Motor drive device, motor system, and motor drive method

Abstract

The invention provides a motor driving device, a motor system, and a motor driving method. A motor drive device (2) is provided with a power conversion device (21) and a controller (22). The power conversion device (21) drives an electric motor (3) including a rotor (301) having a permanent magnet and a stator (302) wound with a coil. The controller (22) performs sensorless control of the motor (3) using the power conversion device (21). The controller (22) starts the electric motor (3) by accelerating the rotor (301) by setting an angular difference between the d-axis and the gamma-axis, and controls the power conversion device (201) such that in the acceleration of the rotor (301), the d-axis current does not leave a fixed range, and the angular velocity of the rotor (301) monotonically rises, and the angular difference is maintained within a determined range that does not include zero.

Description

Technical Field

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

[0002] In the execution of sensorless control that drives the motor without using a position sensor to detect the position of the rotor, the motor may lose step. If the motor loses step, there is a possibility of excessive torque fluctuation, or the motor stops without starting normally. The electric power steering device disclosed in Japanese Patent Publication No. 2011-131725 detects the motor losing step that occurs during the execution of sensorless control.

[0003] In a motor drive device that performs sensorless control, there is a demand to quickly start and / or stop the motor depending on the purpose or condition of the motor. In order 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 step is higher than when the angular acceleration of the rotor is low. Summary of the invention

[0004] The present invention is made to solve the above-mentioned problems, and one object of the present invention is to prevent the motor from losing step and to start the motor quickly. Another object of the present invention is to prevent the motor from losing step and to stop the motor quickly.

[0005] (1) An electric motor drive device according to one aspect of the present invention comprises a power conversion device and a control device. The power conversion device drives an electric motor including a rotor having a permanent magnet and a stator wound with a coil. The control device performs sensorless control of the electric motor using the power conversion device. The control device accelerates the rotor and starts the electric motor by setting an angle difference between the d-axis in a dq rotating coordinate system and the γ-axis from which the d-axis is estimated. The control device controls the power conversion device so that during the acceleration of the rotor, the d-axis current does not deviate from a fixed range, the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a determined range that does not include zero.

[0006] In the structure of (1) above, the angle difference is maintained within a certain range, that is, the angle difference is stable. As a result, the motor is not easily out of step. Therefore, the angular acceleration can be set to a higher value, and the starting time of the motor can be shortened. Therefore, according to the structure of (1) above, the motor can be prevented from losing step, and the motor can be started quickly.

[0007] (2) Another aspect of the present invention relates to a motor drive device including 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 having a coil wound thereon. The control device performs sensorless control of the motor using the power conversion device. The control device decelerates the rotor and stops the motor by setting an angle difference between the d-axis in the dq rotating coordinate system and the γ-axis of the estimated d-axis. The control device controls the power conversion device so that during the deceleration of the rotor, the d-axis current does not deviate from a fixed range, the angular velocity of the rotor decreases monotonically, and the angle difference is maintained within a determined range that does not include zero.

[0008] In the structure of (2) above, the angle difference is maintained within a determined range, that is, the angle difference is stable. As a result, the motor is not easily out of step. Therefore, the angular acceleration can be set to a higher value, and the stopping time of the motor can be shortened. Therefore, according to the structure of (2) above, the motor can be prevented from losing step, and the motor can be stopped quickly.

[0009] (3) In another aspect of the present invention, a method for driving a motor includes a rotor having a permanent magnet and a stator wound with a coil. The method for driving the motor includes the step of accelerating the rotor and starting the motor by setting an angle difference between the d-axis in the dq rotating coordinate system and the γ-axis from which the d-axis is estimated. The step of starting the motor includes the steps of: the d-axis current does not deviate from a fixed range, the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a determined range that does not include zero.

[0010] According to the method of (3), similarly to the configuration of (1), the motor can be prevented from losing step and the motor can be started quickly.

[0011] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram showing the overall configuration of a motor system according to an embodiment of the present invention.

[0013] Figure 2 This is a diagram showing an example of the configuration of a motor system.

[0014] Figure 3 This is a diagram for explaining the relationship between the magnetic pole position of the rotor and the coordinate axis during the startup of the motor.

[0015] Figure 4 It is a timing chart showing the time change of each parameter at the time of starting the motor in the comparative example.

[0016] Figure 5 This is a timing chart showing the time changes of various parameters at the time of starting the electric motor in the first embodiment.

[0017] Figure 6 This is a functional block diagram of the controller in Implementation Example 1.

[0018] Figure 7 This is a diagram for explaining the relationship between the magnetic pole position of the rotor and the coordinate axis when the motor is stopped.

[0019] Figure 8 This is a conceptual diagram for explaining the angle difference during the start and stop of the motor.

[0020] Fig. 9 This is a timing chart showing the temporal changes of various parameters when the motor is stopped.

[0021] Fig.10 This is a conceptual diagram for explaining the execution conditions of the control in the second embodiment.

[0022] Fig.11 It is a timing chart for explaining the angle difference correction control.

[0023] Fig.12 It is a diagram for explaining the correction amount of angular acceleration in angular acceleration correction control.

