JP2007116770A - Motor driving unit and its control method, and air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driving unit, which can reduce the stress to an element by the eddy current at start of a motor, its control method, and an air conditioner. <P>SOLUTION: A motor driver 40, which sets the target value Iqtgt of a current from the difference between the target velocity ωtgt and the present velocity ω of the motor 30 and controls a drive signal to be supplied to each phase of the motor 30, based on this current target value Iqtgt, suppresses the divergence of the target value Iqtgt of the current by setting the upper limit value Iqmax of the target value Iqtgt of the current in the case of starting the motor 30, and also performs the open phase processing for detecting the open phase of a motor wire, based on the values Iu, Iv, and Iw of currents supplied to each phase of the motor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor driving device that drives a motor, a control method thereof, and an air conditioner that drives a compressor.

2. Description of the Related Art Conventionally, there is known an air conditioner that performs speed control of a brushless DC motor, which is a permanent magnet type synchronous motor, without a sensor for detecting the rotational speed and position of a rotor and driving a compressor by this motor. In this type of sensorless control, a part of a three-phase AC current supplied from a three-phase power source to a brushless DC motor is converted into a rotating coordinate system of the rotor to obtain a torque current Iq. The torque current target value is set based on the difference between the estimated value and the target speed, and the motor speed is controlled to the target speed based on the deviation between the torque current target value and the measured torque current. Yes (see, for example, Patent Document 1).
The air conditioner described in Patent Document 1 obtains a variation state of a current value (motor current) flowing through each phase of a motor driven by a three-phase power source, and detects a missing phase of the motor line from the variation state. Phase loss detection processing is performed.
JP-A-2005-181167

In the conventional motor control, when starting the motor, the target speed and the estimated speed are different, so the torque current target value tends to diverge, and the motor current set based on this torque current target value increases. Occurs. In this case, if the motor wire is out of phase, the motor current becomes higher, and the overcurrent causes stress on elements such as a protection circuit.
Further, since the conventional phase loss detection process detects the phase loss of the motor wire from the variation state of the current value flowing through each phase of the motor, the phase loss detection is not performed at the time of starting the motor where the current value is not stable.

  The present invention has been made in view of the above-described circumstances, and reduces a stress on an element due to an overcurrent at the time of starting the motor, and also detects a motor wire phase loss at the time of starting the motor, and its control It is to provide a method and an air conditioner.

In order to solve the above-described problems, the present invention sets a current target value from a difference between a target speed and a current speed of the motor, and controls a drive signal supplied to each phase of the motor based on the current target value. In the drive device, when starting the motor, an upper limit value of the current target value is set to suppress the divergence of the current target value, and the motor line is missing based on the current value supplied to each phase of the motor. A phase loss detection process for detecting a phase is performed.
According to the present invention, when starting the motor, the upper limit value of the current target value is set to suppress the divergence of the current target value, and the motor wire phase loss is determined based on the current value supplied to each phase of the motor. Since the phase loss detection process to be detected is performed, it is possible to reduce the stress on the element due to overcurrent and to detect the phase loss of the motor wire when starting the motor.

  In the above configuration, there is an estimation means for estimating the current speed of the motor from the current value supplied to each phase of the motor, and when starting the motor, the target is determined based on the difference between the target speed and a preset virtual current speed. A starting speed control is performed to control the drive signal by setting a current value. After a predetermined period, a target current value is calculated from the difference between the current speed and the target speed estimated by the estimating means from the starting speed control. May be set to shift to normal speed control for controlling the drive signal.

  In the above configuration, it is preferable that the gain at the start speed control is set to a value that is the same as or close to the gain at the normal speed control. In the above configuration, the virtual current speed is preferably a speed that increases with time. Further, the predetermined period is preferably a predetermined time corresponding to after the start speed control is started and the current speed of the motor substantially matches the target speed.

  Further, in the above configuration, the motor is a motor that drives a compressor that compresses refrigerant, and an upper limit value that sets an upper limit value of the current target value based on a differential pressure at the inlet and outlet of the compressor at the time of starting the motor. You may make it have a setting means. According to this configuration, the motor can be started even in a situation where the load is high due to the pressure at the inlet / outlet of the compressor 16 being not equalized.

