Motor control device

Abstract

A control device for an electric motor that can estimate the magnetic pole position even if the characteristics of the electric motor in question are unknown. [Solution] A control device 100 for a motor 1, which is a permanent magnet synchronous motor, includes a voltage application unit that applies a periodic pulse voltage having a peak at an electrical angle of 360° / n (n is an integer greater than or equal to 2) to the permanent magnet synchronous motor, a current detection unit 0 that detects the amplitude of a current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage, a magnetic pole position estimation unit 9 that estimates the magnetic pole position of the permanent magnet synchronous motor using the current amplitude, and a magnetic saturation detection unit 8 that detects magnetic saturation of the permanent magnet synchronous motor using the current amplitude. The voltage application unit varies the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant. The magnetic pole position estimation unit 9 estimates the magnetic pole position using the current amplitude when the magnetic saturation detection unit 8 detects magnetic saturation.

Description

[Technical Field]

[0001] The present disclosure relates to a control device for an electric motor. [Background technology]

[0002] Known motor control devices include a synchronous motor having a permanent magnet rotor and multiple phases, voltage application means for applying a voltage to each phase of the synchronous motor based on a voltage command, current detection means for detecting the value of a current flowing through each phase in response to the voltage, storage means for storing multiple voltage command vectors of the same amplitude and having a phase difference equally divided into 360 degrees, voltage control means for causing the voltage application means to sequentially switch between and apply multiple pulse voltages for magnetic pole position estimation to each phase based on a voltage command converted from the voltage command vector, and a device for calculating multiple current vectors based on the amplitude of the current flowing through each phase in synchronization with the multiple pulse voltages for magnetic pole position estimation, and calculating the magnetic pole position of the rotor based on the phase of an average vector of the multiple current vectors respectively responding to the multiple voltage command vectors (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-041881 Summary of the Invention [Problem to be solved by the invention]

[0004] The motor control device disclosed in Patent Document 1 calculates the magnetic pole position by utilizing the magnetic saturation of the motor. However, the voltage that can cause magnetic saturation varies depending on the characteristics of the motor. Therefore, it is necessary to design and set the voltage to be applied for each characteristic of the motor. Furthermore, if the characteristics of the motor are unknown, it is difficult to estimate the magnetic pole position.

[0005] The present disclosure has been made to solve such problems, and its purpose is to provide a control device for an electric motor that is capable of estimating the magnetic pole position even if the characteristics of the target electric motor are unknown. [Means for solving the problem]

[0006] A motor control device according to the present disclosure is a control device for a permanent magnet synchronous motor, and includes a voltage application unit that applies a periodic pulse voltage having a peak at an electrical angle of 360° / n (n is an integer of 2 or more) to the permanent magnet synchronous motor, a current detection unit that detects the amplitude of a current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage, a magnetic pole position estimation unit that estimates a magnetic pole position of the permanent magnet synchronous motor using the amplitude of the current, and a magnetic saturation detection unit that detects magnetic saturation of the permanent magnet synchronous motor using the amplitude of the current, and the voltage application unit varies the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant. Gradually increasing Let, the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when a difference between the magnetic pole position estimated by the magnetic pole position estimating unit using the amplitude of the current after the pulse width has been increased and the magnetic pole position estimated by the magnetic pole position estimating unit using the amplitude of the current before the pulse width has been increased is equal to or less than a preset reference value; The magnetic pole position estimation unit estimates the magnetic pole position using the amplitude of the current when the magnetic saturation detection unit detects magnetic saturation. [Effects of the Invention]

[0007] The electric motor control device according to the present disclosure has the advantage that it is possible to estimate the magnetic pole position even if the characteristics of the electric motor in question are unknown. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the overall configuration of a control device for an electric motor according to a first embodiment. [Figure 2] 3 is a diagram illustrating an example of time-series changes in voltage and current of the motor control device according to the first embodiment. FIG. [Figure 3] 3 is a diagram illustrating an example of magnetic saturation detection and magnetic pole position detection by the motor control device according to the first embodiment. FIG. [Figure 4]3 is a diagram illustrating an example of magnetic saturation detection and magnetic pole position detection by the motor control device according to the first embodiment. FIG. [Figure 5] 4 is a flowchart showing an example of processing by the control device for the electric motor according to the first embodiment. [Figure 6] 5A and 5B are diagrams illustrating a first modified example of magnetic saturation detection and magnetic pole position detection in the control device for the electric motor according to the first embodiment. [Figure 7] 5 is a flowchart showing an example of processing in a first modified example of the control device for the electric motor according to the first embodiment. FIG. [Figure 8] 5A and 5B are diagrams illustrating a second modified example of magnetic saturation detection and magnetic pole position detection in the control device for the electric motor according to the first embodiment. [Figure 9] 10 is a flowchart showing an example of processing in a second modified example of the control device for the electric motor according to the first embodiment. [Figure 10] 1 is a diagram showing an example of a configuration for realizing the functions of a control device for an electric motor according to a first embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of an electric motor control device according to the present disclosure will be described with reference to the accompanying drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals, and redundant explanations are appropriately simplified or omitted. For convenience, the following description may express the positional relationship of each structure based on the illustrated state. Note that the present disclosure is not limited to the following embodiments, and any combination of the embodiments, any modification of any component of each embodiment, or any omission of any component of each embodiment are possible within the scope of the present disclosure.

[0010] Embodiment 1 A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 10. FIG. 1 is a diagram illustrating the overall configuration of an electric motor control device. FIG. 2 is a diagram illustrating an example of time-series changes in voltage and current of the electric motor control device. FIGS. 3 and 4 are diagrams illustrating examples of magnetic saturation detection and magnetic pole position detection of the electric motor control device. FIG. 5 is a flow chart illustrating an example of processing by the electric motor control device. FIG. 6 is a diagram illustrating a first modified example of magnetic saturation detection and magnetic pole position detection of the electric motor control device. FIG. 7 is a flow chart illustrating an example of processing in the first modified example of the electric motor control device. FIG. 8 is a diagram illustrating a second modified example of magnetic saturation detection and magnetic pole position detection of the electric motor control device. FIG. 9 is a flow chart illustrating an example of processing in the second modified example of the electric motor control device. FIG. 10 is a diagram illustrating an example of a configuration for implementing the functions of the electric motor control device.

