JP2020080582A - Motor controller and air conditioner having the same - Google Patents

Abstract

To achieve control with reduced motor phase current in a motor controller in a power factor control (phase difference control of voltage and current) system and an air conditioner having the motor controller.SOLUTION: A motor controller 16 comprises a target phase difference setting section 30 for outputting a target phase difference to a phase difference control section 22. The target phase difference setting section 30 comprises: a torque calculation section 21 for detecting a torque value of a motor 7a; and a phase difference extraction section 32 for extracting a minimum current target phase difference which is experimentally obtained and with which motor phase current of the motor 7a becomes minimum at every torque value on the basis of the calculated operation torque value to be outputted. Even if the torque value of a compressor 7 variously changes in accordance with a state of a refrigerant load, control with reduced motor phase current can be performed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an embedded permanent magnet synchronous motor (IPMSM) used in a compressor or the like, and particularly, in a sinusoidal drive system, the position of a motor phase voltage and a motor phase current. The present invention relates to a motor control device that controls a motor based on a phase difference and an air conditioner including the motor control device.

  For example, Patent Document 1 discloses power factor control (voltage/current phase difference control) for controlling a compressor motor by a phase difference between a motor phase current and a motor phase voltage. The motor control device described in this document is shown in the block diagram of FIG.

  In the motor control device of FIG. 5, the phase difference detection unit 111 of the phase difference control unit 110 detects the phase difference between the motor phase voltage and the motor phase current in the motor 100. Further, the power detection unit 117 detects the power used to drive the motor 100. Then, the power minimization unit 118 determines the phase difference target value that brings the detected power close to the minimum value. Then, the phase difference control unit 110 generates a control signal so that the phase difference detected by the phase difference detection unit 111 approaches the phase difference target value. The inverter unit 102 drives the motor 100 based on the generated control signal.

  By the way, when the number of revolutions of the motor 100 is constant, the power consumption of the motor 100 is plotted on the vertical axis, and the target phase difference is plotted on the horizontal axis. There is a characteristic that becomes a curve of. For example, when the target phase difference for controlling the motor 100 is changed from 5 degrees to 40 degrees at a certain rotation speed and the power consumptions at the respective target phase differences are compared, the value of the power consumption becomes the minimum. There is a target phase difference. Therefore, the power minimization unit 118 searches for the target phase difference that minimizes the power consumption while sequentially changing the target phase difference each time the rotation speed changes, and uses the target phase difference extracted in this search as the phase difference. Output to the control unit 110. As a result, power consumption can be minimized at various rotation speeds.

  On the other hand, when the target phase difference that minimizes the power consumption is searched while sequentially changing the target phase difference while the motor 100 is operating, it is not known in advance which target phase difference will be the minimum power consumption. Depending on the setting of the target phase difference in the first search, the power consumption may be maximum, the components used in the inverter unit 102 may deteriorate, and the motor phase current may exceed a predetermined value and become an overcurrent.

  Further, in such a power factor control method, the motor phase voltage is changed in order to change the phase difference between the motor phase voltage and the motor phase current. Specifically, the phase difference is increased by increasing the amplitude of the motor phase voltage, and the phase difference is decreased by decreasing the amplitude of the motor phase voltage. Further, since the motor phase current is affected by the torque of the motor, the motor phase current does not always become the minimum at the target phase difference that minimizes the power consumption described above.

  By the way, when controlling a large-sized device, for example, a compressor of a commercial air conditioner by such a power factor control method, a motor phase current may also flow by 70-80 amperes. For this reason, an IPM (Intelligent Power Module) that constitutes the inverter unit must also be able to withstand this current, but parts with a large current rating are very expensive. Also, the air conditioner monitors the current to prevent overcurrent, and if the target phase difference is changed to search for the target phase difference that minimizes the power consumption described above, a large motor phase current will flow. There was also a problem that overcurrent caused the entire air conditioner to stop and stable operation could not be achieved.

JP-A-2002-374691 (paragraph numbers 0069 to 0087)

  SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and reduce a motor phase current in a power factor control (voltage/current phase difference control) type motor control device and an air conditioner including the same. ..

