JP5798838B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device and a drive device using the same.

  Japanese Unexamined Patent Publication No. 2006-166658 (Patent Document 1) is known as a prior art of a compressor driving apparatus capable of stably starting a compressor. In Patent Document 1, in response to an instruction to stop the compressor, the rotational speed is gradually decreased, and a phase fixing operation is performed in response to reaching the predetermined rotational speed, and the piston is moved to a predetermined position. A configuration for stopping is disclosed.

  Japanese Patent Laid-Open No. 2005-90466 (Patent Document 2) is known as a prior art of a reciprocating compressor drive device without starting failure. Patent Document 2 discloses a configuration in which a driving current is supplied to a comp motor in one phase based on a starting motor constant before starting, and a stator position is waited at a starting initial position, and then starting from this starting initial position is started. Is disclosed.

JP 2006-166658 A JP 2005-90466 A

  Patent Document 1 describes a mechanism for stopping a piston at a predetermined position. However, the compressor driving device of Patent Document 1 does not take into consideration the case where the piston moves from the stop position or the change in load characteristics.

  Therefore, an object of the present invention is to provide a motor control device that stably drives a motor regardless of the stop position and when the load characteristic changes, and a drive device using the motor control device.

  Patent Document 2 describes a mechanism for waiting the rotor position at the starting initial position. However, the compressor driving device of Patent Document 2 only considers a specific type of compressor.

  Accordingly, an object of the present invention is to provide a motor control device applicable to a device whose load torque characteristics change periodically regardless of the compressor, and a drive device using the motor control device.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present invention includes a plurality of means for solving the above-mentioned problems. For example, a synchronous operation mode that does not use information about the rotational angle position and a position sensorless operation mode that uses the information about the rotational angle position to drive. And a periodic torque estimating means for estimating a periodic torque component that varies in one mechanical angle cycle or an integer multiple of one mechanical angle cycle, wherein the inclination of the periodic torque is zero. The operation mode is switched in the vicinity or in a negative period.

  According to the present invention, it is possible to provide a motor control device that can be applied regardless of the stop position and when the load characteristic changes, and a drive device using the motor control device. Further, it is possible to provide a motor control device applicable to a device whose load torque characteristics change periodically regardless of the compressor, and a drive device using the motor control device.

It is an example of the block diagram of a motor control apparatus. It is explanatory drawing of a coordinate axis. It is an example of a block diagram of a power converter circuit. It is an example of the block diagram of a compression mechanism part. It is an example of the change of the load torque with respect to the position of a rotor. It is an example of an operation mode. It is an example of a block diagram of a PLL controller. It is an example of the block diagram of a speed controller. It is an example of the related figure of a real axis and a control axis when the load is light. It is an example of the relationship figure of a real axis and a control axis when a load is heavy. It is an example of the operation mode figure in case a load is light. It is an example of the operation mode figure in case a load is heavy. It is an example of the block diagram of a period torque estimation means. It is an example of another block diagram (voltage command value utilization type) of a period torque estimation means. It is an example of another block diagram (current envelope utilization type) of a period torque estimation means. It is an example of the block diagram of a drive device. It is an example of the enlarged view of control mode switching timing. It is an example of the block diagram of a simple torque estimation means. It is an example of the relationship diagram of a control axis and a three-phase axis. It is an example of the relationship diagram of load torque and a pulsation component extraction value. It is an example of the simulation result of the period torque estimation means 30a. It is an example of the simulation result of the period torque estimation means 30b. It is an example of the simulation result of the period torque estimation means 30c.

  Embodiments of the present invention will be described below with reference to the drawings.

  In this embodiment, an example of a motor control device 1 that drives a compressor will be described.

  FIG. 1 is an example of a configuration diagram of a motor control device 1 of the present embodiment. The motor control device 1 is roughly divided into a current detection unit 12 that detects a current flowing through the motor (electric motor) 6 and a control that calculates a voltage command value to be applied to the motor 6 based on current information detected by the current detection unit 12. Unit 2, power conversion circuit 5 that applies a voltage to motor 6 according to the voltage command value, and compression mechanism unit 500 that is mechanically connected to motor 6.

