JP2023142968A - Motor control device and motor control method - Google Patents

Abstract

To reduce useless control and achieve proper motor control.SOLUTION: A motor control device according to an embodiment of the present invention comprises a drive unit, a current detection unit, a current approximation unit, and a control unit. The drive unit supplies, to a motor, an AC voltage or an AC current that corresponds to a control command value, and controls the motor. The current detection unit detects a motor current flowing in the motor. The current approximation unit calculates, for each control cycle based on the electrical control cycle of the AC voltage or AC current, the approximate line of the motor current on the basis of a plurality of detection values derived from detection of the motor current, and calculates the approximate value of the motor current on the basis of the approximate line. The control unit calculates the control command value on the basis of the approximate value.SELECTED DRAWING: Figure 2

Description

The present invention relates to a motor control device and a motor control method for controlling a motor.

In recent years, sensorless control has been developed as a method of controlling a motor, in which the motor is controlled without providing a sensor for detecting the rotational position of the motor. This method is feedback control performed by detecting the current flowing through the motor. For example, the current flowing through the motor is detected, and the current and voltage command values for driving the motor are set based on the detected value.

For example, the detected value of the current flowing through the motor may change suddenly due to the influence of disturbances such as sudden noise. When feedback control is performed using values that change rapidly in this way, the command value for driving the motor temporarily changes significantly. The amount of change in the command value is gradually reduced through repeated control, but if the command value oscillates due to disturbances during that time and harmonic components are superimposed on the current waveform, the motor control accuracy decreases. there's a possibility that.

For example, Patent Document 1 describes a method of controlling a motor driven by three-phase alternating current by filtering an estimated value of a motor current (motor current) that is fed back. In this method, the d Axis and q-axis current estimates are calculated and used to control the motor. At this time, the d-axis and q-axis current estimated values are averaged by a first-order lag filter and then fed back. Therefore, changes in the estimated value due to sudden noise or the like are reduced, making it possible to reduce the influence thereof.

Japanese Patent Application Publication No. 2001-145398

Generally, it is known that in averaging processing such as the above-mentioned first-order lag filter, a time delay occurs due to filtering. For example, if the current value fluctuates during this time delay, the current value calculated by the averaging process may deviate from the current actual current value. As a result, the waveform of the current flowing through the motor becomes discontinuous, and the control of the motor may become unstable.

Further, the averaging process using the first-order lag filter needs to be executed every time the motor current is detected. For example, depending on the type of motor, it may be possible to cause the motor to perform a desired operation even if the control accuracy is relatively low. In such a case, performing averaging processing every time a current is detected may actually increase unnecessary control.

In view of the above circumstances, an object of the present invention is to provide a motor control device and a motor control method that can realize appropriate motor control while reducing unnecessary control.

A motor control device according to one embodiment of the present invention includes a drive section, a current detection section, a current approximation section, and a control section.
The drive unit drives the motor by supplying the motor with an alternating voltage or an alternating current according to a control command value.
The current detection section detects a motor current flowing through the motor.
The current approximation unit calculates an approximate line of the motor current based on a plurality of detected values of the motor current for each control period based on the electrical angle period of the AC voltage or the AC current, and An approximate value of the motor current is calculated based on the approximate line.
The control unit calculates the control command value based on the approximate value.

In this motor control device, a motor current is detected and an approximate line thereof is calculated every control cycle. The motor control command value is calculated from the approximate value calculated using this approximate line. Since the control period is set based on the electrical angle period of the AC voltage or AC current supplied to the motor, the frequency of control is low. Further, by using an approximation line, it is possible to calculate a feedback value without being affected by noise or the like. This makes it possible to achieve appropriate motor control while reducing unnecessary control.

The motor current may be a d-axis current and a q-axis current. In this case, the current detection section may detect the d-axis current and the q-axis current. Further, the approximate line may be an approximate line of the d-axis current and an approximate line of the q-axis current. Further, the approximate value may be an approximate value of the d-axis current and an approximate value of the q-axis current. Further, the current approximation unit calculates an approximate line of the d-axis current and an approximate value of the d-axis current based on the detected value of the d-axis current, and based on the detected value of the q-axis current, An approximate line of the q-axis current and an approximate value of the q-axis current may be calculated.

The control unit includes an axis error calculation unit that calculates an axis error of the motor based on the approximate value of the d-axis current and the approximate value of the q-axis current, and a a voltage adjustment unit that adjusts the voltage, an approximate value of the d-axis current, an approximate value of the q-axis current, the adjusted motor voltage, and a speed command value for the motor; It may also include a command value calculation unit that calculates the command value and the command value of the q-axis voltage.

The command value calculation unit sets the command value of the electrical angular velocity to the motor as ωe ^* , the q-axis inductance of the motor as Lq, and the approximate value of the q-axis current as iq', and calculates the d-axis voltage Vd as follows. The command value of the d-axis voltage may be calculated based on the calculation result by calculating according to equation (1) shown below.
Vd=-ωe ^* ×Lq×iq'...(1)

The command value calculation unit calculates the q-axis voltage Vq according to equation (2) shown below, where the motor voltage is V and the d-axis voltage is Vd, and the q-axis voltage is calculated based on the calculation result. A command value may also be calculated.
Vq=sqrt(V ² -Vd ² )...(2)

The approximation line may be an approximation line that approximates a change in the motor current with respect to time. In this case, the current detection section may detect the motor current at a predetermined period. Further, the current approximation unit may calculate the approximate value of the motor current from the detection timing of the latest detected value among the detected values of the motor current used to calculate the approximate line and the approximate line.

The approximate line may be a regression line calculated by a least squares method for the plurality of detected values.

The control period may be set to n times or 1/n times the electrical angle period, where n is an arbitrary positive integer value.

The drive unit may include a PWM generation unit that generates a PWM signal based on the control command value, and a power supply unit that supplies power to the motor based on the PWM signal. In this case, the current detection unit may execute current detection processing for detecting the motor current at least once within the carrier cycle of the PWM signal a predetermined number of times within the control cycle.

The current detection section may detect the motor current using a single shunt resistor.

The motor may be a fan motor that drives a fan installed in an air conditioner.

A motor control method according to one embodiment of the present invention includes driving the motor by supplying an alternating current voltage or alternating current to the motor according to a control command value.
A motor current flowing through the motor is detected.
An approximate line of the motor current is calculated based on a plurality of detected values of the motor current for each control cycle based on the electrical angle period of the AC voltage or the AC current, and the approximate line of the motor current is calculated based on the approximate line. Calculate the approximate value of motor current.
The control command value is calculated based on the approximate value for each control cycle.

According to the present invention, it is possible to realize appropriate motor control while reducing unnecessary control.

1 is a schematic diagram showing a configuration example of an air conditioner equipped with a motor control device according to the present embodiment. FIG. 2 is a block diagram showing a configuration example of a motor control device. FIG. 3 is a schematic diagram showing the definition of coordinate axes of a motor. FIG. 3 is a schematic diagram showing the relationship between an alternating current flowing through a motor and a PWM signal. It is a flowchart which shows an example of operation of a motor control device. It is a graph which shows an example of the approximate line of a d-axis current and a q-axis current. 5 is a time chart showing the timing of motor control. FIG. 2 is a block diagram showing a configuration example of a motor control device as a comparative example.

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

[Air conditioner]
FIG. 1 is a schematic diagram showing a configuration example of an air conditioner equipped with a motor control device according to the present embodiment. As shown in FIG. 1, the air conditioner 100 includes an indoor unit 1 and an outdoor unit 2.
The indoor unit 1 is installed and used in an indoor space within a building. The indoor unit 1 includes an indoor heat exchanger 10 and an indoor blower 11.
The outdoor unit 2 is installed and used outdoors of a building in which the indoor unit 1 is installed, and is connected to the indoor unit 1 via refrigerant piping that circulates refrigerant. The outdoor unit 2 includes an outdoor heat exchanger 20, a compressor 21, a pressure reducer (expansion valve) 22, a flow path switch (four-way valve) 23, a fan 24, a motor 25, and a motor control device 30. has.

