A method and system for detecting the initial position of a rotor of a permanent magnet synchronous motor

Abstract

The present invention belongs to the technical field of permanent magnet synchronous motor drive control, and specifically provides a method and system for detecting the initial position of the rotor of a permanent magnet synchronous motor, including the following steps: designing a waveform voltage with an injection period of T, respectively injecting a forward voltage and a reverse voltage with a voltage amplitude of U2 in the two time periods of T2-T3 and T3-T4, and respectively injecting a forward voltage and a reverse voltage with a voltage amplitude of U1 in the two time periods of T1-T2 and T4-T5; injecting a waveform voltage; collecting the feedback current of the d-axis when the forward voltage is injected at different angles; selecting the direction with the maximum absolute value of the slope of the d-axis current change as the true d-axis direction, and then performing polarity judgment to obtain the initial angle position of the rotor. The scheme can quickly determine the initial position angle of the motor in a stationary state for product control, and the accuracy of the initial angle judgment can be selected according to the specific product requirements, thereby solving the reversal and startup failure caused by the transition of the motor from zero speed to low speed.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet synchronous motor drive control, and more specifically, to a method and system for detecting an initial position of a rotor of a permanent magnet synchronous motor. Background Art

[0002] The d-axis is the direct axis in the motor, and the q-axis is the quadrature axis. The center line of the rotor pole in the synchronous motor is the direct axis direction, and the perpendicular bisector between two adjacent poles is the quadrature axis direction. There are many methods for detecting the initial position of the rotor when it is stationary, such as high-frequency pulse injection, high-frequency rotating voltage injection, etc. Most of these methods rely on the motor dq-axis inductance parameters. When the motor inductance is very small or the motor salient polarity is very small, these methods may fail to converge or converge inaccurately in the stationary state, but the position angle can be accurately predicted after the motor rotates, which will cause debugging difficulties in industrial product manufacturing. Summary of the invention

[0003] The present invention aims to solve the technical problem in the prior art that the initial position of a motor in a stationary state is inaccurately judged, thereby causing reverse rotation and starting failure when the motor transitions from zero speed to low speed.

[0004] The present invention provides a method for detecting an initial position of a rotor of a permanent magnet synchronous motor, comprising the following steps:

[0005] S1, design a waveform voltage with an injection period of T, where the waveform period T includes four time periods: T1-T2, T2-T3, T3-T4 and T4-T5;

[0006] S2, inject a forward voltage and a reverse voltage with a voltage amplitude of U2 in the two time periods T2-T3 and T3-T4, respectively, and inject a forward voltage and a reverse voltage with a voltage amplitude of U1 in the two time periods T1-T2 and T4-T5;

[0007] S3, selecting an injection angle interval to form an injection angle group, selecting different angle intervals within the injection angle group, and sequentially injecting waveform voltages according to the same voltage injection method as in step S2; collecting feedback currents of the d-axis when the forward voltage is injected at different angles;

[0008] S4, select the direction with the maximum absolute value of the d-axis current change slope as the true d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

[0009] Preferably, the S2 further comprises: within the time period 0-T1, the voltage amplitude Ud injected on the d-axis is equal to U2, and the q-axis injected voltage Uq is set to 0 to clear the excitation magnetic field.

[0010] Preferably, S2 specifically includes: determining the current sampling accuracy according to the product accuracy requirements, and determining the selection of the later injection voltage amplitude U2 according to the current sampling accuracy;

[0011] The voltage setting standard of U2 is:

[0012] When the voltage is injected, the motor disturbance is within the allowable range, and at the same time, the sampling current size is ensured not to trigger the motor's overcurrent protection. The d-axis current rise amplitude in each sampling cycle can be accurately collected by the sampling circuit.

[0013] Preferably, the numerical value of U1 is one tenth of the numerical value of U2.

[0014] Preferably, the S3 specifically includes:

[0015] When collecting the feedback current of the d-axis, the current difference between two adjacent current sampling points is greater than the sampling accuracy.

[0016] Preferably, the S4 specifically includes:

[0017] S41, selecting the direction with the maximum absolute value of the slope of the d-axis current change as the reference direction for the next round of injection, and taking the angle interval of half of the corresponding injection angle interval A as the interval for the next round of injection, and then repeating step S3 to perform waveform voltage injection;

[0018] S42, selecting the direction with the maximum absolute value of the d-axis current change slope in all waveform voltage injection groups as the true d-axis direction, and then performing polarity judgment to obtain the initial angular position of the rotor.