[0024] Fig.13 This is a functional block diagram of the controller in Implementation Example 2.

[0025] Fig.14 This is a flowchart showing the processing steps related to the angle difference correction control.

[0026] Fig.15 This is a flowchart showing the processing steps related to motor degradation detection.

[0027] Fig.16 Detailed description of the process flow of the angular acceleration correction control. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0029] [Implementation Method 1]

[0030] <System Structure>

[0031] Figure 11 is a diagram showing the overall structure of a motor system according to an embodiment of the present invention. The motor system 100 is mounted on an electric vehicle, for example. However, the use of the motor system 100 is not limited to vehicles. The motor system 100 can also 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.

[0032] The power source 1 supplies electric power to the motor drive device 2. The power source 1 is, for example, a DC power source (DC system) such as a battery or a solar cell. The power source 1 may also be an AC power source (AC system).

[0033] The motor drive device 2 drives the motor 3. The motor drive device 2 includes: a power conversion device 21 that performs power conversion operation on the power supplied from the power source 1; and a controller 22 that controls the power conversion device 21 according to the 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 related to the angular acceleration of the motor 3) a*.

[0034] 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 performs sensorless control of the motor 3 .

[0035] Figure 2 FIG. 1 is a diagram showing an example of the structure of the motor system 100. Figure 2 The main controller 4 is omitted (refer to Figure 1 ) icon.

[0036] 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.

[0037] 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 a converter 211, a voltage sensor 212, and an inverter 213, for example.

[0038] Converter 211 is, for example, a chopper converter including one or more switching elements (not shown) and boosts the voltage of DC power from power source 1 in accordance with a control command from controller 22 and outputs the boosted DC power between power lines PL and NL.

[0039] Voltage sensor 212 detects the voltage between power line PL and power line NL, and outputs the detected voltage to controller 22 .

[0040] The inverter 213 is, for example, a 2-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 freewheeling diodes D1 to D6. Each switching element Q1 to Q6 is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), a bipolar transistor, etc. The freewheeling diodes D1 to D6 are connected in reverse parallel to the switching elements Q1 to Q6, respectively. The switching elements Q1 and Q2 are connected in series to form the U-phase arm of the full-bridge circuit. The switching elements Q3 and Q4 are connected in series to form the V-phase arm of the full-bridge circuit. The switching elements Q5 and Q6 are connected in series to form the W-phase arm of the full-bridge circuit. The U-phase arm, the V-phase arm, and the W-phase arm are connected to AC terminals Tu, Tv, and Tw, respectively. Each phase arm is connected between power line PL and power line NL.

[0041] The motor 3 is a permanent magnet synchronous motor including a rotor 301 having permanent magnets (see Figure 3 ) and a stator 302 wound with a coil. 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 connected to the neutral point in a star shape. 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.

[0042] The motor 3 is provided with current sensors 31 and 32. The current sensor 31 detects a V-phase current Iv flowing through the motor 3. The current sensor 32 detects a W-phase current Iw flowing through the motor 3. Each current sensor outputs the detected current to the controller 22.

[0043] The controller 22 controls the converter 211 and the inverter 213 based on the torque command Tr* and the angular acceleration command a* from the main controller 4 and the detection results of various sensors (monitoring unit 11, voltage sensor 212, current sensors 31, 32, etc.). For example, the controller 22 outputs a switching signal to one or more switching elements included in the converter 211, and outputs a switching signal SW to six switching elements Q1 to Q6 included in the inverter 213. The switching signal SW is typically a PWM (Pulse Width Modulation) signal.

[0044] The controller 22 includes a processor 221 and a memory 222 as main structural elements. The processor 221 includes processing circuits such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The memory 222 includes volatile storage devices such as DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory) and non-volatile storage devices such as HDD (Hard Disk Drive), SSD (Solid State Drive), and flash memory. The memory 222 stores system programs including an OS (Operating System), control programs including computer-readable codes, and various parameters for controlling the power conversion action of the power conversion device 21. The processor 221 reads out the system program, control program, and parameters, expands and executes them in the memory 222 to realize various calculation processes. The calculation processing of the controller 22 may also be realized by an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like.

[0045] The controller 22 of the motor drive device 2 and the main controller 4 do not necessarily have to be provided separately. The controller 22 may be configured to calculate the torque command Tr* and the angular acceleration command a* by itself.

[0046] <Calculation of angle difference>

[0047] The following description will be given assuming that the motor 3 in a stopped state is started.

[0048] Figure 3 3 is a diagram for explaining the relationship between the magnetic pole position of the rotor 301 and the coordinate axis during the startup of the motor 3. Figure 3 As shown, the d-axis is an 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 leading the d-axis by 90 degrees in electrical angle).

[0049] When the sensorless control of the motor 3 is performed, it is difficult for the controller 22 to accurately grasp the d-axis and the q-axis of the rotor 301. Therefore, a γ-δ rotating coordinate system is used instead of the dq rotating coordinate system defined by the d-axis and the q-axis. The γ-δ rotating coordinate system is defined by the γ-axis and the δ-axis which estimate the d-axis and the q-axis. The γ-axis is an axis 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 90 degrees ahead of the γ-axis in electrical angle).

