JP2019161854A - Motor control method and motor control apparatus - Google Patents

Abstract

To provide a technique capable of suitably performing switching determination from voltage phase control to current vector control even when output torque of a motor is reduced.SOLUTION: A motor control method includes: a current control step for executing current control for controlling a motor 9 by controlling a current in accordance with a torque command value to the motor 9; a voltage phase control step for executing voltage phase control for controlling the motor 9 by controlling a voltage phase in accordance with the torque command value to the motor; a mode switching determination step for determining whether or not a control mode of the motor 9 is to be switched from voltage phase control to current control; and a mode switching step for switching a control mode in accordance with a determination result of the mode switching determination step. The mode switching determination step is performed on the basis of a q-axis current when deceleration of the motor 9 is a predetermined value and more, and is performed on the basis of a d-axis current when the deceleration of the motor is less than the predetermined value.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a motor control method and a motor control device.

  As a motor control method, a current vector control for controlling a vector of a current (motor current) applied to the motor and a voltage phase control for controlling a phase of a voltage applied to the motor are known. The current vector control and the voltage phase control are switched according to the operating state of the motor.

  In Patent Document 1, voltage phase control is performed based on a current (q-axis current) detected at a timing such that the motor current has a larger amplitude and the phase is on the lag side compared with the fundamental current. A motor control method for switching from current to current vector control is disclosed.

JP 2010-124666 A

  However, in the technique disclosed in Patent Document 1, since the motor control method is switched based on the q-axis current, the switching determination is performed in a region where the q-axis current is small, such as a scene where the motor output torque is small. In such a case, the difference between the detected q-axis current and the noise becomes small, and the switching determination may not be appropriately performed.

  An object of the present invention is to provide a technique capable of appropriately performing switching determination from voltage phase control to current vector control even in a scene where the output torque of a motor becomes small.

  According to the motor control method of the present invention, the current control step for executing the current control for controlling the motor by controlling the current according to the torque command value for the motor, and the voltage phase according to the torque command value for the motor are controlled. A voltage phase control step for performing voltage phase control for controlling the motor, a mode switching determination step for determining whether or not the motor control mode is switched from voltage phase control to current control, and a mode switching determination step. A mode switching step for switching the control mode according to the determination result. The mode switching determination step is performed based on the q-axis current when the motor deceleration is equal to or greater than a predetermined value, and the motor deceleration is predetermined. When the value is less than the value, the measurement is performed based on the d-axis current.

  According to the present invention, whether or not the motor control mode is switched from voltage phase control to current control is determined when the motor deceleration is greater than or equal to a predetermined value, that is, the q-axis current increase rate is relatively high. Since it is performed only on the basis of the q-axis current and based on the d-axis current when the motor deceleration is less than a predetermined value, the voltage phase control is performed even on the scene where the motor output torque is reduced. The switching determination from current control to current control can be performed appropriately.

FIG. 1 is a schematic configuration diagram illustrating a main configuration of an electric vehicle including a motor control device according to the present invention. FIG. 2 is a block diagram showing details of the current vector control unit. FIG. 3 is a block diagram showing details of the voltage phase control unit. FIG. 4 is a block diagram illustrating details of the control mode switching unit. FIG. 5 is a flowchart showing the flow of the control mode determination process. FIG. 6 is a dq-axis coordinate vector plan view showing current vectors and voltage vectors in a normal state. FIG. 7 is a dq-axis coordinate vector plan view showing current vectors and voltage vectors during rapid deceleration. FIG. 8 is a diagram for explaining current regions of current control and voltage phase control.

[One Embodiment]
FIG. 1 is a block diagram illustrating a main configuration of an electric vehicle including a motor control device according to an embodiment of the present invention. Hereinafter, the configuration of each block will be described with reference to FIG. The motor control device according to the present invention can be applied to an electric vehicle including a motor that functions as a part or all of a drive source of the vehicle. Electric vehicles include not only electric vehicles but also hybrid vehicles and fuel cell vehicles.

