Motor control method

Abstract

The present disclosure relates to a motor control method, comprising the following steps: adjusting a voltage component of an estimated voltage command to a steady-state voltage value; performing a coordinate transformation on another voltage component of the estimated voltage command and the steady-state voltage value, and generating three-phase excitation currents to rotate a synchronous motor to a rotation position and stop; calculating an estimated current signal; when it is determined that a current component does not maintain a steady-state current value, calculating an estimated value of the rotation position and adjusting another voltage component of the estimated voltage command; when it is determined that the current component maintains the steady-state current value, calculating an effective inductance of the synchronous motor based on the steady-state voltage value, another voltage component of the estimated voltage command, the steady-state current value, and another current component of the estimated current signal.

Description

Technical Field

[0001] The present disclosure relates to a motor control method, particularly for calculating the inductance of a permanent magnet assisted synchronous reluctance motor. Background Art

[0002] When driving a motor without a position sensor (or encoder), a large number of motor parameters are required to estimate the shaft angle in order to accurately drive the motor. In traditional technologies, an inverter for driving a motor generates a corresponding stator magnetic field by appropriately controlling the stator current of the motor, and keeps the stator magnetic field and the rotor magnetic field orthogonal to maintain high-efficiency operation. Generally, a traditional control device estimates the position of the rotor of the motor based on the drive voltage, drive current, and motor parameters, and appropriately adjusts the control command according to the rotor position to keep the directions of the stator magnetic field and the rotor magnetic field orthogonal to each other. Therefore, how to correctly calculate the parameters of the motor has become an important issue.

[0003] Among them, in the field of motor control, the inductance of the motor (including: direct-axis inductance and quadrature-axis inductance) is a very important motor parameter. Among them, a permanent magnet assisted synchronous reluctance motor (PMaSynRM, hereinafter referred to as a reluctance motor) is a motor that uses both permanent magnet materials and magnetic conductive materials (such as silicon steel sheets, etc.) as the rotor structure of the motor. However, due to the characteristics of the rotor structure of this motor, the inductance of the motor is related to the rotor position. Under the traditional inductance parameter self-learning method, it is difficult to accurately align the rotor position of the reluctance motor with the set angle, so it is difficult to accurately calculate the inductance of the motor. Therefore, for the current traditional technologies, it is difficult to accurately calculate the inductance of the reluctance motor (such as direct-axis inductance, quadrature-axis inductance). Summary of the Invention

[0004] The present disclosure provides a motor control method for calculating the inductance of a motor. Thereby, the foregoing problems are solved.

[0005] The present disclosure relates to a motor control method for a sensorless synchronous motor. The motor control method includes: adjusting a voltage component of an estimated voltage command to a steady-state voltage value; performing a coordinate transformation on another voltage component of the estimated voltage command and the steady-state voltage value to generate a two-axis voltage command; generating three-phase excitation currents according to a DC excitation voltage command and the two-axis voltage command to drive the synchronous motor to rotate to a rotation position and stop; obtaining the three-phase excitation currents to calculate an estimated current signal, wherein a current component of the estimated current signal corresponds to the steady-state voltage value; when it is determined that the current component does not maintain at the steady-state current value, calculating an estimated value of the rotation position according to the estimated current signal; according to the estimated value of the rotation position, adjusting another voltage component of the estimated voltage command so that the current component corresponding to the steady-state voltage value maintains at the steady-state current value; when it is determined that the current component maintains the steady-state current value, calculating an effective inductance of the synchronous motor according to the steady-state voltage value, another voltage component of the estimated voltage command, the steady-state current value, and another current component of the estimated current signal.

[0006] The present disclosure also relates to a motor control method for a synchronous motor. A position sensor is coupled to the synchronous motor. The motor control method includes: adjusting a voltage component of an estimated voltage command to a steady-state voltage value; performing a coordinate transformation on another voltage component of the estimated voltage command and the steady-state voltage value to generate a two-axis voltage command; generating three-phase excitation currents according to a DC excitation voltage command and the two-axis voltage command to drive the synchronous motor to rotate to a rotation position and stop; obtaining the three-phase excitation currents to calculate an estimated current signal, wherein a current component of the estimated current signal corresponds to the steady-state voltage value; when it is determined that the current component does not maintain at the steady-state current value, obtaining a measured value of the rotation position through the position sensor; according to the measured value of the rotation position, adjusting another voltage component of the estimated voltage command so that the current component corresponding to the steady-state voltage value maintains at the steady-state current value; when it is determined that the current component maintains the steady-state current value, calculating an effective inductance of the synchronous motor according to the steady-state voltage value, another voltage component of the estimated voltage command, the steady-state current value, and another current component of the estimated current signal.

[0007] The present disclosure estimates the position of the rotor of the motor according to a feedback current signal containing angle error information, and adjusts the angle of the estimated coordinate axis according to the estimated rotor position, and accordingly corrects the voltage vector for inductance measurement until the position error between the estimated coordinate and the rotation position of the rotor converges within the error range. Accordingly, the motor control device can estimate the motor parameters at the correct rotor position according to the corrected estimated coordinate axis, so as to facilitate the precise control of the synchronous motor. Description of the Drawings

[0008] Figure 1A It is a schematic diagram of coordinate transformation shown according to the traditional technology.

[0009] Figure 1B Schematic diagram of coordinate conversion according to some embodiments of the present disclosure.

