A method and device for testing flux linkage and inductance of a permanent magnet synchronous motor

Abstract

The present application discloses a method and device for testing the flux linkage and inductance of a permanent magnet synchronous motor, the method comprising: collecting the three-phase current information and rotor position information of the permanent magnet synchronous motor, and determining the d-q axis current of the permanent magnet synchronous motor based on the information. The current command input to the permanent magnet synchronous motor model is determined according to the pre-planned current operating point, and the d-q axis voltage for controlling the permanent magnet synchronous motor is obtained based on the difference between the current command and the d-q axis current. Afterwards, the inductance of the permanent magnet synchronous motor is tested to obtain the cross-incremental inductance and self-axis incremental inductance of the d-q axis, and the flux linkage equation is integrated according to the cross-incremental inductance and self-axis incremental inductance of the d-q axis and the defined flux linkage establishment path to obtain the d-q axis flux linkage under different currents. The method disclosed in the present application comprehensively considers the magnetic saturation of the core and the cross-coupling effect of the flux linkage, and improves the accuracy of measuring the flux linkage and inductance of the permanent magnet synchronous motor.

Description

Technical Field

[0001] The present application relates to the field of motor technology, and in particular to a method and device for testing the flux linkage and inductance of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors are widely used in the industrial field due to their advantages such as high efficiency, high power density and wide speed regulation range. In order to achieve high-performance control of permanent magnet synchronous motors, it is necessary to accurately obtain the flux and inductance parameters of permanent magnet synchronous motors. Flux and inductance parameters are key parameters of the mathematical model of permanent magnet synchronous motors, and their accuracy directly affects the performance of permanent magnet synchronous motor control.

[0003] In the prior art, the commonly used methods for obtaining flux linkage and inductance include finite element analysis, no-load test method, and flux linkage calculation method. However, these methods usually do not take into account the actual manufacturing errors and material performance deviations of permanent magnet synchronous motors, and the calculation results may differ from the actual performance. In addition, these methods do not take into account the magnetic saturation of the core and the cross-coupling effect of flux linkage, which makes it difficult to fully and accurately obtain the inductance and flux linkage characteristics of permanent magnet synchronous motors under actual operating conditions, thereby affecting the measurement accuracy. Summary of the invention

[0004] In order to address the deficiencies of the prior art, the purpose of the present application is to provide a method and device for testing the flux linkage and inductance of a permanent magnet synchronous motor, which can improve the accuracy of measuring the flux linkage and inductance of a permanent magnet synchronous motor.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] In the first aspect, the present application provides a method for testing the flux linkage and inductance of a permanent magnet synchronous motor, the method comprising: collecting the three-phase current and rotor position information of the permanent magnet synchronous motor, and determining the dq-axis current of the permanent magnet synchronous motor based on the three-phase current and rotor position information; determining the current command input to the permanent magnet synchronous motor model based on the pre-planned current operating point, and adjusting the current control loop where the permanent magnet synchronous motor is located based on the difference between the current command and the dq-axis current, so that the current control loop where the permanent magnet synchronous motor is located operates in a stable state to obtain the dq-axis voltage for controlling the permanent magnet synchronous motor; testing the inductance of the permanent magnet synchronous motor when the current control loop operates in a stable state, and performing the following means to obtain the cross-incremental inductance and self-axis incremental inductance of the dq axes: fixing the d-axis current and changing the q-axis current; and fixing the q-axis current and changing the d-axis current; integrating the flux linkage equation according to the cross-incremental inductance and self-axis incremental inductance of the dq axes and the defined flux linkage establishment path to obtain the dq-axis flux linkage under different currents.

[0007] Furthermore, when the current control loop operates in a stable state, the inductance of the permanent magnet synchronous motor is tested, including: selecting a number of first test points from a first range of d-axis currents, each first test point representing a different current; selecting a first test point to linearly change the q-axis current within a first set time interval to obtain the cross-incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis; or selecting a number of second test points from a second range of q-axis currents, each second test point representing a different current; selecting a second test point to linearly change the d-axis current within a second set time interval to obtain the self-axis incremental inductance of the d-axis and the cross-incremental inductance of the q-axis.

