JP2011244571A - Motor drive mechanism and motor control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control technique with which a d-axis current can be more appropriately determined in a motor drive mechanism for driving a triple-phase motor.SOLUTION: A motor drive mechanism includes: a triple-phase motor; a battery; an inverter for supplying a triple-phase drive voltage to the triple-phase motor; bus voltage detecting means for detecting a DC voltage supplied from the battery to the inverter as a detection bus voltage; and an inverter controller for controlling the inverter in response to the detection bus voltage. The inverter controller includes current command generating means, voltage command generating means, and inverter control means for controlling the inverter. The current command generating means calculates a reference bus voltage from the detection bus voltage and generates a d-axis current command and a q-axis current command on the basis of the reference bus voltage. The current command generating means regulates the reference bus voltage in response to whether or not a voltage command of each phase reaches a limit voltage for bringing a duty of each corresponding phase into a maximum value or a minimum value.

Description

  The present invention relates to a motor drive mechanism and a motor control device, and more particularly to a motor drive mechanism and a motor control device configured to perform field-weakening control in response to a battery voltage.

  One of the techniques widely used when operating a permanent magnet motor, an induction motor and other three-phase motors by vector control is field-weakening control. The field weakening control is a technique for reducing the induced voltage of the armature winding of the three-phase motor by flowing a d-axis current (field-weakening current) when the three-phase motor is operated at high speed. When vector control is performed, the induced voltage of the armature winding increases as the number of rotations of the three-phase motor increases. At this time, if the induced voltage becomes too high compared to the voltage of the DC power supply (for example, battery) connected to the inverter, the q-axis current (torque current) cannot flow and torque cannot be generated. Can not be. In order to avoid such a problem, the field weakening control is performed by effectively reducing the magnetomotive force of the rotor field by passing a d-axis current (field weakening current) and thereby reducing the induced voltage. It is the gist of.

When performing field-weakening control in a motor drive mechanism (for example, a motor-driven vehicle such as an electric vehicle or a hybrid car) configured such that a DC voltage is supplied from a battery to an inverter that supplies power to a three-phase motor, The magnitude of the current is preferably determined according to the battery voltage. Such a technique is disclosed, for example, in JP-A-7-107772. The publication disclosed a permanent magnet synchronous motor drive control device detects the battery voltage sequentially, and the maximum motor-applied voltage V _{max (PWM} modulation degree from the detected battery voltage inverter may issue 100% In this case, the voltage V) output from the inverter is calculated. The drive control device further calculates a field weakening current command I _d ^* when the voltage V matches the maximum motor applied voltage V _max from the torque command T _ref and the motor rotation speed N. In calculating the field weakening current command I _d ^* , various characteristic parameters of the motor (primary resistance, d-axis inductance of armature winding, q-axis inductance) are used. By calculating the field weakening current command I _d ^* that causes the voltage V output from the inverter to coincide with the maximum motor applied voltage V _max , it is possible to prevent a decrease in efficiency and a decrease in output.

However, according to the inventors' investigation, there is room for improvement in the method for determining the field weakening current (d-axis current) as described above. What is particularly important is that the characteristic parameters of the inverter and the motor vary depending on the operating conditions (for example, the inverter temperature and the motor temperature), and it is difficult to set the characteristic parameters of the inverter and the motor without error. When an error is included in the characteristics of the inverter parameters, the maximum motor-applied voltage V _max calculated from the battery voltage becomes inaccurate. Further, if the motor characteristic parameter includes an error, the field weakening current command I _d ^* calculated from the torque command T _ref and the motor rotation speed N becomes inaccurate.

Japanese Patent Laid-Open No. 7-107772

  Accordingly, an object of the present invention is to provide a d-axis current control method that can more appropriately control the d-axis current (field weakening current) for a motor drive mechanism that operates a three-phase motor.

