JP4522273B2 - Motor control device and motor drive system having the same - Google Patents

Description

  The present invention relates to a motor drive device that controls driving of a permanent magnet synchronous motor, and more particularly to a motor drive device that performs flux-weakening control. Moreover, it is related with the motor drive system which has those motor drive devices.

  In general, in a motor drive system that drives a permanent magnet synchronous motor (permanent magnet type synchronous motor; hereinafter simply referred to as “motor”), a negative d-axis is used to suppress an excessive increase in induced voltage during high-speed rotation. Magnetic flux weakening control by current is performed.

The induced voltage Vo generated by the rotation of the motor, the inductance of the motor and the armature interlinkage magnetic flux is generally expressed by the following equation (1). Considering that the induced voltage Vo is weakened and kept at the limit voltage V _om by magnetic flux control. The following formula (2) is obtained. Then, when the equation (2) is solved for the d-axis current, the following equation (3) is obtained.

Here, ω is the rotational angular velocity of the motor, L _d is the d-axis inductance, L _q is the q-axis inductance, Φ _a is the armature flux linkage by the permanent magnet, i _d is the d-axis current, and i _q is the q-axis current. is there.

As can be seen from the above equation (3), the d-axis current for flux-weakening control depends on the d-axis inductance L _d and the q-axis inductance L _q . Conventional motor drive system, the d-axis current i _d calculates the d-axis current command value for flux-weakening control to be followed, has been performed weakening controlling by the above formula (3).

  Various methods have been proposed for the magnetic flux weakening control method. For example, the drive control device for a permanent magnet synchronous motor described in Patent Document 1 below calculates the maximum voltage value that can be applied to the motor by sequentially detecting the voltage of the battery, and the maximum voltage value and the request required for the motor Based on the torque, the value of the flux weakening current is calculated.

  Patent Document 2 below discloses a synchronous motor control device that calculates a flux weakening current of a synchronous motor using a battery voltage and a rotational angular velocity.

  Further, in Patent Document 3 below, when field weakening control is performed, when the battery voltage value is large, the starting rotational speed of the field weakening control is high, and when the battery voltage value is small, the starting rotational speed of the field weakening control is low. A control apparatus for a synchronous motor is disclosed in which the starting rotational speed of the field weakening control is corrected in accordance with a detected value of the battery voltage.

Japanese Patent No. 3146791 Japanese Patent No. 3418826 Japanese Patent No. 3396440

In general, it is known that the q-axis inductance L _q changes depending on the q-axis current i _q . The value of the q-axis inductance L _q decreases as the q-axis current i _q increases due to the influence of magnetic saturation. Therefore, in the conventional motor drive system, when the value of L _q is treated as a constant value, the weakening magnetic flux using the above equation (3) due to a change in the q-axis current i _q (that is, a change in torque or a change in load). An error occurs in the calculation of the control d-axis current command value.

In addition, when the above-described expression (3) is used and the flux-weakening control is performed with the q-axis inductance L _q regarded as a constant value, the load range to be driven becomes small. Since the variation range of the q-axis current i _q increases as the load range increases, the change in the value of the q-axis inductance L _q corresponding to the change in the q-axis current i _q also increases and the motor can be controlled stably. It is because it becomes impossible.

Also, when creating a system for driving a motor, there are design values for the d-axis inductance L _d and the q-axis inductance L _q , but these design values do not necessarily match their actual true values. Since the d-axis current command value for flux-weakening control created according to Equation (3) depends on the d-axis inductance L _d and the q-axis inductance L _q , in order to perform flux-weakening control in a conventional motor drive system. Therefore, it was necessary to adjust the values of the d-axis inductance L _d and the q-axis inductance L _q for flux-weakening control so as to match the true values of the actual d-axis inductance L _d and the q-axis inductance L _q . That is, in order to realize the expected flux-weakening control, it is necessary to investigate what value each of the d-axis inductance L _d and the q-axis inductance L _q should be set. The adjustment of the two parameters is complicated and causes an increase in design man-hours and design costs.

  Further, even with the drive control device for the permanent magnet synchronous motor described in Patent Document 1, the calculation error of the d-axis current command value for the flux-weakening control caused by the fluctuation of the q-axis inductance value cannot be solved. The synchronous motor control device described in Patent Document 2 calculates a d-axis current command value for flux-weakening control while ignoring the d-axis component of the motor applied voltage. The d-axis component of the motor applied voltage depends on the q-axis inductance, and the above calculation error cannot be eliminated by simply ignoring it. Further, the technique described in Patent Document 3 is not a technique for solving the above-described problems such as calculation errors.

  Therefore, an object of the present invention is to provide a motor control device and a motor drive system that realize a flux-weakening control that is not affected by a change in q-axis inductance corresponding to a change in torque (q-axis current).

  In order to achieve the above object, a motor control device according to the present invention is a motor control device that performs flux-weakening control of a permanent magnet type synchronous motor. An axis parallel to a magnetic flux generated by a permanent magnet as a rotor is d-axis. When the d-axis component of the induced voltage generated by the rotation of the synchronous motor, the inductance of the synchronous motor and the armature linkage magnetic flux by the permanent magnet is regarded as a value calculated based on the d-axis voltage command value, A magnetic flux control unit that creates a d-axis current command value for flux-weakening control is provided, and the d-axis voltage of the synchronous motor should follow so that the d-axis current of the synchronous motor follows the d-axis current command value. A weakening magnetic flux control is performed by creating a shaft voltage command value.

  The d-axis component of the induced voltage depends on the q-axis inductance. However, as described above, the weak magnetic flux can be obtained by regarding the d-axis component of the induced voltage as a value calculated based on the d-axis voltage command value. The control d-axis current command value does not depend on the q-axis inductance value. As a result, the calculation error of the d-axis current command value for the flux-weakening control caused by the q-axis inductance change corresponding to the torque (q-axis current) change does not occur.