  In this embodiment, a permanent magnet motor having a permanent magnet in the rotor is used as the motor 6. Therefore, description will be made assuming that the position of the control shaft and the position of the rotor are basically synchronized. The rotational angle position information of the rotor is obtained by position sensorless control that is estimated based on information such as a current flowing through the motor and a motor applied voltage. At that time, the position of the rotor in the magnetic flux direction is the d-axis, and the virtual rotor position dc on the control with respect to the d-q axis (rotating coordinate system) consisting of the q-axis that is electrically advanced 90 degrees in the rotation direction therefrom The control is basically based on a dc-qc axis (rotating coordinate system) consisting of an axis and a qc axis that is electrically advanced 90 degrees in the rotation direction therefrom. The relationship between these axes is shown in FIG. In the following description, the dq axis is called a real axis and the dc-qc axis is called a control axis.

FIG. 19 shows the relationship between the three-phase axis, which is a fixed coordinate system, and the control axis. With reference to the U phase, the rotation angle position (magnetic pole position) θ _dc of the dc axis is defined. The dc axis rotates in the direction of the arrow in the figure, and the magnetic pole position θ _dc can be obtained by integrating the rotation frequency (inverter frequency command value ω _1, which will be described later).

  The current detection unit 12 detects a current flowing in the U phase and the W phase among the three-phase AC current flowing in the motor 6. Although all phases of AC current may be detected, if one of the three phases can be detected from Kirchhoff's law, the other one phase can be calculated from the detected two phases.

  As another method for detecting the AC current flowing through the motor 6, for example, a single shunt for detecting the AC side current of the power conversion circuit 5 from a DC current flowing through a shunt resistor added to the DC side of the power conversion circuit 5 described later. There is a current detection method. This method uses the fact that the current flowing through the shunt resistor changes with time depending on the energization state of the switching elements constituting the power conversion circuit 5. Although not shown, there is no problem even if a single shunt current detection method is used for the current detection means 12.

The control unit 2 includes a 3φ / dq converter 8 that performs coordinate conversion of the AC current detection values (I _u and I _w ) on the three-phase axis to current detection values on the control axis, and a current detection value (I _dc on the control axis). And I _qc ) and voltage command values (V _d ^* and V _q ^* ), an axis error calculator 10 for calculating an axis error Δθ _c (shown in FIG. 2) between the real axis and the control axis, and periodically Periodic torque estimation means 30 for estimating the fluctuating load torque, and the frequency of the voltage applied to the motor 6 (inverter frequency command value ω ₁ ) to cause the shaft error Δθ _c to follow the shaft error command value Δθ ^* (usually zero). ), A control changeover switch (16a and 16b) for switching operation modes, which will be described in detail later, a control changeover decision unit 31, a voltage command value generator 3, and a voltage command value on the dq axis. coordinate transformation from (V _d ^* and V _q ^*) to the control shaft to the three-phase axes That dq / 3 [phi] converter 4, the current controller 112, and the like integrator 9.

  Most of the control unit 2 is configured by a semiconductor integrated circuit (arithmetic control means) such as a microcomputer or a DSP, and is realized by software or the like.

  As shown in FIG. 3, the power conversion circuit 5 includes an inverter 21, a DC voltage source 20, and a driver circuit 23. The inverter 21 is configured by a switching element 22 (for example, a semiconductor switching element such as IGBT or MOS-FET). These switching elements 22 are connected in series and constitute upper and lower arms of the U phase, the V phase, and the W phase. The connection point of the upper and lower arms of each phase is wired to the motor 6. The switching element 22 performs a switching operation according to the pulsed drive signals (24a to 24f) output from the driver circuit 23. By switching the DC voltage source 20, an AC voltage having an arbitrary frequency is applied to the motor 6 to drive the motor.

  When the shunt resistor 25 is added to the DC side of the power conversion circuit 5, it can be used for an overcurrent protection circuit for protecting the switching element 22 when an excessive current flows, a single shunt current detection method, or the like.

  As shown in FIG. 4, the compression mechanism 500 drives the piston 501 using the motor 6 as a power source. Thereby, a compression operation is performed. A crankshaft 503 is connected to the shaft 502 of the motor 6 to convert the rotational motion of the motor 6 into linear motion. As the motor 6 rotates, the piston 501 also operates to perform a series of steps such as suction, compression, and discharge. First, the refrigerant is sucked from the suction port 505 provided in the cylinder 504. Thereafter, the valve 506 is closed to perform compression, and the compressed refrigerant is discharged from the discharge port 507.