The current vector control unit 1 executes current control (current vector control) for controlling driving of the motor 9 by controlling a current applied to the motor 9. Specifically, the current vector control unit 1 is based on the target torque T ^* , the rotation speed N of the motor 9, the voltage detection value v _dc of the battery 19, and the dq axis current detection values i _d and i _q. The dq axis current command values i _d ^* and i _q ^* and the dq axis voltage command values v _di ^* and v _qi ^* for causing the motor 9 to generate (output) a desired torque are calculated, and the control mode switching unit 3 Output to. The target torque T ^* is a torque command value determined according to the accelerator depression amount (accelerator opening) or the like. The current vector control unit 1 is an example of a current control unit that performs a current control step. Details of the current vector control unit 1 will be described later with reference to FIG.

The voltage phase control unit 2 executes voltage phase control for controlling the driving of the motor 9 by controlling the phase of the voltage applied to the motor 9. Specifically, the voltage phase control unit 2 is based on the target torque T ^* , the rotation speed N of the motor 9, the voltage detection value v _dc of the battery 19, and the dq axis current detection values i _d and i _q. The voltage amplitude command value v _a ^* and the dq axis voltage command values v _di ^* and v _qi ^* for causing the motor 9 to generate a desired torque are calculated and output to the control mode switching unit 3. The voltage phase control unit 2 is an example of a voltage phase control unit that executes a voltage phase control step. Details of the voltage phase control unit 2 will be described with reference to FIG.

The control mode switching unit 3 switches a method (control mode) for controlling the motor 9. Specifically, the control mode switching unit 3 determines a voltage command value (dq-axis voltage command value v by current vector control) based on the rotational speed change rate dN / dt and the dq-axis current detection values i _d and i _{q. di} ^* , v _qi ^* ) and a voltage command value (dq axis voltage command value v _di ^* , v _qi ^* ) by voltage phase control are determined to be switched, and the one selected based on the determination result is determined. The voltage command value is output to the coordinate converter 4. The control mode switching unit 3 is an example of a mode switching determination unit and a mode switching unit that execute a mode switching determination step and a mode switching step. Details of the control mode switching unit 3 will be described later with reference to FIG.

  Next, the motor control unit 40 will be described. The motor control unit 40 includes a coordinate converter 4, a voltage sensor 7, a PWM converter 5, an inverter 6, a current sensor 8, a battery 19, a coordinate converter 12, and a rotation speed change rate calculator 13.

The coordinate converter 4 is a converter that performs coordinate conversion from the dq axis to the UVW phase. The coordinate converter 4 performs coordinate conversion of the d-axis voltage command value v _d ^* and the q-axis voltage command value v _q ^* using the following formula, and converts the conversion result into the three-phase voltage command values v _u ^* , v _v ^*, _v PWM converter 5 to output as ^{w *.}

The PWM converter 5 receives the three-phase voltage command values v _u ^* , v _v ^* , and v _w ^* from the coordinate converter 4 and the voltage detection value v _dc from the voltage sensor 7. The voltage sensor 7 is a sensor that detects a drive voltage supplied from the battery 19 to the inverter 6. The PWM converter 5 corrects the three-phase voltage command values v _u ^* , v _v ^* , and v _w ^* using a known dead time compensation technique, a voltage utilization ratio improvement technique, and the like. The PWM converter 5 generates drive signals D _uu ^* , D _ul ^* , D _vu ^* , D _vl ^* , D _wu ^* , and D _wl ^* that are used to drive the power elements included in the inverter 6. Output.

The inverter 6 is composed of three-phase six-arms and includes six power elements, two for each phase. The inverter 6 drives the power elements based on the drive signal output from the PWM converter 5 to generate PWM voltages v _u , v _v , and v _w that are pseudo AC voltages. The inverter 6 supplies PWM voltages v _u , v _v and v _w to the motor 9.

Since the motor 9 is driven in three phases, the inverter 6 and the motor 9 are connected by three wires corresponding to the three phases. A PWM voltage v _u is input to the motor 9 via the u-phase wiring, a PWM voltage v _v is input via the v-phase wiring, and a PWM voltage v _w is input via the w-phase wiring. The u-phase wiring is provided with a current sensor 8u, and the v-phase wiring is provided with a current sensor 8v. The u-phase current value i _u detected by the current sensor 8 _u and the v-phase current value iv detected by the current sensor 8 _v are output to the coordinate converter 12.

Here, since the sum of i _u , i _v , and i _w , which are three-phase currents, becomes zero, the w-phase current value i _w can be expressed by the following equation.

  The coordinate converter 12 is a converter that performs coordinate conversion from the UVW phase to the dq axis using the following equation (3).