[0008] Furthermore, the first range is , select the first test point in the first range , where M is a positive integer, represents the maximum stator current of the permanent magnet synchronous motor, I d represents the d-axis current; and obtains a first functional formula characterizing the d-axis current, the first functional formula being:

[0009] ;

[0010] In the formula, Indicates the d-axis current of the xth first test point The corresponding first current instruction; the second range is , select the second test point in the second range , where N is a positive integer, I q represents the q-axis current; and obtains a second functional formula characterizing the q-axis current, the second functional formula being:

[0011] ;

[0012] In the formula, Indicates the q-axis current of the N+yth second test point The corresponding second current instruction.

[0013] Furthermore, when When fixed In the case of Linear change to , the q-axis current transformation is ; and / or, when When fixed In the case of Linear change to , the q-axis current transformation is ; According to the following relationship, calculate and The cross incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis are:

[0014] ;

[0015] ;

[0016] in, and are the d-axis voltage and q-axis voltage of the permanent magnet synchronous motor respectively; R is the stator resistance; and are d-axis current and q-axis current respectively; Cross incremental inductance of d-axis, It represents the incremental inductance of the q-axis.

[0017] Furthermore, when When fixed In the case of Linear change to , the d-axis current transformation is ; According to the following relationship, calculate The self-axis incremental inductance of the d-axis and the cross incremental inductance of the q-axis are:

[0018] ;

[0019] ;

[0020] in, represents the incremental inductance of the d-axis. Represents the cross incremental inductance of the q-axis.

[0021] Furthermore, when testing the permanent magnet synchronous motor, the permanent magnet synchronous motor meets the following restrictions:

[0022] ;

[0023] and, ;

[0024] For systems using space vector pulse width modulation, ,in V DC Indicates the DC bus voltage of the permanent magnet synchronous motor; is the maximum stator current of the permanent magnet synchronous motor.

[0025] Furthermore, when , When , the dq axis flux satisfies the following relationship:

[0026] ;

[0027] when , When , the dq axis flux satisfies the following relationship:

[0028] ;

[0029] in, , Represents different combination currents The dq axis flux under.

[0030] Furthermore, the permanent magnet synchronous motor model is specifically:

[0031] (1);

[0032] In the formula, and are the d-axis voltage and q-axis voltage of the permanent magnet synchronous motor respectively; R is the stator resistance; and are d-axis current and q-axis current respectively; and are the self-axis incremental inductances of the d-axis and q-axis respectively; and are the cross incremental inductances of the d-axis and q-axis respectively.

[0033] Furthermore, the nonlinear mathematical model of the permanent magnet synchronous motor in the synchronous rotating dq coordinate system is determined, and the nonlinear mathematical model satisfies the following relationship:

[0034] (2);

[0035] In the formula, represents the angular velocity of the permanent magnet synchronous motor, represents the d-axis magnetic flux, represents the q-axis flux; in the synchronous rotating dq coordinate system, when the d-axis of the permanent magnet synchronous motor is aligned with the flux of the permanent magnet, the d-axis flux and the q-axis flux can be expressed as:

[0036] (3);

[0037] In the formula, It means that the d-axis flux is a function of the d-axis current, It means that the q-axis flux is a function of the q-axis current, is the magnetic flux generated by the permanent magnet; the d-axis magnetic flux and the q-axis magnetic flux are derived respectively, and combined with the chain rule, the following relationship is obtained:

[0038] (4);

[0039] Substitute formula (4) into formula (2) to obtain the permanent magnet synchronous motor model.

[0040] In the second aspect, the present application provides a test device for the magnetic flux and inductance of a permanent magnet synchronous motor, including: a sampling unit, the sampling unit is connected to the input end of a permanent magnet synchronous motor, and samples the three-phase current flowing through the permanent magnet synchronous motor, and the sampling unit is also used to sample the position information of the rotor of the permanent magnet synchronous motor; a calculation unit, the calculation unit is used to perform the following steps: receiving the three-phase current, and determining the dq-axis current of the permanent magnet synchronous motor according to the three-phase current; determining the current command input to the permanent magnet synchronous motor model according to a pre-planned current operating point, and adjusting the current control loop where the permanent magnet synchronous motor is located based on the difference between the current command and the dq-axis current, so that the current control loop where the permanent magnet synchronous motor is located operates in a stable state to obtain control of the permanent magnet synchronous motor. The invention discloses a method for obtaining a dq axis voltage of a permanent magnet synchronous motor; generating a space vector pulse width modulation signal according to the dq axis voltage of the permanent magnet synchronous motor; and an inverter unit, which is used to output a three-phase AC voltage according to the space vector pulse width modulation signal to drive the permanent magnet synchronous motor to operate according to a current instruction; wherein, when the current control loop operates in a stable state, the calculation unit tests the inductance of the permanent magnet synchronous motor and performs the following means to obtain the cross-incremental inductance and self-axis incremental inductance of the dq axes: fixing the d axis current and changing the q axis current; and fixing the q axis current and changing the d axis current; integrating the magnetic flux equation according to the cross-incremental inductance and self-axis incremental inductance of the dq axes and the defined magnetic flux establishment path to obtain the dq axis magnetic flux under different currents.