  In a series of steps, the pressure applied to the piston 501 changes. This means that the load torque changes periodically when viewed from the motor 6 that drives the piston. FIG. 5 shows an example of a change in load torque with respect to the rotor position in one mechanical angle cycle. In FIG. 5, an example of a four-pole motor is shown as the motor 6, so that two electrical angle cycles correspond to one mechanical angle cycle. Although the relationship between the position of the rotor and the position of the piston varies depending on the assembly, FIG. 5 shows the change from the bottom dead center of the piston. It is characteristic that when the compression process starts, the load torque increases, and in the discharge process, the load torque decreases rapidly. From FIG. 5, it can be seen that the load torque fluctuates during one rotation, and the load torque fluctuates every rotation. Therefore, when viewed from the motor 6, the load torque fluctuates periodically.

  Even if the same compression mechanism 500 is used, the load torque varies due to various factors such as the number of rotations of the motor 6, the pressure of the suction port 505 and the discharge port 507, and the pressure difference between the suction port 505 and the discharge port 507. There are changing characteristics. Further, the relationship between the opening / closing timing of the valve 506 and the position of the piston varies depending on the configuration of the valve 506, and varies depending on the pressure condition depending on the valve 506.

A basic operation when starting the motor 6 will be described, and then a problem when there is a periodic pulsation torque such as a compressor will be described. FIG. 6 is an example of an operation mode showing transition of each operation mode when starting the motor 6. The operation mode includes a positioning mode in which a direct current is supplied to a motor winding of an arbitrary phase to fix the stator of the motor 6 at a certain position, a d-axis current command value I _d ^*, and a q-axis current command value I _q ^*. And a synchronous operation mode for determining a voltage to be applied to the motor 6 based on the frequency command value ω ^*, and a position sensorless mode for adjusting the inverter frequency command value ω ₁ so that the axis error Δθ _c becomes zero. .

In these operation modes, one or more of the d-axis current command value (I _d ^* ), the q-axis current command value (I _q ^* ), and the inverter frequency command value ω ₁ are changed, or the control unit 2 By switching the provided control changeover switches (16a and 16b), a transition is made to another operation mode. Note that the two control changeover switches (16a and 16b) are simultaneously switched unless otherwise specified.

In the positioning mode, the control changeover switches (16a and 16b) are set to the A side. That is, the frequency command value ω ^* becomes the inverter frequency command value ω ₁ as it is. Further, the q-axis current command value I _q ^* ₀ (given from the host controller or the like or determined in advance in the control unit 2) becomes the q-axis current command value I _q ^* as it is. In the positioning mode d, since a direct current flows through the motor 6, the inverter frequency command value ω ₁ is set to zero. On the other hand, the d-axis current command value I _d ^* is increased in a linear function with time. Of course, there is no problem in giving the d-axis current command value I _d ^* other than that shown in FIG. Further, the phase to be positioned may be fixed to a specific phase, or may be a phase that is different every time it is started. In other words, the magnetic pole position θ _dc in the positioning mode may be changed at each activation. For example, when θ _{dc is set} to zero, positioning is performed in the U phase.

After the positioning mode ends, the mode changes to the synchronous operation mode. The control changeover switches (16a and 16b) remain on the A side. In the synchronous operation mode, the d-axis current command value I _d ^* remains at a constant value (this activation method is called “d-axis activation”), and the inverter frequency command value ω ₁ is increased. As a result, the motor 66 accelerates following the inverter frequency command value ω ₁ .

Transition to the position sensorless mode is made by setting the control switch (16a and 16b) to the B side. In the position sensorless mode, the PLL controller 13 operates to adjust the inverter frequency command value ω ₁ so that the shaft error Δθ _c becomes the shaft error command value Δθ ^* (usually zero). At the same time, the speed controller 14 adjusts the q-axis current command value I _q ^* so that the difference between the frequency command value ω ^* given from others such as the host controller and the inverter frequency command value ω ₁ becomes zero.

The permanent magnet motor of this embodiment is a non-salient pole type. Therefore, the reluctance torque generated due to the difference in inductance between the d axis and the q axis is not taken into consideration. Therefore, the torque generated by the motor 6 is proportional to the current flowing through the q axis. Further, the d-axis current command value I _d ^* in the position sensorless mode is set to zero.

