Electric motor control unit

Abstract

The present invention provides a motor control device that enables the estimation of magnetic pole positions even when the characteristics of the target motor are unknown. [Solution] The control device 100 for the motor 1, which is a permanent magnet synchronous motor, includes a voltage application unit that applies a periodic pulse voltage with a peak at an electrical angle of 360° / n (where n is an integer of 2 or more) to the permanent magnet synchronous motor, a current detection unit 0 that detects the amplitude of the 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 amplitude of the current, and a magnetic saturation detection unit 8 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 9 estimates the magnetic pole position using the amplitude of the current 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 Art

[0002] In a control device for an electric motor, there are a synchronous motor having a rotor with permanent magnets and a plurality of 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 a current value flowing in each phase in response to the voltage, storage means for storing a plurality of voltage command vectors having the same amplitude and a phase difference obtained by equally dividing 360 degrees, voltage control means for sequentially switching and applying a plurality of pulse voltages for estimating magnetic pole positions to each phase based on a voltage command obtained by converting a voltage command vector to the voltage application means, calculating a plurality of current vectors based on the amplitude of the current flowing in each phase in synchronization with the plurality of pulse voltages for estimating magnetic pole positions, and calculating the magnetic pole position of the rotor based on the phase of the average vector of the plurality of current vectors corresponding to the plurality of voltage command vectors respectively. (For example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] This disclosure was made to solve these problems. Its purpose is to provide a motor control device that can estimate the magnetic pole position even when the characteristics of the target motor are unknown. [Means for solving the problem]

[0006] The motor control device according to this disclosure is a motor control device that is a permanent magnet synchronous motor, and comprises: a voltage application unit that applies a periodic pulse voltage having a peak at an electrical angle of 360° / n (where n is an integer of 2 or more) to the permanent magnet synchronous motor; a current detection unit that detects the amplitude of the current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage; a magnetic pole position estimation unit that estimates the 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, wherein the voltage application unit changes the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant, and 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 motor control device described herein has the effect of being able to estimate the magnetic pole position even if the characteristics of the target motor are unknown. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the overall configuration of the control device for the electric motor according to Embodiment 1. [Figure 2] This figure illustrates an example of the time-series changes in voltage and current of the control device for an electric motor according to Embodiment 1. [Figure 3] This figure illustrates an example of magnetic saturation detection and magnetic pole position detection in a control device for an electric motor according to Embodiment 1. [Figure 4] This figure illustrates an example of magnetic saturation detection and magnetic pole position detection in a control device for an electric motor according to Embodiment 1. [Figure 5]This is a flowchart showing an example of the processing of the control device for an electric motor according to Embodiment 1. [Figure 6] This figure illustrates a first modified example of the magnetic saturation detection and magnetic pole position detection of the electric motor control device according to Embodiment 1. [Figure 7] This is a flowchart showing an example of processing in a first modified example of the control device for an electric motor according to Embodiment 1. [Figure 8] This figure illustrates a second modified example of the magnetic saturation detection and magnetic pole position detection of the electric motor control device according to Embodiment 1. [Figure 9] This is a flowchart showing an example of processing in a second modified example of the control device for an electric motor according to Embodiment 1. [Figure 10] This figure shows an example of a configuration that realizes the functions of the control device for an electric motor according to Embodiment 1. [Modes for carrying out the invention]

[0009] Embodiments for implementing the electric motor control device described herein will be explained with reference to the attached drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are simplified or omitted as appropriate. For convenience, the positional relationships of each structure may be expressed based on the illustrated state in the following explanation. This disclosure is not limited to the embodiments described below, and any combination of embodiments, any modification of any component of each embodiment, or any omission of any component of each embodiment is possible without departing from the spirit of this disclosure.