In order to solve the above-mentioned problems, the present invention provides a motor control device according to claim 1 of the present invention.
A motor control device for driving a motor by controlling a phase difference between a motor phase current and a motor phase voltage by an amplitude of the motor phase voltage,
The motor control device,
A phase difference control unit that detects the motor phase current and controls the amplitude of the motor phase voltage so that the phase difference between the motor phase current and the motor phase voltage becomes a target phase difference,
A target phase difference setting unit that outputs the target phase difference to the phase difference control unit,
The target phase difference setting means,
A minimum current target phase difference that minimizes the motor phase current is stored in advance for each value of the operating torque that is the torque during operation of the motor, and corresponds to the value of the operating torque input during operation of the motor. Phase difference extracting means for outputting the minimum current target phase difference as the target phase difference.

The invention of the air conditioner according to claim 2 of the present invention is
The motor control device, a motor driven by the motor control device, a compressor provided with the motor, and a torque calculation means for calculating the value of the operating torque of the motor and outputting the value to the phase difference extraction means; A discharge pressure sensor for detecting the discharge pressure of the compressor,
The torque calculating means calculates the value of the operating torque based on the discharge pressure.

By using the above means, the motor control device according to the present invention and the air conditioner including the same can perform control with the motor phase current reduced.
Further, according to the present invention, the minimum current target phase difference can be extracted from the input operating torque by the phase difference extracting means without searching. Therefore, it is not necessary to change the target phase difference that minimizes the power consumption described in the background art during operation, that is, to increase/decrease the phase current to search for the minimum point of power consumption, and It is possible to stably operate the air conditioner without generating

It is a block diagram showing an example of an air harmony machine provided with a motor control device by the present invention. It is an equation for calculating the torque. It is explanatory drawing explaining a phase difference table. 3 is a graph of phase difference-motor phase current characteristics for explaining the principle of the present invention. It is a block diagram which shows the conventional motor control apparatus.

  Hereinafter, embodiments of the present invention will be described in detail as examples based on the accompanying drawings.

FIG. 1 is a block diagram showing an air conditioner 1 according to the present invention.
The air conditioner 1 includes an outdoor unit 40 to which a three-phase AC power source 2 is connected, and an indoor unit 50 that is communicatively connected to the outdoor unit 40.

  Further, the outdoor unit 40 includes a motor control device 16 to which the AC power source 2 is connected, a compressor 7 having a motor 7a therein, a flow meter 17, a four-way valve 8, a heat exchanger 9, and an electronic expansion device. A valve 10, a first operation valve 11, a second operation valve 12, a discharge pressure sensor 13, and a suction pressure sensor 14 are provided. The discharge pressure sensor 13 outputs the detected pressure as a discharge pressure signal, and the suction pressure sensor 14 outputs the detected pressure as a suction pressure signal. Further, the flow meter 17 measures the flow rate of the refrigerant and outputs it as a flow rate signal. The motor 7a has a winding (not shown) inside, and the rotor inside the motor 7a rotates when a motor phase current flows through this winding.

  A discharge port of the compressor 7 is a discharge pipe 15a via a flow meter 17, and a suction port thereof is a gas pipe 15b, which are connected to the four-way valve 8, respectively. Further, the four-way valve 8 is connected to the heat exchanger 9, the electronic expansion valve 10, the first refrigerant pipe 15c, and the second operation valve 12 by sequential piping. Further, the four-way valve 8 is connected to the first operation valve 11 by the second refrigerant pipe 15d. The outdoor unit 40 and the indoor unit 50 are connected to their respective refrigerant circuits via the first operation valve 11 and the second operation valve 12. On the other hand, the discharge pressure sensor 13 is provided in the discharge pipe 15a, and the suction pressure sensor 14 is provided in the gas pipe 15b.

