) so that the rotation speed ω of the motor 30 matches the target rotation speed ω0 from the operation command unit 11. For example, the speed control unit 124 obtains the deviation ωe (ωe = ω0−ω) between the target rotation speed ω0 and the rotation speed ω. Then, the speed control unit 124 obtains the q-axis current command value Iq * by Iq * = k1 · ωe + k2 ∫ωedt by PI control based on the deviation ωe. Note that k1 is the feedback gain of the proportional element, and k2 is the feedback gain of the integrating element. Further, the feedback control performed by the speed control unit 124 is not limited to the PI control, and may be a control using at least one of P (proportional), I (integral), and D (differential).

The torque control unit 13 calculates the torque correction current Iq *'based on the rotation speed ω estimated by the position estimation unit 123 and the q-axis current Iq and the d-axis current Id converted by the current conversion unit 122. The adder 14 adds the torque correction current Iq *'and the q-axis current command value Iq * calculated by the speed control unit 124. As a result, the corrected q-axis current command value Iq * ″ is calculated. This torque correction current Iq *'is set to a value that stabilizes the rotational speed ω of the motor 30 regardless of the load fluctuation due to torque pulsation.

In this embodiment, as will be described later, torque control (correction of the q-axis current command value Iq *) by the torque control unit 13 may or may not be performed. When the torque control by the torque control unit 13 is not performed, the torque correction current Iq *'is 0 (Iq *'= 0) as described later, and the q-axis current value Iq *'' output from the adder 14 Is the q-axis current command value Iq * calculated by the speed control unit 124 as it is. The specific configuration and processing contents of the torque control unit 13 will be described later.

The d-axis current control unit 125 determines the d-axis current command value Id * according to the q-axis current command value Iq * ″ output from the adder 14, and outputs the d-axis current command value Id * to the current control unit 126. Further, the d-axis current control unit 125 acquires the rotation speed ω estimated by the position estimation unit 123, and also acquires the maximum voltage Vam (upper limit value of the terminal voltage of the motor 30) from a voltage sensor (not shown). These rotation speed ω and maximum voltage Vam are also used to determine the d-axis current command value Id *.

Specifically, the d-axis current control unit 125 selects one of the following first to third control modes according to the conditions, and the method according to the selected mode (the following (Equation 1) to (Equation 3). ) Is used to calculate the d-axis current command value Id *. The d-axis current control unit 125 calculates the d-axis current command value Id * by using the data and the table showing the following equations (Equation 1) to (Equation 3) stored in the ROM in advance. The first to third control modes will be described below.

(1st control mode: maximum torque control)
At the start of driving the motor 30, the d-axis current control unit 125 calculates the d-axis current command value Id * based on the q-axis current command value Iq *'' acquired from the adder 14 and the following equation (Equation 1). .. As a result, the maximum torque control as the first control mode is executed. In the maximum torque control, the current vector is controlled so that the maximum torque can be obtained with the minimum current according to the maximum torque control curve C1 (see FIG. 8) represented by the following equation (Equation 1). K1 is a coefficient obtained by K1 = Kf / {2 (ρ-1)}, and Kf is a coefficient obtained by Kf = Ψ / Ld. ρ is a salient pole coefficient (ρ = Lq / Ld), Lq and Ld are q and d-axis armature self-inductances, and Ψ is the number of magnetic flux chain crossings. Further, "Iq" in the following (Equation 1) is the q-axis current command value Iq *'' acquired from the adder 14, and "Id" is the d-axis current command value Id * calculated by the d-axis current control unit 125. Equivalent to.