[0050] The d-axis current and q-axis current in the γ-δ rotating coordinate system are recorded as Id and Iq, respectively. The d-axis current command and q-axis current command required to make the motor 3 generate a torque corresponding to the torque command Tr* are recorded as Id* and Iq*, respectively. The d-axis current Id is a current used to generate a magnetic field in the motor 3. The q-axis current Iq is a 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, thereby preventing the motor 3 from generating torque and generating a magnetic field at a specified position. Figure 3 In the example of FIG. 2 , 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 (generated magnetic field).

[0051] In the following, the angle difference between the γ-axis and the d-axis (the γ-δ rotating coordinate system and the dq rotating coordinate system) is recorded as "angle difference Δθ". Δθ can also be called "angle error" instead of the angle difference. The d-axis voltage, q-axis voltage, γ-axis voltage, and δ-axis voltage are recorded as Vd, Vq, Vγ, and Vδ, respectively. The winding resistance of the coil of the stator 302 is recorded as R. The d-axis self-inductance and q-axis self-inductance of the coil of the stator 302 are recorded as Ld and Lq, respectively. The back electromotive force constant of the motor 3 is recorded as Ke [V / rpm].

[0052] In the dq rotating coordinate system, the d-axis voltage Vd, the q-axis voltage Vq, the d-axis current Id, and the q-axis current Iq have the following relationships (1) and (2). In addition, for easy reading, the symbols (d, q, γ, δ) used to distinguish the axial directions of the voltage / current are used in the formulas.

[0053] [Mathematical formula 1]

[0054]

[0055] On the other hand, in the γ-δ rotating coordinate system, the γ-axis voltage Vγ and the δ-axis voltage Vδ are expressed as in the following equations (3) and (4). Here, it is assumed that Ld=Lq=L.

[0056] [Mathematical formula 2]

[0057]

[0058] The equations (3) and (4) are expressed in a matrix as shown in the following equation (5).

[0059] [Mathematical formula 3]

[0060]

[0061] The d-axis voltage Vd and the q-axis voltage Vq in the dq rotating coordinate system are obtained by rotating the γ-axis voltage Vγ and the δ-axis voltage Vδ in the γ-δ rotating coordinate system as expressed by the following equation (6).

[0062] [Formula 4]

[0063]

[0064] Substituting equation (5) into the right side of equation (6) and rearranging it, we obtain the following equations (7) and (8).

[0065] [Mathematical formula 5]

[0066]

[0067] Here, regarding the tangent (tan) of the angle difference Δθ, the following equation (9) always holds true.

[0068] [Mathematical formula 6]

[0069]

[0070] Therefore, from the equations (7) to (9), the angle difference Δθ is expressed as in the following equation (10).

[0071] [Formula 7]

[0072]

[0073] The formula (10) can also be expressed as the following formula (11).

[0074] [Mathematical formula 8]

[0075]

[0076] The control in this embodiment can be performed based on tan (Δθ) as in equation (10), or based on the angle difference Δθ [deg] as in equation (11). For convenience, an example of performing control based on the angle difference Δθ is described below. However, those skilled in the art can appropriately replace it with control based on tan (Δθ).

[0077] <Timing diagram>

[0078] 《Comparative Example》

[0079] In order to facilitate understanding of the control during motor startup in the present embodiment, the control during motor startup in a comparative example will first be described.

[0080] Figure 4 : is a timing chart showing the time variation of various parameters when the motor is started in the comparative example. The horizontal axis represents the elapsed time. The vertical axis represents 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] from top to bottom. Figure 5 The same is true in Chinese.

[0081] During the acceleration of the rotor, the d-axis current is controlled to be fixed so as not to deviate from the fixed range X. In addition, the angular acceleration command is also controlled to be fixed so as not to deviate from the fixed range Y. Therefore, the angular velocity command increases monotonically over time (in this example, it increases at a fixed rate). If the angular acceleration command is set low to prevent the motor from losing step, the start-up time of the motor will be longer. On the other hand, if the angular acceleration command is set high to shorten the start-up time of the motor, the rotation of the rotor does not follow the command, as shown in FIG. Figure 4 As shown in FIG. 1 , the actual angular acceleration and the actual angular velocity may vary with time. Therefore, the angle difference Δθ repeatedly increases and decreases. As a result, the motor 3 may lose step, especially when the angle difference Δθ increases.

[0082] <<Present Implementation Method>>

[0083] Figure 5 is a timing chart showing the time changes of various parameters when the motor 3 is started in the first embodiment. Figure 4 The timing chart in the comparative example shown is used for comparison.

