Motor driving device, motor system, and motor driving method

Abstract

To quickly start a motor while preventing the motor from losing synchronization.SOLUTION: A motor driving device 2 includes a power converter 21 and a controller 22. The power converter 21 drives a motor 3 including a rotor 301 having a permanent magnet and a stator 302 around which a coil is wound. The controller 22 executes sensorless control of the motor 3 using the power converter 21. The controller 22 accelerates the rotor 301 by providing an angular difference between the d-axis and the γ-axis to start the motor 3, and controls the power converter 201 so that, during the acceleration of the rotor 301, the d-axis current does not deviate from a certain range, the angular velocity of the rotor 301 increases monotonically, and the angular difference is maintained within a determined range not including zero.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a motor drive device, a motor system, and a method for driving a motor.

Background Art

[0002] During the execution of sensorless control for driving a motor without using a position sensor for detecting the position of a rotor, the motor may lose synchronization. When the motor loses synchronization, excessive torque fluctuations may occur, or the motor may stop without starting normally. The electric power steering device disclosed in Japanese Patent Application Laid-Open No. 2011-131725 (Patent Document 1) detects the loss of synchronization of the motor that occurs during the execution of sensorless control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a motor drive device that executes sensorless control, depending on the use or situation of the motor, there is a demand to start and / or stop the motor promptly. To meet this demand, it is required to increase the angular acceleration of the rotor (the amount of change in the angular velocity of the rotor per unit time). On the other hand, when the angular acceleration of the rotor is high, the possibility of the motor losing synchronization is higher than when the angular acceleration of the rotor is low.

[0005] The present invention has been made to solve the above problems, and one of the objects of the present invention is to quickly start the motor while preventing the motor from losing synchronization. Another object of the present invention is to quickly stop the motor while preventing the motor from losing synchronization.

Means for Solving the Problems

[0006] (1) A motor drive device according to an aspect of the present invention includes a power conversion device and a control device. The power conversion device drives a motor including a rotor having a permanent magnet and a stator around which a coil is wound. The control device performs sensorless control of the motor using the power conversion device. The control device accelerates the rotor by providing an angular difference between the d-axis in the d-q rotating coordinate system and the γ-axis obtained by estimating the d-axis, thereby starting the motor. During the acceleration of the rotor, the control device controls the power conversion device so that the d-axis current does not deviate from a certain range, the angular velocity of the rotor increases monotonically, and the angular difference is maintained within a defined range that does not include zero.

[0007] In the configuration of (1) above, the angular difference is maintained within a defined range, that is, the angular difference is stabilized. As a result, it becomes difficult for the motor to lose synchronization. Therefore, it is possible to set the angular acceleration to a high value, and the starting time of the motor can be shortened. Thus, according to the configuration of (1) above, the motor can be quickly started while preventing the motor from losing synchronization.

[0008] (2) A motor drive device according to another aspect of the present invention includes a power conversion device and a control device. The power conversion device drives a motor including a rotor having a permanent magnet and a stator around which a coil is wound. The control device performs sensorless control of the motor using the power conversion device. The control device decelerates the rotor by providing an angular difference between the d-axis in the d-q rotating coordinate system and the γ-axis obtained by estimating the d-axis, thereby stopping the motor. During the deceleration of the rotor, the control device controls the power conversion device so that the d-axis current does not deviate from a certain range, the angular velocity of the rotor decreases monotonically, and the angular difference is maintained within a defined range that does not include zero.

[0009] In the configuration of (2) above, the angular difference is maintained within a specified range, that is, the angular difference is stabilized. As a result, it becomes difficult for the motor to lose synchronization. Therefore, it becomes possible to set the angular acceleration to a high value, and the stopping time of the motor can be shortened. Thus, according to the configuration of (2) above, the motor can be quickly stopped while preventing the motor from losing synchronization.

[0010] (3) In a method for driving a motor according to still another aspect of the present invention, the motor includes a rotor having a permanent magnet and a stator around which a coil is wound. The method for driving the motor includes a step of starting the motor by accelerating the rotor by providing an angular difference between the d-axis and the γ-axis obtained by estimating the d-axis in the d-q rotating coordinate system. The step of starting the motor includes a step in which the d-axis current does not deviate from a certain range, the angular velocity of the rotor increases monotonically, and the angular difference is maintained within a specified range that does not include zero.

[0011] According to the method of (3) above, similar to the configuration of (1) above, the motor can be quickly started while preventing the motor from losing synchronization.

Effects of the Invention

[0012] According to the present invention, the motor can be quickly started while preventing the motor from losing synchronization. Further, according to the present invention, the motor can be quickly stopped while preventing the motor from losing synchronization.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0015] [Embodiment 1] <System Configuration> FIG. 1 is a diagram showing the overall configuration of a motor system according to an embodiment of the present invention. The motor system 100 is mounted on, for example, an electric vehicle. However, the application of the motor system 100 is not limited to vehicle use. The motor system 100 may be used in a stationary system (for example, an air conditioning system). The motor system 100 includes a power source 1, a motor drive device 2, a motor 3, and a main controller 4.

[0016] The power source 1 supplies power to the motor drive device 2. The power source 1 is, for example, a DC power source (DC system) such as a storage battery or a solar cell. The power source 1 may be an AC power source (AC system).

[0017] The motor drive device 2 drives the motor 3. The motor drive device 2 includes a power conversion device 21 that performs a power conversion operation on the supplied power from the power source 1, and a controller 22 that controls the power conversion device 21 according to a control command from the main controller 4. The control command from the main controller 4 to the controller 22 includes a torque command Tr* and an angular acceleration command (a command regarding the angular acceleration of the motor 3) a*.

[0018] The motor 3 is typically a three-phase AC rotating electric machine. The motor 3 is not provided with a position sensor (resolver) for detecting the position of the rotor. Therefore, the motor drive device 2 executes sensorless control of the motor 3.

[0019] FIG. 2 is a diagram showing an example of the configuration of the motor system 100. However, in FIG. 2, the illustration of the main controller 4 (see FIG. 1) is omitted.

