MOTOR CONTROL DEVICE, PROGRAM, AND MOTOR CONTROL METHOD

Abstract

To provide a motor control device and a program for increasing the upper limit speed of a rotor as much as possible when temperature of a permanent magnet is low.SOLUTION: A motor control device 40 is applied to a system having a motor 50 having a stator with coils and a rotor with permanent magnets, and an inverter 30 connected to the coils. The motor control device 40 rotates the rotor by applying current to the coils of the stator under the control of an inverter 30. A determination unit 42 of the motor control device 40 determines whether or not the temperature of the permanent magnet of the rotor is lower than a threshold value. A control unit 43 of the motor control device 40 performs changing processing of control mode of the inverter 30 in order to increase the upper limit rotation speed of the rotor under a condition that the temperature of the permanent magnet of the rotor is determined to be lower than the threshold value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a motor control device. , program and motor control method Regarding. [Background technology]

[0002] The motor described in Patent Document 1 and the like has a stator with a coil and a rotor with a permanent magnet, and the rotor is rotated by magnetic flux generated by a current flowing through the coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4730420 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, motors heat up when a current flows through the coil, and are therefore designed on the assumption that the motor will be operated at temperatures around or higher than room temperature. However, for example, in cold regions, the motor may be operated at low temperatures immediately after starting.

[0005] However, the characteristics of permanent magnet motors change with temperature, and at low temperatures, the magnetic force of the permanent magnets becomes stronger, resulting in greater torque. On the other hand, as the magnetic force of the permanent magnets becomes stronger, the back electromotive force at the same rotation speed also increases, resulting in a lower upper limit rotation speed. As a result, although the motor's torque increases at low temperatures, the upper limit rotation speed of the rotor decreases.

[0006] The present invention has been made in consideration of the above circumstances, and has as its main object to make it possible to maximize the upper limit rotation speed of a motor when the permanent magnet is at a low temperature. [Means for solving the problem]

[0007] The motor control device of the present invention is applied to a system including a motor having a stator with a coil and a rotor with a permanent magnet, and an inverter connected to the coil, and rotates the rotor by passing a current through the coil by controlling the inverter. The motor control device includes a determination unit that determines whether or not a temperature of the permanent magnet is lower than a threshold value, and a control unit that performs processing to change the control mode of the inverter in order to increase the upper limit rotation speed of the rotor on condition that it is determined that the temperature of the permanent magnet is lower than the threshold value.

[0008] The present invention performs a process of changing the control mode of the inverter in order to increase the upper limit rotation speed of the rotor on condition that the temperature of the permanent magnet is determined to be lower than a threshold value, and therefore, when the permanent magnet is at a low temperature, it is possible to maximize the upper limit rotation speed of the motor. [Brief description of the drawings]

[0009] [Figure 1] 1 is a circuit diagram showing a motor control device and its periphery according to a first embodiment. [Diagram 2] FIG. 4 is a block diagram showing processing by the motor control device. [Diagram 3] 4 is a time chart showing transitions of a carrier signal and a switch drive signal. [Figure 4] 4 is a timing chart showing changes in current flowing through upper and lower arm switches. [Diagram 5] FIG. 2 is a diagram showing an operating region of a motor defined by rotational speed and torque. [Figure 6] 4 is a flowchart showing control by the motor control device. [Figure 7] 6 is a time chart showing transitions of a carrier signal and a switch drive signal after a frequency reduction process is performed. [Figure 8] 6 is a time chart showing changes in current flowing through upper and lower arm switches after a length reduction process is performed. [Figure 9] 11A and 11B are diagrams showing the operating regions of the motor before and after a rate reduction process is performed. [Figure 10] 10 is a graph showing a transition of a current of a predetermined phase before and after a ripple increasing process is performed in the second embodiment. [Figure 11] 6A and 6B are diagrams showing dq-axis currents before and after a current increasing process is performed. [Figure 12] FIG. 4 is a diagram showing the operating regions of the motor before and after a magnet heating treatment is performed. [Figure 13] 13 is a time chart showing changes in temperature, etc. of the upper and lower arm switches in the third embodiment. [Figure 14] FIG. 13 is a block diagram showing a process performed by a motor control device in a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and can be appropriately modified and implemented without departing from the spirit and scope of the invention.

[0011] [First embodiment] 1 is a circuit diagram showing a motor control device 40 and its periphery according to a first embodiment. The motor control device 40 is applied to a system having a motor 50 and an inverter 30. The motor 50 has a stator 51 and a rotor 56. The motor 50 is a synchronous motor, and the rotor 56 has a permanent magnet 57.

[0012] The stator 51 has a U-phase coil cU, a V-phase coil cV, and a W-phase coil cW as three-phase coils. One end of the U-phase coil cU, one end of the V-phase coil cV, and one end of the W-phase coil cW are connected to each other at a neutral point. That is, the three-phase coils are star-connected. However, instead of this, for example, they may be delta-connected.

