JP4527596B2 - MOTOR CONTROL DEVICE AND ELECTRIC DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to a motor control device for an electric device driven by a motor such as a washing machine and a washing / drying machine.

  In an electric device such as a washing machine or a washing / drying machine, a permanent magnet type synchronous motor having a permanent magnet in a rotor is used as a motor for rotating a washing tub. In the vector control inverter for this motor, a d-axis current command and a q-axis current command are created from the torque command and the rotational speed, and a gate signal is generated so that a necessary voltage can be obtained from these commands.

  Here, when the rotational speed of the motor is high, it is common to set a negative d-axis current command and perform field-weakening control to reduce the counter electromotive force generated with the rotation of the motor. With this control, even if the motor rotates at high speed and the back electromotive force increases, the voltage applied to the motor increases. Therefore, the power shortage due to the counter electromotive force can be compensated, and the rotation speed of the motor can be increased.

There are a method of calculating and calculating a d-axis current command and a method of referring to a table. In the calculation method, since the calculation of the d-axis current command is complicated, a high capacity is required for an arithmetic processing unit such as a microcomputer. As a result, it is necessary to use an expensive arithmetic processing unit, which increases the cost. On the other hand, in the method of referring to the table, the amount of calculation for generating the d-axis current command can be reduced, and the load on the arithmetic processing device is reduced. As a result, the arithmetic processing device can be used even if it is inexpensive and has low performance, and cost reduction can be expected. For example, Patent Documents 1 and 2 disclose motor control devices using such a table.
JP 2000-228892 A JP 2000-32799 A

  When the field weakening control is performed, the d-axis current command needs to be set to a value corresponding to the rotation speed and the DC voltage. As a table to be referred for this control, a two-axis table of rotation speed and DC voltage as shown in FIG. 8 is created. The table is stored in a non-volatile memory such as a flash memory. If the amount of data is large as shown in FIG. 8, a large-capacity memory is required, which causes an increase in cost.

  Therefore, the memory usage can be saved by using a one-axis table corresponding to only the rotation speed as shown in FIG. However, when the DC voltage fluctuates, problems such as efficiency deterioration and inability to drive at a desired rotational speed occur. Further, even if a uniaxial table corresponding to only the DC voltage as shown in FIG. 10 is used, the memory usage can be saved, but if the rotational speed changes, the efficiency deteriorates or the desired rotational speed is increased. It becomes impossible to drive. If a plurality of tables are used for each DC voltage or for each rotation speed, appropriate field-weakening control can be performed, but it takes time to search the table and the memory capacity increases.

  SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a low-cost motor control device that can always realize high-efficiency field-weakening control at a desired rotational speed even when the DC voltage fluctuates.

  The present invention is a motor control device that supplies power from a power source to a motor through an inverter circuit, a current determination unit that determines a current command based on the number of rotations of the motor, and a voltage that calculates a voltage command from the current command The rotation unit includes a calculation unit, a conversion unit that generates a PWM signal based on the voltage command and outputs the PWM signal to the inverter circuit, and a DC voltage detection unit that detects a DC voltage supplied from the power source to the inverter circuit. A table in which a current command for the number is set is provided, and the current determination unit corrects the rotation speed in accordance with a change in the DC voltage, and determines the current command with reference to the table.

  The table has a current command set for the rotational speed at the reference DC voltage. The current determination unit corrects the rotational speed based on the reference DC voltage and the detected DC voltage. Then, with reference to the table, a current command corresponding to the corrected rotation speed is determined, and the motor is driven and controlled based on this current command. As a result, even if the DC voltage supplied to the inverter circuit fluctuates, the motor can be driven to rotate at a desired rotational speed, and field-weakening control can be performed reliably.

  As a specific correction of the rotation speed, the current determination unit corrects the rotation speed to be larger when the detected DC voltage is smaller than the reference DC voltage, and rotates when the DC voltage is larger than the reference DC voltage. Correct so that the number is smaller. That is, the greater the difference between the reference DC voltage and the detected DC voltage, the greater the amount of rotation speed correction.