For example, during heating operation, high-temperature, high-pressure refrigerant (gas refrigerant) discharged from the compressor 21 of the outdoor unit 2 flows into the indoor heat exchanger 10 of the indoor unit 1 via the flow path switch 23. The high-pressure refrigerant that has exchanged heat with air in the indoor heat exchanger 10 (condenser) is condensed and liquefied. Thereafter, the high-temperature, high-pressure liquid refrigerant is depressurized by passing through the pressure reducer 22 of the outdoor unit 2, and becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant and flows into the outdoor heat exchanger 20. The refrigerant that has exchanged heat with the outside air in the outdoor heat exchanger 20 (evaporator) is vaporized. Thereafter, the low-temperature, low-pressure refrigerant is sucked into the compressor 21 via the flow path switch 23.

For example, during cooling operation, high-temperature, high-pressure refrigerant discharged from the compressor 21 of the outdoor unit 2 flows into the outdoor heat exchanger 20 via the flow path switching device 23. The high-temperature, high-pressure gas refrigerant that has exchanged heat with the outside air in the outdoor heat exchanger 20 (condenser) is condensed and liquefied. Thereafter, the high-temperature, high-pressure liquid refrigerant is depressurized by passing through the pressure reducer 22 of the outdoor unit 2, becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant, and flows into the indoor heat exchanger 10 of the indoor unit 1. In the indoor heat exchanger 10 (evaporator), the refrigerant that has exchanged heat with the air is vaporized. Thereafter, the low-temperature, low-pressure gas refrigerant is sucked into the compressor 21 via the flow path switch 23 .

The fan 24 is, for example, a propeller fan that generates airflow according to the rotation of an impeller, and is fixed to the rotor of the motor 25 and arranged toward an outlet (not shown).
The motor 25 drives a fan 24 mounted on the air conditioner 100. The motor 25 is a permanent magnet synchronous motor (PM synchronous motor) that uses a permanent magnet in a rotor and has windings arranged in a stator. The motor 25 is provided with three-phase windings of U-phase, V-phase, and W-phase, and an alternating current voltage output from the drive circuit 31 is applied to the windings of each phase. The specific configuration of the motor 25 is not limited, and any type of motor may be used.

As the motor 25 rotates the fan 24, outdoor air is blown to the outdoor heat exchanger 20. Outdoor air passes through the outdoor heat exchanger 20 and exchanges heat with the refrigerant. The heat-exchanged cool air or warm air flow is blown out from the outdoor unit 2. The flow rate of the airflow passing through the outdoor heat exchanger 20 is adjusted according to the rotation speed of the fan 24, that is, the rotation speed of the motor 25.
In this embodiment, the motor 25 corresponds to a fan motor.

The motor control device 30 is a device that rotates the motor 25 based on electric power supplied from the power source 3 and controls the rotational operation of the motor 25.
In this embodiment, the motor control device 30 performs vector control of the motor 25. In vector control, the current flowing through the windings provided on the stator of the motor 25 is divided into a current component (d-axis current) that generates magnetic flux in the rotor of the motor 25 and a current component (q-axis current) that generates torque in the rotor. (axis current) and each current component is controlled independently. In this embodiment, a case will be described in which the motor control device 30 performs vector control of a fan motor as the motor 25, but it is also possible to apply the present technology to vector control of other motors.
As shown in FIG. 1, the motor control device 30 includes a drive circuit 31, an arithmetic circuit 32, a current detection circuit 33, and a DC detection circuit 34.

The drive circuit 31 corresponds to a drive section that drives the motor 25 by supplying the motor 25 with an alternating voltage or an alternating current according to a control command value. The drive circuit 31 outputs the DC voltage supplied from the power supply 3 as a three-phase AC voltage and applies it to each phase of the motor 25, and supplies an AC current corresponding to the AC voltage to each phase.
In this embodiment, the drive circuit 31 corresponds to a drive section.

The control command value is a command value of a parameter for controlling the motor 25. For example, command values regarding voltage values to be supplied to the U-phase, V-phase, and W-phase of the motor 25 are input to the drive circuit 31 as control command values. The drive circuit 31 generates an AC voltage to be applied to each phase based on the voltage indicated by the control command value. By applying this AC voltage to the windings of each phase of the motor 25, an AC current corresponding to the AC voltage flows through the windings of each phase, and the motor 25 is driven.
Further, in the drive circuit 31, the voltage applied to the motor 25 is controlled using a pulse width modulation (PWM) signal. Further, the control command value is a duty command value that specifies the width (duty) of the PWM signal.

The arithmetic circuit 32 is a circuit that performs arithmetic processing necessary for controlling the motor 25. The arithmetic circuit 32 is configured using a computer equipped with a CPU (Central Processing Unit), memory, and the like. The arithmetic circuit 32 corresponds to a control section that generates a control command value.
The arithmetic circuit 32 receives the detected values of the current detection circuit 33 and the DC detection circuit 34, as well as commands and set values transmitted from the indoor unit 1 of the air conditioner 100. In response to these inputs, a control command value for vector control of the motor 25 is calculated. Here, a duty command value representing a voltage value to be supplied to each phase of the motor 25 is calculated.

The current detection circuit 33 is a circuit that detects the current flowing through the three-phase windings provided in the motor 25. The current detection circuit 33 is configured using, for example, a current sensor, an amplifier, an AD converter, etc. (see FIG. 2).
In this embodiment, among the currents flowing through the three-phase windings of the motor 25, the currents flowing through the two-phase windings are detected. Note that it is possible to calculate the current flowing through the remaining windings from this detection result. In this embodiment, the current detection circuit 33 constitutes a current detection section together with a three-phase to two-phase converter 36, which will be described later.

The DC detection circuit 34 is a circuit that detects the voltage value of the power supply 3. That is, the DC detection circuit 34 detects the DC voltage supplied to the motor 25. The detection result of the DC detection circuit 34 is output to the arithmetic circuit 32.
For example, the voltage value of the power source 3 may change due to changes in the voltage of an external power source supplied to the power source 3, load changes, etc. In such a case, the arithmetic circuit 32 adjusts the control command value using the detection result of the DC detection circuit 34. This allows the motor 25 to be driven stably even if the voltage of the power source 3 changes.

[Motor control device]
FIG. 2 is a block diagram showing a configuration example of the motor control device 30. As shown in FIG. FIG. 3 is a schematic diagram showing the definition of the coordinate axes of the motor 25. Below, the detailed configuration of each part of the motor control device 30 will be explained with reference to FIGS. 2 and 3.

First, the coordinate axes used in the following explanation will be explained. FIG. 3 schematically shows the permanent magnet 5 provided on the rotor of the motor 25. As shown in FIG. The permanent magnet 5 is arranged perpendicular to the rotation axis (Z-axis) of the motor 25. Here, the direction of the N pole of the permanent magnet 5 (the N pole side is in the + direction) is defined as the d-axis, and the axis perpendicular to the d-axis is defined as the q-axis. Note that the d-axis current that generates magnetic flux in the d-axis direction becomes a current component that generates magnetic flux in the rotor. Further, the q-axis current that generates magnetic flux in the q-axis direction becomes a current component that generates torque in the rotor of the motor 25.
Further, it is assumed that θe is the estimated position of the rotor expressed in electrical angle (estimated angle with respect to the U axis), and ωe is the estimated angular velocity of the rotor expressed in electrical angle. Further, it is assumed that the Z-axis is a virtual axis orthogonal to both the d-axis and the q-axis.

As shown in FIG. 2, the motor control device 30 includes the above-described drive circuit 31, arithmetic circuit 32, and current detection circuit 33. The arithmetic circuit 32 also includes, as functional blocks, a three-phase to two-phase converter 36, an approximation processing unit 37, an axis error calculation processing unit 38, an axis error control unit 39, an integrator 40, an angular velocity converter 41, and a voltage command generation unit. It has a section 42. Each functional block of the arithmetic circuit 32 may be configured using a dedicated IC or the like.
Note that in FIG. 2, illustration of the DC detection circuit 34 is omitted.

The drive circuit 31 uses voltage command vectors (Vu ^* , Vv ^* , Vw ^* ) in a fixed coordinate system (UVW coordinate system), that is, U-phase voltage command value Vu ^* , V-phase voltage command value Vv ^* , and W-phase voltage command value. Vw ^* is received from the voltage command generation unit 42 (two-phase to three-phase converter 55), and a DC voltage Vdc for driving the motor 25 is received from the power supply 3. In this embodiment, the U-phase voltage command value Vu ^* , the V-phase voltage command value Vv ^* , and the W-phase voltage command value Vw ^* correspond to control command values.
Further, ^the drive circuit 31 ^outputs three-phase AC voltages to U-phase, V ^- phase, The motor 25 is driven by supplying it to the motor 25 through the windings of each phase of the W phase.
Specifically, drive circuit 31 includes a PWM modulator 45 and an intelligent power module (IPM) 46.