  In one aspect of the present invention, a motor driving mechanism includes a three-phase motor, a battery, an inverter that receives a DC voltage supplied from the battery and supplies a three-phase driving voltage to the three-phase motor, and a battery that supplies the inverter. Bus voltage detecting means for detecting the detected DC voltage as a detected bus voltage, and an inverter controller for controlling the inverter in response to the detected bus voltage. The inverter controller responds to the current command generating means for generating the d-axis current command and the q-axis current command, and the d-axis current command and the q-axis current command, and the u-phase voltage command, the v-phase voltage command, and the w-phase voltage. A voltage command generating means for generating a command; a duty calculating means for calculating a u-phase duty, a v-phase duty, and a w-phase duty in response to the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command; Inverter control means for controlling the inverter in response to the calculated u-phase duty, v-phase duty, and w-phase duty is provided. The current command generation means calculates a reference bus voltage from the detected bus voltage, and generates a d-axis current command and a q-axis current command based on the reference bus voltage. The current command generator means that the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command have reached a limit voltage that sets the u-phase duty, v-phase duty, and w-phase duty to the maximum value or the minimum value, respectively. Responsive to adjusting the reference bus voltage.

  The current command generation means decreases the reference bus voltage when at least one of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command reaches a limit voltage in a predetermined period in the past. It is preferable to decrease the reference bus voltage when all of the voltage command and the w-phase voltage command do not reach the limit voltage during the predetermined period.

  When the current command generating means calculates the maximum torque in response to the reference bus voltage and the rotor speed of the three-phase motor and calculates the relative torque command from the torque command and the maximum torque, the current command generating means A plurality of current tables describing the combination of the rotor rotational speed and the relationship between the d-axis current command and the q-axis current command are prepared, and the current command generating means is configured to select one of the plurality of current tables based on the reference bus voltage. It is preferable that the selected current table is selected from the above, and the d-axis current command and the q-axis current command are calculated from the combination of the relative torque command and the rotor rotational speed using the selected current table.

  The correspondence relationship between the plurality of current tables and the reference bus voltage is preferably determined such that the larger the reference bus voltage, the larger the q-axis current command and the smaller the absolute value of the d-axis current command.

  When the reference bus voltage is calculated from the sum of the detected bus voltage and the bus voltage compensation value, at least one of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command is a past predetermined period. Preferably, the voltage is decreased when the limit voltage is reached, and is increased when all of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command do not reach the limit voltage during the predetermined period.

  In another aspect of the present invention, a motor control device for controlling an inverter that receives a DC voltage supplied from a battery and supplies a three-phase drive voltage to a three-phase motor has a DC voltage supplied from the battery to the inverter. Bus voltage detecting means for detecting the detected bus voltage, and an inverter controller for controlling the inverter in response to the detected bus voltage. The inverter controller responds to the current command generating means for generating the d-axis current command and the q-axis current command, and the d-axis current command and the q-axis current command, and the u-phase voltage command, the v-phase voltage command, and the w-phase voltage. A voltage command generating means for generating a command; a duty calculating means for calculating a u-phase duty, a v-phase duty, and a w-phase duty in response to the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command; Inverter control means for controlling the inverter in response to the calculated u-phase duty, v-phase duty, and w-phase duty is provided. The current command generation means calculates a reference bus voltage from the detected bus voltage, and generates a d-axis current command and a q-axis current command based on the reference bus voltage. The current command generator means that the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command have reached a limit voltage that sets the u-phase duty, v-phase duty, and w-phase duty to the maximum value or the minimum value, respectively. Responsive to adjusting the reference bus voltage.

  ADVANTAGE OF THE INVENTION According to this invention, the control method of d-axis current which can determine a d-axis current (field-weakening current) more appropriately can be provided with respect to the motor drive mechanism which drives a three-phase motor.

It is a block diagram which shows the structure of the motor drive mechanism of one Embodiment of this invention. It is a block diagram which shows the structure / operation | movement of the inverter controller of the motor drive mechanism of FIG. It is a graph which shows the correspondence of u phase voltage command Vu ^* , v phase voltage command Vv ^*, and w phase voltage command Vw ^* in this embodiment, u phase duty Du, v phase duty Dv, and w phase duty Dw. FIG. 3A is a conceptual diagram illustrating a calculation performed in a current command calculation unit of the inverter controller. FIG. 3B is a conceptual diagram illustrating a calculation performed in a current command calculation unit of the inverter controller. FIG. 3C is a conceptual diagram illustrating a calculation performed in a current command calculation unit of the inverter controller. FIG. 4 is a graph showing an example of the contents of the maximum torque table prepared in the current command calculation unit of the inverter controller. FIG. 5 is a graph showing an example of the contents of a current table prepared in the current command calculation unit of the inverter controller.