When the induced voltage of the motor 30 does not reach the applied voltage (when voltage saturation does not occur), the d-axis current control unit 125 calculates the d-axis current command value Id * by the equation (Equation 1), and the maximum torque. Take control. Specifically, the d-axis current control unit 125 controls the maximum torque when the rotation speed ω acquired from the position estimation unit 123 is less than the switching rotation speed ω1 corresponding to the case where the motor 30 is in the voltage saturation state. To execute. The switching rotation speed ω1 varies depending on the load of the motor 30. On the other hand, the d-axis current control unit 125 has a second control mode in which the applied voltage is weakened in order to prevent the torque from decreasing due to the increase in the induced voltage when the rotation speed ω becomes the switching rotation speed ω1 or more. Weak magnetic flux control is performed.

(Second control mode: weak magnetic flux control)
When the weakening magnetic flux control is executed, the d-axis current control unit 125 uses the q-axis current command value Iq *'' acquired from the adder 14, the upper limit value Vam of the terminal voltage of the motor 30, and the following equation (Equation 2). Based on this, the d-axis current command value Id * is calculated. In the weakening magnetic flux control, the current vector is controlled so that the motor 30 does not saturate the voltage according to the weakening magnetic flux control curve (voltage limiting curve) C2 (see FIG. 8) represented by the following (Equation 2). In the following (Equation 2), "Iq" is the q-axis current command value Iq *'' acquired from the adder 14, and "Id" is the d-axis current command value Id * calculated by the d-axis current control unit 125. Equivalent to.

(Third control mode)
The d-axis current control unit 125 sets the d-axis current command value Id * as the third control mode when the torque control is executed by the torque control unit 13 even during the period in which the weakening magnetic flux control is executed. It is determined to be a predetermined value which is not related to the q-axis current command value Iq *'' acquired from 14. The d-axis current control unit 125 determines whether or not torque control is currently being executed by referring to the torque control executing flag described later.
In the third control mode, the d-axis current control unit 125 has a value I2 corresponding to the intersection point N2 between the weak magnetic flux control curve C2 representing the above equation (Equation 2) and the current limiting curve C3 representing the following equation (Equation 3). Is determined as the d-axis current command value Id *. Iam is a limit value of the armature current of the motor 30, and is a value determined by the rated current of the motor 30 or the maximum output current of the inverter 20. Therefore, the intersection N2 between the current limiting curve C3 and the weakening magnetic flux control curve C2 represents the current vector in which the torque generated during the weakening magnetic flux control is maximized under the current limitation.

Specifically, the d-axis current control unit 125 rotates with the maximum voltage Vam into an IQ-independent function obtained by substituting one IQ of the equations (2) and (3) into the other. The value of Id obtained by substituting the number ω is determined as the d-axis current command value Id *. At this time, instead of the rotation speed ω estimated by the position estimation unit 123, the target rotation speed ω0 output by the operation command unit 11 is substituted for ω in the equation.

As can be seen from the above, in the second control mode, the value corresponding to the input q-axis current command value Iq *'' is set to the d-axis current command value Id * according to the equation (Equation 2) representing the weakening magnetic flux control curve C2. On the other hand, in the third control mode, the predetermined value I2 is determined to be the d-axis current command value Id * regardless of the input q-axis current command value Iq *''. In this way, the reason why the d-axis current command value Id * is set to a predetermined value regardless of the input q-axis current command value Iq *'' in the third control mode is due to the torque control by the torque control unit 13 described later. If this is done, the q-axis current command value Iq *'' does not theoretically become a variation factor, but in reality, the q-axis current command value Iq *'' tends to vary. Further, the reason why the predetermined value is set to I2 is input if the d-axis current command value Id * is set to a value corresponding to the intersection N2 where the generated torque at the time of weakening magnetic flux control is maximized under the current limit. This is because the weakening magnetic flux effect can be exhibited regardless of the q-axis current command value Iq *''. The d-axis current command value Id * determined in the third control mode is not limited to I2 corresponding to the intersection N2, and is arbitrary as long as the motor 30 does not saturate the voltage as described in a later modification. Is.