[0019] Preferably, the S4 specifically includes:

[0020] After obtaining the actual d-axis direction, the polarity is judged. If it is positive, it is used as the initial angular position of the rotor. If it is reverse, π needs to be added as the initial angular position of the rotor.

[0021] The present invention also provides a permanent magnet synchronous motor rotor initial position detection system, the system is used to implement a permanent magnet synchronous motor rotor initial position detection method, comprising:

[0022] The waveform voltage design module is used to design a waveform voltage with an injection period of T, where the waveform period T includes four time periods, namely, T1-T2, T2-T3, T3-T4 and T4-T5;

[0023] In the two time periods T2-T3 and T3-T4, a forward voltage and a reverse voltage with a voltage amplitude of U2 are respectively injected, and in the two time periods T1-T2 and T4-T5, a forward voltage and a reverse voltage with a voltage amplitude of U1 are respectively injected;

[0024] The waveform voltage injection module is used to select an injection angle interval to form an injection angle group, select different angle intervals within the injection angle group, and sequentially inject the waveform voltage according to the same voltage injection method in step S2; collect the feedback current of the d-axis when the forward voltage is injected at different angles;

[0025] The initial angle judgment module is used to select the direction with the maximum absolute value of the d-axis current change slope as the real d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

[0026] The present invention also provides an electronic device, comprising a memory and a processor, wherein the processor is used to implement the steps of a method for detecting the initial position of a rotor of a permanent magnet synchronous motor when executing a computer management program stored in the memory.

[0027] The present invention also provides a computer-readable storage medium on which a computer management program is stored. When the computer management program is executed by a processor, the steps of the method for detecting the initial position of the rotor of a permanent magnet synchronous motor are implemented.

[0028] Beneficial effect: The present invention provides a method and system for detecting the initial position of the rotor of a permanent magnet synchronous motor, comprising the following steps: designing a waveform voltage with an injection period of T, wherein the waveform period T includes four time periods, namely T1-T2, T2-T3, T3-T4 and T4-T5; injecting a forward voltage and a reverse voltage with a voltage amplitude of U2 in the two time periods of T2-T3 and T3-T4, respectively, and injecting a forward voltage and a reverse voltage with a voltage amplitude of U1 in the two time periods of T1-T2 and T4-T5; selecting an injection angle interval to form a group of injection angle groups, selecting different angle intervals in the injection angle group, and sequentially injecting waveform voltages according to the same voltage injection method in step S2; collecting the feedback current of the d-axis when the forward voltage is injected at different angles; selecting the direction with the maximum absolute value of the slope of the d-axis current change as the true d-axis direction, and then performing polarity judgment to obtain the initial angle position of the rotor. This solution can quickly determine the initial position angle of the motor when it is stationary for product control, and the accuracy of the initial angle judgment can be selected according to specific product requirements, thereby solving the reversal and starting failure caused by the transition from zero speed to low speed of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A waveform injection principle diagram of a method for detecting the initial position of a rotor of a permanent magnet synchronous motor provided by the present invention;

[0030] Figure 2 A schematic diagram of the hardware structure of a possible electronic device provided by the present invention;

[0031] Figure 3A schematic diagram of the hardware structure of a possible computer-readable storage medium provided by the present invention;

[0032] Figure 4 This is a relationship diagram between the waveform voltage injection direction d1-q1 coordinate system provided by the present invention and the real dq coordinate system. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0034] like Figure 1 As shown, a method for detecting the initial position of a rotor of a permanent magnet synchronous motor provided by an embodiment of the present invention comprises the following steps:

[0035] S1, design a waveform voltage with an injection period of T, where the waveform period T includes four time periods: T1-T2, T2-T3, T3-T4 and T4-T5;

[0036] S2, inject a forward voltage and a reverse voltage with a voltage amplitude of U2 in the two time periods T2-T3 and T3-T4, respectively, and inject a forward voltage and a reverse voltage with a voltage amplitude of U1 in the two time periods T1-T2 and T4-T5;

[0037] S3, selecting an injection angle interval to form an injection angle group, selecting different angle intervals within the injection angle group, and sequentially injecting waveform voltages according to the same voltage injection method as in step S2; collecting feedback currents of the d-axis when the forward voltage is injected at different angles;

[0038] S4, select the direction with the maximum absolute value of the d-axis current change slope as the true d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

[0039] This solution can quickly determine the initial position angle of the motor when it is stationary for product control, and the accuracy of the initial angle judgment can be selected according to specific product requirements, thereby solving the reversal and starting failure caused by the transition from zero speed to low speed of the motor.