  Further, the present invention provides a control method for a motor drive device that sets a current target value from a difference between a target speed and a current speed of the motor, and controls a drive signal supplied to each phase of the motor based on the current target value. When starting the motor, the upper limit value of the target current value is set to suppress the divergence of the target current value, and the motor wire phase is detected based on the current value supplied to each phase of the motor. The phase loss detection process is performed.

  Further, the present invention has a motor control unit that sets a current target value from the difference between the target speed and the current speed of the motor, and controls a drive signal supplied to each phase of the motor based on the current target value, In the air conditioner in which the compressor for refrigerant compression is driven by the motor, the motor control unit sets an upper limit value of the current target value and suppresses the divergence of the current target value when starting the motor. In addition, a phase loss detection process for detecting a phase loss of the motor wire based on the current value supplied to each phase of the motor is performed.

  In the present invention, when starting a motor, the upper limit value of the current target value is set to suppress the divergence of the current target value, and the motor wire phase loss is detected based on the current value supplied to each phase of the motor. Since the phase loss detection process is performed, it is possible to reduce stress on the element due to overcurrent at the time of starting the motor and to detect the phase loss of the motor line at the time of starting the motor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of an air conditioner including a compressor driven by a permanent magnet type synchronous motor (hereinafter referred to as a brushless DC motor).
As shown in FIG. 1, the air conditioner 10 includes an outdoor unit 11, an indoor unit 12, and a control device 13, and an outdoor refrigerant pipe 14 of the outdoor unit 11 and an indoor refrigerant pipe 15 of the indoor unit 12 are connected to a pipe 24. , 25, and the outdoor unit 11 and the indoor unit 12 are controlled by the control device 13.

The outdoor unit 11 is installed outside, a compressor 16 is disposed in the outdoor refrigerant pipe 14, an accumulator 17 is connected to the suction side of the compressor 16, and a four-way valve is connected to the discharge side of the compressor 16. 18 and the outdoor heat exchanger 19 are connected in order. The outdoor unit 11 is provided with an outdoor fan 20 that blows air toward the outdoor heat exchanger 19.
The indoor unit 12 is installed indoors, an indoor heat exchanger 21 and an electric expansion valve 22 are disposed in the indoor refrigerant pipe 15, and an indoor fan 23 for blowing air to the indoor heat exchanger 21 is disposed. .

  The air conditioner 10 is set to the cooling operation or the heating operation by switching the four-way valve 18 of the outdoor unit 11 to the cooling side or the heating side. That is, when the four-way valve 18 is switched to the cooling side, the refrigerant flows as indicated by the solid line arrow, the outdoor heat exchanger 19 functions as a condenser, and the indoor heat exchanger 21 functions as an evaporator to enter a cooling operation state. Cool the air. When the four-way valve 18 is switched to the heating side, the refrigerant flows as indicated by broken arrows, the indoor heat exchanger 21 functions as a condenser, and the outdoor heat exchanger 19 functions as an evaporator to enter a heating operation state. Heat up.

The compressor 16 includes a brushless DC motor 30 having a stator winding (not shown) and a permanent magnet rotor (rotor). The brushless DC motor 30 is driven by a motor drive unit (motor drive device) 40. Driven.
FIG. 2 is a block diagram of the motor drive unit 40. As shown in the figure, the motor drive unit 40 includes a three-phase PWM inverter 41 that supplies a drive signal to each phase of the brushless DC motor 30, and a control unit 50. The three-phase PWM inverter 41 includes an AC power supply. AC power from 42 is converted into DC power by a rectifier circuit 43 and supplied.
The three-phase PWM inverter 41 converts the DC power supplied from the rectifier circuit 43 into three-phase AC power having a predetermined frequency and voltage in accordance with the three-phase voltage commands Vu, Vv, and Vw from the control unit 50, and a drive signal As a result, the brushless DC motor 30 is driven to rotate.

  The control unit 50 includes a power input unit (current detection unit) 51, a three-phase / two-phase coordinate conversion unit 52, a current speed / position estimation unit 53, a speed control unit 54, a phase control unit 55, a current control unit 56, and a two-phase control unit. / A three-phase coordinate conversion unit 57 and a controller 60 that controls the operation of the motor drive unit 40. The controller 60 may also serve as the controller 13 that controls the operation of the air conditioner 10.

  The current input unit 51 takes in two-phase AC current values Iu and Iv from the three-phase AC current supplied from the three-phase PWM inverter 41 to the brushless DC motor 30 by A / D conversion (analog to digital conversion). . In the present embodiment, the suffixes u, v, and w correspond to the u-phase, v-phase, and w-phase of the brushless DC motor 30, respectively.

