JP5517851B2 - Refrigeration equipment having a motor control device and a compressor drive device using the motor control device - Google Patents

Description

The present invention, a motor control device, a refrigeration apparatus including a compressor driving apparatus using the motor controller.

  The following methods are known as conventional motor control devices.

  As a positioning mode, the rotor is positioned by passing a current through a specific phase. Next, as a synchronous operation mode, the synchronous motor is driven without using information on the rotational angle position of the permanent magnet motor, and the output frequency of the inverter is gradually increased to accelerate from the positioning state to a certain rotational speed. Next, the operation mode is shifted to the position feedback operation mode at the number of rotations, and the operation is performed using the estimated value of the magnetic pole position or the information on the rotation angle position by the magnetic pole position sensor or the like.

  Further, as a technique for realizing uniform acceleration characteristics regardless of load torque, the following method described in Japanese Patent Application Laid-Open No. 2007-37352 (Patent Document 1) is known.

  During the synchronous operation mode, an estimation calculation of a value proportional to the torque of the permanent magnet motor is performed, a control constant is set based on the value proportional to the torque, and the mode shifts to the position feedback operation mode. Next, during the synchronous operation mode, the ratio of the first current in the current phase energized during positioning and the second current in the phase advanced by 90 degrees in the rotation direction is sequentially changed to shift to the position feedback operation mode. Sometimes, a fixed initial value is set for the first current and the second current command value.

JP 2007-33752 A

  The control method described in Patent Document 1 changes the current command value during the synchronous operation mode and suppresses the speed fluctuation when switching to the position feedback operation mode, and the load torque changes greatly during the position feedback operation. There is no description on how to deal with the speed fluctuations that occur.

  In the conventional motor control system, due to the configuration of the control loop, the response frequency of the automatic speed regulator (hereinafter referred to as “ASR”) is the automatic current regulator (hereinafter referred to as “ACR”). It is necessary to set it sufficiently lower than.

  Therefore, in the conventional motor control system, when the output torque (hereinafter referred to as required torque) required to rotate the motor obtained from the sum of the load torque and the acceleration torque greatly changes during the position feedback operation mode, The response cannot follow the change and the control becomes unstable.

  Accordingly, the present invention provides a control configuration that suppresses speed fluctuations that occur when the required torque changes suddenly and greatly during the position feedback operation mode, and that has uniform stability against changes in the required torque. Objective.

In order to solve the problem, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above-described problem. To give an example, a calculation means for calculating a current command value that is an electric quantity related to the torque of the permanent magnet motor or a value related to the current command value ; a current controller which receives the value of the said current command value or current command value, a voltage command value generator which receives the output of the current controller, the permanent magnet motor according to an output of said voltage command value generator In a motor control device having a power conversion circuit for applying a voltage to the motor, the torque is suddenly reduced by using a timing when the torque of the permanent magnet motor suddenly changes or fluctuates during the position feedback operation mode as a trigger. The q-axis current command value or the integral term of the speed controller is set to the q-axis current value necessary to output the necessary torque after the change according to the timing trigger. Alternatively, the lower limit function for limiting the lower limit value of the q-axis current command value to the lower limit value is turned OFF or the timing at which the torque fluctuation becomes stable is synchronized with the trigger of the timing at which the torque fluctuation becomes stable. According to the trigger, the addition function for adding the difference between the q-axis detection current and the qc-axis current addition determination value to the q-axis current command value is turned off .

  According to the present invention, it is possible to provide a control configuration that suppresses speed fluctuations that occur when the required torque changes suddenly and greatly during the position feedback operation mode, and that has uniform stability against changes in the required torque. Can do.

It is a control block diagram of the motor control apparatus concerning one Example of this invention. It is a figure which shows the example of 1 structure of a power converter circuit. It is a figure which shows an example of a d-axis and q-axis current controller. It is a figure which shows an example of a speed controller. It is a simplified diagram for explaining transition to each operation mode and features. It is a figure which shows an example of the test result when required torque becomes small rapidly during position feedback driving | operation. It is a figure which shows an example of the speed controller in this invention. It is a figure which shows an example of the test result which shows the effect by this invention. It is a control block diagram of the motor control apparatus concerning one Example of this invention. It is a figure which shows an example of the speed controller in this invention. It is a figure which shows an example for demonstrating the fluctuation phenomenon of the load torque in a reciprocating compressor. It is a figure which shows an example of the subject which this invention tends to solve. It is a figure which shows an example of the test result which shows the effect by this invention. It is a control block diagram of the motor control apparatus concerning one Example of this invention. It is a figure which shows an example of the speed controller in this invention. It is a figure which shows an example of the test result which shows the effect by this invention. It is a control block diagram of the motor control apparatus concerning one Example of this invention. It is a figure which shows an example of the speed controller in this invention. It is a figure which shows an example of the test result which shows the effect by this invention. It is a figure which shows an example of the test result which shows the effect by this invention. It is a figure which shows an example of the schematic diagram of a refrigerator at the time of applying this invention to the control apparatus of the compressor drive motor of a refrigerator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In this embodiment, the position information in the position feedback operation mode is the position sensorless control obtained from the motor voltage command and the motor current information, and the position of the permanent magnet motor rotor in the magnetic flux direction is set to the d axis and then to the rotation direction. With respect to the dq-axis real rotation coordinate system (motor axis) consisting of the q-axis advanced by 90 degrees, from the control virtual rotor position dc-axis and from the control position qc-axis advanced by 90 degrees in the rotation direction. The control based on the dc-qc control rotating coordinate system is based on the following control. Hereinafter, the dc-qc coordinate axis is simply referred to as a control axis.