[0084] like Figure 5As shown, in the present embodiment, in addition to controlling the d-axis current to be fixed so as not to deviate from the fixed range X, and controlling the angular acceleration command to be fixed so as not to deviate from the fixed range Y (thereby the angular velocity command monotonically increases over time), the angle difference Δθ is also maintained fixed. The angle difference Δθ being "fixed" includes a situation where the angle difference Δθ is strictly fixed to a target value, but is not limited to this, and means that the angle difference Δθ is within a range including the target value. In other words, the angle difference Δθ may also vary slightly within the range specified by the upper limit UL and the lower limit LL in the figure. By stabilizing the angle difference Δθ within this range, the motor 3 is less likely to lose step. Therefore, compared with the comparative example, the angular acceleration command can be set to a higher value, so the startup time of the motor 3 can be shortened. Therefore, according to the present embodiment, the motor 3 can be prevented from losing step, and the motor 3 can be started quickly.

[0085] <Function block>

[0086] Figure 6 Controller 22 is a functional block diagram of the controller 22 in Embodiment 1. Controller 22 includes a current command generating unit 501, subtraction units 502, 503, a voltage command generating unit 504, an angular velocity command generating unit 505, an angle command generating unit 506, an angle difference calculating unit 507, a subtraction unit 508, a coordinate conversion unit 509, a switch signal generating unit 510, and a coordinate conversion unit 511.

[0087] In this example, the current command generating unit 501 is from the main controller 4 (see Figure 1 ) receives the torque command Tr*. The current command generating unit 501 generates a d-axis current command Id* and a q-axis current command Iq* for causing the motor 3 to generate a torque corresponding to the torque command Tr* according to a pre-prepared map, table, etc. The current command generating unit 501 outputs the d-axis current command Id* and the q-axis current command Iq* to the subtraction units 502 and 503, respectively. In addition, the current command generating unit 501 outputs the d-axis current command Id* and the q-axis current command Iq* to the angle difference calculating unit 507.

[0088] 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.

[0089] 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.

[0090] In this example, the angular velocity command generating unit 505 is generated from the main controller 4 (see Figure 1 ) receives the angular acceleration instruction a*. The angular velocity instruction generation unit 505 calculates the angular velocity instruction ω* by performing a given operation (e.g., integration of the angular acceleration instruction a*) on the angular acceleration instruction a*. The angular velocity instruction generation unit 505 outputs the angular velocity instruction ω* to the angle instruction generation unit 506 and to the angle difference calculation unit 507.

[0091] 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 .

[0092] The angle difference calculation unit 507 receives the d-axis current command Id* and the q-axis current command Iq* from the current command generation unit 501, the d-axis voltage command Vd* and the 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 equation (11), and outputs the angle difference Δθ to the subtraction unit 508.

[0093] 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, in other words, the corrected angle command (θ*-Δθ) to the coordinate conversion units 509 and 511.

[0094] The coordinate conversion unit 509 converts the d-axis voltage command Vd* and the q-axis voltage command Vq* on the dq2-phase coordinates into the U-phase voltage command Vu*, the V-phase voltage command Vv*, and the W-phase voltage command Vw* on 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*, and Vw* in each phase to the switching signal generation unit 510.

[0095] The switching signal generating unit 510 generates the switching signal SW according to the voltage commands Vu*, Vv*, Vw* of each phase. More specifically, the switching signal generating 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. The switching signal generating unit 510 outputs the generated switching signal SW to the inverter 213 (see Figure 2 ).

[0096] The coordinate conversion unit 511 converts the angle command (θ*-Δθ) obtained by the current sensors 31 and 32 (see FIG. 1 ) according to a known coordinate conversion equation (UVW3-phase→dq2-phase conversion equation) using the corrected angle command (θ*-Δθ) obtained by the subtraction unit 508. Figure 2 ) The V-phase current Iv and the W-phase current Iw detected respectively are converted into the d-axis current Id and the q-axis current Iq. 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.

[0097] 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)). Since the angle difference Δθ is stable, the motor 3 is unlikely to lose step. Therefore, the angular acceleration a can be set to a high value without causing the motor 3 to lose step, and the start-up time of the motor 3 can be shortened. Therefore, according to the first embodiment, the motor 3 can be prevented from losing step, and the motor 3 can be started quickly.

[0098] [Modifications]

[0099] In the first embodiment, the control during the start-up of the motor 3 (when the rotor 301 is accelerated) is described. In this modification, the control during the stop of the motor 3 (when the rotor 301 is decelerated) is described.

[0100] Figure 7 3 is a diagram for explaining the relationship between the magnetic pole position of the rotor 301 and the coordinate axis when the motor 3 is stopped. Figure 3 for comparison. Figure 8: is a conceptual diagram for explaining the angle difference Δθ during the start and stop of the motor 3. Figure 7 as well as Figure 8 As shown, when the motor 3 is stopped, the angle difference Δθ is set to the opposite direction (the opposite direction to the angular velocity ω) to that when the motor 3 is started. The angle difference Δθ when the motor 3 is started is a positive value (Δθ>0), whereas the angle difference Δθ when the motor 3 is stopped is a negative value (Δθ<0).

[0101] Fig. 9 : is a timing chart showing the time variation of various parameters during the stop of the motor 3. Fig. 9 As shown, the angle difference Δθ is fixedly maintained at a negative value. As in the startup of the motor 3, the angle difference Δθ may slightly vary within the range defined by the upper limit UL and the lower limit LL. The angle difference Δθ is stable within this range, so that the motor 3 is unlikely to lose step.