Returning to FIG. 4, the current control unit 126 calculates the q-axis voltage command value Vq for matching the current q-axis current Iq with the q-axis current command value Iq * ″. Further, the current control unit 126 calculates the d-axis voltage command value Vd for matching the current d-axis current Id with the d-axis current command value Id *. At this time, the current control unit 126 may perform feedback control by PI control by the same calculation method as the speed control unit 124, or may perform feedback control such as PD and PID.

The voltage conversion unit 127 converts the q-axis voltage command value Vq and the d-axis voltage command value Vd calculated by the current control unit 126 into U-phase, V-phase, and W-phase voltage command values Vu, Vv, and Vw.

The PWM signal generation unit 128 pulse-width-modulates the DC voltage according to the voltage command values Vu, Vv, Vw of the U-phase, V-phase, and W-phase coordinate-converted by the voltage conversion unit 127, thereby performing the PWM signal Su, Sv. , Sw is generated. The PWM signal generation unit 128 outputs the PWM signals Su, Sv, Sw to the inverter 20.

(Torque control unit 13)
Next, a specific configuration of the torque control unit 13 will be described.
As shown in FIG. 5, the torque control unit 13 includes a torque pulsation estimation unit 13a, a low-pass filter 13e, and a correction torque current calculation unit 13f.

The torque pulsation estimation unit 13a suppresses the rotation speed fluctuation due to the torque pulsation based on the q-axis current Iq and the d-axis current Id converted by the current conversion unit 122 and the rotation speed ω estimated by the position estimation unit 123. Estimate the missing torque.

Specifically, the torque pulsation estimation unit 13a includes a motor output torque calculation unit 13b, a motor load torque calculation unit 13c, and a subtractor 13d.

The motor output torque calculation unit 13b is the output torque Ta of the motor 30 based on the product of the motor current Ia estimated from the q-axis current Iq and the d-axis current Id converted by the current conversion unit 122 and the torque coefficient K of the motor 30. = K · Ia) is calculated. The output torque Ta is the torque actually output by the motor 30. The motor current Ia is, for example, a combined current of the q-axis current Iq and the d-axis current Id. In the present embodiment, the motor current Ia is estimated from the q-axis current Iq and the d-axis current Id, but the motor current Ia may be estimated only from the q-axis current Iq in order to simplify the control. good.

The motor load torque calculation unit 13c is the load torque Tb of the motor 30 due to the product of the angular acceleration α (= dω / dt) obtained by the time derivative of the rotational speed ω of the motor 30 and the moment of inertia J of the output shaft of the motor 30. Calculate (= J · α). The load torque Tb is a torque that hinders the rotation of the output shaft of the motor 30, and is generally a load due to an internal interference force received by the output shaft of the motor 30 such as centrifugal force and Coriolis force, and the above-mentioned torque pulsation and the like. It is obtained by the sum of the load due to the external force and the load due to friction.

The subtractor 13d calculates the differential torque Tc (= Ta−Tb) by subtracting the load torque Tb from the output torque Ta. This differential torque Tc is a torque that is insufficient to stabilize the rotation speed ω.

The low-pass filter 13e removes high-frequency noise superimposed on the differential torque Tc. The low-pass filter 13e is, for example, a first-order lag filter. The cutoff frequency of the low-pass filter 13e is set higher than the frequency of the rotation speed fluctuation component due to torque pulsation and lower than the frequency of the rotation speed fluctuation component other than torque pulsation, based on, for example, an experiment.

The correction torque current calculation unit 13f calculates the torque correction current Iq *'as the q-axis current value of the value corresponding to the difference torque Tc based on the difference torque Tc that has passed through the low-pass filter 13e. Specifically, the torque correction current Iq *'is obtained by dividing the differential torque Tc by the torque coefficient K (Iq *'= Tc / K).

