JP5195884B2 - Compressor driving method and compressor driving device - Google Patents

Description

  The present invention relates to a compressor driving method and apparatus, and more particularly, to a compressor driving method and apparatus for controlling a synchronous motor by an inverter and driving the compressor by the synchronous motor.

  The compressor is used as a drive source for various devices including an air conditioner.

  As a device for driving the compressor, a synchronous motor is conventionally controlled by an inverter and the compressor is driven by the synchronous motor, and the rotational position of the rotor of the synchronous motor (hereinafter referred to as the rotor position). OCP for protecting a power element such as an inverter when the motor current becomes excessive, and a position detection unit for detecting the position of the rotor, and an inverter control unit for controlling the voltage of the inverter based on the detected rotor position. Some have been proposed.

  Here, a sensor such as a Hall element may be used as the position detection unit. However, when a synchronous motor is incorporated in the compressor, a position detection unit that does not use a sensor, for example, an inverter. A position detector that detects the rotor position by detecting the motor-induced voltage during the non-energization period, or the rotor position by detecting the neutral point voltage of the stator winding of the synchronous motor. It is preferable to employ a position detection unit that detects.

  If the compressor driving device having the above-described configuration is employed, the inverter can be controlled based on the rotor position to operate the synchronous motor and drive the compressor.

JP-A-11-332298 JP-A-8-103093 JP-A 63-87195

  When the above compressor drive unit is used, when the load becomes excessive and the motor current becomes excessive, the OCP unit generates power element protection (trip) such as an inverter and stops the compressor. It will be.

  When a trip occurs, restart is performed after a waiting time of several minutes in consideration of reliable start-up, compressor protection, and the like, so that inconvenience occurs due to the stop of the compressor.

  For example, if the compressor is an air conditioner compressor, the air conditioning operation cannot be performed during the compressor stop period, so that the room temperature fluctuates from the target temperature, causing discomfort. End up.

  Moreover, in the compressor for an air conditioner, since the refrigerant gas is compressed in a normal operation state, the operation is performed only under a load state less than the maximum load assumed by the compression of the refrigerant gas. Therefore, trips are not expected to occur. However, in actuality, the refrigerant may be sucked in a liquid state. In this case, liquid compression is performed, so that the load becomes excessive and a trip occurs. As a result, the above inconvenience occurs.

  The present invention has been made in view of the above problems, and provides a compressor driving method and apparatus capable of reliably preventing the occurrence of a trip even when the load becomes excessive. It is aimed.

  In the compressor driving method according to claim 1, the load is excessive in the compressor driving method in which the synchronous motor (7) is controlled by the inverter (6) and the compressor (8) is driven by the synchronous motor (7). In some cases, the inverter (6) is controlled so that the motor current does not exceed the predetermined range, and the current phase is maximized in response to the motor current approaching or becoming equal to the upper limit value defining the predetermined range. It is close to the phase where torque can be generated.

  In the compressor driving device according to claim 2, the load is excessive in the compressor driving device in which the synchronous motor (7) is controlled by the inverter (6) and the compressor (8) is driven by the synchronous motor (7). In some cases, the inverter control means (3), (4), (10), (11), and (12) for controlling the inverter (6) so that the motor current does not exceed a predetermined range includes the inverter control means (2) ( In 12), in response to the motor current approaching or becoming equal to the upper limit value defining the predetermined range, the current phase is brought close to a phase capable of generating the maximum torque.

  According to the compressor driving method of claim 1, in response to the motor current approaching or becoming equal to the upper limit value defining the predetermined range, the current phase is brought close to a phase capable of generating the maximum torque. The motor torque can be utilized to the maximum.

  According to the compressor driving device of claim 2, the inverter control means can generate the maximum torque in the current phase in response to the motor current approaching or becoming equal to the upper limit value defining the predetermined range. Since the thing close | similar to a phase is employ | adopted, a motor torque can be utilized to the maximum.

It is a block diagram which shows the principal part of one embodiment of the compressor drive device of this invention. It is a figure which shows the change of the speed and motor current at the time of driving a compressor with the compressor drive device of FIG. It is a figure which shows the change of the speed and motor current at the time of driving a compressor with the conventional compressor drive device. It is a block diagram which shows the principal part of the other embodiment of the compressor drive device of this invention. It is a figure which shows an example of speed droop amount-command current characteristic. It is a block diagram which shows the principal part of the further another embodiment of the compressor drive device of this invention. It is a block diagram which shows the principal part of the further another embodiment of the compressor drive device of this invention. It is a figure which shows the torque-current phase characteristic of the permanent magnet motor which mounts | wears with a permanent magnet inside a rotor.

  Embodiments of a compressor driving method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a main part of one embodiment of a compressor driving apparatus of the present invention.