[0013] For the motor 50, a temperature sensor 52 that detects the “coil temperature”, which is the temperature of at least one of the coils cU, cV, cW of each phase, and a rotation angle sensor 53 that detects the rotation angle of the rotor 56 are provided.

[0014] The inverter 30 is connected to the battery 20, the smoothing capacitor 27, and the three-phase coil. The battery 20 has a series connection of cell batteries 22 such as lithium ion batteries. The inverter 30 has an upper arm switch s1 and a lower arm switch s2 for each phase.

[0015] The upper and lower arm switches s1 and s2 in each phase are semiconductor switches such as IGBTs, MOSFETs, bipolar transistors, etc., and have a positive terminal, a negative terminal, and a control terminal. In the figure, the semiconductor switches are N-channel IGBTs, the positive terminal is the collector terminal, the negative terminal is the emitter terminal, and the control terminal is the gate terminal. A freewheel diode 33 is connected in inverse parallel to each of the arm switches s1 and s2. A drive circuit 34 is connected to the control terminal of each of the arm switches s1 and s2.

[0016] The positive terminal of the upper arm switch s1 of each phase is connected via a positive wiring Lp to the positive terminal of the battery 20 and the positive terminal of the smoothing capacitor 27. The negative terminal of the lower arm switch s2 of each phase is connected via a negative wiring Ln to the negative terminal of the battery 20 and the negative terminal of the smoothing capacitor 27.

[0017] The negative terminal of the U-phase upper arm switch s1 and the positive terminal of the U-phase lower arm switch s2 are connected to an end of the U-phase coil cU opposite to the neutral point via a U-phase wiring Lu. The negative terminal of the V-phase upper arm switch s1 and the positive terminal of the V-phase lower arm switch s2 are connected to an end of the U-phase coil cU opposite to the neutral point via a V-phase wiring Lv. The negative terminal of the W-phase upper arm switch s1 and the positive terminal of the W-phase lower arm switch s2 are connected to an end of the W-phase coil cW opposite to the neutral point via a W-phase wiring Lw. With the above configuration, the upper arm switch s1 and the lower arm switch s2 of the same phase are connected in series with each other.

[0018] A current sensor 39 for detecting a current value in each of the phase wirings Lu, Lv, Lw is provided for the inverter 30. The current sensor 39 detects a current flowing in at least two phase wirings among the phase wirings Lu, Lv, Lw.

[0019] The motor control device 40 controls the inverter 30 by transmitting commands to the drive circuits 34 of the respective phases to control the arm switches s1, s2 of the respective phases. As a result, a three-phase AC current is caused to flow through the three-phase coils to rotate the rotor 56.

[0020] The motor control device 40 is mainly composed of a microcomputer, and the microcomputer has a CPU. The functions provided by the microcomputer can be provided by software recorded in a physical memory device and a computer that executes the software, by software alone, by hardware alone, or by a combination of these. For example, when the microcomputer is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a large number of logic circuits, or an analog circuit. For example, the microcomputer executes a program such as that shown in FIG. 6 that is stored in a non-transitory tangible storage medium as a storage unit that the microcomputer has. By executing the program, a method corresponding to the program is executed. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated, for example, via a network such as the Internet.

[0021] 2 is a block diagram showing the processing of the motor control device 40. The motor control device 40 has a control unit 43. The control unit 43 controls each arm switch s1, s2 by controlling each drive circuit 34 with a drive signal, and passes a three-phase AC current through the inverter 30. Specifically, the control unit 43 receives drive commands such as a torque command value transmitted from a higher-level ECU or the like, current information from the current sensor 39, and rotation angle information from the rotation angle sensor 53, and calculates a voltage command value V* for each phase based on the received drive command, current information, and rotation angle information. The voltage command values ​​V* for each phase are shifted by 120 degrees in electrical angle. Note that a method for calculating the voltage command value V* may be a known one, and therefore a detailed description thereof will be omitted.

[0022] FIG. 3(a) is a time chart showing the transitions of the carrier signal Z and the voltage command value V*. FIGS. 3(b) and 3(c) are time charts showing the transitions of the drive signals for the upper and lower arm switches s1 and s2. The carrier signal Z in this embodiment is a triangular wave signal with equal increasing and decreasing speeds. Note that FIG. 3 shows the transitions of each signal over a very short period of time. For this reason, although the voltage command value V* is constant in FIG. 3, the voltage command value V* transitions in a sinusoidal manner.