  On the other hand, the motor control device 16 rectifies the AC power supply 2 and outputs a DC voltage, the smoothing capacitor 4 connected to the positive output terminal and the negative output terminal of the rectifier 3, and the positive output terminal of the rectifier 3. Each of the negative output terminals is connected to the input terminal, and the input DC voltage is converted to supply a three-phase AC voltage (motor phase voltage) to the motor 7a and the amplitude of the motor phase voltage applied to the motor 7a is changed. An inverter unit 5 that controls and drives the motor 7a in a sine wave; a current sensor 6 that detects a motor phase current flowing in one of the three windings of the motor 7a and outputs it as a motor phase current signal; An outdoor unit controller 20 that controls the entire outdoor unit including the control device 16 is provided.

  The outdoor unit control unit 20 includes a torque calculation unit (torque calculation unit) 21, a phase difference control unit 22, and a target phase difference setting unit (target phase difference setting unit) 30. In the motor control device 16, the torque of the motor 7a is determined by the pressure (load) for compressing the refrigerant in the compressor 7. Then, the inverter unit 5 needs to rotate the motor 7a with a torque corresponding to this load. On the other hand, the torque of the motor 7a fluctuates due to fluctuations in the air conditioning load related to the refrigerant circuits of the outdoor unit 40 and the indoor unit 50.

  Specifically, when the set temperature and the room temperature largely deviate from each other and the air conditioning load is large, the air conditioner 1 performs control so as to reduce the deviation. Therefore, the air conditioner 1 rotates the compressor 7 at high speed to increase the pressure of the compressor 7. That is, the load on the compressor 7 increases. On the other hand, the air conditioner 1 reduces the pressure of the compressor 7 by rotating the compressor 7 at a low speed when the difference between the set temperature and the room temperature is small and the air conditioning load is small. As a result, the load on the compressor 7 is reduced. Since the load (pressure) of the compressor 7 is the torque for the motor 7a, the torque varies depending on the condition of the air conditioning load as described above.

  In order to obtain this fluctuating torque, the torque calculation unit 21 calculates a torque value during operation of the motor 7a based on the input motor rotation speed, discharge pressure signal, suction pressure signal, and flow rate signal, and calculates the operating torque value. Is output to the target phase difference setting unit 30. The method of calculating the torque value will be described in detail later.

  The target phase difference setting unit 30 extracts a target phase difference (minimum current target phase difference described later) from the input operating torque value using a table stored inside and outputs it to the phase difference control unit 22. The phase difference control unit 22 outputs an inverter control signal to the inverter unit 5 in accordance with the input motor phase current signal and the target phase difference, and also outputs the motor rotation speed, which is the rotation speed of the motor 7a, to the torque calculation unit 21. The phase difference control unit 22 internally monitors the rotation speed in order to control the motor 7a, and outputs the value of this rotation speed as the motor rotation speed.

  The target phase difference setting unit 30 extracts a minimum current target phase difference, which is a phase difference corresponding to the input operating torque value, and outputs the minimum current target phase difference, and a minimum current target phase difference. Is temporarily stored, and the phase difference storage unit 31 is provided for outputting the already stored minimum current target phase difference to the phase difference control unit 22 as the target phase difference until the minimum current target phase difference is input. ing.

  Next, the torque calculation unit 21 will be described in detail. As a calculation formula for calculating the value of the torque during operation of the compressor that circulates the refrigerant, for example, formula 1 of FIG. 2 is known. Where Tr: compressor torque [kgf·m], Pd: discharge pressure [kgf/square centimeter], Ps: suction pressure [kgf/square centimeter], k, m: constant, Vc: compressor discharge amount [cc]. .. Here, Vc can be calculated from Gr: refrigerant flow rate [kg/h], Nc: compressor rotation speed [rpm], and time t [Sec], so that the torque value can be finally obtained by Equation 2 in FIG. it can. It should be noted that other formulas for obtaining the torque are known and may be used.

