JP5194779B2 - Synchronous motor control method and control apparatus - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a synchronous motor control method and control apparatus, and more particularly, a motor control method and motor control apparatus for controlling operation of a synchronous motor including a plurality of phase motor coils without using a rotor position sensor. It is about.

  As a prior art, there is an inverter control device disclosed in Patent Document 1 below. In this motor control device, based on the determinations of the rotational speed command means for setting the target rotational speed of the motor by an external operation command, the power supply state determination means for determining the supply state of AC power, and the power supply state determination means And a rotational speed determination means for limiting the rotational speed of the motor in preference to the rotational speed setting of the rotational speed command means.

Then, when the supply state of the AC power supply is unstable by determining the supply state of the AC power supply by the power supply state determination means and limiting the upper limit of the rotation speed with respect to the target rotation speed by the rotation speed command means, The stable operation of the motor is continued by avoiding frequent stoppage of the motor operation.
Japanese Patent No. 2007-97249

  However, the inverter control device of the above prior art is a method of continuing stable operation by limiting the upper limit rotational speed. However, when there is a sudden power supply voltage drop (instantaneous voltage drop) due to a lightning strike, etc. If the rotational speed is limited in accordance with the voltage drop, the steep rotational speed reduction instruction cannot be followed due to the mechanical characteristics of the rotor, and the unstable operation such as the rotor rotating oscillates. There is a problem that it stops out of operation. For this reason, means for designing the responsiveness according to the mechanical characteristics is used. However, the responsiveness is poor and the operation becomes unstable, and there is a problem that the operation is stepped out of the unstable operation and stops.

  The present invention has been made paying attention to such problems existing in the prior art, the purpose of which, even if an instantaneous voltage drop occurs, the motor does not become unstable operation, An object of the present invention is to provide a synchronous motor control method and control device capable of continuing or stopping stable limited operation.

In order to achieve the above object, the present invention employs the following technical means. That is, in the first aspect of the present invention, the voltage command applied to the stator coil composed of a plurality of phases is output and the load (11) is driven without using a position sensor for detecting the position of the rotor. A synchronous motor control method for controlling the operation of the synchronous motor (12).
Via an inverter circuit (18) that converts the voltage of the AC power supply (13) that may cause an instantaneous voltage drop to DC, charges the capacitor with the voltage converted to DC, and uses the voltage of the capacitor as an input voltage. The synchronous motor (12) is driven,
By applying a voltage to the stator coil according to the voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling the current vector (i) flowing through the stator coil, the synchronous motor (12) can be rotated at the rotational speed based on the operation command. A normal motor control step (S4) for driving, and applying a voltage to the stator coil by a voltage amplitude and voltage phase command based on the estimated position of the rotor to control the current vector (i) flowing through the stator coil, thereby controlling the synchronous motor A limited operation control step (S5) for limiting (12) to a rotational speed lower than the rotational speed based on the operation command;
The limited operation determination step (S3) for determining whether or not the limited operation is necessary from the voltage and current of the stator coil and at least one state quantity related thereto, and the limited operation determination step (S3) is determined that the limited operation is necessary. Operation control switching steps (S3 to S5) for switching the operation control from the normal operation control step (S4) to the limited operation control step (S5). In the limited operation control step (S5), the current vector (i ) Phase angle (θc) is controlled to a predetermined range of lead angle, and the rotation speed is more linear and gentler than the decrease in rotation speed due to the rotation speed limit line set in accordance with the voltage drop line at the capacitor voltage. It is characterized by lowering .

  According to the first aspect of the present invention, for example, even when the power supply voltage is instantaneously reduced, the phase angle (θc) of the current vector (i) is controlled to a predetermined range of advance angle to limit the rotation. Even if a transient position estimation error occurs, including the range where the motor is raised (actuated by so-called field weakening control), the rotational speed control line that matches the mechanical characteristics of the rotor will be lowered to the rotational speed limit or stopped. Can be made. As a result, an unstable operation such as the rotor rotating in vibration can be prevented, and the synchronous motor (12) can be stably shifted to the limit operation while avoiding the step-out of the synchronous motor (12), or Can be stopped.

  According to a second aspect of the present invention, in the synchronous motor control method according to the first aspect, the limited operation determination step (S3) controls the predetermined threshold, the state quantity, and the current vector (i). And a relational map or current relation value with the current limit value, and when it is determined that the limited operation is necessary by comparing the state quantity and the threshold value, the normal operation control step (S4) to the limited operation control step ( The operation control is switched to S5), and a current limit value is derived from the state quantity and the relational expression or relational map for control.