  FIG. 1 is a block diagram showing a configuration of a motor drive mechanism 1 according to an embodiment of the present invention. The motor drive mechanism 1 includes a permanent magnet motor 2, an inverter 3, a battery 4, an encoder 5, a bus voltage detection unit 6, a current detection unit 7, and an inverter controller 8. The inverter 3 generates a three-phase drive voltage from the DC voltage supplied from the battery 4 and supplies the generated drive current to the permanent magnet motor 2. The encoder 5 sequentially detects the rotor position θ of the permanent magnet motor 2. The bus voltage detection unit 6 detects a DC voltage supplied from the battery 4 to the inverter 3, that is, a voltage of a bus connecting the inverter 3 and the battery 4. Hereinafter, the bus voltage detected by the bus voltage detector 6 is referred to as a detected bus voltage v_batt. The current detector 7 measures a three-phase current supplied from the inverter 3 to the permanent magnet motor 2, that is, a u-phase current Iu, a v-phase current Iv, and a w-phase current Iw. The inverter controller 8 controls the inverter 3 in response to the detected rotor position θ, the detected bus voltage v_batt, and the three-phase currents Iu, Iv, Iw. The motor drive mechanism 1 having such a configuration is used, for example, in a drive system that drives drive wheels of an electric vehicle or a hybrid car. In this case, the driving force generated by the permanent magnet motor 2 is transmitted to the driving wheels.

FIG. 2A is a block diagram showing the configuration of the inverter controller 8. The inverter controller 8 includes a current command calculation unit 11, a speed calculation unit 12, a three-phase two-phase conversion unit 13, a current control unit 14, a two-phase three-phase conversion unit 15, and a duty calculation unit 16. Yes. The current command calculation unit 11 calculates a d-axis current command Id ^* and a q-axis current command Iq ^* from the torque command T ^* , the detected bus voltage v_batt, and the rotor rotational speed ω. The calculation in the current command calculation unit 11 will be described in detail later. The speed calculation unit 12 calculates the rotor rotational speed ω from the rotor angle θ of the permanent magnet motor 2 that is sequentially detected by the encoder 5. The three-phase / two-phase converter 13 performs three-phase / two-phase conversion on the measured three-phase currents Iu, Iv, Iw, and the d-axis current of the three-phase current supplied from the inverter 3 to the permanent magnet motor 2. A component (that is, d-axis current Id) and a q-axis current component (that is, q-axis current Iq) are calculated. The current control unit 14 performs PI control based on the difference between the d-axis current command Id ^* and the d-axis current Id and the difference between the q-axis current command Iq ^* and the q-axis current Iq, and the d-axis voltage command Vd ^*. And q-axis voltage command Vq ^* is calculated. The two-phase / three-phase conversion unit 15 performs two-phase / three-phase conversion on the d-axis voltage command Vd ^* and the q-axis voltage command Vq ^* , and performs the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage. Command Vw ^* is generated.

The duty calculator 16 calculates the u-phase duty Du (that is, the u-phase PWM modulation factor) and the v-phase duty from the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* , respectively. Dv and w-phase duty Dw are calculated. The u-phase duty Du, the v-phase duty Dv and the w-phase duty Dw are not less than a predetermined lower limit value D _MIN (typically 0%) and not more than a predetermined upper limit value D _MAX (typically 100%). Takes a value.

FIG. 2B is a graph showing a correspondence relationship between the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^* and the w-phase voltage command Vw ^* and the u-phase duty Du, the v-phase duty Dv, and the w-phase duty Dw.

In this embodiment, when the u-phase voltage command Vu ^* does not reach the limit voltages −V _LIM and V _LIM , that is, in the range of −V _LIM or more and V _LIM or less, the u-phase duty Du is u Increased with increasing phase voltage command Vu ^* . At this time, the u-phase duty Du is increased from the lower limit value D _MIN (typically 0%) to the upper limit value D _MAX (typically 100%) as the u-phase voltage command Vu ^* increases. On the other hand, when u-phase voltage command Vu ^* is less than −V _LIM , u-phase duty Du is fixed to lower limit value D _MIN , and when u-phase voltage command Vu ^* exceeds V _LIM , u-phase duty Du Is fixed to the upper limit value D _MAX . The correspondence between the u-phase voltage command Vu ^* and the u-phase duty Du is set in advance in the duty calculator 16 as, for example, a table or an arithmetic expression.