Since the value of the torque of the compressor largely depends on the discharge pressure, the formula 1 may be simplified by simply setting Vc: the compressor discharge amount in the formula 1 by multiplying the discharge pressure by a coefficient.
In this way, the torque calculation unit 21 calculates the compressor torque in units of [kgf·m]. On the other hand, since the phase difference extracting unit 32 handles the operating torque in the unit of [N·m], the torque calculating unit 21 multiplies the calculation result by the unit conversion coefficient: 9.81 to calculate the operating torque in the unit of [N·m]. It is output as an operating torque value after conversion into

  As described above, the pressure for compressing the refrigerant in the compressor 7 becomes the load of the motor 7a, and the inverter unit 5 needs to rotate the motor 7a with the torque corresponding to this load. The phase difference extraction unit 32 determines the operating torque value that is the value of the torque [unit: N·m] applied to the motor 7a during operation of the compressor 7 and the minimum value that minimizes the motor phase current when the operating torque value is reached. The phase difference table shown in FIG. 3 in which the current target phase differences (degrees) are stored in association with each other is provided. When the operating torque value is input, the phase difference extracting unit 32 extracts the minimum current target phase difference corresponding to the operating torque value from this phase difference table and outputs it to the phase difference storage unit 31. For example, when the operating torque value: 10 [N·m] is input, the phase difference extracting unit 32 refers to the phase difference table and extracts the minimum current target phase difference: 11.0 degrees.

  Next, a method of creating the phase difference table will be described. When creating the phase difference table, the values in the table are determined based on the characteristics obtained experimentally in advance. Therefore, in the present invention, the air conditioner 1 of FIG. 1 is used as an experimental machine. However, since the phase difference table of the phase difference extraction unit 32 is incomplete, the value of the minimum current target phase difference is manually changed.

  In FIG. 4, the minimum current target phase difference is manually changed while the torque value of the motor 7a is fixed by fixing the load of the compressor 7 applied to the motor 7a, and the motor phase current at that time is measured. It is plotted as a thick solid line. The torque value was set to three values of 10 N·m, 20 N·m, and 30 N·m, and the motor phase current was measured. As a result, there was a phase difference in which the motor phase current was changed by changing the phase difference among these three values, and the motor phase current was always the minimum for each torque value.

  For example, when the torque value is 10 N·m and the phase difference is 11°, the motor phase current is 29.2 amperes, and when the torque value is 20 N·m, the phase difference is 23° and the motor phase current is 23°. Is 39.5 amps and the torque value is 30 N·m, the motor phase current is 50.1 amps when the phase difference is 36°, which is the smallest motor phase current among the torque values (minimum current). Has become. Further, as the torque value increases, the phase difference that produces this minimum current increases.

  Further, it was confirmed that the locus plotting the minimum phase current at the torque values was a straight line even when the measured torque values were other than the three torque values. Then, the line connecting the point where the motor phase current is 29.2 amperes when the torque value is 10 N·m and the point where the motor phase current is 50.1 amperes when the torque value is 30 N·m is a broken line. It shows with. The graph shown by this broken line is called the minimum current phase difference characteristic line. It should be noted that the point where the motor phase current is 39.5 amperes when the torque value is 20 N·m exists on this minimum current phase difference characteristic line.

  The minimum current at each torque value and the phase difference at that time exist on this minimum current phase difference characteristic line. Since the three torque values and the phase difference that is the minimum current at each torque value are already known, the possible torque values between these torque values and the position indicating the minimum current at this torque value are shown. What is calculated and stored so as to interpolate the value of the phase difference is the phase difference table of FIG. It should be noted that a more accurate phase difference table can be created by actually measuring the minimum current phase difference characteristic at a large number of torque values instead of calculation.

  The outdoor unit control unit 20 controls the inverter unit 5 to generate the required torque even when various torques are required based on the phase difference table. At this time, the target phase difference setting unit 30 outputs the minimum current target phase difference at which the motor phase current becomes the minimum current in the torque to the phase difference control unit 22, and the phase difference control unit 22 drives the inverter unit 5 accordingly. To do. That is, it is possible to reduce the current flowing through the IPM (not shown) in the inverter unit 5 regardless of the value of the load of the motor 7a. Further, the motor phase current flowing through the motor 7a can be reduced at the same time.