[0020] The power source 1 is a storage battery in this example. The power source 1 outputs DC power to the power conversion device 21 via the DC terminals Tp and Tn of the power conversion device 21. The power source 1 is provided with a monitoring unit (including a voltage sensor, a current sensor, etc.) 11 for monitoring the state of the power source 1. The monitoring unit 11 outputs the monitored voltage, current, etc. to the controller 22.

[0021] The power conversion device 21 converts the DC power from the power source 1 into AC power according to the control command from the controller 22, and outputs the AC power to the motor 3. More specifically, the power conversion device 21 includes, for example, a converter 211, a voltage sensor 212, and an inverter 213.

[0022] The converter 211 is, for example, a chopper-type converter and includes one or more switching elements (not shown). The converter 211 boosts the voltage of the DC power from the power source 1 according to the control command from the controller 22, and outputs the boosted DC power between the power line PL and the power line NL.

[0023] The voltage sensor 212 detects the voltage between the power line PL and the power line NL, and outputs the detected voltage to the controller 22.

[0024] The inverter 213 is, for example, a two-level three-phase full-bridge circuit. The inverter 213 converts the DC power between the power lines PL and NL into AC power according to the control command from the controller 22, and outputs the AC power to the AC terminals Tu, Tv, and Tw. In this example, the inverter 213 includes six switching elements Q1 to Q6 and six freewheel diodes D1 to D6. Each of the switching elements Q1 to Q6 is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), IGBT (Insulated Gate Bipolar Transistor), bipolar transistor, or the like. The freewheel diodes D1 to D6 are connected in anti-parallel to the switching elements Q1 to Q6, respectively. The switching elements Q1 and Q2 are connected in series with each other to form the U-phase arm of the full-bridge circuit. The switching elements Q3 and Q4 are connected in series with each other to form the V-phase arm of the full-bridge circuit. The switching elements Q5 and Q6 are connected in series with each other to form the W-phase arm of the full-bridge circuit. The U-phase arm, V-phase arm, and W-phase arm are connected to the AC terminals Tu, Tv, and Tw, respectively. Each phase arm is connected between the power line PL and the power line NL.

[0025] The motor 3 is a permanent magnet synchronous motor, and includes a rotor 301 having permanent magnets (see FIG. 3) and a stator 302 around which coils are wound. In this example, the stator 302 has a U-phase coil, a V-phase coil, and a W-phase coil. One end of each phase coil is star-connected to the neutral point. The other end of each phase coil is connected to the connection point of the switching element of each phase arm of the inverter 213, respectively.

[0026] Current sensors 31 and 32 are provided in the motor 3. The current sensor 31 detects the V-phase current Iv flowing through the motor 3. The current sensor 32 detects the W-phase current Iw flowing through the motor 3. Each current sensor outputs the detected current to the controller 22.

[0027] Based on the torque command Tr* and the angular acceleration command a* from the main controller 4, and the detection results by various sensors (monitoring unit 11, voltage sensor 212, current sensors 31 and 32, etc.), the controller 22 controls the converter 211 and the inverter 213. For example, the controller 22 outputs a switching signal to each of one or more switching elements included in the converter 211, and outputs a switching signal SW to each of the six switching elements Q1 to Q6 included in the inverter 213. The switching signal SW is typically a PWM (Pulse Width Modulation) signal.

[0028] The controller 22 includes, as main components, a processor 221 and a memory 222. The processor 221 includes a processing circuitry such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The memory 222 includes a volatile storage device such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory), and a non-volatile storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory. The memory 222 stores a system program including an OS (Operating System), a control program including computer-readable code, and various parameters for controlling the power conversion operation by the power conversion device 21. The processor 221 realizes various arithmetic processes by reading out the system program, the control program, and the parameters, expanding them in the memory 222, and executing them. The arithmetic processes by the controller 22 may be realized by an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like.

[0029] Note that it is not essential that the controller 22 of the motor drive device 2 and the main controller 4 are provided separately. The controller 22 may be configured to calculate the torque command Tr* and the angular acceleration command a* by itself.

[0030] <Calculation of the angle difference> Hereinafter, a situation where the motor 3 in a stopped state is started will be described by way of assumption.

[0031] FIG. 3 is a diagram for explaining the relationship between the magnetic pole position of the rotor 301 and the coordinate axes during the start-up of the motor 3. As shown in FIG. 3, the d-axis is the axis extending from the rotation axis C of the rotor 301 toward the N pole of the rotor 301. The d-axis rotates counterclockwise at the angular velocity ω of the rotor 301. The q-axis is an axis orthogonal to the d-axis (an axis extending in a direction advanced by 90 electrical degrees from the d-axis).

[0032] When performing sensorless control of the motor 3, it is difficult for the controller 22 to accurately grasp the d-axis and q-axis of the rotor 301. Therefore, instead of the d-q rotating coordinate system defined by the d-axis and q-axis, a γ-δ rotating coordinate system is used. The γ-δ rotating coordinate system is defined by the γ-axis and δ-axis obtained by estimating the d-axis and q-axis. The γ-axis is the axis extending from the rotation axis C toward the estimated N pole of the rotor 301. The δ-axis is an axis orthogonal to the γ-axis (an axis extending in a direction advanced by 90 electrical degrees from the γ-axis).

[0033] The d-axis current and q-axis current in the γ-δ rotating coordinate system are denoted as Id and Iq, respectively. The d-axis current command and q-axis current command required to generate the torque corresponding to the torque command Tr* in the motor 3 are denoted as Id* and Iq*, respectively. The d-axis current Id is the current used to generate the magnetic field in the motor 3. The q-axis current Iq is the current corresponding to the torque of the motor 3. The controller 22 sets the q-axis current command Iq* to zero and sets the d-axis current command Id* to a variable value, so as not to generate torque in the motor 3 and to generate a magnetic field at a specified position. In the example of FIG. 3, the controller 22 generates a magnetic field of the S pole on the γ-axis. As a result, the rotor 301 rotates so that the N pole of the rotor 301 approaches the S pole (the generated magnetic field).