[0102] In addition, the functional block diagram of the motor 3 when it is stopped and the functional block diagram of the motor 3 when it is started (refer to Figure 6 ) are the same, so the detailed description is not repeated.

[0103] As described above, in the modification of the first embodiment, although the sign of the angle difference Δθ is different, the angle difference Δθ is maintained constant as in the first embodiment. By stabilizing the angle difference Δθ, the angular acceleration a can be set to a high value without causing the motor 3 to lose step. As a result, the stop time of the motor 3 can be shortened. Therefore, according to the modification of the first embodiment, the motor 3 can be prevented from losing step and the motor 3 can be stopped quickly. For example, in the case where the motor 3 adopts an air bearing, by stopping the motor 3 quickly, the wear of the shaft (journal) and the receiving portion (sleeve) can be suppressed to a minimum.

[0104] [Implementation Method 2]

[0105] In Embodiment 2, a configuration for executing various additional controls based on the angle difference Δθ is described. In the following, for ease of understanding, the description is made assuming that the motor 3 is started, but similar controls can be executed even when the motor 3 is stopped.

[0106] In addition, the overall structure of the motor system in the second embodiment includes a controller 22A (see Fig.13 ) instead of the controller 22, the overall structure of the motor system 100 in the first embodiment (see Figure 1 as well as Figure 2 ) are the same, so they are not repeated.

[0107] <Execution conditions>

[0108] Fig.10 2 is a conceptual diagram for explaining the execution conditions of various controls in Embodiment 2. In Embodiment 2, Fig.10 As shown, three thresholds are set for the angle difference Δθ. The three thresholds are increased in the order of the first threshold TH1, the second threshold TH2, and the third threshold TH3. The angles in the figure and the specific numerical values ​​described below related to the thresholds are illustrative and are not limited to these.

[0109] The controller 22A is configured to perform angle difference correction control, motor degradation detection, and angular acceleration correction control according to the magnitude relationship with the three thresholds. More specifically, when the angle difference Δθ exceeds the first threshold TH1, the controller 22A performs angle difference correction control. When the angle difference Δθ exceeds the second threshold TH2, the controller 22A performs motor degradation detection. When the angle difference Δθ exceeds the third threshold TH3, the controller 22A performs angular acceleration correction control.

[0110] In addition, as in Fig.13 As described in , the motor degradation detection is performed when the angle difference after correction based on the angle difference correction control exceeds the second threshold value TH2. The angular acceleration correction control is performed when the angle difference after correction based on the angle difference correction control exceeds the third threshold value TH3. Figure 10 to Figure 12 In FIG. 1 , for simplicity, the angle difference after correction is replaced by the angle difference Δθ.

[0111] 《Angle difference correction control》

[0112] Fig.11 : is a timing 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.

[0113] The angle difference correction control is a control to reduce 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 to return the d-axis that is too far away from the γ-axis toward the γ-axis by the correction amount Q. The angle difference after correction is recorded as (Δθ-Q). The correction amount Q is 0 or a positive value.

[0114] The angle difference Δθ at the start of the motor 3 (reference time t0) is usually zero. After the motor 3 starts to start, the angle difference Δθ naturally increases as the angular velocity ω increases. It is not necessary to reduce the angle difference Δθ during this period. Therefore, when the angle difference Δθ is less than the first threshold value TH1, the angle difference Δθ is not corrected, and the correction amount Q is set to zero.

[0115] The first threshold TH1 is set in advance to a value that exceeds a normal increase in the angle difference Δθ accompanying an increase in the angular velocity ω, based on the specifications of the motor 3. The first threshold TH1 is, for example, TH1 = 20°.

[0116] The angle difference Δθ exceeding the first threshold value TH1 means that the angle difference Δθ increases beyond the usual increase amount. Therefore, when the angle difference Δθ exceeds the first threshold value TH1 (refer to time t1), the angle difference Δθ is corrected, and the correction amount Q is set to non-zero. Preferably, the larger the increase amount of the angle difference Δθ, the larger the correction amount Q is set. As an example, k is set to a positive constant, and the correction amount Q can be set to Q = k × θ. Thus, the larger the angle difference Δθ, the larger the return amount of the angle difference Δθ, and therefore the corrected angle difference Δθ becomes smaller. Therefore, the excessive increase of the angle difference Δθ can be suppressed.

[0117] 《Motor Deterioration Detection》

[0118] When the motor 3 is degraded, the angle difference Δθ increases compared to when the motor 3 is not degraded. More specifically, when the magnetic force of the permanent magnets of the rotor 301 decreases, the torque required for the rotation of the rotor 301 increases, and the d-axis becomes difficult to rotate, so the angle difference Δθ increases. In addition, when the winding resistance of the coil in the stator 302 increases, the magnetic field generated by the stator 302 weakens, and the d-axis becomes difficult to rotate, so the angle difference Δθ increases.

[0119] The second threshold value TH2 is determined in advance based on, for example, an experimental result of comparing a degraded motor with a non-degraded motor. The second threshold value TH2 is, for example, TH2 = 40°.