  In addition, since the d-axis current command value for flux-weakening control does not depend on the q-axis inductance, it is not necessary to consider the change in the q-axis inductance value corresponding to the torque (q-axis current) change. Therefore, even if the variation range of the q-axis current is increased to increase the load range, stable flux-weakening control is ensured. That is, according to said motor control apparatus, a large load range can be taken.

  Also, the adjustment of the two parameters d-axis inductance and q-axis inductance required in the conventional motor drive system can be simplified to the adjustment of only the d-axis inductance, and parameter adjustment becomes easy.

Specifically, for example, the d-axis current command value is i _d ^* , the armature interlinkage magnetic flux is Φ _a , the d-axis inductance is L _d , the predetermined limit voltage for the induced voltage is V _om , and the d-axis The voltage command value is v _d ^* , the rotational angular velocity of the synchronous motor is ω, the resistance of the armature winding of the synchronous motor is R _a , and the d-axis current obtained using the rotor position and the value of the current flowing through the synchronous motor is i _{When d} , the magnetic flux control unit regards the d-axis component of the induced voltage as (v _d ^* −R _a · _id ), and creates the d-axis current command value based on the following formula (A). That's fine.

Also, for example, the d-axis current command value is i _d ^* , the armature flux linkage is Φ _a , the d-axis inductance is L _d , the predetermined limit voltage for the induced voltage is V _om , and the d-axis voltage command value is Is v _d ^* and the rotational angular velocity of the synchronous motor is ω, the magnetic flux control unit regards the d-axis component of the induced voltage as v _d ^*, and the d-axis current command value based on the following equation (B) May be created.

  This simplifies the calculation process and speeds up the process of the motor control device.

Further, for example, when the latest d-axis current command value is created using the formula (A), the d-axis current command value created immediately before may be used as the value of i _d in the formula (A). .

  Further, for example, the magnetic flux control unit considers the d-axis component of the induced voltage as a value calculated based on the d-axis voltage command value, and determines the magnitude of the induced voltage and a predetermined value for the induced voltage. Based on the result of comparison with the magnitude of the limit voltage, it is preferable to determine whether or not to perform the flux-weakening control.

  Although the d-axis component of the induced voltage depends on the value of the q-axis inductance, the magnitude of the induced voltage obtained after considering the d-axis component of the induced voltage as a value calculated based on the d-axis voltage command value. The length does not depend on the value of the q-axis inductance. Therefore, by configuring as described above, the determination as to whether or not the flux-weakening control is performed is not affected by the change in the q-axis inductance corresponding to the change in the torque (q-axis current).

Further, for example, the d-axis voltage command value is v _d ^* , the q-axis voltage command value to be followed by the q-axis voltage of the synchronous motor is v _q ^* , the resistance of the armature winding of the synchronous motor is _Ra , and the rotor When the d-axis current and the q-axis current obtained using the position and the value of the current flowing through the synchronous motor are i _d and i _q , respectively, and the predetermined limit voltage for the induced voltage is V _om , the magnetic flux control unit When the following formula (C) is satisfied, it is preferable to perform the flux-weakening control.

For example, when determining whether or not to perform the flux-weakening control using the equation (C), the d-axis current command value to be followed by the d-axis current is set to the value of _{d d} in the equation (C). It may be used as a value.

Further, for example, when determining whether or not to perform the flux-weakening control using the formula (C), the q-axis current command value that the q-axis current should follow is the value of i _q in the formula (C). It may be used as

Further, for example, the d-axis voltage command value is v _d ^* , the resistance of the armature winding of the synchronous motor is R _a , and the d-axis current obtained using the rotor position and the value of the current flowing through the synchronous motor is i _d. When the armature interlinkage flux is Φ _a , the d-axis inductance is L _d , the rotational angular velocity of the synchronous motor is ω, and the predetermined limit voltage for the induced voltage is V _om , the magnetic flux control unit has the following formula ( When D) is established, the flux-weakening control may be performed.

For example, when determining whether or not to perform the flux-weakening control using the equation (D), the d-axis current command value to be followed by the d-axis current is set to the value of _{d d} in the equation (D). It may be used as a value.

  In addition, for example, the motor control device is configured to control the weakening magnetic flux of the synchronous motor by controlling an inverter that drives the synchronous motor, and the magnetic flux control unit is configured to apply d of the voltage applied to the synchronous motor. Based on the comparison result between the magnitude of the voltage applied to the synchronous motor and the predetermined limit voltage with respect to the maximum voltage that can be output from the inverter based on the fact that the axis component is regarded as the d-axis voltage command value, the flux-weakening control It is better to determine whether or not to perform.

  Although the d-axis component of the voltage applied to the synchronous motor depends on the value of the q-axis inductance, the applied voltage to the synchronous motor that is obtained by regarding the d-axis component of the voltage applied to the synchronous motor as the d-axis voltage command value. Does not depend on the value of the q-axis inductance. Therefore, by configuring as described above, the determination as to whether or not the flux-weakening control is performed is not affected by the change in the q-axis inductance corresponding to the change in the torque (q-axis current).

Further, for example, the motor control device is configured to control the magnetic flux weakening of the synchronous motor by controlling an inverter that drives the synchronous motor, and the d-axis voltage command value is set to v _d ^* When the q-axis voltage command value to be followed by the q-axis voltage is v _q ^* , and the predetermined limit voltage with respect to the maximum voltage that can be output from the inverter is V _am , the magnetic flux control unit satisfies the following formula (E) It is better to perform magnetic flux control.

Further, for example, the motor control device is configured to control the magnetic flux weakening of the synchronous motor by controlling an inverter that drives the synchronous motor, and the d-axis voltage command value is set to v _d ^* The resistance of the armature winding is R _a , the d-axis current and the q-axis current obtained using the values of the rotor position and the current flowing through the synchronous motor are i _d and i _q , respectively, and the armature linkage flux is Φ _a When the d-axis inductance is L _d , the rotational angular velocity of the synchronous motor is ω, and the predetermined limit voltage with respect to the maximum voltage that can be output from the inverter is V _am , the magnetic flux control unit performs the following equation (F): Magnetic flux weakening control may be performed.