[0011] The electric motor 1 to be controlled by the electric motor control device according to this embodiment is a permanent magnet synchronous machine. In the configuration example shown in Fig. 1, the electric motor 1 is provided with a brake 2. The brake 2 is used to brake the rotation of the electric motor 1.

[0012] A control device 100 for an electric motor 1 according to this embodiment applies a periodic pulse voltage to the electric motor 1 in order to estimate the magnetic pole position of the electric motor 1 and detect magnetic saturation of the electric motor 1. As shown in Fig. 1, the control device 100 includes a voltage command generation unit 3, a voltage coordinate converter 4, a power converter 5, a current sensor 6, a current coordinate converter 7, a magnetic saturation detection unit 8, and a magnetic pole position estimation unit 9.

[0013] The voltage command generation unit 3 generates and outputs a periodic pulse-like voltage command having a peak at an electrical angle of 360° / n, where n is a preset integer of 2 or greater. In the configuration example described here, the voltage command generation unit 3 generates and outputs a voltage command Vαβ in a two-phase AC coordinate system, i.e., an αβ axis system.

[0014] The voltage command Vαβ output from the voltage command generation unit 3 is input to a voltage coordinate converter 4. The voltage coordinate converter 4 converts the voltage command Vαβ in the two-phase AC coordinate system into a voltage command Vuvw* in the three-phase AC coordinate system and outputs it. The voltage command Vuvw* output from the voltage coordinate converter 4 is input to a power converter 5.

[0015] The power converter 5 is an amplifier that applies a voltage according to the voltage command Vuvw* to the electric motor 1. As the power converter 5, for example, a PWM (Pulse Width Modulation) inverter can be used.

[0016] In this way, the voltage command generation unit 3, voltage coordinate converter 4, and power converter 5 constitute a voltage application unit that applies a periodic pulse voltage having a peak at an electrical angle of 360° / n (n is an integer of 2 or more) to the electric motor 1, which is a permanent magnet synchronous machine. The electric motor 1 is then driven in synchronization with the voltage applied by the power converter 5, i.e., the voltage application unit.

[0017] The current sensor 6 is a sensor that detects the three-phase current Iuvw flowing through the electric motor 1. The current sensor 6 may be a sensor that detects two of the three-phase currents flowing through the electric motor 1. In this case, the current sensor 6 can calculate the current of the remaining phase by using the relationship of three-phase balance. The three-phase current Iuvw detected by the current sensor 6 is input to a current coordinate converter 7.

[0018] The current coordinate converter 7 converts the current Iuvw in the three-phase AC coordinate system into a current Iαβ in the two-phase AC coordinate system and outputs it. The current Iαβ is a current value in the αβ axis system, which is the same coordinate system as the voltage command Vαβ. The current Iαβ output from the current coordinate converter 7 is input to a magnetic saturation detection unit 8 and a magnetic pole position estimation unit 9.

[0019] The magnetic saturation detection unit 8 uses the current Iαβ to detect whether magnetic saturation has occurred in the electric motor 1. If it detects that magnetic saturation has occurred in the electric motor 1, the magnetic saturation detection unit 8 outputs a magnetic saturation detection signal. The magnetic saturation detection signal output from the magnetic saturation detection unit 8 is input to the magnetic pole position estimation unit 9.

[0020] Furthermore, the magnetic saturation detection unit 8 outputs a command to change the pulse width of the pulse voltage depending on the detection result of whether magnetic saturation has occurred in the electric motor 1. The command to change the pulse width of the pulse voltage output from the magnetic saturation detection unit 8 is input to the voltage command generation unit 3. The voltage command generation unit 3 changes the pulse width of the voltage command Vαβ depending on the command to change the pulse width of the pulse voltage. At this time, the amplitude of the pulse voltage and the pulse peak position are kept constant. In this way, the voltage application unit described above changes the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant.

[0021] The magnetic pole position estimator 9 uses the current Iαβ to estimate the magnetic pole position of the electric motor 1. In addition, the magnetic pole position estimator 9 receives a magnetic saturation detection signal from the magnetic saturation detector 8 and determines the magnetic pole position of the electric motor 1. In other words, the magnetic pole position estimator 9 outputs the magnetic pole position estimated value when the magnetic saturation detector 8 detects that magnetic saturation has occurred in the electric motor 1 as the determined value of the magnetic pole position of the electric motor 1.

[0022] Next, estimation of the magnetic pole position of the electric motor 1 and detection of magnetic saturation in the control device 100 for the electric motor 1 according to this embodiment will be described. Fig. 2 shows an example of time-series waveforms of voltage and current when estimating the magnetic pole position of the electric motor 1.

[0023] First, we will explain the estimation of the magnetic pole position of the electric motor 1 by the magnetic pole position estimating unit 9. As described above, the voltage application unit of the control device 100 applies to the electric motor 1 a periodic pulse voltage having a peak at an electrical angle of 360° / n (n is an integer of 2 or more), that is, a pulse voltage with phases obtained by dividing an electrical angle of 360° at equal intervals.

[0024] The magnetic pole position estimation unit 9 identifies the magnetic pole position from the current value of the electric motor 1 when such a pulse voltage is applied to the electric motor 1. In other words, the current sensor 6 is a current detection unit that detects the amplitude of the current flowing through the electric motor 1 in synchronization with the pulse voltage. The magnetic pole position estimation unit 9 then estimates the magnetic pole position of the electric motor 1 using the amplitude of the current of the electric motor 1 detected by such a current detection unit.