In the case of the salient pole type, in addition to the torque due to the q-axis current, there is a reluctance torque caused by the difference in inductance between the d-axis and the q-axis, so the d-axis current command value I _d ^* is set in consideration thereof. Thus, the same torque can be generated with a small q-axis current.

A configuration example of the PLL controller 13 is shown in FIG. The difference between the axis error command value Δθ ^* and the axis error Δθ _c is obtained by the subtractor 11a, and this is multiplied by the proportional gain _{Kp_pll,} and the calculation result of the proportional operation unit 42a for proportional control is multiplied by the integral gain K _{i_pll} for integral control. a calculation result of the integration unit 43a which is added by the adder 18a, and outputs the inverter frequency command value omega _1.

A configuration example of the speed controller 14 is shown in FIG. The difference between the frequency command value ω ^* and the inverter frequency command value ω ₁ is obtained by the subtractor 11b, multiplied by the proportional gain _{Kp_asr} , and the result of the proportional operation unit 42b that performs proportional control and the integral gain K _{i_asr} are multiplied and integrated. The adder 18b adds the calculation results of the integral calculation unit 43b to be controlled, and outputs the q-axis current command value I _q ^* .

  The example of the operation mode diagram shown in FIG. 6 is a schematic diagram showing the relationship between the control switch (16a and 16b) and each value. Actually, each value changes according to the load (load torque) of the motor 6, the PLL controller 13, the current controllers 42 and 43, and the response frequency (proportional gain or integral gain) of the speed controller 14. Hereinafter, the behavior when the load torque fluctuates when shifting from the synchronous operation mode to the position sensorless mode will be described in detail with reference to FIGS. 9 to 12. It is assumed that the current controller is an ideal controller, and that the current according to the current command value flows through the motor 6.

First, the case where the load of the motor 6 is light will be described. When d-axis activation is employed, the axis error Δθ _c in the synchronous operation mode is a value near zero. In the synchronous operation mode, since control is not performed using the rotation angle position information (or position estimated value) of the rotor, an axis error (load angle) is generated so that the generated torque of the motor 6 and the load torque are balanced. This will be described below using the example of the relationship diagram between the real axis and the control axis shown in FIG. The d-axis current command value I _d ^* is flowing on the dc axis. The torque generated by the motor 6 is proportional to the q-axis current. When the load is light, the q-axis current may be small, so the load angle is small.

  On the other hand, when the load is heavy, the load angle increases as shown in FIG. As a result, a large current flows through the q axis, and the motor 6 generates a larger torque.

Next, the movement of each value when shifting to the position sensorless mode will be described when the load is light (FIG. 11) and when the load is heavy (FIG. 12). As described above, when shifting to the position sensorless mode, the PLL controller 13 and the speed controller 14 operate. At this time, since the axis error Δθ _c is a positive value, the inverter frequency command value ω ₁ is decreased. As a result, the difference between the frequency command value ω ^* and the inverter frequency command value ω ₁ becomes a negative value, and the speed controller 14 increases the q-axis current command value I _q ^* . As a result, the inverter frequency command value ω ₁ follows the frequency command value ω ^* .

On the other hand, when the load is heavy, the shaft error Δθ _c in the synchronous operation mode becomes a larger positive value. Therefore, when the mode is shifted to the position sensorless mode and the PLL controller 13 operates, the inverter frequency command value ω ₁ is further lowered. In some cases, the voltage drops to near zero, which causes the motor 6 to step out and cause a start failure. As shown in FIG. 5, since the periodic load fluctuation is particularly large in the compressor, the timing and position at which the load temporarily increases due to the periodic load fluctuation even if the average load torque for one cycle of the mechanical angle is small. When the timing for switching to the sensorless mode overlaps, there is a high possibility that the activation will fail. Therefore, it is one of the objects of this embodiment to start the motor 6 stably without failing to start even when the periodic load fluctuation is large.