  A threshold value for the corrected rotation speed is set, and when the corrected rotation speed exceeds the threshold value, the current command is set to a fixed value. Depending on the number of revolutions, the current command may not be required or the current command may be limited from the viewpoint of safety. Based on this, the threshold is set.

  An upper limit threshold is set as the threshold, and a minimum limit value is determined as a fixed value of the current command with respect to the upper limit threshold. In addition, a lower limit threshold is set, and a fixed value of the current command with respect to the lower limit threshold is set to zero. Note that not only both the upper threshold and the lower threshold may be set, but either one may be set. Thus, the data amount of the table can be reduced by setting the current command to a fixed value according to the rotation speed threshold value.

  Then, an AC power source is used as a power source, an AC voltage from the AC power source is converted into a DC voltage and supplied to an inverter circuit, and an AC voltage detecting unit for detecting the AC voltage is provided instead of the DC voltage detecting unit. The DC voltage is calculated from the detected AC voltage.

  For example, the direct current voltage may not be directly detected due to the circuit layout or measurement components. Since the DC voltage supplied to the inverter circuit and the AC voltage before conversion of the DC voltage have a corresponding relationship, the fluctuation of the DC voltage is also the fluctuation of the AC voltage. Therefore, even if the DC voltage cannot be detected, it is only necessary to detect the AC voltage, and the motor can be driven and controlled with reference to the table by correcting the rotational speed as described above.

  When the electric apparatus includes the motor control device, the field weakening control of the motor can be performed using a table. In particular, when the present invention is applied to a washing machine or a washing / drying machine as an electric device, it is necessary to rotate the motor at a high speed as in a dehydrating operation.

  According to the present invention, when controlling a motor using a table, it is not necessary to prepare a plurality of tables or a table with a lot of data, and only one table is required, and the memory usage is reduced. Can reduce costs.

  A schematic configuration of a motor driving device using the motor control device of the present embodiment is shown in FIG. The motor driving device is mounted on an electric device that operates with electric power from an AC power supply, and drives and controls a motor 1 that is a three-phase permanent magnet type synchronous motor by inverter control by an inverter circuit 2. The inverter circuit 2 is supplied with three-phase voltage signals Vu *, Vv * and Vw * from a microcomputer 3 which is a motor control device. The inverter circuit 2 applies an applied voltage to the motor 1 based on this signal. Output. The converter circuit 4 forms a DC power supply from the AC power supply 5 and supplies power to the inverter circuit 2.

  A rotor position detector 6 is provided to detect the rotation speed of the motor 1. The rotor position detection unit 6 detects the rotor position of the motor 1 using a hall sensor and outputs a rotor position signal to the microcomputer 3. Further, a DC voltage detector 7 that detects a DC voltage supplied to the inverter circuit 2 is provided. The DC voltage detector 7 is provided between the converter circuit 4 and the inverter circuit 2, detects a DC voltage from the voltage applied to both ends of the resistor, and outputs a DC voltage signal Vdc to the microcomputer 3.

  The microcomputer 3 calculates the three-phase voltage signals Vu *, Vv *, and Vw * according to the program using the rotor position signal from the rotor position detector 6 and the DC voltage signal Vdc from the DC voltage detector 7. These signals are output to the inverter circuit 2.

  The microcomputer 3 generates a PWM signal based on the current command, a current determination unit that determines a current command based on the rotational speed of the motor 1, a voltage calculation unit that calculates a voltage command from the current command, and generates a PWM signal. A converter that outputs a signal to the inverter circuit 2. Specifically, as shown in FIG. 2, the motor rotation number calculation unit 11, the subtraction unit 12, the q-axis current calculation unit 13, the reference rotation number correction unit 14, the d-axis current calculation unit 15, and the two-phase voltage calculation unit 16. A d-axis current table 17, an angle calculation unit 18, and a two-phase three-phase voltage conversion unit 19. The current determination unit includes a motor rotation number calculation unit 11, a subtraction unit 12, a q-axis current calculation unit 13, and a d-axis current calculation unit 15. The voltage calculation unit includes a two-phase voltage calculation unit 16, and the conversion unit includes a two-phase three-phase voltage conversion unit 19.