  In addition, a non-salient pole type permanent magnet motor having a small difference in dq axis inductance will be described as an example of the motor, and it will be described that no reluctance torque is generated. It is not limited to.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a control configuration diagram of a motor control device according to the present invention. The motor control device 1 is roughly divided into a current detection unit 2, a control unit 4, and a power conversion circuit 5.

  The current detection means 2 includes motor current detection means 6a and 6b for detecting currents Iu and Iw flowing in the U phase and the W phase among the three-phase AC current flowing in the motor.

  As an example of the motor current detection means 6a, 6b, there is a method of converting a current into a voltage using a shunt resistor. In this case, either of two shunt current detection using two shunt resistors or one shunt current detection using one shunt resistor added to the DC side of the inverter 20 may be used.

  The control unit 4 mainly includes an axis error calculator 8, a PLL controller 10, a speed controller 12a, current controllers 15a and 15b, a voltage command value generator 16, a dq / 3-phase converter 17, and a three-phase / dq. It is composed of a converter 7.

  The three-phase / dq converter 7 receives the motor current detection means 6a, 6b and the estimated magnetic pole position θdc as an input, and performs coordinate conversion from the three-phase axis to the control axis to convert the d-axis detection current Idc and the q-axis. The detection current Iqc is output.

The axis error calculator 8 calculates the d-axis detection current Idc and the q-axis detection current Iqc, the d-axis and q-axis voltage command values (Vd ^* and Vq ^* ), the inverter frequency command value ω1 ^* or the frequency command value ω ^* . As an input, a position error (axis error Δθc) between the actual rotation position (actual rotation coordinate axis) of the rotor of the permanent magnet motor 6 and the virtual rotation position (control axis) is output.

The PLL controller 10 obtains the difference between the shaft error Δθc and the shaft error command value Δθ ^* (usually zero) by the subtractor 9a, and outputs the inverter frequency command value ω1 ^* so that it becomes zero.

As shown in FIG. 4, the speed controller 12a receives the frequency command value ω ^* and the inverter frequency command value ω1 ^* as input, obtains the difference between them by the subtractor 9e, and uses the PI controller so that the difference becomes zero. , Q-axis current command value Iq ^* is output. The q-axis current command value Iq ^* is obtained by the following equation.

[Equation 1]
Iq ^* = (ω ^* −ω1 ^* ) × (Kps + Kis / S) (Equation 1)
Here, Kps is a proportional gain, and Kis is an integral gain.

It should be noted that Iq ^* is output according to (Equation 1) when the control switch 11b is on the B side, and when the control switch 11b is on the A side, the value of Iq ^* is obtained from others such as the host controller. The q-axis current command value Iq ^* 0 is given.

As shown in FIG. 3, the current controllers 15a and 15b receive the d-axis and q-axis current command values (Id ^* and Iq ^* ), the d-axis detection current Idc, and the q-axis detection current Iqc as inputs. Is calculated by the subtractors 9c and 9d, and the second current command values Id ^** and Iq ^** are output so that the difference becomes zero. The second current command values Id ^** and Iq ^** are obtained by the following equations.

[Equation 2]
Id ^** = (Id ^* −Idc) × (Kpd + Kid / S) (Formula 2)
Iq ^** = (Iq ^* −Iqc) × (Kpq + Kiq / S) (Formula 3)
Here, Kpd and Kpq are proportional gains, and Kid and Kiq are integral gains.

The voltage command value generator 16 receives the second current command value (Id ^** and Iq ^** ) and the inverter frequency command value ω1 ^* as input, performs a vector operation, and performs a d-axis voltage command value Vd ^* and a q-axis voltage command. The value Vq ^* is output. The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are obtained by the following equations.