The same applies to the v-phase voltage command Vv ^* and the w-phase voltage command Vw ^* . When the v-phase voltage command Vv ^* and the w-phase voltage command Vw ^* are in the range of −V _LIM or more and V _LIM or less, the v-phase duty Dv and the w-phase duty Dw are respectively the v-phase voltage command Vv ^* and the w-phase voltage. Increased with increase in command Vw ^* . At this time, the v-phase duty Dv and the w-phase duty Dw increase from the lower limit value D _MIN (typically 0%) to the upper limit value D _MAX (typically) as the v-phase voltage command Vv ^* and the w-phase voltage command Vw ^* increase. To 100%). On the other hand, when the v-phase voltage command Vv ^* and the w-phase voltage command Vw ^* are less than −V _LIM , the v-phase duty Dv and the w-phase duty Dw are fixed to the lower limit value D _MIN , respectively, and the v-phase voltage command Vv ^*. and w-phase voltage command Vw ^* are if more than _{V LIM} is, v-phase duty Dv and w-phase duty Dw is fixed to the upper limit value _{D MAX.} The correspondence between the v-phase voltage command Vv ^* and the w-phase voltage command Vw ^* and the v-phase duty Dv and the w-phase duty Dw is set in advance in the duty calculator 16 as, for example, a table or an arithmetic expression.

In addition, the duty calculator 16 sets the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw based on the calculated u-phase duty Du, v-phase duty Dv, and w-phase duty Dw. I do. Specifically, the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw are reset every predetermined period (details will be described later). After the u-phase duty flag flag_du, v-phase duty flag flag_dv, and w-phase duty flag flag_dw are reset, the u-phase duty flag flag_du is set when the u-phase duty Du reaches the lower limit value D _MIN or the upper limit value D _MAX. . Similarly, v-phase duty Dv, the w-phase duty Dw reaches the lower limit value _{D MIN} or the upper limit value _{D MAX,} respectively, v-phase duty flag Flag_dv, the w-phase duty flag flag_dw is set. After the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw are once set, the states are maintained until reset. As described above, since the lower limit value D _MIN or the upper limit value D _MAX of the duty of each phase corresponds to the limit voltage ± V _LIM of the voltage command value of each phase, the u-phase duty flag flag_du, the v-phase duty flag flag_dv and w-phase duty flag flag_dw indicate whether or not the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* have reached the limit voltage ± V _LIM during the past predetermined period. It will be.

  The duty calculator 16 controls the inverter 3 by supplying the calculated u-phase duty Du, v-phase duty Dv, and w-phase duty Dw to the inverter 3. Further, the u-phase duty flag flag_dv, the v-phase duty flag flag_dv, and the u-phase duty flag flag_dv are sent to the current command calculation unit 11 and used in calculations in the current command calculation unit 11 (details will be described later).

  The inverter 3 turns on and off the power transistor by PWM control in response to the u-phase duty Du, the v-phase duty Dv, and the w-phase duty Dw, and generates a three-phase voltage supplied to the permanent magnet motor 2. In FIG. 2A, the configuration of the inverter controller 8 is illustrated as a block, but it should be noted that the inverter controller 8 can be realized by software, hardware, and a combination thereof that perform equivalent operations.

One aim of the motor drive mechanism 1 of the present embodiment is that when the field weakening control is performed, the u-phase duty Du, the v-phase duty Dv, and the w-phase duty Dw reach the upper limit value D _MAX and the lower limit value D _MIN at the last minute. Thus, the d-axis current command Id ^* is determined. In other words, the d-axis current command Id ^* is determined so that the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* reach the limit voltage ± V _LIM at the last minute. Thus determine the d-axis current command Id ^*, during high-speed operation, as small as possible the d-axis current command Id ^* under the condition of utilizing the voltage of the battery 4 to the maximum, permanently high efficiency The magnet motor 2 can be operated.