[0010] Figure 2 Schematic diagram of a motor control device according to some embodiments of the present disclosure.

[0011] Figure 3A Flowchart of a motor control method according to some embodiments of the present disclosure.

[0012] Figure 3B Flowchart of a method for generating three-phase excitation current according to some embodiments of the present disclosure.

[0013] Figure 4 Schematic diagram of a motor control device according to some embodiments of the present disclosure.

[0014] Figure 5A Flowchart of a motor control method according to some embodiments of the present disclosure.

[0015] Figure 5B Flowchart of a method for generating three-phase excitation current according to some embodiments of the present disclosure.

[0016] Description of reference numerals:

[0017] 100: Motor control device

[0018] 110: Control arithmetic unit

[0019] 111: Coordinate converter

[0020] 112: Inductance arithmetic unit

[0021] 120: Drive arithmetic unit

[0022] 121: Two-phase to three-phase converter

[0023] 122: PWM modulation circuit

[0024] 130: Feedback arithmetic unit

[0025] 131: Current sensing processing unit

[0026] 132: Three-phase to two-phase converter

[0027] 133: Position estimator

[0028] 140: Position sensor

[0029] 200: Synchronous motor

[0030] 210: Rotor

[0031] 220: Stator

[0032] Vδ: Estimated direct-axis voltage

[0033] Vγ: Estimated quadrature-axis voltage

[0034] Vdc: DC excitation voltage command

[0035] Vα: First voltage component

[0036] Vβ: Second voltage component

[0037] Vt: Excitation drive voltage

[0038] Va-Vc: Three-phase drive voltage

[0039] Ia~Ic: Three-phase excitation current

[0040] Ia_ac: Feedback AC signal component

[0041] Ib_ac: Feedback AC signal component

[0042] Ic_ac: Feedback AC signal component

[0043] Iδ: Estimated direct-axis current

[0044] Iγ: Estimated quadrature-axis current

[0045] Θv: Estimated value

[0046] Θm: Measured value

[0047] Θer: Angle error

[0048] Ld: Direct-axis inductance

[0049] Lq: Quadrature-axis inductance

[0050] 300, 500: Motor control method

[0051] S301-S308: Steps

[0052] S3031-S3034: Steps

[0053] S501-S508: Steps

[0054] S5031-S5034: Steps

[0055]

Biological material deposit

[0056] Domestic deposit information (Please note in the order of deposit institution, date, number)

[0057] None

[0058] Overseas deposit information (Please note in the order of country, institution, date, and number of deposit)

[0059] None Detailed implementation manners

[0060] The following will disclose multiple embodiments of the present invention with the accompanying drawings. For the sake of clear description, many practical details will be described together in the following narration. However, it should be understood that these practical details should not be used to limit the present invention. That is to say, in some embodiments of the present invention, these practical details are not necessary. In addition, for the sake of simplifying the accompanying drawings, some conventional structures and elements will be shown in a simple schematic manner in the accompanying drawings.

[0061] Figure 1A It is a schematic diagram of coordinate axis conversion shown according to traditional technologies. In the general field of motor control (including the control of reluctance motors), the motion state of a motor is represented by coordinate axis conversion operations, such as Figure 1A shown. Generally speaking, the d-axis and the q-axis are synchronous coordinate axes used to represent the rotor position of the motor. Therefore, when the rotational speed of the reluctance motor is zero, the synchronous coordinate axes of the reluctance motor are represented by Equation (1) as follows:

[0062]

[0063] In Equation (1), Vd represents the d-axis voltage, Vq represents the q-axis voltage, id represents the d-axis current, iq represents the q-axis current, Ld represents the d-axis inductance, Lq represents the q-axis inductance, and rs represents the stator resistance of the reluctance motor.

[0064] As Figure 1A shown, the δ-axis and the γ-axis are estimated coordinate axes used to represent the set rotor position of the motor (usually the rotor position recognized by a computer or a controller) or the estimated rotor position. The α-axis and the β-axis are stationary coordinate axes used to represent the stator position of the motor. The a-axis, the b-axis, and the c-axis represent the three-phase coordinate axes of the motor.

[0065] Due to the structural characteristics of the reluctance motor, when controlling the rotor of the reluctance motor to stop, when Θa represents the actual position Θa of the rotor of the motor (or the angle difference between the d-axis of the synchronous coordinate axes and the a-axis of the three-phase coordinate axes), there is an obvious angle error between the estimated coordinate axes and the synchronous coordinate axes. Therefore, when converting Equation (1) to the estimated coordinate axes, Equation (2) can be obtained as follows:

[0066]

[0067] In Equation (2), Vδ represents the δ-axis voltage, Vγ represents the γ-axis voltage, iδ represents the δ-axis current, iγ represents the γ-axis current, Ld represents the d-axis inductance, Lq represents the q-axis inductance, rs represents the stator resistance of the reluctance motor, and Θer represents the angular error between the motor synchronous coordinate axis and the estimated coordinate axis.