[Equation 3]
Vd ^* = R × Id ^{** −} ω1 ^* × Lq × Iq ^** (Formula 4)
Vq ^* = R × Iq ^** + ω1 ^* × Ld × Id ^** + ω1 ^* × Ke (Formula 5)
Here, in (Expression 4) and (Expression 5), R is the primary winding resistance value of the permanent magnet motor 3, Ld is the d-axis inductance, Lq is the q-axis inductance, and Ke is the induced voltage constant.

The dq / 3-phase converter 17 receives the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* as input, converts the coordinate from the control axis to the three-phase axis, and applies it to the permanent magnet motor 3. The values (Vu ^* , Vv ^* , Vw ^* ) are output.

  As shown in FIG. 2, the power conversion circuit 5 includes an inverter 20, a DC voltage source 21, and a driver circuit 22. The inverter 20 is composed of a switching element such as an IGBT or a power MOSFET. The inverter 20 performs a switching operation in accordance with the pulse signals 23a, 23b, and 23c output from the driver circuit 22, and drives the motor by applying an AC voltage having an arbitrary frequency to the permanent magnet motor.

The basic operation when starting the permanent magnet motor 3 will be described. FIG. 5 is a simplified diagram showing transition of each operation mode when starting the permanent magnet motor 3. The operation mode includes a positioning mode in which a DC current is gradually passed through a motor winding of an arbitrary phase to fix the rotor of the permanent magnet motor 3 at a certain position, a d-axis current command value Id ^*, and a q-axis current command value. A synchronous operation mode that determines the voltage to be applied to the permanent magnet motor 3 according to Iq ^* and the frequency command ω ^*, and a position feedback operation mode that adjusts the inverter frequency command value ω1 ^* so that the axis error Δθc becomes zero. There is one.

In these operation modes, any one of the d-axis current command value Id ^* , the q-axis current command value Iq ^* , and the inverter frequency command value ω1 ^* is changed, or the control changeover switches 11a and 11b in the control unit 4a are switched. Makes a transition to another operation mode. Note that the two control change-over switches 11a and 11b are simultaneously switched unless otherwise specified.

In the synchronous operation mode, the frequency command ω ^* is gradually increased, and the speed of the permanent magnet motor 3 is increased accordingly. When the frequency at which the position feedback operation can be performed is reached, the control changeover switches 11a and 11b are set to the B side to shift to the position feedback operation mode. As a result, the PLL controller 10 adjusts the inverter frequency command value ω1 ^* so that the difference between the shaft error Δθc and the shaft error command value Δθ ^* (usually zero) is zero, and the frequency command value ω ^* and the inverter The speed controller 12 adjusts the q-axis current command value Iq ^* so that the difference from the frequency command value ω1 ^* becomes zero. Iq ^* becomes a value corresponding to the required torque which is the sum of the acceleration torque and the load torque, and the permanent magnet motor 3 is accelerated. Thereafter, when the speed becomes constant, the q-axis current command value Iq ^* becomes constant at a value corresponding to the required torque (= load torque). The value of the d-axis current command value Id ^* is set to zero during the position feedback operation mode because the permanent magnet motor is of a non-salient type.

If the required torque changes during the position feedback operation and the amount of change is large, the response of the speed controller (= change in the q-axis current command value Iq ^* ) is not in time, and the frequency command value ω ^* and the permanent magnet motor Deviation occurs in the actual rotational frequency ωr.

For example, as shown in FIG. 6, if the required torque is suddenly reduced so that the response of the speed controller (= change in the q-axis current command value Iq ^* ) is not in time during the position feedback operation, the frequency command value ω ^* The actual rotational frequency ωr of the permanent magnet motor greatly overshoots, resulting in a problem that the control becomes unstable or the designed maximum rotational speed may be exceeded depending on the application of the motor control device 1.

Further, when the required torque increases rapidly, the actual rotational frequency ωr of the permanent magnet motor decreases with respect to the frequency command value ω ^* , and the response of the speed controller 12a (= q-axis current command value Iq ^* If the change is not in time, the motor stops, which is a problem.

  Further, since the speed controller 12a is generally used as an outer loop, there are cases in which it is more difficult to increase the responsiveness because it is more easily limited by the setting of the response frequency and the like than an inner loop controller (such as ACR). is there.

  In order to solve such a problem, the value of the integral term or the current command value of the speed controller 12a is adjusted to an appropriate value with respect to the necessary torque after the change in accordance with the timing when the necessary torque changes. It is an object of the present invention to suppress speed fluctuations that occur when the torque changes suddenly and greatly.

  A method for realizing the above object will be described.

  The necessary torque is the sum of the acceleration torque and the load torque as described above. Further, the acceleration torque τa when accelerating from the rotational speed N1 [rpm] to the rotational speed N2 [rpm] in the time T [s] can be obtained by the following equation.