[0025] When a pulse voltage is applied to the motor 1, the magnitude of the resultant magnetic flux, which is the magnetic flux due to the current generated by the applied voltage and the magnetic flux of the rotor, changes depending on the phase difference between the phase of the magnetic poles of the rotor of the motor 1 and the phase of the applied voltage. For example, if the phase difference between the phase of the magnetic poles of the rotor of the motor 1 and the phase of the applied voltage is 0°, in other words, if these phases are in phase, the magnetic flux due to the current generated by the applied voltage and the magnetic flux of the rotor will have the same direction. As a result, the sum of these magnetic fluxes becomes large, causing magnetic saturation in the iron core of the motor 1. When magnetic saturation occurs in the iron core of the motor 1, the winding inductance of the motor 1 decreases, and the amplitude of the current flowing through the motor 1 increases.

[0026] On the other hand, if the phase difference between the magnetic poles of the rotor of the motor 1 and the phase of the applied voltage is 180°, in other words, if these phases are in an anti-phase relationship, the magnetic flux due to the current generated by the applied voltage and the magnetic flux of the rotor magnet will have opposite directions. As a result, the sum of these magnetic fluxes becomes small, and magnetic saturation does not occur in the iron core of the motor 1. When magnetic saturation does not occur in the iron core of the motor 1, the winding inductance of the motor 1 increases, and the amplitude of the current flowing through the motor 1 decreases.

[0027] In this way, when a pulse voltage is applied to the motor 1, the degree of magnetic saturation in the iron core of the motor 1 varies depending on the phase difference between the phase of the magnetic poles of the rotor of the motor 1 and the phase of the applied voltage, and the amplitude of the current flowing through the motor 1 also changes. Therefore, the magnetic pole position estimation unit 9 can estimate the magnetic pole position of the motor 1 from the amplitude of the current of the motor 1 detected by the current detection unit.

[0028] Specifically, for example, the integer n, which is equal to or greater than 2, is set to 6. In other words, the electrical angle of 360° of the motor 1 is divided into six parts, and a periodic pulse voltage with a pulse peak every 60° is applied to the motor 1. The voltage waveform in this case is as shown in Figure 2. In this case, the amplitude of each pulse voltage on the αβ axes is expressed by the following equations (1) and (2).

[0029] Vα=V·cos(k×60°), (k=0~5) ··· (1) Vβ=V sin(k×60°), (k=0~5) (2)

[0030] The waveform of the voltage that flows through the motor 1 in synchronization with this pulse voltage is also as shown in Figure 2. At this time, the amplitude of the αβ-axis current Iαβ that flows through the motor 1 in synchronization with the pulse voltage is expressed by the following equations (3) and (4).

[0031] Iα=I·cos(k×60°), (k=0~5) ··· (3) Iβ=I·sin(k×60°), (k=0~5) ··· (4)

[0032] Since the motor 1 has resistance and inductance components, the amplitude of the current expressed by equations (3) and (4) actually appears as a first-order delay response determined by the electrical time constant. Here, if the magnitude of the voltage V in equations (1) and (2) is fixed, the current flowing through the motor 1 can be changed by changing the pulse width of the pulse voltage.

[0033] In other words, while the current increases according to the electrical time constant determined by the inductance and resistance of the motor 1, if the pulse width of the pulse voltage is small, i.e., the duration of application of one pulse voltage is short, the voltage application ends before the first-order lag response converges, and the first-order lag response does not continue, resulting in a small current amplitude. On the other hand, if the pulse width of the pulse voltage is large, i.e., the duration of application of one pulse voltage is long, the first-order lag response continues and the current amplitude increases. In this way, as the pulse width of the applied voltage increases, the current amplitude also increases, as shown in Figure 2. Furthermore, the larger the current amplitude, the larger the magnetic flux generated, making magnetic saturation more likely to occur.

[0034] The pulse width can be expressed, for example, in units of the sampling period in the voltage command generating unit 3. In this example, a pulse width of 1 means that the voltage command generating unit 3 generates a voltage command with a width equivalent to one sampling period. Also, a pulse width of 2 means that the voltage command generating unit 3 generates a voltage command with a width equivalent to two sampling periods. The same applies to pulse widths of 3, 4, ...

[0035] Next, the sums of the current values ​​Iα and Iβ corresponding to the application of pulse voltages Vα and Vβ are expressed by the following equations (5) and (6). Note that in equation (5), Iα1 = I·cos(0°), Iα2 = I·cos(60°), Iα3 = I·cos(120°), Iα4 = I·cos(180°), Iα5 = I·cos(240°), and Iα6 = I·cos(300°). Also, in equation (6), Iβ1 = I·sin(0°), Iβ2 = I·sin(60°), Iβ3 = I·sin(120°), Iβ4 = I·sin(180°), Iβ5 = I·sin(240°), and Iβ6 = I·sin(300°).

[0036] ΣIα=Iα1+Iα2+Iα3+Iα4+Iα5+Iα6 ··· (5) ΣIβ=Iβ1+Iβ2+Iβ3+Iβ4+Iβ5+Iβ6 ··· (6)

[0037] Here, since cos(0°) = 1, cos(60°) = cos(300°) = 1 / 2, cos(120°) = cos(240°) = -1 / 2, and cos(180°) = -1, if the current amplitude I remains constant at each electrical angle, the terms in equation (5) cancel out, and ΣIα = 0. Similarly, since sin(0°) = 0, sin(60°) = sin(120°) = √3 / 2, sin(180°) = 0, and sin(240°) = sin(300°) = -√3 / 2, if the current amplitude I remains constant at each electrical angle, the terms in equation (6) also cancel out, and ΣIβ = 0.

[0038] However, as mentioned above, ΣIα = ΣIβ = 0 occurs when the current amplitude I remains constant at each electrical angle. When magnetic saturation occurs, the inductance of the motor 1 decreases, allowing current to flow more easily and increasing the current amplitude I. In other words, when magnetic saturation occurs at a specific electrical angle θ, the current amplitude I at that electrical angle θ becomes larger than the current amplitude I at other electrical angles. As a result, terms that do not cancel out appear in equation (5), and ΣIα ≠ 0. Similarly, terms that do not cancel out appear in equation (6), and ΣIβ ≠ 0. The specific electrical angle θ at which such magnetic saturation occurs can be calculated using the following equation (7).