[0023] The control unit 43 alternates between a "first state" and a "second state" based on the magnitude relationship between the carrier signal Z and the voltage command value *V. The first state is a state in which the command for the upper arm switch s1 is an ON command, and the command for the lower arm switch s2 is an OFF command. The second state is a state in which the command for the upper arm switch s1 is an OFF command, and the command for the lower arm switch s2 is an ON command. Specifically, the control unit 43 switches to the first state when the voltage command value *V is greater than the carrier signal Z, and switches to the second state when the voltage command value *V is smaller than the carrier signal Z.

[0024] Between the period Pt1 of the first state and the period Pt2 of the second state, there is provided a "dead time Dt" for setting the command to the upper arm switch s1 and the lower arm switch s2 to an OFF command. Without the dead time Dt, a delay in the response of the switching state to the OFF command to the upper arm switch s1 and the lower arm switch s2 would cause the upper and lower arm switches s1 and s2 of the same phase to be turned ON simultaneously, causing the positive wiring Lp to be short-circuited to the negative wiring Ln.

[0025] 4 is a time chart showing the transition of the current flowing through the upper and lower arm switches s1 and s2. The dead time Dt (=D1) is set to a value within a range in which no current flows through the upper and lower arm switches s1 and s2 at the same time.

[0026] Next, the problem to be solved by this embodiment will be described with reference to FIG. 5. FIG. 5 is a diagram showing the operating region of the motor 50 defined by the rotation speed and torque. The permanent magnet type motor 50 has characteristics that change with temperature, and in a low temperature state compared to a normal temperature state, the magnetic force of the permanent magnet 57 becomes stronger, so the torque becomes larger. On the other hand, when the magnetic force of the permanent magnet 57 becomes stronger, the back electromotive force at the same rotation speed becomes higher, so the upper limit rotation speed becomes lower. Therefore, although the torque of the motor 50 becomes larger in a low temperature state compared to a normal temperature state, the upper limit rotation speed of the rotor 56 becomes lower. Therefore, in a low temperature state, the motor 50 cannot operate in the high-speed rotation range indicated by the diagonal lines in FIG. 5. As a result, the upper limit output of the motor 50 becomes smaller in a low temperature state compared to a normal temperature state.

[0027] Next, a configuration for solving the problems described above will be described. As shown in Fig. 2, a motor control device 40 has a temperature calculation unit 41 and a determination unit 42. The temperature calculation unit 41 stores, for example, a map or formula information showing the relationship between the coil temperature and the magnet temperature in a storage unit such as a non-volatile memory, and calculates the magnet temperature based on the map or formula and the coil temperature detected by a temperature sensor 52. Also, for example, the temperature calculation unit 41 may calculate the detected coil temperature as the magnet temperature.

[0028] The determination unit 42 performs a temperature determination as to whether or not the calculated magnet temperature is lower than a threshold value, and transmits an output expansion signal to the control unit 43 on condition that it is determined that the magnet temperature is lower than the threshold value. On condition that the control unit 43 receives the output expansion signal, it performs an "output expansion process" as a process for changing the control mode of the inverter 30 to increase the upper limit rotation speed of the rotor 56. In other words, the control unit 43 performs output expansion control on condition that it is determined that the magnet temperature is lower than the threshold value. The threshold value here is, for example, a value that can determine whether or not the area is a cold region.

[0029] 6 is a flowchart showing the control performed by motor control device 40. This flow is repeatedly performed, for example, at predetermined intervals while motor 50 is in operation.

[0030] First, the magnet temperature is calculated based on the coil temperature (S11). Next, it is determined whether the calculated magnet temperature is lower than a threshold value (S12). If it is determined that the magnet temperature is lower than the threshold value (S12: YES), the output expansion process is performed (S13), and the flow ends. On the other hand, if it is determined in S12 that the magnet temperature is higher than the threshold value (S12: NO), normal control is performed without performing the output expansion process (S14), and the flow ends.

[0031] Next, the output expansion process performed in S13 will be described. In this embodiment, as the output expansion control, a "ratio reduction process" is performed to reduce the "dead time ratio", which is the ratio of the dead time Dt in one switching period St of the upper and lower arm switches s1 and s2. The ratio reduction process includes at least one of the "frequency reduction process" and the "length reduction process" described below.

[0032] FIG. 7(a) is a time chart showing the transition of the carrier signal Z and the voltage command value V* after the frequency reduction process is performed. FIGS. 7(b) and (c) are time charts showing the transition of the drive signals for the upper and lower arm switches s1 and s2 after the frequency reduction process is performed. The frequency reduction process is a process of reducing the dead time ratio by increasing the switching period St by decreasing the frequency of the carrier signal Z and decreasing the frequency at which the dead time Dt occurs, as compared to the normal control shown in FIG. 3.