The PWM modulator 45 converts the control command values (U-phase voltage command value Vu ^* , V-phase voltage command value Vv ^* , W-phase voltage command value Vw ^* ) received from the voltage command generation unit 42 into PWM signals, respectively. Supplied to IPM46. For example, a PWM signal having a pulse width set according to each command value is generated. In this embodiment, the PWM modulator 45 corresponds to a PWM generation section that generates a PWM signal based on a control command value.

The IPM 46 has a plurality of switching elements, receives a PWM signal from the PWM modulator 45, performs a power conversion operation by switching the plurality of switching elements at a predetermined timing according to the PWM signal, and converts the generated three-phase The motor 25 is driven by supplying an alternating current voltage to the motor 25. In this embodiment, the IPM 46 corresponds to a power supply section that supplies power to the motor 25 based on the PWM signal.

The current detection circuit 33 detects (picks up) current values of at least two phase currents. In the example shown in FIG. 2, a U-phase current iu and a W-phase current iw flowing through the U-phase and W-phase windings are detected. Note that the configuration is not limited to this, and for example, there may be a configuration in which the U-phase current iu and the V-phase current iv are detected, or a configuration in which the V-phase current iv and the W-phase current iw are detected. Alternatively, all of the U-phase current iu, V-phase current iv, and W-phase current iw may be detected.

Current detection circuit 33 includes a current sensor 47u, a current sensor 47w, and an AD converter 48.
Current sensor 47u detects U-phase current iu. Current sensor 47w detects W-phase current iw. The detection results of each current sensor 47u and 47w are output to the AD converter 48. As the current sensor, a CT (Current Transformer), a Hall element, or the like is used.
The AD converter 48 performs AD conversion on the current values output from the current sensors 47u and 47w, and outputs the result as a signal that can be controlled by a computer.
Note that the specific configuration of the current detection circuit 33 is not limited, and other current detection methods may be used, such as using a shunt resistor, for example.

Next, each functional block of the arithmetic circuit 32 will be explained.
The three-phase to two-phase converter (u, v, w/d-q) 36 converts two current values (U-phase current iu and W-phase current iu, V-phase current iv, and W-phase current iw) into The phase current iw) is received from the AD converter 48 of the current detection circuit 33, and the current values of the remaining phases (V-phase current iv) are calculated based on these current values. Furthermore, the three-phase to two-phase converter 36 receives the estimated position of the rotor (electrical rotation angle θe) from the integrator 40, and converts the current vector (iu, iv, iw) in the fixed coordinate system (UVW coordinate system) into the rotating coordinates. Convert to current vector (id, iq) in the system (dq coordinate system). The rotating coordinate system (dq coordinate system) has a d-axis and a q-axis that intersect with each other as shown in FIG. Below, the current vector (id, iq) is simply described as d-axis current id and q-axis current iq.

In this embodiment, the motor current flowing through the motor 25 is detected by the current detection circuit 33 and the three-phase to two-phase converter 36. Here, the motor current is a drive current that drives the motor 25.
For example, the current flowing through the three-phase windings (U-phase current iu, W-phase current iw detected by the current detection circuit 33, V-phase current iv calculated by the 3-phase to 2-phase converter) is equal to the motor current. This is an example. Furthermore, the d-axis current id and the q-axis current iq calculated by converting the U-phase current iu, V-phase current iv, and W-phase current iw are also motor currents.

Furthermore, since the d-axis current id and the q-axis current iq are converted from the detected values of the U-phase current iu, V-phase current iv, and W-phase current iw, they can be regarded as detected values.
Therefore, it can be said that the current detection circuit 33 and the three-phase to two-phase converter 36 detect the d-axis current id and the q-axis current iq as motor currents. In this embodiment, the current detection circuit 33 and the three-phase to two-phase converter 36 realize a current detection section.
The three-phase to two-phase converter 36 outputs the d-axis current id and the q-axis current iq to the approximation processing section 37.

The approximation processing unit 37 calculates an approximation line of the motor current based on a plurality of detected values of the motor current for each control period T based on the electrical angle period Te, and calculates an approximation line of the motor current based on the approximation line. Calculate approximate value. In this embodiment, the approximation processing section 37 functions as a current approximation section.

Here, the approximate line is a line that approximately represents a current component (change in motor current) that changes with the passage of time (phase). The approximate line may be a straight line or a curved line. For example, a regression line is used as the approximate line. Further, for example, an exponential approximate curve, a power approximate curve, a logarithmic approximate curve, etc. may be used. In addition, an approximation line using an arbitrary function may be used.
These approximate lines may be selected appropriately depending on, for example, the change tendency of the current component, the data interval used for calculating the approximate lines, and the like. In this embodiment, as will be described later, a regression line calculated by the least squares method is used.

The electrical angle period Te is the period of the alternating current voltage or alternating current supplied to the motor 25, and is, for example, the time for one rotation of the electrical rotation angle θe. The electrical angular period Te changes depending on the rotational speed of the motor 25 and the like.
The control cycle T is a cycle in which feedback control is performed on the motor 25. This can also be said to be the cycle for updating the feedback parameters used to calculate the control command value for the motor 25. For example, an approximate value of the motor current or a value calculated from the approximate value is the feedback parameter.
In this embodiment, an approximate line and an approximate value of the motor current are calculated for each control cycle T. The control period T is appropriately set to a period that is identical to the electrical angular period Te, or a period that is longer (or shorter) than the electrical angular period Te, with the electrical angular period Te as a reference.

Note that the electrical angular period Te is sufficiently longer than the carrier period Tc of the PWM signal (see FIG. 4).
For example, when the carrier frequency is 20 kHz, the motor rotation speed is 900 rpm, and the number of pole pairs is 4, Te=(60/(4×900)) and Tc=(1/20k). In this case, Te/Tc=333.33, and Te is approximately 300 times as large as Tc. Similarly, if the motor rotation speed is 200 rpm, Te will be approximately 1500 times as large as Tc.
Therefore, the control period T set based on the electrical angular period Te is also sufficiently longer than the carrier period Tc, and it can be said that the frequency of performing feedback control on the motor 25 is sufficiently lower than the frequency of generating PWM signals. .

The approximation processing unit 37 calculates an approximate line and an approximate value of the motor current for the motor current (d-axis current id and q-axis current iq) received from the 3-phase to 2-phase converter 36.
For example, the approximation processing unit 37 sequentially records the d-axis current id received from the 3-phase to 2-phase converter 36 as d-axis current data, calculates an approximation line λd that is an approximation line of the d-axis current id, and A d-axis current approximate value id', which is an approximate value of the d-axis current id, is calculated from λd.
Further, the approximation processing unit 37 sequentially records the q-axis current iq received from the 3-phase to 2-phase converter 36 as q-axis current data, calculates an approximation line λq that is an approximation line of the q-axis current iq, and converts the approximation line A q-axis current approximate value iq', which is an approximate value of the q-axis current iq, is calculated from λq.

Thus, in this embodiment, the approximate lines calculated by the approximation processing unit 37 are the approximate line λd of the d-axis current id and the approximate line λq of the q-axis current. Further, the approximate values calculated by the approximation processing unit 37 are a d-axis current approximate value id' and a q-axis current approximate value iq'.

Further, the approximation processing unit 37 receives the d-axis voltage command value Vd ^* from the voltage command generation unit 42, and calculates the d-axis voltage command approximate value Vd ^* ', which is an approximate value of the d-axis voltage command value Vd ^* . Further, the approximation processing unit 37 receives the q-axis voltage command value Vq ^* from the voltage command generation unit 42, and calculates the q-axis voltage command approximate value Vq ^* ', which is an approximate value of the q-axis voltage command value Vq ^* . The d-axis voltage command approximate value Vd ^* ' and the q-axis voltage command approximate value Vq ^* ' are approximate lines for the d-axis voltage command value Vd ^* and the d-axis voltage command value Vd ^* used within the control period T, for example. Calculated using

The axis error calculation processing unit 38 calculates the axis error Δθ of the motor 25 based on the d-axis current approximate value id' and the q-axis current approximate value iq'. Specifically, the axis error calculation processing unit 38 calculates the d-axis current approximate value id', the q-axis current approximate value iq', the d-axis voltage command approximate value Vd ^* ', and the q-axis voltage command approximate value Vq ^* '. The electric angular velocity command value ωe * is received from the approximation processing unit 37 and the electrical angular velocity command value ωe ^* is received from the voltage command generation unit 42 , and the d-axis current approximate value id', the q-axis current approximate value iq', the d-axis voltage command approximate value Vd ^* ', the q-axis An axis error Δθ, which is a difference between the actual position and the estimated position of the rotor, is determined according to the voltage command approximate value Vq ^* ′ and the electrical angular velocity command value ωe ^* , and is output to the axis error control unit 39. In this embodiment, the axis error calculation processing section 38 corresponds to an axis error calculation section.