[0039] θ=arctan(ΣIβ / ΣIα) ··· (7)

[0040] As is clear from the above explanation, the conditions under which the current amplitude I becomes large include the following two. The difference between the phase (electrical angle) of the pulse voltage applied to the motor 1 and the phase (electrical angle) of the magnetic pole position of the rotor of the motor 1 is small. The pulse width of the pulse voltage applied to the motor 1 is large.

[0041] From the first condition, it can be said that the current amplitude I is maximum when a pulse voltage is applied whose peak is at the electrical angle that is the smallest difference from the electrical angle of the magnetic pole position of the electric motor 1. However, considering the second condition, if the pulse width of the pulse voltage is small, magnetic saturation will not occur even at the electrical angle that results in the maximum current amplitude I (the electrical angle closest to the magnetic pole position). Therefore, if the pulse width of the periodic pulse voltage applied to the electric motor 1 is changed while maintaining its amplitude constant, or more specifically, if the pulse width is gradually increased from the minimum, magnetic saturation will first occur when a pulse voltage whose peak is at the electrical angle that results in the maximum current amplitude I (the electrical angle closest to the magnetic pole position) is applied.

[0042] In this state, the specific electrical angle θ at which magnetic saturation occurs can be calculated using equation (7). This specific electrical angle θ at which magnetic saturation occurs is the electrical angle closest to the magnetic pole position. Therefore, the magnetic pole position estimation unit 9 can estimate the magnetic pole position θ using equation (7).

[0043] Here, the larger the pulse width of the pulse voltage, the more current flows, which is advantageous for estimating the magnetic pole position. However, excessive current flow can damage the power converter 5 and other hardware. For this reason, setting the pulse width is important. If the characteristics of the motor 1 are known, calculating the electrical time constant in advance allows us to estimate how much current will flow over what time, and therefore the pulse width can be determined in advance. On the other hand, if the characteristics of the motor 1 are unknown, the pulse width cannot be determined in advance, so detecting magnetic saturation is necessary to estimate the magnetic pole position θ using equation (7). Furthermore, if magnetic saturation can be detected, even if the characteristics of the motor 1 are known, the magnetic pole position θ can be estimated using equation (7) without calculating the electrical time constant and pulse width in advance.

[0044] Therefore, in the control device 100 for the electric motor 1 according to this embodiment, the magnetic saturation detection unit 8 detects the magnetic saturation of the electric motor 1. Then, the magnetic pole position estimation unit 9 estimates the magnetic pole position of the electric motor 1 by using the amplitude of the current detected by the current sensor 6 when the magnetic saturation detection unit 8 detects the magnetic saturation.

[0045] In this case, the voltage command generation unit 3 generates a voltage command for the pulse voltage while changing the pulse width while maintaining a constant amplitude until the magnetic saturation detection unit 8 detects magnetic saturation. That is, the magnetic saturation detection unit 8 outputs a command to increase the pulse width of the pulse voltage until it detects the occurrence of magnetic saturation in the electric motor 1. The voltage command generation unit 3 increases the pulse width of the voltage command Vαβ in response to this command. Then, when the magnetic saturation detection unit 8 detects the occurrence of magnetic saturation in the electric motor 1, it stops outputting the command to increase the pulse width of the pulse voltage.

[0046] Next, we will explain the detection of magnetic saturation of the electric motor 1 by the magnetic saturation detection unit 8. Figures 3 and 4 show an example of the absolute value of the detected current at each electrical angle when the pulse width of the pulse voltage applied to the electric motor 1 is changed in a case where the magnetic pole position is near an electrical angle of 300°.

[0047] First, for the α-axis, |cos(0°)| = |cos(180°)| = 1, |cos(60°)| = |cos(120°)| = |cos(240°)| = |cos(300°)| = 1 / 2. Therefore, if magnetic saturation does not occur because the pulse width is small and the current value is small, the current amplitude I at each electrical angle is equal, and therefore |Iα1| = |Iα4| and |Iα2| = |Iα3| = |Iα5| = |Iα6|. On the other hand, if magnetic saturation occurs near an electrical angle of 300° due to a large pulse width and a large current value, the current amplitude I near 300°, where the magnetic pole position is located, becomes large, and therefore |Iα1| = |Iα4| and |Iα2| = |Iα3| = |Iα5| ≠ |Iα6|. Therefore, the magnetic saturation detector 8 can detect magnetic saturation of the electric motor 1 by detecting this current difference.

[0048] Similarly, for the β-axis, when the pulse width is small and no magnetic saturation occurs, the current amplitude I at each electrical angle is equal, so |Iβ1| = |Iβ4| and |Iβ2| = |Iβ3| = |Iβ5| = |Iβ6|. On the other hand, when the pulse width is large and magnetic saturation occurs near an electrical angle of 300°, where the magnetic pole position is located, the current amplitude I near 300° becomes large, so |Iβ1| = |Iβ4| and |Iβ2| = |Iβ3| = |Iβ5| ≠ |Iβ6|. The magnetic saturation detection unit 8 can detect the magnetic saturation of the electric motor 1 by detecting this current difference.

[0049] However, the current value detected by the current sensor 6 includes a detection error. Also, there may be variations in the resistance and inductance of each phase of the electric motor 1, and variations in the voltage applied to each phase by the power converter 5. These factors may cause a change in the current amplitude I at a specific electrical angle, regardless of magnetic saturation, and thus a change in the absolute value of the current value at a specific electrical angle. Therefore, the magnetic saturation detector 8 may detect magnetic saturation of the electric motor 1 when the difference between the amplitudes of the currents corresponding to peaks at different electrical angles of the pulse voltage is equal to or greater than a predetermined first reference value. The first reference value may be set appropriately depending on, for example, the rated current of the electric motor 1, the rated current of the power converter 5, etc.

[0050] For example, for the α axis, the magnetic saturation detection unit 8 calculates the difference |Iα1|-|Iα4| between the magnitudes of Iα1 and Iα4 and determines whether this difference is within a first reference value. It also calculates the differences |Iα2|-|Iα3|, |Iα2|-|Iα5|, |Iα2|-|Iα6|, |Iα3|-|Iα5|, |Iα3|-|Iα6|, and |Iα5|-|Iα6| and determines whether these differences are greater than or equal to the first reference value.