  In the present embodiment, the piston 501 of the compression mechanism unit 500 is described as an example of a reciprocating type that moves linearly. However, as another method of the compression mechanism, a rotary type that compresses by rotating the piston, a spiral type, or the like There are scroll types that consist of a swirling wing. Although the characteristic of periodic load fluctuation varies depending on the compression method, there is load fluctuation caused by the compression process in any compression method. Therefore, there is a possibility that the start failure may occur due to the overlap of the timing at which the load temporarily increases due to the periodic load fluctuation and the operation mode switching timing. Therefore, one of the objects of the present embodiment is to provide a solution applicable to any compression method. The variation of the load torque varies depending on the type of the compressor, and even in the same compressor, it varies depending on the operation conditions (pressure of the suction port and the discharge port, the temperature of the compressor, etc.) and the rotational speed of the motor. For this reason, it is better to determine the switching timing from actual load fluctuations than to determine the switching timing in advance, and this is one of the purposes of this embodiment.

  The periodic torque estimation means 30 and the control switching determination unit 31 which are one of means for realizing these objects will be described. Since there are several examples of these configurations, each will be described.

The periodic torque estimating means 30 estimates a load torque component that varies periodically based on the current information detected by the current detecting means 12. In the periodic torque estimation means 30a shown in FIG. 13, the q-axis current detection value I _qc obtained by the 3φ / dq converter 8 is converted into a coordinate system that rotates at the mechanical angular frequency ω _m using the single-phase coordinate converter 32. Perform coordinate transformation.

For example, when the number of magnetic poles of the rotor of the motor 6 is 4, the electrical angle 2 period corresponds to the mechanical angle 1 period. Therefore, the mechanical angular frequency ω _m can be obtained by dividing the frequency command value ω ^* (electrical angle) by the number of pole pairs of the motor 6 (= number of poles / 2). In this embodiment, the frequency command value ω ^* is used to obtain the mechanical angular frequency, but the inverter frequency command value ω ₁ may be used.

  Coordinate conversion is performed using the following equation.

As a result, the cos component (I _{qc_cos} ) and the sin component (I _{qc_sin} ) of the mechanical angular frequency ω _m are extracted from the q-axis current detection value I _qc . A constant pass filter (LPF) 35 is added when it is desired to remove higher-order components of fluctuations in load torque or to remove noise in the current detection value. Thereafter, coordinate transformation is performed again using the following equation.

By adding the operation result to each other, among the q-axis current detection value I _qc, components of mechanical angular frequency ω _m (I _qm) is extracted. That is, by observing the change in the output of the single-phase coordinate converter, it is possible to estimate a periodic change in load torque that varies at the mechanical angular frequency ω _m .

This series of movement will be described with reference to FIG. Since the position information is not fed back in the synchronous operation mode, when the load torque fluctuates, the motor torque follows the load torque by changing the load angle as described above. At this time, when current control is not performed, a current corresponding to the load angle flows as _indicated by I _{qc in} FIG. When the component of the mechanical angular frequency ω _m of the q-axis current detection value I _qc is extracted by the periodic torque estimation means 30a, a waveform like the pulsation component extraction value I _qm is _obtained .

Next, the output of the periodic torque estimating means 30a is input to the control switching determination unit 31a. Conventionally, from the synchronous operation mode to the position sensorless mode, for example, the operation mode is switched when the frequency command value ω ^* reaches a predetermined value or a predetermined time elapses. In such a conventional operation mode switching determination, there is a possibility that the timing at which the load temporarily increases due to periodic load fluctuations overlaps with the operation mode switching timing. Therefore, based on the output of the single-phase coordinate converter, a signal is output to the control switch 16 when the change in the load torque is near zero or the conventional operation mode switching determination is established in the period when the load torque decreases. Then, the operation mode is switched to the position sensorless mode. For example, a signal is output to the control switch 16 when the pulsation component extraction value I _qm shown in FIG.

As a result, since the mode is switched to the position sensorless mode in a period in which the load torque fluctuation is small, that is, in a period in which the fluctuation of the axis error Δθ _c is small, the motor 6 can be stably started without starting failure.

A waveform of each part of the control switching determination unit 31a and a simulation result waveform are shown in FIG. It can also be seen from the simulation result waveform that the pulsation component extraction value I _qm is very close to the change in the load torque by using the periodic torque estimating means 30a. When the operation mode is switched when the switching determination value is equal to or less than the switching determination value, the motor 6 can be stably started without failing to start because the mode is switched to the position sensorless mode in a period when the load torque fluctuation is small.