The axis error Δθ represents the error in the actual rotor position relative to the assumed rotor position on the control axis. Therefore, it can be said that the axis error control unit 39 is a position estimation unit that estimates the position of the rotor by calculating the axis error Δθ.
An algorithm using an observer or the like is typically used to calculate the axis error Δθ. In addition, any algorithm capable of calculating the axis error Δθ may be used.

The axis error control unit 39 receives the axis error Δθ from the axis error calculation processing unit 38, calculates a motor voltage V that converges this error to 0 based on the axis error Δθ, and outputs it to the voltage command generation unit 42. . That is, the axis error control unit 39 adjusts the motor voltage V so that the axis error Δθ converges to zero.
Here, the motor voltage V is a voltage value representing the magnitude of the voltage vector (d-axis voltage Vd and q-axis voltage Vq) supplied to the motor 25. In this embodiment, the axis error control section 39 corresponds to a voltage adjustment section.
The axis error control section 39 is, for example, a PI controller configured using an integrator and a proportional device. Note that the present invention is not limited to this, and for example, in order to avoid steep control, an I controller configured using an integrator may be used as the axis error control section 39.

The integrator 40 calculates the electrical rotation angle θe as the estimated position of the rotor in the fixed coordinate system (UVW coordinate system) by time-integrating the electrical angular velocity command value ωe ^* output from the angular velocity converter 41, It is output to the phase-to-two-phase converter 36 and the two-to-three-phase converter 55 of the voltage command generation section 42, respectively.

The angular velocity converter 41 converts the mechanical angular velocity of the motor 25 into an electrical angular velocity. Specifically, the angular velocity converter 41 receives a mechanical angular velocity command value ωm ^* from the outside, and converts the mechanical angular velocity command value ωm ^* into an electrical angular velocity command value ^ωe * using the number of pole pairs according to the configuration of the motor 25. . The electrical angular velocity command value ωe ^* is output to the voltage command generation section 42 , the approximation processing section 37 , the axis error calculation processing section 38 , and the integrator 40 .

The voltage command generation unit 42 receives the d-axis current approximate value id' and the q-axis current approximate value iq' from the approximation processing unit 37, receives the motor voltage V from the axis error control unit 39, and externally outputs the mechanical angular velocity command value ωm ^* . ⁽ for example, a higher-level controller (not shown)), the control command value (U-phase voltage A command value Vu ^* , a V-phase voltage command value Vv ^* , a W-phase voltage command value Vw ^* ) are generated.

Specifically, the voltage command generation unit 42 generates d based on the d-axis current approximate value id', the q-axis current approximate value iq', the adjusted motor voltage V, and the mechanical angular velocity command value ωm ^* . Axis voltage command value Vd ^* and q-axis voltage command value Vq ^* are calculated. The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* calculated here are converted into a U-phase voltage command value Vu ^* , a V-phase voltage command value Vv ^* , and a W-phase voltage command value Vw ^* .
In this embodiment, the mechanical angular velocity command value ωm ^* corresponds to the speed command value for the motor. Further, the voltage command generation section 42 corresponds to a command value calculation section.

As shown in FIG. 2, the voltage command generation unit 42 includes a d-axis voltage calculator 50, a q-axis voltage calculator 51, a deinterference controller 52, a subtracter 53, an adder 54, and a 2-phase to 3-phase converter. A container (dq/u, v, w) 55 is provided.

The d-axis voltage calculator 50 receives the electrical angular velocity command value ωe ^* from the angular velocity converter 41, receives the q-axis current approximate value iq' from the approximation processing unit 37, and calculates the electrical angular velocity command value ωe ^* and the q-axis current approximate value iq. ', and outputs the d-axis voltage Vd to the q-axis voltage calculator 51 and the subtracter 53. This process is a process of calculating the d-axis voltage (Vd) that realizes the current speed command value (ωe ^* ) from the approximate value (iq') of the q-axis current.

The q-axis voltage calculator 51 receives the motor voltage V from the axis error control unit 39 and the d-axis voltage Vd from the d-axis voltage calculator 50, and calculates the q-axis voltage Vq according to the motor voltage V and the d-axis voltage Vd. is calculated, and the q-axis voltage Vq is output to the adder 54. This process is a process of calculating the q-axis voltage (Vq) that realizes both the current speed command value (ωe ^* ) and the motor voltage V that makes the axis error Δθ zero.

The process of calculating the d-axis voltage Vd and the q-axis voltage Vq by the d-axis voltage calculator 50 and the q-axis voltage calculator 51 is a process of substituting parameters input to each calculator into a predetermined function. This point will be explained in detail later.

The deinterference controller 52 deactivates the q-axis voltage Vq and the d-axis voltage Vd. Specifically, the deinterference controller 52 receives the d-axis current approximate value id' from the approximation processing unit 37, and performs a process for deinterfering the q-axis voltage Vq according to the d-axis current approximate value id'. A non-interference correction value Vqa is determined, and the non-interference correction value Vqa is output to the adder 54. Further, the deinterference controller 52 receives the q-axis current approximate value iq' from the approximation processing unit 37, and performs a deinterference process for decoupling the d-axis voltage Vd according to the q-axis current approximate value iq'. A correction value Vda is determined, and the non-interference correction value Vda is output to the subtracter 53.

The subtracter 53 receives the d-axis voltage Vd from the d-axis voltage calculator 50, receives the de-interference correction value Vda from the de-interference controller 52, and subtracts the de-interference correction value Vda from the d-axis voltage Vd. The subtraction result is output to the two-phase to three-phase converter 55 and the approximation processing section 37 as the d-axis voltage command value Vd ^* after decoupling.

The adder 54 receives the q-axis voltage Vq from the q-axis voltage calculator 51, receives the de-interference correction value Vqa from the de-interference controller 52, and adds the q-axis voltage Vq and the de-interference correction value Vqa. , and outputs the addition result to the two-phase to three-phase converter 55 and the approximation processing unit 37 as the q-axis voltage command value Vq ^* after decoupling.

The 2-phase to 3-phase converter (d-q/u, v, w) 55 receives the d-axis voltage command value Vd ^* from the subtracter 53, receives the q-axis voltage command value Vq ^* from the adder 54, and converts the electricity The rotation angle θe is received from the integrator 40, and the voltage command vectors (Vd ^* , Vq ^* ) in the rotational coordinate system (dq coordinate system) are converted into a fixed coordinate system (UVW coordinate system) according to the electrical rotation angle θe, for example. It is converted into voltage command vectors (Vu ^* , Vv ^* , Vw ^* ) at.

As described above, in this embodiment, based on the approximate values (d-axis current approximate value id' and q-axis current approximate value iq') calculated by the approximation processing unit 37, the axis error calculation processing unit 38 calculates the axis error. The control unit 39 and the voltage command generation unit 42 calculate voltage command vectors (Vu ^* , Vv ^* , Vw ^* ), which are control command values. That is, the axis error calculation processing section 38, the axis error control section 39, and the voltage command generation section 42 calculate the control command value based on the approximate value. This approximate value is updated at the control period T.
In this embodiment, the control section is realized by the axis error calculation processing section 38, the axis error control section 39, and the voltage command generation section 42 working together.

FIG. 4 is a schematic diagram showing the relationship between the alternating current flowing through the motor 25 and the PWM signal. In the upper part of FIG. 4, a schematic graph showing the currents (U-phase current iu, V-phase current iv, W-phase current iw) flowing through the U-phase, V-phase, and W-phase windings of the motor 25 is shown. There is. Also, on the lower side of FIG. 4 is a schematic graph showing U-phase, V-phase, and W-phase PWM signals (PWM signal 6u, PWM signal 6v, PWM signal 6w) during a part of the period of the upper graph. is illustrated.