(3) As indicated formula, coordinate converter 12, u-phase current value i _u, and, with respect to the V-phase current value i _v, a coordinate conversion based on the electrical angle θ outputted from the rotation sensor 10 Do. Then, the coordinate converter 12 outputs the d-axis current value i _d and the q-axis current value i _q that are the conversion results to the current vector control unit 1, the voltage phase control unit 2, and the control mode switching unit 3. To do.

  The rotation sensor 10 is provided adjacent to the motor 9 and detects the electrical angle θ of the rotor of the motor 9. The rotation sensor 10 outputs the detected electrical angle θ to the coordinate converters 4 and 12 and the rotation speed calculator 11.

  The rotational speed calculator 11 calculates the rotational speed N of the motor 9 from the amount of change of the electrical angle θ per time and outputs it to the rotational speed change rate calculator 13.

  The rotational speed change rate calculator 13 calculates the rotational speed change rate dN / dt of the motor 9 from the amount of change of the rotational speed N of the motor 9 per time, and outputs it to the control mode switching unit 3.

  Next, details of each block according to the above-described current vector control unit 1, voltage phase control unit 2, and control mode switching unit 3 will be described. Note that the current vector control unit 1, the voltage phase control unit 2, and the control mode switching unit 3 according to the present embodiment are configured as functional units provided in at least one controller. The controller includes, for example, a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

FIG. 2 is a diagram illustrating an example of a block configuration that implements the current vector control unit 1 of the present embodiment. The current vector control unit 1 includes a current command value calculator 14, a non-interference voltage calculator 15, a PI compensator 16, a subtracter 17, and an adder 18. Note that FIG. 2 shows only signals related to the calculation of the d-axis voltage command value v _di ^* , and omits signals related to the calculation of the q-axis voltage command value v _qi ^* input / output to / from each block. .

The current command value calculator 14 stores a table in which the target torque T ^{* is associated} with the d-axis current command value i _d ^* and the q-axis current command value i _q ^* . This table is obtained in advance by experiment or analysis. In addition, it is preferable that the temperature characteristics of the motor 9 are taken into account in this table. The current command value calculator 14 refers to this table, and the d-axis current command value i corresponding to the input target torque T ^* , the rotational speed N of the motor 9, and the voltage detection value v _dc of the battery 19. _d ^* and the q-axis current command value i _q ^* are obtained, and these command values are output to the subtractor 17. The current command value calculator 14 also outputs these command values to the control mode switching unit 3.

The subtractor 17 calculates a deviation between the d-axis current command value i _d ^* and the q-axis current command value i _q ^* and the d-axis current detection value i _d and the q-axis current detection value i _q. , Output to the PI compensator 16.

The PI compensator 16 is an arithmetic unit that performs so-called PI control. The PI compensator 16 calculates a value obtained by multiplying a deviation between the dq-axis current command values i _d ^* and i _q ^* and the dq-axis current detection values i _d and i _q by a proportional gain, and an integral value of the deviation. And the value obtained by multiplying by the integral gain are added together, and the added values v _{d_fb} ^* and v _{q_fb} ^* are output to the adder 18.

The non-interference voltage calculator 15 refers to a table stored in advance, and determines d according to the input target torque T ^* , the rotational speed N of the motor 9, and the voltage detection value _vdc of the battery 19. An axis non- _interacting voltage command value v _{d_dcpl} ^* and a q-axis non- _interacting voltage command value v _{q_dcpl} ^* are obtained, and these command values are output to the adder 18.

Then, in the adder 18, the dq-axis non-interference voltage command value _{v D_dcpl} ^*, and _{v Q_dcpl} ^*, the output value _v of the PI compensator ₁₆ d_fb ^*, _{v by Q_fb} ^* and are added, the current in the dq-axis Dq axis voltage command values v _di ^* and v _qi ^* in which the interference voltage generated when the current flows are suppressed are calculated. The calculated dq-axis voltage command values v _di ^* and v _qi ^* are output to the control mode switching unit 3.

  Next, the details of the voltage phase control unit 2 will be described with reference to FIG.

  FIG. 3 is a diagram illustrating an example of a block configuration that implements the voltage phase control unit 2 of the present embodiment. The voltage phase control unit 2 includes a voltage amplitude calculator 20, a voltage phase calculator 21, a torque estimator 22, a PI compensator 23, a dq axis voltage generator 24, an adder 25, and a subtractor 26.