[0010] Embodiment 1. Embodiment 1 of the present disclosure will be described with reference to Figures 1 to 10. Figure 1 is a diagram showing the overall configuration of the motor control device. Figure 2 is a diagram illustrating an example of the time-series changes of the voltage and current of the motor control device. Figures 3 and 4 are diagrams illustrating examples of magnetic saturation detection and magnetic pole position detection of the motor control device, respectively. Figure 5 is a flowchart showing an example of the processing of the motor control device. Figure 6 is a diagram illustrating a first modified example of magnetic saturation detection and magnetic pole position detection of the motor control device. Figure 7 is a flowchart showing an example of the processing in the first modified example of the motor control device. Figure 8 is a diagram illustrating a second modified example of magnetic saturation detection and magnetic pole position detection of the motor control device. Figure 9 is a flowchart showing an example of the processing in the second modified example of the motor control device. Figure 10 is a diagram showing an example of a configuration that realizes the functions of the motor control device.

[0011] The motor 1 controlled by the motor control device according to this embodiment is a permanent magnet synchronous motor. In the configuration example shown in Figure 1, the motor 1 is equipped with a brake 2. The brake 2 is for braking the rotation of the motor 1.

[0012] The control device 100 for the 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 to detect magnetic saturation of the electric motor 1. As shown in Figure 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 with a peak at an electrical angle of 360° / n. Herein, n is a preset integer of 2 or more. 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 the 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 the power converter 5.

[0015] The power converter 5 is an amplifier that applies a voltage corresponding to the voltage command Vuvw* to the 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, the voltage coordinate converter 4, and the 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 motor 1, which is a permanent magnet synchronous machine. And the motor 1 is driven in synchronization with the voltage applied by the power converter 5, that is, the voltage application unit.

[0017] The current sensor 6 is a sensor that detects the three-phase current Iuvw flowing through the motor 1. The current sensor 6 may detect two of the three-phase currents flowing through the motor 1. In this case, the current sensor 6 can calculate the remaining one-phase current by using the three-phase balance relationship. The three-phase current Iuvw detected by the current sensor 6 is input to the 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 the 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 the magnetic saturation detection unit 8 and the magnetic pole position estimation unit 9.

[0019] The magnetic saturation detection unit 8 uses the current Iαβ to detect whether or not magnetic saturation is occurring in the motor 1. If magnetic saturation is detected in the 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 according to the detection result of whether or not magnetic saturation is occurring in the 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 in the voltage command Vαβ according to the command to change the pulse width of the pulse voltage. At this time, the amplitude of the pulse voltage and the peak position of the pulse are kept constant. In this way, the voltage application unit described above changes the pulse width of the pulse voltage while keeping the amplitude of the pulse voltage constant.

[0021] The magnetic pole position estimation unit 9 estimates the magnetic pole position of the motor 1 using the current Iαβ. The magnetic pole position estimation unit 9 also receives a magnetic saturation detection signal from the magnetic saturation detection unit 8 and determines the magnetic pole position of the motor 1. In other words, the magnetic pole position estimation unit 9 outputs the estimated magnetic pole position value at the time the magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the motor 1 as the determined value of the magnetic pole position of the motor 1.

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

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

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

[0025] When a pulse voltage is applied to the motor 1, the magnitude of the combined magnetic flux of 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°, that is, if these phases are in phase, the direction of the magnetic flux of the current generated by the applied voltage and the magnetic flux of the rotor's magnets will be the same. As a result, the sum of these magnetic fluxes becomes large, and magnetic saturation occurs 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 phase of the magnetic poles of the rotor of motor 1 and the phase of the applied voltage is 180°, that is, if these phases are in opposite phases, the direction of the magnetic flux due to the current generated by the applied voltage and the magnetic flux of the rotor magnets will be opposite. As a result, the sum of these magnetic fluxes becomes small, and magnetic saturation does not occur in the iron core of motor 1. When magnetic saturation does not occur in the iron core of motor 1, the winding inductance of motor 1 becomes large, and the amplitude of the current flowing through motor 1 becomes small.