Another configuration example of the periodic torque estimation means and the control switching determination device will be described with reference to FIG. The dq-axis voltage command values (V _d ^* and V _q ^* ) are input to the periodic torque estimation means 30b shown in FIG. Since the dq axis voltage command value is a value on the control axis, it usually has a direct current component. However, when there is a periodic load variation, the current control controls the dq axis current to be constant, so the voltage command value on the control axis also varies. Therefore, the voltage command value is input to the periodic torque estimation means 30b, and the fluctuation of the voltage command value is extracted, or the differential value of the voltage command value is output to the control switching determination unit 31b using the incomplete differentiator 34.

FIG. 22 shows a result of calculating incomplete differential values (V _d ^* _{_div} and V _q ^* _{_div} ) of the dq-axis voltage command value using the configuration of FIG. As can be seen from this waveform, the fluctuation of the load torque can also be estimated from the differentiation of the voltage command value.

  The control switching determination unit 31b is configured to switch the switching determination value in a period in which the variation of the voltage command value or the differential value of the voltage command value is near zero, or the differential value of the voltage command value is negative, or as shown in FIG. In the following period, when the conventional operation mode switching determination is established, a signal is output to the control switch 16 to switch the operation mode to the position sensorless mode. Thereby, since it switches to position sensorless mode in the period when load torque fluctuation is small, the motor 6 can be started stably without starting failure.

  Here, the voltage command value generator 3 can be expressed by the following equation.

Here, R is the winding resistance value of the motor 6, L _d is the d-axis inductance, L _q is the q-axis inductance, and K _e is the induced voltage constant.

  Considering the above equation for calculating the voltage command value, the q-axis voltage command value is more influenced by the cyclic fluctuation torque than the d-axis voltage command value, so that it is more effective to input the q-axis voltage command value. . Further, not the voltage command value on the control axis, but the square sum of squares of the d-axis voltage command value and the q-axis voltage command value is calculated, in other words, the amplitude value of the voltage command value is calculated, and this is calculated as a control switching determination device. The same effect can be obtained even if it is input to 31b. In addition, the drive signal 24 for driving the switching element of each phase may be input to the periodic torque estimating unit 30b. For example, when the drive signal 24 is input, a larger voltage is required in a period in which the load torque is large, so that the switching duty is increased (the pulse width of the drive signal is widened). That is, the width of the drive signal during a heavy load changes from that of other periods.

A description will be given of another configuration example of the periodic torque estimating means and the control switching determination unit that is effective when current control is not performed in the synchronous operation mode, with reference to FIG. When current control is not performed, the voltage applied to the motor 6 has a predetermined value. In this case, the amplitude value of the current (I _u , I _v , I _w ) on the three-phase axis changes depending on the load angle that changes according to the load. Therefore, the current value of each phase detected by the current detection unit 12 is input to the periodic torque estimation unit 30c. The envelope detector 34 detects an envelope of a three-phase alternating current and outputs it to the control switching determination unit 31c.

  FIG. 23 shows a relationship diagram between the load torque and the three-phase alternating current obtained by simulation. As can be seen from FIG. 23, it can be seen that the envelope changes at the timing when the load increases.

  The control switching determination unit 31c outputs a signal to the control changeover switch 16 when the conventional operation mode switching determination is established during a period in which the envelope variation is substantially constant or the envelope increases. To the position sensorless mode. Thereby, since it switches to position sensorless mode in the period when load torque fluctuation is small, the motor 6 can be started stably without starting failure.

  As described above, by using any one of the configuration examples of the periodic torque estimation unit 30 and the control switching determination unit 31, the mode is switched to the position sensorless mode in a period in which the load torque fluctuation is small, so that the startup is not failed and stable. The motor 6 can be started. In order to estimate the variation of the load torque, it is apparent that the present invention is applicable to any compression method without being limited to a specific compressor method.

The suction pressure P _s and the discharge pressure P _d in one step of the compressor of the motor 6 vary depending on the state of the system (for example, the refrigeration cycle) to which the compressor is connected, but load torque fluctuations in one step occur. Therefore, it is applicable to motor control devices having various load characteristics by estimating the load torque fluctuation and using the information for the operation mode switching determination.

  Needless to say, the present invention can be applied not only to the compressor but also to a motor control device having a load torque characteristic that varies periodically.