[0068] As can be seen from Equation (2), since the synchronous coordinate axis representing the motor rotor is not aligned with the estimated coordinate axis, Equation (2) includes the component of the actual position Θa. In the case of a sensorless situation, it is difficult to obtain the actual position Θa of the rotor. Therefore, traditional sensorless motor control methods cannot accurately estimate the d-axis inductance Ld (or direct-axis inductance Ld) and q-axis inductance (or quadrature-axis inductance Lq) of the reluctance motor, resulting in a significant reduction in the control efficiency of the motor. As Figure 1B shown, the present disclosure proposes a motor control device and its control method. By calculating the estimated value Θv of the actual position Θa of the rotor, the positions of the estimated coordinate axes (δ-axis and γ-axis) are adjusted to reduce the component of the actual rotor position Θa. Thereby, the above problems are solved. Although there is an angular error Θer between the estimated value Θv and the actual position Θa of the rotor, the present disclosure can make the angular error Θer approach zero by adjusting the estimated value Θv. The implementation method of the present disclosure will be described in detail below.

[0069] Figure 2 FIG. 100 is a schematic diagram of a motor control device 100 according to some embodiments of the present disclosure. The motor control device 100 is applied to a synchronous motor 200 without a position sensor installed. It should be noted in particular that the synchronous motor 200 refers to a magnet-assisted synchronous reluctance motor, but the present disclosure is not limited thereto.

[0070] The motor control device 100 (or variable frequency drive) includes a control arithmetic unit 110, a drive arithmetic unit 120, and a feedback arithmetic unit 130. Among them, the control arithmetic unit 110 is used to receive the estimated voltage commands (including the estimated direct-axis voltage Vδ and the estimated quadrature-axis voltage Vγ), and generate two-axis voltage commands (including the first voltage component Vα and the second voltage component Vβ) based on them to the drive arithmetic unit 120. According to the two-axis voltage commands, the drive arithmetic unit 120 provides three-phase exciting currents Ia, Ib, and Ic to the synchronous motor 200. The feedback arithmetic unit 130 acquires the three-phase exciting currents Ia, Ib, and Ic of the synchronous motor 200. Then, the feedback arithmetic unit 130 generates a feedback signal to the control arithmetic unit 110 based on the three-phase exciting currents Ia, Ib, and Ic. The control arithmetic unit 110 calculates the direct-axis inductance or quadrature-axis inductance of the synchronous motor 200 based on the aforementioned feedback signal. In this embodiment, the two-axis voltage commands (Vα, Vβ) represent the stationary coordinate axes. Therefore, the first voltage component Vα is also called the α-axis voltage of the stationary coordinate axes, and the second voltage component Vβ is also called the β-axis voltage of the stationary coordinate axes. However, the present disclosure is not limited thereto. It should be particularly noted that in one embodiment, the estimated direct-axis voltage Vδ, the estimated quadrature-axis voltage Vγ, the first voltage component Vα, and the second voltage component Vβ are all high-frequency AC signals. However, the present disclosure is not limited thereto.

[0071] Please refer to the following Figure 2 , Figure 3A and Figure 3B to illustrate the various embodiments of the present disclosure. The present disclosure proposes a motor control method 300, and the motor control method 300 is applicable to the synchronous motor 200 without a position sensor. The motor control method 300 is executed by the motor control device 100, and the motor control method 300 includes: steps S301 to S308. In addition, step S303 further includes: steps S3031 to S3034.

[0072] In step S301, the control arithmetic unit 110 adjusts one voltage component of the estimated voltage commands (including: the estimated direct-axis voltage Vδ and the estimated quadrature-axis voltage Vγ) to a steady-state voltage value. As Figure 2 shown, in order to calculate the quadrature-axis inductance Lq more accurately, the control arithmetic unit 110 can adjust the estimated direct-axis voltage Vδ to a steady-state voltage value and maintain the estimated quadrature-axis voltage Vγ as a high-frequency AC signal. Or, in order to calculate the direct-axis inductance Ld more accurately, the control arithmetic unit 110 can adjust the estimated quadrature-axis voltage Vγ to a steady-state voltage value and maintain the estimated direct-axis voltage Vδ as a high-frequency AC signal. In a preferred embodiment, the steady-state voltage value can be designed to be zero. However, the present disclosure is not limited thereto.

[0073] In step S302, another voltage component of the estimated voltage command and the steady-state voltage value are subjected to coordinate conversion to generate a two-axis voltage command. For example, as Figure 2 shown, the control arithmetic unit 110 includes a coordinate converter 111 and an inductor arithmetic unit 112, and the control arithmetic unit 110 adjusts the estimated quadrature-axis voltage Vγ to the steady-state voltage value and maintains the estimated direct-axis voltage Vδ as a high-frequency AC signal (the estimated direct-axis voltage Vδ is regarded as another voltage component of the estimated voltage command). The coordinate converter 111 performs coordinate conversion on the estimated direct-axis voltage Vδ and the steady-state voltage value to generate the first voltage component Vα and the second voltage component Vβ of the two-axis voltage command. Then, the control arithmetic unit 110 provides the first voltage component Vα and the second voltage component Vβ to the drive arithmetic unit 120. In this embodiment, the estimated direct-axis voltage Vδ and the estimated quadrature-axis voltage Vγ represent the estimated coordinate axes, and the first voltage component Vα and the second voltage component Vβ represent the stationary coordinate axes, but the present disclosure is not limited thereto.