[0027] Thus, when a pulse voltage is applied to the motor 1, the degree of magnetic saturation in the iron core of the motor 1 differs 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, if we set the aforementioned integer n of 2 or more to 6, that is, the 360° electrical angle of the motor 1 is divided into 6 parts, and a periodic pulse voltage with a pulse peak at every 60° interval is applied to the motor 1. In this case, the voltage waveform will be as shown in Figure 2. In this case, the amplitude of each pulse voltage in the αβ axis 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 flowing through motor 1 in synchronization with this pulse voltage is as shown in Figure 2. At this time, the amplitude of the αβ axis current Iαβ flowing through 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 motor 1 has resistance and inductance components, the amplitude of the current expressed in equations (3) and (4) actually appears as a first-order lag response determined by the electrical time constant. Here, if the magnitude V of the voltage in equations (1) and (2) is fixed, the current flowing through motor 1 can be changed by changing the pulse width of the pulse voltage.

[0033] In other words, the current increases according to the electrical time constant determined by the inductance and resistance of motor 1. If the pulse width of the pulse voltage is small, that is, if the duration of application of one pulse voltage is short, the voltage application ends before the first-order lag response converges, and the current amplitude becomes small because the first-order lag response does not persist. On the other hand, if the pulse width of the pulse voltage is large, that is, if the duration of application of one pulse voltage is long, the first-order lag response persists, and the current amplitude becomes large. Thus, as the pulse width of the applied voltage increases, the current amplitude also increases accordingly. Furthermore, as the current amplitude increases, the magnetic flux generated by it increases, 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 generation unit 3. In this example, a pulse width of 1 means that the voltage command generation unit 3 generates a voltage command with a width of one sampling period. A pulse width of 2 means that the voltage command generation unit 3 generates a voltage command with a width of two sampling periods. The same applies to pulse widths of 3, 4, ...

[0035] Next, the sum of the current values ​​Iα and Iβ corresponding to the application of pulse voltages Vα and Vβ is expressed by equations (5) and (6) below. 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°). 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 we assume that the current amplitude I remains constant at each electrical angle, then the terms in equation (5) cancel each other 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 we assume that the current amplitude I remains constant at each electrical angle, then the terms in equation (6) also cancel each other out, and ΣIβ=0.

[0038] However, ΣIα=ΣIβ=0 only occurs when the current amplitude I remains constant and equal at each electrical angle, as mentioned above. Here, when magnetic saturation occurs, the inductance of motor 1 decreases, making it easier for current to flow and increasing the current amplitude I. That is, 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, there is a term in equation (5) that does not cancel out, and ΣIα≠0. Similarly, there is a term in equation (6) that does not cancel out, and ΣIβ≠0. The specific electrical angle θ at which such magnetic saturation occurs can be found in the following equation (7).

[0039] θ=arctan(ΣIβ / ΣIα) ··· (7)

[0040] As is clear from the explanation above, the following two conditions can be given for the current amplitude I to become large. The difference between the phase (electrical angle) of the pulse voltage applied to motor 1 and the phase (electrical angle) of the magnetic pole position of the rotor of 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 maximized when a pulse voltage is applied with a peak at the electrical angle where the difference between the electric angle and the magnetic pole position of motor 1 is smallest. 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 where the maximum current amplitude I occurs (the electrical angle closest to the magnetic pole position). Therefore, when the pulse width of the periodic pulse voltage applied to motor 1 is changed while keeping the amplitude constant, or more specifically, when the pulse width is gradually increased from the minimum, magnetic saturation first occurs when a pulse voltage with a peak at the electrical angle where the maximum current amplitude I occurs (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 determined 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, a larger pulse width of the pulse voltage allows more current to flow, which is advantageous for estimating the magnetic pole position. However, if too much current flows, it may damage the power converter 5 and other hardware. Therefore, setting the pulse width is important. If the characteristics of the motor 1 are known, the pulse width can be determined in advance by calculating the electrical time constant beforehand, which allows for an estimate of how much current flows in how long. On the other hand, if the characteristics of the motor 1 are unknown, the pulse width cannot be determined in advance, so detection of magnetic saturation is necessary for estimating the magnetic pole position θ using equation (7). Furthermore, if magnetic saturation can be detected, the magnetic pole position θ can be estimated using equation (7) without calculating the electrical time constant and pulse width beforehand, even if the characteristics of the motor 1 are known.