[0041] Compared with the prior art, the magnetic synchronous motor flux and inductance test method proposed in the present application collects the three-phase current and rotor position information of the permanent magnet synchronous motor, and determines the dq axis current of the permanent magnet synchronous motor according to the three-phase current and rotor position information. After that, the current command input to the permanent magnet synchronous motor model is determined according to the pre-planned current operating point, and the current control loop where the permanent magnet synchronous motor is located is adjusted based on the difference between the current command and the dq axis current, so that the current control loop where the permanent magnet synchronous motor is located works in a stable state to obtain the dq axis voltage of the permanent magnet synchronous motor. When the current control loop works in a stable state, the inductance of the permanent magnet synchronous motor is tested to obtain the cross-incremental inductance and self-axis incremental inductance of the dq axis. Finally, the flux equation is integrated according to the cross-incremental inductance and self-axis incremental inductance of the dq axis, and the defined flux establishment path to obtain the dq axis flux under different currents. The method proposed in the present application comprehensively considers the core magnetic saturation and flux cross-coupling effects, and improves the accuracy of the flux and inductance measurement of the permanent magnet synchronous motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the structure of a device for testing the flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application;

[0043] Figure 2 A flowchart schematic diagram of a method for testing flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application;

[0044] Figure 3 A schematic diagram of a flow chart of another method for testing flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application;

[0045] Figure 4 A schematic diagram of the principle of a method for testing the flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application;

[0046] Figure 5 A schematic diagram of an application scenario of a method for testing the flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the specific implementation manner of the present application will be clearly and completely described below in conjunction with the drawings in the implementation manner of the present application.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the embodiments of the present application as detailed in the attached claims.

[0049] It should also be understood that the term “comprising” indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements and / or components.

[0050] A method and device for testing the flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application will be described in detail below in conjunction with the accompanying drawings.

[0051] Figure 1 is a structural schematic diagram of a permanent magnet synchronous motor flux and inductance testing device provided in an embodiment of the present application, such as Figure 1As shown, the device includes: a sampling unit 101, a calculation unit 102 and an inversion unit 103.

[0052] The sampling unit 101 is connected to the input end of a permanent magnet synchronous motor and samples the three-phase current flowing through the permanent magnet synchronous motor. The sampling unit is also used to sample the position information of the rotor of the permanent magnet synchronous motor. For example, the three-phase current can be collected by the current sampling unit, and the position information of the rotor can be collected by an encoder.

[0053] The computing unit 102 is used to perform the following steps:

[0054] The three-phase current flowing through the permanent magnet synchronous motor is received and sampled, and combined with the rotor position information provided by the motor encoder in the sampling unit, the current in the three-phase coordinate system is converted into the current component in the two-phase rotating coordinate system (dq coordinate system) through coordinate transformation, thereby determining the d-axis and q-axis currents of the permanent magnet synchronous motor.

[0055] The current command input to the permanent magnet synchronous motor model is determined according to the pre-planned current operating point, and the current control loop of the permanent magnet synchronous motor is adjusted based on the difference between the current command and the dq axis current, so that the current control loop of the permanent magnet synchronous motor operates in a stable state to obtain the dq axis voltage for controlling the permanent magnet synchronous motor.

[0056] A space vector pulse width modulation signal is generated according to the dq axis voltage of the permanent magnet synchronous motor.

[0057] The inverter unit 103 is used to output a three-phase AC voltage according to the space vector pulse width modulation signal to drive the permanent magnet synchronous motor to operate according to the current instruction.

[0058] When the current control loop operates in a stable state, the calculation unit 102 tests the inductance of the permanent magnet synchronous motor and performs the following means to obtain the cross incremental inductance and the self-axis incremental inductance of the dq axis:

[0059] The d-axis current is fixed and the q-axis current is varied;

[0060] and, fix the q-axis current and vary the d-axis current;

[0061] The flux equation is determined according to the cross incremental inductance and self-axis incremental inductance of the dq axis, and the flux equation is integrated according to the defined flux establishment path to obtain the dq axis flux under different currents.