As shown in the upper graph of FIG. 4, the U-phase current iu, the V-phase current iv, and the W-phase current iw are sinusoidal alternating currents that oscillate with an electrical angular period Te. The phases of the currents iu, iv, and iw of each phase are shifted at intervals of 120°. Note that the electrical angular period Te becomes shorter as the rotational speed of the motor 25 becomes higher.
The voltage applied to the winding is set by the duty command value of the PWM signal output at the carrier frequency so that such an alternating current waveform is realized.

The lower graph in FIG. 4 shows pulse waveforms of the PWM signal 6u, PWM signal 6v, and PWM signal 6w that vary with the carrier period Tc. In each PWM signal, one carrier period Tc includes one pulse.
The carrier period Tc of the PWM signal is generally a constant, and is set to be sufficiently smaller than the electrical angle period Te. Therefore, for example, a large number of PWM signals are generated during one electrical angular period Te.

In this embodiment, a control period T for calculating an approximate value and performing feedback control is set with the electrical angle period Te as a reference. Therefore, the time interval used for feedback by calculating approximate values from the detected values of the U-phase current iu, V-phase current iv, and W-phase current iw is sufficiently longer than, for example, the carrier period Tc of the PWM signal.
This makes it possible to significantly reduce the frequency of feedback control, for example, compared to the case where feedback control is performed at a period several times the carrier period Tc (for example, 4 to 5 times the carrier period Tc). Furthermore, since the number of times of control is reduced, it is possible to avoid unnecessary control such as feeding back sudden current fluctuations, for example.

For example, the control period T is set to be n times the electrical angle period Te, where n is an arbitrary positive integer value (T=n×Te). In this case, for example, even if n is set to 1, the frequency of feedback control can be made sufficiently low. Further, for example, the control period T may be set to 1/n times the electrical angle period Te, where n is an arbitrary positive integer value (T=Te/n). In this case, since feedback control is performed n times during one electrical angular period T, it is possible to improve the control accuracy of the motor.

Note that the control cycle T is a cycle in which the d-axis current approximate value id' and the q-axis current approximate value iq' are updated. For example, after each approximation value is updated until the next update is executed, the latest approximation value is used to set the control command value (Vu ^* , Vv ^* , Vw ^* ) are calculated.
For example, the electrical rotation angle θe is input from the integrator 40 to the two-phase to three-phase converter 55 shown in FIG. The electrical rotation angle θe is an angle that rotates with an electrical angle period Te, and is updated, for example, with a carrier period Tc. Therefore, the two-phase to three-phase converter 55 outputs control command values (Vu ^* , Vv ^* , Vw ^* ) according to the electrical rotation angle θe at each carrier cycle Tc. Thereby, it is possible to calculate the control command value for creating a sinusoidal alternating current using the carrier period Tc.

[Operation of motor control device]
FIG. 5 is a flowchart showing an example of the operation of the motor control device 30.
Below, the basic operation of the motor control device 30 will be explained with reference to FIG.
First, the motor 25 is driven based on the control command value (step 101). For example, a control command value generated using the most recent approximate values (d-axis current approximate value id' and q-axis current approximate value iq') is input to the PWM modulator 45 of the drive circuit 31. Here, the control command values are a U-phase voltage command value Vu ^* , a V-phase voltage command value Vv ^* , and a W-phase voltage command value Vw ^* .

Further, the PWM modulator 45 generates PWM signals 6u, 6v, and 6w according to each control command value and inputs them to the IPM 46.
The IPM 46 supplies voltages corresponding to the PWM signals 6u, 6v, and 6w to the U-phase, V-phase, and W-phase windings of the motor 25, thereby driving the motor.

Next, it is determined whether it is the detection timing to detect the motor current (step 102). Here, the process of detecting the motor current (current detection process) is to detect the U-phase current iu, V-phase current iv, and W-phase current iw, and convert the detection results to obtain the d-axis current id and the q-axis current. This is a process of detecting iq.

The current detection process is, for example, a process of detecting the motor current at least once within the carrier period Tc. Specifically, two of the U-phase, V-phase, and W-phase currents are detected at least once within one carrier period Tc. Thereby, the U-phase current iu, V-phase current iv, and W-phase current iw, and the d-axis current id and q-axis current iq in the carrier period Tc can be detected. In step 102, the timing for executing such current detection processing is determined.

In this embodiment, the current detection process is executed a predetermined number of times within the control period T. The number of current detection processes is, for example, the number of data points used to calculate the approximate line. For example, if there are too many data points, the approximation will follow the sudden load. On the other hand, if the number of data points is too small, it becomes difficult to properly calculate the approximate line. Therefore, the number of times of current detection processing is set so that the approximate line can be calculated appropriately.
Further, in this embodiment, the current detection process is executed at a predetermined detection cycle Tm. The detection period Tm is an interval between detection timings, and is appropriately set so that current detection processing can be performed a predetermined number of times within the control period T. For example, when current detection is performed M times within the control period T, Tm=T/M is set. For example, when current detection is performed once within one carrier cycle Tc, Tm=Tc is set. In this embodiment, the detection period Tm corresponds to a predetermined period.
Note that the current detection process does not necessarily need to be executed periodically.

As shown in FIG. 5, if it is determined that the detection timing is not reached (No in step 102), step 105, which will be described later, is executed.
If it is determined that it is the detection timing (Yes in step 102), the U-phase current iu, V-phase current iv, and W-phase current iw of the motor 25 are detected as current detection processing (step 103).

In step 103, the current detection circuit 33 detects two phase currents among the U-phase current iu, V-phase current iv, and W-phase current iw during one carrier period ΔT, and It is input to a two-phase converter 36. Further, the current values of the remaining phases are calculated as appropriate from the current values of the two phases in the three-phase to two-phase converter 36. This makes it possible to detect the U-phase current iu, the V-phase current iv, and the W-phase current iw at substantially the same timing.

Next, the three-phase to two-phase converter 36 converts the U-phase current iu, V-phase current iv, and W-phase current iw into a d-axis current id and a q-axis current iq (step 104). Here, dq conversion is performed on three-phase currents (iu, iv, iw), and d-axis current id and q-axis current iq are calculated. The d-axis current id is recorded as d-axis current data, and the d-axis current iq is recorded as q-axis current data.

Such current detection processing (steps 103 and 104) is executed at the detection period Tm. That is, the d-axis current id and the q-axis current iq are detected at the detection period Tm.
Therefore, the d-axis current data is data that records the detected values of a plurality of d-axis currents id detected at the detection period Tm, and the q-axis current data is the data that records the detected values of a plurality of d-axis currents iq detected at the detection period Tm. The data records the detected values.

Next, it is determined whether it is the control timing to perform feedback control (step 105). For example, the elapsed time since the previous feedback control is counted, and it is determined whether the elapsed time is equal to or longer than the control period T. For example, if the elapsed time is less than T, it is determined that it is not the control timing (No in step 105), and step 108, which will be described later, is executed.
Further, if the elapsed time is T or more, it is determined that the control timing has come (Yes in step 105). In this case, a regression line λd of the d-axis current id and a regression line λq of the q-axis current iq are calculated using the d-axis current data and the q-axis current data (step 106).

FIG. 6 is a graph showing an example of an approximate line of the d-axis current id and the q-axis current iq.
FIG. 6 schematically shows a graph of data points of a plurality of detected current values and an approximate line calculated from the detected current values. When the detected current value is the detected value of the d-axis current id, the approximate line becomes the approximate line λd of the d-axis current id. Further, when the detected current value is the detected value of the q-axis current iq, the approximate line becomes the approximate line λq of the q-axis current iq.
The data points shown in FIG. 6 are plots of d-axis current data (or q-axis current data). The horizontal axis x of the graph is the rotor position ωe×t of the motor 25 at time t. The vertical axis y of the graph is the value of the d-axis current id (or the q-axis current iq).

The approximate line shown in FIG. 6 is calculated from each data point of the detected current value. Here, there is a tendency for the detected current value to increase over time. The approximation line approximates such a change in the detected current value (change in motor current). That is, the approximate line is a line that approximately represents the change tendency of the detected current value.
Of course, the changing trends of the d-axis current id and the q-axis current iq are different from each other. Therefore, the approximation line λd of the d-axis current id becomes an approximation line that approximates the change in the d-axis current id with respect to time. Further, the approximate line λq of the q-axis current iq is an approximate line that approximates the change in the q-axis current iq with respect to time.