The voltage amplitude calculator 20 uses the following equation (4) based on the detected voltage value v _dc of the battery 19 and the command value modulation factor M ^* which is a value stored in advance, and uses the voltage amplitude command value v _a ^*. Is calculated. The calculated voltage amplitude command value v _a ^* is output to the dq axis voltage generator 24 and the control mode switching unit 3.

The voltage phase calculator 21 includes a table obtained in advance by experiment or analysis, and performs voltage phase control according to the input target torque T ^* , the rotation speed N of the motor 9, and the voltage detection value _vdc. The voltage phase command value α _ff ^* to be used is obtained. Then, the voltage phase calculation unit 21 outputs the voltage phase command value α _ff ^* to the adder 25.

The torque estimator 22 stores a table indicating the relationship between the d-axis and q-axis current values flowing to the motor 9 and the torque generated in the motor 9. This table is obtained by experiment or analysis. Torque estimator 22 refers to this table, dq axis current detection value i _d, the i _q, and calculates the estimated torque T _cal as the estimated value of torque generated in the motor 9, the calculated values Output to the subtractor 26.

The subtractor 26 calculates a deviation between the target torque T ^* and the estimated torque T _cal and outputs the obtained value to the PI compensator 23.

The PI compensator 23 is an arithmetic unit that executes so-called PI control. The PI compensator 23 _adds the value obtained by multiplying the deviation between the target torque T ^* and the estimated torque T _cal by the proportional gain and the value obtained by multiplying the integral value of the deviation by the integral gain. The value α _fb ^* is output to the adder 25.

The adder 25 calculates the final voltage phase command value α ^* by adding the voltage phase command values α _ff ^* and α _fb ^*, and outputs the final voltage phase command value α ^* to the dq axis voltage generator 24. To do.

The dq-axis voltage generator 24 uses the following equation (5) based on the input voltage amplitude command value v _a ^* and the final voltage phase command value α ^*, and the d-axis voltage command value v _dv ^* , q-axis The voltage command value v _qv ^* is calculated. The calculated dq axis voltage command values v _dv ^* and v _qv ^* are output to the control mode switching unit 3.

  Next, the details of the control mode switching unit 3 will be described with reference to FIG.

  FIG. 4 is a diagram illustrating an example of a block configuration that implements the control mode switching unit 3 of the present embodiment. The control mode switching unit 3 includes a filter processor 30, a control mode determiner 31, a switcher 32, a switcher 33, and a previous value processor 34.

The filter processor 30 performs a filtering process using the following equation (6) on the input d-axis current command value i _d ^* and the d-axis current detection value i _d to thereby obtain a d-axis current command value. The filter value i _{d_flt} ^* and the d-axis current detection value filter value i _{d_flt} are calculated. However, τ _sw in the following formula (6) is a time constant constituting the low-pass filter.

  The previous value processor 34 stores the value of the control mode flag CNT_FLG, which is the output of the control mode determiner 31 described later. Then, the previous value processor 34 uses the control mode flag previous value CNT_FLG_z (hereinafter, simply referred to as “previous value CNT_FLG_z”) as the value (previous value) one control cycle before the control mode flag CNT_FLG. Output to.

The control mode determiner 31 includes a previous value CNT_FLG_z, a d-axis current command value filter value i _{d_flt} ^* , a d-axis current detection value filter value i _{d_flt} , a q-axis current command value i _q ^* , a q-axis current detection value i _q , a voltage The control mode is determined based on the amplitude command value v _a ^* , the rotation speed change rate dN / dt, and the dq-axis voltage command values v _di ^* and v _qi ^* , and either the current control mode or the voltage phase control mode A control mode flag CNT_FLG instructing one of the control modes is output. Details of the control mode determination process executed in the control mode determination unit 31 will be described later with reference to FIG.

The switches 32 and 33 switch between the current control mode and the voltage phase control mode according to the control mode flag CNT_FLG. Specifically, the switchers 32 and 33 are connected to the voltage command values (dq axis voltage command values v _di ^* , v _qi ^* ) calculated by the current vector control unit 1 and the voltage phase control unit 2 according to the control mode flag CNT_FLG. _Is selected from the voltage command values (dq-axis voltage command values v _dv ^* , v _qv ^* ) calculated in step (1). Then, the selected voltage command value is output to the coordinate converter 4 as dq-axis voltage command values v _d ^* and v _q ^* . Thereby, the current control mode and the voltage phase control mode can be switched as a control mode for operating the motor 9.