[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 using the amplitude of the current detected by the current sensor 6 when the magnetic saturation detection unit 8 detects magnetic saturation.

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

[0046] Next, the detection of magnetic saturation of the motor 1 by the magnetic saturation detection unit 8 will be explained. Figures 3 and 4 show examples of the absolute values ​​of the detected current at each electrical angle when the pulse width of the pulse voltage applied to the motor 1 is changed, when the magnetic pole position is around an electrical angle of 300°.

[0047] First, with respect to the α axis, |cos(0°)|=|cos(180°)|=1 and |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, so |Iα1|=|Iα4| and |Iα2|=|Iα3|=|Iα5|=|Iα6|. On the other hand, if magnetic saturation occurs around the electrical angle of 300° where the magnetic pole is located because the pulse width is large and the current value is large, the current amplitude I around the electrical angle of 300° becomes large, so |Iα1|=|Iα4| and |Iα2|=|Iα3|=|Iα5|≠|Iα6|. Thus, the magnetic saturation detection unit 8 can detect the magnetic saturation of the motor 1 by detecting this difference in current.

[0048] Similarly, for the β axis, if 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, if the pulse width is large and magnetic saturation occurs around the electrical angle of 300° where the magnetic pole is located, the current amplitude I around the electrical angle of 300° becomes large, so |Iβ1|=|Iβ4| and |Iβ2|=|Iβ3|=|Iβ5|≠|Iβ6|. The magnetic saturation detection unit 8 can detect the magnetic saturation of the motor 1 by detecting this difference in current.

[0049] However, the current value detected by the current sensor 6 contains detection errors. Furthermore, variations in the resistance and inductance of each phase of the motor 1, and variations in the voltage applied to each phase by the power converter 5 are also possible. Due to these factors, the current amplitude I at a specific electrical angle may change independently of magnetic saturation, and the absolute value of the current at that specific electrical angle may change. Therefore, the magnetic saturation detection unit 8 may detect magnetic saturation of the motor 1 when the difference between the current amplitudes corresponding to peaks at different electrical angles of pulse voltage is greater than or equal to a preset first reference value. The first reference value can be appropriately set according to, for example, the rated current of the motor 1, the rated current of the power converter 5, etc.

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

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

[0052] The magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the motor 1 if any of these differences are greater than or equal to the first reference value. In the example shown in Figure 3, when the pulse width exceeds 8, i.e., when the pulse width becomes 9, |Iα2|-|Iα6|, |Iα3|-|Iα6|, and |Iα5|-|Iα6| become greater than or equal to 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 Figure 4, when the pulse width exceeds 8, i.e., when the pulse width becomes 9, |Iβ2|-|Iβ6|, |Iβ3|-|Iβ6|, and |Iβ5|-|Iβ6| become greater than or equal to 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 of magnetic saturation may be performed using the current values ​​of both the α axis and the β axis, or it may be performed using the current value of only one of the α axis or the β axis.

[0053] Next, with reference to the flowchart in Figure 5, an example of the magnetic saturation detection and magnetic pole position determination process in the control device 100 of the electric motor 1 according to this embodiment will be described. When the control device 100 starts estimating the magnetic pole position and detecting magnetic saturation of the electric motor 1, 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 to the motor 1 in response to the pulse voltage applied in step S001. Once the pulse voltage has been applied for a full 360° rotation of electrical angle, 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 greater than or equal to a first reference value. If the difference between the absolute values ​​of the currents corresponding to each electrical angle is not greater than or equal to the first reference value, the control device 100 performs the process in step S005, 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 S001 to continue processing, applies the pulse voltage again, and repeats the processes in steps S002 and S003.

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

[0056] The control device 100 for the motor 1, configured as described above, can detect magnetic saturation 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, and based on the magnitude of the current value at each electrical angle. Then, the magnetic pole position can be estimated from the current value at the time of magnetic saturation detection. For this reason, even if the characteristics of the target motor 1 are unknown, it is possible to estimate the magnetic pole position with high accuracy.