[0034] Hereinafter, the angular difference between the γ-axis with respect to the d-axis (γ-δ rotating coordinate system with respect to the d-q rotating coordinate system) is described as "angular difference Δθ". Δθ may also be referred to as "angular error" instead of angular difference. The d-axis voltage, q-axis voltage, γ-axis voltage, and δ-axis voltage are described as Vd, Vq, Vγ, and Vδ, respectively. The winding resistance of the coil of the stator 302 is described as R. The d-axis self-inductance and q-axis self-inductance of the coil of the stator 302 are described as Ld and Lq, respectively. The back electromotive force constant of the motor 3 is described as Ke [V / rpm].

[0035] In the d-q rotating coordinate system, the following relationships of equations (1) and (2) exist among the d-axis voltage Vd, q-axis voltage Vq, d-axis current Id, and q-axis current Iq. For ease of reading, in the equations, symbols (d, q, γ, δ, etc.) for distinguishing the axial directions of voltage / current are described using subscripts.

Equation

[0036] On the other hand, in the γ-δ rotating coordinate system, the γ-axis voltage Vγ and δ-axis voltage Vδ are expressed as in the following equations (3) and (4). Here, it is assumed that Ld = Lq = L.

Equation

[0037] Equations (3) and (4) are represented in matrix form as in the following equation (5).

Equation

[0038] The d-axis voltage Vd and q-axis voltage Vq in the d-q rotating coordinate system are obtained by rotating the γ-axis voltage Vγ and δ-axis voltage Vδ in the γ-δ rotating coordinate system as in the following equation (6).

Equation

[0039] Substituting Equation (5) into the right side of Equation (6) and arranging the terms, the following Equations (7) and (8) are obtained.

Number

[0040] Here, the following Equation (9) always holds for the tangent (tan) of the angle difference Δθ.

Number

[0041] Therefore, from Equations (7) to (9), the angle difference Δθ is expressed as the following Equation (10).

Number

[0042] Equation (10) may be expressed as the following Equation (11).

Number

[0043] The control in this embodiment may be executed based on tan(Δθ) as in Equation (10), or may be executed based on the angle difference Δθ [deg] as in Equation (11). Hereinafter, for the sake of convenience, an example in which the control is executed based on the angle difference Δθ will be described. However, those skilled in the art can appropriately substitute it based on tan(Δθ).

[0044] <Time Chart> ≪Comparative Example≫ To facilitate the understanding of the control during motor startup in this embodiment, first, the control during motor startup in the comparative example will be described.

[0045] FIG. 4 is a time chart showing the time change of each parameter when the motor in the comparative example starts. The horizontal axis represents the elapsed time. The vertical axis represents, in order from the top, the d-axis current Id [A], the angular acceleration a [rpm / s] of the rotor 301, the angular velocity ω [rpm] of the rotor 301, and the angle difference Δθ [deg]. The same applies to FIG. 5 described later.

[0046] During the acceleration of the rotor, the d-axis current is constantly controlled so as not to deviate from a certain range X. Also, the angular acceleration command is constantly controlled so as not to deviate from a certain range Y. Therefore, the angular velocity command monotonically increases (in this example, increases at a constant rate) with the passage of time. When the angular acceleration command is set low to prevent the motor from falling out of synchronization, the motor startup time may become long. On the other hand, when the angular acceleration command is set high to shorten the motor startup time, the rotation of the rotor does not follow the command, and as shown in FIG. 4, the actual angular acceleration and actual angular velocity may vary with time. Then, the angle difference Δθ repeats increases and decreases. As a result, there is a possibility that the motor 3 may fall out of synchronization, particularly when the angle difference Δθ increases.

[0047] ≪This Embodiment≫ FIG. 5 is a time chart showing the time change of each parameter when the motor 3 in Embodiment 1 starts. This time chart is compared with the time chart in the comparative example shown in FIG. 4.

[0048] As shown in FIG. 5, in this embodiment, in addition to being constantly controlled so that the d-axis current does not deviate from a certain range X and the angular acceleration command is constantly controlled so that it does not deviate from a certain range Y (whereby the angular velocity command monotonically increases with the passage of time), the angle difference Δθ is maintained constant. The fact that the angle difference Δθ is "constant" includes, but is not limited to, the situation where the angle difference Δθ is exactly constant at the target value, and means that the angle difference Δθ is within a range including the target value. That is, the angle difference Δθ may slightly vary within the range defined by the upper limit UL and the lower limit LL in the figure. By stabilizing the angle difference Δθ within the said range, it becomes difficult for the motor 3 to fall out of synchronization. Therefore, compared with the comparative example, since it becomes possible to set the angular acceleration command to a high value, the starting time of the motor 3 can be shortened. Thus, according to this embodiment, it becomes possible to start the motor 3 promptly while preventing the motor 3 from falling out of synchronization.

[0049] <Functional block> FIG. 6 is a functional block diagram of the controller 22 in Embodiment 1. The controller 22 includes a current command generation unit 501, subtraction units 502 and 503, a voltage command generation unit 504, an angular velocity command generation unit 505, an angle command generation unit 506, an angle difference calculation unit 507, a subtraction unit 508, a coordinate conversion unit 509, a switching signal generation unit 510, and a coordinate conversion unit 511.

[0050] The current command generation unit 501 receives a torque command Tr* from the main controller 4 (see FIG. 1) in this example. The current command generation unit 501 generates a d-axis current command Id* and a q-axis current command Iq* for generating a torque corresponding to the torque command Tr* according to a previously prepared map, table, etc. The current command generation unit 501 outputs the d-axis current command Id* and the q-axis current command Iq* to the subtraction units 502 and 503 respectively. Also, the current command generation unit 501 outputs the d-axis current command Id* and the q-axis current command Iq* to the angle difference calculation unit 507.