[0074] Next, the calculation of the direct-axis inductance Ld is used as an example of coordinate conversion. As Figure 2 and Figure 3A shown, in order to accurately calculate the direct-axis inductance Ld, the control arithmetic unit 110 receives the estimated direct-axis voltage Vδ and the estimated quadrature-axis voltage Vγ of the estimated voltage command, and the control arithmetic unit 110 adjusts the estimated quadrature-axis voltage Vγ to zero (i.e., the steady-state voltage value in step S301), as shown in Equation (3):

[0075]

[0076] In Equation (3), V S sinωt is the high-frequency AC signal received by the control arithmetic unit 110 and is regarded as the estimated direct-axis voltage Vδ. Then, according to Equation (3) for coordinate conversion, the first voltage component Vα and the second voltage component Vβ of the two-axis voltage command can be obtained, as shown in Equation (4):

[0077]

[0078] In Equation (4), θv is the estimated value of the rotational position. It should be noted that when the program is executed for the first time, since the estimated value Θv of the rotational position is not obtained through feedback, but is a preset value in the program of the coordinate converter 111 or a position command from the outside. Therefore, the coordinate converter 111 performs coordinate conversion based on the estimated direct-axis voltage Vδ and the steady-state voltage value of the estimated voltage command to obtain the first voltage component Vα and the second voltage component Vβ of the two-axis voltage command.

[0079] Similarly, in other preferred embodiments of step S302, in order to accurately calculate the quadrature-axis inductance Lq, the control operation unit 110 receives the estimated direct-axis voltage Vδ and the estimated quadrature-axis voltage Vγ of the estimated voltage command, and the control operation unit 110 adjusts the estimated direct-axis voltage Vδ to zero (i.e., the steady-state voltage value in step S301). Then, the coordinate converter 111 performs coordinate conversion based on the estimated quadrature-axis voltage Vγ of the estimated voltage command and the steady-state voltage value to obtain the first voltage component Vα and the second voltage component Vβ of the two-axis voltage command. Since the equation principle of this embodiment can be obtained by modifying equations (3) and (4), the present disclosure will not be described in detail herein.

[0080] In step S303, after the driving operation unit 120 receives the first voltage component Vα and the second voltage component Vβ output by the coordinate converter 111, the driving operation unit 120 generates three-phase exciting currents Ia, Ib, and Ic according to the DC exciting voltage command Vdc and the two-axis voltage command (including the first voltage component Vα or the second voltage component Vβ) to drive the synchronous motor 200 to rotate to the rotation position and stop. It should be particularly noted that regarding the rotation position of the synchronous motor 200 (i.e., the actual position Θa of the rotor 210), since no position sensor is used in this embodiment, the motor control device 200 cannot directly obtain the actual value of the rotation position.

[0081] Please refer to Figure 2 , Figure 3A and Figure 3B simultaneously to illustrate the operation mode of step S303 in detail. Step S303 includes steps S3031 to S3034. In step S3031, the driving operation unit 120 selects one of the first voltage component Vα and the second voltage component Vβ as the first driving command. In step S3032, the other one of the first voltage component Vα and the second voltage component Vβ is selected as the second driving command. For example: if the first voltage component Vα is selected as the first driving command, then the second voltage component Vβ is selected as the second driving command. Similarly, if the second voltage component Vβ is selected as the first driving command, then the first voltage component Vα is selected as the second driving command.

[0082] In step S3033, the driving operation unit 120 superimposes the DC exciting voltage command Vdc and the first driving command to generate the exciting driving voltage Vt. In step S3034, the driving operation unit 120 generates three-phase exciting currents Ia, Ib, and Ic according to the exciting driving voltage Vt and the second driving command.

[0083] For example: If the first voltage component Vα is selected as the first driving command, the driving arithmetic unit 120 superimposes the DC exciting voltage command Vdc and the first voltage component Vα. Then, the second voltage component Vβ is selected as the second driving command. Therefore, the driving arithmetic unit 120 arranges Equation (4) and the DC exciting voltage command Vdc to obtain Equation (5) as follows:

[0084]

[0085] In Equation (5), Vt is the exciting driving voltage. After the driving arithmetic unit arranges Equations (3), (4), and (5), Equation (6) can be obtained as follows:

[0086]

[0087] Referring to Equation (6), the driving arithmetic unit 120 generates three-phase exciting currents Ia, Ib, and Ic based on the exciting driving voltage Vt and the second voltage component Vβ (i.e., the second driving command).

[0088] Similarly, in steps S3033 and S3034, if the second voltage component Vβ is selected as the first driving command, the driving arithmetic unit 120 superimposes the DC exciting voltage command Vdc and the second voltage component Vβ. Then, in step S3034, the driving arithmetic unit 120 generates three-phase exciting currents Ia, Ib, and Ic based on the exciting driving voltage Vt and the first voltage component Vα (i.e., the second driving command). In this embodiment, those skilled in the art can modify Equations (5) and (6) to obtain the exciting driving voltage Vt and generate three-phase exciting currents Ia, Ib, and Ic. Therefore, the present disclosure will not repeat the description.

[0089] It should be noted that the Figure 2 is only used to describe the example where the first voltage component Vα is selected as the first driving command, and the driving arithmetic unit 120 superimposes the DC exciting voltage command Vdc and the first voltage component Vα. To simplify the description of the present disclosure, the example where the second voltage component Vβ is selected as the first driving command, and the driving arithmetic unit 120 superimposes the DC exciting voltage command Vdc and the second voltage component Vβ will not be repeatedly depicted.