[0040] In a specific implementation scenario:

[0041] The first step is to determine the current sampling accuracy according to the product accuracy requirements, and determine the selection of the later injection voltage amplitude, that is, the preset value U2, according to the current sampling accuracy. Specifically, first determine whether the waveform time t is less than T1. If it is less than T1, that is, in the time period of 0-T1, select the d-axis injection voltage amplitude Ud=U2, and artificially set the q-axis injection voltage Uq to 0, which is used to clear the excitation magnetic field and improve the judgment accuracy.

[0042] Among them, the selection of U2 should be determined according to the rated input voltage of the motor. The selection criteria are that the motor disturbance cannot be large when the voltage is injected, and at the same time, the sampling current size will not trigger the motor's overcurrent protection. The d-axis current rise amplitude in each sampling cycle can be accurately collected by the sampling circuit.

[0043] The third step is to determine U2 and make an injection judgment according to the designed injection waveform. The waveform voltage with an injection period of T is designed, and the waveform period T includes four time periods, namely, T1-T2, T2-T3, T3-T4 and T4-T5.

[0044] Specifically, a forward voltage and a reverse voltage with a voltage amplitude of U2 are respectively injected in the two time periods T2-T3 and T3-T4, and a forward voltage and a reverse voltage with a voltage amplitude of U1 are respectively injected in the two time periods T1-T2 and T4-T5, and the feedback current of the d-axis is collected.

[0045] In the time period T1-T2, a voltage with an amplitude of U1 is injected. The function of U1 is to generate a relatively small excitation magnetic field to enhance the salient polarity of the motor and ensure that the initial value of the collected current is within a normal range, which can reduce the interference caused by the sampling accuracy. The selection of U1 should not be too large. It is generally selected to be about one tenth of U2.

[0046] In the T2-T3 stage, a voltage excitation with an amplitude of U2 is injected, and the d-axis feedback current is collected in this stage. The selection of U2 should be determined based on the rated input voltage of the motor. The selection criteria are that the motor disturbance cannot be large when the voltage is injected, and at the same time, the sampling current size will not trigger the motor's overcurrent protection. The d-axis current rise amplitude in each sampling cycle can be accurately collected by the sampling circuit.

[0047] In the T3-T4 stage, a reverse waveform is injected to offset the excitation magnetic field caused by voltage injection, reduce motor disturbance, and improve the accuracy of judgment.

[0048] like Figure 4 As shown, in the fourth step, the injection angle interval is selected to form a group of injection angle groups, and different angles within the injection angle group are selected to perform the same voltage injection method (d-axis forward injection followed by reverse equal-amplitude voltage injection of the same time), that is, the waveform voltage is injected in sequence according to the same voltage injection method in the third step.

[0049] The fifth step is to collect the d-axis feedback current when the forward voltage is injected at different angles. The larger the absolute value of the d-axis current change slope, the closer the injection direction (d1 axis) is to the true d-axis direction.

[0050] The preferred solution is to change the d-axis excitation amplitude according to the waveform voltage over time while collecting the motor current, observing the current change curve, ensuring that the current difference between adjacent sampling points is greater than the sampling accuracy and that the sampled current has an obvious change curve.

[0051] Step 6: Angle approach.

[0052] First, select the direction with the maximum absolute value of the d-axis current change slope as the reference direction for the next round of injection, and use the angle interval of half the corresponding injection angle interval A as the interval for the next round of injection, and then repeat the fourth step to perform waveform voltage injection. By selecting the direction with the maximum absolute value of the d-axis current change slope as the reference direction for the next round of injection, this step is called the first angle estimation.

[0053] Specifically, an angle interval of half the injection angle interval A corresponding to the reference direction is selected as the interval, and the same voltage is injected in the upper and lower directions of the direction angle A and in the direction of the reference direction angle A.

[0054] Then, the direction with the maximum absolute value of the d-axis current change slope in all waveform voltage injection groups is selected as the true d-axis direction, and then the polarity is judged to obtain the initial angular position of the rotor.

[0055] The direction with the largest absolute value of the d-axis current change slope is selected as the reference direction for the next round of injection. This step can be repeated according to actual design requirements until the design goal is met.