  In the above description, an example in which the shaft of the motor 6 is connected to the piston 501 of the compression mechanism unit 500 via the crankshaft 503 is used. For this reason, a series of steps as a compressor has one mechanical angle cycle, and as a result, the variation in load torque is one mechanical angle cycle. For example, when a gear is added between the shaft of the motor 6 and the crankshaft 503, the variation of the load torque varies at an integral multiple of one cycle of the mechanical angle. Also in this case, if the fluctuation cycle of the load torque is known in advance, the contents described in this embodiment can be applied and the same effect can be obtained.

  Further, when the motor 6 is decelerated, that is, when the operation mode is switched from the position sensorless mode to the synchronous operation mode, the contents described in the present embodiment can be applied, and similar effects can be obtained.

  In the present embodiment, an example of a motor control device that can estimate a variation in load torque even when the startup time is short will be described.

  FIG. 16 is an example of a configuration diagram illustrating a refrigerator using the motor control device 1 according to the second embodiment.

  In addition, description is abbreviate | omitted about the part which has the same code | symbol shown by Example 1 already demonstrated, and the part which has the same function.

  As shown in FIG. 16, the refrigerator 301 includes a heat exchanger 302, a blower 303, a compressor 304, a compressor driving motor 305, and the like. The refrigerator control device 306 includes an internal control device 307 and a motor control device 1 that control a blower, an internal light, and the like based on various sensor information.

  In the refrigerator, when the compressor is started from a stopped state, it is necessary to start the compressor in a short time (at a high acceleration rate) because the lubricating oil is sucked into the cylinder. In this case, if it takes a long time to detect periodic load fluctuations, there is a concern that the start-up time may be delayed. Therefore, even when the start-up time is short, one of the objects of this embodiment is to provide a solution that can switch to the position sensorless mode and start the motor stably during the period when the gradient of the load torque is near zero or negative. It is.

  Hereinafter, explanation will be given using the enlarged view of the control mode switching timing of FIG. When the motor has more than two poles, the electrical angle has a plurality of cycles. For example, when the motor 6 has four poles, two electrical angles are one mechanical angle. Therefore, when DC positioning is performed in the positioning mode, even if it is electrically the same position (d-axis), it is mechanically positioned at different positions (for example, 0 degrees and 180 degrees in mechanical angle). . In this state, a transition is made to the synchronous operation mode, and acceleration is performed according to a preset acceleration rate.

When the inverter frequency command value ω ₁ (or frequency command value ω ^* ) reaches the sensorless switching speed (switching timing indicated by a thick arrow in FIG. 17), the control switch is switched to shift to the position sensorless mode. . FIG. 17 shows a temporal enlarged view at this time.

  The lower left side (Example 1) of FIG. 17 is an example in the case where the sensorless switching rotation speed achievement timing does not overlap with a period in which the load fluctuation is large. At this time, since the load fluctuation is small, the control mode can be switched stably.

On the other hand, the lower right side (example 2) of FIG. 17 is an example in the case where the sensorless switching rotation speed achievement timing overlaps with a period in which the load fluctuation is large. In this case, after the position sensorless switching, the load suddenly increases, so the inverter frequency command value ω ₁ may change suddenly, causing the motor to step out and stop.

Therefore, the periodic torque estimation means 30d and the control switching determination unit 31c shown in FIG. 18 are used. The frequency command value ω ^* (or inverter frequency command value ω ₁ ) is input to the periodic torque estimation means 30d, and the mechanical angle is calculated by dividing by the number of pole pairs. The q-axis current detection value I _qc is also input to the periodic torque estimation means 30d. Since the periodic torque estimating means 30d is a means suitable for short-time activation, it determines the magnitude of the change in the periodic torque within the two electrical angle periods. For example, the peak hold circuit 34 is used to determine _whether the peak value of I _qc in one cycle of the mechanical angle is in the mechanical angle of 0 to 180 degrees or in the range of 180 to 360 degrees.

For example, _when the peak value of I _qc is at a mechanical angle of 0 ° to 180 ° and the sensorless switching speed is reached during that period (in the case of the lower right side in FIG. 17 (example 2)), the control mode is switched. First, after one electrical angle cycle has elapsed, the mode is switched to the position sensorless mode. By doing so, since the mode is switched to the position sensorless mode during a period when the load torque fluctuation is small, the motor 6 can be started stably without starting failure.