[0090] In step S303, the driving arithmetic unit 120 generates three-phase exciting currents Ia, Ib, and Ic to drive the synchronous motor 200 to rotate to the rotation position and stop. As Figure 2As shown, the driving arithmetic unit 120 includes a two-phase to three-phase converter 121 and a PWM modulation circuit 122. Among them, after the two-phase to three-phase converter 121 receives the exciting drive voltage Vt and the second voltage component Vβ (i.e., the second drive command), the two-phase to three-phase converter 121 generates three-phase voltages Va, Vb, and Vc. The PWM modulation circuit 122 switches the three-phase voltages Va, Vb, and Vc to generate three-phase currents Ia, Ib, and Ic. Alternatively, in other embodiments, after the two-phase to three-phase converter 121 receives the exciting drive voltage Vt and the first voltage component Vα (i.e., the second drive command), the two-phase to three-phase converter 121 generates three-phase voltages Va, Vb, and Vc. The PWM modulation circuit 122 switches the three-phase voltages Va, Vb, and Vc to generate three-phase currents Ia, Ib, and Ic.

[0091] In some embodiments, the purpose of the driving arithmetic unit 120 receiving the DC exciting voltage command Vdc is to make the torque output by the synchronous motor 200 zero, so that the synchronous motor 200 stops at the set rotation position. Generally, the torque equation of the synchronous motor is as shown in Equation (7):

[0092]

[0093] In Equation (7), τ e is the torque output by the synchronous motor, P is the number of poles of the synchronous motor, i q is the quadrature-axis current of the synchronous coordinate axis, i d is the direct-axis current of the synchronous coordinate axis, Ld represents the direct-axis inductance, Lq represents the quadrature-axis inductance, and λ m is the rotor flux equivalent to the stator flux.

[0094] Converting Equation (7) to the stationary coordinate axes (α-axis and β-axis) and assuming the estimated value θv is zero degree, Equation (8) can be obtained as follows:

[0095]

[0096] In Equation (8), the control device of a general synchronous motor can control the rotor of the synchronous motor to rotate to a rotational position and stop according to the DC excitation voltage. Therefore, in the present disclosure, the synchronous motor 200 (reluctance motor) can also apply the same aforementioned principle to make the rotor of the synchronous motor 200 rotate to a rotational position and stop. In addition, it can be seen from Equation (8) that based on the structural characteristics of the reluctance motor, the direct-axis inductance Ld of the reluctance motor is different from the quadrature-axis inductance Lq. Therefore, the output torque in Equation (8) includes the electromagnetic torque generated by the magnet component and the reluctance torque generated by the inductance difference (Ld, Lq). When DC excitation is performed (step S303), due to the synthesis of the two different torques, when the torque is zero, the angle between the estimated coordinate axes (δ-axis, γ-axis) and the actual synchronous coordinate axes (d-axis and q-axis) is not zero.

[0097] In step S304, the feedback operation unit 130 acquires the three-phase excitation currents Ia, Ib, and Ic, and establishes an estimated coordinate axis based on the three-phase excitation currents Ia, Ib, and Ic to calculate the estimated current signals (including: estimated direct-axis current Iδ and estimated quadrature-axis current Iγ), wherein one current component of the estimated current signals corresponds to the steady-state voltage value. It should be particularly noted that since the estimated voltage command and the estimated current signals are on the same estimated coordinate axis and the motor has been stopped (step S303), the estimated direct-axis current Iδ corresponds to the estimated direct-axis voltage Vδ, and the estimated quadrature-axis current Iγ corresponds to the estimated quadrature-axis voltage Vγ. If the angle error Θer ( Figure 1B ) is very small, the estimated coordinate axes (δ-axis, γ) and the synchronous coordinate axes (d-axis, q-axis) can be regarded as aligned. When the estimated coordinate axes and the synchronous coordinate axes are aligned, the estimated quadrature-axis current Iγ corresponding to the steady-state voltage value (i.e., when the estimated quadrature-axis voltage Vγ is adjusted to the steady-state voltage value) is the frequency of the high-frequency AC signal where the similar estimated direct-axis voltage Vδ cannot be observed. Therefore, the estimated quadrature-axis current Iγ is maintained at the steady-state current value. On the contrary, if the angle error Θer ( Figure 1B ) is very large, the estimated coordinate axes (δ-axis, γ) and the synchronous coordinate axes (d-axis, q-axis) are not aligned. When the estimated coordinate axes and the synchronous coordinate axes are not aligned, the estimated quadrature-axis current Iγ corresponding to the steady-state voltage value (i.e., when the estimated quadrature-axis voltage Vγ is adjusted to the steady-state voltage value) observes the frequency of the high-frequency AC signal where the similar estimated direct-axis voltage Vδ can be obtained.

[0098] Particularly noteworthy is that if the motor is not stopped, there will be a coupling quantity between the estimated voltage command and the estimated current signal, so that the estimated direct-axis current Iδ cannot accurately correspond to the estimated direct-axis voltage Vδ, and the estimated quadrature-axis current Iγ cannot accurately correspond to the estimated quadrature-axis voltage Vγ. Therefore, if the control operation unit 110 adjusts the estimated quadrature-axis voltage Vγ to the steady-state voltage value (step S301), the estimated quadrature-axis current Iγ corresponds to the steady-state voltage value. Conversely, if the control operation unit 110 adjusts the estimated direct-axis voltage Vδ to the steady-state voltage value (step S301), the estimated direct-axis current Iδ corresponds to the steady-state voltage value.