  Below, the detail of the control mode determination process performed in the control mode determination device 31 is demonstrated.

  FIG. 5 is a flowchart showing a control mode determination process executed by the control mode determiner 31 of the present embodiment. The control mode determination process described below is programmed in the controller so as to always execute one control cycle shown in FIG. 5 from the start to the end at regular intervals while the vehicle system is activated. .

  In step S501, the controller determines whether or not the control mode before one control cycle is voltage phase control. If the control mode before one control cycle is voltage phase control, the processing after step S504 is executed to determine whether or not to switch to current vector control. If the control mode before one control cycle is current vector control, the processing of steps S502 and S503 is executed to determine whether or not to switch to voltage phase control. Steps S503 and S503 will be described later.

  In step S504, the controller determines whether the rotational speed change rate dN / dt of the motor 9 is equal to or greater than a predetermined value. When the rotational speed change rate dN / dt is large, that is, when the deceleration is large, the change rate (increase rate) of the q-axis current that mainly contributes to torque increase / decrease is higher than the change rate of the d-axis current. large. Therefore, when the deceleration of the vehicle is large, the control mode determination process is faster and more appropriate when the control mode determination process is performed using the q-axis current than when the d-axis current is used. can do. The predetermined value (dN / dt) to be compared in this step is appropriately set to an appropriate value derived from experiments, simulation analysis, or the like based on such a viewpoint. As an example, the rotational speed change rate dN / dt is set such that the increase rate of the q-axis current is larger than the change rate of the d-axis current. When the rotational speed change rate dN / dt of the motor 9 is greater than or equal to a predetermined value, the process of the subsequent step S505 is executed. If the rotational speed change rate dN / dt is less than the predetermined value, the process of step S507 is executed. The term of rapid deceleration used below includes at least the case where the rotational speed change rate dN / dt is equal to or greater than a predetermined value.

In step S505, the controller determines whether or not the absolute value of the q-axis current command value i _q ^* is equal to or greater than a predetermined value. In this step, the controller determines whether or not the motor 9 is in the high torque region. In the present embodiment, the absolute value of the q-axis current command value i _q ^* is used as an index for determining whether or not the motor 9 is in the high torque region. Step S505 is an example of a high torque region determination step for determining whether or not the torque output from the motor 9 is within the high torque region.

Here, in the voltage phase control, if the motor 9 is suddenly decelerated when it is in the high torque region, an overcurrent may be generated due to excessive application of a voltage corresponding to the rotation speed N before deceleration. The generated overcurrent may damage the motor 9 and the inverter 6. Thus, compared to become q-axis current command value i _q ^* of the absolute value in step S505, even if rapid deceleration, the torque equivalent to the extent that overcurrent is not generated q-axis current command value i _q ^* is set . In other words, in this step, a torque region equal to or greater than the torque that generates an overcurrent upon rapid deceleration is set as a high torque region.

In the present embodiment, the absolute value of the q-axis current command value i _q ^* is used as an index for determining whether or not the motor 9 is in the high torque region, but is not necessarily limited thereto. The index for determining whether or not the motor 9 is in the high torque region is not particularly limited as long as it is correlated with the magnitude of the torque of the motor 9. For example, instead of the q-axis current command value i _q ^* , the q-axis current detection value i _q or the estimated value of the q-axis current may be used. Alternatively, a torque command value (target torque T ^* ) for the motor 9, a detected torque value of the motor 9, or an estimated torque value (estimated torque T _cal ) of the motor 9 may be used. Alternatively, it may be implemented by any one of the voltage phase command value α ^* , the voltage phase detection value, and the voltage phase estimation value for the motor 9. The detection method (the detected torque value of the motor 9 and the detected voltage phase value) and the estimated value (the estimated value of the q-axis current and the estimated voltage phase value) used here are known methods. What is necessary is just to use, and it does not specifically limit.

In the present embodiment, if the absolute value of the q-axis current command value i _q ^* is greater than or equal to a predetermined value, the process of the subsequent step S506 is executed. If the absolute value of the q-axis current command value i _q ^* is less than the predetermined value, the process of step S507 is executed.