[0120] When the angle difference Δθ is less than the second threshold value TH2, it is determined that the motor 3 has not deteriorated. On the other hand, when the angle difference Δθ exceeds the second threshold value TH2, it is determined that the motor 3 has been deteriorated. When the deterioration of the motor 3 is detected, it is preferable to notify the user or record and retain the fact.

[0121] 《Angular acceleration correction control》

[0122] Fig.12 1 is a diagram for explaining the angular acceleration correction amount in the angular acceleration correction control. The horizontal axis represents the angle difference Δθ (more specifically, the angle difference after correction by the angle difference correction control). The vertical axis represents the angular acceleration correction amount α by the angular acceleration correction control.

[0123] If the angle difference Δθ increases further due to the further development of the deterioration of the motor 3, the possibility of the motor 3 losing step increases. The angular acceleration correction control refers to the control of adjusting the angular acceleration by the correction amount α so that the angle difference Δθ approaches the third threshold value TH3 in order to prevent the motor 3 from losing step. The corrected angular acceleration is recorded as (a+α). The correction amount α is a negative value, zero or a positive value.

[0124] The third threshold value TH3 is set in advance to a limit value at which the motor 3 will lose step if the angle difference Δθ further increases, according to the specification of the motor 3. The third threshold value TH3 is, for example, TH3 = 60°.

[0125] As an example, Fig.12 As shown, the correction amount α of the angular acceleration is determined to be zero when the angle difference Δθ is equal to the third threshold value TH3, to be a negative value when the angle difference Δθ is greater than the third threshold value TH3, and to be a positive value when the angle difference Δθ is smaller than the third threshold value TH3. In addition, the correction amount α is preferably determined so that the angular acceleration after correction does not fall below the guaranteed value (the minimum speed required to start the motor 3 within a given time).

[0126] If the angle difference Δθ exceeds the third threshold value TH3, the angular acceleration correction control is started. When the angle difference Δθ exceeds the third threshold value TH3, the correction amount α is a negative value, so the corrected angular acceleration (a+α) is lower than the angular acceleration before correction. On the other hand, when the angle difference Δθ is less than the third threshold value TH3, the correction amount α is a positive value, so the corrected angular acceleration (a+α) is higher than the angular acceleration before correction. As a result, the angle difference Δθ approaches the third threshold value TH3, and the angle difference Δθ is suppressed from exceeding the third threshold value TH3 significantly. Therefore, it is possible to more reliably prevent the motor 3 from losing steps.

[0127] <Function block>

[0128] Fig.13 22A is a functional block diagram of the controller 22A in the second embodiment. The controller 22A is different from the controller 22 in the first embodiment (see Figure 6 ) is different from the above in that it further includes an angle difference correction unit 512, an angular acceleration correction unit 513 and a degradation detection unit 514.

[0129] The angle difference correction unit 512 receives the angle difference Δθ from the angle difference calculation unit 507. The angle difference correction unit 512 sets the correction amount Q to Q=0 before the angle difference Δθ exceeds the first threshold value TH1, and sets the correction amount Q to Q=k×Δθ (see Fig.11 ). The angle difference correction unit 512 outputs the corrected angle difference (Δθ−Q) to the subtraction unit 508 and to the degradation detection unit 514 .

[0130] The angular acceleration correction unit 513 is, for example, from the main controller 4 (see Figure 1 ) receives the angular acceleration command a*. If the angle difference Δθ exceeds the third threshold value TH3, the angular acceleration correction unit 513 starts the angular acceleration correction control and sets the angular acceleration correction amount α corresponding to the angle difference Δθ (refer to Fig.12 ). The angular acceleration correction unit 513 outputs the corrected angular acceleration command (a*+α) to the angular velocity command generation unit 505 .

[0131] The degradation 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 the second threshold value TH2, the degradation detection unit 514 determines that the motor 3 is not degraded, and when the angle difference Δθ exceeds the second threshold value TH2, it determines that the degradation of the motor 3 is detected. When the degradation detection unit 514 detects the degradation of the motor 3, it notifies the external or records it. For example, when the motor system 100 is installed in a vehicle, the degradation detection unit 514 can light a warning lamp (not shown) or record the degradation detection in the diagnosis (fault diagnosis function).

[0132] Functional blocks other than those described above are the same as the corresponding functional blocks in Embodiment 1, and thus detailed descriptions thereof will not be repeated.

[0133] Thus, in Embodiment 2, the controller 22A performs angle difference correction control, motor degradation detection, and angular acceleration correction control. Through angle difference correction control, the excessive increase of the angle difference Δθ can be suppressed. Through motor degradation detection, the user can implement appropriate countermeasures for the motor 3, such as entrusting the manager to repair or replace the motor 3. Through angular acceleration correction control, the motor 3 can be more reliably prevented from losing step. However, the controller 22A may not perform all of the above three controls. The controller 22A only needs to perform at least one of the three controls, or may only perform any one or two of the controls.