[0057] Next, some modifications of the magnetic saturation detection in the control device 100 of the electric motor 1 according to this embodiment will be described. First, a first modification of the magnetic saturation detection will be described with reference to Figures 6 and 7. In this first modification, the magnetic saturation detection unit 8 calculates the sum of the amplitudes of the current flowing through the electric motor 1 on each axis, corresponding to the peaks at different electrical angles of the pulse voltage applied to the electric motor 1. The magnetic saturation detection unit 8 then detects magnetic saturation of the electric motor 1 when the sum of the squares of the sums of the current amplitudes on each axis is equal to or greater than a preset second reference value.

[0058] Figure 6 shows an example of the sum of the squares of the sum of the current amplitudes in each axis when the pulse width of the pulse voltage applied to the motor 1 is changed, when the magnetic pole position is around an electrical angle of 300°. First, for the α axis, if magnetic saturation does not occur because the pulse width is small and the current value is small, then, as mentioned above, the current amplitude I is equal at each electrical angle, 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 around an electrical angle of 300° where the magnetic pole position is located, the current amplitude I around an electrical angle of 300° becomes large, and |Iα1|=|Iα4| and |Iα2|=|Iα3|=|Iα5|≠|Iα6|. Therefore, ΣIα≠0.

[0059] Similarly, for the β axis, if we assume that the current amplitude I remains constant 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 around an electrical angle of 300° where the magnetic pole is located, the current amplitude I around an electrical angle of 300° becomes 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 motor 1 if the sum of the squares of the sum of the currents for each electrical angle in the α axis ΣIα and the sum of the currents for each electrical angle in the β axis ΣIβ ((ΣIα)^2 + (ΣIβ)^2) is equal to or greater than a preset second reference value. The second reference value can be appropriately set according to, for example, the rated current of the motor 1, the rated current of the power converter 5, etc. It should be noted that using the square root of the sum of the squares of ΣIα and ΣIβ instead of the sum of the squares of ΣIα and ΣIβ is substantially the same. In this sense, in this disclosure, the square root of the sum of the squares of ΣIα and ΣIβ may simply be 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, that is, 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 a pulse width of 9.

[0061] Next, with reference to the flowchart in Figure 7, an example of the magnetic saturation detection and magnetic pole position determination process in a first modified example of the control device 100 for the electric motor 1 according to this embodiment will be described. When the control device 100 starts estimating the magnetic pole position and detecting magnetic saturation of the electric motor 1, first in step S101, 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.

[0062] In the following step S102, the current sensor 6 detects the amplitude of the current flowing to the motor 1 in response to the pulse voltage applied in step S101. Once the pulse voltage has been applied for a full 360° rotation in electrical angle, in step S103, the magnetic saturation detection unit 8 uses the current amplitude obtained in step S102 to determine whether the sum of the squares of the sum of the currents at each electrical angle in the α axis ΣIα and the sum of the squares of the currents at each electrical angle in the β axis ΣIβ is greater than or equal to the second reference value. If the sum of the squares of ΣIα and ΣIβ is not greater than or equal to the second reference value, the control device 100 performs the process in 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 processing, applies the pulse voltage again, and repeats the processes in steps S102 and S103.

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

[0064] Even with the first modified configuration of the control device 100 as described above, it is possible to accurately estimate the magnetic pole position even if the characteristics of the target electric motor 1 are unknown. Furthermore, with this first modified configuration, magnetic saturation can be determined by processing the data uniformly, rather than by determining the current value for each coordinate axis.

[0065] Next, a second modified example of magnetic saturation detection will be described with reference to Figures 8 and 9. In this second modified example, the magnetic saturation of the motor 1 is detected using the magnetic pole position estimated by the magnetic pole position estimation unit 9. More specifically, the voltage application unit described above gradually increases the pulse width while maintaining a constant amplitude of the pulse voltage applied to the motor 1. The magnetic saturation detection unit 8 then detects magnetic saturation of the motor 1 when the difference in the magnetic pole position 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 motor 1 is less than or equal to a preset 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 then detects magnetic saturation of the motor 1 when the change in the magnetic pole position estimated by the magnetic pole position estimation unit 9 remains below the third reference value for multiple consecutive times as the pulse width is gradually increased.