  As described above, the motor control device 16 according to the present invention sets the target phase difference setting unit 30 that outputs the target phase difference (minimum current target phase difference) to the phase difference control unit 22 and the value of the operating torque of the motor 7a. A torque calculation unit 21 for detecting is provided. Then, the target phase difference setting unit 30 is experimentally obtained in advance and extracts the minimum current target phase difference that minimizes the motor phase current of the motor 7a for each value of the operating torque, based on the calculated value of the operating torque. A phase difference extraction unit 32 for outputting the output is provided.

Therefore, even when the torque value of the compressor 7 changes variously depending on the load state, it is possible to perform control with the motor phase current reduced. Therefore, with respect to the components such as the IPM forming the inverter unit 5, inexpensive components having a small rated current can be adopted. As a result, the cost of the motor control device 16 can be reduced.
Moreover, since the target phase difference is not changed in order to search for the target phase difference that minimizes the power consumption described in the background art, the air conditioner 1 can be stably operated. Further, since the current for driving the compressor 7 can be reduced, it is possible to prevent the heat generation of the compressor 7 and the demagnetization of the permanent magnet provided in the motor 7a to be prevented, thereby improving the reliability.

Although the phase difference extraction unit 32 extracts the minimum current target phase difference from the operating torque using the phase difference table in the present embodiment, the present invention is not limited to this, and the minimum current phase difference characteristic line is used as a calculation formula. For example, it may be stored in the phase difference extraction unit 32, the input operating torque value may be calculated, and the calculation result may be output as the minimum current target phase difference. For example, when the value of the operating torque and the minimum current target phase difference are expressed by the equation in the phase difference table of FIG. 3, Tr: operating torque [N·m], a: slope of the minimum current phase difference characteristic line (constant: 1. 25), b: offset value (constant 6), Ph: minimum current target phase difference [degree], Ph=a(Tr-b)+b.
Further, in the present embodiment, the phase current of the motor 7a is detected by the current sensor 6, but the present invention is not limited to this, and a shunt resistor is provided immediately before the input terminal to which the power source of the inverter unit 5 is input. The phase current value obtained based on the bus current detected by the resistance may be used.

1 Air Conditioner 2 AC Power Supply 3 Rectifier 4 Smoothing Capacitor 5 Inverter Section 6 Current Sensor 7 Compressor 7a Motor 8 Four-way Valve 9 Heat Exchanger 10 Electronic Expansion Valve 11 First Operation Valve 12 Second Operation Valve 13 Discharge Pressure Sensor 14 Intake Pressure sensor 15a Discharge pipe 15b Gas pipe 15c First refrigerant pipe 15d Second refrigerant pipe 16 Motor controller 17 Flow meter 20 Outdoor unit controller 21 Torque calculator (torque calculator)
22 Phase Difference Control Section 30 Target Phase Difference Setting Section (Target Phase Difference Setting Means)
31 phase difference storage section 32 phase difference extraction section (phase difference extraction means)
40 Outdoor unit 50 Indoor unit

Claims (2)

A motor control device for driving a motor by controlling a phase difference between a motor phase current and a motor phase voltage by an amplitude of the motor phase voltage,
The motor control device,
A phase difference control unit that detects the motor phase current and controls the amplitude of the motor phase voltage so that the phase difference between the motor phase current and the motor phase voltage becomes a target phase difference,
A target phase difference setting unit that outputs the target phase difference to the phase difference control unit,
The target phase difference setting means,
The minimum current target phase difference that minimizes the motor phase current is stored in advance for each value of the operating torque that is the torque during operation of the motor, and corresponds to the value of the operating torque input during operation of the motor. A motor control device, comprising: a phase difference extracting means for outputting the minimum current target phase difference as the target phase difference. The motor control device, a motor driven by the motor control device, a compressor provided with the motor, and a torque calculation means for calculating the value of the operating torque of the motor and outputting the value to the phase difference extraction means; A discharge pressure sensor for detecting the discharge pressure of the compressor,
The air conditioner, wherein the torque calculating means calculates a value of the operating torque based on the discharge pressure.

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