[Equation 4]
τa = (Jm + JL) × 2 × π × (N2-N1) / 60 / T (Expression 6)
Here, Jm is the inertia of the motor, and JL is the inertia of the load mechanically connected to the motor.

Further, as an example of a method for obtaining the load torque τL, it can be obtained by the following equation using the relationship with the torque current Iq.
[Equation 5]
τL = {(3/2) × Pm × Ke} × Iq (Expression 7)
Here, Pm is the number of motor pole pairs, Ke is an induced voltage constant, and since both are constants, if the motor current when the motor is rotating at a constant speed (= acceleration torque is zero) is measured, The load torque τL at that time can be known.

  The above method is merely an example, and there is no particular limitation on the method for obtaining the load torque after the change.

  If the required torque after the change can be obtained by (Expression 6) and (Expression 7) or other methods, the corresponding q-axis current value Iqset can be determined from (Expression 7).

  Using the timing at which the required torque changes or stabilizes as a trigger, the q-axis current set value Iqset obtained above is set in the integral term of the speed controller 12a or the q-axis current command value. Thereby, even when the speed controller 12a is restricted by the setting of the response frequency or the like, the speed fluctuation can be suppressed and the permanent magnet motor 3 can be driven stably.

  As another method, there is a method of using the speed controller 12b instead of the speed controller 12a.

  As shown in FIG. 7, the speed controller 12b includes a PI controller 33a used during normal operation, a PI controller 33b in which a q-axis current set value Iqset is set in advance, and a PI controller switching for switching between these PI controllers. Switches 32a and 32b are provided, and the PI controller changeover switches 32a and 32b are used to switch from the PI controller 33a to the PI controller 33b when the required torque changes or stabilizes. The number of PI controllers provided is not necessarily two, and a plurality of PI controllers may be prepared. As a result, similarly in the speed controller 12b, even when the setting of the response frequency or the like is restricted, the speed fluctuation can be suppressed and the permanent magnet motor 3 can be driven stably. In addition, by preparing a plurality of PI controllers, it is possible to select optimal control in a plurality of load states.

A case where the inverter frequency command value ω1 ^* is used will be described as an example of a trigger at the timing when the required torque changes or stabilizes.

The inverter frequency command value ω <b ^> 1 ^* is a value that is obtained from the output of the PLL controller 10 and changes according to the speed fluctuation. As shown in FIG. 8, when a speed change occurs due to a change in the required torque of the motor, the speed change occurrence timing and its change amount Dltω1 (for example, the frequency command ⁾ are observed by observing the inverter frequency command value ω1 ^*. The difference between the value ω ^* and the inverter frequency command value ω1 ^* ). Therefore, if the fluctuation amount of the inverter frequency command value ω1 ^{* is used as} the trigger determination value, the speed fluctuation amount can be limited. That is, when the inverter frequency command value ω1 ^* starts to decrease, the required torque of the motor also decreases. Therefore, the value of the integral term or the current command value of the speed controller 12a may be changed using this timing as a trigger.

According to the present embodiment, even when the required torque changes during the position feedback operation and the change amount is large and the response of the speed controller (= change of the q-axis current command value Iq ^* ) is not in time, Since the integral term of the speed controller 12a or 12b is set to a value corresponding to the required torque after the change, it is possible to suppress speed fluctuations that occur when the required torque changes suddenly and greatly.

  A motor control device according to a second embodiment of the present invention will be described. The configuration of the motor control device in this embodiment is shown in FIG. The description of the components having the same functions as those shown in FIG. 1 already described with reference to FIG. 1 is omitted.

  FIG. 9 includes a control unit 4b, a power conversion circuit 5, and a position sensor 34.

  The position sensor input converter 35 converts, for example, an input from the position sensor 34 such as a Hall IC or an encoder into an actual rotation frequency ωr of the motor rotor, and outputs the actual rotation frequency ωr.

  The control unit 4b includes a speed controller 12c, a voltage command value generator 16, a dq / 3 phase converter 17, a position sensor input converter 35, and a timer 36.

Similar to the speed controller 12a, the speed controller 12c receives the frequency command value ω ^* and the inverter frequency command value ω1 ^* , and outputs a q-axis current command value Iq ^* by the proportional controller and the integral controller.

  As shown in FIG. 10, the speed controller 12c is different from the speed controller 12a in that a PI controller 33c, a PI controller 33d having a response frequency different from that of the PI controller 33c, and a PI controller for switching between them. A changeover switch is provided, and the PI controller 33d is switched from the PI controller 33c with a timing at which the required torque changes or stabilizes as a trigger. The number of PI controllers provided is not necessarily two, and a plurality of PI controllers may be prepared.