In this embodiment, an approximation line that is a straight line is used in a coordinate system in which the vertical axis is the d-axis current id (or the q-axis current iq) and the horizontal axis is the rotor position (phase).
Specifically, as the approximation line, a regression line calculated by the least squares method for a plurality of detected values for the d-axis current id and the q-axis current iq is used. By using such a regression line, it becomes possible to accurately and stably calculate the d-axis current approximate value id' and the q-axis current approximate value iq'.
Hereinafter, the approximate line λd of the d-axis current id will be referred to as a regression line λd, and the approximate line λq of the q-axis current iq will be referred to as a regression line λq.

Specifically, the approximation processing unit 37 calculates regression lines λd and λq from a plurality of current detection values detected during the control period T. Therefore, the interval range of the data used to calculate the regression lines λd and λq is set to a range corresponding to the control period T.
Here, the control period T is set to the electrical angle period Te. In this case, the horizontal axis x of the graph corresponds to the phase of the motor in the electrical angle period Te (that is, the electrical rotation angle θe at time t). Further, the value of x at time t=Te at the end of the data interval range is 2π (=ωe×Te). Note that the data interval range does not necessarily have to match the electrical angle period Te and can be set arbitrarily.

In the example shown in FIG. 6, the current detection process is performed an arbitrary number of times during one electrical angle period Te with reference to the electrical angle period Te. As a result, an arbitrary number of data points are generated for each of the d-axis current id and the q-axis current iq. Regression lines λd and λq are calculated by applying the least squares method to these data points.

For example, when the d-axis current id (or the q-axis current iq) is written as y and the rotor position ωe×t is written as x, the equation of the regression line becomes y=ax+b.
Here, a is the slope of the regression line, and b is the intercept of the regression line. The process of calculating the regression line is the process of calculating the slope a and the intercept b.
The approximation processing unit 37 calculates the slope a and the intercept b for the d-axis current id as a process for calculating the regression line λd. Furthermore, as a process for calculating the regression line λq, the slope a and the intercept b of the q-axis current iq are calculated.
Note that any calculation formula or algorithm using the least squares method may be used to calculate the slope a and the intercept b.

Next, the approximation processing unit 37 calculates the d-axis current approximate value id' and the q-axis current approximate value iq' from the regression lines λd and λq (step 107).
The d-axis current approximate value id' is calculated by setting the x value of the regression line λd. Further, the q-axis current approximate value iq' is calculated by setting the x value of the regression line λq.

For example, as shown in FIG. 6, the actual detected values are not necessarily stable and may vary. Furthermore, the detected value may change instantaneously due to the influence of noise or the like. For this reason, for example, if the detected value is used as it is for feedback control, control that abruptly changes the current value is executed, which may cause a hunting phenomenon or the like.

Therefore, in this embodiment, an approximate value calculated from the regression line is used for feedback control instead of the actual detected value. This stabilizes the value used for feedback, making it possible to avoid hunting phenomena and the like.
In this way, the process of calculating an approximate value from the regression line can be said to be a current averaging process for removing harmonic components of motor control.

In this embodiment, the value of the regression line at the end of the interval range (here, the control period T) of the data used to calculate the regression line is used as the approximate value. Therefore, an approximate value (y=a×2π+b) is calculated by substituting x=2π (where 0≦x≦2π) into each regression line. This is a process of calculating an approximate value at the detection timing of the latest detected value among the detected values. In FIG. 6, points on the regression line at x=2π (t=Te) are schematically illustrated by white circles. The current value indicated by this white circle point is used as an approximate value for feedback control.

In step 107, the above-mentioned processing is executed for each of the d-axis current id and the q-axis current iq.
For example, the d-axis current approximate value id' is calculated from the detection timing of the latest detected value among the detected values of the d-axis current id used to calculate the regression line λd and the regression line λd. That is, the value obtained by substituting x=2π for λd becomes id'.
Further, for example, a q-axis current approximate value iq' is calculated from the regression line λq and the detection timing of the latest detected value among the detected values of the q-axis current iq used to calculate the regression line λq. That is, the value obtained by substituting x=2π for λq becomes iq'.
This makes it possible to feed back the latest values represented by each of the approximation lines λd and λq as the approximation values id' and iq', making it possible to appropriately calculate the control command value.

Note that setting the value of x corresponds to, for example, setting the timing for reading the current used for control. x can be set arbitrarily; for example, it can be set to estimate a future current value, or it can be set to estimate a past current value.

In this manner, the approximation processing unit 37 calculates the approximate line (regression line λd) of the d-axis current id and the d-axis current approximate value id' based on the detected value of the d-axis current id. Further, based on the detected value of the q-axis current iq, an approximate line (regression line λq) of the q-axis current iq and an approximate q-axis current value iq' are calculated. This enables vector control using the d-axis current approximate value id' and the q-axis current approximate value iq', making it possible to realize highly accurate control with less waste.

Next, a control command value for the motor 25 is calculated using the d-axis current approximate value id' and the q-axis current approximate value iq' (step 108). Here, from the latest d-axis current approximate value id' and q-axis current approximate value iq', the U-phase voltage command value Vu ^* , V-phase voltage command value Vv ^* , and W-phase voltage command value Vw ^* , which are the control command values, are calculated. Calculated.

For example, if it is determined in step 105 that it is the control timing, the d-axis current approximate value id' and q-axis current approximate value iq' calculated in steps 106 and 107 are used to set the d-axis voltage command value Vd ^* Processing to update the q-axis voltage command value Vq ^* is executed.

Specifically, as the process of updating the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* , position estimation processing, axis error control processing, and voltage command update processing are executed in this order (see FIG. 7 reference).
The position estimation process is executed by the axis error calculation processing section 38. Specifically, the axis error Δθ of the motor 25 is calculated from the d-axis current approximate value id' and the q-axis current approximate value iq'.
The axis error control process is executed by the axis error control section 39. Specifically, a motor voltage V that causes the axis error Δθ to converge to 0 is calculated.

The voltage command update process is executed by the voltage command generation unit 42, and is a process of updating the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* . Specifically, using the d-axis current approximate value id', the q-axis current approximate value iq', the motor voltage V, and the electrical angular velocity command value ωe, the d-axis voltage command value Vd ^* and the q-axis voltage command value are determined. Vq ^* is updated.

As a method of controlling the motor 25, for example, there is a method of calculating an error in the rotational speed of the motor 25 from the axis error Δθ, and controlling the speed of the motor 25 so that the error approaches 0 (see FIG. 8). In this case, highly accurate speed control is possible, but speed control may increase the processing load required for feedback control.

On the other hand, as explained with reference to FIG. 2, in this embodiment, the speed control is omitted and the voltage command value (d-axis voltage The configuration is such that the command value Vd ^* and the q-axis voltage command value Vq ^* ) are controlled. This makes it possible to reduce the processing load required for feedback control and reduce unnecessary control.
Below, the operations of the d-axis voltage calculator 50 and the q-axis voltage calculator 51 in the voltage command generation section 42 will be specifically described.

The d-axis voltage calculator 50 calculates the d-axis voltage Vd, which is the source of the d-axis voltage command value Vd ^* . The d-axis voltage command value Vd ^* is calculated by performing non-interference processing on the d-axis voltage Vd.
Here, it is assumed that the electrical angular velocity command value for the motor 25 is ωe ^* , the q-axis inductance of the motor 25 is Lq, and the approximate q-axis current value is iq'. The d-axis voltage calculator 50 calculates the d-axis voltage Vd according to equation (1) shown below.
Vd=-ωe ^* ×Lq×iq'...(1)

Furthermore, the d-axis voltage command value Vd ^* is calculated based on the calculation result of equation (1). Specifically, the subtracter 53 subtracts the non-interference correction value Vda from the d-axis voltage Vd, and the result is calculated as the d-axis voltage command value Vd ^* . Note that the non-interference correction value Vda is calculated by the non-interference controller 52 according to the q-axis current approximate value iq'.

The q-axis voltage calculator 51 calculates the q-axis voltage Vq, which is the source of the q-axis voltage command value Vq ^* . The q-axis voltage command value Vq ^* is calculated by performing non-interference processing on the q-axis voltage Vq.
Here, the motor voltage is V and the d-axis voltage is Vd. The q-axis voltage calculator 51 calculates the q-axis voltage Vq according to equation (2) shown below.
Vq=sqrt(V ² -Vd ² )...(2)
Note that sqrt() in equation (2) means the square root of the value in ().