[0051] Similarly, for the β axis, the magnetic saturation detection unit 8 calculates the difference |Iβ1|-|Iβ4| between the magnitudes of Iβ1 and Iβ4 and determines whether this difference is within the first reference value. It also calculates the differences |Iβ2|-|Iβ3|, |Iβ2|-|Iβ5|, |Iβ2|-|Iβ6|, |Iβ3|-|Iβ5|, |Iβ3|-|Iβ6|, |Iβ5|-|Iβ6| and |Iβ5|-|Iβ6| and determines whether these differences are greater than or equal to the first reference value.

[0052] If any of these differences is equal to or greater than a first reference value, the magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the electric motor 1. In the example shown in FIG. 3, when the pulse width exceeds 8, i.e., when the pulse width becomes 9, |Iα2|-|Iα6|, |Iα3|-|Iα6|, and |Iα5|-|Iα6| become equal to or greater than the first reference value, so the magnetic saturation detection unit 8 detects that magnetic saturation has occurred at pulse width 9. Similarly, in the example shown in FIG. 4, when the pulse width exceeds 8, i.e., when the pulse width becomes 9, |Iβ2|-|Iβ6|, |Iβ3|-|Iβ6|, and |Iβ5|-|Iβ6| become equal to or greater than the first reference value, so the magnetic saturation detection unit 8 detects that magnetic saturation has occurred at pulse width 9. Note that the detection and determination of magnetic saturation may be performed using both the α-axis and β-axis current values, or may be performed using only the α-axis or β-axis current value.

[0053] Next, an example of the processing for detecting magnetic saturation and determining the magnetic pole position in the control device 100 for the electric motor 1 according to this embodiment will be described with reference to the flowchart in Fig. 5. When the control device 100 starts estimating the magnetic pole position of the electric motor 1 and detecting magnetic saturation, first, in step S001, the voltage command generation unit 3 generates a pulse voltage command, and the power converter 5 applies a periodic pulse voltage to the electric motor 1.

[0054] In the following step S002, the current sensor 6 detects the amplitude of the current flowing through the electric motor 1 in response to the pulse voltage applied in step S001. After application of the pulse voltage for one rotation of 360° in electrical angle has been completed, in step S003, the magnetic saturation detection unit 8 uses the current amplitude acquired in step S002 to determine whether the difference between the absolute values ​​of the currents corresponding to each electrical angle is equal to or greater than a first reference value. If the difference between the absolute values ​​of the currents corresponding to each electrical angle is not equal to or greater than the first reference value, the control device 100 performs the process of step S005, in which the magnetic saturation detection unit 8 outputs a command to the voltage command generation unit 3 to increase the pulse width of the pulse voltage. The control device 100 then returns to step S001 to continue the process, applies the pulse voltage again, and performs the processes of steps S002 and S003 again.

[0055] On the other hand, if the difference between the absolute values ​​of the currents corresponding to each electrical angle is equal to or greater than the first reference value in step S003, the magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the electric motor 1. In this case, the control device 100 then performs the process of step S004. In step S004, the magnetic saturation detection unit 8 outputs a magnetic saturation detection signal to the magnetic pole position estimator 9. Then, upon receiving the magnetic saturation detection signal, the magnetic pole position estimator 9 outputs the estimated magnetic pole position as a confirmed value of the magnetic pole position of the electric motor 1. When the process of step S004 is completed, the series of processes ends.

[0056] The control device 100 for the electric motor 1 configured as described above can detect magnetic saturation based on the magnitude of the current value at each electrical angle by utilizing the fact that the current value near the electrical angle where magnetic saturation occurs is larger than the current value at other electrical angles.The magnetic pole position can then be estimated from the current value when magnetic saturation is detected.As a result, even if the characteristics of the target electric motor 1 are unknown, it is possible to accurately estimate the magnetic pole position.

[0057] Next, several modified examples of magnetic saturation detection in the control device 100 for the electric motor 1 according to this embodiment will be described. First, a first modified example of magnetic saturation detection will be described with reference to Figs. 6 and 7. In this first modified example, the magnetic saturation detection unit 8 calculates the sum of the amplitude of the current flowing through the electric motor 1 for each axis, corresponding to peaks at different electrical angles of the pulse voltage applied to the electric motor 1. Then, the magnetic saturation detection unit 8 detects magnetic saturation of the electric motor 1 when the sum of the squares of the sum of the amplitude of the current for each axis is equal to or greater than a preset second reference value.

[0058] FIG. 6 shows an example of the sum of squares of the total current amplitude for each axis when the pulse width of the pulse voltage applied to the electric motor 1 is changed when the magnetic pole position is near 300° electrical angle. First, for the α axis, if the pulse width is small and the current value is small, and no magnetic saturation occurs, the current amplitude I at each electrical angle is equal, as described above, so the terms in equation (5) cancel each other out, and ΣIα = 0. On the other hand, if the pulse width is large and magnetic saturation occurs near 300° electrical angle, where the magnetic pole position is located, the current amplitude I near 300° electrical angle becomes large, and |Iα1| = |Iα4| and |Iα2| = |Iα3| = |Iα5| ≠ |Iα6|. Therefore, ΣIα ≠ 0.

[0059] Similarly, for the β axis, if the current amplitude I is assumed to be constant and not change at each electrical angle, the terms in equation (6) cancel each other out, and ΣIβ = 0. On the other hand, if the pulse width is large and magnetic saturation occurs near an electrical angle of 300°, where the magnetic pole position is located, the current amplitude I near an electrical angle of 300° will become large, and |Iβ1| = |Iβ4| and |Iβ2| = |Iβ3| = |Iβ5| ≠ |Iβ6|. Therefore, ΣIβ ≠ 0.