In step S506, the controller determines whether or not the absolute value of the q-axis current detection value i _q is greater than or equal to the absolute value of the q-axis current command value i _q ^* . In voltage phase control, if the absolute value of the q-axis current detection value i _q is equal to or greater than the absolute value of the q-axis current command value i _q ^* , an overcurrent can occur. Therefore, when it is determined that the absolute value of the q-axis current detection value i _q is greater than or equal to the absolute value of the q-axis current command value i _q ^* , the controller executes the process of step S508 to switch to current vector control. To do. If the absolute value of the q-axis current detection value iq is less than the absolute value of the q-axis current command value i _q ^*, no overcurrent has occurred in this control cycle, so the controller maintains voltage phase control. The process of step S509 is executed.

On the other hand, in step S507, the controller determines whether or not the d-axis current detection value filter value i _{d_flt} is equal to or greater than the d-axis current command value filter value i _{d_flt} ^* . In this step, when it is determined in step S504 that the deceleration of the vehicle is slowly decelerating (not rapidly decelerating), or in step S505, the torque region of the motor 9 is a low torque region (high torque region). This process is executed when it is determined that it is not an area.

Here, since the q-axis current detection value i _q ^* is accompanied by a ripple component due to the influence of noise, if the control mode is switched based on the q-axis current during slow deceleration, a torque step is produced due to the influence of the ripple component. Can do. Therefore, except during sudden deceleration (after NO determination in step 504), the occurrence of a torque step is suppressed by performing control mode switching determination based on the d-axis current filter values ( _{id_flt} , _{id_flt} ^* ). The control mode can be switched. In addition, since the d-axis current is hardly affected by noise even in the low torque region, mode switching determination in the low torque region can be performed by using the d-axis current as an index for determining the control mode in the low torque region (NO determination in step S505). Can be performed properly.

Accordingly, in step S507, the controller performs control mode switching determination by determining whether or not the d-axis current detection value filter value i _{d_flt} is equal to or greater than the d-axis current command value filter value i _{d_flt} ^* . When the d-axis current detection value filter value i _{d_flt} is less than the d-axis current command value filter value i _{d_flt} ^* , it is determined that the so-called field weakening control is performed in a high rotation region, and thus voltage phase control is maintained. Therefore, the process of step S509 is executed. On the other hand, if the d-axis current detection value filter value i _{d_flt} is equal to or greater than the d-axis current command value i _{d_flt} ^*, it is determined that it is not a high rotation region where field weakening control is performed. In order to switch to vector control, the process of step S508 is executed.

  Next, the process of step S502 will be described. Step S502 is a process executed when the control mode before one control cycle is current vector control (NO determination in step S501).

At step S502, the controller, dq-axis voltage command value _v ^di _{*, v} based on _qi ^*, is calculated using the following equation the voltage amplitude _{v a} (7). When the voltage amplitude v _a is calculated, the processing of the subsequent step S503 is executed.

At step S503, the controller, the voltage amplitude _{v a} determines whether the voltage amplitude command value _v ^{a *} or more. If the voltage amplitude v _a is the voltage amplitude command value v _a ^* above, since it is presumed to be in the voltage saturation region, the process of step S509 is performed to switch the control mode to the voltage phase control. If the voltage amplitude v _a is the voltage lower than amplitude command value v _a ^*, in order to maintain the current vector control, the process of step S508 is executed.

  As described above, when the control mode is determined in step S508 or step S509, the control mode determination process for one control cycle ends. Thereby, the control mode for controlling the motor 9 is appropriately selected and switched. Then, with reference to FIGS. 6-8, the effect by performing the above-mentioned control mode determination process is demonstrated.

FIG. 6 shows a current / voltage vector diagram in a normal state other than at least during a rapid deceleration. In the figure, φ _a is a magnetic flux vector, φ ₀ is an armature flux linkage vector, L _d is a d-axis inductance, L _q is a q-axis inductance, ω is a motor electrical angular velocity, I _a is a current vector, and _Ra is a winding. line resistance value, v ₀ is the induction voltage vector, v _a denotes a motor terminal voltage vector of the motor 9.

  In contrast, FIG. 7 shows a current / voltage vector diagram during rapid deceleration. Each symbol in the figure is the same as each symbol shown in FIG.