[0062] It can be understood that the method for testing the flux linkage and inductance of a permanent magnet synchronous motor can be performed by the above-mentioned device for testing the flux linkage and inductance of a permanent magnet synchronous motor. Figure 1The structure of the test device for the flux linkage and inductance of the permanent magnet synchronous motor shown in the figure does not constitute a limitation on the test device for the flux linkage and inductance of the permanent magnet synchronous motor. The test device for the flux linkage and inductance of the permanent magnet synchronous motor may include a Figure 1 More or fewer components may be shown, or certain components may be combined, or the components may be arranged differently.

[0063] It should be noted that the executor of the permanent magnet synchronous motor flux and inductance testing method provided in the present application is a permanent magnet synchronous motor flux and inductance testing device, which may also be a chip or system on chip, without limitation.

[0064] The embodiments of the present application do not limit the application scenarios of the device. The business scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. It is known to those skilled in the art that with the evolution of technology and the emergence of new business scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0065] Figure 2 is a flow chart of a method for testing flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application, such as Figure 2 As shown, the high dynamic response current control method of the permanent magnet synchronous motor includes steps S201 to S204:

[0066] Step S201: collect the three-phase current and rotor position information of the permanent magnet synchronous motor, and determine the dq axis current of the permanent magnet synchronous motor according to the three-phase current and the rotor position information.

[0067] As an implementation method, when the permanent magnet synchronous motor is stopped, the sampling unit 101 collects the three-phase current (i a ,i b ,i c ) and rotor position information, and sends it to the calculation unit 102. Accordingly, the calculation unit 102 receives the three-phase current and rotor position information of the permanent magnet synchronous motor, and transforms the three-phase current of the permanent magnet synchronous motor from three phases to two phases, that is, converts the three-phase current into a DC current component I in the rotating coordinate system d and I q , so as to project the current onto the reference coordinate system that rotates synchronously with the permanent magnet synchronous motor rotor and obtain the dq axis current of the permanent magnet synchronous motor.

[0068] Step S202, determine the current command input to the permanent magnet synchronous motor model according to the pre-planned current operating point, and adjust the current control loop of the permanent magnet synchronous motor based on the difference between the current command and the dq axis current, so that the current control loop of the permanent magnet synchronous motor operates in a stable state to obtain the dq axis voltage for controlling the permanent magnet synchronous motor.

[0069] Among them, the calculation unit 102 pre-stores multiple current operating points (current instructions), and the current instructions input into the permanent magnet synchronous motor model are used to compare with the dq axis current, and the voltage adjustment amount of the permanent magnet synchronous motor is calculated according to the difference obtained by the comparison to adjust the current control loop where the permanent magnet synchronous motor is located.

[0070] The permanent magnet synchronous motor model is used to describe the relationship between parameters such as permanent magnet synchronous motor flux, inductance, voltage and current. The permanent magnet synchronous motor model is specifically expressed as follows (1):

[0071] (1);

[0072] In formula (1), and are the d-axis voltage and q-axis voltage of the permanent magnet synchronous motor respectively; R is the stator resistance; and are d-axis current and q-axis current respectively; and are the self-axis incremental inductances of the d-axis and q-axis respectively; and are the cross incremental inductances of the d-axis and q-axis respectively.

[0073] As an implementation method, the calculation unit 102 first establishes a nonlinear mathematical model of the permanent magnet synchronous motor in a synchronous rotating dq coordinate system, and the nonlinear mathematical model satisfies the following relationship (2):

[0074] (2);

[0075] In formula (2), represents the angular velocity of the permanent magnet synchronous motor, represents the d-axis magnetic flux, represents the q-axis magnetic flux.

[0076] Further, in the synchronous rotating dq coordinate system, when the d-axis of the permanent magnet synchronous motor is aligned with the flux of the permanent magnet, the calculation unit 102 expresses the d-axis flux and the q-axis flux as formula (3):

[0077] (3);

[0078] In the formula, It means that the d-axis flux is a function of the d-axis current, It means that the q-axis flux is a function of the q-axis current, is the flux linkage generated by the permanent magnet.