Furthermore, the q-axis voltage command value Vq ^* is calculated based on the calculation result of equation (2). Specifically, the adder 54 adds the non-interference correction value Vqa to the q-axis voltage Vq, and the result is calculated as the q-axis voltage command value Vq ^* . Note that the deinterference correction value Vqa is calculated by the deinterference controller 52 according to the d-axis current approximate value id'.

In this way, by performing non-interference processing on Vd calculated by equation (1) and Vq calculated by equation (2), the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* is calculated. The current value used in this non-interference process is also an approximate value calculated using a regression line.
The calculated d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* are converted into control command values (Vu ^* , Vv ^* , Vw ^* ) by a two-phase to three-phase converter 55.

Note that if it is determined in step 105 that it is not the control timing, steps 106 and 107 are not executed. In this case, the latest d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* are converted into control command values (Vu ^* , Vv ^* , Vw ^* ).

Once the control command value is calculated, it is determined whether or not to end the control of the motor 25 (step 109). For example, when the user of the air conditioner 100 performs an operation to stop the operation, the control of the motor 25 ends. If the control is to be terminated (Yes in step 109), the loop processing based on the flowchart of FIG. 5 is terminated. If control is to be continued (No in step 109), the processes from step 101 onwards are executed again.

[Motor control timing]
FIG. 7 is a time chart showing the timing of motor control. At the top of FIG. 7, a schematic graph showing temporal changes in the electrical rotation angle θe is illustrated. Below this graph, time charts of current detection processing, approximation processing, position estimation processing, axis error control processing, and voltage command updating processing are illustrated in this order. The horizontal axis of the graph and time chart in FIG. 7 is time.
Here, the control period T is set to the electrical angle period Te. Further, in FIG. 7, the end timing of the current detection process is set to the end timing of the electrical angle period Te (θe=2π).

As shown in FIG. 7, in the motor control device 30, current detection processing, approximation processing, position estimation processing, axis error control processing, and voltage command updating processing are repeatedly executed in this order.
Among these, in the current detection process, as described above, the U-phase current iu, the V-phase current iv, and the W-phase current iw are detected, and the results are converted into the d-axis current id and the q-axis current iq. The current detection process corresponds to step 103 and step 104 in FIG. The detection cycle Tm for executing this process is set to a cycle that allows sampling a predetermined number of times within the control cycle T.

In the approximation process, a regression line λd and a regression line λq are calculated for the d-axis current id and the q-axis current iq. Furthermore, the d-axis current approximate value id' and the q-axis current approximate value iq' are calculated from the regression line λd and the regression line λq. The approximation process corresponds to step 106 and step 107 in FIG.

The position estimation process, axis error control process, and voltage command update process are executed in step 108 in FIG. 6 when steps 106 and 107 are executed.
In the position estimation process, the axis error Δθ is calculated from the d-axis current approximate value id' and the q-axis current approximate value iq'. Further, in the axis error control process, the motor voltage V is calculated from the axis error Δθ. Furthermore, in the voltage command update process, the d-axis voltage command value Vd ^* and the q-axis Voltage command value Vq ^* is updated. In the next control cycle T, control command values (Vu ^* , Vv ^* , Vw ^* ) are calculated based on the updated d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* .

In this way, in the motor control device 30, current detection is performed a predetermined number of times in each control period T, and then the approximation process, position estimation process, axis error control process, and voltage command update process are executed to perform the approximation process. Feedback control using the values is executed.
Since the control period T of the feedback control is based on the electrical angle period Te, it is possible to reduce the frequency of control. Further, since the approximate value calculated from the approximate line is used as the value to be fed back, it is possible to stably continue motor control without being affected by, for example, sudden changes in current.

As described above, in the motor control device 30 according to the present embodiment, the d-axis current id and the q-axis current iq are detected and their approximate lines λd and λq are calculated every control period T. Control command values Vu ^* , Vv ^* , Vw ^* ) for the motor 25 are calculated from the d-axis current approximate value id' and the q-axis current approximate value iq' calculated using the approximate lines λd and λq. Since the control period T is set based on the electrical angle period Te, the frequency of control becomes low. Further, by using an approximation line, it is possible to calculate a feedback value without being affected by noise or the like. It becomes possible to realize appropriate motor control while reducing unnecessary control.

FIG. 8 is a block diagram showing a configuration example of a motor control device as a comparative example. The motor control device 130 shown in FIG. 8 is, for example, a device used for vector control of a general motor. Here, the same components as the motor control device 30 shown in FIG. 2 will be described with the same reference numerals.

As shown in FIG. 8, the motor control device 130 is not provided with a block for calculating an approximate line or an approximate value, and the detected d-axis current id and q-axis current iq are directly used for feedback.
For example, the axis error calculation processing section 80 uses the detected value as is to calculate the axis error Δθ. Furthermore, the PLL controller 81 calculates the estimated angular velocity ωe from the axis error Δθ. The estimated angular velocity ωe is input to a converter 83 via a low-pass filter 82 (LPF), and is converted into a mechanical angular velocity ωm. The mechanical angular velocity ωm is input to the voltage command generation section 85.
Furthermore, the integrator 84 calculates the electrical rotation angle θe by integrating the estimated angular velocity ωe. The deinterference controller 52 also calculates deinterference correction values (Vda and Vqa) using the estimated angular velocity ωe, the d-axis current detection value id, and the q-axis current detection value iq.

In the voltage command generation unit 85, the subtracter 86 calculates the angular difference between the mechanical angular velocity command value ωm and the mechanical angular velocity ωm. Further, the speed controller 87 calculates the q-axis current command value iq ^* using an integrator and a proportional device according to the angular velocity difference. This corresponds to the speed control process described above.

Furthermore, the subtracter 88 subtracts the d-axis current detection value id from the d-axis current command value id ^* inputted from the outside. From this subtraction result, the d-axis current controller 89 calculates the d-axis voltage command value Vd ^** . Further, the subtracter 90 subtracts the detected q-axis current value iq from the q-axis current command value iq ^* input from the speed controller 87. From this subtraction result, the q-axis current controller 91 calculates the q-axis voltage command value Vq ^** .
Vd ^** and Vq ^** are parameters corresponding to Vd in equation (1) and Vq in equation (2) above. The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are calculated by performing non-interference processing on Vd ^** and Vq ^** .

In feedback control that uses the detected values as they are as shown in FIG. 8, components that change due to disturbances such as noise are also fed back. For example, if a disturbance such as noise causes an error in the detected value and the detected value changes suddenly, a hunting phenomenon occurs in which the control command value temporarily changes greatly due to the inaccurate detected value, and then converges while oscillating. This may occur. As described above, when harmonic components are superimposed on the control command value due to the influence of disturbances such as noise, the operation of the motor becomes unstable.
Furthermore, in a situation where the control command value oscillates, energy loss (control loss) due to speed control or the like may occur. For example, energy is wasted by unnecessarily accelerating the motor in accordance with an inaccurate detection value that deviates from the original detection value.

Further, in the motor control device 130 shown in FIG. 8, feedback control is repeatedly performed at a period approximately several times the carrier frequency Tc (for example, 4 to 5 times the carrier period). Therefore, the motor control device 130 becomes a device that frequently performs current detection and feedback control using the detected value.
In this way, when control is repeatedly performed at a period based on the carrier frequency Tc, unnecessary control may increase. Moreover, it becomes more susceptible to the effects of the above-mentioned noise, etc., and energy efficiency may deteriorate.

One method for removing components that change due to disturbances such as noise is to use a first-order lag filter. In this case, a time delay occurs depending on the characteristics of the filter. For example, if the current value fluctuates during the time delay, the current value calculated by averaging may deviate from the actual current current value.
For this reason, for example, control may be performed to abruptly change the value of the current flowing through the motor, and the operation of the motor may become unstable. Furthermore, when sudden load fluctuations or noise occur, the current value cannot be accurately estimated due to the time delay.

Further, the averaging process using the first-order lag filter needs to be performed every time a current value is detected, which may increase the number of control operations and increase the processing load.
For example, when driving a fan motor that drives a propeller fan, the control does not necessarily need to follow sudden load changes. In this case, if averaging processing is performed using a first-order lag filter every time a current value is detected, there will be a lot of unnecessary control.