Armature flux linkage vector φ0 shown in Figure 7 is larger than the phi ₀ shown in FIG. This is because the magnitude of the motor terminal voltage vector v _a is proportional to the magnitude of the electrical angular velocity ω and the armature flux linkage vector phi ₀ of the motor 9. That is, during voltage phase control, control is performed so as to maintain the magnitude of the motor terminal voltage. Therefore, when the electrical angular velocity ω of the motor 9 decreases during rapid deceleration, the armature linkage magnetic flux vector φ ₀ increases. At this time, as shown in FIG. 7, the q-axis current i _q increases.

  Here, each control mode (current vector control, voltage phase control) for controlling the motor 9 is divided into current regions as shown in FIG. When switching between the control modes, ideally, the operating point of the motor 9 is preferably located at the boundary between the voltage phase control region and the current control region. Then, as shown in FIG. 8, when the operating point (current vector) of the motor 9 changes during sudden deceleration or the like, in order to detect whether the operating point exceeds the boundary, the d-axis current, and It can be seen that the q-axis current can be detected more quickly by using a current having a higher rate of change as an index. Therefore, as described above, when the vehicle suddenly decelerates, the amplification factor of the q-axis current iq is increased. Therefore, the control mode switching determination is performed based on the magnitude of the q-axis current, so that the determination is performed based on the d-axis current. The switching determination to the current vector control can be executed earlier than that.

  Thus, at the time of sudden deceleration during voltage phase control, it is possible to switch to current vector control at an earlier stage by performing control mode switching determination using the q-axis current. As a result, in the current vector control after the control mode is switched, control is performed so as to suppress the magnitude of the motor terminal voltage in accordance with the decrease in the motor rotation speed during rapid deceleration. It is possible to suppress the occurrence of overcurrent due to being applied to.

  However, since the q-axis current iq is a value close to zero in the low torque region, it is difficult to perform an appropriate control mode switching determination due to the influence of noise. Therefore, in the present embodiment, it is preferable that the control mode switching process based on the q-axis current is performed in a high torque region (see step S505 in FIG. 5). In the low torque region, even if sudden deceleration occurs during voltage phase control, the amount of increase in current is small, so that it is unlikely that an overcurrent that will damage the motor 9 and the inverter 6 will occur.

As described above, according to the motor control method of the embodiment, the current control for executing the current control (current vector control) for controlling the motor by controlling the current according to the torque command value (target torque T ^* ) for the motor 9. A voltage phase control step for executing voltage phase control for controlling the motor 9 by controlling the voltage phase in accordance with a torque command value for the motor, and whether the control mode of the motor 9 is switched from voltage phase control to current control. A mode switching determination step for determining whether or not, and a mode switching step for switching the control mode according to the determination result in the mode switching determination step. The mode switching determination step includes a deceleration of the motor 9 equal to or greater than a predetermined value. The case is executed based on the q-axis current, and when the motor deceleration is less than the predetermined value, the case is executed based on the d-axis current.

  As a result, whether or not the control mode of the motor 9 is switched from voltage phase control to current control is determined when the deceleration of the motor 9 is greater than or equal to a predetermined value, that is, the increase rate of the q-axis current is greater than the d-axis current. This is performed based on the q-axis current only in relatively high scenes, and based on the d-axis current when the motor deceleration is less than a predetermined value. As a result, even in a scene where the output torque of the motor 9 becomes small, it is possible to more appropriately carry out switching determination from voltage phase control to current vector control. In addition, in a scene where the increase rate of the q-axis current is relatively high with respect to the d-axis current, the switching determination is performed based on the q-axis current, so that the switching determination can be performed earlier than in the past. Therefore, the occurrence of overcurrent can be suppressed more accurately.

  In addition, according to the motor control method of the embodiment, the motor control method further includes a high torque region determination step for determining whether or not the torque output from the motor 9 is in the high torque region. When the speed is equal to or higher than a predetermined value and the torque output from the motor 9 is in the high torque range, the speed is reduced based on the q-axis current, the deceleration of the motor 9 is lower than the predetermined value, and When the torque output from the motor 9 is not in the high torque region, the torque is output based on the d-axis current. As a result, the control mode switching determination based on the q-axis current is performed only in the high torque region and not in the low torque region where the influence of noise or the like is large. Therefore, the switching determination from the voltage phase control to the current vector control is more appropriately performed. Can be implemented. As a result, it is possible to prevent overcurrent that occurs when the torque is high and the deceleration is greater than or equal to a predetermined value.