  The three-phase / two-phase coordinate conversion unit 52 converts the alternating currents Iu and Iv detected by the current input unit 51 into a rotational coordinate system (dq coordinate system) on the rotor in the brushless DC motor 30 to generate a magnetic flux. A current Id (d-axis current) and a torque current Iq (q-axis current) are calculated.

  The current speed / position estimation unit 53 determines the current speed ω and position of the brushless DC motor 30 every 100 μsec, for example, based on the magnetic flux current Id and the torque current Iq coordinate-converted by the three-phase / two-phase coordinate conversion unit 52. Calculate and estimate.

  Based on the deviation between the current speed ω estimated by the current speed / position estimation unit 53 and the target speed ωtgt, the speed control unit 54 executes, for example, proportional integral control (PI control) every 1 ms to obtain a torque current target value. Iqtgt is generated. The rotor target speed ωtgt is set by the controller 60.

  The current control unit 56 performs PI control based on the deviation between the torque current target value Iqtgt generated by the speed control unit 54 and the actual torque current Iq, and calculates the torque voltage Vq (Vq axis voltage). PI control is executed based on the deviation between the magnetic flux current target value Idtgt generated by the phase controller 55 and the actual magnetic flux current Id, and the magnetic flux voltage Vd (Vd axis voltage) is calculated. By this PI control, these deviations are controlled to be zero.

  The two-phase / three-phase coordinate conversion unit 57 converts the magnetic flux voltage Vd and the torque voltage Vq calculated by the current control unit 56 into a three-phase AC coordinate system, and a pulse-modulated sinusoidal voltage command Vu, Vv and Vw are calculated, and these voltage commands Vu, Vv and Vw are output to the switching element of the three-phase PWM inverter 41. As a result, the three-phase AC power, which is a pseudo sine wave whose voltage is subjected to pulse width modulation, is supplied from the three-phase PWM inverter 41 to the brushless DC motor 30, and the current speed ω of the brushless DC motor 30 becomes the target speed ωtgt. To be controlled.

  The controller 60 is a computer that includes a CPU, a ROM that stores and executes various control data read and executed by the CPU, and a RAM that temporarily stores various data. The control program stores the CPU in the ROM. To control the entire motor drive unit 40. The controller 60 also performs a phase loss detection process for detecting a phase loss of the motor line, that is, functions as a failure detection means for detecting the phase loss of the motor wire.

  Under the above configuration, when the load of the indoor unit 12 fluctuates during motor operation (except when the motor is started), the controller 60 changes the target speed ωtgt in accordance with the load fluctuation, and the control of the controller 60 The speed control unit 54 generates a torque current target value Iqtgt based on the deviation between the current speed ω estimated by the current speed / position estimation unit 53 and the target speed ωtgt, and the phase control unit 55 The magnetic flux current target value Idtgt is generated based on the current Iq, and the current control unit 56 is based on the deviation between the torque current target value Iqtgt and the actual torque current Iq and the deviation between the magnetic flux current target value Idtgt and the actual magnetic flux current Id. PI control is executed, and voltage commands Vu, Vv, Vw are output to the three-phase PWM inverter 41 via the two-phase / three-phase coordinate converter 57. Thereby, the rotational speed of the motor 30, that is, the rotational speed of the compressor 16 is appropriately controlled according to the load of the indoor unit 12. The above is the normal speed control (normal speed control). During this speed control, the controller 60 executes a phase loss detection process that will be described in detail later.

By the way, when the motor is started, the torque current target value Iqtgt tends to diverge due to the difference between the target speed ωtgt of the motor 30 and the current speed ω, and the motor current set based on the torque current target value Iqtgt may increase. There is a risk that stress will be applied to elements such as a protection circuit (not shown) due to overcurrent.
Therefore, in the present embodiment, when the motor is started, the controller 60 sets an upper limit value Iqmax of the torque current target value Iqtgt to the speed control unit 54 so that the motor current does not become excessively high. Hereinafter, start control of the motor 30 will be described.