  Here, a reciprocating compressor is taken as an example of a problem that occurs when the motor control device described in Patent Document 1 is used for a drive motor for a machine such as a compressor or a pump whose load torque changes periodically. explain.

  In a reciprocating compressor, a compression process and an expansion process are repeated by a piston in accordance with a rotation period of a compressor driving motor. At this time, the load torque of the motor is usually larger in the compression process than in the expansion process. That is, the load torque varies alternately and periodically.

  Further, as shown in FIG. 11, the compressor has a pressure equalization state in which there is almost no pressure difference between the input and output sides of the compressor and a differential pressure state in which there is a pressure difference. When the motor is started in the differential pressure state, the load fluctuation range in the compression / expansion process is larger than that in the pressure equalization state. However, regardless of the pressure state, the load fluctuation width becomes smaller and a steady state is reached after a certain period of time.

As shown in FIG. 12, a case is considered where the load torque fluctuates alternately in magnitude during the position feedback operation. At the timing when the load torque fluctuates small, the speed controller 12c cannot instantaneously adjust the q-axis current command value Iq ^* , so the rotational frequency ωr of the motor rotor temporarily increases. The speed controller 12c adjusts the q-axis current command value Iq ^* to be small in order to make the inverter frequency command value ω1 ^* coincide with the frequency command value ω ^* . On the other hand, at the timing when the load torque increases, the reverse phenomenon occurs, the rotational frequency ωr of the motor rotor decreases, and the q-axis current command value Iq ^* increases.

The value of the frequency command value ω ^* continues to increase uniformly until the target rotational speed is reached. For this reason, when the rotational frequency ωr of the motor rotor temporarily decreases, the difference between the frequency command value ω ^* and the inverter frequency command value ω1 ^* increases, and the control may become unstable.

  In addition, when the motor is started (especially when the motor is started in a state where there is a differential pressure), the variation range of the load torque is large, so the speed fluctuation range of the motor is also large. In some cases, the rotational frequency ωr decreases and the motor stops.

In order to solve this problem, in this embodiment, as shown in FIG. 13, the response frequency of the PI controller of the speed controller 12c is switched as a trigger for the timing at which the required torque changes or stabilizes. While the load torque fluctuation is large, the response frequency of the PI controller of the speed controller 12c is switched to the lower side to suppress the fluctuation of the q-axis current command value Iq ^* caused by the fluctuation of the motor rotor speed caused by the load torque fluctuation. In other words, the q-axis current command value Iq ^* can be prevented from fluctuating more than necessary for the load torque fluctuation while maintaining the followability to the frequency command value ω ^* . For example, this is particularly effective when the speed command at startup increases at the same rate every time regardless of the load.

  In the present embodiment, a case where a timer is used will be described as an example of a trigger at which the required torque changes or stabilizes.

  In the case of a system in which the torque changes or stabilizes over a certain period of time as in the above-described compressor, the time required until that time is prepared in advance as a set value (TrigOnTime in the figure is a set value), and a timer To determine by counting. A trigger is used when the count value exceeds the set value. As a result, the response frequency of the PI controller can always be switched at a constant timing, and a stable control system can be obtained. Further, the elapsed time set in the timer may be counted from the time of starting the motor, or may be counted from the middle of operation. In addition, by preparing multiple set times according to the pressure and temperature conditions on the compressor input and output side at start-up and using appropriate set values, stable start-up can be achieved even under various load conditions. Characteristics can be obtained.

  Next, in the present embodiment, a case where the actual rotational frequency ωr of the motor rotor is used as an example of a trigger at the timing when the required torque changes or stabilizes will be described.

  In the case of a control configuration including a position sensor as shown in FIG. 9, the actual rotation frequency ωr of the motor rotor can be obtained from the output of the position sensor. The rotational frequency ωr changes in response to the occurrence of motor torque fluctuation. Therefore, by observing the fluctuation of the rotation frequency ωr, that is, the fluctuation width of the rotation frequency ωr is smaller than a certain determination value, or the variation amount of the fluctuation width of the rotation frequency ωr is smaller than a certain determination value. It is possible to estimate whether the required torque has changed or stabilized based on the determination that

  Therefore, if the rotational frequency ωr is used as a trigger for the timing at which the required torque changes or stabilizes, the motor control device of this embodiment can be used at an appropriate timing even when the torque fluctuation occurs at an irregular timing. The response frequency of the PI controller can be switched, and control stability can be maintained.

  As described above, according to the present embodiment, it is possible to suppress a decrease in the rotational frequency ωr of the motor rotor even when the load torque periodically fluctuates during the position feedback operation. Will improve.