[0079] Furthermore, the calculation unit 102 respectively derives the d-axis flux and the q-axis flux, and combines the chain rule to obtain the following relationship:

[0080] (4)

[0081] Finally, the calculation unit 102 substitutes formula (4) into formula (2) to obtain a nonlinear model for flux linkage test, which satisfies the following relationship (5):

[0082] (5)

[0083] in, , They are the self-axis incremental inductance of the d-axis and q-axis respectively, reflecting the magnetic saturation characteristics. , They are the cross incremental inductances of the d-axis and q-axis, respectively, reflecting the cross coupling characteristics between the d and q axes.

[0084] Furthermore, the calculation unit 102 compares the pre-stored multiple current instructions with the received dq axis current, and selects a current instruction (i ) that matches the received dq axis current from the multiple current instructions. * d 、i * q ), in order to determine the current command input to the permanent magnet synchronous motor model. The calculation unit 102 performs PI operation (adjusting proportional gain and integral gain) based on the current command and the dq axis current to optimize the response of the current control loop and calculate the voltage adjustment amount to be applied to the permanent magnet synchronous motor to obtain the dq axis voltage (u * d 、u * q ), and adjust the dq axis current so that the current control loop where the permanent magnet synchronous motor is located works in a stable state.

[0085] Step S203: When the current control loop operates in a stable state, the inductance of the permanent magnet synchronous motor is tested to obtain the cross incremental inductance and the self-axis incremental inductance of the dq axis.

[0086] Among them, the cross incremental inductance represents the inductance generated by the mutual influence between the d-axis and q-axis of the permanent magnet synchronous motor, and reflects the cross-coupling characteristics between the d-axis and the q-axis.

[0087] The self-axis incremental inductance represents the inductance on the d-axis or q-axis of the permanent magnet synchronous motor. When the stator current is large, the permanent magnet synchronous motor will enter the magnetic saturation state. As the current changes, the inductance on the d-axis or q-axis also changes. The self-axis incremental inductance reflects the magnetic saturation characteristics of the permanent magnet synchronous motor.

[0088] As an implementation manner, when the calculation unit 102 tests the inductance of the permanent magnet synchronous motor, the permanent magnet synchronous motor needs to meet the following restriction conditions: and .

[0089] U max Indicates the maximum voltage limit during the test. I max Indicates the maximum stator current of the permanent magnet synchronous motor, that is, the maximum current limit during the test of the permanent magnet synchronous motor. v d (t) represents the d-axis voltage, v q (t) represents the q-axis voltage, i d (t) Indicates the d-axis current ，i q (t) represents the q-axis current.

[0090] When performing space vector pulse width modulation, the voltage of the permanent magnet synchronous motor meets ,in V DC Indicates the DC bus voltage of the permanent magnet synchronous motor.

[0091] Specifically, Figure 3 As shown, testing the inductance of the permanent magnet synchronous motor includes steps S2031 to S2033:

[0092] Step S2031 : Select a number of first test points from the d-axis current in the first range, or select a number of second test points from the q-axis current in the second range.

[0093] The current represented by each first test point is different, and the current represented by each second test point is different.

[0094] It should be noted that when the d-axis current is less than zero, the magnetic field generated by part of the permanent magnet can be offset and weak magnetic control can be achieved. Therefore, the calculation unit 102 selects a number of first test points when the d-axis current is less than or equal to zero, but the present application does not limit the test points where the d-axis current is greater than zero.

[0095] As an implementation method, in the first range The calculation unit 102 selects a number of first test points , M is a positive integer. Then, the calculation unit 102 establishes a first functional formula to characterize the d-axis current, and the first functional formula is:

[0096] (6),

[0097] In the formula, Indicates the first current instruction of the xth first test point, Indicates the d-axis current corresponding to the first current command.

[0098] Similarly, in the second range The calculation unit 102 selects a number of second test points , N is a positive integer. Then, the calculation unit 102 establishes a second functional formula to characterize the q-axis current, and the second functional formula is:

[0099] (7);

[0100] In the formula, represents the second current instruction of the N+yth second test point, Indicates the q-axis current corresponding to the second current command.

[0101] Step S2032: select a first test point, and make the q-axis current change linearly within a first set time interval to obtain the cross-axis incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis.

[0102] As a way to achieve this, When fixed In the case of Linear change to , the q-axis current transformation is .

[0103] and / or when When fixed In the case of Linear change to , the q-axis current transformation is ;

[0104] The calculation unit 102 maintains The following relationship is obtained:

[0105] (8);

[0106] (9).

[0107] The calculation unit 102 calculates according to the above equations (8) and (9) and The cross incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis.