[0033] Specifically, for example, the control unit 43 stores map or mathematical formula information indicating the relationship between the magnet temperature and the carrier frequency in a storage unit such as a non-volatile memory, and in the frequency reduction process, sets the carrier frequency based on the map or mathematical formula and the magnet temperature calculated by the temperature calculation unit 41. More specifically, for example, the control unit 43 sets the carrier frequency lower as the calculated magnet temperature is lower.

[0034] FIG. 8 is a time chart showing the transition of the current flowing through the upper and lower arm switches s1 and s2 after the length reduction process is performed. Here too, similar to the case of normal control shown in FIG. 4, a dead time Dt (D2) is required such that the upper and lower arm switches s1 and s2 do not turn on simultaneously. However, the arm switches s1 and s2 respond faster to commands as the temperature decreases. Therefore, in the length reduction process, based on the "switch temperature" which is the temperature of the arm switches s1 and s2, within the range where the upper and lower arm switches s1 and s2 do not turn on simultaneously, the length of each dead time Dt is shortened (D2 < D1), thereby reducing the dead time ratio.

[0035] Specifically, for example, the control unit 43 stores map or mathematical formula information indicating the relationship between the switch temperature and the length of the dead time Dt in a storage unit such as a non-volatile memory, and in the length reduction process, sets the length of each dead time Dt based on the map or mathematical formula and the acquired switch temperature. More specifically, for example, the control unit 43 sets the length of each dead time Dt shorter as the acquired switch temperature is lower.

[0036] The switch temperature may be obtained by directly detecting the temperatures of the arm switches s1 and s2, or may be estimated from the ambient temperature and temperature gradient of the arm switches s1 and s2. For example, the switch temperature may be estimated from the estimated initial temperature of the arm switches s1 and s2 and the temperature rise of the arm switches s1 and s2 estimated from the power integration value or the like.

[0037] Fig. 9 is a diagram showing the operating region of the motor 50 before and after the ratio reduction process, which includes at least one of the frequency reduction process and the length reduction process described above. When the ratio reduction process is performed from the state before the ratio reduction process shown by the dashed line in Fig. 9, the dead time ratio becomes smaller, and the voltage utilization rate increases. This causes the upper limit rotation speed of the rotor 56 to increase, as shown by the solid line in Fig. 9. This causes the upper limit output of the motor 50 to increase.

[0038] The effects of this embodiment are summarized below. In this embodiment, the control unit 43 performs a ratio reduction process including at least one of a frequency reduction process and a length reduction process on the condition that the magnet temperature is determined to be lower than the threshold value, thereby reducing the dead time ratio. This increases the voltage utilization rate and increases the upper limit rotation speed of the rotor 56. Therefore, when the permanent magnet 57 is in a low temperature state, the upper limit output of the motor 50 can be increased as much as possible. Moreover, since the ratio reduction process can be performed simply by changing the control mode of the inverter 30, there is no need to change components such as the inverter 30 and the motor 50. Therefore, an increase in costs can be suppressed.

[0039] More specifically, in the frequency reduction process, the control unit 43 reduces the frequency of the dead time Dt and reduces the dead time ratio by lowering the frequency of the carrier signal Z. This increases the voltage utilization rate and makes it possible to increase the upper limit rotation speed of the motor 50.

[0040] In the length reduction process, the control unit 43 reduces the dead time ratio by shortening the length of each dead time Dt, taking advantage of the fact that the dead time Dt can be short when the arm switches s1 and s2 are in a low temperature state. This increases the voltage utilization rate, and makes it possible to increase the upper limit rotation speed of the motor 50.

[0041] Furthermore, the temperature calculation unit 41 calculates the magnet temperature from the coil temperature, and the determination unit 42 determines whether the calculated magnet temperature is lower than a threshold value or not. Therefore, even if the temperature of the rotating permanent magnet 57 is not directly measured, it is possible to determine whether the magnet temperature is lower than a threshold value or not based on the coil temperature.

[0042] The motor control device 40 of the present embodiment is particularly effective when there is a particularly high demand for increasing the upper limit rotation speed of the rotor 56. Specifically, for example, in a direct drive motor that does not use a reducer, the rotation speed is lower and the electrical angle frequency is lower than in a motor that uses a reducer. Furthermore, when ATC (Angle Triggered Control), which is rotor control based on the rotor rotation angle as described in JP 2017-153249 A, is not performed, there is a high demand for increasing the electrical angle frequency for rotor control, and there is a high demand for increasing the upper limit rotation speed. In this way, the motor control device 40 of the present embodiment is particularly effective when there is a particularly high demand for increasing the upper limit rotation speed of the rotor 56, for example, when the motor is a direct drive and ATC is not performed.

[0043] [Second embodiment] Next, a second embodiment will be described. In the following embodiments, the same reference numerals will be used for the same or corresponding components as those in the previous embodiments. The following embodiments will be described based on the first embodiment, focusing on the differences, and descriptions of the same or similar parts as the first embodiment will be omitted as appropriate.