Further, the correction torque current calculation unit 13f sets the value of the output torque correction current Iq *'to 0 (zero) in a predetermined case. That is, in this case, the torque control unit 13 does not perform torque control (correction of the q-axis current value Iq *). Specifically, the correction torque current calculation unit 13f can acquire the target rotation speed ω0 and the rotation speed ω, and the calculated deviation Δω (Δω = | ω0-ω |) is stored in the ROM in advance. If the allowable value is not exceeded, torque control is not executed (torque correction current Iq *'is set to 0). The permissible value is predetermined as, for example, the maximum rotation speed fluctuation value within a range in which sound or vibration can be tolerated as a device. In this way, in the rotation range where the deviation Δω does not exceed the permissible value and the fluctuation of the rotation speed is considered to be relatively small (for example, the high rotation range where the load pulsation is small), the rotation speed is not executed without torque control. Since ω is stable, torque control is not executed.

When the correction torque current calculation unit 13f calculates the torque correction current Iq *'as the q-axis current value of the value corresponding to the difference torque Tc, the torque control execution flag is turned on to indicate that the torque control is being executed. By setting it to, it is stored in the RAM. On the other hand, when the value of the torque correction current Iq *'is set to 0, the correction torque current calculation unit 13f clears the torque control executing flag to the off state to indicate that the torque control is not currently executed, thereby causing the RAM. Remember in. Whether or not torque control is being executed is a criterion for determining whether to shift to the second control mode or the third control mode in the d-axis current control process described later.

As described above, the torque control unit 13 constantly monitors the output torque Ta and the load torque Tb when executing the torque control, and the torque correction current Iq so that the output torque Ta and the load torque Tb are balanced. * Adjust'. As a result, the output torque Ta and the load torque Tb become equal to each other, so that the rotational speed ω of the motor 30 becomes stable.

When the torque control unit 13 does not perform torque control (correction of the q-axis current command value), the load torque Tb fluctuates due to the above-mentioned torque pulsation as schematically shown in FIG. 6A. As schematically shown in (b), the output torque Ta is constant. Therefore, as schematically shown in FIG. 6C, theoretically, the rotational speed ω of the motor 30 fluctuates due to torque pulsation and becomes unstable. However, as described above, in this embodiment, when the deviation Δω of the rotation speed does not exceed the allowable value and it can be considered that the rotation speed ω is stable without executing torque control (for example, high rotation where the load pulsation becomes small). Since the torque control is not executed in the range), there is no problem as an actual machine regarding the fluctuation of the rotation speed ω of the motor 30.
On the other hand, for example, in the low rotation speed region where the load pulsation is larger than in the high rotation speed region, the deviation Δω of the rotation speed exceeds the allowable value, and the torque control unit 13 performs torque control. When torque control is performed by the torque control unit 13, the output torque Ta fluctuates according to the fluctuation of the load torque Tb due to the torque pulsation described above, as schematically shown in FIGS. 7 (a) and 7 (b). do. Therefore, as schematically shown in FIG. 7 (c), the rotational speed ω of the motor 30 is stable regardless of the torque pulsation. The above is the description of the overall configuration of the motor control unit 12.

Subsequently, it is executed by the d-axis current control unit 125, and one of the first to third control modes is selected according to the conditions, and the d-axis current command value corresponding to each mode is determined and output. The control process will be described with reference to the flowchart of FIG. The d-axis current control process is continuously executed while the motor 30 is being driven. At the start of driving the motor 30, the d-axis current control unit 125 executes the first control mode (maximum torque control) by default.

(D-axis current control processing)
When the d-axis current control process is started, first, the d-axis current control unit 125 acquires the q-axis current command value Iq *'', the rotation speed ω, and the maximum voltage Vam (step S1).

Subsequently, the d-axis current control unit 125 determines whether or not to execute the weakening magnetic flux control (step S2). Specifically, the d-axis current control unit 125 determines that the weakening magnetic flux control is executed when the rotation speed ω acquired in step S1 is equal to or higher than the switching rotation speed ω1. It should be noted that it may be determined whether or not the weakening magnetic flux control can be executed based on the terminal voltage, terminal current, or the like of the motor 30.