[0108] It should be noted that when When , the cross incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis satisfy the following expressions:

[0109] (10);

[0110] Step S2033: select a second test point, and make the d-axis current change linearly within a second set time interval to obtain the self-axis incremental inductance of the d-axis and the cross-incremental inductance of the q-axis.

[0111] As a way to achieve this, in a fixed In the case of Linear change to , the d-axis current transformation is .

[0112] The calculation unit 102 maintains The following relationship is obtained:

[0113] (11),

[0114] (12);

[0115] The calculation unit 102 calculates according to the above relationship (11) and (12): The d-axis incremental inductance and the q-axis incremental inductance are shown in Figure 2.

[0116] S204, determining a flux equation according to the cross incremental inductance and the self-axis incremental inductance of the dq axis, and integrating the flux equation according to the defined flux establishment path to obtain the dq axis flux under different currents.

[0117] As an implementation method, the calculation unit 102 integrates the above formula 4 to obtain the following expression:

[0118] (13),

[0119] Further, the calculation unit 102 substitutes the cross incremental inductance and self-axis incremental inductance of the dq axis calculated in the above step S203 into the above expression to calculate the dq axis flux linkage under different currents.

[0120] Specifically, when , When , the dq-axis flux linkage under different currents calculated by the calculation unit 102 is 0.

[0121] when , When the calculation unit 102 defines the magnetic link establishment path (0,0)~(0,i qy )~(i qx ,i qy ), then the dq axis flux under different currents satisfies the following expression:

[0122] (14),

[0123] The calculation unit 102 calculates the dq-axis flux linkage according to the above expression (14).

[0124] when , When the calculation unit 102 defines the magnetic link establishment path (0,0)~(0,i qy )~(i qx ,i qy ), then the dq axis flux under different currents satisfies the following expression:

[0125] (15),

[0126] The calculation unit 102 calculates the dq-axis flux linkage according to the above expression (15).

[0127] It should be noted that the dq-axis flux calculated in this application only represents the change in d-axis flux caused by current, and does not include the flux generated by permanent magnets. According to the definition of formula 3, the complete d-axis flux should be , The value of can be obtained by individual experiments or analytical methods, such as open circuit back EMF testing or finite element analysis.

[0128] Based on the above scheme, the test method of the flux linkage and inductance of the permanent magnet synchronous motor provided by the present application collects the three-phase current and rotor position information of the permanent magnet synchronous motor, and determines the dq axis current of the permanent magnet synchronous motor according to the three-phase current and rotor position information, determines the current command input to the permanent magnet synchronous motor model according to the pre-planned current working point, and obtains the dq axis voltage for controlling the permanent magnet synchronous motor based on the difference between the current command and the dq axis current. When the current control loop is working in a stable state, the inductance of the permanent magnet synchronous motor is tested to obtain the cross-incremental inductance and self-axis incremental inductance of the dq axis, and the cross-incremental inductance and self-axis incremental inductance of the dq axis, and the defined flux linkage establishment path, the flux linkage equation is integrated to obtain the dq axis flux linkage under different currents. The method proposed in the present application comprehensively considers the cross-coupling effect of the magnetic saturation flux linkage of the core, and calculates the cross-incremental inductance and self-axis incremental inductance by setting a high-density test point, so as to obtain a comprehensive and accurate permanent magnet synchronous motor inductance, and effectively ignores the influence of the stator resistance error.

[0129] At the same time, the present application uses the measured high-precision cross incremental inductance and self-axis incremental inductance to integrate according to the set integration path to calculate the magnetic flux characteristics of the motor. Unlike the traditional direct integration method, the initial value of the magnetic flux integral in the present application is zero, and the integration process is completely independent of the motor parameters. This integration method effectively overcomes the error accumulation and amplification problems caused by the uncertainty of stator resistance and the nonlinearity of the inverter in the traditional method, and greatly improves the accuracy and reliability of the magnetic flux calculation. In addition, the integration process is decoupled from the motor parameters, making the calculation results more accurate.

[0130] In summary, the solution provided in this application effectively improves the accuracy of flux linkage and inductance measurement of permanent magnet synchronous motors.

[0131] Figure 4 Schematic diagram of the principle of a permanent magnet synchronous motor flux and inductance test method provided in the embodiment of the present application. The permanent magnet synchronous motor flux and inductance test method adopts the principle of FOC current loop control method, such as Figure 4 As shown, the current loop control method of FOC includes: current sampling, rotor position sampling, transformation of 3-phase current to 2-phase current, PI operation and space vector pulse width modulation.