[0066] If magnetic saturation does not occur and there is no change in current amplitude at a specific electrical angle, or if current detection errors 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 pronounced than current detection errors. As a result, the estimated magnetic pole position stabilizes, and the estimated magnetic pole position no longer changes 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, and if, for example, the estimated magnetic pole position does not change for multiple consecutive times, or more specifically, if the estimated magnetic pole position remains within the third reference value for multiple consecutive times, 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. When the pulse width is small and magnetic saturation does not occur, accurate magnetic pole position estimation cannot be performed, the estimated magnetic pole position changes each time the pulse width is changed. This corresponds to pulse widths from 1 to 5 in Figure 8. In contrast, when the pulse width is large and magnetic saturation occurs, accurate magnetic pole position estimation can be performed, the estimated magnetic pole position does not change much even when the pulse width is changed. This corresponds to pulse widths of 6 or more in Figure 8.

[0068] Whether or not magnetic saturation has occurred can be determined, for example, by checking whether the difference ((θm+1)-(θm)) between the estimated magnetic pole value θm at pulse width m and the estimated magnetic pole value θm+1 at pulse width m+1 is less than or equal to a third reference value. In the example in Figure 8, the difference (θ3-θ2) between the estimated magnetic pole value θ2 at pulse width 2 and the estimated magnetic pole 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 estimated magnetic pole value θ6 for pulse width 6 and the estimated magnetic pole value θ7 for pulse width 7 is within the reference value, it is determined that magnetic saturation has occurred, and therefore the magnetic pole estimation result is determined to be stable. Furthermore, since the difference between the estimated magnetic pole value θ7 for pulse width 7 and the estimated magnetic pole value θ8 for pulse width 8 is also below the third reference value, it is determined that magnetic saturation has occurred. In this way, if a situation in which magnetic saturation is determined to have occurred occurs multiple times in a row, it may be determined that the magnetic pole position has been accurately estimated, and the magnetic pole position may be finalized.

[0070] Next, with reference to the flowchart in Figure 9, an example of the magnetic saturation detection and magnetic pole position determination process in a second modified example of the control device 100 for the electric motor 1 according to this embodiment will be described. When the control device 100 starts estimating the magnetic pole position and detecting magnetic saturation of the electric motor 1, first in step S201, 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.

[0071] In the following step S202, the current sensor 6 detects the amplitude of the current flowing through the motor 1 in response to the pulse voltage applied in step S201. Once the pulse voltage has been applied for a full 360° rotation in electrical angle, 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 processing in step S203. In step S203, the magnetic saturation detection unit 8 determines whether the difference between the previous estimate of the magnetic pole position by the magnetic pole position estimation unit 9 and the current estimate of the magnetic pole position by the magnetic pole position estimation unit 9 is less than or equal to the third reference value. If the difference between the previous and current estimates of the magnetic pole position is not less than or equal to the third reference value, the control device 100 performs the process in step S205, 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. Then, the control device 100 returns to step S201 and continues processing, applying the pulse voltage again and repeating the processes in steps S202 and S203.

[0072] On the other hand, if the difference between the previous and current estimated magnetic pole positions in step S203 is less than or equal to the third reference value, the magnetic saturation detection unit 8 detects that magnetic saturation has occurred in the motor 1. In this case, the control device 100 then proceeds to 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. Upon receiving the magnetic saturation detection signal, the magnetic pole position estimation unit 9 outputs the magnetic pole position estimated this time as the confirmed value of the magnetic pole position of the motor 1. Once the processing in step S204 is completed, the series of processes is finished.