For example, _when a change in I _qc can also be detected using the incomplete differentiator 34 shown in FIG. 14 or the like, after the sensorless switching rotation speed achievement timing overlaps with a period during which the load fluctuation is large, one electrical angle cycle is set. Without waiting, _when the differential value of I _qc becomes negative, the mode may be switched to the position sensorless mode. This is effective when it is desired to start up in a shorter time.

  In this way, by using the configuration example of the periodic torque estimating means and the control switching determination device of the present embodiment, the motor 6 is stably started without failing to start because the mode is switched to the position sensorless mode in a period when the load torque fluctuation is small. Can be made. Also, since the magnitude of load fluctuation in one cycle of electrical angle is compared with a plurality of electrical angles, it does not depend on the initial position of the motor, for example, after positioning, the rotor moves to another position due to some disturbance. The motor can be started stably even if

  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. Further, a part of the configuration 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 procedures, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. 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.

  Although the motor has been described as a permanent magnet motor, other electric motors (for example, induction machines, synchronous machines, switched reluctance motors, synchronous reluctance motors, etc.) may be used. At that time, the calculation method in the voltage command value generator varies depending on the electric motor, but other methods can be applied in the same manner, and the object of the present embodiment can be achieved.

  In the above embodiment, the speed control type configuration has been described as an example, but the present invention can of course be applied to a torque control type configuration. In this case, the calculation method of the q-axis current command value is different, and the control mode switching can be similarly applied, and the object of the present embodiment can be achieved.

  In the above embodiment, the switching timing of the control mode (positioning mode, synchronous operation mode, position sensorless mode) has been described, but it is not limited to switching of the control mode. For example, when the energization method is switched from 120-degree energization to 180-degree energization (of course, the opposite is also possible), by using the periodic torque estimation means and the control switching determination device described in this embodiment, current fluctuation, individuality fluctuation, etc. Switching shock can be minimized.

DESCRIPTION OF SYMBOLS 1 Motor control apparatus 2 Control part 3 Voltage command value preparation device 5 Power conversion circuit 6 Motor (electric motor)
DESCRIPTION OF SYMBOLS 10 Axis error calculator 12 Current detection means 13 PLL controller 14 Speed controller 16 Control changeover switch 20 DC voltage source 30 Periodic torque estimation means 31 Control change determination device 301 Refrigerator 500 Compression mechanism 503 Crankshaft

Claims (5)

In a motor control device comprising a synchronous operation mode that does not use information related to the rotation angle position and a position sensorless operation mode that is driven using information related to the rotation angle position, and switches the operation mode during driving,
It comprises periodic torque estimation means for estimating a periodic torque component that fluctuates in one mechanical angle cycle or an integral multiple of one mechanical angle cycle, and the operation mode is switched during a period in which the gradient of the periodic torque is near zero or negative. Motor control device. In a motor control device comprising a synchronous operation mode that does not use information related to the rotation angle position and a position sensorless operation mode that is driven using information related to the rotation angle position, and switches the operation mode during driving,
A periodic torque estimating means for estimating a periodic torque component that fluctuates in one mechanical angle cycle or an integral multiple of one mechanical angle cycle;
Cares angle one cycle collector to one period of the torque variation includes multiple, the more of one cycle of electrical angle, q-axis current detection value of the peak value is less one cycle of electrical angle period than the predetermined value, or A motor control device, wherein the operation mode is switched during a period of one electrical angle cycle in which a change in a q-axis current detection value is smaller than a predetermined value . The motor control device according to claim 1 or 2,
A motor control device comprising: a current detection unit, wherein the periodic torque estimation unit estimates a periodic torque component that fluctuates by one mechanical angle cycle or an integer multiple of one mechanical angle cycle, using information of the current detection unit. . In the motor control device according to any one of claims 1 to 3,
A motor control device comprising a current control means and estimating a periodic torque component from a change in output voltage.   4. The motor control device according to claim 3, wherein the periodic torque estimating means uses a differential value of the current detected by the current detecting means to generate a periodic torque component that fluctuates by one mechanical angle period or an integral multiple of one mechanical angle period. A motor control device characterized by estimating.