Furthermore, according to the motor control method of an embodiment, in the high torque region determination step,
Based on one of the q-axis current command value i _q ^* , the q-axis current detection value i _q , and the q-axis current estimated value, it is determined whether or not the torque output from the motor 9 is within the high torque region. Also good.

According to the motor control method of one embodiment, the high torque region determination step is based on any of the torque command value (target torque T ^* ), the detected torque value, and the estimated torque value (estimated torque T _cal ). Further, it may be determined whether or not the torque output from the motor 9 is within the high torque region.

Still further, according to the motor control method of one embodiment, the high torque region determination step is based on one of the voltage phase command value α ^* , the voltage phase detection value, and the voltage phase estimation value used in the voltage phase control. Further, it may be determined whether or not the torque output from the motor 9 is within the high torque region.

  Thereby, it can be determined by various methods whether or not the operating point corresponding to the torque output from the motor 9 is in the high torque region.

Further, according to the motor control method of the embodiment, the filter process using the low-pass filter (filter processor 30) that removes the high-frequency component is executed on the d-axis current. As a result, at times other than sudden deceleration (during slow deceleration), the control mode switching determination is performed based on the filter values ( _{id_flt} , _{id_flt} ^* ) of the d-axis current. The control mode can be switched while suppressing the occurrence of a torque step.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent. For example, the current vector control unit 1, the voltage phase control unit 2, and the control mode switching unit 3 have been described as being configured as one functional unit included in the controller. However, the functional units included in the controller are not necessarily limited to these. . The coordinate converters 4 and 12, or the rotation speed change rate calculator 13, the rotation speed calculator 11 and the like shown in FIG. 1 may also be configured as one functional unit of the controller.

DESCRIPTION OF SYMBOLS 1 ... Current vector control part 2 ... Voltage phase control part 3 ... Control mode switching part (mode switching determination part, mode switching part)
9 ... Motor

Claims (7)

A current control step for executing current control for controlling the motor by controlling the current according to a torque command value for the motor;
A voltage phase control step for performing voltage phase control for controlling the motor by controlling the voltage phase according to a torque command value for the motor;
A mode switching determination step for determining whether or not to switch the control mode of the motor from the voltage phase control to the current control;
A mode switching step of switching the control mode according to a determination result in the mode switching determination step,
The mode switching determination step includes
When the deceleration of the motor is greater than or equal to a predetermined value, it is performed based on the q-axis current,
When the deceleration of the motor is less than a predetermined value, it is performed based on the d-axis current.
Motor control method. The motor control method according to claim 1,
A high torque region determination step of determining whether or not the torque output by the motor is in a high torque region;
The mode switching determination step includes
When the deceleration of the motor is equal to or greater than a predetermined value and the torque output by the motor is within the high torque region, it is performed based on the q-axis current,
When the deceleration of the motor is less than a predetermined value and the torque output by the motor is not within the high torque region, the motor is implemented based on the d-axis current.
Motor control method. The motor control method according to claim 2,
In the high torque region determination step,
Based on one of the torque command value, torque detection value, and torque estimation value, it is determined whether or not the torque output by the motor is within the high torque region.
Motor control method. The motor control method according to claim 2,
In the high torque region determination step,
Determining whether the torque output by the motor is within the high torque region based on any of the voltage phase command value, the voltage phase detection value, and the voltage phase estimation value used in the voltage phase control;
Motor control method. The motor control method according to claim 2,
In the high torque region determination step,
determining whether the torque output by the motor is within the high torque region based on any of the q-axis current command value, the q-axis current detection value, and the q-axis current estimation value;
Motor control method. In the motor control method according to any one of claims 1 to 5,
A filtering process using a low-pass filter that removes high-frequency components is performed on the d-axis current.
Motor control method. A current control unit that executes current control for controlling the motor by controlling the current according to a torque command value for the motor;
A voltage phase control unit that executes voltage phase control for controlling the motor by controlling a voltage phase according to a torque command value for the motor;
A mode switching determination unit for determining whether or not to switch the control mode of the motor from the voltage phase control to the current control;
A mode switching unit that switches the control mode according to a determination result of the mode switching determination unit,
The mode switching determination unit
If the motor deceleration is greater than or equal to a predetermined value, determine whether to switch from the voltage phase control to the current control based on the q-axis current,
If the deceleration of the motor is less than a predetermined value, determine whether to switch from the voltage phase control to the current control based on the d-axis current,
Motor control device.

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