  A third embodiment of the motor control device according to the present invention will be described. The configuration of the motor control device in this embodiment is shown in FIG. The description of the components having the same functions as those shown in FIG. 1 already described with reference to FIG. 1 is omitted.

The configuration of the speed controller 12d in FIG. 14 is shown in FIG.
Similarly to the speed controller 12a, the speed controller 12d receives the frequency command value ω ^* and the inverter frequency command value ω1 ^* as input, and obtains a q-axis current command value by the proportional controller and the integral controller.

As a difference from the speed controller 12a, the speed controller 12d uses the q-axis current command lower limit value IqStarLimit to perform a q-axis current command value limit determination process and outputs a q-axis current command value Iq ^* . The limit determination process for the q-axis current command value is performed until the load torque fluctuation reaches a steady state, and the limit determination process is not performed when the steady state is reached. The limit determination process is switched using a control switch.

In this embodiment, as shown in FIG. 16, a lower limit value IqStarLimit is provided for the q-axis current command value to limit the q-axis current command value. As a result, even during a period in which the required torque is reduced due to load torque fluctuation, it is possible to limit the amount of decrease in the q-axis current command value Iq ^* , and during the limit determination processing (the period during which the limit function is ON in FIG. 16). Torque equal to or greater than the q-axis current command lower limit value IqStarLimit can be obtained. Thereby, acceleration performance above a certain level can be obtained. Therefore, for example, it is particularly effective when it is desired to shorten the activation time.

In the present embodiment, a case where the frequency command value ω ^* is used as a trigger for timing when the required torque changes or stabilizes will be described.

The frequency command value ω ^* increases to the target rotational speed with a certain inclination as shown in FIG. Therefore, by setting the frequency command value ω ^* when the load torque fluctuation is in a steady state as a trigger in advance, the limit determination processing function for the q-axis current command value can be turned ON / OFF at a constant timing. it can. Of course, the ON / OFF of the limit determination processing function may be performed from another control device connected to the motor control device of this embodiment.

  According to the present embodiment, even when the load torque fluctuates periodically during position feedback operation, it is possible to suppress a decrease in the rotational frequency ωr of the motor rotor, and to obtain acceleration performance above a certain level. be able to.

  A motor control device according to a fourth embodiment of the present invention will be described. FIG. 17 shows the configuration of the motor control device in this embodiment. The description of the components having the same functions as those shown in FIG. 1 already described with reference to FIG. 1 is omitted.

The configuration of the speed controller 12e in FIG. 15 is shown in FIG. As with the speed controller 12a, the speed controller 12e receives the frequency command value ω ^* and the inverter frequency command value ω1 ^* as input, and obtains a q-axis current command value using a proportional controller and an integral controller.

The speed controller 12e is different from the speed controller 12a in that the speed controller 12e adds a difference DltIqc between the q-axis detection current Iqc and the qc-axis current addition determination value IqcLimit to the output value of the PI controller, and the q-axis current command value Iq ^* Is output. Further, the execution of the DltIqc addition process is determined by a trigger. That is, the process is performed until the load torque fluctuation reaches a steady state, and when the steady state is reached, the addition process is not performed. The addition process is switched using the control switch 11d.

Since the value of the frequency command value ω ^* increases with a certain slope until the target rotational speed is reached, when the load torque changes suddenly, the difference between the frequency command value ω ^* and the rotational frequency ωr increases and control is performed. It may become unstable and the motor may stop.

  In the present embodiment, as shown in FIG. 19, the control with the response frequency as designed is performed by adding the difference DltIqc between the q-axis detected current and the qc-axis current addition determination value IqcLimit to the q-axis current command value. However, the shortage of the q-axis current command value caused by torque fluctuation can be compensated. When the shaft error Δθc occurs, a part of the current flowing through the q-axis of the motor is detected as the d-axis detection current Idc depending on the magnitude of the shaft error Δθc, so that the q-axis detection current Iqc is apparently small. May be detected. However, as in the present embodiment, by providing the qc-axis current addition determination value IqcLimit, a certain current or more flows through the q-axis of the motor, and a torque corresponding to that amount can be obtained. Thereby, acceleration performance above a certain level can be obtained. Therefore, for example, this is particularly effective when it is desired to shorten the start-up time even in a device in which the inertia of the motor is small and the shaft error Δθc is likely to occur.

  In the present embodiment, a description will be given of a case where the axis error Δθc is used as a trigger for timing when the required torque changes or stabilizes.