[0134] <Processing Flow>

[0135] 《Angle difference correction control》

[0136] Fig.14 2 is a flowchart showing the processing steps related to the angle difference correction control. The processing shown in the flowchart is executed when a predetermined condition is met (for example, every predetermined cycle). Each step is implemented by software processing of the controller 22A, but can also be implemented by hardware (electrical circuit) configured in the controller 22A. Hereinafter, the step is abbreviated as S. Fig.15 as well as Fig.16 The flowchart is also the same.

[0137] In S11, the controller 22A calculates the angle difference Δθ according to the above equation (11). In addition, as described above, the controller 22A may perform a series of processes based on tan instead of angle. In this case, the controller 22A calculates the angle difference tan (Δθ) according to the above equation (10).

[0138] 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 the first threshold value TH1 (No in S12), the controller 22A sets the correction amount Q of the angle difference to Q=0 (S14).

[0139] In S15 , the controller 22A corrects the angle difference Δθ using the correction amount Q. Thus, the motor 3 is started so that the corrected angle difference (Δθ−Q) is maintained constant.

[0140] 《Motor Deterioration Detection》

[0141] Fig.15 2 is a flowchart showing a process procedure related to motor degradation detection. In S21 , the controller 22A obtains the angle difference (Δθ-Q) after correction by the angle difference correction control.

[0142] 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 is detected (S23). In addition, the controller 22A notifies the user of the detection of the deterioration of the motor 3 or records it in the memory 222 (S24). On the other hand, when the corrected angle difference (Δθ-Q) is less than the second threshold value TH2 (No in S22), the controller 22A determines that the deterioration of the motor 3 is not detected (S25).

[0143] 《Angular acceleration correction control》

[0144] Fig.16 2 is a flowchart showing a process procedure related to the angular acceleration correction control. In S31, the controller 22A obtains the angle difference (Δθ-Q) after correction by the angle difference correction control.

[0145] In S32, the controller 22A determines whether the corrected angular difference (Δθ-Q) is greater than the third threshold value TH3. If the corrected angular difference (Δθ-Q) is greater than the third threshold value TH3 (Yes in S32), the controller 22A causes the process to proceed to S33, and calculates the correction amount α of the angular acceleration based on the corrected angular difference (Δθ-Q) (refer to Fig.12 ).

[0146] In S34 , the controller 22A uses the correction amount α to correct the angular acceleration a. Thus, the motor 3 is started so that the angle difference (Δθ-Q) after correction based on the angle difference correction control approaches the third threshold value TH3 .

[0147] In S35, the controller 22A determines whether the end condition for ending the correction of the angle difference is satisfied. For example, the end condition is satisfied when the start of the motor 3 is completed (when the motor 3 enters the steady-state drive). If the end condition is not satisfied (No in S35), the controller 22A returns the process to S33 and continues the correction of the angle difference. If the end condition is satisfied (Yes in S35), the controller 22A ends a series of processes and ends the correction of the angle difference.

[0148] If the corrected angle difference (Δθ−Q) is equal to or smaller 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.

[0149] As described above, according to Embodiment 2, similarly to Embodiment 1, the angle difference Δθ is maintained fixed during the startup of the motor 3. Thus, the motor 3 can be prevented from losing step, and the motor 3 can be started quickly. In addition, in Embodiment 2, angle difference correction control, motor degradation detection, and angular acceleration correction control are performed. By the angle difference correction control, the excessive increase of the angle difference Δθ can be suppressed. By the motor degradation detection, the user can take appropriate measures against the degraded motor 3. By the angular acceleration correction control, the motor 3 can be prevented from losing step more reliably.

[0150] <Note>

[0151] Finally, each aspect of the present invention is described together as a supplementary note.

[0152] Appendix 1

[0153] A motor drive device comprises: a power conversion device that drives a motor including a rotor having permanent magnets and a stator wound with coils; and a control device that performs sensorless control of the motor using the power conversion device, the control device accelerating the rotor and starting the motor by setting an angle difference between the d-axis in a dq rotating coordinate system and the γ-axis from which the d-axis is estimated, the control device controlling the power conversion device so that during the acceleration of the rotor, the d-axis current does not deviate from a fixed range, the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a determined range that does not include zero.

[0154] Postscript 2

[0155] The motor drive device according to Supplementary Note 1, wherein the control device controls the power conversion device so that the d-axis current is fixed, the angular velocity increases at a fixed rate, and the angle difference is maintained fixed.

[0156] Note 3

[0157] An electric motor drive device according to Note 1 or 2, wherein the control device controls the angle difference according to the above-mentioned formula (10) or formula (11), in which 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.

[0158] Note 4

[0159] The motor drive device according to any one of Supplementary Notes 1 to 3, wherein when the angle difference exceeds a first threshold value during acceleration of the motor, the control device reduces the angle difference compared to a case where the angle difference is less than the first threshold value.

[0160] Appendix 5

[0161] The motor drive device according to Supplementary Note 4, wherein when the angle difference is lower than the first threshold value, the control device does not reduce the angle difference.

[0162] Appendix 6

[0163] The motor drive device according to Supplement 4 or 5, wherein 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 increases.

[0164] Appendix 7

[0165] The motor drive device according to any one of Supplementary Notes 1 to 6, wherein the control device detects degradation of the motor when the angle difference exceeds a second threshold value during acceleration of the motor.