For example, when determining whether or not to perform the flux-weakening control using the formula (F), the d-axis current command value to be followed by the d-axis current is set to the value of _{d d} in the formula (F). It may be used as a value.

Further, for example, when determining whether or not to perform the flux-weakening control using the equation (F), the q-axis current command value that the q-axis current should follow is the value of i _q in the equation (F). It may be used as

  Since none of the expressions (C), (D), (E), and (F) includes the q-axis inductance, it is determined whether or not to perform the flux-weakening control by the magnetic flux controller (execution / The determination of non-execution) is not affected by a change in q-axis inductance corresponding to a change in torque (q-axis current).

  Further, for example, the magnetic flux control unit may calculate the limit voltage with respect to the induced voltage based on a power supply voltage for driving the synchronous motor. For example, the magnetic flux control unit may calculate the limit voltage with respect to the maximum voltage based on a power supply voltage for driving the synchronous motor.

  If the value of the limit voltage for the induced voltage is calculated based on the power supply voltage for driving the synchronous motor, the limit voltage for the induced voltage according to the power supply voltage can be optimized, and the weakening flux control can be optimized. It is done. In addition, if the value of the limit voltage for the induced voltage or the limit voltage for the maximum voltage calculated based on the power supply voltage for driving the synchronous motor is used to determine whether to perform the flux-weakening control, the power supply voltage is The execution / non-execution of the weak magnetic flux control is determined accordingly.

  In order to achieve the above object, the motor drive system according to the present invention includes the synchronous motor, an inverter that drives the synchronous motor, and the motor control that performs flux weakening control of the synchronous motor by controlling the inverter. And a device.

  As described above, according to the motor control device and the motor drive system of the present invention, the flux-weakening control that is not affected by the change in the q-axis inductance corresponding to the change in the torque (q-axis current) is possible.

  Hereinafter, embodiments of a motor control device and a motor drive system according to the present invention will be described. FIG. 1 is a block configuration diagram of a motor control device and a motor drive system having the motor control device according to an embodiment of the present invention.

Reference numeral 1 denotes a three-phase permanent magnet synchronous motor 1 (hereinafter simply referred to as “motor 1”) in which a permanent magnet is provided on a rotor (not shown) and an armature winding is provided on a stator (not shown). is there. The motor (synchronous motor) 1 obtains a field magnetic flux by the permanent magnet. A PWM (Pulse Width Modulation) inverter 2 supplies a three-phase AC voltage composed of a U phase, a V phase, and a W phase to the motor 1 according to the rotor position of the motor 1. The voltage supplied to the motor 1 and the motor applied voltage (armature voltage) V _a, the current supplied to the motor 1 the motor current (armature current) and I _a. Reference numeral 3 denotes a motor control device, which provides the PWM inverter 2 with a signal for rotating the motor 1 at a desired rotational speed and a signal for performing flux-weakening control.

  The motor drive system of FIG. 1 includes a motor 1, a PWM inverter 2, and a motor control device 3, and is configured by connecting a power supply 4 that supplies a power supply voltage for driving the motor 1 to the PWM inverter 2. The power supply 4 may be anything as long as it supplies a DC power supply voltage to the PWM inverter 2. For example, a battery (for example, a secondary battery such as a nickel metal hydride battery) may be used, or an AC / DC converter that converts a commercial AC voltage into a direct current may be used.

The output voltage of the power supply 4 (equal to the power supply voltage) is converted into a three-phase AC voltage by the PWM inverter 2 provided between the power supply 4 and the motor 1 and supplied to the motor 1. The output voltage of the power source 4 is sequentially detected by the voltage detector 5, and the detected value is given to the motor control device 3 as the power source voltage V _B for driving the motor 1. Note that the power supply 4 and the voltage detector 5 may be considered to be included in the motor drive system according to the present embodiment.

  FIG. 2 is an analysis model diagram of the three-phase permanent magnet synchronous motor 1. FIG. 2 shows U-phase, V-phase, and W-phase armature winding fixed axes. 1 a is a permanent magnet corresponding to the rotor of the motor 1. In the rotating coordinate system that rotates at the same speed as the magnetic flux generated by the permanent magnet, the magnetic flux direction of the permanent magnet is taken as the d-axis, and the q-axis is taken at a phase advanced by 90 degrees from the d-axis by an electrical angle (the q-axis is not shown).

  A rotational coordinate axis composed of a d-axis and a q-axis is rotating, and its rotational angular velocity is ω. This rotational angular velocity ω is equal to the rotational angular velocity of the motor 1. In addition, in a rotating coordinate axis rotating at a certain moment, the phase of the d-axis is represented by θ (rotor position θ) with respect to the U-phase armature winding fixed axis.

In the following description, the d-axis component and the q-axis component of the motor applied voltage V _a are represented by the d-axis voltage v _d and the q-axis voltage v _q , respectively, and the d-axis component and the q-axis component of the motor current I _a are respectively expressed as It is expressed by d-axis current i _d and q-axis current i _q .

In the following description, R _a is a motor resistance (resistance value of the armature winding of the motor 1), and L _d and L _q are d-axis inductances (inductance of the armature winding of the motor 1). d-axis component), q-axis inductance (q-axis component of the inductance of the armature winding of the motor 1), and Φ _a is an armature interlinkage magnetic flux by the permanent magnet 1a. Note that L _d , L _q , R _a and Φ _a are values set in advance at the time of designing the motor drive system.

(Overall description)
FIG. 3 shows a detailed block diagram of the motor drive system 3 of FIG. The motor drive system 3 includes a current detector 11, a three-phase two-phase coordinate converter 12, a subtractor 13, a subtractor 14, a current control unit 15, a magnetic flux control unit 16, a two-phase three-phase coordinate converter 18, a resolver 20, A position detector 21 and a velocity detector 22 are included.