On the other hand, in the motor control device 30 according to the present embodiment, the control period T for performing feedback control is set based on the electrical angle period Te. For example, as shown in FIG. 7, the approximation process and the subsequent process of updating the voltage command value and the like are executed at the electrical angle period Te. This makes it possible to significantly reduce the number of times the control is performed, compared to the case where feedback control is frequently performed based on the carrier cycle Tc as shown in FIG. 8, for example. As a result, unnecessary feedback control can be eliminated.

Furthermore, in this embodiment, the regression line λd and the regression line λq for the d-axis current id and the q-axis current iq are calculated for each control cycle T. Then, a d-axis current approximate value id' and a q-axis current approximate value iq' are calculated from the regression line λd and the regression line λq as current values used for feedback control. This makes it possible to accurately detect the current value without being affected by sudden load fluctuations, noise, etc., compared to the case where, for example, a first-order lag filter is used.

Further, the values of the regression line λd and the regression line λq at the detection timing of the last data point are used for the d-axis current approximate value id' and the q-axis current approximate value iq'. In this way, by using the final value of the regression line, each approximate value will not deviate greatly from the actual current current value. As a result, it becomes possible to stably control the motor 25.

For example, in averaging processing as typified by a first-order lag filter, a time delay occurs due to filtering, making feedback control redundant. If a sudden load change occurs during this time delay, the current waveform may become discontinuous.
In this embodiment, the values used for feedback control (approximate values id' and iq') are stabilized by using the regression line (λd and λq). This makes it possible to alleviate discontinuity in the current waveform due to redundant feedback control.
Further, since the value used for feedback control is not affected by noise or the like, it becomes possible to stably supply a sinusoidal waveform current to the motor 25, and it becomes possible to stabilize the operation of the motor 25.
Furthermore, control in response to sudden load fluctuations, noise, etc. is less likely to occur. For example, a sudden load change may occur when a person crosses in front of the outdoor unit 2 of the air conditioner 100, but any control that follows this change would be wasteful. Such unnecessary control is reduced, and the motor can be controlled efficiently.

In this way, in this embodiment, the number of times of control is reduced by setting the control period T based on the electrical angular period Te, and by using the approximate value calculated from the approximate line, there is no need to follow sudden loads. . This makes it possible to sufficiently reduce unnecessary control, and it becomes possible to achieve energy savings in the device.

For example, when driving a propeller fan that has a large moment of inertia and does not require frequent control, appropriate control is possible even if the control cycle T is relatively long, and the present invention can be effectively applied. It is. In this case, it becomes possible to sufficiently reduce energy loss and the like associated with control and realize efficient motor control.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways. For example, in the above embodiment, the electrical angular period Te is the period of the alternating current supplied to the motor 25, but the period of the alternating current voltage supplied to the motor 25 may be the electrical angular period Te.

In the above embodiments, a configuration has been described in which a current detection circuit including two current sensors detects two currents among the U-phase current, V-phase current, and W-phase current. The method of detecting these motor currents is not limited.
For example, the current detection circuit may be configured to detect motor current using a single shunt resistor. In this case, a shunt resistor is connected in series on the wiring connecting the IPM and GND, and the voltage between the terminals of the shunt resistor is detected. This makes it possible to detect the current flowing from the IPM to GND through the windings of each phase of the motor.
U-phase current, V-phase current, and W-phase current may be detected by such a method. In this case, since it is not necessary to provide multiple current sensors, etc., it is possible to reduce the device cost.

In the above embodiments, an example of calculating approximate lines and approximate values for the d-axis current and the q-axis current has been described. The present invention is not limited to this, and for example, approximate lines and approximate values for the U-phase current, V-phase current, and W-phase current may be calculated. In this case, approximate values of the U-phase current, V-phase current, and W-phase current are calculated using, for example, a sinusoidal approximation line. A d-axis current and a q-axis current are calculated from approximate values of these three phases and used for feedback. As a result, even when sudden noise or the like occurs, for example, the approximate values for each phase can be stably calculated, making it possible to realize appropriate motor control while reducing unnecessary control.

6u, 6v, 6w...PWM signal 24...Fan 25...Motor 30...Motor control device 31...Drive circuit 32...Arithmetic circuit 33...Current detection circuit 36...3-phase-2-phase converter 37...Approximation processing unit 38...Axis error Arithmetic processing section 39... Axis error control section 40... Integrator 42... Voltage command generation section 45... PWM modulator 46... IPM
50...d-axis voltage calculator 51...q-axis voltage calculator 100...air conditioner

Claims (12)

a drive unit that drives the motor by supplying an AC voltage or AC current to the motor according to a control command value;
a current detection unit that detects a motor current flowing through the motor;
An approximate line of the motor current is calculated based on a plurality of detected values of the motor current for each control cycle based on the electrical angle period of the AC voltage or the AC current, and the approximate line of the motor current is calculated based on the approximate line. a current approximation unit that calculates an approximate value of the motor current;
A motor control device comprising: a control section that calculates the control command value based on the approximate value. The motor control device according to claim 1,
The motor current is a d-axis current and a q-axis current,
The current detection unit detects the d-axis current and the q-axis current,
The approximate line is an approximate line of the d-axis current and an approximate line of the q-axis current,
The approximate value is an approximate value of the d-axis current and an approximate value of the q-axis current,
The current approximation unit calculates an approximate line of the d-axis current and an approximate value of the d-axis current based on the detected value of the d-axis current, and calculates an approximate line of the d-axis current and an approximate value of the d-axis current based on the detected value of the q-axis current. A motor control device that calculates an approximate line of axis current and an approximate value of the q-axis current. The motor control device according to claim 2,
The control unit includes:
an axis error calculation unit that calculates an axis error of the motor based on the approximate value of the d-axis current and the approximate value of the q-axis current;
a voltage adjustment unit that adjusts the motor voltage so that the axis error converges to zero;
A command value for the d-axis voltage and a command value for the q-axis voltage based on the approximate value of the d-axis current, the approximate value of the q-axis current, the adjusted motor voltage, and the speed command value for the motor. A motor control device comprising: a command value calculation section that calculates . The motor control device according to claim 3,
The command value calculation unit sets the command value of the electrical angular velocity to the motor as ωe ^* , the q-axis inductance of the motor as Lq, and the approximate value of the q-axis current as iq', and calculates the d-axis voltage Vd as follows. Calculate according to formula (1) shown below, and calculate the command value of the d-axis voltage based on the calculation result. Vd=-ωe ^* ×Lq×iq' (1)
Motor control device. The motor control device according to claim 4,
The command value calculation unit calculates the q-axis voltage Vq according to equation (2) shown below, where the motor voltage is V and the d-axis voltage is Vd, and the q-axis voltage is calculated based on the calculation result. Calculate the command value Vq=sqrt(V ² - Vd ² )...(2)
Motor control device. The motor control device according to any one of claims 1 to 5,
The approximate line is an approximate line that approximates a change in the motor current with respect to time,
The current detection unit detects the motor current at a predetermined period,
The current approximation unit calculates the approximate value of the motor current from the detection timing of the latest detected value among the detected values of the motor current used to calculate the approximate line and the approximate line. The motor control device according to any one of claims 1 to 6,
The approximate line is a regression line calculated by the least squares method for the plurality of detected values. The motor control device. The motor control device according to any one of claims 1 to 7,
The control period is set to be n times the electrical angle period or 1/n times the electrical angle period, where n is an arbitrary positive integer value. The motor control device according to any one of claims 1 to 8,
The drive unit includes a PWM generation unit that generates a PWM signal based on the control command value, and a power supply unit that supplies power to the motor based on the PWM signal,
The current detection unit executes a current detection process of detecting the motor current at least once within the carrier cycle of the PWM signal a predetermined number of times within the control cycle. The motor control device according to claim 9,
The current detection unit detects the motor current using a single shunt resistor. The motor control device. The motor control device according to any one of claims 1 to 10,
The motor is a fan motor that drives a fan installed in an air conditioner. driving the motor by supplying an alternating current voltage or alternating current according to a control command value to the motor;
detecting a motor current flowing through the motor;
An approximate line of the motor current is calculated based on a plurality of detected values of the motor current for each control cycle based on the electrical angle period of the AC voltage or the AC current, and the approximate line of the motor current is calculated based on the approximate line. Calculate the approximate value of the motor current,
A motor control method, wherein the control command value is calculated based on the approximate value for each control cycle.

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