In order to optimally determine the d-axis current command Id ^* , in the present embodiment, the following calculation is performed by the current command calculation unit 11. 3A to 3C show a procedure in which the current command calculation unit 11 calculates the d-axis current command Id ^* and the q-axis current command Iq ^* from the torque command T ^* , the detected bus voltage v_batt, and the rotor rotational speed ω. FIG. The current command calculation unit 11 performs the following three operations: (1) calculation of the reference bus voltage vb ^* , (2) calculation of the relative torque command Tr ^* , and (3) d-axis current command Id ^* and q-axis current. The final calculation of the command Iq ^* is performed.

Referring to FIG. 3A, reference bus voltage vb ^* is calculated by adding bus voltage compensation value vb_repair to detection bus voltage v_batt and subtracting predetermined value Voffset. As will be described later, the reference bus voltage vb ^* is used to calculate the allowable maximum torque T_max, the d-axis current command Id ^*, and the q-axis current command Iq ^* .

Here, in this embodiment, the bus voltage compensation value vb_repair used for calculating the reference bus voltage vb ^* is the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase during the past predetermined time. The voltage command Vw ^* is adjusted according to whether or not the limit voltage ± V _LIM has been reached. More specifically, at least one of the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw is set (when it is “1” in the present embodiment), and the bus voltage compensation value vb_repair is set. It is reduced by a predetermined value V _ON from the previous value. Otherwise, that is, when all of the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw are reset (in the present embodiment, “0”), the bus voltage compensation value vb_repair is It is decreased by a predetermined value V _OFF from the previous value. However, an upper limit value VH (> 0) and a lower limit value VL (<0) are determined for the bus voltage compensation value vb_repair, and the bus voltage compensation value vb_repair is increased or decreased within a range from VL to VH.

By calculating the reference bus voltage vb ^* using the bus voltage compensation value vb_repair adjusted in this way, as a result, the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* are obtained. The reference bus voltage vb ^* is calculated so as to reach the limit voltage ± V _LIM at the last minute.

The update of the bus voltage compensation value vb_repair and the calculation of the reference bus voltage vb ^* are performed at predetermined time intervals, for example, every 1 msec. When the calculation of the reference bus voltage vb ^* and the update of the bus voltage compensation value vb_repair are completed, the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw are reset, and the same control is performed again.

Note that the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw are also reset at predetermined time intervals. This is because the u-phase duty flag flag_du, the v-phase duty flag flag_dv, and the w-phase duty flag flag_dw are respectively the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw during the past predetermined time. It means that ^* indicates whether or not the limit voltage ± V _LIM has been reached. That is, when the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* reach the limit voltage ± V _LIM during the past predetermined time, the u-phase duty flag flag_du, v-phase, respectively. The duty flag flag_dv and the w-phase duty flag flag_dw are set. On the other hand, if the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* have not reached the limit voltage ± V _LIM during the past predetermined time, the u-phase duty flag flag_du, The v-phase duty flag flag_dv and the w-phase duty flag flag_dw are maintained in reset.

As shown in FIG. 3B, the reference bus voltage vb ^* calculated in this way is used to generate the relative torque command Tr ^* . Specifically, the maximum torque T _max is calculated from the reference bus voltage vb ^* and the rotor rotational speed ω of the permanent magnet motor 2. In one embodiment, the current command calculation unit 11 is provided with a maximum torque table that describes the relationship between the combination of the reference bus voltage vb ^* and the rotor rotational speed ω and the corresponding maximum torque T _max , and uses that table. A maximum torque T _max is determined. FIG. 4 is a graph showing an example of the content of the maximum torque table. Maximum torque T _max is in the range from the rotor rotational speed omega is 0 to the limit rotational speed omega _{T_LIM} is maintained at a predetermined value, gradually decreases with increasing rotor rotational speed omega exceeds the limit rotational speed ω _{T_LIM.} Here, limit rotational speed ω _{T_LIM} is increased with an increase in reference bus voltage vb ^* . The relative torque command Tr ^* is calculated by dividing the torque command T ^* given from the outside by the maximum torque _Tmax . However, the relative torque command Tr ^* is limited to 100% or less.