  According to the second aspect of the present invention, the limit value is determined based on the state quantity as compared with the case where the current limit value is calculated using the actually measured state quantity (eg, voltage, current, rotation speed, etc.). Thus, the processing can be simplified.

  According to a third aspect of the present invention, in the synchronous motor control method according to the first or second aspect, in the limited operation step (S5), the current in the magnetic pole axis direction of the current vector (i) or orthogonal to the magnetic pole axis. The phase angle (θc) of the current vector (i) is controlled to be a lead angle within a predetermined range by limiting the current value of any of the currents in the direction of current. According to the third aspect of the present invention, since it is not necessary to calculate the phase angle (θc) of the current vector (i), the calculation can be simplified.

  According to a fourth aspect of the present invention, in the synchronous motor control method according to any one of the first to third aspects, the phase angle (θc) of the current vector (i) is set to 90 to 150 degrees as a predetermined range. It is characterized by being. According to the fourth aspect of the present invention, even when a position estimation error occurs, the rotation limit of the synchronous motor (12) can be raised as much as possible to maintain the rotation.

  According to a fifth aspect of the present invention, in the synchronous motor control method according to any of the first to fourth aspects, the phase angle (θc) of the current vector (i) is set to approximately 90 degrees as a predetermined range. It is characterized by that. According to the fifth aspect of the present invention, it is possible to minimize the torque fluctuation with respect to the axis error (the estimated position error with respect to the actual position of the rotor).

  According to a sixth aspect of the present invention, in the method for controlling a synchronous motor according to any of the first to fifth aspects, the load (11) is a compression mechanism (for compressing the refrigerant circulating during the heat pump cycle). 11). According to the sixth aspect of the present invention, the compression mechanism (11) for compressing the refrigerant of the heat pump cycle is likely to vary greatly in load torque depending on the state of the refrigerant in the cycle and the suction compression / discharge cycle, and the rotational direction. In this case, vibration fluctuations are likely to occur in the rotor.

  Therefore, according to the present invention, even when the power supply voltage drops instantaneously, an unstable operation such as the rotor rotating in vibration can be prevented, and the synchronous motor (12) is stepped out and stopped. The effect of stably shifting to the limited operation or stopping is avoided.

According to the seventh aspect of the present invention, the voltage command to be applied to the stator coil composed of a plurality of phases is output and the load (11) is driven without using a position sensor for detecting the position of the rotor. A control device for a synchronous motor for controlling the operation of the synchronous motor (12),
An inverter circuit (18) having a capacitor that converts the voltage of the AC power source (13) that may cause an instantaneous voltage drop into DC and that is charged with the voltage converted to DC, and uses the voltage of the capacitor as an input voltage. ) Through which the synchronous motor (12) is driven,
By applying a voltage to the stator coil according to the voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling the current vector (i) flowing through the stator coil, the synchronous motor (12) can be rotated at the rotational speed based on the operation command. By operating the normal operation control means (22) to be operated and applying a voltage to the stator coil in accordance with a voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling the current vector (i) flowing through the stator coil, the synchronous motor (12) limited operation control means (23) for limiting the operation to a rotation speed lower than the rotation speed based on the operation command;
The limited operation determination means (24) for determining whether or not the limited operation is necessary from the voltage and current of the stator coil and at least one state quantity related thereto, and the limited operation determination means (24) determines that the limited operation is necessary. Operation control switching means (25) for switching the operation control from the normal operation control means (22) to the limited operation control means (23). The limited operation control means (23) The phase angle (θc) is controlled to a lead angle within a predetermined range, and the rotational speed is further reduced more linearly and gently than the rotational speed is reduced by the rotational speed limit line set in accordance with the voltage drop line at the capacitor voltage. It is characterized by letting . According to the seventh aspect of the invention, the control method of the first aspect of the invention can be performed.

  According to an eighth aspect of the present invention, in the synchronous motor control device according to the seventh aspect, the limited operation determining means (24) controls the predetermined threshold, the state quantity, and the current vector (i). The relational expression or relation map with the current limit value is previously stored, and when it is determined that the limited operation is necessary by comparing the state quantity and the threshold value, the normal operation control means (22) to the limited operation control means ( The operation control is switched to 23), and the current limit value is derived from the state quantity and the relational expression or the relation map for control. According to the eighth aspect of the invention, the control method of the second aspect of the invention can be performed.