[0132] Current sampling: Current sampling is achieved by collecting the three-phase current of the permanent magnet synchronous motor, usually using a current sensor or sampling resistor.

[0133] Rotor position sampling: Rotor position sampling obtains the rotor position information of the permanent magnet synchronous motor through the encoder.

[0134] Transformation of 3-phase current to 2-phase current: The current in the three-phase coordinate system is transformed into the current component in the two-phase rotating coordinate system (dq coordinate system) through coordinate transformation, so as to determine the d-axis and q-axis currents of the permanent magnet synchronous motor. For example, the transformation of 3-phase current to 2-phase current can be Clark transformation and Park transformation. Clark transformation converts the sampled three-phase currents Ia, Ib and Ic of the permanent magnet synchronous motor into two-phase currents Iα and Iβ, and Clark transformation converts the current from the stationary three-phase coordinate system to the two-phase vertical coordinate system. Park transformation further converts Iα and Iβ to the rotating direct axis (d-axis) and quadrature axis (q-axis) coordinate systems, and the dq-axis current represents the current components in the direct axis and quadrature axis directions of the permanent magnet synchronous motor rotor. For another example, the transformation of 3-phase current to 2-phase current can also be directly transformed using a preset formula.

[0135] PI operation: By comparing the current reference value (i * d and i * q ) and the actual current feedback value (current sampling from the permanent magnet synchronous motor), the voltage vector output by the inverter is adjusted using a PI controller to generate the desired voltage signal to drive the permanent magnet synchronous motor to achieve the required current and torque.

[0136] Space vector pulse width modulation: According to the voltage command calculated by the PI controller, space vector pulse width modulation (SVPWM) technology is used to generate a three-phase PWM signal to control the switching states of the inverter to drive the permanent magnet synchronous motor.

[0137] The FOC current loop control method principle adopted in this application improves the accuracy of the test compared with the traditional open-loop test method. The FOC current loop control method can monitor and adjust the current in real time, so that it can accurately track the preset current instruction, ensuring the accuracy of current measurement. Through closed-loop control, the test scheme of this application can effectively suppress the test errors caused by various interference factors, thereby significantly improving the reliability and accuracy of the test results.

[0138] Figure 5 is a schematic diagram of an application scenario of a method for testing flux linkage and inductance of a permanent magnet synchronous motor provided in an embodiment of the present application, such as Figure 5 As shown, the structure of the application scenario includes: a test device for the magnetic flux and inductance of a permanent magnet synchronous motor, a permanent magnet synchronous motor, a coupling, a load stalling platform and a terminal.

[0139] Among them, the permanent magnet synchronous motor is connected to the test device of the permanent magnet synchronous motor flux and inductance and the coupling, the permanent magnet synchronous motor is connected to the load stalling platform through the coupling, and the terminal is connected to the test device of the permanent magnet synchronous motor flux and inductance.

[0140] The permanent magnet synchronous motor is used to send three-phase current to a test device for the flux linkage and inductance of the permanent magnet synchronous motor, and is also used to receive current fed back by the test device for the flux linkage and inductance of the permanent magnet synchronous motor, so that the permanent magnet synchronous motor reaches a stable state.

[0141] The testing device for the flux linkage and inductance of a permanent magnet synchronous motor is used to receive a three-phase current and execute the above-mentioned testing method for the flux linkage and inductance of a permanent magnet synchronous motor according to the three-phase current.

[0142] The coupling is used to connect the permanent magnet synchronous motor and the load stalling platform.

[0143] The load stalling platform is used to fix the permanent magnet synchronous motor.

[0144] The terminal is used to configure the set current and display the flux linkage and inductance of the permanent magnet synchronous motor under different current tests.

[0145] The application scenario of the method for testing the flux linkage and inductance of a permanent magnet synchronous motor provided in the present application can realize full automation of the test process, including automatic calculation of incremental inductance and automatic calculation of flux linkage. This automated structure not only greatly improves the test efficiency and reduces the error rate of manual operation, but also enables the present invention to quickly, accurately and stably obtain the flux linkage and inductance characteristics of the permanent magnet synchronous motor, and has strong practicality.