If it is determined that the weakening magnetic flux control is not executed (step S2; No), the mode shifts to the first control mode. In the first control mode, the d-axis current control unit 125 determines the d-axis current command value Iq *'' acquired in step S1 and the d-axis current stored in the ROM according to the above equation (Equation 1). The command value Id * is calculated and determined (step S3). Then, the d-axis current control unit 125 outputs the determined d-axis current command value Id * to the current control unit 126 (step S4). In this way, the motor 30 is driven by the maximum torque control via the inverter 20.

On the other hand, when it is determined to execute the weakening magnetic flux control (step S2; Yes), the d-axis control unit 125 refers to the on / off state of the torque control executing flag stored in the RAM by the correction torque current calculation unit 13f. , It is determined whether or not the torque control by the torque control unit 13 is being executed (step S5).

If the torque control is not being executed (step S5; No), the mode shifts to the second control mode. In the second control mode, the d-axis current control unit 125 is based on the q-axis current command value Iq *'' and the maximum voltage Vam acquired in step S1 and the above equation (Equation 2) stored in the ROM. , The d-axis current command value Id * is calculated and determined (step S6). Then, the d-axis current control unit 125 outputs the determined d-axis current command value Id * to the current control unit 126 (step S4). In this way, the motor 30 is weakened and driven by magnetic flux control via the inverter 20.

If torque control is being executed (step S5; Yes), the mode shifts to the third control mode. In the third control mode, the d-axis current control unit 125 sets the maximum voltage Vam to the IQ-independent function obtained by substituting one IQ of the equation (Equation 2) and the equation (Equation 3) into the other. The value of Id obtained by substituting the target rotation speed ω0 is determined as the target value of the d-axis current command value Id * (step S7). That is, regardless of the q-axis current command value Iq *'' acquired in step S1, as described above, the d-axis current command is the predetermined value I2 corresponding to the intersection point N2 between the current limit curve C3 and the weakening magnetic flux control curve C2. Determine the target value of the value Id *.

Subsequently, the d-axis current control unit 125 determines whether or not the current d-axis current command value Id * has reached the target value determined in step S7 (step S8). If the target value has not been reached (step S8; No), the change amount ΔI (negative change amount) is added to the current d-axis current command value Id * (step S9), and Id * + ΔI is set to the d-axis. It is output to the current control unit 126 as the current command value Id * (step S4).

In the third control mode, the current d-axis current command value Id * continues to be determined as No in step S8 until it reaches the target value determined in step S7 and is determined as Yes in step S8. , The change amount ΔI (negative change amount) continues to be added to the current d-axis current command value Id * (step S9). That is, until the target value is reached, ΔI is added to the current d-axis current command value Id *. In this way, the d-axis current command value Id * is gradually changed to the predetermined value I2 determined in step S7. As a result, it is possible to prevent the d-axis current command value Id * from suddenly changing and causing unstable operation in the motor 30.

The amount of change ΔI added for each process in step S9 does not have to be the same fixed value each time, and changes depending on, for example, the number of times of addition or the magnitude of the current d-axis current command value Id *. It may be a value to be used. The mode of change of the value may be specified by a table or the like stored in the ROM. Further, even when the torque control operation by the torque control unit 13 is stopped during the execution of the third control mode and the third control mode is switched to the second control mode, the d-axis current command value Id * changes abruptly. In order to prevent the motor 30 from causing unstable operation, it is preferable to gradually change the current d-axis current command value Id * to a determined target value.

Each of the above processes is continuously executed while the motor 30 is being driven. This concludes the description of the d-axis current control process.