  According to the ninth aspect of the present invention, in the synchronous motor control device according to the seventh or eighth aspect, the limited operation control means (23) applies the current in the magnetic pole axis direction of the current vector (i) or the magnetic pole axis. The phase angle (θc) of the current vector (i) is controlled to the advance angle within a predetermined range by limiting the current value of any of the currents in the orthogonal direction. According to the ninth aspect of the invention, the control method of the third aspect of the invention can be performed.

  According to a tenth aspect of the present invention, in the synchronous motor control device according to any of the seventh to ninth aspects, the phase angle (θc) of the current vector (i) is set to 90 to 150 degrees as a predetermined range. It is characterized by being. According to the invention described in claim 10, the control method of the invention described in claim 4 can be performed.

  In the invention according to claim 11, in the synchronous motor control device according to any one of claims 7 to 10, the phase angle (θc) of the current vector (i) is set to approximately 90 degrees as a predetermined range. It is characterized by that. According to the eleventh aspect, the control method according to the fifth aspect can be performed.

  According to a twelfth aspect of the present invention, in the synchronous motor control device according to any of the seventh to eleventh aspects, the load (11) is a compression mechanism (for compressing the refrigerant circulating during the heat pump cycle). 11). According to the invention of the twelfth aspect, the control method of the invention of the sixth aspect can be performed. In addition, the code | symbol in the parenthesis as described in a claim and said each means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, the first embodiment will be described in detail with reference to FIGS. First, FIG. 1 is a block diagram showing a schematic configuration of a drive circuit of the electric compressor 10 and a control device 20 in the first embodiment. The electric compressor 10 is a compressor disposed in a heat pump cycle such as a heat pump type hot water supply apparatus using carbon dioxide or the like as a refrigerant, for example, and as shown in FIG. 1, a compression mechanism (load referred to in the present invention). 11 is an electric compressor that is driven by a synchronous motor 12 having a built-in motor 11 and compresses a gas-phase refrigerant (for example, compresses it to a critical pressure or more if it is a carbon dioxide refrigerant) and discharges it.

  The synchronous motor 12 of this embodiment is a synchronous motor having a four-pole three-phase coil that rotationally drives a rotor in which magnets are embedded. Then, the AC voltage from the AC power supply unit 13 is input to the AC / DC converter circuit 15 through the input line 14, converted into a DC voltage, and input to the inverter circuit 18 through the bus 16. Note that a capacitor 17 is connected to the bus 16 between the AC / DC converter circuit 15 and the inverter circuit 18, and the AC voltage from the AC power supply unit 13 sharply decreases (instantaneous voltage decrease) due to a lightning strike or the like. If so, the capacitor voltage is generated. Alternatively, a smoothing capacitor may be provided in the AC / DC converter circuit 15.

  The inverter circuit 18 applies voltage to each phase (U, V, W phase) of the stator coil of the synchronous motor 12 via the wiring 19 based on a command signal from the control device 20 so that the rotor is driven to rotate. It has become. As shown in FIG. 1, the inverter circuit 18 has a known structure composed of a plurality of arms in which switching elements and diodes are connected in antiparallel.

  The control device 20 includes a control input / output unit 21, a normal operation control unit 22, a limited operation control unit 23, a limited operation determination unit 24, and an operation control switching unit 25. Here, the normal operation control unit 22 corresponds to the normal operation control unit in the present embodiment, the limited operation control unit 23 corresponds to the limited operation control unit, and the limited operation determination unit 24 corresponds to the limited operation determination unit. The control switching unit 25 corresponds to an operation control switching unit.

  The control input / output unit 21 is a connection unit that manages input / output of signals between the inverter power supply component (in this example, the inverter circuit 18 and the wiring 19) and the substantial motor control unit of the control device 20. As shown in FIG. 1, the input / output of information signals performed via the control input / output unit 21 includes input of detected current value information in one phase or a plurality of phases (two phases in this example) of the wiring 19, and an inverter circuit. There are input of voltage information from 18 and output of voltage command information to the inverter circuit 18.

  The normal operation control unit 22 estimates the rotor position by using the actual state quantity (measured state quantity, for example, voltage, current, rotation speed) of the synchronous motor 12 input via the control input / output unit 21 and calculates The voltage amplitude and voltage phase commands based on the estimated position of the rotor are output to the inverter circuit 18 via the control input / output unit 21, and a voltage is applied to the stator coil by vector control reflecting the estimated position of the rotor to synchronize. A function of operating the motor 12 at a rotational speed based on the operation command is provided. The control executed here is so-called position sensorless control.