  The position detector 21 detects the rotor position θ based on the output from the resolver 20 having a function as a position sensor. The speed detector 22 detects the rotational angular speed ω based on the output from the resolver 20 having a function as a rotational speed sensor.

Current detector 11, for example, a Hall element, detects the U-phase current i _u and the V-phase current i _v of the motor current I _a supplied from the PWM inverter 2 to the motor 1. 3-phase 2-phase coordinate converter 12 receives detection results of the U-phase current i _u and the V-phase current i _v from the current detector 11, with the rotor position θ given from their position detector 21, It converts into d-axis current i _d and q-axis current i _q .

The subtractor 14 subtracts the q-axis current i _q given from the three-phase two-phase coordinate converter 12 from the q-axis current command value i _q ^* to calculate a current error (i _q ^* −i _q ). The q-axis current command value i _q ^* corresponds to a current value that the q-axis current i _q should follow. The q-axis current command value i _q ^* is given from, for example, a CPU (Central Processing Unit) not shown. Further, for example, the speed control unit (not shown) performs proportional-integral control so that the rotational angular speed ω output from the speed detector 22 follows a motor speed command value representing a desired rotational speed given from a CPU (not shown). The q-axis current command value i _q ^* is calculated from the above.

The subtracter 13 subtracts the d-axis current i _d supplied from three-phase to two-phase coordinate converter 12 from the d-axis current command value i _d ^*, and calculates the current error (i _d ^* -i _d). The d-axis current command value i _d ^* corresponds to a current value that the d-axis current i _d should follow. The d-axis current command value i _d ^* is given from the magnetic flux controller 16, and the calculation method will be described later.

The current control unit 15 is based on the current errors from the subtracters 13 and 14, the d-axis current _id and the q-axis current i _q from the three-phase two-phase coordinate converter 12, and the rotational angular velocity ω from the speed detector 22. Thus, the d-axis current i _d follows the d-axis current command value i _d ^* (so that it becomes equal), and the q-axis current i _q follows the q-axis current command value i _q ^* (equally). The voltage command values (d-axis voltage command value v _d ^* and q-axis voltage command value v _q ^* ) on the rotating coordinate system representing the voltage to be applied to the motor 1 using proportional integral control or the like. Create and output. The current control unit 15 creates the voltage command value based only on the current errors from the subtracters 13 and 14 without being based on the d-axis current i _d and the q-axis current i _{q and the} rotational angular velocity ω. Also good.

The two-phase / three-phase coordinate converter 18 performs reverse conversion of the d-axis voltage command value v _d ^* and the q-axis voltage command value v _q ^* by using the rotor position θ given from the position detector 21, and the U-phase voltage A three-phase voltage command value composed of the command value v _u ^* , the V-phase voltage command value v _v ^*, and the W-phase voltage command value v _w ^* is created and output to the PWM inverter 2. The PWM inverter 2 creates a pulse-width modulated signal based on a three-phase voltage command value representing a voltage to be applied to the motor 1 and drives the motor 1.

(Calculation method of i _d ^* )
Next, a method for calculating the d-axis current command value i _d ^* for the flux weakening control by the magnetic flux controller 16 will be described. The induced voltage Vo generated by the rotation and inductance of the motor 1 (inductance of the armature winding of the motor 1) and the armature interlinkage magnetic flux Φ _a is expressed by the above-described equation (1). When the control voltage is kept at the limit voltage V _om , the value of the d-axis current i _d is generally as shown on the right side of the above equation (3). In Expression (3), the limit voltage V _om indicates an upper limit voltage to be limited to the induced voltage Vo, and is calculated from the maximum voltage (suppliable voltage) that can be output by the PWM inverter 2. The law will be described later.

Formula (3) is transformed into the following formula (4). Further, if the d-axis component of the induced voltage Vo is v _do , then v _do = −ωL _q i _q, so equation (4) is further transformed into equation (5).

Here, the d-axis component v _do of the induced voltage Vo calculated by −ωL _q i _q is replaced with the d-axis induced voltage command value v _do ^* calculated from the d-axis voltage command value v _d ^* , and the formula ( 6) is obtained.

Here, the d-axis induced voltage command value v _do ^* is a value calculated by v _do ^* = (v _d ^* −R _a · _id ). In the steady state, the d-axis component v _do of the induced voltage Vo corresponds to _a value obtained by subtracting the voltage drop due to the motor resistance Ra from the d-axis voltage v _d , that is, (v _d −R _a · _id ). Since the shaft voltage v _d follows (becomes equal to) the d-axis voltage command value v _d ^* , the d-axis component v _do of the induced voltage Vo is d-axis induced voltage command value v _do ^* = (v _d ^* −R _a. i _d ).

Therefore, if the magnetic flux control unit 16 calculates the d-axis current command value i _d ^* for flux-weakening control according to the following formula (7), the d-axis current i _d follows the d-axis current command value i _d ^* . Therefore, the induced voltage Vo is kept at the limit voltage V _om . As described above, the magnetic flux controller 16 regards the d-axis component v _do of the induced voltage Vo as (v _d ^* −R _a · _id ), and creates the d-axis current command value i _d ^* for controlling the weak magnetic flux. To do.

As described above, the d-axis component v _do of the induced voltage Vo is accurately −ωL _q i _q , but the d-axis current command value for the flux-weakening control according to the equations (3) and (4). If i _d ^* is calculated, its value depends on the q-axis inductance L _q and the q-axis current i _q . If it does so, an error will arise in calculation of d axis current command value for magnetic flux control like the conventional composition.

However, by regarding the d-axis component v _do of the induced voltage Vo as a value calculated on the basis of the d-axis voltage command value v _d ^* , the d-axis current command value i _d ^* for flux-weakening control becomes the q-axis inductance L _It does not depend on the value of _q . Thereby, the problem of the calculation error which the conventional structure has is solved.