When the required torque increases rapidly, the controller (PLL controller 10 or speed controller 12c, etc.) cannot adjust the inverter frequency command value ω1 ^* or the q-axis current command value Iq ^* instantaneously. The rotational frequency ωr of the rotor is reduced. The relationship between the motor shaft and the control shaft at this time is that the motor shaft is delayed in the rotation of the motor with respect to the control shaft. That is, the axis error Δθc changes in the positive direction. On the other hand, when the necessary torque is suddenly reduced or when an overshoot occurs in the inverter frequency command value ω1 ^* , the shaft error Δθc changes in the negative direction. Further, when the load torque fluctuation is in a steady state and the control is stabilized, the value of the axis error Δθc is stabilized by the PLL controller 10 at or near zero.

  Therefore, by observing the change in the axis error Δθc, it is possible to know the torque change or the stable timing. As an example of the method, as shown in FIG. 19, if the value of the axis error Δθc is stabilized within the determination value, it can be determined that the load torque fluctuation has become a steady state.

According to the present embodiment, even when the load torque periodically changes during the position feedback operation, it is possible to suppress a decrease in the rotation frequency ωr of the motor rotor, and to achieve a response frequency as designed. The deficiency of the q-axis current command value Iq ^* due to torque fluctuation can be compensated for while being held.

  A motor control device according to a fifth embodiment of the present invention will be described. A case where the motor control device according to the present invention is applied to a refrigerator will be described with reference to the drawings. As shown in FIG. 21, the refrigerator includes a heat exchanger 24, a blower 25, a compressor 26, a compressor driving motor 27, and a refrigerator control device 28.

  The refrigerator control device 28 includes an internal control device 29 that controls a blower, an internal lamp, and the like based on various sensor information, and the motor control device 1. The motor control device 1 includes a control unit 4 a and a power conversion circuit 5. Is done.

  The compressor will be described as a reciprocating compressor that compresses and expands the refrigerant by piston movement.

  In such a configuration, the compressor has a pressure equalization state in which there is almost no pressure difference between the input and output sides of the compressor and a differential pressure state in which there is a pressure difference. When the motor is started in the differential pressure state, the fluctuation range of the load torque in the compression / expansion process becomes larger than that in the pressure equalization state. Further, the fluctuation of the load torque is periodically generated by repeating the compression / expansion process.

  In addition, in a refrigerator, when starting from a compressor stopped state, a speed increasing operation mode that starts at high acceleration in order to suck up oil in the compressor, and a normal operation that operates at low acceleration to reduce the burden on the refrigeration cycle There is an operation mode. Both the speed increase operation mode and the normal operation mode are performed by position feedback operation, and when the speed reaches a predetermined rotation speed by the speed increase operation mode, the operation mode is switched to the normal operation mode.

  Therefore, when the compressor is started from a stopped state in the differential pressure state (hereinafter referred to as differential pressure startup), the load torque due to the differential pressure is large at the time of startup, and the acceleration torque is also large during the acceleration operation mode. The required torque is large.

  However, when a certain amount of time elapses, the load torque due to the differential pressure decreases and stabilizes at a steady load torque. Further, since the acceleration becomes low when the mode is switched to the normal operation mode, the acceleration torque becomes small.

  Therefore, when the differential pressure activation is performed in the refrigerator, a phenomenon occurs in which the necessary torque is large and periodically fluctuates during the activation, and the necessary torque is rapidly reduced during the position feedback operation.

Therefore, when the motor is started, the speed fluctuation of the rotational frequency ωr of the motor rotor is large, the q-axis current command value Iq ^* becomes unstable, and the permanent torque with respect to the inverter frequency command value ω1 ^* becomes permanent at the timing when the required torque decreases rapidly. An overshoot of the actual rotational frequency ωr of the magnet motor occurs. Therefore, control may become unstable and the motor may stop. For this reason, differential pressure activation is one of the problems to be solved in the refrigerator.

As shown in FIG. 20, according to the present invention, the q-axis current command value Iq ^* can be stabilized by switching the response frequency even when there is a periodic load torque fluctuation during the position feedback operation. it can. When the response frequency of the speed controller 12 is low, the q-axis current command value Iq ^* is not changed more than necessary with respect to the load torque fluctuation. Therefore, the q-axis current command value Iq ^* can be avoided from being reduced more than necessary due to load torque fluctuations, and a certain level of acceleration performance can be obtained.