The relative torque command Tr ^* thus calculated is used for final calculation of the d-axis current command Id ^* and the q-axis current command Iq ^* as shown in FIG. 3C. Specifically, the d-axis current command Id ^* and the q-axis current command Iq ^* are calculated from the relative torque command Tr ^* , the reference bus voltage vb ^*, and the rotor rotational speed ω. For this calculation, the current command calculation unit 11 describes a combination of the relative torque command Tr ^* and the rotor rotational speed ω and a current describing the relationship between the corresponding d-axis current command Id ^* and q-axis current command Iq ^*. Multiple tables are prepared. Each current table is associated with the reference bus voltage vb ^* , and the reference bus voltage vb ^* is actually used to calculate the d-axis current command Id ^* and the q-axis current command Iq ^* from the plurality of current tables. Used to select the current table used.

FIG. 5 is a diagram showing the contents of a current table prepared in the current command calculation unit 11. q-axis current command Iq ^* is in a range from the rotor rotational speed omega is 0 to the limit rotational speed omega _{Iq_LIM} is maintained at a predetermined value, gradually decreases with increasing rotor rotational speed omega exceeds the limit rotational speed omega _{Iq_LIM} . Here, limit rotational speed ω _{Iq_LIM} is increased with an increase in relative torque command Tr ^* . On the other hand, d-axis current command Id * ^(absolute value) is in the range from the rotor rotational speed omega is 0 to the limit rotational speed omega _{Id_LIM} is maintained at a predetermined value, the rotor rotational speed of the omega exceeds the limit rotational speed omega _{Id_LIM} It is gradually increased with the increase. Here, limit rotational speed ω _{Id_LIM} is increased with an increase in relative torque command Tr ^* . The plurality of current tables prepared in the current command calculation unit 11 are determined such that the limit rotational speeds ω _{Iq_LIM} and ω _{Id_LIM} increase as the corresponding reference bus voltage vb ^* increases. In other words, as the corresponding reference bus voltage vb ^* increases, the q-axis current command Iq ^* increases and the d-axis current command Id ^* decreases.

One of a plurality of current tables is selected based on the reference bus voltage vb ^* , and the d-axis current commands Id ^* and q corresponding to the combination of the relative torque command Tr ^* and the rotor rotational speed ω using the selected current table. A shaft current command Iq ^* is obtained. The obtained d-axis current command Id ^* and q-axis current command Iq ^* are sent to the current control unit 14 and used for current control.

As described above, in the present embodiment, the bus voltage compensation value vb_repair (that is, the reference bus voltage vb ^* ) is determined by the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^*. Is adjusted according to whether or not the voltage reaches the limit voltage ± V _LIM , whereby the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* are limited to the limit voltage ± V _LIM . In this way, the reference bus voltage vb ^* is determined. Further, the d-axis current command Id ^* is determined using the reference bus voltage vb ^* determined as described above. As a result, when the field weakening control is performed, the motor drive mechanism 1 of the present embodiment makes the d-axis current command Id ^* as small as possible while effectively using the voltage of the battery 4 (detection bus voltage v_batt). In addition, the permanent magnet motor 2 can be operated with high efficiency.

At this time, in the motor drive mechanism 1 of the present embodiment, depending on whether the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^*, and the w-phase voltage command Vw ^* have actually reached the limit voltage ± V _LIM. since the reference bus voltage vb ^* is adjusted Te, characteristic parameter is the operating condition of the permanent magnet motor 2 and the inverter 3 (e.g., inverter temperature and motor temperature, etc.) changes, the appropriate d-axis current command Id ^* Can be calculated.

  Although the embodiments of the present invention are specifically described above, the present invention is not limited to the above-described embodiments. Various modifications obvious to those skilled in the art can be made to the embodiments of the present invention. For example, although the motor drive mechanism 1 of the present embodiment includes the permanent magnet motor 2, another three-phase motor (for example, an induction motor) that can be operated by vector control instead of the permanent magnet motor 2 may be used. Good.