Subsequently, with reference to FIG. 8 again, an example of shifting to the control mode according to the d-axis current control process will be described. When the driving of the motor 30 is started, first, the maximum torque control as the first control mode is executed. That is, the d-axis current control unit 125 determines the value on the maximum torque control curve C1 corresponding to the acquired q-axis current command value Iq * ″ as the d-axis current command value Id * and outputs the value. Then, when the q-axis current command value Iq *'' rises in response to the increase in the target rotation speed ω0 and the load state is such that the induced voltage exceeds the applied voltage, the weak magnetic flux control as the second control mode is executed. (See the section from point P1 to point P2). That is, the d-axis current control unit 125 determines the value on the weakened magnetic flux control curve C2 corresponding to the acquired q-axis current command value Iq * ″ as the d-axis current command value Id * and outputs the value.

Here, it is assumed that the execution of torque control by the torque control unit 13 is started at the point P2 (step S5; Yes). Then, the mode shifts from the second control mode to the third control mode, the target value of the d-axis current command value Id * is determined to be I2, and the d-axis current command determined immediately before shifting to the third control mode. The value (in this example, the d-axis current command value Id * corresponding to the point P2) gradually changes to the target value I2. As described above, in the third control mode, regardless of the q-axis current command value Iq *'' input to the d-axis current control unit 125, the d-axis current command value is set to Id *, the weakened magnetic flux control curve C2 and the current limit. It is determined to be I2 according to the intersection N2 of the curve C3.

In this control mode transition example, an example of transitioning to the first, second, and third control modes in order has been described, but as can be seen from FIG. 9, Yes, in step S2 during the execution of the first control mode. If Yes is determined in step S5, the first control mode is switched to the third control mode. Further, if the torque control operation by the torque control unit 13 is stopped during the execution of the third control mode, Yes in step S2 and No in step S5, so that the third control mode is switched to the second control mode. ..

As described above, when the torque is controlled by the torque control unit 13, the mode shifts to the third control mode, and the d-axis current command value Id * is set to the predetermined value I2 which is not related to the input q-axis current command value Iq *''. To determine. Therefore, the d-axis current caused by the variation of the q-axis current command value Iq *'' (see FIG. 10A) and the change of the weakening control curve C2 due to the variation of Vam and ω (see FIG. 10B). It is possible to avoid fluctuations in the command value Id *. As a result, the motor 30 and the compressor 40 can be operated stably. Further, since the d-axis current command value Id * is set to a predetermined value I2 corresponding to the intersection N2 where the torque generated during weakening magnetic flux control is maximized under the current limit, the input q-axis current command value Iq *'' Regardless, the weakening magnetic flux effect can be exhibited.

The present invention is not limited to the above embodiments and drawings. Changes (including deletion of components) can be made as appropriate without changing the gist of the present invention. An example of the modification will be described below.

(Modification example)
The d-axis current command value Id * determined in the third control mode is not limited to I2 corresponding to the intersection N2, and may be any value as long as the motor 30 does not saturate the voltage. For example, the d-axis current command value Id * determined in the third control mode may be any value within the range D (| I1 | <D << | Iam |) from I1 to Iam shown in FIG. .. Here, theoretically, when the d-axis current command value Id * is within the range of I1 to I2, the weakening magnetic flux effect may be insufficient depending on the input q-axis current command value Iq *''. .. On the other hand, when the d-axis current command value Id * is within the range of I2 to Iam, the current limit may be exceeded depending on the input q-axis current command value Iq *''. However, when considering the system of the actual machine, it is possible to set the value unevenly distributed in either I1 or Iam from I2 corresponding to the intersection N2. The value may be obtained experimentally.

Further, the torque control by the torque control unit 13 is not limited to the method described in the above embodiment. For example, torque control is executed by a method (called a profile method) in which correction values associated with each rotation position θ of the motor 30 and the compressor 40 are stored in advance as a table according to a load torque fluctuation pattern assumed in advance. You may. In the profile method, a correction value is read from the table according to the acquired rotation position θ, and torque control is performed based on this correction value. When this method is adopted, for example, when the rotation speed ω estimated by the position estimation unit 123 becomes equal to or higher than the threshold value stored in the ROM in advance, the torque control unit 13 should not execute the torque control. Just do it. The threshold value may be predetermined as the rotation speed according to the control limit by the profile method. Further, also in the profile method, the torque control may not be executed when the deviation Δω of the rotation speed does not exceed the above-mentioned allowable value.