[0099] As Figure 2 shown, the feedback operation unit 130 includes a current sensing processing unit 131, a three-phase to two-phase converter 132, and a position estimator 133. Among them, the current sensing processing unit 131 obtains the AC components of the three-phase exciting currents Ia, Ib, and Ic, and outputs the feedback AC signal components Ia_ac to Ic_ac to the three-phase to two-phase converter 132.

[0100] The three-phase to two-phase converter 132 establishes an estimated coordinate axis based on the feedback AC signal components Ia_ac to Ic_ac to calculate the estimated current signals (Iδ, Iγ). Since the operating principle of the three-phase to two-phase converter 132 is well-known to those skilled in the art, it will not be elaborated in this disclosure. In some embodiments, the current sensing processing unit 131 includes a plurality of current sensors (not shown), and each of the plurality of current sensors is used to obtain the feedback AC signal components Ia_ac to Ic_ac.

[0101] In step S305, the position estimator 133 determines whether the current component corresponding to the steady-state voltage value remains at the steady-state current value. Theoretically, if the control operation unit 110 adjusts the estimated quadrature-axis voltage Vγ to the steady-state voltage value (step S301), the estimated quadrature-axis current Iγ should remain at the steady-state current value. Conversely, if the control operation unit 110 adjusts the estimated direct-axis voltage Vδ to the steady-state voltage value (step S301), the estimated direct-axis current Iδ should remain at the steady-state current value.

[0102] However, as Figure 1AAs shown, due to the angular error between the synchronous coordinate axis (used to represent the actual position of the rotor) and the estimated coordinate axis (i.e., the actual position Θa of the rotor), the current component corresponding to the steady-state voltage value contains a high-frequency AC signal and cannot be maintained at the steady-state current value. For example, if the control operation unit 110 adjusts the estimated quadrature-axis voltage Vγ to the steady-state voltage value, the estimated quadrature-axis current Iγ contains a high-frequency AC signal. Similarly, if the control operation unit 110 adjusts the estimated direct-axis voltage Vδ to the steady-state voltage value, the estimated direct-axis current Iδ contains a high-frequency AC signal. If the position estimator 133 determines that the current component (estimated direct-axis current Iδ or estimated quadrature-axis current Iγ) corresponding to the steady-state voltage value is not maintained at the steady-state current value, the motor control device 100 proceeds to step S306.

[0103] In step S306, the position estimator 133 calculates the estimated value Θv of the rotational position of the synchronous motor 200 based on the estimated current signals (Iδ and Iγ) and provides it to the control operation unit 110 and the three-phase to two-phase converter 132. Among them, the three-phase to two-phase converter 132 adjusts the estimated direct-axis current Iδ and the estimated quadrature-axis current Iγ of the estimated current signal according to the estimated value Θv to improve the accuracy of the estimated value Θv.

[0104] As mentioned above, the position estimator 133 calculates the estimated value Θv of the rotational position of the synchronous motor 200 based on the estimated direct-axis current Iδ or the estimated quadrature-axis current Iγ. The calculation method is referenced from: Chen, J., Tseng, S., & Liu, T. (2012). Implementation of high-performance sensorless interior permanent-magnet synchronous motor control systems using a high-frequency injection technique. IET Electric Power Applications, 6(8), 533. doi: 10.1049 / iet-epa.2011.0303. Therefore, the calculation method is not elaborated in this disclosure, but this disclosure is not limited thereto.

[0105] In step S307, the control operation unit 110 adjusts another voltage component of the estimated voltage command based on the estimated value Θv of the rotational position, so that the current component corresponding to the steady-state voltage value is maintained at the steady-state current value. For example, when the control operation unit 110 adjusts the estimated direct-axis voltage Vδ to the steady-state voltage value, the control operation unit 110 adjusts the estimated quadrature-axis voltage Vγ based on the estimated value Θv of the rotational position, so that the estimated direct-axis current Iδ corresponding to the steady-state voltage value is maintained at the steady-state current value.

[0106] Alternatively, in other embodiments, when the control arithmetic unit 110 adjusts the estimated quadrature-axis voltage Vγ to the steady-state voltage value, the control arithmetic unit 110 adjusts the estimated direct-axis voltage Vδ according to the estimated value Θv of the rotational position, so that the estimated quadrature-axis current Iγ corresponding to the corresponding steady-state voltage value is maintained at the steady-state current value. When the motor control device 100 completes step S307, the motor control device 100 returns to step S305: the position estimator 133 determines whether the current component corresponding to the steady-state voltage value is maintained at the steady-state current value.

[0107] Wherein when the position estimator 133 determines that the current component corresponding to the steady-state voltage value maintains the steady-state current value, the motor control device 100 enters step S308.

[0108] In step S308, the control arithmetic unit 110 calculates the effective inductance (direct-axis inductance Ld or quadrature-axis inductance Lq) of the synchronous motor according to the steady-state voltage value, another voltage component of the estimated voltage command, the steady-state current value, and another current component of the estimated current signal. Please refer to Table 1 below to illustrate the calculation method for adjusting each parameter:

[0109]

[0110] Table 1

[0111] As can be seen from Table 1 above, if the control arithmetic unit 110 selects the estimated quadrature-axis voltage Vγ as the voltage component to be adjusted to the steady-state voltage value (i.e., when the estimated quadrature-axis voltage Vγ is adjusted to the steady-state voltage value), then: another voltage component of the estimated voltage command is the estimated direct-axis voltage Vδ; the current component corresponding to the steady-state voltage value is the estimated quadrature-axis current Iγ; another current component of the estimated current signal is the estimated direct-axis current Iδ; and the calculated effective inductance is the direct-axis inductance Ld.