  The reference rotation speed correction unit 14 corrects the detected rotation speed according to the fluctuation of the DC voltage, and outputs the corrected rotation speed to the d-axis current calculation unit 15. The d-axis current calculation unit 15 determines a d-axis current command with reference to the d-axis current table 17 for the corrected rotational speed. In addition, each other part is a well-known thing as described in patent document 1, Unexamined-Japanese-Patent No. 2001-204200, etc.

  As shown in FIG. 3, the d-axis current table 17 has a d-axis current command with respect to the rotational speed of the motor. The d-axis current command in this table is d-axis current command data determined in advance for each rotation speed at the reference DC voltage. For example, the reference DC voltage is set to 80 V, and a table is created by obtaining a d-axis current command capable of realizing high-efficiency field-weakening control at a desired rotational speed by experiment or simulation for each motor rotational speed.

  Next, the control operation by the microcomputer 3 will be described. As shown in the flowchart of FIG. 4, the rotational speed of the motor 1 is calculated by the motor rotational speed calculator 11 based on the rotor position signal (S1). The motor rotation number ω is output from the motor rotation number calculation unit 11, and the subtraction unit 12 calculates a deviation Δω between the calculation motor rotation number ω and the target command motor rotation number ω * (S 2). This deviation Δω is input to the q-axis current calculation unit 13. The q-axis current calculation unit 13 determines the q-axis current command Iq from Δω (S3).

  Further, the reference rotation speed correction unit 14 corrects the arithmetic motor rotation speed ω according to the DC voltage Vdc detected by the DC voltage detection unit 7, and determines the reference rotation speed ωL (S4). That is, when the detected DC voltage Vdc is larger than the standard DC voltage, the reference rotational speed ωL of the d-axis current command is corrected so as to be small, and when the detected DC voltage Vdc is smaller than the standard DC voltage, It correct | amends so that rotation speed (omega) L may become large. The d-axis current calculation unit 15 refers to the data in the d-axis current table 17 and determines the d-axis current command Id based on the corrected rotation speed ωL (S5).

  The d-axis current calculation unit 15 determines a d-axis current command corresponding to the reference rotation speed ωL input from the reference rotation speed correction unit 14 and outputs the d-axis current command to the two-phase voltage calculation unit 16. The two-phase voltage calculation unit 16 calculates the q-axis voltage command Vq and the d-axis voltage command Vd based on the q-axis current command Iq, the d-axis current command Id, and the calculation motor rotation speed ω (S6).

  Further, the angle calculator 18 calculates the rotation angle θ from the rotor position signal (S7). The two-phase three-phase voltage converter 19 converts the q-axis voltage command Vq and the d-axis voltage command Vd into three-phase voltages Vu, Vv, and Vw based on the rotation angle θ (S8). The three-phase voltages Vu, Vv, Vw are output to the inverter circuit 2 (S9).

Here, in the correction of the rotational speed, the reference rotational speed ωL is calculated by the following equation according to the detected value of the DC voltage Vdc.
ωL = ω + k × (80−Vdc) (1)
k is a coefficient for calculation. If the motor has the same characteristics as the motor using the table of FIG. 8, k = 1 may be used.

  When the rotational speed of the arithmetic motor is 100 rpm and the DC voltage is 60 V, the d-axis current command Id = −6 when the table of FIG. 9 shown in the prior art is used. When field weakening control is performed according to the d-axis current command, the motor 1 cannot obtain a sufficient torque, resulting in problems such as inefficiency and inability to drive at a desired rotational speed. However, the rotation speed after correction based on the equation (1) is 120 rpm, and referring to the d-axis current table 17 in FIG. 3, the d-axis current command Id = −8. Even if the DC voltage decreases from the reference DC voltage 80V to 60V, the number of revolutions of the motor 1 can be increased and sufficient torque can be obtained. Therefore, it is possible to drive at a desired rotational speed without deteriorating the efficiency.