[0166] Postscript 8

[0167] The motor drive device according to Supplementary Note 7, wherein the control device, when detecting the deterioration of the motor, notifies the outside of the motor drive device of the deterioration of the motor.

[0168] Appendix 9

[0169] The motor drive device according to Supplementary Note 7 or 8, wherein the control device records the degradation of the motor in a memory when the degradation of the motor is detected.

[0170] Appendix 10

[0171] An electric motor drive device according to any one of Notes 1 to 9, wherein the control device calculates the angle difference based on the angular acceleration of the electric motor, and when the angle difference exceeds a third threshold value during acceleration of the electric motor, performs angular acceleration correction control to correct the angular acceleration so that the angle difference approaches the third threshold value.

[0172] Appendix 11

[0173] According to the motor drive device described in Note 10, wherein the control device corrects the angular acceleration during the execution of the angular acceleration correction control so that the angular acceleration decreases when the angle difference is greater than the third threshold value, and increases when the angle difference is less than the third threshold value.

[0174] Appendix 12

[0175] A motor drive device comprises: a power conversion device that drives a motor including a rotor having permanent magnets and a stator wound with coils; and a control device that performs sensorless control of the motor using the power conversion device, the control device decelerating the rotor and stopping the motor by setting an angle difference between the d-axis in a dq rotating coordinate system and the γ-axis from which the d-axis is estimated, the control device controlling the power conversion device so that during the deceleration of the rotor, the d-axis current does not deviate from a fixed range, the angular velocity of the rotor decreases monotonically, and the angle difference is maintained within a determined range that does not include zero.

[0176] Appendix 13

[0177] A motor system comprises: the motor drive device according to any one of Supplementary Notes 1 to 12; and the motor.

[0178] Appendix 14

[0179] A method for driving an electric motor, the electric motor comprising a rotor having a permanent magnet and a stator wound with a coil, the method comprising the step of accelerating the rotor and starting the motor by setting an angle difference between a d-axis in a dq rotating coordinate system and a γ-axis from which the d-axis is estimated, the step of starting the motor comprising the steps of: the d-axis current does not deviate from a fixed range, the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a determined range that does not include zero.

[0180] Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A motor drive device, characterized in that: have: 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 for performing sensorless control of the electric motor using the power conversion device, The control device accelerates the rotor to start the motor by providing an angle difference between the d-axis in the dq rotating coordinate system and the γ-axis from which the d-axis is estimated. The control device controls the power conversion device so that, in acceleration of the rotor, the d-axis current does not deviate from a fixed range, the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a determined range not including zero.

2. The motor drive 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 angle difference is maintained constant.

3. The motor drive device according to claim 1 or 2, wherein: The control device controls the angle difference according to the following formula (1): [Mathematical formula 1] In the formula (1), 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.

4. The motor drive device according to any one of claims 1 to 3, wherein: When the angle difference exceeds a first threshold value during acceleration of the electric motor, the control device reduces the angle difference compared to a case where the angle difference is lower than the first threshold value.

5. The motor drive device according to claim 4, wherein: When the angle difference is lower than the first threshold, the control device does not reduce the angle difference.

6. The motor drive device according to claim 4 or 5, wherein: 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 increases.

7. The motor drive device according to any one of claims 1 to 6, wherein: The control device detects degradation of the electric motor when the angle difference exceeds a second threshold value during acceleration of the electric motor.

8. The motor drive device according to claim 7, wherein: When the control device detects the deterioration of the electric motor, it notifies the outside of the electric motor drive device of the deterioration of the electric motor.

9. The motor drive device according to claim 7 or 8, wherein: The control device records the deterioration of the motor in a memory when deterioration of the motor is detected.

10. The motor drive device according to any one of claims 1 to 9, wherein: The control device calculates the angle difference based on the angular acceleration of the motor, When the angle difference exceeds a third threshold value during acceleration of the electric motor, the control device performs angular acceleration correction control for correcting the angular acceleration so that the angle difference approaches the third threshold value.

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

12. A motor driving device, characterized in that: have: 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 for performing sensorless control of the electric motor using the power conversion device, The control device decelerates the rotor and stops the motor by providing an angle difference between the d-axis in the dq rotating coordinate system and the γ-axis from which the d-axis is estimated. The control device controls the power conversion device so that, in deceleration of the rotor, the d-axis current does not deviate from a fixed range, the angular velocity of the rotor decreases monotonically, and the angle difference is maintained within a determined range not including zero.

13. A motor system, characterized in that: have: The motor drive device according to any one of claims 1 to 12; and The electric motor.

14. A method for driving an electric motor, the electric motor comprising a rotor having a permanent magnet and a stator wound with a coil, characterized in that: The method for driving the electric motor includes the steps of accelerating the rotor and starting the electric motor by providing an angle difference between a d-axis in a dq rotating coordinate system and a γ-axis from which the d-axis is estimated, The step of starting the motor includes the steps of: the d-axis current does not deviate from a fixed range, and the angular velocity of the rotor increases monotonically, and the angle difference is maintained within a determined range that does not include zero.

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