  This compressor drive device receives a speed command unit 1 that outputs a torque command by performing PI control based on a difference between a speed command given from outside and an actual speed, and a phase command and a torque command given from outside as inputs. The current command generator 2 that generates the current command and the current command are compared with a preset current upper limit value. When the current command exceeds the current upper limit value, the magnitude of the current command is maintained while maintaining the current phase. The current limiter 3 that is limited by the upper limit value, the current control unit 4 that performs PI calculation based on the difference between the current command from the current limiter 3 and the actual current, and outputs the voltage command, and the rotor command with the voltage command as an input Dq → three-phase converter 5 that performs dq → three-phase conversion based on (rotational position of the rotor of the synchronous motor) and outputs a three-phase voltage command, and three-phase based on the three-phase voltage command AC voltage is generated Voltage detection for detecting an actual voltage by performing an inverter 6 applied to the motor 7, a compressor 8 driven by the synchronous motor 7, and a three-phase voltage command as input and performing dead time compensation based on the rotor position Part 6a, current detection part 7a for detecting the actual current based on the rotor position with the motor current as input, and position detection part for detecting the rotor position (θ) and speed (ω) with the actual voltage and actual current as inputs 9, a constant K1 unit 10 that multiplies the current over value from the current limiter 3 by a constant K1, and a subtraction to obtain a corrected speed command by subtracting the output of the constant K1 unit 10 from a speed command given from the outside. Part 11.

  Also, on condition that the current command exceeds the current upper limit value, an I term limit command is supplied from the current limiter 3 to the speed control unit 1, and the internal state of the speed control unit 1 before the current command exceeds the current upper limit value is supplied. It is preferable to maintain the state (see the broken line in FIG. 1), and it is possible to prevent the PI calculation from diverging to the speed control unit 1. This configuration may be adopted in place of the constant k unit 10 and the subtraction unit 11, but both may be used together.

  The operation of the above compressor drive device is as follows.

  Based on the difference between the speed command given from the outside and the actual speed, the speed control unit 1 performs a PI calculation to generate a torque command, and based on the torque command and the phase command given from the outside, the current command generator 2 Generate directives.

  The current command is limited by the current limiter 3 only when the current command exceeds the current upper limit value.

  Next, based on the difference between the current command and the actual current, PI control is performed by the current control unit 4 to generate a voltage command, which is converted into a three-phase voltage command by the dq → three-phase conversion unit 5 and converted to the inverter 6. The three-phase AC voltage is supplied to the synchronous motor 7 to drive the synchronous motor 7, and the synchronous motor 7 drives the compressor 8.

  Further, during the above operation, the actual voltage is detected by the voltage detector 6a, the actual current is detected by the current detector 7a, and the position detector 9 based on the detected actual voltage and actual current. Since the rotor position (θ) and the speed (ω) can be detected (estimated), the voltage applied to the synchronous motor 7 is controlled based on the detected rotor position (θ), and synchronized to follow the speed command. The motor 7 can be driven, and thus the compressor 8 can be driven.

  In the case where the above action is performed, when the load becomes excessive due to liquid compression or the like, the motor current (actual current) is increased when the speed control unit 1 increases the torque command as the actual speed decreases. Will increase.

  When the motor current increases in this way and reaches the current upper limit value, the current command is limited so that the current limiter 3 does not exceed the current upper limit value. Therefore, the current command supplied to the current control unit 4 sets the current upper limit value. To prevent crossing over. Then, it is possible to prevent the motor current from becoming excessive by generating a voltage command by the current control unit 4 based on the current command thus restricted and controlling the inverter 6.

  That is, even when the load becomes excessive, the synchronous motor 7 can be controlled so that the motor current does not exceed the predetermined range, and the compressor 8 can be driven. In other words, the compressor stoppage due to power device protection (trip), standby time, and the like can be eliminated. When the compressor is an air conditioner compressor, the compressor stoppage is caused. A decrease in comfort can be prevented in advance.

  Furthermore, since the maximum value of the motor current can be reduced, the capacity of the inverter 6 can be reduced and the maximum current value of the synchronous motor 7 can be reduced, and the cost of the synchronous motor / inverter can be reduced.

  Next, a case where the compressor is driven by the compressor driving device of FIG. 1 to perform liquid compression, and a case where the compressor is driven by the conventional compressor driving device to perform liquid compression will be described.

  The speed and phase current when the compressor is driven by the compressor driving device of FIG. 1 are as shown in FIGS. 2A and 2B, respectively, and the compressor is driven by the conventional compressor driving device under the same conditions. The speed and phase current when driving were as shown in FIGS. 3A and 3B, respectively.

  In the compressor driving apparatus of FIG. 1, the peak value of the motor current was 39.6 A, and the maximum speed droop was −40.6 rps. On the other hand, in the conventional compressor driving device, the peak value of the motor current was 53.6 A, and the maximum speed droop was −33.1 rps.

  Therefore, by adopting the compressor driving device of FIG. 1, the peak value of the motor current can be greatly reduced, and the current capacity of the inverter 6 such as IGBT can be greatly reduced.