[0112] If the control arithmetic unit 110 selects the estimated direct-axis voltage Vδ as the voltage component to be adjusted to the steady-state voltage value (i.e., when the estimated direct-axis voltage Vδ is adjusted to the steady-state voltage value), then: another voltage component of the estimated voltage command is the estimated quadrature-axis voltage Vγ; the current component corresponding to the steady-state voltage value is the estimated direct-axis current Iδ; another current component of the estimated current signal is the estimated quadrature-axis current Iγ; and the calculated effective inductance is the quadrature-axis inductance Lq.

[0113] In a preferred embodiment, the steady-state voltage value is zero, but the present disclosure is not limited thereto. It should be noted in particular that, in step S303, the drive arithmetic unit adds the DC excitation command Vdc to the stationary coordinate axes (Vα, Vβ). Due to the factor of the DC excitation command Vdc, when the estimated quadrature-axis voltage Vγ is adjusted to zero, the estimated quadrature-axis current Iγ maintains a non-zero steady-state current value. Similarly, due to the factor of the DC excitation command Vdc, when the estimated direct-axis voltage Vδ is adjusted to zero, the estimated direct-axis current Iδ maintains a non-zero steady-state current value.

[0114] Figure 4 FIG. is a schematic diagram of a motor control device according to some embodiments of the present disclosure. Figure 5A FIG. is a flowchart of a motor control method according to some embodiments of the present disclosure. Figure 5B FIG. is a flowchart of a method for generating three-phase excitation currents according to some embodiments of the present disclosure. Please refer to Figure 4 、 Figure 5A and Figure 5B as well, to illustrate the following various embodiments.

[0115] The present disclosure provides a motor control method 500, and the motor control method 500 is applicable to a synchronous motor 200 with a position sensor 140 (e.g., an encoder), and the position sensor 140 is coupled to the synchronous motor 200. The motor control method 500 is executed by the motor control device 100, and the motor control method 500 includes: steps S501 to S508.

[0116] Among them, the operation methods of steps S501 to S505 are the same as those of steps S301 to S305. Therefore, the present disclosure will not repeat them.

[0117] In step S506, the position sensor 140 measures the rotational position of the rotor 210 of the synchronous motor 200 and outputs the measured value Θm to the position estimator 133 of the feedback arithmetic unit 130. Therefore, the position estimator 133 of the feedback arithmetic unit 130 obtains the measured value Θm of the rotational position through the position sensor 140. Then, the position estimator 133 outputs the measured value Θm of the rotational position to the control arithmetic unit 110. In addition, when the motor control device 100 executes step S506, the feedback arithmetic unit 130 still obtains the feedback AC signal components Ia_ac to Ic_ac of the three-phase excitation currents Ia to Ic of the synchronous motor 200 to calculate the estimated current signals (Iδ, Iγ) (the same as step S304, so it will not be repeated).

[0118] It should be noted in particular that, depending on different situations, the position sensor 140 can be disposed inside or outside the motor control device 100, but the present disclosure is not limited thereto.

[0119] In step S507, the control arithmetic unit 110 adjusts another voltage component of the estimated voltage command according to the measured value Θm of the rotational position, so that the current component of the corresponding steady-state voltage value is maintained at the steady-state current value (the method is similar to step S307). The operation methods of steps S507 to S508 are the same as those of steps S307 and S308. Therefore, the details are not described again in this disclosure.

[0120] Therefore, in the synchronous motor 200 with the position sensor 140, the motor control device 100 can also calculate the direct-axis inductance or quadrature-axis inductance of the synchronous motor 200 according to the steps shown in FIG. 3 when the current component of the corresponding steady-state voltage value is maintained at the steady-state current value. The motor control device 100 measures the rotational position of the synchronous motor 200 through the position sensor 140, rather than evaluating the rotational position of the synchronous motor 200 through the estimated current signals (Iδ, Iγ). Therefore, in this embodiment, the motor control device 100 can omit complex calculations and can more effectively reduce the influence caused by the actual position Θa of the rotor.

[0121] In summary, the key point of this disclosure is to calculate the excitation angle value according to the estimated voltage command, and control the rotor of the synchronous motor 200 to rotate to the rotational position and stop. Then, by detecting or calculating the rotor position of the synchronous motor 200, the position error between the rotor position and the excitation angle value is reduced. In this way, this disclosure can calculate the direct-axis inductance or quadrature-axis inductance of the synchronous motor 200 more accurately.

[0122] The various elements, method steps or technical features in the foregoing embodiments can be combined with each other, without being limited by the order of the text description or the order of the figures in the content of the present invention.

[0123] Although the content of the present invention has been disclosed as above in the form of embodiments, it is not intended to limit the content of the present invention. Any person skilled in the art can make various changes and modifications without departing from the concept and scope of the content of the present invention. Therefore, the protection scope of the content of the present invention shall be subject to what is defined by the claims.