In addition, by setting the q-axis current value Iqset in the integral term of the speed controller using the timing at which the required torque becomes small as a trigger, the actual rotational frequency ωr of the permanent magnet motor exceeds the generated inverter frequency command value ω1 ^* . Shooting can also be suppressed. Usually, the amount of change in the integral term of the speed controller is determined according to the response frequency of the speed controller. Therefore, when a value larger than the value corresponding to the required torque is set as the q-axis current command value Iq ^* and the response frequency of the speed controller is set low, the inverter frequency command value ω1 ^* becomes the frequency command value ω. Even if the value is close to ^* , the decrease in the integral term of the speed controller is slow, so overshoot may occur. Therefore, the overshoot can be suppressed by setting the q-axis current value Iqset in the integral term of the speed controller by a certain trigger. This method is particularly effective when, for example, the change width of the load torque at the time of start-up is large and the q-axis current command value Iq ^* must be set to a large value in accordance with the maximum load in order to avoid start-up failure. It becomes effective. Further, FIG. 20 shows the case where the response frequency of the speed controller is set to a high value by the trigger, but conversely, the case where the response controller is set from a high value to a low value by the trigger is also conceivable. For example, when the start-up time is very short, that is, the acceleration torque is large, but the normal load torque is small and the change width is small, the response frequency of the speed controller is set high only at the time of start-up. Thereby, the start-up in a short time and the stability at the time of normal operation are realizable.

  The case where the estimated value of the required torque is used as a trigger for the timing at which the required torque becomes small will be described.

  As an example of a method for estimating the value of the load torque, there is a method of estimating the value of the load torque from (Equation 7) described above by observing the q-axis detection current value Iqc. Therefore, the load torque value is estimated from the q-axis current detection value Iqc, and the trigger may be used when the estimated value τa is equal to or less than the determination value. Further, the refrigerator control device 28 may estimate the load torque of the compressor from the number of rotations of the blower 25 and the temperature inside the refrigerator or the refrigerator, and give a trigger to the motor control device.

  According to this embodiment, uniform acceleration characteristics are obtained even when the required torque changes suddenly during position feedback operation in the refrigerator compressor (for example, when the compressor has a differential pressure). And smooth start-up can be realized.

  In the first to fifth embodiments, the speed controller 12 has been described for the sake of explanation. However, considering the configuration of the controller, the contents of the present invention can be applied to the current controller 15 as well. It can be easily imagined that the same effect can be obtained when applied to.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, a part of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Further, each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor.

DESCRIPTION OF SYMBOLS 1,28 Motor control apparatus 2,6a, 6b Current detection means 3 Permanent magnet motor 4,4a, 4b, 4c, 4d Control part 5 Power conversion circuit 7 3 phase / dq converter 8 Axis error calculator 9a, 9b, 9c , 9d, 9e, 9f Subtractor 10 PLL controllers 11a, 11b, 11c, 11d Control change-over switches 12a, 12b, 12c, 12d, 12e Speed controller 13 Load estimator 14 Integral term initial value calculator 15a, 15b Current control 16 Voltage command generator 17 dq / 3-phase converter 18 Integrator 20 Inverter 21 DC voltage source 22 Driver circuits 23a, 23b, 23c PWM pulse signal 24 Heat exchanger 25 Blower 26 Compressor 27 Compressor drive motor 28 Refrigerator Control device 29 Internal control device 30 Adder 31a, 31b Response frequency changeover switch 32a, 32b PI controller changeover switch Pitch 33a, 33b, 33c, 33d PI controller 34 position sensor 35 position sensor input transducer

Claims (3)

A calculating means for calculating a value relating to the current command value or a current command value is a quantity of electricity according to the torque of the permanent magnet motor, and a current controller which receives the value of the said current command value or current command value, the current the motor control apparatus having a voltage command value generator which receives the output of the controller, and a power conversion circuit for applying a voltage to the permanent magnet motor according to an output of said voltage command value generator,
Torque of the permanent magnet motor is abruptly changed, or change a trigger timing for stable during position feedback operation mode,
The q-axis current command value or the integral term of the speed controller is set to the q-axis current value necessary to output the necessary torque after the change in accordance with the trigger of the timing when the torque suddenly decreases.
Alternatively, the lower limit function for limiting the lower limit value of the q-axis current command value to the lower limit value is turned OFF in accordance with the trigger of the timing when the torque fluctuation is stabilized.
Alternatively, in accordance with the trigger of the timing when the torque fluctuation is stabilized, the addition function for adding the difference between the q-axis detected current and the qc-axis current addition determination value to the q-axis current command value is turned OFF.
A motor control device characterized by that. In claim 1, as a trigger of the timing when the torque of the motor suddenly changes or the timing when the torque fluctuation of the motor is stabilized,
If the inverter frequency command value starts to decrease,
When the timer counts and the count value exceeds the set value,
When the fluctuation width of the rotation frequency is smaller than the judgment value or the variation amount of the fluctuation width of the rotation frequency is smaller than the judgment value,
If the load torque fluctuation reaches the preset frequency command value when the steady state is reached,
If the axis error value is within the judgment value,
When the load torque value is estimated from the q-axis detected current value, and the estimated load torque value is equal to or less than the determination value,
Any one of the above is used. A refrigeration apparatus comprising a compressor driving device using the motor control device according to claim 1 .

Images