[0051] The subtraction unit 502 calculates the d-axis current deviation ΔId (= Id - Id*), which is the deviation between the d-axis current Id from the coordinate conversion unit 511 and the d-axis current command value Idc from the current command generation unit 501, and outputs the d-axis current deviation ΔId to the voltage command generation unit 504. The subtraction unit 503 calculates the q-axis current deviation ΔIq (= Iq - Iq*), which is the deviation between the q-axis current Iq from the coordinate conversion unit 511 and the q-axis current command Iq* from the current command generation unit 501, and outputs the q-axis current deviation ΔIq to the voltage command generation unit 504.

[0052] The voltage command generation unit 504 performs a proportional-integral (PI) operation on the d-axis current deviation ΔId from the subtraction unit 502, and outputs the operation result as the d-axis voltage command Vd* to the coordinate conversion unit 509. Similarly, the voltage command generation unit 504 performs a PI operation on the q-axis current deviation ΔIq from the subtraction unit 503, and outputs the operation result as the q-axis voltage command Vq* to the coordinate conversion unit 509. In addition, the voltage command generation unit 504 outputs the d-axis voltage command Vd* and the q-axis voltage command Vq* to the angle difference calculation unit 507.

[0053] In this example, the angular velocity command generation unit 505 receives the angular acceleration command a* from the main controller 4 (see FIG. 1). The angular velocity command generation unit 505 calculates the angular velocity command ω* by performing a predetermined operation (for example, integration of the angular acceleration command a*) on the angular acceleration command a*. The angular velocity command generation unit 505 outputs the angular velocity command ω* to the angle command generation unit 506 and the angle difference calculation unit 507.

[0054] The angle command generation unit 506 calculates the angle command θ* by performing a predetermined operation (for example, integration of the angular velocity command ω*) on the angular velocity command ω* from the angular velocity command generation unit 505. The angle command generation unit 506 outputs the angle command θ* to the subtraction unit 508.

[0055] The angle difference calculation unit 507 receives the d-axis current command Id* and q-axis current command Iq* from the current command generation unit 501, the d-axis voltage command Vd* and q-axis voltage command Vq* from the voltage command generation unit 504, and the angular velocity command ω* from the angular velocity command generation unit 505. The angle difference calculation unit 507 calculates the angle difference Δθ according to the above formula (11) and outputs the angle difference Δθ to the subtraction unit 508.

[0056] The subtraction unit 508 calculates the difference (θ* - Δθ) between the angle command θ* from the angle command generation unit 506 and the angle difference Δθ from the angle difference calculation unit 507. This process is equivalent to correcting the angle command θ* by the angle difference Δθ. The subtraction unit 508 outputs the difference, that is, the corrected angle command (θ* - Δθ), to the coordinate conversion units 509 and 511.

[0057] The coordinate conversion unit 509 converts the d-axis voltage command Vd* and q-axis voltage command Vq* in the dq2-phase coordinates into the U-phase voltage command Vu*, V-phase voltage command Vv*, and W-phase voltage command Vw* in the UVW3-phase coordinates according to a known coordinate conversion formula (dq2-phase → UVW3-phase conversion formula) using the corrected angle command (θ* - Δθ) from the subtraction unit 508. The coordinate conversion unit 509 outputs the voltage commands Vu*, Vv*, Vw* for each phase to the switching signal generation unit 510.

[0058] The switching signal generation unit 510 generates a switching signal SW from the voltage commands Vu*, Vv*, Vw* for each phase. More specifically, the switching signal generation unit 510 generates a PWM signal as the switching signal SW based on the comparison between the voltage commands Vu*, Vv*, Vw* and a predetermined carrier wave. The switching signal generation unit 510 outputs the generated switching signal SW to the inverter 213 (see Figure 2).

[0059] The coordinate conversion unit 511 converts the V-phase current Iv and the W-phase current Iw respectively detected by the current sensors 31 and 32 (see FIG. 2) into a d-axis current Id and a q-axis current Iq according to a known coordinate conversion formula (UVW three-phase → dq two-phase conversion formula) using the corrected angle command (θ* - Δθ) from the subtraction unit 508. The coordinate conversion unit 511 outputs the d-axis current Id to the subtraction unit 502 and outputs the q-axis current Iq to the subtraction unit 503.

[0060] As described above, in the first embodiment, the angle difference Δθ is maintained constant by correcting the angle command θ* (corrected angle command (θ* - Δθ)). By stabilizing the angle difference Δθ, it becomes difficult for the motor 3 to lose synchronization. Therefore, it is possible to set the angular acceleration a to a high value without causing the motor 3 to lose synchronization, and the starting time of the motor 3 can be shortened. Thus, according to the first embodiment, the motor 3 can be started promptly while preventing the motor 3 from losing synchronization.

[0061] [Modification Example] In the first embodiment, the control during the start of the motor 3 (during the acceleration of the rotor 301) was described. In this modification example, the control during the stop of the motor 3 (during the deceleration of the rotor 301) will be described.

[0062] FIG. 7 is a diagram for explaining the relationship between the magnetic pole position of the rotor 301 and the coordinate axes during the stop of the motor 3. This figure is compared with FIG. 3 regarding the start of the motor 3. FIG. 8 is a conceptual diagram for explaining the angle difference Δθ during the start and stop of the motor 3. As shown in FIGS. 7 and 8, during the stop of the motor 3, the angle difference Δθ is set in the direction opposite to that during the start of the motor 3 (opposite to the angular velocity ω). While the angle difference Δθ during the start of the motor 3 is a positive value (Δθ > 0), the angle difference Δθ during the stop of the motor 3 is a negative value (Δθ < 0).

[0063] FIG. 9 is a time chart showing the time change of each parameter during the stop of the motor 3. As shown in FIG. 9, the angle difference Δθ is constantly maintained at a negative value. Similar to when the motor 3 is starting, the angle difference Δθ may slightly vary within the range defined by the upper limit UL and the lower limit LL. By stabilizing the angle difference Δθ within this range, it becomes difficult for the motor 3 to lose synchronization.