[0044] In this embodiment, as the output expansion control, a "magnet heating process" is performed to increase the heating degree of the permanent magnet 57 by changing the control mode of the inverter 30. This increases the magnet temperature and weakens the magnetic force of the permanent magnet 57, thereby suppressing the back electromotive force and enabling operation in the high speed rotation range. The magnet heating process includes at least one of the "ripple increase process" and "current increase process" described below.

[0045] Fig. 10 is a time chart showing the transition of the current of a predetermined phase such as the U phase before and after the ripple increasing process is performed. The dashed line in the enlarged view of Fig. 10 shows the current when the increase or decrease in the current due to the ripple is eliminated and averaged. The ripple increasing process is a process in which the frequency of the carrier signal Z is lowered compared to before the ripple increasing process to increase the amplitude of the ripple current flowing through the three-phase coils, thereby increasing the iron loss due to the ripple current and increasing the degree of heating of the permanent magnet 57.

[0046] Specifically, for example, the control unit 43 stores a map or formula information indicating the relationship between magnet temperature and carrier frequency in a storage unit such as a non-volatile memory, and in the ripple increasing process, sets the carrier frequency based on the map or formula and the magnet temperature calculated by the temperature calculation unit 41. More specifically, for example, the control unit 43 sets the carrier frequency lower as the calculated magnet temperature is lower.

[0047] 11 is a diagram showing the dq-axis currents before and after the current increase process is performed. The current increase process is a process in which the torque output by the motor is kept the same before and after the current increase process by changing the dq-axis currents flowing through the three-phase coils, and the magnitude of the current vector flowing through the three-phase coils is increased, thereby increasing the degree of heating of the permanent magnets 57. That is, in the current increase process, the control unit 43 intentionally changes the d-axis current and q-axis current to a ratio that is less efficient when outputting the same torque as before the current increase process. Thereby, the magnitude of the current vector is intentionally made larger than before the change, and the current flowing through the three-phase coils is increased.

[0048] Specifically, for example, the control unit 43 stores a map or formula information showing the relationship between the magnet temperature and the magnitude of the current vector in a storage unit such as a non-volatile memory, and in the current increasing process, calculates the magnitude of the current vector based on the map or formula and the magnet temperature calculated by the temperature calculation unit 41. More specifically, for example, the control unit 43 sets the magnitude of the current vector to be larger the lower the calculated magnet temperature. Then, the control unit 43 sets the dq-axis currents based on the magnitude of the set current vector.

[0049] Fig. 12 is a diagram showing the operating regions of the motor 50 before and after magnet heating treatment, which includes at least one of the ripple increasing process and the current increasing process described above. When the magnet temperature increases due to magnet heating treatment from the state before magnet heating treatment shown by the dashed line in Fig. 12, the magnetic force of the permanent magnet 57 weakens. As a result, as in the state after magnet heating treatment shown by the solid line in Fig. 12, the torque decreases, but the back electromotive force at the same rotation speed decreases, and the upper limit rotation speed of the rotor 56 increases.

[0050] The effects of this embodiment are summarized below. According to this embodiment, the motor control device 40 performs magnet heating processing including at least one of ripple increase processing and current increase processing on the condition that the magnet temperature is determined to be lower than the threshold value, thereby increasing the heating degree of the permanent magnet 57. This makes it possible to suppress the magnetic force of the permanent magnet 57 and increase the upper limit rotation speed of the rotor 56. Therefore, when the permanent magnet 57 is in a low temperature state, it is possible to maximize the upper limit output of the motor 50. Moreover, since the magnet heating processing can be performed simply by changing the control mode of the inverter 30, there is no need to change components such as the inverter 30 and the motor 50. Therefore, it is possible to suppress an increase in costs.

[0051] More specifically, according to the ripple increasing process, the control unit 43 can increase the amplitude of the ripple current flowing through the three-phase coils by lowering the frequency of the carrier signal Z, thereby increasing the heating degree of the permanent magnet 57. Also, according to the current increasing process, the control unit 43 can increase the heating degree of the permanent magnet 57 by changing the dq-axis currents flowing through the three-phase coils while keeping the torque output by the motor 50 the same before and after the change, thereby increasing the magnitude of the current vector flowing through the three-phase coils.

[0052] [Third embodiment] Next, a third embodiment will be described. In this embodiment, a temperature calculation unit 41 calculates the magnet temperature based on the square of the current value flowing through the three-phase coil, and a determination unit 42 determines whether the calculated magnet temperature is lower than a threshold value.