[0056] The seventh step is to determine the polarity of the actual d-axis direction. If it is positive, it is used as the initial angular position of the rotor. If it is reverse, π needs to be added as the initial angular position of the rotor.

[0057] The present invention relates to the field of permanent magnet synchronous motor drive control, and can assist a high-frequency injection method and other sensorless control technologies in determining an initial position. In industrial design, when a motor is in a stationary state and the sensorless control technology is used to determine the initial position, when the angle convergence is inaccurate, the motor will fail to start. The method mentioned in the present invention is used to determine the initial angle of the motor in a stationary state and then assist other sensorless control methods in realizing the normal starting of the motor. The method does not require a position sensor and can be combined with other sensorless control schemes to improve the accuracy of the control system.

[0058] The embodiment of the present invention further provides a permanent magnet synchronous motor rotor initial position detection system, the system is used to implement a permanent magnet synchronous motor rotor initial position detection method, including:

[0059] The waveform voltage design module is used to design a waveform voltage with an injection period of T, where the waveform period T includes four time periods, namely, T1-T2, T2-T3, T3-T4 and T4-T5;

[0060] In the two time periods T2-T3 and T3-T4, a forward voltage and a reverse voltage with a voltage amplitude of U2 are respectively injected, and in the two time periods T1-T2 and T4-T5, a forward voltage and a reverse voltage with a voltage amplitude of U1 are respectively injected;

[0061] The waveform voltage injection module is used to select an injection angle interval to form an injection angle group, select different angle intervals within the injection angle group, and sequentially inject the waveform voltage according to the same voltage injection method in step S2; collect the feedback current of the d-axis when the forward voltage is injected at different angles;

[0062] The initial angle judgment module is used to select the direction with the maximum absolute value of the d-axis current change slope as the real d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

[0063] See also Figure 2 Schematic diagram of an electronic device provided by an embodiment of the present invention. Figure 2 As shown, an embodiment of the present invention provides an electronic device, including a memory 1310, a processor 1320, and a computer program 1311 stored in the memory 1310 and executable on the processor 1320. When the processor 1320 executes the computer program 1311, the following steps are implemented: S1, designing a waveform voltage with an injection period of T, wherein the waveform period T includes four time periods, namely, T1-T2, T2-T3, T3-T4, and T4-T5;

[0064] S2, inject a forward voltage and a reverse voltage with a voltage amplitude of U2 in the two time periods T2-T3 and T3-T4, respectively, and inject a forward voltage and a reverse voltage with a voltage amplitude of U1 in the two time periods T1-T2 and T4-T5;

[0065] S3, selecting an injection angle interval to form an injection angle group, selecting different angle intervals within the injection angle group, and sequentially injecting waveform voltages according to the same voltage injection method as in step S2; collecting feedback currents of the d-axis when the forward voltage is injected at different angles;

[0066] S4, select the direction with the maximum absolute value of the d-axis current change slope as the true d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

[0067] See also Figure 3 Schematic diagram of an embodiment of a computer-readable storage medium provided by the present invention. Figure 3As shown, this embodiment provides a computer-readable storage medium 1400, on which a computer program 1411 is stored. When the computer program 1411 is executed by a processor, the following steps are implemented: S1, designing a waveform voltage with an injection period of T, wherein the waveform period T includes four time periods, namely, T1-T2, T2-T3, T3-T4, and T4-T5;

[0068] S2, inject a forward voltage and a reverse voltage with a voltage amplitude of U2 in the two time periods T2-T3 and T3-T4, respectively, and inject a forward voltage and a reverse voltage with a voltage amplitude of U1 in the two time periods T1-T2 and T4-T5;

[0069] S3, selecting an injection angle interval to form an injection angle group, selecting different angle intervals within the injection angle group, and sequentially injecting waveform voltages according to the same voltage injection method as in step S2; collecting feedback currents of the d-axis when the forward voltage is injected at different angles;

[0070] S4, select the direction with the maximum absolute value of the d-axis current change slope as the true d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

[0071] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0072] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0073] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for detecting the initial position of a rotor of a permanent magnet synchronous motor, characterized in that: The following steps are involved: S1, design a waveform voltage with an injection period of T, where the waveform period T includes four time periods: T1-T2, T2-T3, T3-T4 and T4-T5; S2, in the two time periods T2-T3 and T3-T4, respectively, inject a forward voltage and a reverse voltage with a voltage amplitude of U2, and in the two time periods T1-T2 and T4-T5, respectively, inject a forward voltage and a reverse voltage with a voltage amplitude of U1, U1 <U2; S3, selecting an injection angle interval to form an injection angle group, selecting different angle intervals within the injection angle group, and sequentially injecting waveform voltages according to the same voltage injection method as in step S2; collecting feedback currents of the d-axis when the forward voltage is injected at different angles; S4, select the direction with the maximum absolute value of the d-axis current change slope as the true d-axis direction, and then perform polarity judgment to obtain the initial angular position of the rotor.