  On the other hand, the limited operation control unit 23 estimates the position of the rotor using the actual state quantities (measured state quantities such as voltage, current, and rotation speed) of the synchronous motor 12 input via the control input / output unit 21. A voltage amplitude and voltage phase command based on the calculated estimated position of the rotor is output to the inverter circuit 18 via the control input / output unit 21, and a voltage is applied to the stator coil by vector control reflecting the estimated position of the rotor. Thus, the synchronous motor 12 is provided with a function of limiting the rotational speed to a rotational speed lower than the rotational speed based on the operation command.

  The normal operation control unit 22 and the limited operation control unit 23 include current control units 221 and 231 and speed control units 222 and 232, respectively. The limited operation determination unit 24 detects (acquires) the actual state quantities (voltage values and current values actually measured in this example) of the synchronous motor 12 input via the control input / output unit 21 and the detection results thereof. It is determined whether or not limited operation is necessary based on (acquired result).

  When it is determined that the limited operation is necessary, an operation control switching command from the normal operation control to the limited operation control is output to the operation control switching unit 25. The operation control switching unit 25 performs operation control switching between normal operation control by the normal operation control unit 22 and limited operation control by the limited operation control unit 23.

  Next, the control operation will be described with reference to a flowchart. FIG. 2 is a flowchart showing a schematic control operation of the limited operation determination unit 24 and the operation control switching unit 25 in FIG. The limited operation determination unit 24 of the control device 20 acquires the actual state quantity (measured voltage value or current value in this example) of the synchronous motor 12 via the control input / output unit 21 (step S1). Next, the limited operation determination unit 24 calculates the maximum rotation speed (limit value) based on the actual state quantity detected in step S1 (step S2).

  Then, from the relationship shown in FIG. 3, it is determined whether or not the calculated maximum rotational speed exceeds a predetermined threshold rotational speed, and it is determined whether or not limited operation is necessary (step S3). FIG. 3 is a graph showing an example in which the operation control switching determination is performed based on the relationship between the maximum rotational speed and the input voltage from the power source examined in advance.

  If the calculated maximum rotational speed exceeds the predetermined threshold rotational speed and there is no need for the limited operation, normal operation control (step S4) is performed, and the calculated maximum rotational speed is below the predetermined threshold rotational speed and the limited operation is performed. If it is necessary, the limited operation control (step S5) is performed. That is, the limited operation determination unit 24 calculates the maximum number of revolutions from the state quantity and determines whether or not the limited operation is necessary.

  Here, step S3 is a limited operation determination step in the present embodiment, steps S3 to S5 are operation control switching steps in the present embodiment, step S4 is a normal operation control step in the present embodiment, and step S5 is a limited operation in the present embodiment. It is a control step. In addition, said step S1-5 is always repeatedly performed while the synchronous motor 12 is drive | operated.

  Next, an operation when the operation control is switched will be described. FIG. 4 is a graph showing the transition of the input voltage and the rotational speed of the synchronous motor 12 when, for example, an instantaneous voltage drop occurs and the operation control is switched. In the example shown in FIG. 4, a case where the input voltage from the AC power supply unit 13, which is usually 250 V, is reduced to 100 V at a stroke due to lightning strikes or the like is shown.

  First, when the input voltage is normal 250 V, the maximum rotation number as the limit value calculated in step S2 described above is 8000 rpm in this example. For this reason, in the above-described determination in step S3 performed by the limited operation determination unit 24, the normal operation control by the normal operation control unit 22 is performed because it exceeds the predetermined threshold rotation speed and there is no need for the limited operation.

  However, when the input voltage drops to 100 V due to the instantaneous voltage drop, the maximum rotational speed as the limit value calculated in step S2 described above is 2000 rpm in this example. For this reason, in the above-described determination in step S3 performed by the limited operation determination unit 24, the operation is switched to the limited operation control by the limited operation control unit 23 because it is below the predetermined threshold rotation speed and the limited operation is necessary.