[0073] Even with the second modified configuration of the control device 100 as described above, it is possible to accurately estimate the magnetic pole position even if the characteristics of the target electric motor 1 are unknown. Furthermore, with this second modified configuration, the accuracy of detecting magnetic saturation can be improved by utilizing the fact that when magnetic saturation occurs, the change in the estimated magnetic pole position becomes small even if the pulse width changes.

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

[0075] Furthermore, the magnetic saturation detection unit 8 may store the pulse width of the applied voltage when it detects magnetic saturation of the motor 1. In this case, when estimating the magnetic pole position in subsequent cycles, the magnetic saturation detection unit 8 may output a command signal to the voltage command generation unit 3 to generate a voltage command using the pulse width stored from the previous magnetic saturation detection. 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 motor 1. In this way, for example, when it is necessary to estimate the magnetic pole position each time the motor 1 is powered on or each time control of the motor 1 is started, detecting magnetic saturation only the first time is sufficient, and thereafter, a voltage with a pulse width that generates magnetic saturation can be applied to the motor 1 without having to detect magnetic saturation again.

[0076] The voltage command generation unit 3 may output a voltage command Vuvw* in a three-phase AC coordinate system instead of a voltage command Vαβ in a two-phase AC coordinate system. In this case, the voltage coordinate converter 4 is not required. The magnetic saturation detection unit 8 may also detect whether or not magnetic saturation is occurring in the motor 1 using the current Iuvw in a three-phase AC coordinate system instead of the current Iαβ in a two-phase AC coordinate system. Similarly, the magnetic pole position estimation unit 9 may estimate the magnetic pole position of the motor 1 using the current Iuvw in a three-phase AC coordinate system instead of the current Iαβ in a 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 where the peak of the pulse voltage applied to the motor 1 is located is not limited to the 6 example explained above. In other words, it is not limited to cases where the peak interval of the pulse voltage is an electrical angle of 60°. The number of divisions n = 12, meaning the peak interval is an electrical angle of 30°, or the number of divisions n = 24, meaning the peak interval is an electrical angle of 15°. Note that the larger the number of divisions n, the higher the resolution of the estimated magnetic pole position can be.

[0078] Figure 10 shows an example of a configuration that realizes the functions of the control device 100 in this embodiment. The functions of the control device 100 are realized, for example, by a processing circuit. The processing circuit may include a processor 101 and a memory 102. The processing circuit may also include 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. Also, in the example shown in the figure, the processing circuit further includes a processor 101 and a memory 102.

[0079] A processing circuit that is partly a dedicated hardware component 103 may include, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. If the processing circuit includes at least one processor 101 and at least one memory 102, the functions of the control device 100 are 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. The processor 101 reads and executes the programs stored in memory 102 to realize the functions of each part. The processor 101 is also called a CPU (Central Processing Unit), central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP. Examples of memory 102 include non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, and EEPROM, or magnetic disks, flexible disks, optical disks, compact disks, minidiscs, and DVDs.