In the above embodiment, an example of executing the operation in the third control mode when the torque control by the torque control unit 13 is executed is shown, but the present invention is not limited to this. For example, the d-axis current control unit 125 causes the d-axis current command value Id * to fluctuate based on parameters such as the q-axis current command value Iq *'', the maximum voltage Vam, and the rotation speed ω that can be acquired. , When it is determined that there is a parameter fluctuation amount exceeding a predetermined threshold value or an error value is acquired), the d-axis current command value Id * is determined to the above-mentioned predetermined value by the third control mode. And may be output.

In the above embodiment, the motor control unit 12 controls the motor 30 based on the detection results of the current sensors 35v and 35w, but the current sensors 35v and 35w may be omitted. In this case, the motor control unit 12 may restore the three-phase alternating currents Iu, Iv, and Iw based on the current detection signal Sp1 from the shunt resistance 19 and the PWM switching pattern.

In the above embodiment, the motor 30 is without a rotation angle sensor, but a rotation angle sensor may be provided.

In the above embodiment, the compressor 40 is a slide vane type compressor, but a compressor other than this type may be used, for example, a twin rotary type, a reciprocating type, a swash plate type, a diaphragm type, a twin screw type, or a single compressor. It may be a screw type, a scroll type, a rotary piston type, or the like.

(1) The control unit 10 (an example of the motor control device) of the air conditioner 1 described above has the d-axis current command value Id * and the q-axis current command value Iq determined according to the target rotation speed ω0 of the motor 30. The motor 30 is driven via the inverter 20 according to *''. The d-axis current control unit 125 included in the control unit 10 acquires the determined q-axis current command value Iq *'', and the d-axis current command value Id * based on the acquired q-axis current command value Iq *''. It is provided with a function as a d-axis current control means for determining whether or not the motor 30 is driven by weakening magnetic flux control and as a determination means for determining whether or not the motor 30 is driven by magnetic flux control. Even when the discrimination means determines that the motor 30 is weakened and driven by the magnetic flux control, the d-axis current control means sets the value to a predetermined value regardless of the acquired q-axis current command value Iq *'' under predetermined conditions. The d-axis current command value Id * is determined. This predetermined value is a value at which the motor 30 does not saturate the voltage.
As described above, the fluctuation of the d-axis current command value Id * can be avoided as described above, and as a result, the motor 30 and the compressor 40 can be operated stably.

(2) Further, the control unit 10 corrects the q-axis current command value Iq * in order to suppress the rotation speed fluctuation of the motor 30 (by outputting the torque correction current Iq *', the q-axis current command value. Is Iq *'' (Iq *'' = Iq * + Iq *')) The torque control unit 13 (an example of the correction means) is provided, and the d-axis current control means has the torque control unit 13 as the predetermined condition. When the q-axis current command value Iq * is corrected, the d-axis current command value Id * is determined to be the predetermined value.
In this way, the d-axis current command value Id * is determined to be the predetermined value when torque control is executed, which is highly likely to cause variation in the q-axis current command value Iq *'', so that the d-axis current command value Id * is determined more effectively. Fluctuations in the current command value Id * can be avoided, and as a result, the motor 30 and the compressor 40 can be operated stably.
Further, although the torque control method is not limited as described in the modified example, according to the torque control of the above-described embodiment, even when the load fluctuation pattern during compressor rotation changes due to various factors, the load fluctuation pattern may change. The torque correction current Iq *'is set to a different value in real time accordingly. Therefore, the rotation speed ω of the motor 30 can be stabilized. Further, this can reduce the vibration, noise and the like of the compressor 40. Further, since it is not necessary to store the torque correction current Iq *'in advance according to the innumerable load fluctuation patterns, the torque control unit 13 can be easily designed, and the memory for storing the torque correction current Iq *' The burden is also small.