Also, weakening since the flux control of d-axis current command value i _d ^* does not depend on the q-axis inductance L _q, necessary to consider the change in the value of q-axis current i q-axis corresponding to the change of _q inductance L _q There is no. Therefore, even if the fluctuation range of the q-axis current i _q is increased so as to increase the load range, stable flux-weakening control is ensured. That is, according to the present embodiment, the load range can be increased.

Also, the adjustment of the two parameters of the d-axis inductance L _d and the q-axis inductance L _q required in the conventional motor drive system can be simplified to the adjustment of only the d-axis inductance L _d , and the parameter adjustment becomes easy. .

Note that the rotational angular velocity ω, the d-axis voltage command value v _d ^* , and the d-axis current i _d required for calculating the d-axis current command value i _d ^* for flux-weakening control are the speed detector 22 and the current, respectively. It is given from the control unit 15 and the three-phase / two-phase coordinate converter 12.

In the flux weakening control, the magnetic flux controller 16 updates the d-axis current command value i _d ^* one after another at a predetermined interval. Then, the current control unit 15 sets the d-axis voltage command value v _d ^* and the q-axis voltage command value v _q ^* so as to follow the d-axis current command value i _d ^{* in} which the d-axis current i _d is updated one after another. Update one after another.

Considering that the d-axis current command value i _d ^* is updated one after another (n-2), (n-1), nth, etc. (where n is a natural number) ), the value of d-axis current i _d to be used in the n-th d-axis current command value i _d ^* is calculated in the equation (7) is the (n-1) th to the obtained d-axis current command value i It can be considered to be approximately equal to _d ^* .

Therefore, the latest (the n-th) when d-axis current command value i _d ^* for calculation, immediately before (the (n-1) th to) the calculated d-axis current command value i _d ^* and d-axis current i You can consider it as _d . That is, the latest d-axis current command value i _d ^* may be calculated using the following equation (8) instead of the above equation (7). In the following formula (8), i _d− ^* represents the d-axis current command value obtained immediately before the latest d-axis current command value i _d ^* to be obtained by the formula (8).

Moreover, ignoring the voltage drop in the motor resistance R _a, the following equation (9) may be calculated d-axis current command value i _d ^* for flux-weakening control using instead of the equation (7). Method using the following formula (9), such as when the voltage drop in the motor resistance R _a is sufficiently smaller than the d-axis voltage command value v _d ^*, is a particularly effective method. By using the following formula (9), the calculation process is simplified, and the processing speed of the motor control device 3 is increased.

(Calculation method of limit voltage)
Next, a method for calculating the limit voltage V _om with respect to the induced voltage Vo will be described. The limit voltage V _om indicates an upper limit voltage to be limited with respect to the induced voltage Vo, and is calculated from the maximum voltage (suppliable voltage) that the PWM inverter 2 can output. For example, the magnetic flux controller 16 calculates the limit voltage V _om according to the following formula (10).

Here, V _am is a predetermined limit voltage with respect to the maximum voltage (voltage that can be supplied) that can be output by the PWM inverter 2, and I _am is the maximum current that can be output by the PWM inverter 2. The limit voltage _Vam may be set to be equal to the maximum voltage that the PWM inverter 2 can output, or may be set to a voltage less than the maximum voltage with a margin from the maximum voltage. The value of V _am is based on the detection result of the output voltage of the power source 4 by the voltage detector 5 (see FIG. 1), that is, the value of the power source voltage V _B for driving the motor 1, for example, by the following equation (11) Calculated. If the value of V _B sequentially detected by the voltage detector 5 changes, the value of V _am is also updated sequentially.

However, V _am calculated by the above formula (11) is that when the effective utilization rate (voltage utilization rate) of the output voltage of the power supply 4 is 100%, and the effective utilization rate (voltage) of the output voltage of the power supply 4 is In the case where the (utilization rate) is less than 100%, _Vam is set smaller than the value calculated on the right side of the above equation (11) in consideration of the decrease in the effective utilization rate.

The value of I _am is set in consideration of the restrictions on the characteristics of the PWM inverter 2, the current that can be output from the power source 4, the restriction on the heat generation of the motor 1, and the like. Note that the value of I _am may be a fixed value, or changes according to the temperature of the motor 1 (for example, the temperature detected by a thermistor not shown), the value of the motor current detected by the current detector 11, and the like. You may make it do.

  For example, when the maximum voltage that can be output from the PWM inverter 2 is greater than a certain reference voltage, the PWM inverter 2 and the power supply 4 are not stressed even if a larger induced voltage is generated. It is desirable to change to a larger value.

If, despite larger than the reference voltage with a maximum voltage, necessary to adjust the value of the limit voltage V _om, because the d-axis current i _d which is not involved in torque generation occurring waste, reduction of efficiency Invite. On the contrary, if the value of the limit voltage V _{om is} not changed even though the maximum voltage is smaller than a certain reference voltage, the reverse voltage caused by the induced voltage is added to the PWM inverter 2 and the power source 4 and is added to them. It can be stressful.

However, as can be seen from the above formulas (10) and (11), the magnetic flux control unit 16 according to the present embodiment corresponds to the maximum voltage based on the output voltage of the power source 4 corresponding to the power source voltage for driving the motor 1. Since the value of the limit voltage V _am is calculated, and the value of the limit voltage V _om is also calculated based on the output voltage, the limit voltage V _om is optimized according to the output voltage of the power supply 4. This makes it possible to optimize the flux-weakening control. In particular, when the power source 4 is a battery, the output voltage of the power source 4 fluctuates relatively greatly. Therefore, it is significant to calculate the limit voltage V _om based on the output voltage of the power source 4. Further, using the value of the limit voltage V _om corresponding to the output voltage of the power source 4 or the value of the limit voltage V _am corresponding to the output voltage of the power source 4, the following expressions (14) to (20) are established / not established. If it is determined, execution / non-execution of the magnetic flux weakening control corresponding to the output voltage of the power supply 4 is determined.