  Then, the maximum rotational speed of the synchronous motor 12 is limited to 2000 rpm (the rotational speed limit line indicated by the solid line in FIG. 4). In this embodiment, since the capacitor 17 is provided on the input side of the inverter circuit 18, the actual input voltage is set to a certain time constant as indicated by the broken line in FIG. 4 due to the capacitor voltage generated by the capacitor 17. Decreases in relation to Since the voltage actually inputted to the inverter circuit 18 becomes this capacitor voltage, the rotation speed limit line indicated by the broken line in FIG. 4 is driven in accordance with the voltage drop line at the capacitor voltage.

  However, the reduction in the rotational speed due to the mechanical characteristics including the actual load of the rotor is, for example, as shown by a one-dot chain line in FIG. As described above, since the change due to the mechanical characteristics is slow with respect to the electric command, even if any of the above-mentioned limit lines is taken, the actual rotor movement cannot follow and stops due to instability or step-out. There is a case.

  Therefore, in this embodiment, the target is to set the rotational speed limit line in accordance with the mechanical characteristics including the actual load of the rotor. However, as can be seen from FIG. 4, there is a region where the voltage is insufficient. For this reason, the current value jumps by the amount of voltage shortage and sticks to the current value limit line, or may be unstable due to a sudden change. Therefore, in this embodiment, the phase angle of the current vector is controlled to a predetermined range of advance angle so that the drive is continued while maintaining the rotation limit as much as possible even when an error occurs in position estimation.

  First, FIG. 5 and FIG. 6 are diagrams for defining coordinate axes in motor control. FIG. 5 shows the relationship between the position of each phase (U, V, W phase) of the stator coil and the fixed coordinates composed of the α and β axes, and FIG. 6 shows the rotor based on the α and β axes. It shows a rotational coordinate composed of a d-axis that is a magnetic pole axis and a q-axis that is orthogonal to the d-axis.

The limited operation control unit 23 calculates an instantaneous current vector phase based on the U-phase current value iu and the V-phase current value iv that are detection values acquired from the control input / output unit 21. Specifically, the obtained U-phase current value iu and V-phase current value iv are coordinate-transformed, and the d-axis current id that is the d-axis component of the current vector i that flows through the stator coil and the q-axis current iq that is the q-axis component. Is calculated. Next, the current phase (phase angle of the current vector i) θc is calculated from the relationship shown in FIG.
(Equation 1)
θc = tan-1 (iq / id)
In the present embodiment, during the limited operation control, the phase angle θc of the current vector i is controlled to an advance angle within a predetermined range. Specifically, the predetermined range of the phase angle θc is 90 to 150 degrees. Note that the phase angle θc of the current vector i to be limited varies depending on the characteristics of the synchronous motor 12 and the compression mechanism 11 that is a load, and thus cannot be uniquely determined. In consideration of maintaining the rotational speed as much as possible, the range of the phase angle θc that can actually be stably driven is set by conducting an actual machine investigation in advance.

  As a method for limiting the phase angle θc of the current vector i, the d-axis and q-axis current values may be individually limited so that the same effect can be obtained using the d-axis and q-axis current values. That is, if the control is vector control, the current values of the d-axis and the q-axis are used in the control, so that it is not necessary to newly calculate them, so that the control can be simplified.

Next, the features and effects of this embodiment will be described. First, a voltage is applied to the stator coil by a voltage amplitude and voltage phase command based on the estimated position of the rotor, and the current vector i flowing through the stator coil is controlled, so that the synchronous motor 12 is operated at the rotation speed based on the operation command. A voltage is applied to the stator coil by the normal operation control unit 22 and a voltage amplitude and voltage phase command based on the estimated position of the rotor, and the current vector i flowing through the stator coil is controlled, thereby causing the synchronous motor 12 to be based on the operation command. A limited operation control unit 23 that operates by limiting to a lower rotation speed than the rotation speed;
When it is determined by the limited operation determination unit 24 that determines whether or not the limited operation is necessary from the voltage and current of the stator coil and at least one state quantity related thereto, and the limited operation determination unit 24 determines that the limited operation is necessary In addition, an operation control switching unit 25 that switches operation control from the normal operation control unit 22 to the limited operation control unit 23 is provided, and the limited operation control unit 23 controls the phase angle θc of the current vector i to an advance angle within a predetermined range. I am doing so.

  According to this, for example, even when the power supply voltage decreases instantaneously, the phase angle θc of the current vector i is controlled to a predetermined range of advance angle to increase the rotation limit (actuated by so-called field weakening control). Even if a transient position estimation error including the range occurs, the rotational speed can be reduced to the limit rotational speed or stopped by the rotational speed control line that matches the mechanical characteristics of the rotor. As a result, an unstable operation such as the rotor rotating in vibration can be prevented, and the synchronous motor 12 can be stably shifted to the limited operation or stopped while preventing the synchronous motor 12 from stepping out and stopping. be able to.