(3) Further, it is preferable that the predetermined value is a value I2 corresponding to the intersection N2 between the current limiting curve C3 and the weakening magnetic flux control curve C2.
In this way, if the d-axis current command value is a predetermined value I2 corresponding to the intersection N2 where the torque generated during weakening magnetic flux control is maximized under the current limit, the input q-axis current command value Iq *' This is because the weakening magnetic flux effect can be exerted regardless of'.

(4) Further, it is preferable that the d-axis current control means gradually changes the d-axis current command value Id * from the current value to the predetermined value when the d-axis current command value Id * is determined to be the predetermined value.
This is because it is possible to prevent the d-axis current command value Id * from suddenly changing and causing unstable operation in the motor 30.

(5) Further, the air conditioning device 1 is an air conditioner that adjusts the room temperature by using a motor control device, an inverter 20, a motor 30, a compressor 40 driven by the motor 30, and a refrigerant compressed by the compressor 40. A unit 60 is provided.
As described in the modified example, the type of the compressor 40 is not limited, but when the slide vane type, in which the load fluctuation and the rotation speed fluctuation during one rotation are larger than those of other types of compressors, is adopted, the third control mode is used. The method for determining the d-axis current command value and the torque control by the torque control unit 13 are more effective.

1 ... Air conditioner 10 ... Control unit 11 ... Operation command unit 12 ... Motor control unit 124 ... Speed control unit 125 ... d-axis current control unit (example of discriminating means, d-axis current control means)
C1 ... Maximum torque control curve, C2 ... Weak magnetic flux control curve, C3 ... Current limit curve 13 ... Torque control unit (example of correction means)
20 ... Inverter 30 ... Motor 40 ... Compressor 50 ... Power supply 60 ... Air conditioning unit

Claims (3)

A motor control device that drives the motor via an inverter according to the d-axis current command value and the q-axis current command value determined according to the target rotation speed of the motor.
A d-axis current control means that acquires the determined q-axis current command value and determines the d-axis current command value based on the acquired q-axis current command value.
A discriminating means for determining whether or not the motor is driven by weakening magnetic flux control, and
It is provided with a correction means capable of executing torque control for correcting the q-axis current command value in order to suppress the rotation speed fluctuation of the motor.
The discrimination means determines that the motor is driven by the weakening magnetic flux control when the rotation speed of the motor is equal to or higher than a predetermined switching rotation speed.
The correction means executes the torque control when the deviation between the target rotation speed and the rotation speed of the motor exceeds an allowable value regardless of whether or not the discrimination means determines that the motor is driven by weakening magnetic flux control. However, if the deviation does not exceed the permissible value, the torque control is not executed and the torque control is not executed.
The d-axis current control means has acquired the q-axis current command value when the correction means executes the torque control even when the discriminating means determines that the motor is weakened and driven by the magnetic flux control. The d-axis current command value is determined as a predetermined value obtained based on a specific function, which is a value obtained regardless of the above.
The specific function is a function that does not depend on the q-axis current command value and is derived from the function of the current limiting curve and the function of the curve according to the weakening magnetic flux control theory.
The predetermined value is a value at which the motor does not saturate the voltage, and is a value corresponding to the intersection of the current limiting curve and the curve according to the weakening magnetic flux control theory.
Motor control device. When the d-axis current control means determines the d-axis current command value to the predetermined value, the d-axis current control means gradually changes the d-axis current command value from the current value to the predetermined value.
The motor control device according to claim 1 . The motor control device according to claim 1 or 2 ,
It includes the inverter, the motor, a compressor driven by the motor, and an air conditioning unit that adjusts the room temperature by using the refrigerant compressed by the compressor.
Air conditioner.

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