(Execution of weak flux control)
Next, a description will be given of what conditions are satisfied by the magnetic flux control unit 16 to enable the flux-weakening control.

Generally, when the magnitude of the induced voltage Vo (the magnitude of the vector of the induced voltage Vo) exceeds the magnitude of the limit voltage V _om with respect to the induced voltage, that is, when the following formula (12) is satisfied, the flux weakening Control is enabled (weakening magnetic flux control is performed).

Here, v _qo is the q-axis component of the induced voltage Vo, and the value and the d-axis component v _do of the induced voltage Vo use the rotational angular velocity ω and the d-axis current i _d q-axis current i _q which are detected values. And represented by the following formula (13a) and formula (13b). In a steady state, the d-axis voltage v _d and the q-axis voltage v _q are expressed by the following formulas (13c) and (13d).

As described above, the q-axis inductance L _q changes depending on the q-axis current i _q involved in the torque of the motor 1. Therefore, according to the equation (12), it is determined whether or not the weakening magnetic flux control is enabled. Is affected by the change in the q-axis inductance L _q according to the change in the torque (q-axis current i _q ).

Therefore, the magnetic flux controller 16 determines whether or not to perform the weak magnetic flux control using any of the following first to fourth determination methods that do not include the q-axis inductance L _q in the determination formula (execution of the weak magnetic flux control). / Not-executed).

In the first determination method, the d-axis component v _do of the induced voltage Vo and the q-axis component v _qo of the induced voltage Vo in the above equation (12) are used as the d-axis induced voltage command value v _do ^* and the q-axis induced voltage, respectively. Equation (14) replaced with the command value v _qo ^* is used. d-axis induced voltage command value v _do ^* is, v _do ^* = a value calculated by ^{_{(v d * -R a · i}} d), q axis induced voltage command value v _qo ^* is, v _qo ^* = This is a value calculated by (v _q ^* −R _a · i _q ). Therefore, equation (14) is equivalent to equation (15). The magnetic flux control unit 16 enables the weakening magnetic flux control (performs the weakening magnetic flux control) when the following formula (15) is established. Note that the value of the q-axis current i _q necessary for determining whether the equation (15) is satisfied or not is supplied from the three-phase / two-phase coordinate converter 12 to the magnetic flux controller 16 although not shown in FIG.

In the steady state, the d-axis component v _do of the induced voltage Vo corresponds to _a value obtained by subtracting the voltage drop due to the motor resistance Ra from the d-axis voltage v _d , that is, (v _d −R _a · _id ). Since the shaft voltage v _d follows (becomes equal to) the d-axis voltage command value v _d ^* , the d-axis component v _do of the induced voltage Vo is d-axis induced voltage command value v _do ^* = (v _d ^* −R _a. i _d ). Similarly, in the steady state, the q-axis component v _qo of the induced voltage Vo _corresponds to the q-axis voltage v _q minus the voltage drop due to the motor resistance R _a , that is, (v _q −R _a · i _q ). However, since the q-axis voltage v _q follows (becomes equal) the q-axis voltage command value v _q ^* , the q-axis component v _qo of the induced voltage Vo is the q-axis induced voltage command value v _qo ^* = (v _q ^* − R _a · i _q ). Therefore, even if the above equation (15) is used, the execution / non-execution of the weak magnetic flux control can be determined without any problem.

In the second determination method, considering that the q-axis component v _qo of the induced voltage Vo does not depend on the q-axis inductance L _q , only the d-axis component v _do of the induced voltage Vo in Expression (12) is used as the d-axis induced. Expression (16) replaced with the voltage command value v _do ^* is used. Expression (17) is an expression equivalent to Expression (16) (see Expression (13b)). The magnetic flux control unit 16 enables the weakening magnetic flux control (performs the weakening magnetic flux control) when the following formula (17) is established.

The d-axis component v _do of the induced voltage Vo depends on the q-axis inductance L _q as can be seen from the equation (13a). In view of this, both the expression (14) in the first determination method and the expression (16) in the second determination method are based on the d-axis component v _do of the induced voltage Vo based on the d-axis voltage command value v _do ^* . The magnitude of the induced voltage Vo and the magnitude of the limit voltage V _om which are obtained after being regarded as the values calculated in the above are compared.

In the third determination method, the following equation without consideration of the components of the R _a · i _d and R _a · i _q (18), weakened used in executing the judgment of the flux control. The magnetic flux controller 16 enables the weakening magnetic flux control (performs the weakening magnetic flux control) when the following formula (18) is established.

In the fourth determination method, Expression (19) in which the q-axis voltage command value v _q ^* in Expression (18) is replaced with the q-axis voltage v _q is used for execution determination of the flux-weakening control. As can be seen from the equation (13d), the q-axis voltage v _q does not depend on the q-axis inductance L _q . By substituting equation (13d) into equation (19), equation (20) is obtained. The magnetic flux control unit 16 enables the weakening magnetic flux control (performs the weakening magnetic flux control) when the following equation (20) is established. Note that the value of the q-axis current i _q necessary for determining whether the equation (20) is satisfied or not is supplied from the three-phase two-phase coordinate converter 12 to the magnetic flux control unit 16 although not shown in FIG.

The d-axis component (d-axis voltage v _d ) of the motor applied voltage V _a depends on the q-axis inductance L _q as can be seen from the equation (13c). In view of this, both the expression (18) in the third determination technique and the expression (19) in the fourth determination technique both _express the d-axis component (d-axis voltage v _d ) of the motor applied voltage V _a as the d-axis voltage. The magnitude of the voltage applied to the motor 1 that is obtained after considering the command value v _d ^* is compared with the magnitude of the limit voltage V _am with respect to the maximum voltage that can be output by the PWM inverter 2.