  Further, the limited operation control unit 23 limits the current value of the current vector i in the direction of the magnetic pole axis or the current in the direction perpendicular to the magnetic pole axis to thereby set the phase angle θc of the current vector i within a predetermined range. The advance angle is controlled. According to this, since it is not necessary to calculate the phase angle θc of the current vector i, the calculation can be simplified.

  Further, the phase angle θc of the current vector i is set to 90 to 150 degrees as a predetermined range. According to this, even when a position estimation error occurs, the rotation limit of the synchronous motor 12 can be raised as much as possible to maintain the rotation. The load is a compression mechanism 11 for compressing the refrigerant circulating during the heat pump cycle. According to this, in the compression mechanism 11 that compresses the refrigerant in the heat pump cycle, the load torque is likely to fluctuate greatly depending on the state of the refrigerant in the cycle and the suction compression / discharge cycle, and vibrational fluctuations occur in the rotor in the rotational direction. Easy to do.

  Therefore, according to the present invention, even when the power supply voltage is instantaneously reduced, it is possible to prevent an unstable operation such as the rotor rotating oscillating, and the synchronous motor 12 is prevented from stepping out and stopping. While avoiding, the effect of stably shifting to the limited operation or stopping is extremely large.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. FIG. 8 shows a state where the phase angle θc of the current vector i is 170 degrees in the dq axis coordinates, and FIG. 9 shows a state where the phase angle θc of the current vector i is 90 degrees in the dq axis coordinates. FIG. 10 is a characteristic diagram showing the relationship between the error (axis error) between the actual position of the rotor and the estimated position and the torque. In the following embodiments, the same components as those in the first embodiment described above are denoted by the same reference numerals, description thereof will be omitted, and different configurations and features will be described.

  FIG. 8 and FIG. 9 show characteristics that cause a problem that the operation becomes unstable in the position sensorless control. In the position sensorless control, in the state of a transient change such as a sudden change of the input voltage, the actual position of the rotor and the estimated position are deviated to generate an axis error. FIG. 10 shows the effect on torque when an axial error occurs at the angle of the current vector i as shown in FIGS.

  As can be seen from FIG. 10, when the phase angle θc of the current vector i is 90 degrees, the torque change with respect to the axis error is small, but when the phase angle θc of the current vector i is 170 degrees, the torque with respect to the axis error. A big change will occur. For example, when the phase angle θc = 170 degrees of the current vector i and the axial error is 0 degree and when the axial error is 30 degrees, + 1Nm is −1Nm and the error is such that the torque is reversed. turn into.

  For this reason, it is necessary to control the angle of the current vector i to be within a predetermined range. In the present embodiment, the phase angle θc of the current vector i is approximately 90 degrees as a predetermined range. According to this, the torque fluctuation with respect to the shaft error can be minimized. In other words, even if an axial error occurs, a torque error does not occur greatly, and even in an operating state where the input voltage changes suddenly, it is possible to realize a drive that is as stable as possible.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. FIG. 11 is a map showing the relationship between the maximum number of rotations, the magnitude of the current vector, and the current limit value. A different characteristic part from each embodiment mentioned above is demonstrated. The limited operation determination unit 24 of the present embodiment has in advance a predetermined threshold and a relational expression or a relation map between the current limit value for controlling the state quantity and the current vector i. When it is determined that the limited operation is necessary, the operation control is switched from the normal operation control unit 22 to the limited operation control unit 23, and the current limit value is derived from the state quantity and the relational expression or the relation map for control. I have to.

  According to this, processing is simplified by determining the limit value based on the state quantity, compared to calculating the current limit value using the actually measured state quantity (for example, voltage, current, rotation speed, etc.). be able to.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows. For example, in the above-described embodiment, it is determined whether normal operation control or limited operation control is based on whether or not the calculated maximum rotational speed (limit value) exceeds a predetermined threshold rotational speed. It may be determined whether the normal operation control or the limited operation control is performed based on the operation state obtained from the state quantity from.

  In other words, the determination of the operating state is performed using at least one or more information related to the voltage and current and the state variables, and the rotational speed limit value and the related value are calculated, and the rotational speed limit value and the related value are calculated. The value may be calculated from a voltage equation of the synchronous motor or a simplified formula.