[0064] Note that since the functional block diagram during the stop of the motor 3 is equivalent to the functional block diagram during the start of the motor 3 (see FIG. 6), a detailed description will not be repeated.

[0065] As described above, in the modification of Embodiment 1, although the sign of the angle difference Δθ is different, the angle difference Δθ is maintained constant in the same manner as in Embodiment 1. By stabilizing the angle difference Δθ, it becomes possible to set the angular acceleration a to a high value without causing the motor 3 to lose synchronization. As a result, the stop time of the motor 3 can be shortened. Therefore, according to the modification of Embodiment 1, the motor 3 can be quickly stopped while preventing the motor 3 from losing synchronization. For example, when the motor 3 employs an air bearing, by quickly stopping the motor 3, wear of the shaft (journal) and the receiving part (sleeve) can be minimized.

[0066] [Embodiment 2] In Embodiment 2, a configuration will be described in which various additional controls are executed according to the angle difference Δθ. In the following, for ease of understanding, the description will be made assuming that the motor 3 is starting, but the same control can also be executed during the stop of the motor 3.

[0067] Note that the overall configuration of the motor system in Embodiment 2 is the same as the overall configuration of the motor system 100 in Embodiment 1 (see FIGS. 1 and 2) except that the motor drive device 2 includes a controller 22A (see FIG. 13) instead of the controller 22, so the description will not be repeated.

[0068] <Execution Conditions> FIG. 10 is a conceptual diagram for explaining the execution conditions of various controls in the second embodiment. In the second embodiment, as shown in FIG. 10, three threshold values are set for the angle difference Δθ. The three threshold values increase in the order of the first threshold value TH1, the second threshold value TH2, and the third threshold value TH3. Note that the angles in the figure regarding the threshold values and the specific numerical values described later are exemplary and are not limited thereto.

[0069] The controller 22A is configured to execute angle difference correction control, motor deterioration detection, and angular acceleration correction control according to the magnitude relationship with the three threshold values. More specifically, when the angle difference Δθ exceeds the first threshold value TH1, the controller 22A executes angle difference correction control. When the angle difference Δθ exceeds the second threshold value TH2, the controller 22A executes motor deterioration detection. When the angle difference Δθ exceeds the third threshold value TH3, the controller 22A executes angular acceleration correction control.

[0070] Note that, as described with reference to FIG. 13, motor deterioration detection is executed when the angle difference after correction by the angle difference correction control exceeds the second threshold value TH2. Angular acceleration correction control is executed when the angle difference after correction by the angle difference correction control exceeds the third threshold value TH3. However, for simplicity, in FIGS. 10 to 12, the angle difference Δθ is simply described instead of the angle difference after correction.

[0071] ≪Angle Difference Correction Control≫ FIG. 11 is a time chart for explaining the angle difference correction control. The horizontal axis represents the elapsed time. The upper vertical axis represents the angle difference Δθ, and the lower vertical axis represents the correction amount Q of the angle difference.

[0072] The angle difference correction control is a control for reducing the angle difference Δθ by the correction amount Q when the angle difference Δθ exceeds the first threshold value TH1. In other words, it is a control for returning the d-axis that has deviated excessively from the γ-axis toward the γ-axis by the correction amount Q. The angle difference after correction is described as (Δθ - Q). The correction amount Q is 0 or a positive value.

[0073] The angular difference Δθ at the start of the motor 3 (refer to time t0) is usually zero. After starting the motor 3, as the angular velocity ω increases, the angular difference Δθ also increases naturally. During this period, there is no need to decrease the angular difference Δθ. Therefore, when the angular difference Δθ is equal to or less than the first threshold value TH1, the angular difference Δθ is not corrected, and the correction amount Q is set to zero.

[0074] The first threshold value TH1 is set in advance according to the specifications of the motor 3 to a value exceeding the normal increase amount of the angular difference Δθ with the increase in the angular velocity ω. For example, the first threshold value TH1 is TH1 = 20°.

[0075] The fact that the angular difference Δθ exceeds the first threshold value TH1 means that the angular difference Δθ has increased beyond the normal increase amount. Therefore, when the angular difference Δθ exceeds the first threshold value TH1 (refer to time t1), the angular difference Δθ is corrected, and the correction amount Q is set to a non-zero value. It is desirable that the larger the increase amount of the angular difference Δθ, the larger the correction amount Q is set. As an example, with k being a positive constant, the correction amount Q can be set to Q = k×θ. Thereby, the larger the angular difference Δθ, the larger the amount by which the angular difference Δθ is returned, so that the corrected angular difference Δθ becomes smaller. Therefore, excessive increase in the angular difference Δθ can be suppressed.

[0076] ≪Motor degradation detection≫ When the motor 3 deteriorates, the angular difference Δθ may increase compared to when the motor 3 has not deteriorated. More specifically, when the magnetic force of the permanent magnet of the rotor 301 decreases, the torque required for the rotation of the rotor 301 increases, making it difficult for the d-axis to rotate, so the angular difference Δθ may increase. Also, when the winding resistance of the coil in the stator 302 increases, the magnetic field generated by the stator 302 weakens, making it difficult for the d-axis to rotate, so the angular difference Δθ may increase.

[0077] The second threshold value TH2 is determined in advance, for example, based on the experimental results of comparing a deteriorated motor and a non-deteriorated motor. For example, the second threshold value TH2 is TH2 = 40°.

[0078] When the angular difference Δθ is equal to or less than the second threshold value TH2, it is determined that the motor 3 is not deteriorated. On the other hand, when the angular difference Δθ exceeds the second threshold value TH2, it is determined that the deterioration of the motor 3 has been detected. When the deterioration of the motor 3 is detected, it is desirable to notify the user of this fact or record and save it.

[0079] ≪Angular Acceleration Correction Control≫ FIG. 12 is a diagram for explaining the angular acceleration correction amount in the angular acceleration correction control. The horizontal axis represents the angular difference Δθ (more specifically, the angular difference after correction by the angular difference correction control). The vertical axis represents the correction amount α of the angular acceleration by the angular acceleration correction control.