  By the way, when the rotational speed is low, such as when the motor 1 is started, the field current becomes zero. In the table 17 shown in FIG. 3, there is a rotation region in which the reference rotation speed ωL is low and a d-axis current command is not required. That is, an area where the d-axis current command Id = 0 is included in the table 17.

  Further, in order to avoid an excessive current flowing through the inverter circuit 2 to deteriorate or destroy the circuit, the minimum value of the d-axis current command is limited to a predetermined value, for example, −10. The table 17 shown in FIG. 3 has a rotation region in which the reference rotation speed ωL is high and the d-axis current is limited to the minimum value. That is, the table 17 includes an area where the d-axis current command Id = −10.

  Therefore, a threshold for the corrected rotation speed is set. The threshold includes an upper limit threshold ω1 and a lower limit threshold ω2, and the value of the d-axis current command is a fixed value for each threshold. The fixed value of the lower threshold is d-axis current command Id = 0. The fixed value of the upper limit threshold is d-axis current command Id = −10.

  For this reason, the d-axis current table 17 stores d-axis current command data when the lower limit threshold is 40 rpm, as shown in FIG. Further, when the upper limit threshold is 140 rpm, d-axis current command data when lower than 140 rpm is stored.

  A control operation when this table 17 is used is shown in FIG. The basic operation is the same as that shown in FIG. The d-axis current calculation unit 13 determines whether or not the reference rotation speed ωL is larger than the threshold value ω1 (S10). If it is equal to or less than the threshold value ω1, the reference rotational speed ωL = ω1 is set (S11).

  When the reference rotational speed ωL is larger than the threshold ω1, it is determined whether or not the reference rotational speed ωL is smaller than the threshold ω2 (S12). If it is equal to or greater than the threshold ω2, the reference rotational speed ωL = ω2 is set (S13). When the reference rotational speed ωL is larger than the threshold ω1 and smaller than the threshold ω2, the reference rotational speed ωL is used as it is. Current command data for the reference rotational speed ωL is read from the d-axis current table 17 to determine the d-axis current command Id (S5).

  By using such a table 17, the amount of data stored in the nonvolatile memory can be reduced. Therefore, it is possible to use a memory with a small storage capacity, and the cost can be reduced.

  In the motor drive device in the above embodiment, a direct current voltage is directly detected. Instead of the DC voltage detector 7, an AC voltage detector 20 may be provided as shown in FIG. The AC voltage detection unit 20 is provided between the AC power supply 5 and the converter circuit 4 and detects an AC voltage from the AC power supply 5. The converter circuit 4 rectifies the input AC voltage and outputs it as a DC voltage. Therefore, there is a correspondence between the magnitude of the input AC voltage and the magnitude of the output DC voltage. The microcomputer 3 can estimate a DC voltage from the detected AC voltage. Then, the rotational speed used when referring to the d-axis current table 17 is corrected according to the estimated DC voltage. Other configurations are the same as those in the above-described embodiment, and thus are omitted.

  Next, the motor drive device of this embodiment is applied to a washing machine. The washing machine is a direct drive system in which the motor 1 is directly attached to the washing tub, and the number of times of the motor 1 directly rotates the washing tub. The washing machine performs a washing operation and a rinsing operation in which the laundry tub is rotated at a low speed to wash the laundry, and a dehydration operation in which the laundry tub is rotated at a high speed to perform dehydration.

  In the dehydration operation, it is required to reduce moisture by centrifugation in order to dry the laundry quickly. Therefore, it is necessary to rotate the washing tub at high speed, and the motor is driven and controlled at the designated motor rotation speed. At this time, field weakening control is performed so that sufficient torque is secured and stable rotation driving can be performed.