[0060] The magnetic saturation detection unit 8 detects that magnetic saturation is occurring in the electric motor 1 if the sum of the squares of the sum of the currents for each electrical angle on the α-axis, ΣIα, and the sum of the currents for each electrical angle on the β-axis, ΣIβ ((ΣIα)^2 + (ΣIβ)^2), is equal to or greater than a predetermined second reference value. The second reference value can be set appropriately depending on, for example, the rated current of the electric motor 1, the rated current of the power converter 5, etc. Note that the square root of the sum of the squares of ΣIα and ΣIβ can be used instead of the sum of the squares of ΣIα and ΣIβ, which is essentially the same. In this sense, in the present disclosure, the square root of the sum of the squares of ΣIα and ΣIβ may also be simply referred to as the sum of the squares of ΣIα and ΣIβ. In the example shown in Figure 6, when the pulse width exceeds 8, i.e., when the pulse width becomes 9, √((ΣIα)^2+(ΣIβ)^2) becomes greater than or equal to the second reference value, so the magnetic saturation detection unit 8 detects that magnetic saturation has occurred at pulse width 9.

[0061] Next, an example of the processing for detecting magnetic saturation and determining the magnetic pole position in the first modified example of the control device 100 for the electric motor 1 according to this embodiment will be described with reference to the flowchart in Fig. 7. When the control device 100 starts estimating the magnetic pole position of the electric motor 1 and detecting magnetic saturation, first, in step S101, the voltage command generator 3 generates a pulse voltage command, and the power converter 5 applies a periodic pulse voltage to the electric motor 1.

[0062] In the following step S102, the current sensor 6 detects the amplitude of the current flowing through the electric motor 1 in response to the pulse voltage applied in step S101. After application of the pulse voltage for one rotation of 360° in electrical angle has been completed, in step S103, the magnetic saturation detection unit 8 uses the current amplitude acquired in step S102 to determine whether the sum of the squares of the sum of the currents for each electrical angle on the α-axis, ΣIα, and the sum of the currents for each electrical angle on the β-axis, ΣIβ, is equal to or greater than a second reference value. If the sum of the squares of ΣIα and ΣIβ is not equal to or greater than the second reference value, the control device 100 performs the process of step S105, and the magnetic saturation detection unit 8 outputs a command to the voltage command generation unit 3 to increase the pulse width of the pulse voltage. The control device 100 then returns to step S101 to continue the process, applies the pulse voltage again, and performs the processes of steps S102 and S103 again.

[0063] On the other hand, if the sum of the squares of ΣIα and ΣIβ is equal to or greater than the second reference value in step S103, the magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the electric motor 1. In this case, the control device 100 then performs the process of step S104. In step S104, the magnetic saturation detection unit 8 outputs a magnetic saturation detection signal to the magnetic pole position estimation unit 9. Then, upon receiving the magnetic saturation detection signal, the magnetic pole position estimation unit 9 outputs the estimated magnetic pole position as a confirmed value of the magnetic pole position of the electric motor 1. When the process of step S104 is completed, the series of processes ends.

[0064] The first modified example of the control device 100 configured as described above also makes it possible to accurately estimate the magnetic pole position even if the characteristics of the target electric motor 1 are unknown. Furthermore, according to the first modified example, magnetic saturation can be determined by unified processing rather than determining magnetic saturation based on the current value for each coordinate axis.

[0065] Next, a second modified example of magnetic saturation detection will be described with reference to FIGS. 8 and 9. In this second modified example, magnetic saturation of the electric motor 1 is detected using the magnetic pole position estimated by the magnetic pole position estimation unit 9. More specifically, the voltage application unit gradually increases the pulse width of the pulse voltage applied to the electric motor 1 while maintaining the amplitude constant. The magnetic saturation detection unit 8 detects magnetic saturation of the electric motor 1 when the difference between the magnetic pole positions estimated by the magnetic pole position estimation unit 9 before and after the increase in the pulse width of the pulse voltage applied to the electric motor 1 is equal to or less than a predetermined third reference value. In other words, the magnetic pole position estimation unit 9 estimates the magnetic pole position each time the pulse width is increased. The magnetic saturation detection unit 8 detects magnetic saturation of the electric motor 1 when the change in the magnetic pole position estimated by the magnetic pole position estimation unit 9 remains equal to or less than the third reference value multiple times in succession as the pulse width is gradually increased.

[0066] When magnetic saturation does not occur and there is no change in current amplitude at a specific electrical angle, or when current detection errors and the like are dominant, the estimated magnetic pole position is inaccurate, and the estimated magnetic pole position changes each time the pulse width of the applied voltage is changed. In contrast, when magnetic saturation occurs, the change in current amplitude at a specific electrical angle becomes more significant than current detection errors and the like. This stabilizes the estimated magnetic pole position, and the estimated magnetic pole position does not change even when the pulse width of the applied voltage is changed. Therefore, the magnetic pole position is estimated each time the pulse width of the applied voltage is changed. If, for example, the estimated magnetic pole position does not change multiple times in succession, more specifically, if the estimated magnetic pole position falls within a third reference value multiple times in succession, it is determined that magnetic saturation has occurred, and the magnetic pole position is determined.

[0067] Figure 8 shows an example of the pulse width of the applied voltage and the estimated magnetic pole position. If the pulse width is small and magnetic saturation does not occur, preventing accurate magnetic pole position estimation, the estimated magnetic pole position results will change each time the pulse width is changed. This corresponds to pulse widths 1 to 5 in Figure 8. In contrast, if the pulse width is large and magnetic saturation occurs, allowing accurate magnetic pole position estimation, the estimated magnetic pole position results will not change much even if the pulse width is changed. This corresponds to pulse widths 6 and above in Figure 8.

[0068] Whether magnetic saturation has occurred can be determined, for example, by determining whether the difference ((θm+1) - (θm)) between the magnetic pole estimation value θm at pulse width m and the magnetic pole estimation value θm+1 at pulse width m+1 is equal to or less than a third reference value. In the example of Fig. 8, the difference (θ3 - θ2) between the magnetic pole estimation value θ2 at pulse width 2 and the magnetic pole estimation value θ3 at pulse width 3 is greater than the third reference value. Therefore, the magnetic saturation detection unit 8 determines that magnetic saturation has not occurred.