  In the above-described embodiment, as shown in FIG. 7, the case where the rotation direction of the rotor is the counterclockwise direction has been described. However, as shown in FIG. 12, the rotation direction of the rotor is the clockwise direction. Of course it may be. In the above-described embodiment, the synchronous motor 12 is a four-pole three-phase motor, but the number of poles and the number of phases are not limited thereto.

  In the above-described embodiment, the description of the type of the compression mechanism 11 driven by the synchronous motor 12 is omitted, but various types of compression mechanisms such as a rotary type, a piston type, and a scroll type can be employed. When the rotary type compression mechanism is employed, the rotary type compression mechanism is particularly effective when the operation control switching according to the present invention is applied because the torque fluctuation during driving is relatively large.

  Moreover, in the above-mentioned embodiment, although the synchronous motor 12 was a motor which drives the compression mechanism 11 of the heat pump cycle which uses a carbon dioxide as a refrigerant | coolant, it is not limited to this. The refrigerant may be a compressor motor of a heat pump cycle (refrigeration cycle) other than carbon dioxide, and the load may be a pump mechanism instead of a compression mechanism. The present invention is widely applied and effective when controlling the operation of a synchronous motor without using a position sensor.

1 is a block diagram showing a schematic configuration of a drive circuit of an electric compressor 10 and a control device 20 in a first embodiment of the present invention. 2 is a flowchart showing a schematic control operation of a voltage drop determination unit 24 and an operation control switching unit 25 in FIG. It is a graph which shows the example which performs driving | operation control switching determination from the relationship of the maximum rotation speed with respect to the input voltage from the power supply investigated beforehand. It is a graph which shows transition of an input voltage and the rotation speed of the synchronous motor 12 when an instantaneous voltage drop arises and operation control switches. It is a figure which defines the relationship between the position of each phase (U, V, W phase) of a stator coil, and the fixed coordinate which consists of (alpha) and (beta) axis | shaft. It is a figure which defines the rotation coordinate which consists of d axis | shaft which is a rotor magnetic pole axis, and q axis orthogonal to d axis | shaft on the basis of (alpha) and (beta) axis. It is a figure which shows the relationship between phase angle (theta) c of the current vector i, d-axis current id, and q-axis current iq. It is a figure which shows the state whose phase angle (theta) c of the current vector i is 170 degree | times in a dq-axis coordinate. It is a figure which shows the state whose phase angle (theta) c of the current vector i is 90 degree | times in a dq-axis coordinate. FIG. 6 is a characteristic diagram showing a relationship between an error (axis error) between an actual position of a rotor and an estimated position and torque. It is a map which shows the relationship between the maximum rotation speed, the magnitude | size of a current vector, and a current limiting value. It is a figure explaining the state of the electric current vector i at the time of performing the operation control switching in other embodiment.

Explanation of symbols

11 ... Compression mechanism (load)
12 ... Synchronous motor 22 ... Normal operation control part (normal operation control means)
23. Restricted operation control unit (restricted operation control means)
24. Restricted operation determination unit (restricted operation determination means)
25. Operation control switching unit (operation control switching means)
i: Current vector θc: Phase angle

Claims (12)