  When the command motor rotation speed ω * is input to the microcomputer 3 in the dehydration operation, the microcomputer 3 drives and controls the motor 1 based on the command motor rotation speed ω *. The microcomputer 3 performs field-weakening control while referring to the d-axis current table 17 according to the fluctuation of the DC voltage. As a result, the motor drive device rotates the washing tub with high efficiency at the command motor rotational speed ω * even when the DC voltage fluctuates due to fluctuations in the load applied to the motor 1 along with the rotation of the washing tub. be able to.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. You may apply said motor control apparatus to the electric equipment which uses synchronous motors, such as an electric vehicle, an elevator, and a pump. In addition, although the upper and lower thresholds are set for the corrected number of revolutions, only one of the thresholds may be set. Even if a d-axis current table is created in accordance with this, the amount of data can be reduced. Can be reduced.

The block diagram which shows schematic structure of the motor drive device of this invention The block diagram which shows schematic structure of the motor control apparatus used for a motor drive device The figure which shows the table of the rotation speed of this embodiment, and d-axis current command Microcomputer control operation flowchart The figure which shows the table of rotation speed and d-axis current command of other embodiment. Flow chart of control operation of microcomputer when using table of other embodiment The block diagram which shows schematic structure of the motor drive device of other embodiment. The figure which shows the table of the d-axis current command with respect to the conventional rotation speed and DC voltage The figure which shows the table of the conventional rotation speed and d-axis current command The figure which shows the table of the conventional DC voltage and d-axis current command

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Inverter circuit 3 Microcomputer 4 Converter circuit 5 AC power supply 6 Rotor position detection part 7 DC voltage detection part 11 Motor rotation speed calculation part 12 Subtraction part 13 q-axis current calculation part 14 Reference rotation speed correction part 15 d-axis current calculation Unit 16 two-phase voltage calculation unit 17 d-axis current table 18 angle calculation unit 19 two-phase three-phase voltage conversion unit 20 AC voltage detection unit

Claims (9)

A motor control device that supplies power from a power source to a motor through an inverter circuit, a current determination unit that determines a current command based on the number of rotations of the motor, a voltage calculation unit that calculates a voltage command from the current command, A current command for the rotational speed, comprising: a converter that generates a PWM signal based on the voltage command and outputs the PWM signal to the inverter circuit; and a DC voltage detector that detects a DC voltage supplied from the power source to the inverter circuit. A motor control device is provided, wherein the current determination unit corrects the rotation speed in accordance with a change in the DC voltage, and determines a current command with reference to the table. The table holds a current command set for the rotational speed at the reference DC voltage, and the current determining unit corrects the rotational speed based on the reference DC voltage and the detected DC voltage. The motor control device according to claim 1, characterized in that: The current determining unit corrects the rotational speed to be increased when the detected DC voltage is smaller than the reference DC voltage, and corrects the rotational speed to be decreased when the DC voltage is larger than the reference DC voltage. The motor control device according to claim 2. 4. The motor control device according to claim 2, wherein a threshold value for the corrected rotational speed is set, and the current command is set to a fixed value when the corrected rotational speed exceeds the threshold value. The motor control device according to claim 4, wherein an upper limit threshold value for the rotation speed after correction is set, and a minimum limit value is determined as a fixed value of the current command with respect to the upper limit threshold value. 5. The motor control device according to claim 4, wherein a lower limit threshold value of the rotation speed after correction is set, and a fixed value of the current command with respect to the lower limit threshold value is set to zero. An AC power source is used as a power source, an AC voltage from the AC power source is converted into a DC voltage and supplied to an inverter circuit, and instead of a DC voltage detection unit, an AC voltage detection unit for detecting the AC voltage is provided, The motor control device according to claim 1, wherein a DC voltage is calculated from the detected AC voltage. An electric apparatus comprising the motor control device according to claim 1, wherein field weakening control of the motor is performed using a table. 9. The electric device according to claim 8, wherein the electric device is a washing machine or a washing / drying machine.

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