[0069] On the other hand, since the difference between the magnetic pole estimation value θ6 with pulse width 6 and the magnetic pole estimation value θ7 with pulse width 7 is within the reference value, it is determined that magnetic saturation has occurred, and therefore it is determined that the magnetic pole estimation result is stable. Furthermore, since the difference between the magnetic pole estimation value θ7 with pulse width 7 and the magnetic pole estimation value θ8 with pulse width 8 is also within the third reference value, it is determined that magnetic saturation has occurred. In this way, if a situation in which it is determined that magnetic saturation has occurred occurs multiple times in succession, it may be determined that the magnetic pole position has been accurately estimated, and the magnetic pole position may be confirmed.

[0070] Next, an example of the processing for detecting magnetic saturation and determining the magnetic pole position in the second modified example of the control device 100 for the electric motor 1 according to this embodiment will be described with reference to the flowchart in Fig. 9. When the control device 100 starts estimating the magnetic pole position of the electric motor 1 and detecting magnetic saturation, first, in step S201, the voltage command generator 3 generates a pulse voltage command, and the power converter 5 applies a periodic pulse voltage to the electric motor 1.

[0071] In the next step S202, the current sensor 6 detects the amplitude of the current flowing through the electric motor 1 in response to the pulse voltage applied in step S201. Then, when the application of the pulse voltage for one rotation of 360° in electrical angle has been completed, the magnetic pole position estimation unit 9 estimates the magnetic pole position using the detected current amplitude. After step S202, the control device 100 then performs the process of step S203. In step S203, magnetic saturation detection unit 8 determines whether the difference between the previous estimate of the magnetic pole position by magnetic pole position estimator 9 and the current estimate of the magnetic pole position by magnetic pole position estimator 9 is equal to or less than a third reference value. If the difference between the previous and current estimates of the magnetic pole position is not equal to or less than the third reference value, control device 100 performs the process of step S205, and magnetic saturation detection unit 8 outputs a command to voltage command generator 3 to increase the pulse width of the pulse voltage. Then, control device 100 returns to step S201 to continue the process, applies the pulse voltage again, and performs the processes of steps S202 and S203 again.

[0072] On the other hand, if the difference between the previous and current estimated values ​​of the magnetic pole position is equal to or less than the third reference value in step S203, the magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the electric motor 1. In this case, the control device 100 then performs the process of step S204. In step S204, the magnetic saturation detection unit 8 outputs a magnetic saturation detection signal to the magnetic pole position estimation unit 9. Then, upon receiving the magnetic saturation detection signal, the magnetic pole position estimation unit 9 outputs the currently estimated magnetic pole position as the confirmed value of the magnetic pole position of the electric motor 1. When the process of step S204 is completed, the series of processes ends.

[0073] The second modified example of the control device 100 configured as described above also makes it possible to estimate the magnetic pole position with high accuracy even if the characteristics of the target electric motor 1 are unknown. Furthermore, according to the second modified example, when magnetic saturation occurs, the change in the magnetic pole position estimate value becomes small even if the pulse width changes, and this makes it possible to improve the accuracy of detecting magnetic saturation.

[0074] In the control device 100 for the electric motor 1 configured as described above, when a pulse voltage is applied, torque may be generated depending on the phase of the pulse voltage, causing the electric motor 1 to rotate. If the electric motor 1 rotates, accurate magnetic pole position estimation becomes difficult. Therefore, it is desirable to estimate the magnetic pole position and detect magnetic saturation when the electric motor 1 is braked by the brake 2. That is, the magnetic pole position estimator 9 may estimate the magnetic pole position of the electric motor 1 when the electric motor 1 is braked by the brake 2. Furthermore, the magnetic saturation detector 8 may detect the magnetic saturation of the electric motor 1 when the electric motor 1 is braked by the brake 2. Alternatively, the magnetic pole position estimation and magnetic saturation detection may be performed when the rotation of the electric motor 1 is suppressed by a mechanical overload, rather than by the brake 2.

[0075] Furthermore, the magnetic saturation detection unit 8 may store the pulse width of the applied voltage when magnetic saturation of the electric motor 1 is detected. In this case, when estimating the magnetic pole position from the next time onward, the magnetic saturation detection unit 8 may output a command signal to the voltage command generation unit 3 to generate a voltage command with the pulse width stored when magnetic saturation was previously detected. That is, the voltage application unit may apply a pulse voltage with the pulse width stored in the magnetic saturation detection unit 8 to the electric motor 1. By doing so, for example, when it is necessary to estimate the magnetic pole position each time the electric motor 1 is powered on or each time control of the electric motor 1 is started, it is possible to detect magnetic saturation only the first time, and thereafter apply to the electric motor 1 a voltage with a pulse width that generates magnetic saturation without having to detect magnetic saturation.

[0076] The voltage command generating unit 3 may output a voltage command Vuvw* in a three-phase AC coordinate system instead of the voltage command Vαβ in the two-phase AC coordinate system. In this case, the voltage coordinate converter 4 is not required. The magnetic saturation detecting unit 8 may detect whether magnetic saturation has occurred in the motor 1 using the current Iuvw in the three-phase AC coordinate system instead of the current Iαβ in the two-phase AC coordinate system. Similarly, the magnetic pole position estimating unit 9 may estimate the magnetic pole position of the motor 1 using the current Iuvw in the three-phase AC coordinate system instead of the current Iαβ in the two-phase AC coordinate system. In this case, the current coordinate converter 7 is not required.

[0077] Furthermore, the number of divisions n of the electrical angle at which the peaks of the pulse voltage applied to the electric motor 1 are located is not limited to 6, as has been described above as an example. In other words, the interval between the peaks of the pulse voltage is not limited to an electrical angle of 60°. The number of divisions n may be 12, meaning that the interval between the peaks is an electrical angle of 30°, or the number of divisions n may be 24, meaning that the interval between the peaks is an electrical angle of 15°. Note that the larger the number of divisions n, the more the resolution of the estimated magnetic pole position can be improved.