[0080] If the angular difference Δθ further increases due to further progression of the deterioration of the motor 3 or the like, the possibility of the motor 3 losing synchronization increases. The angular acceleration correction control is a control for adjusting the angular acceleration by the correction amount α so that the angular difference Δθ approaches the third threshold value TH3 in order to prevent the motor 3 from losing synchronization. The corrected angular acceleration is described as (a + α). The correction amount α is a negative value, zero, or a positive value.

[0081] The third threshold value TH3 is set in advance according to the specifications of the motor 3 to a limit value at which the motor 3 may lose synchronization when the angular difference Δθ further increases. The third threshold value TH3 is, for example, TH3 = 60°.

[0082] As an example, the correction amount α of the angular acceleration is determined such that it is zero when the angular difference Δθ is equal to the third threshold value TH3, negative when the angular difference Δθ is greater than the third threshold value TH3, and positive when the angular difference Δθ is less than the third threshold value TH3, as shown in FIG. 12. Also, it is desirable that the correction amount α is determined such that the corrected angular acceleration does not fall below the guaranteed value (the minimum speed required to start the motor 3 within a predetermined time).

[0083] When the angular difference Δθ exceeds the third threshold TH3, angular acceleration correction control is started. When the angular difference Δθ exceeds the third threshold TH3, since the correction amount α is a negative value, the corrected angular acceleration (a + α) decreases compared to the angular acceleration before correction. On the other hand, when the angular difference Δθ is less than or equal to the third threshold TH3, since the correction amount α is a positive value, the corrected angular acceleration (a + α) increases compared to the angular acceleration before correction. As a result, the angular difference Δθ approaches the third threshold TH3, and it is suppressed that the angular difference Δθ greatly exceeds the third threshold TH3. Therefore, detuning of the motor 3 can be more reliably prevented.

[0084] <Functional block> FIG. 13 is a functional block diagram of the controller 22A in the second embodiment. The controller 22A is different from the controller 22 (see FIG. 6) in the first embodiment in that it further includes an angular difference correction unit 512, an angular acceleration correction unit 513, and a degradation detection unit 514.

[0085] The angular difference correction unit 512 receives the angular difference Δθ from the angular difference calculation unit 507. The angular difference correction unit 512 sets the correction amount Q to Q = 0 until the angular difference Δθ exceeds the first threshold TH1, and sets the correction amount Q to Q = k × Δθ when the angular difference Δθ exceeds the first threshold TH1 (see FIG. 11). The angular difference correction unit 512 outputs the corrected angular difference (Δθ - Q) to the subtraction unit 508 and also outputs it to the degradation detection unit 514.

[0086] The angular acceleration correction unit 513 receives, for example, an angular acceleration command a* from the main controller 4 (see FIG. 1). When the angular difference Δθ exceeds the third threshold TH3, the angular acceleration correction unit 513 starts angular acceleration correction control and sets a correction amount α of the angular acceleration according to the angular difference Δθ (see FIG. 12). The angular acceleration correction unit 513 outputs the corrected angular acceleration command (a* + α) to the angular velocity command generation unit 505.

[0087] The deterioration detection unit 514 receives the corrected angle difference (Δθ - Q) from the angle difference correction unit 512. When the corrected angle difference (Δθ - Q) is less than or equal to the second threshold value TH2, the deterioration detection unit 514 determines that the motor 3 has not deteriorated. When the angle difference Δθ exceeds the second threshold value TH2, the deterioration detection unit 514 determines that the deterioration of the motor 3 has been detected. When the deterioration detection unit 514 detects the deterioration of the motor 3, it notifies or records the fact externally. For example, when the motor system 100 is mounted on a vehicle, the deterioration detection unit 514 may turn on a warning light (not shown) or record the deterioration detection in a diagnostic (fault diagnosis function).

[0088] Since the functional blocks other than those described above are equivalent to the corresponding functional blocks in Embodiment 1, detailed descriptions will not be repeated.

[0089] As described above, in Embodiment 2, the controller 22A executes angle difference correction control, motor deterioration detection, and angular acceleration correction control. By the angle difference correction control, an excessive increase in the angle difference Δθ can be suppressed. By the motor deterioration detection, it becomes possible for the user to take appropriate measures with respect to the motor 3, such as requesting the administrator to repair or replace the motor 3. By the angular acceleration correction control, out-of-step of the motor 3 can be more reliably prevented. However, the controller 22A does not necessarily execute all of the above three controls. The controller 22A may execute at least one of the three controls, and may execute only one or two of the controls.

[0090] <Processing Flow> ≪Angle Difference Correction Control≫ FIG. 14 is a flowchart showing a processing procedure related to the angle difference correction control. The processing shown in this flowchart is executed when a predetermined condition is satisfied (for example, at a predetermined cycle). Each step is realized by software processing by the controller 22A, but may also be realized by hardware (electric circuit) arranged in the controller 22A. Hereinafter, steps are abbreviated as S. The same applies to the flowcharts of FIGS. 15 and 16 described later.

[0091] In S11, the controller 22A calculates the angle difference Δθ according to the above formula (11). As described above, the controller 22A may execute a series of processes based on the tan basis instead of the angle basis. In this case, the controller 22A calculates the angle difference tan(Δθ) according to the above formula (10).

[0092] In S12, the controller 22A determines whether the angle difference Δθ is greater than the first threshold value TH1. When the angle difference Δθ is greater than the first threshold value TH1 (YES in S12), the controller 22A sets the correction amount Q of the angle difference to Q = k × ΔQ (S13). On the other hand, when the angle difference Δθ is less than or equal to the first threshold value TH1 (NO in S12), the controller 22A sets the correction amount Q of the angle difference to Q = 0 (S14).

[0093] In S15, the controller 22A corrects the angle difference Δθ using the correction amount Q. Thereby, the motor 3 is started so that the corrected angle difference (Δθ - Q) is maintained constant.

[0094] ≪Motor deterioration detection≫ FIG. 15 is a flowchart showing a processing procedure related to motor deterioration detection. In S21, the controller 22A acquires the corrected angle difference (Δθ - Q) by angle difference correction control.