2. The method for detecting the initial position of the rotor of a permanent magnet synchronous motor according to claim 1, characterized in that: The S2 also includes: in the time period 0-T1, the voltage amplitude Ud injected on the d-axis is equal to U2, and the q-axis injected voltage Uq is set to 0 to clear the excitation magnetic field.

3. The method for detecting the initial position of the rotor of a permanent magnet synchronous motor according to claim 1, characterized in that: The S2 specifically includes: determining the current sampling accuracy according to the product accuracy requirements, and determining the selection of the later injection voltage amplitude U2 according to the current sampling accuracy; The voltage setting standard of U2 is: When the voltage is injected, the motor disturbance is within the allowable range, and at the same time, the sampling current size is ensured not to trigger the motor's overcurrent protection. The d-axis current rise amplitude in each sampling cycle can be accurately collected by the sampling circuit.

4. The method for detecting the initial position of the rotor of a permanent magnet synchronous motor according to claim 3, characterized in that: The numerical value of U1 is one tenth of the numerical value of U2.

5. The method for detecting the initial position of the rotor of a permanent magnet synchronous motor according to claim 1, characterized in that: The S3 specifically includes: When collecting the feedback current of the d-axis, the current difference between two adjacent current sampling points is greater than the sampling accuracy.

6. The method for detecting the initial position of the rotor of a permanent magnet synchronous motor according to claim 1, characterized in that: The S4 specifically includes: S41, selecting the direction with the maximum absolute value of the slope of the d-axis current change as the reference direction for the next round of injection, and taking the angle interval of half of the corresponding injection angle interval A as the interval for the next round of injection, and then repeating step S3 to perform waveform voltage injection; S42, selecting the direction with the maximum absolute value of the d-axis current change slope in all waveform voltage injection groups as the true d-axis direction, and then performing polarity judgment to obtain the initial angular position of the rotor.

7. The method for detecting the initial position of the rotor of a permanent magnet synchronous motor according to claim 1, characterized in that: The S4 specifically includes: After obtaining the actual d-axis direction, the polarity is judged. If it is positive, it is used as the initial angular position of the rotor. If it is reverse, π needs to be added as the initial angular position of the rotor.

8. A permanent magnet synchronous motor rotor initial position detection system, characterized in that: The system is used to implement the method for detecting the initial position of the rotor of the permanent magnet synchronous motor according to any one of claims 1 to 7, comprising: The waveform voltage design module is used to design a waveform voltage with an injection period of T, where the waveform period T includes four time periods, namely, T1-T2, T2-T3, T3-T4 and T4-T5; In the two time periods T2-T3 and T3-T4, a forward voltage and a reverse voltage with a voltage amplitude of U2 are respectively injected, and in the two time periods T1-T2 and T4-T5, a forward voltage and a reverse voltage with a voltage amplitude of U1 are respectively injected; The waveform voltage injection module is used to select an injection angle interval to form an injection angle group, select different angle intervals within the injection angle group, and sequentially inject the waveform voltage according to the same voltage injection method in step S2; collect the feedback current of the d-axis when the forward voltage is injected at different angles; The initial angle judgment module is used to select the direction with the maximum absolute value of the d-axis current change slope as the real d-axis direction, and then perform polarity judgment to obtain the initial angle position of the rotor.

9. An electronic device, characterized in that: It comprises a memory and a processor, wherein the processor is used to implement the steps of the method for detecting the initial position of the rotor of a permanent magnet synchronous motor as described in any one of claims 1 to 7 when executing a computer management program stored in the memory.

10. A computer-readable storage medium, characterized in that: A computer management program is stored thereon, and when the computer management program is executed by the processor, the steps of the method for detecting the initial position of the rotor of the permanent magnet synchronous motor as described in any one of claims 1 to 7 are implemented.

Images