Since none of the equations (15), (17), (18), and (20) used in the first to fourth determination methods described above includes the q-axis inductance L _q , the magnetic flux control unit The determination as to whether to enable the flux-weakening control by 16 (execution / non-execution determination) is not affected by the change in the q-axis inductance L _q according to the change in the torque (q-axis current i _q ).

Further, when the execution / non-execution of the flux-weakening control is determined using the first, second, and fourth determination methods, the d-axis current command value i _d ^* is expressed by Expression (15), Expression (17), and Expression (20) may be used as the value of d-axis current i _d in each of. Further, when the execution / non-execution of the flux-weakening control is determined using the first and fourth determination methods, the q-axis current command value i _q ^{* is changed} to the q-axis in each of the equations (15) and (20). It may be used as the value of the current i _q . Further, when the execution / non-execution of the flux-weakening control is determined using the first and fourth determination methods, the d-axis current command value i _d ^{* is set} to the d-axis in each of the equations (15) and (20). The q-axis current command value i _q ^* may be used as the value of the current i _{d as} the value of the q-axis current i _q in each of the equations (15) and (20). Further, in each of the equations (14) to (20), the magnetic flux weakening control may be made effective only when the value on the left side is larger than the value on the right side. That is, “≧” in each of the equations (14) to (20) may be replaced with “>”.

Note that the d-axis voltage command value v _d ^* and the q-axis voltage command value v _q ^* necessary for determining whether to enable the flux-weakening control are obtained from the current control unit 15 by the d-axis current _id and q-axis current. i _q is supplied to the magnetic flux controller 16 from the three-phase / two-phase coordinate converter 12, and the rotational angular velocity ω is supplied from the velocity detector 22. However, FIG. 3 showing a block diagram for creating the d-axis current command value i _d ^* for flux-weakening control (see the above formula (7), etc.) shows the q-axis current to prevent the drawing from becoming complicated. how i _q is given to the flux controller 16 is not shown.

Further, when the above formulas (14) to (20) are not established and the flux-weakening control is not performed, the d-axis current command value i _d ^* is set to, for example, zero.

(Debt time is considered)
The PWM inverter 2 alternately turns on and off the switching elements of the upper arm and the lower arm based on the three-phase voltage command value given from the two-phase / three-phase coordinate converter 18. In order to prevent the elements from being short-circuited, when switching on and off the switching elements of the upper arm and the lower arm, both switching elements are turned off for a predetermined dead time.

  Therefore, if no correction is made to the voltage command value corresponding to the dead time, the actual voltage applied to each phase of the motor 1 is the three-phase voltage command value given from the two-phase three-phase coordinate converter 18. Smaller than.

Therefore, the current control unit 15 may be configured to create the d-axis voltage command value v _d ^* and the q-axis voltage command value v _q ^* in consideration of the dead time. That is, the d-axis voltage command value v _d ^* and the q-axis voltage command value v _q ^* are created so as to cancel the actual voltage drop applied to each phase of the motor 1 that may be caused by the dead time. May be. Of course, in this case, the above-described calculation of the d-axis current command value i _d ^{* for} the flux-weakening control and the determination as to whether or not to enable the flux-weakening control are determined based on the d-axis voltage created in consideration of the dead time. This is performed using the command value v _d ^* and the q-axis voltage command value v _q ^* . As a result, it is possible to control the magnetic flux weakening without the influence of the dead time.

<< Other, deformation, etc. >>
In the above-described embodiment, an example in which the rotor position θ and the rotational angular velocity ω are obtained based on the output from the resolver 20 is shown, but the motor current is not provided without the resolver 20, the position detector 21, and the velocity detector 22. So-called speed sensorless control in which the rotor position θ and the rotational angular velocity ω are estimated based on I _a or the like may be employed.

The current detector 11 has been illustrated and detects the motor current I _a by using a Hall element or the like, may be adopted a so-called current sensorless control. For example, a current detector 11, to reproduce the motor current from the instantaneous current of the power supply side of the DC current, whereby it may be configured so as to detect the motor current I _a.

  According to the motor control device and the motor drive system of the present invention, it is possible to control the magnetic flux weakening without being affected by the q-axis inductance change corresponding to the torque (q-axis current) change.

1 is a block configuration diagram of a motor control device according to an embodiment of the present invention and a motor drive system having the motor control device. It is an analysis model figure of the permanent magnet synchronous motor of FIG. FIG. 2 is a detailed block configuration diagram of the motor drive system of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 1a Permanent magnet 2 PWM inverter 3 Motor controller 4 Power supply 5 Voltage detector 11 Current detector 12 Three-phase two-phase coordinate converter 13, 14 Subtractor 15 Current control unit 16 Magnetic flux control unit 18 Two-phase three-phase coordinate conversion 20 Resolver 21 Position detector 22 Speed detector ω Rotational angular velocity ω
θ Rotor position θ
v _u ^* U-phase voltage command value v _u ^*
v _v ^* V-phase voltage command value v _v ^*
v _w ^* W-phase voltage command value v _w ^*
v _d ^* d-axis voltage command value v _d ^*
v _q ^* q-axis voltage command value v _q ^*
i _d d-axis current i _d
i _q q-axis current i _q
i _d ^* d-axis current command value i _d ^*
i _q ^* q-axis current command value i _q ^*
V _B supply voltage

Claims (18)

In the motor control device for performing the flux weakening control of the permanent magnet type synchronous motor,
When the axis parallel to the magnetic flux created by the permanent magnet as the rotor is d-axis,
For weakening magnetic flux control, the d-axis component of the induced voltage generated by the rotation of the synchronous motor, the inductance of the synchronous motor, and the armature linkage flux by the permanent magnet is regarded as a value calculated based on the d-axis voltage command value. A magnetic flux control unit for creating a d-axis current command value of
A magnetic flux control is performed by creating the d-axis voltage command value that the d-axis voltage of the synchronous motor should follow so that the d-axis current of the synchronous motor follows the d-axis current command value. Control device. The d-axis current command value is i _d ^* , the armature flux linkage is Φ _a , the d-axis inductance is L _d , the predetermined limit voltage for the induced voltage is V _om , and the d-axis voltage command value is v _d ^*. When the rotational angular velocity of the synchronous motor is ω, the resistance of the armature winding of the synchronous motor is R _a , and the d-axis current obtained by using the rotor position and the value of the current flowing through the synchronous motor is i _d ,
The magnetic flux control unit regards the d-axis component of the induced voltage as (v _d ^* −R _a · _id ), and creates the d-axis current command value based on the following formula (A). The motor control device according to claim 1.