[0095] In S22, the controller 22A determines whether the corrected angle difference (Δθ - Q) is greater than the second threshold value TH2. When the corrected angle difference (Δθ - Q) is greater than the second threshold value TH2 (YES in S22), the controller 22A determines that the deterioration of the motor 3 has been detected (S23). Then, the controller 22A notifies the user that the deterioration of the motor 3 has been detected or records it in the memory 222 (S24). On the other hand, when the corrected angle difference (Δθ - Q) is less than or equal to the second threshold value TH2 (NO in S22), the controller 22A determines that the deterioration of the motor 3 is not detected (S25).

[0096] ≪Angular acceleration correction control≫ FIG. 16 is a flowchart showing a processing procedure related to angular acceleration correction control. In S31, the controller 22A acquires the corrected angular difference (Δθ-Q) by angular difference correction control.

[0097] In S32, the controller 22A determines whether the corrected angular difference (Δθ-Q) is greater than a third threshold value TH3. When the corrected angular difference (Δθ-Q) is greater than the third threshold value TH3 (YES in S32), the controller 22A proceeds to S33 and calculates a correction amount α of the angular acceleration according to the corrected angular difference (Δθ-Q) (see FIG. 12).

[0098] In S34, the controller 22A corrects the angular acceleration a using the correction amount α. Thereby, the motor 3 is started so that the corrected angular difference (Δθ-Q) by the angular difference correction control approaches the third threshold value TH3.

[0099] In S35, the controller 22A determines whether an end condition for ending the correction of the angular difference is satisfied. For example, when the start of the motor 3 is completed (when the motor 3 enters steady driving), the end condition is satisfied. When the end condition is not satisfied (NO in S35), the controller 22A returns the process to S33 and continues to correct the angular difference. When the end condition is satisfied (YES in S35), the controller 22A ends a series of processes and ends the correction of the angular difference.

[0100] Note that when the corrected angular difference (Δθ-Q) is equal to or less than the third threshold value TH3 (NO in S32), the processes of S33 to S35 are skipped and the correction of the angular acceleration is not started.

[0101] As described above, according to the second embodiment, similar to the first embodiment, the angular difference Δθ is maintained constant during the start-up of the motor 3. Thereby, while preventing the detuning of the motor 3, the motor 3 can be started promptly. In addition, in the second embodiment, angular difference correction control, motor deterioration detection, and angular acceleration correction control are executed. By the angular difference correction control, an excessive increase in the angular difference Δθ can be suppressed. By the motor deterioration detection, it becomes possible for the user to take appropriate measures against the deteriorated motor 3. By the angular acceleration correction control, the detuning of the motor 3 can be more reliably prevented.

[0102] <Supplementary Note> Finally, various aspects of the present invention will be collectively described as supplementary notes.

[0103] ≪Supplementary Note 1≫ A power conversion device for driving a motor including a rotor having a permanent magnet and a stator around which a coil is wound, A control device that executes sensorless control of the motor using the power conversion device, The control device, Starts the motor by accelerating the rotor by providing an angular difference between the d-axis in the d-q rotating coordinate system and the γ-axis estimating the d-axis, During the acceleration of the rotor, controls the power conversion device so that the d-axis current does not deviate from a certain range, the angular velocity of the rotor increases monotonically, and the angular difference is maintained within a defined range not including zero. A motor drive device.

[0104] ≪Supplementary Note 2≫ The control device controls the power conversion device so that the d-axis current is constant, the angular velocity increases at a constant rate, and the angular difference is maintained constant. The motor drive device according to Supplementary Note 1.

[0105] ≪Supplementary Note 3≫ The control device controls the angular difference according to the above formula (10) or formula (11), In the above formula (10) or the above formula (11), Δθ represents the angle difference, Vd represents the d-axis voltage, Vq represents the q-axis voltage, Id represents the d-axis current, Iq represents the q-axis current, R represents the winding resistance of the coil, ω represents the angular velocity, Ld represents the d-axis self-inductance of the coil, and Lq represents the q-axis self-inductance of the coil. The motor drive device according to Supplementary Note 1 or 2.

[0106] ≪Supplementary Note 4≫ When the angle difference exceeds a first threshold value during acceleration of the motor, the control device reduces the angle difference as compared with the case where the angle difference is below the first threshold value. The motor drive device according to any one of Supplementary Notes 1 to 3.

[0107] ≪Supplementary Note 5≫ When the angle difference is below the first threshold value, the control device does not reduce the angle difference. The motor drive device according to Supplementary Note 4.

[0108] ≪Supplementary Note 6≫ When the angle difference exceeds the first threshold value, the control device increases the amount of reduction of the angle difference as the angle difference becomes larger. The motor drive device according to Supplementary Note 4 or 5.

[0109] ≪Supplementary Note 7≫ When the angle difference exceeds a second threshold value during acceleration of the motor, the control device detects deterioration of the motor. The motor drive device according to any one of Supplementary Notes 1 to 6.

[0110] ≪Supplementary Note 8≫ When the deterioration of the motor is detected, the control device notifies the outside of the motor drive device of the deterioration of the motor. The motor drive device according to Supplementary Note 7.

[0111] ≪Supplementary Note 9≫ When the deterioration of the motor is detected, the control device records the deterioration of the motor in a memory. The motor drive device according to Supplementary Note 7 or 8.

[0112] ≪Supplementary Note 10≫ The control device calculates the angle difference based on the angular acceleration of the motor, and when the angle difference exceeds a third threshold value during acceleration of the motor, executes angular acceleration correction control for correcting the angular acceleration so that the angle difference approaches the third threshold value, the motor drive device according to any one of Appendices 1 to 9.

[0113] ≪Appendix 11≫ During execution of the angular acceleration correction control, the control device corrects the angular acceleration such that the angular acceleration decreases when the angle difference is greater than the third threshold value and the angular acceleration increases when the angle difference is greater than the third threshold value, the motor drive device according to Appendix 10.