[0053] FIG. 13 is a graph showing the transition of magnet temperature and current squared value in this embodiment. As described above, there is a correlation between the transition of magnet temperature and the transition of current squared value. Therefore, in this embodiment, the temperature calculation unit 41 acquires current information of the three-phase coil from the current sensor 39 to calculate the current squared value, and calculates the magnet temperature based on the integrated value of the calculated current squared value. Specifically, for example, the control unit 43 estimates the magnet temperature at the start of the motor to be the same as the temperature of a predetermined item other than the permanent magnet 57 or the temperature of the cooling water. Then, after the motor is started, the control unit 43 estimates the current magnet temperature by updating the magnet temperature estimated at the start of the motor based on the integrated value of the current squared value.

[0054] According to this embodiment, the temperature calculation unit 41 calculates the magnet temperature based on the current squared value, and the determination unit 42 determines whether the calculated magnet temperature is lower than a threshold value. Therefore, it is possible to determine whether the magnet temperature is lower than a threshold value based on the current values ​​of the three-phase coils.

[0055] [Fourth embodiment] Next, a fourth embodiment will be described. In this embodiment, the determination unit 42 determines whether the magnet temperature is lower than a threshold value based on the magnitude of the magnetic flux of the permanent magnet 57.

[0056] 14 is a block diagram showing the processing of the motor control device 40 of this embodiment. The motor 50 is provided with a magnetic flux detection unit 52b that detects the magnitude of the magnetic flux of the permanent magnet 57. The magnetic flux detection unit 52b may be provided in a form that utilizes a part of the rotation angle sensor 53, for example, or may be provided separately from the rotation angle sensor 53.

[0057] The temperature calculation unit 41 calculates the magnet temperature based on the magnitude of the detected magnetic flux. Specifically, for example, the temperature calculation unit 41 stores a map or formula information showing the relationship between the magnitude of the magnetic flux and the magnet temperature in a storage unit such as a non-volatile memory, and calculates the magnet temperature based on the map or formula and the magnitude of the detected magnetic flux.

[0058] The determination unit 42 performs temperature determination based on the calculated magnet temperature. However, instead of this, the temperature calculation unit 41 may be eliminated and the determination unit 42 may directly perform temperature determination based on the magnitude of the detected magnetic flux. Specifically, in this case, for example, the determination unit 42 determines that the magnet temperature is lower than the threshold value on the condition that the magnitude of the detected magnetic flux is greater than the determination value. For example, the method described in JP 2019-122188 A may be referenced for this determination method.

[0059] According to the present embodiment, the determination unit 42 determines whether the magnet temperature is lower than the threshold value based on the magnitude of the magnetic flux of the permanent magnet 57. Therefore, it is possible to determine whether the magnet temperature is lower than the threshold value based on the magnitude of the magnetic flux of the permanent magnet 57 without acquiring the coil temperature or current value.

[0060] [Other embodiments] The embodiment described above can be modified as follows, for example.

[0061] In the first embodiment, ratio reduction control is performed as the output expansion control, and in the second embodiment, magnet heating control is performed as the output expansion control. Alternatively, both ratio reduction control and magnet heating control may be performed as the output expansion control. In this case, the upper limit rotation speed of the rotor 56 can be made higher when the permanent magnet 57 is at a low temperature, compared to when only one of them is performed.

[0062] In the second embodiment, if the rotation speed of the rotor 56 is high and a ripple increase process for lowering the frequency of the carrier signal Z is performed, there is a concern that the controllability of the rotor 56 may be reduced. For this reason, the ripple increase process may be performed on the condition that the rotation speed of the rotor 56 is determined to be lower than a threshold value. Note that, if the rotation speed of the rotor 56 is determined to be higher than the threshold value, for example, the output increase process itself may not be performed, or a process other than the ripple increase process, such as a current increase process, may be performed as the output increase process.

[0063] The upper and lower arm switches s1 and s2 are not limited to IGBTs, but may be, for example, N-channel MOSFETs with built-in body diodes. In this case, the positive terminal of the switch is the drain terminal, and the negative terminal is the source terminal.

[0064] The moving body on which the motor 50 and the motor control device 40 are mounted is not limited to a vehicle, and may be, for example, an aircraft or a ship. For example, if the moving body is an aircraft, the motor 50 serves as the flight power source for the aircraft. Also, for example, if the moving body is a ship, the motor 50 serves as the navigation power source for the ship. Also, the mounting location of the motor 50 is not limited to a moving body.

[0065] The motor 50 may be used as an actuator for an electric power steering device or an electric brake, for example, in addition to being used as a power source for moving a moving object.

[0066] The method of the motor control device 40 may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program, as described above. Alternatively, the method of the motor control device 40 may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the method of the motor control device 40 may be realized by one or more special-purpose computers configured by combining a processor and a memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer. [Explanation of symbols]

[0067] 30... inverter, 40... motor control device, 42... determination unit, 43... control unit, 50... motor, 51... stator, 56... rotor, 57... permanent magnet, cU... U-phase coil, cV... V-phase coil, cW... W-phase coil.