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

[0082] In this disclosure, the embodiments may be combined in any way without departing from the spirit of this disclosure. Examples of various embodiments of this disclosure are summarized below as an appendix. (Note 1) A control device for a permanent magnet synchronous motor, A voltage application unit that applies a periodic pulse voltage with a peak at an electrical angle of 360° / n (where n is an integer of 2 or more) to the permanent magnet synchronous motor, A current detection unit that detects the amplitude of the current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage, A magnetic pole position estimation unit that estimates the magnetic pole position of the permanent magnet synchronous motor using the amplitude of the current, The system includes a magnetic saturation detection unit that detects the 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 is a control device for an electric motor that estimates the magnetic pole position using the amplitude of the current when the magnetic saturation detection unit detects magnetic saturation. (Note 2) The control device for a motor according to Appendix 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when the difference between the absolute values ​​of the currents corresponding to the peaks at different electrical angles of the pulse voltage is greater than or equal to a preset first reference value. (Note 3) The magnetic saturation detection unit is The sum of the amplitudes of the current corresponding to the peaks at different electrical angles of the pulse voltage is calculated along each axis. The motor control device according to Appendix 1, which detects magnetic saturation of the permanent magnet synchronous motor when the sum of the squares of the sums in each shaft is equal to or greater than a preset second reference value. (Note 4) The voltage application unit gradually increases the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant. The control device for a motor according to Appendix 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when the difference between the magnetic pole position estimated by the magnetic pole position estimation unit using the current amplitude after the increase in pulse width and the magnetic pole position estimated by the magnetic pole position estimation unit using the current amplitude before the increase in pulse width is less than or equal to a preset third reference value. (Note 5) The magnetic pole position estimation unit estimates the magnetic pole position when the permanent magnet synchronous motor is being braked by the brake, The control device for an electric motor according to any one of the appendices 1 to 4, wherein the magnetic saturation detection unit detects the magnetic saturation of the permanent magnet synchronous motor when the permanent magnet synchronous motor is being braked by a brake. (Note 6) When the magnetic saturation detection unit detects magnetic saturation in the permanent magnet synchronous motor, it stores the pulse width of the pulse voltage applied to the permanent magnet synchronous motor. The control device for an electric motor according to any one of the appendices 1 to 5, wherein the voltage application unit applies the pulse voltage of the pulse width stored in the magnetic saturation detection unit to the permanent magnet synchronous electric motor. [Explanation of Symbols]

[0083] 1 electric motor 2. Brake 3. Voltage command generation unit 4 Voltage Coordinate Converter 5 Power Converters 6 Current Sensor 7 Current Coordinate Converter 8 Magnetic saturation detection unit 9 Magnetic pole position estimation section 100 Control device 101 Processors 102 memory 103 Dedicated Hardware

Claims

1. A control device for a permanent magnet synchronous motor, A voltage application unit that applies a periodic pulse voltage with a peak at an electrical angle of 360° / n (where n is an integer of 2 or more) to the permanent magnet synchronous motor, A current detection unit that detects the amplitude of the current flowing through the permanent magnet synchronous motor in synchronization with the pulse voltage, A magnetic pole position estimation unit that estimates the magnetic pole position of the permanent magnet synchronous motor using the amplitude of the current, The system includes a magnetic saturation detection unit that detects the 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 is a control device for an electric motor that estimates the magnetic pole position using the amplitude of the current when the magnetic saturation detection unit detects magnetic saturation.

2. The control device for an electric motor according to claim 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous electric motor when the difference between the absolute values ​​of the currents corresponding to the peaks at different electrical angles of the pulse voltage is greater than or equal to a preset first reference value.

3. The magnetic saturation detection unit is The sum of the amplitudes of the current corresponding to the peaks at different electrical angles of the pulse voltage is calculated along each axis. The motor control device according to claim 1, which detects magnetic saturation of the permanent magnet synchronous motor when the sum of the squares of the sums in each shaft is equal to or greater than a preset second reference value.

4. The voltage application unit gradually increases the pulse width of the pulse voltage while maintaining the amplitude of the pulse voltage constant. The control device for a motor according to claim 1, wherein the magnetic saturation detection unit detects magnetic saturation of the permanent magnet synchronous motor when the difference between the magnetic pole position estimated by the magnetic pole position estimation unit using the current amplitude after the increase in pulse width and the magnetic pole position estimated by the magnetic pole position estimation unit using the current amplitude before the increase in pulse width is less than or equal to a preset third reference value.

5. The magnetic pole position estimation unit estimates the magnetic pole position when the permanent magnet synchronous motor is being braked by the brake, The control device for an electric motor according to any one of claims 1 to 4, wherein the magnetic saturation detection unit detects the magnetic saturation of the permanent magnet synchronous motor when the permanent magnet synchronous motor is being braked by a brake.

6. When the magnetic saturation detection unit detects magnetic saturation in the permanent magnet synchronous motor, it stores the pulse width of the pulse voltage applied to the permanent magnet synchronous motor. The control device for an electric motor according to any one of claims 1 to 4, wherein the voltage application unit applies the pulse voltage of the pulse width stored in the magnetic saturation detection unit to the permanent magnet synchronous electric motor.

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