Synchronous operation for controlling the operation of a synchronous motor (12) for driving a load (11) by outputting a voltage command to be applied to a stator coil composed of a plurality of phases without using a position sensor for detecting the position of the rotor. A method for controlling a motor,
Via an inverter circuit (18) that converts the voltage of the AC power supply (13) that may cause an instantaneous voltage drop to DC, charges the capacitor with the voltage converted to DC, and uses the voltage of the capacitor as an input voltage. The synchronous motor (12) is driven,
By applying a voltage to the stator coil by a voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling a current vector (i) flowing through the stator coil, the synchronous motor (12) is set as an operation command. A normal operation control step (S4) for operating at a rotational speed based on
By applying a voltage to the stator coil by a voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling a current vector (i) flowing through the stator coil, the synchronous motor (12) is controlled by the operation command. A limited operation control step (S5) for limiting the operation to a rotation speed lower than the rotation speed based on
A limited operation determination step (S3) for determining whether or not the limited operation is necessary from the voltage and current of the stator coil and at least one state quantity related thereto;
Operation control switching step (S3 to S5) for switching the operation control from the normal operation control step (S4) to the limited operation control step (S5) when it is determined that the limited operation is necessary in the limited operation determination step (S3). And
In the limit operation control step (S5), the phase angle (θc) of the current vector (i) is controlled to an advance angle within a predetermined range, and the rotation speed limit set in accordance with the voltage drop line at the capacitor voltage A method for controlling a synchronous motor, characterized in that the rotational speed is further reduced linearly and gradually rather than a reduction in rotational speed due to a line . The limited operation determination step (S3) has in advance a relational expression or a relationship map of a predetermined threshold value and the current limit value for controlling the state quantity and the current vector (i),
When it is determined that the limited operation is necessary by comparing the state quantity and the threshold, the operation control is switched from the normal operation control step (S4) to the limited operation control step (S5).
2. The synchronous motor control method according to claim 1, wherein the current limit value is derived from the state quantity and the relational expression or the relation map and controlled.   In the limiting operation control step (S5), the current vector (i) is limited by limiting the current value of either the current in the magnetic pole axis direction of the current vector (i) or the current in the direction orthogonal to the magnetic pole axis. The method of controlling a synchronous motor according to claim 1, wherein the phase angle (θc) is controlled to a lead angle within a predetermined range.   The method for controlling a synchronous motor according to any one of claims 1 to 3, wherein the phase angle (θc) of the current vector (i) is 90 to 150 degrees as the predetermined range.   5. The method for controlling a synchronous motor according to claim 1, wherein the phase angle (θc) of the current vector (i) is approximately 90 degrees as the predetermined range.   6. The method for controlling a synchronous motor according to claim 1, wherein the load (11) is a compression mechanism (11) for compressing a refrigerant circulating during a heat pump cycle. Synchronous operation for controlling the operation of a synchronous motor (12) for driving a load (11) by outputting a voltage command to be applied to a stator coil composed of a plurality of phases without using a position sensor for detecting the position of the rotor. A motor control device,
An inverter circuit (18) having a capacitor that converts the voltage of the AC power source (13) that may cause an instantaneous voltage drop into DC and that is charged with the voltage converted to DC, and uses the voltage of the capacitor as an input voltage. ) To drive the synchronous motor (12),
By applying a voltage to the stator coil by a voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling a current vector (i) flowing through the stator coil, the synchronous motor (12) is set as an operation command. Normal operation control means (22) for operation at a rotational speed based on
By applying a voltage to the stator coil by a voltage amplitude and voltage phase command based on the estimated position of the rotor and controlling a current vector (i) flowing through the stator coil, the synchronous motor (12) is controlled by the operation command. Limited operation control means (23) for operating by limiting to a lower rotation speed than the rotation speed based on
Limited operation determining means (24) for determining whether or not the limited operation is necessary from the voltage and current of the stator coil and at least one state quantity related thereto;
An operation control switching means (25) for switching the operation control from the normal operation control means (22) to the restricted operation control means (23) when the restricted operation determination means (24) determines that the restricted operation is necessary. Prepared,
The limit operation control means (23) controls the phase angle (θc) of the current vector (i) to an advance angle within a predetermined range, and limits the rotation speed set in accordance with the voltage drop line at the capacitor voltage. A control apparatus for a synchronous motor, characterized in that the rotational speed is further reduced linearly and gradually rather than a reduction in rotational speed due to a line . The limited operation determination means (24) has in advance a relational expression or a relationship map between a predetermined threshold value and a current limit value for controlling the state quantity and the current vector (i),
When it is determined that the limited operation is necessary by comparing the state quantity and the threshold, the operation control is switched from the normal operation control means (22) to the limited operation control means (23), and
The synchronous motor control device according to claim 7, wherein the current limit value is derived from the state quantity and the relational expression or the relation map and controlled.   The limited operation control means (23) limits the current value of either the current in the magnetic pole axis direction of the current vector (i) or the current in the direction orthogonal to the magnetic pole axis, thereby the current vector (i). The synchronous motor control device according to claim 7 or 8, wherein the phase angle (θc) is controlled to a lead angle within a predetermined range.   The synchronous motor control device according to any one of claims 7 to 9, wherein the phase angle (θc) of the current vector (i) is 90 to 150 degrees as the predetermined range.   11. The synchronous motor control device according to claim 7, wherein the phase angle (θc) of the current vector (i) is approximately 90 degrees as the predetermined range.   The synchronous motor control device according to any one of claims 7 to 11, wherein the load (11) is a compression mechanism (11) for compressing a refrigerant circulating during a heat pump cycle.

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