When a start instruction for the motor 30 is input, first, the controller 60 sets the magnetic flux current target value Idtgt of the phase control unit 55 to zero and sets the upper limit value Iqmax of the torque current target value Iqtgt of the speed control unit 54. Further, the PI control gain of the speed control unit 54 is set to a value that is the same as or close to the gain during the normal speed control.
At the time of starting the motor, the controller 60 sets a predetermined low-speed starting target speed ωtgt1 (for example, 4 Hz) as the target speed ωtgt. The starting target speed ωtgt1 is set to the starting target speed ωtgt1 and the motor. It is held until at least the current speed ω of 30 matches.
Here, the upper limit value Iqmax is set to a value that is sufficient to control the motor speed to the starting target speed ωtgt1 and that keeps the motor current below a value that does not cause stress on the element. .

  Further, when the motor is started, the controller 60 sets a virtual current speed ω1 that increases step by step for each predetermined control cycle as the current speed ω, and the current speed / position estimation unit 53 estimates the speed control unit 54. The configured current speed ω is not used.

Therefore, by the motor start control (starting speed control), the speed control unit 54 generates the torque current target value Iqtgt based on the deviation between the virtual current speed ω1 set by the controller 60 and the starting target speed ωtgt1. Since the upper limit value Iqmax of the torque current target value Iqtgt is set, the torque current target value Iqtgt is limited to a value equal to or lower than the upper limit value Iqmax, and the divergence of the torque current target value Iqtgt is suppressed.
For this reason, the upper limit value of the torque voltage Vq calculated by the current control unit 56 based on the deviation between the torque current target value Iqtgt and the actual torque current Iq is also lowered, and as a result, it is output to the three-phase PWM inverter 41. The upper limit value of the motor current supplied from the three-phase PWM inverter 41 to each phase can be suppressed by the voltage commands Vu, Vv, and Vw. Thus, the motor speed can be increased to the starting target speed ωtgt1 by gradually increasing the rotational speed of the motor 30 while suppressing an excessive increase in the motor current.

  When the motor speed reaches the starting target speed ωtgt1 and a predetermined period elapses, the controller 60 cancels the settings of the upper limit value Iqmax and the speed ω1, and the speed control unit 54 performs the current speed / position estimation unit 53. Transition is made to normal speed control in which speed control is performed based on the deviation between the estimated current speed ω and the target speed ωtgt. The transition timing to the normal speed control is a time sufficient for the motor speed to reach the start target speed ωtgt1 on the assumption that the motor 30 is normal from the start timing of the start control of the motor 30. It is set at a timing when a corresponding preset set time has elapsed.

In the present embodiment, the controller 60 performs the phase loss detection process in parallel with the motor start control. This phase loss detection process is a process for detecting a phase loss of the motor line based on the variation state of the current values Iu, Iv, and Iw flowing through the respective phases of the motor 30. Specifically, the controller 60 performs the current input unit 51. The current values Iu, Iv, and Iw of the three phases (u phase, v phase, and w phase) detected by the above are acquired, the largest current value among the current values Iu, Iv, and Iw is Ia, and the smallest current value is Ib In this case, the current ratio X is obtained by a calculation formula of X = Ia / Ib, and this current ratio X is compared with a predetermined reference value for phase loss determination. If it is equal to or greater than this reference value, it is determined that the motor wire is in phase, and the motor 30 is forcibly stopped and a notification means (not shown) notifies the fact.
In the present embodiment, as described above, the upper limit value Iqmax of the torque current target value Iqtgt is set to suppress the divergence of the torque current target value Iqtgt. Therefore, the motor current is compared as compared with the case where the upper limit value Iqmax is not set. It is possible to detect the phase loss of the motor wire even when the motor is started.

  As described above, according to this embodiment, when the motor 30 is started, the upper limit value Iqmax of the torque current target value Iqtgt is set, so that the divergence of the torque current target value Iqtgt at the time of starting the motor is suppressed. It is possible to reduce the stress on the element due to overcurrent, and to detect the phase loss of the motor wire when starting the motor. As described above, since the phase failure of the motor wire can be detected during the motor start, it is possible to avoid the occurrence of overcurrent caused by the phase loss of the motor wire, thereby also reducing the stress on the element. Become.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, A various change implementation is possible.
For example, in the above embodiment, the case where the upper limit value Iqmax of the torque current target value Iqtgt is set as a fixed value is exemplified, but the upper limit value Iqmax may be varied. For example, the differential pressure at the inlet / outlet of the compressor 16 (including the differential pressure between the high pressure portion and the low pressure portion of the refrigerant circuit) may be detected, and the upper limit value Iqmax may be increased or decreased according to this differential pressure. In this case, when the compressor 16 is restarted immediately after the operation is stopped, that is, when the motor 30 is started in a situation where the load is comparatively high because the inlet / outlet pressure of the compressor 16 is not equalized, the load depends on the load. Thus, the upper limit value Iqmax can be set high, and the motor 30 can be started by increasing the torque when starting the motor. The upper limit value setting means for setting the upper limit value Iqmax is not limited to the controller 60 and may be the control device 13.