1: Motor drive mechanism 2: Permanent magnet motor 3: Inverter 4: Battery 5: Encoder 6: Bus voltage detection unit 7: Current detection unit 8: Inverter controller 11: Current command calculation unit 12: Speed calculation unit 13: Three-phase 2 Phase conversion unit 14: Current control unit 15: Two-phase three-phase conversion unit 16: Duty calculation unit

Claims (7)

A three-phase motor,
Battery,
An inverter that receives a DC voltage from the battery and supplies a three-phase drive voltage to a three-phase motor;
Bus voltage detection means for detecting a DC voltage supplied from the battery to the inverter as a detection bus voltage;
An inverter controller that controls the inverter in response to the detected bus voltage;
The inverter controller is
current command generating means for generating a d-axis current command and a q-axis current command;
Voltage command generation means for generating a u-phase voltage command, a v-phase voltage command, and a w-phase voltage command in response to the d-axis current command and the q-axis current command;
Duty calculation means for calculating a u-phase duty, a v-phase duty, and a w-phase duty in response to the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command;
Inverter control means for controlling the inverter in response to the u-phase duty, the v-phase duty, and the w-phase duty,
The current command generation means calculates a reference bus voltage from the detected bus voltage, generates the d-axis current command and the q-axis current command based on the reference bus voltage,
In the current command generation means, the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command set the u-phase duty, the v-phase duty, and the w-phase duty to a maximum value or a minimum value, respectively. A motor drive mechanism that adjusts the reference bus voltage in response to whether a limit voltage has been reached. The motor drive mechanism according to claim 1,
The current command generation means decreases the reference bus voltage when at least one of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command reaches the limit voltage in a predetermined period in the past, A motor drive mechanism that reduces the reference bus voltage when all of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command do not reach the limit voltage during a predetermined period. The motor drive mechanism according to claim 2,
The current command generation means calculates a maximum torque in response to the reference bus voltage and the rotor speed of the three-phase motor, calculates a relative torque command from the torque command and the maximum torque,
The current command generating means is provided with a plurality of current tables in which a combination of the relative torque command and the rotor rotational speed and a relationship between the d-axis current command and the q-axis current command are described.
The current command generation means selects a selected current table from the plurality of current tables based on the reference bus voltage, and uses the selected current table to determine the d from the combination of the relative torque command and the rotor rotational speed. A motor drive mechanism that calculates an axis current command and the q-axis current command. The motor drive mechanism according to claim 3,
The correspondence relationship between the plurality of current tables and the reference bus voltage is determined such that the larger the reference bus voltage, the larger the q-axis current command and the smaller the absolute value of the d-axis current command. Motor drive mechanism. The motor drive mechanism according to any one of claims 1 to 4,
The reference bus voltage is calculated from the sum of the detected bus voltage and a bus voltage compensation value;
The bus voltage compensation value is decreased when at least one of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command reaches the limit voltage in the predetermined period, and the u-phase voltage command in the predetermined period. A motor drive mechanism that is increased when all of the voltage command, the v-phase voltage command, and the w-phase voltage command do not reach the limit voltage. A motor control device for controlling an inverter that receives a DC voltage from a battery and supplies a three-phase drive voltage to a three-phase motor,
Bus voltage detection means for detecting a DC voltage supplied from the battery to the inverter as a detection bus voltage;
An inverter controller that controls the inverter in response to the detected bus voltage;
The inverter controller is
current command generating means for generating a d-axis current command and a q-axis current command;
Voltage command generation means for generating a u-phase voltage command, a v-phase voltage command, and a w-phase voltage command in response to the d-axis current command and the q-axis current command;
Duty calculation means for calculating a u-phase duty, a v-phase duty, and a w-phase duty in response to the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command;
Inverter control means for controlling the inverter in response to the u-phase duty, the v-phase duty, and the w-phase duty,
The current command generation means calculates a reference bus voltage from the detected bus voltage, generates the d-axis current command and the q-axis current command based on the reference bus voltage,
In the current command generation means, the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command set the u-phase duty, the v-phase duty, and the w-phase duty to a maximum value or a minimum value, respectively. A motor control device that adjusts the reference bus voltage in response to whether or not a limit voltage has been reached. The motor control device according to claim 6,
The current command generation means decreases the reference bus voltage when at least one of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command reaches the limit voltage in a predetermined period in the past, A motor control device that decreases the reference bus voltage when all of the u-phase voltage command, the v-phase voltage command, and the w-phase voltage command do not reach the limit voltage in a predetermined period.

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