Claims

1. The present invention is applied to a system having a motor (50) having a stator (51) with coils (cU, cV, cW) and a rotor (56) with permanent magnets (57), and an inverter (30) connected to the coils, A motor control device (40) that rotates the rotor by passing a current through the coil under control of the inverter, The inverter includes an upper arm switch (s1) for each phase of the coil, and a lower arm switch (s2) connected in series to the upper arm switch, A determination unit (42) that determines whether or not the temperature of the permanent magnet is lower than a threshold value; a control unit (43) that performs a process of changing a control mode of the inverter in order to increase an upper limit rotation speed of the rotor on condition that the temperature of the permanent magnet is determined to be lower than the threshold value; having the control unit alternately switches between a first state in which a command for the upper arm switch is an ON command and a command for the lower arm switch is an OFF command and a second state in which a command for the upper arm switch is an OFF command and a command for the lower arm switch is an ON command based on a magnitude relationship between a carrier signal (Z) and a voltage command value (*V); A dead time (Dt) is provided between the first state period and the second state period, during which a command to the upper arm switch and the lower arm switch is set to an OFF command, As the change process, the control unit performs a process of lowering the frequency of the carrier signal compared to when the temperature of the permanent magnet is determined to be equal to or higher than the threshold value, thereby reducing the ratio of the dead time in one switching period of the upper and lower arm switches.

2. The motor control device of claim 1, wherein, as the change processing, the control unit performs processing to reduce the ratio of the dead time by shortening the length of the dead time in addition to lowering the frequency of the carrier signal compared to when the temperature of the permanent magnet is determined to be above the threshold value.

3. The present invention is applied to a system having a motor (50) having a stator (51) with coils (cU, cV, cW) and a rotor (56) with permanent magnets (57), and an inverter (30) connected to the coils, A motor control device (40) that rotates the rotor by passing a current through the coil under control of the inverter, The inverter includes an upper arm switch (s1) for each phase of the coil, and a lower arm switch (s2) connected in series to the upper arm switch, A determination unit (42) that determines whether or not the temperature of the permanent magnet is lower than a threshold value; a control unit (43) that performs a process of changing a control mode of the inverter in order to increase an upper limit rotation speed of the rotor on condition that the temperature of the permanent magnet is determined to be lower than the threshold value; having The control unit alternately switches between a first state in which a command for the upper arm switch is an ON command and a command for the lower arm switch is an OFF command, and a second state in which a command for the upper arm switch is an OFF command and a command for the lower arm switch is an ON command; A dead time (Dt) is provided between the first state period and the second state period, during which a command to the upper arm switch and the lower arm switch is set to an OFF command, As the change process, the control unit performs a process of reducing the ratio of the dead time to one switching period of the upper and lower arm switches by shortening the length of the dead time compared to when it is determined that the temperature of the permanent magnet is equal to or higher than the threshold value.

4. A motor control device as described in claim 2 or 3, wherein, in the change process, the control unit performs a process of setting the length of the dead time to be shorter the lower the temperatures of the upper arm switch and the lower arm switch.

5. 5. The motor control device according to claim 1, wherein the change process includes a process of increasing a degree of heating of the permanent magnet by changing a control mode of the inverter.

6. The control unit switches between the first state and the second state based on a magnitude relationship between a carrier signal (Z) and a voltage command value (*V), The motor control device according to claim 5 , wherein the change process includes a process of increasing a degree of heating of the permanent magnet by lowering a frequency of the carrier signal and increasing an amplitude of a ripple current flowing through the coil.

7. 7. The motor control device according to claim 5, wherein the change process includes a process of increasing a magnitude of a current vector flowing through the coils while keeping the torque output by the motor the same before and after the change by changing a dq-axis current flowing through the coils, thereby increasing a degree of heating of the permanent magnets.

8. A calculation unit (41) that calculates a temperature of the permanent magnet based on a temperature of the coil, 8. The motor control device according to claim 1, wherein the determination unit determines whether or not the calculated temperature of the permanent magnet is lower than the threshold value.

9. A calculation unit (41) that calculates a temperature of the permanent magnet based on a current value flowing through the coil, 8. The motor control device according to claim 1, wherein the determination unit determines whether or not the calculated temperature of the permanent magnet is lower than the threshold value.

10. 8. The motor control device according to claim 1, wherein the determination unit determines whether or not the temperature of the permanent magnet is lower than the threshold value based on a magnitude of magnetic flux of the permanent magnet.