  In the above embodiment, the current values Iu, Iv, and Iw of the three phases (u phase, v phase, and w phase) are acquired, and the motor wire missing phase is detected from the variation state of these current values Iu, Iv, and Iw. However, the present invention is not limited to this, and two-phase (u-phase, v-phase) current values Iu and Iv are detected, and the remaining one-phase (w-phase) current value Iw is detected from this detection result. May be detected, and the phase loss of the motor wire may be detected from the variation state of these current values Iu, Iv, and Iw. In this case, using the fact that the sum of the current values flowing through the phases of the motor 30 is always zero (Iu + Iv + Iw = 0), the remaining current values Iu and Iv of the detected two phases (u-phase and v-phase) are used. The one-phase (w-phase) current value Iw may be estimated. Further, not only the above-described phase loss detection processing, but also known phase loss detection processing may be widely applied.

It is a figure which shows the structure of the air conditioning apparatus which concerns on this embodiment. It is a block diagram of the motor drive part of an air conditioning apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Air conditioning apparatus 11 Outdoor unit 12 Indoor unit 13 Control apparatus (upper limit value setting means)
16 Compressor 30 Brushless DC motor 40 Motor drive unit (motor drive device)
51 Power input unit (current detection unit)
52 Three-phase / two-phase coordinate conversion unit 53 Current speed / position estimation unit 54 Speed control unit 55 Phase control unit 56 Current control unit 57 Two-phase / three-phase coordinate conversion unit 60 Controller (open phase detection means, upper limit value setting means)

Claims (8)

In the motor drive device that sets the current target value from the difference between the target speed and the current speed of the motor, and controls the drive signal supplied to each phase of the motor based on the current target value.
When starting the motor, an upper limit value of the current target value is set to suppress the divergence of the current target value, and a motor line phase loss is detected based on the current value supplied to each phase of the motor. A motor driving device that performs phase loss detection processing. Having estimation means for estimating a current speed of the motor from a current value supplied to each phase of the motor;
When starting the motor, start speed control is performed to control the drive signal by setting a target current value from the difference between the target speed and a preset virtual current speed. After a predetermined period, the start speed control is performed. 2. The motor according to claim 1, wherein the motor shifts to normal speed control in which a target current value is set based on a difference between a current speed and a target speed estimated by the estimation means and the drive signal is controlled. Drive device.   The motor drive device according to claim 2, wherein the gain at the time of starting speed control is set to a value that is the same as or close to the gain at the time of normal speed control.   The motor driving apparatus according to claim 2, wherein the virtual current speed is a speed that increases as time elapses.   5. The predetermined period is set to a predetermined time after the start speed control is started and the current speed of the motor substantially coincides with the target speed. The motor drive device according to any one of the above. The motor is a motor that drives a compressor that compresses the refrigerant,
6. The motor drive device according to claim 1, further comprising upper limit value setting means for setting an upper limit value of the current target value based on a differential pressure at an inlet / outlet of the compressor at the time of starting the motor. . In a control method of a motor drive device that sets a current target value from a difference between a target speed and a current speed of the motor, and controls a drive signal supplied to each phase of the motor based on the current target value.
When starting the motor, an upper limit value of the current target value is set to suppress the divergence of the current target value, and a motor line phase loss is detected based on the current value supplied to each phase of the motor. A method for controlling a motor drive device, comprising performing phase loss detection processing. A current control value is set from the difference between the target speed and the current speed of the motor, and a motor control unit that controls a drive signal supplied to each phase of the motor based on the current target value is provided. In the air conditioner in which the compressor is driven,
When starting the motor, the motor control unit sets an upper limit value of the current target value to suppress divergence of the current target value, and based on the current value supplied to each phase of the motor, the motor line An air conditioner that performs an open phase detection process for detecting an open phase.

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