[0078] FIG. 10 is a diagram showing an example of a configuration for realizing the functions of the control device 100 in this embodiment. The functions of the control device 100 are realized by, for example, a processing circuit. The processing circuit may include a processor 101 and a memory 102. The processing circuit may be dedicated hardware 103. A part of the processing circuit may be formed as dedicated hardware 103, and the processing circuit may further include a processor 101 and a memory 102. In the example shown in the figure, a part of the processing circuit is formed as dedicated hardware 103. Furthermore, in the example shown in the figure, the processing circuit further includes a processor 101 and a memory 102.

[0079] The processing circuitry, part of which is at least one dedicated hardware 103, may be, for example, a single circuit, a multiple circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. If the processing circuitry comprises at least one processor 101 and at least one memory 102, the functionality of the control device 100 may be realized by software, firmware, or a combination of software and firmware.

[0080] The software and firmware are written as programs and stored in memory 102. Processor 101 realizes the functions of each unit by reading and executing the programs stored in memory 102. Processor 101 is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. Memory 102 may include, for example, non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM, or a magnetic disk, flexible disk, optical disk, compact disk, minidisk, DVD, etc.

[0081] In this way, the processing circuit of the control device 100 can realize each function of the control device 100 by hardware, software, firmware, or a combination of these. When the processing circuit of the control device 100 includes at least the processor 101 and the memory 102, the processor 101 executes a program stored in the memory 102 in the control device 100, and the hardware and software of the control device 100 work together to realize the functions of each of the units included in the control device 100, namely, the voltage command generation unit 3, the voltage coordinate converter 4, the current coordinate converter 7, the magnetic saturation detection unit 8, and the magnetic pole position estimation unit 9. Note that the electric motor 1 is not limited to a configuration in which its operation is controlled by a single control device 100. The operation of the electric motor 1 may be controlled by a plurality of devices working together.

[0082] In the present disclosure, the embodiments may be combined in any manner without departing from the spirit of the present disclosure. Examples of various aspects of the present disclosure are summarized below as appendices. (Appendix 1) A control device for a motor that is a permanent magnet synchronous motor, a voltage application unit that applies a periodic pulse voltage having a peak at an electrical angle of 360° / n (n is an integer of 2 or more) to the permanent magnet synchronous motor; a current detection unit that detects the amplitude of a current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage; a magnetic pole position estimating unit that estimates a magnetic pole position of the permanent magnet synchronous motor using the amplitude of the current; a magnetic saturation detection unit that detects magnetic saturation of the permanent magnet synchronous motor using the amplitude of the current, the voltage application unit changes the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant, The magnetic pole position estimation unit estimates the magnetic pole position using the amplitude of the current when the magnetic saturation detection unit detects magnetic saturation. (Appendix 2) 2. The motor control device according to claim 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when a difference between absolute values ​​of the currents corresponding to peaks at different electrical angles of the pulse voltage is equal to or greater than a predetermined first reference value. (Appendix 3) The magnetic saturation detection unit calculating a sum of the amplitudes of the currents corresponding to peaks at different electrical angles of the pulse voltage on each axis; 2. The motor control device according to claim 1, wherein magnetic saturation of the permanent magnet synchronous motor is detected when the sum of squares of the total sums for each axis is equal to or greater than a second reference value set in advance. (Appendix 4) the voltage application unit gradually increases the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant, The motor control device according to claim 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when a difference between the magnetic pole position estimated by the magnetic pole position estimating unit using the amplitude of the current after the pulse width has been increased and the magnetic pole position estimated by the magnetic pole position estimating unit using the amplitude of the current before the pulse width has been increased is equal to or less than a preset third reference value. (Appendix 5) the magnetic pole position estimating unit estimates the magnetic pole position when the permanent magnet synchronous motor is braked, 5. The motor control device according to claim 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when the permanent magnet synchronous motor is braked by a brake. (Appendix 6) the magnetic saturation detection unit stores a pulse width of the pulse voltage applied to the permanent magnet synchronous motor when magnetic saturation of the permanent magnet synchronous motor is detected, 6. The motor control device according to claim 1, wherein the voltage application unit applies the pulse voltage having the pulse width stored in the magnetic saturation detection unit to the permanent magnet synchronous motor. [Explanation of symbols]

[0083] 1 electric motor 2. Brakes 3. Voltage command generator 4. Voltage coordinate converter 5 Power Converter 6 Current Sensor 7 Current coordinate converter 8 Magnetic saturation detector 9 Magnetic pole position estimation section 100 control device 101 processors 102 memory 103 Dedicated Hardware

Claims

1. A control device for a motor that is a permanent magnet synchronous motor, a voltage application unit that applies a periodic pulse voltage having a peak at an electrical angle of 360° / n (n is an integer of 2 or more) to the permanent magnet synchronous motor; a current detection unit that detects the amplitude of a current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage; a magnetic pole position estimating unit that estimates a magnetic pole position of the permanent magnet synchronous motor using the amplitude of the current; a magnetic saturation detection unit that detects magnetic saturation of the permanent magnet synchronous motor using the amplitude of the current, the voltage application unit gradually increases the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant, the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when a difference between the magnetic pole position estimated by the magnetic pole position estimating unit using the amplitude of the current after the pulse width has been increased and the magnetic pole position estimated by the magnetic pole position estimating unit using the amplitude of the current before the pulse width has been increased is equal to or less than a preset reference value; The magnetic pole position estimation unit estimates the magnetic pole position using the amplitude of the current when the magnetic saturation detection unit detects magnetic saturation.

2. the magnetic pole position estimating unit estimates the magnetic pole position when the permanent magnet synchronous motor is braked, 2. The motor control device according to claim 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when the permanent magnet synchronous motor is braked by a brake.

3. the magnetic saturation detection unit stores a pulse width of the pulse voltage applied to the permanent magnet synchronous motor when magnetic saturation of the permanent magnet synchronous motor is detected, 3. The motor control device according to claim 1, wherein the voltage application unit applies the pulse voltage having the pulse width stored in the magnetic saturation detection unit to the permanent magnet synchronous motor.

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