Claims

1. A motor control method for a synchronous motor without a position sensor, wherein the motor control method comprises: Adjusting a voltage component of an estimated voltage command to a steady-state voltage value; Performing a coordinate axis transformation on another voltage component of the estimated voltage command and the steady-state voltage value to generate a two-axis voltage command; Generating a three-phase exciting current according to a DC exciting voltage command and the two-axis voltage command to drive the synchronous motor to rotate to a rotation position and stop; Obtaining the three-phase exciting current to calculate an estimated current signal, wherein a current component of the estimated current signal corresponds to the steady-state voltage value; When it is determined that the current component does not maintain at a steady-state current value, calculating an estimated value of the rotation position according to the estimated current signal; Adjusting the another voltage component of the estimated voltage command according to the estimated value of the rotation position, so that the current component corresponding to the steady-state voltage value maintains at the steady-state current value; And When it is determined that the current component maintains the steady-state current value, calculating an effective inductance of the synchronous motor according to the steady-state voltage value, the another voltage component of the estimated voltage command, the steady-state current value and another current component of the estimated current signal.

2. The motor control method according to claim 1, wherein the two-axis voltage command includes a first voltage component and a second voltage component, and the motor control method further comprises: Selecting one of the first voltage component and the second voltage component as a first driving command; Selecting the other of the first voltage component and the second voltage component as a second driving command; Superimposing the DC exciting voltage command and the first driving command to generate an exciting driving voltage; And Generating the three-phase exciting current according to the exciting driving voltage and the second driving command.

3. The motor control method according to claim 1, wherein the estimated voltage command includes an estimated direct-axis voltage and an estimated quadrature-axis voltage, and the estimated current signal includes an estimated direct-axis current and an estimated quadrature-axis current.

4. The motor control method according to claim 3, further comprising: Adjusting the estimated direct-axis current and the estimated quadrature-axis current of the estimated current signal according to the estimated value of the rotation position.

5. The motor control method according to claim 3, wherein the estimated quadrature-axis voltage of the estimated voltage command is adjusted to the steady-state voltage value, the another voltage component of the estimated voltage command is the estimated direct-axis voltage; the current component corresponding to the steady-state voltage value is the estimated quadrature-axis current; the another current component of the estimated current signal is the estimated direct-axis current; and the effective inductance is a direct-axis inductance.

6. The motor control method according to claim 3, wherein the estimated direct-axis voltage of the estimated voltage command is adjusted to the steady-state voltage value, the another voltage component of the estimated voltage command is the estimated quadrature-axis voltage; the current component corresponding to the steady-state voltage value is the estimated direct-axis current; the another current component of the estimated current signal is the estimated quadrature-axis current; and the effective inductance is a quadrature-axis inductance.

7. The motor control method according to claim 1, wherein the steady-state voltage value is zero.

8. A motor control method for a synchronous motor, wherein a position sensor is coupled to the synchronous motor, and the motor control method includes: Adjusting a voltage component of an estimated voltage command to a steady-state voltage value; Performing a coordinate transformation on another voltage component of the estimated voltage command and the steady-state voltage value to generate a two-axis voltage command; Generating a three-phase exciting current according to a DC exciting voltage command and the two-axis voltage command to drive the synchronous motor to rotate to a rotation position and stop; Obtaining the three-phase exciting current to calculate an estimated current signal, wherein a current component of the estimated current signal corresponds to the steady-state voltage value; When it is determined that the current component does not maintain at a steady-state current value, obtaining a measurement value of the rotation position through the position sensor; Adjusting the another voltage component of the estimated voltage command according to the measurement value of the rotation position, so that the current component corresponding to the steady-state voltage value maintains at the steady-state current value; And When it is determined that the current component maintains the steady-state current value, calculating an effective inductance of the synchronous motor according to the steady-state voltage value, the another voltage component of the estimated voltage command, the steady-state current value and another current component of the estimated current signal.

9. The motor control method according to claim 8, wherein the two-axis voltage command includes a first voltage component and a second voltage component, and the motor control method further includes: Selecting one of the first voltage component and the second voltage component as a first driving command; Selecting the other of the first voltage component and the second voltage component as a second driving command; Superposing the DC exciting voltage command and the first driving command to generate an exciting driving voltage; And Generating the three-phase exciting current according to the exciting driving voltage and the second driving command.

10. The motor control method according to claim 8, wherein the estimated voltage command includes an estimated direct-axis voltage and an estimated quadrature-axis voltage, and the estimated current signal includes an estimated direct-axis current and an estimated quadrature-axis current.

11. The motor control method according to claim 10, further includes: Adjusting the estimated direct-axis current and the estimated quadrature-axis current of the estimated current signal according to the measurement value of the rotation position.

12. The motor control method according to claim 10, wherein the estimated quadrature-axis voltage of the estimated voltage command is adjusted to the steady-state voltage value, the another voltage component of the estimated voltage command is the estimated direct-axis voltage; the current component corresponding to the steady-state voltage value is the estimated quadrature-axis current; the another current component of the estimated current signal is the estimated direct-axis current; and the effective inductance is a direct-axis inductance.

13. The motor control method according to claim 10, wherein the estimated direct-axis voltage of the estimated voltage command is adjusted to the voltage component of the steady-state voltage value, the another voltage component of the estimated voltage command is the estimated quadrature-axis voltage; the current component corresponding to the steady-state voltage value is the estimated direct-axis current; the another current component of the estimated current signal is the estimated quadrature-axis current; and the effective inductance is a quadrature-axis inductance.

14. The motor control method according to claim 8, wherein the steady-state voltage value is zero.

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