11. A computer is applied to a system having a motor (50) having a stator (51) with coils (cU, cV, cW) and a rotor (56) with permanent magnets (57), and an inverter (30) connected to the coils, the computer (40) rotating the rotor by passing a current through the coils by controlling the inverter, The inverter includes an upper arm switch (s1) for each phase of the coil, and a lower arm switch (s2) connected in series to the upper arm switch, The computer includes: a determination process for determining whether or not the temperature of the permanent magnet is lower than a threshold value; a change process of changing a control mode of the inverter to increase an upper limit rotation speed of the rotor on condition that the temperature of the permanent magnet is determined to be lower than the threshold value; a process of alternately switching between a first state in which a command for the upper arm switch is an ON command and a command for the lower arm switch is an OFF command, and a second state in which a command for the upper arm switch is an OFF command and a command for the lower arm switch is an ON command, based on a magnitude relationship between a carrier signal (Z) and a voltage command value (*V); Execute a process including A dead time (Dt) is provided between the first state period and the second state period, during which a command to the upper arm switch and the lower arm switch is set to an OFF command, As the change process, a program performs a process of reducing the ratio of the dead time in one switching period of the upper and lower arm switches by lowering the frequency of the carrier signal compared to when the temperature of the permanent magnet is determined to be equal to or higher than the threshold value.

12. A computer is applied to a system having a motor (50) having a stator (51) with coils (cU, cV, cW) and a rotor (56) with permanent magnets (57), and an inverter (30) connected to the coils, the computer (40) rotating the rotor by passing a current through the coils by controlling the inverter, The inverter includes an upper arm switch (s1) for each phase of the coil, and a lower arm switch (s2) connected in series to the upper arm switch, The computer includes: a determination process for determining whether or not the temperature of the permanent magnet is lower than a threshold value; a change process of changing a control mode of the inverter to increase an upper limit rotation speed of the rotor on condition that it is determined that the temperature of the permanent magnet is lower than the threshold value; A process of alternately switching between a first state in which a command for the upper arm switch is an ON command and a command for the lower arm switch is an OFF command, and a second state in which a command for the upper arm switch is an OFF command and a command for the lower arm switch is an ON command; Execute a process including A dead time (Dt) is provided between the first state period and the second state period, during which a command to the upper arm switch and the lower arm switch is set to an OFF command, As the change process, the program performs a process of reducing the ratio of the dead time to one switching period of the upper and lower arm switches by shortening the length of the dead time compared to when it is determined that the temperature of the permanent magnet is equal to or higher than the threshold value.

13. A motor control method applied to a system having a motor (50) having a stator (51) with coils (cU, cV, cW) and a rotor (56) with permanent magnets (57), and an inverter (30) connected to the coils, the method rotating the rotor by passing a current through the coils by controlling the inverter, The inverter includes an upper arm switch (s1) for each phase of the coil, and a lower arm switch (s2) connected in series to the upper arm switch, a determining step of determining whether the temperature of the permanent magnet is lower than a threshold value; a changing step of changing a control mode of the inverter to increase an upper limit rotation speed of the rotor, on condition that it is determined that the temperature of the permanent magnet is lower than the threshold value; a step of alternately switching between a first state in which a command for the upper arm switch is an ON command and a command for the lower arm switch is an OFF command, and a second state in which a command for the upper arm switch is an OFF command and a command for the lower arm switch is an ON command, based on a magnitude relationship between a carrier signal (Z) and a voltage command value (*V); Including, A dead time (Dt) is provided between the first state period and the second state period, during which a command to the upper arm switch and the lower arm switch is set to an OFF command, In the change step, the frequency of the carrier signal is lowered compared to when the temperature of the permanent magnet is determined to be equal to or higher than the threshold value, thereby reducing the ratio of the dead time in one switching period of the upper and lower arm switches.

14. A motor control method applied to a system having a motor (50) having a stator (51) with coils (cU, cV, cW) and a rotor (56) with permanent magnets (57), and an inverter (30) connected to the coils, the method rotating the rotor by passing a current through the coils by controlling the inverter, The inverter includes an upper arm switch (s1) for each phase of the coil, and a lower arm switch (s2) connected in series to the upper arm switch, a determining step of determining whether the temperature of the permanent magnet is lower than a threshold value; a changing step of changing a control mode of the inverter to increase an upper limit rotation speed of the rotor, on condition that it is determined that the temperature of the permanent magnet is lower than the threshold value; A step of alternately switching between a first state in which a command for the upper arm switch is an ON command and a command for the lower arm switch is an OFF command, and a second state in which a command for the upper arm switch is an OFF command and a command for the lower arm switch is an ON command; Including, A dead time (Dt) is provided between the first state period and the second state period, during which a command to the upper arm switch and the lower arm switch is set to an OFF command, A motor control method in which the change step reduces the length of the dead time compared to when it is determined that the temperature of the permanent magnet is equal to or higher than the threshold value, thereby reducing the ratio of the dead time to one switching period of the upper and lower arm switches.

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