The d-axis current command value is i _d ^* , the armature flux linkage is Φ _a , the d-axis inductance is L _d , the predetermined limit voltage for the induced voltage is V _om , and the d-axis voltage command value is v _d ^*. When the rotational angular speed of the synchronous motor is ω,
2. The motor control according to claim 1, wherein the magnetic flux control unit regards the d-axis component of the induced voltage as v _d ^* and creates the d-axis current command value based on the following formula (B). apparatus.

The latest d-axis current command value is created using the equation (A), and the d-axis current command value created immediately before is used as the value of i _d in the equation (A). 2. The motor control device according to 2. The magnetic flux control unit considers the d-axis component of the induced voltage as a value calculated based on the d-axis voltage command value, and the magnitude of the induced voltage and a predetermined limit voltage with respect to the induced voltage. 4. The motor control device according to claim 1, wherein a determination is made as to whether or not the flux-weakening control is performed based on a comparison result with the motor control device. 5. The d-axis voltage command value is v _d ^* , the q-axis voltage command value to be followed by the q-axis voltage of the synchronous motor is v _q ^* , the resistance of the armature winding of the synchronous motor is _Ra , the rotor position and the synchronous motor When the d-axis current and the q-axis current obtained using the values of the currents flowing through i are i _d and i _q , respectively, and the predetermined limiting voltage for the induced voltage is V _om ,
The motor control device according to any one of claims 1 to 3, wherein the magnetic flux control unit performs magnetic flux weakening control when the following formula (C) is satisfied.

When determining whether or not to perform flux-weakening control using the equation (C), the d-axis current command value that the d-axis current should follow is used as the value of _id in the equation (C). The motor control device according to claim 6. When determining whether or not to perform flux-weakening control using the equation (C), the q-axis current command value that the q-axis current should follow is used as the value of i _q in the equation (C). The motor control device according to claim 6, wherein the motor control device is characterized by the following. The d-axis voltage command value is v _d ^* , the resistance of the armature winding of the synchronous motor is R _a , the d-axis current obtained using the rotor position and the value of the current flowing through the synchronous motor is i _d , and the armature When the flux linkage is Φ _a , the d-axis inductance is L _d , the rotational angular velocity of the synchronous motor is ω, and the predetermined limiting voltage for the induced voltage is V _om ,
The motor control device according to any one of claims 1 to 3, wherein the magnetic flux control unit performs magnetic flux weakening control when the following formula (D) is satisfied.

When determining whether or not to perform flux-weakening control using the equation (D), the d-axis current command value that the d-axis current should follow is used as the value of _id in the equation (D). The motor control device according to claim 9. The motor control device is configured to control the magnetic flux weakening of the synchronous motor by controlling an inverter that drives the synchronous motor,
The magnetic flux control unit determines a predetermined limit on the magnitude of the voltage applied to the synchronous motor and the maximum voltage that can be output from the inverter based on the d-axis component of the voltage applied to the synchronous motor as the d-axis voltage command value. The motor control device according to any one of claims 1 to 3, wherein a determination is made as to whether or not the flux-weakening control is performed based on a comparison result with the magnitude of the voltage. The motor control device is configured to control the magnetic flux weakening of the synchronous motor by controlling an inverter that drives the synchronous motor,
When the d-axis voltage command value is v _d ^* , the q-axis voltage command value to be followed by the q-axis voltage of the synchronous motor is v _q ^* , and a predetermined limit voltage with respect to the maximum voltage that can be output from the inverter is V _am ,
The motor control device according to any one of claims 1 to 3, wherein the magnetic flux control unit performs magnetic flux weakening control when the following formula (E) is satisfied.

The motor control device is configured to control the magnetic flux weakening of the synchronous motor by controlling an inverter that drives the synchronous motor,
The d-axis voltage command value is v _d ^* , the resistance of the armature winding of the synchronous motor is R _a , and the d-axis current and q-axis current obtained by using the rotor position and the value of the current flowing through the synchronous motor are i, respectively. _d and i _q , where the armature flux linkage is Φ _a , the d-axis inductance is L _d , the rotational angular velocity of the synchronous motor is ω, and the predetermined limit voltage with respect to the maximum voltage that can be output from the inverter is V _am ,
The motor control device according to any one of claims 1 to 3, wherein the magnetic flux control unit performs magnetic flux weakening control when the following formula (F) is satisfied.

When determining whether to perform flux-weakening control using the equation (F), the d-axis current command value that the d-axis current should follow is used as the value of i _d in the equation (F). The motor control device according to claim 13. When determining whether to perform the flux-weakening control using the equation (F), the q-axis current command value that the q-axis current should follow is used as the value of i _q in the equation (F). The motor control device according to claim 13 or claim 14, characterized by the above. The motor control device according to claim 2, wherein the magnetic flux control unit calculates the limit voltage for the induced voltage based on a power supply voltage for driving a synchronous motor. The motor control device according to claim 12, wherein the magnetic flux control unit calculates the limit voltage with respect to the maximum voltage based on a power supply voltage for driving a synchronous motor. The synchronous motor;
An inverter for driving the synchronous motor;
A motor drive system comprising: the motor control device according to claim 1, wherein the magnetic flux weakening control of the synchronous motor is performed by controlling the inverter.

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