[0114] ≪Appendix 12≫ A power conversion device that drives a motor including a rotor having a permanent magnet and a stator around which a coil is wound, and a control device that executes sensorless control of the motor using the power conversion device, wherein the control device decelerates the rotor by providing an angle difference between the d-axis in the d-q rotating coordinate system and the γ-axis obtained by estimating the d-axis, thereby stopping the motor, and controls the power conversion device such that during deceleration of the rotor, the d-axis current does not deviate from a certain range, the angular velocity of the rotor decreases monotonically, and the angle difference is maintained within a defined range that does not include zero, the motor drive device.

[0115] ≪Appendix 13≫ A motor drive device according to any one of Appendices 1 to 12, and the motor, a motor system.

[0116] ≪Appendix 14≫ A method for driving a motor including a rotor having a permanent magnet and a stator around which a coil is wound, Including a step of accelerating the rotor by providing an angular difference between the d-axis in the d-q rotating coordinate system and the γ-axis obtained by estimating the d-axis, and starting the motor, The step of starting the motor includes steps in which the d-axis current does not deviate from a certain range, the angular velocity of the rotor increases monotonically, and the angular difference is maintained within a defined range that does not include zero. A method for driving a motor.

[0117] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the description of the above embodiments but by the claims, and it is intended that all changes within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0118] 100 Motor system, 1 Power source, 11 Monitoring unit, 2 Motor drive device, 21 Power conversion device, 211 Converter, 212 Voltage sensor, 213 Inverter, 22, 22A Controller, 221 Processor, 222 Memory, 3 Motor, 301 Rotor, 302 Stator, 31, 32 Current sensors, 4 Main controller, 501 Current command generation unit, 502 Subtraction unit, 503 Subtraction unit, 504 Voltage command generation unit, 505 Angular velocity command generation unit, 506 Angle command generation unit, 507 Angular difference calculation unit, 508 Subtraction unit, 509 Coordinate conversion unit, 510 Switching signal generation unit, 511 Coordinate conversion unit, 512 Angular difference correction unit, 513 Angular acceleration correction unit, 514 Degradation detection unit, Q1 to Q6 Switching elements, D1 to D6 Freewheel diodes, NL, PL Power lines, Tn, Tp DC terminals, Tu, Tv, Tw AC terminals.

Claims

1. A power conversion device for driving a motor including a rotor having a permanent magnet and a stator around which a coil is wound, and a control device that performs sensorless control of the motor using the power conversion device, wherein the control device, starts the motor by accelerating the rotor by providing an angular difference between the d-axis in the d-q rotating coordinate system and the γ-axis on which the d-axis is estimated, and controls the power conversion device so that during the acceleration of the rotor, the d-axis current does not deviate from a certain range, the angular velocity of the rotor increases monotonically, and the angular difference is maintained within a defined range not including zero. A motor driving device.

2. The control device according to claim 1, wherein the control device controls the power conversion device so that the d-axis current is constant, the angular velocity increases at a constant rate, and the angular difference is maintained constant. Motor driving device.

3. The control device controls the angular difference according to the following formula (1), 【Number 1】 In the formula (1), Δθ represents the angular difference, Vd represents the d-axis voltage, Vq represents the q-axis voltage, Id represents the d-axis current, Iq represents the q-axis current, R represents the winding resistance of the coil, ω represents the angular velocity, Ld represents the d-axis self-inductance of the coil, and Lq represents the q-axis self-inductance of the coil. The motor driving device according to claim 1.

4. The control device according to any one of claims 1 to 3, wherein when the angular difference exceeds a first threshold during the acceleration of the motor, the control device reduces the angular difference compared to when the angular difference is below the first threshold. Motor driving device.

5. The control device according to claim 4, wherein when the angular difference is below the first threshold, the control device does not reduce the angular difference. Motor driving device.

6. The control device according to claim 4, wherein when the angular difference exceeds the first threshold, the greater the angular difference, the greater the amount of reduction of the angular difference. Motor driving device.

7. The control device according to any one of claims 1 to 3, wherein when the angular difference exceeds a second threshold during the acceleration of the motor, the control device detects degradation of the motor. Motor driving device.

8. The control device according to claim 7, wherein when degradation of the motor is detected, the control device notifies the degradation of the motor outside the motor driving device. Motor driving device.

9. The motor drive device according to claim 7, wherein when deterioration of the motor is detected, the control device records the deterioration of the motor in a memory.

10. The control device calculates the angle difference based on the angular acceleration of the motor, and when the angle difference exceeds a third threshold value during acceleration of the motor, executes angular acceleration correction control to correct the angular acceleration so that the angle difference approaches the third threshold value. The motor drive device according to any one of claims 1 to 3.

11. During execution of the angular acceleration correction control, the control device corrects the angular acceleration such that the angular acceleration decreases when the angle difference is greater than the third threshold value, and the angular acceleration increases when the angle difference is greater than the third threshold value. The motor drive device according to claim 10.

12. A power conversion device that drives a motor including a rotor having a permanent magnet and a stator around which a coil is wound, and a control device that executes sensorless control of the motor using the power conversion device, wherein the control device decelerates the rotor by providing an angle difference between the d-axis in the d-q rotating coordinate system and the γ-axis obtained by estimating the d-axis, and stops the motor, and controls the power conversion device such that during deceleration of the rotor, the d-axis current does not deviate from a certain range, the angular velocity of the rotor decreases monotonically, and the angle difference is maintained within a defined range that does not include zero. A motor drive device.

13. A motor system comprising the motor drive device according to claim 1 or 12, and the motor.

14. A method for driving a motor including a rotor having a permanent magnet and a stator around which a coil is wound, the method including a step of starting the motor by accelerating the rotor by providing an angle difference between the d-axis in the d-q rotating coordinate system and the γ-axis obtained by estimating the d-axis, wherein the step of starting the motor includes a step in which the d-axis current does not deviate from a certain range, the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a defined range that does not include zero. A method for driving a motor.

Images