  Moreover, the reason why the maximum speed drooping in the compressor driving device of FIG. 1 is large is that the motor current is limited to limit application of excessive torque. In this case, since the motor torque is limited, it is possible to achieve protection of the compressor mechanism.

  FIG. 4 is a block diagram showing a main part of another embodiment of the compressor driving apparatus of the present invention.

  The compressor driving device is different from the compressor driving device of FIG. 1 in that a command current detector 12 is provided in place of the current limiter 3 to output a speed drooping command with a current command as an input and to supply the subtracting unit 11. It is only a point.

  The command current detector 12 has, for example, a speed droop amount-command current characteristic shown in FIG. 5 set in advance, and can output a corresponding speed droop amount using the command current as an input.

  When the compressor driving device of this configuration is adopted, when the current command is sufficiently smaller than the current upper limit value, the same operation as the compressor driving device of FIG. 1 when the current command is not limited is performed. The compressor can be driven.

  When the current command approaches the current upper limit value, a corresponding speed droop amount is output from the command current detector 12, and the speed command can be decreased (drooped) by the subtractor 11.

  As a result, the maximum value of the motor current can be reduced, the capacity of the inverter 6 can be reduced, and the maximum current value of the synchronous motor 7 can be reduced, and the cost reduction of the synchronous motor / inverter can be achieved.

  Further, in this compressor driving device, the speed drooping can be performed gradually near the current upper limit value, so that the abrupt current command limiting process as in the compressor driving device of FIG. 1 is eliminated, and the control is stabilized. can do.

  FIG. 6 is a block diagram showing a main part of still another embodiment of the compressor driving apparatus of the present invention.

  The compressor driving device is different from the compressor driving device of FIG. 1 only in that a command current detector 12 is further provided which outputs a speed drooping command with a current command as an input and supplies the command to the subtracting unit 11.

  The command current detector 12 has, for example, a speed droop amount-command current characteristic shown in FIG. 5 set in advance, and can output a corresponding speed droop amount using the command current as an input.

  When the compressor driving device having this configuration is adopted, when the current command gradually increases, the same action as in FIG. 4 is performed, and when the current command approaches the current upper limit value, the command current detector 12 responds. The speed droop amount to be output is output, and the speed command can be decreased (drooped) by the subtractor 11.

  However, if a sudden speed fluctuation occurs so that the current command value rapidly exceeds the current upper limit value, the compressor driving device of FIG. 4 may not be able to achieve a sufficient motor current reduction. is there.

  However, in this embodiment, since the current limiter 3 is also provided, even if such a rapid speed change occurs, the current limiter 3 limits the current command so that it does not exceed the current upper limit value. And sufficient motor current reduction can be achieved.

  FIG. 7 is a block diagram showing a main part of still another embodiment of the compressor driving apparatus of the present invention.

  The compressor driving device is different from the compressor driving device of FIG. 6 in that the command current detector 12 is preset with, for example, the speed droop amount-command current characteristic shown in FIG. The command current phase (command phase) is input and [command phase × {1− (speed droop command) / (speed droop command at current upper limit value)} + maximum torque current phase × { (Speed drooping command) / (Speed drooping command at current upper limit value)}] / 2 is calculated, the current phase is calculated, and the one supplied to the current command generator 2 is only adopted.

  The current upper limit value is set so that the speed drooping amount becomes a predetermined value at the current upper limit value.

  When the compressor driving device having this configuration is adopted, in addition to the operation of the compressor driving device of FIG. 6, the current phase from the command current detector 12 is supplied to the current command generator 2 to maximize the current phase. It is possible to approach the phase where torque can be generated. As a result, the motor torque can be utilized to the maximum.

  For example, since the torque-current phase characteristic of a permanent magnet motor having a permanent magnet mounted inside the rotor is given as shown in FIG. 8, the maximum torque current phase at the maximum current is stored, and By calculating the current phase based on this, the current phase can be brought close to a phase capable of generating the maximum torque, and the motor torque can be utilized to the maximum extent.

2 Current command generator 3 Current limiter 4 Current control unit 6 Inverter 7 Synchronous motor 8 Compressor 10 Constant K1 unit 11 Subtraction unit 12 Command current detector

Claims (2)

In the compressor driving method of controlling the synchronous motor (7) by the inverter (6) and driving the compressor (8) by the synchronous motor (7),
The inverter (6) is controlled so that the motor current does not exceed the predetermined range even when the load becomes excessive,
A compressor driving method in which a current phase is brought close to a phase capable of generating a maximum torque in response to a motor current approaching or becoming equal to an upper limit value that defines a predetermined range. In the compressor driving device that controls the synchronous motor (7) by the inverter (6) and drives the compressor (8) by the synchronous motor (7),
Including inverter control means (3) (4) (10) (11) (12) for controlling the inverter (6) so that the motor current does not exceed a predetermined range even when the load becomes excessive,
The inverter control means (2) (12) is adapted to bring the current phase closer to the phase capable of generating the maximum torque in response to the motor current approaching or becoming equal to the upper limit value defining the predetermined range. , Compressor drive.

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