[0146] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A method for testing the flux linkage and inductance of a permanent magnet synchronous motor, characterized in that: include: Collecting three-phase current and rotor position information of the permanent magnet synchronous motor, and determining the dq axis current of the permanent magnet synchronous motor according to the three-phase current and rotor position information; Determine a current command input to a permanent magnet synchronous motor model according to a pre-planned current operating point, and adjust a current control loop of the permanent magnet synchronous motor based on a difference between the current command and the dq axis current, so that the current control loop of the permanent magnet synchronous motor operates in a stable state, so as to obtain a dq axis voltage for controlling the permanent magnet synchronous motor; When the current control loop operates in a stable state, the inductance of the permanent magnet synchronous motor is tested, and the following means are performed to obtain the cross incremental inductance and self-axis incremental inductance of the dq axis: The d-axis current is fixed, and the q-axis current is changed, and a plurality of first test points are selected from the d-axis current in a first range, each of the first test points representing a different current; Selecting the first test point, within a first set time interval, so that the q-axis current changes linearly to obtain the cross-incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis; The q-axis current is fixed, and the d-axis current is changed, and a plurality of second test points are selected from the q-axis current in a second range, each of the second test points representing a different current; Selecting a second test point, within a second set time interval, so that the d-axis current changes linearly to obtain the self-axis incremental inductance of the d-axis and the cross-incremental inductance of the q-axis; The flux equation is integrated according to the cross incremental inductance and self-axis incremental inductance of the dq axis and the defined flux establishment path to obtain the dq axis flux under different currents.

2. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 1, characterized in that: The first range is , select the first test point within the first range , where M is a positive integer, represents the maximum stator current of the permanent magnet synchronous motor, I d represents the d-axis current; A first functional formula characterizing the d-axis current is obtained, wherein the first functional formula is: ； In the formula, represents the d-axis current of the xth test point a corresponding first current instruction; The second range is , select the second test point within the second range , where N is a positive integer, I q represents the q-axis current; A second functional formula characterizing the q-axis current is obtained, wherein the second functional formula is: ； In the formula, Indicates the q-axis current of the second test point N+y The corresponding second current instruction.

3. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 2, characterized in that: when When fixed In the case of Linear change to , the q-axis current transformation is ; when When fixed In the case of Linear change to , the q-axis current transformation amount is ; According to the following relationship, we can calculate and The cross incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis are: ； ； in, and are the d-axis voltage and q-axis voltage of the permanent magnet synchronous motor respectively, R is the stator resistance, and are the d-axis current and the q-axis current respectively, represents the cross incremental inductance of the d-axis, It represents the incremental inductance of the q-axis.

4. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 3, characterized in that: when When fixed In the case of Linear change to , the d-axis current transformation is ; According to the following relationship, we can calculate The self-axis incremental inductance of the d-axis and the cross incremental inductance of the q-axis are: ； ； in, represents the self-axis incremental inductance of the d-axis, represents the cross incremental inductance of the q-axis.

5. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 4, characterized in that: When testing the permanent magnet synchronous motor, the permanent magnet synchronous motor meets the following restrictions: ； and, ; For systems using space vector pulse width modulation, ,in V DC Represents the DC bus voltage of the permanent magnet synchronous motor; is the maximum stator current of the permanent magnet synchronous motor.

6. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 4, characterized in that: when , When , the dq axis flux satisfies the following relationship: ； when , When , the dq axis flux satisfies the following relationship: ； in, , Represents different combination currents The dq axis flux linkage below.

7. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 1, characterized in that: The permanent magnet synchronous motor model is specifically: （1）； In the formula, and are the d-axis voltage and q-axis voltage of the permanent magnet synchronous motor respectively; R is the stator resistance; and are the d-axis current and the q-axis current respectively; and are the self-axis incremental inductances of the d-axis and q-axis respectively; and are the cross incremental inductances of the d-axis and q-axis respectively.

8. The method for testing the flux linkage and inductance of a permanent magnet synchronous motor according to claim 7, characterized in that: The method comprises: Determine a nonlinear mathematical model of the permanent magnet synchronous motor in a synchronous rotating dq coordinate system, wherein the nonlinear mathematical model satisfies the following relationship: （2）； In the formula, represents the angular velocity of the permanent magnet synchronous motor, represents the d-axis magnetic flux, represents the q-axis magnetic flux; In the synchronous rotating dq coordinate system, when the d-axis of the permanent magnet synchronous motor is aligned with the flux of the permanent magnet, the d-axis flux and the q-axis flux can be expressed as: （3）； In the formula, represents the d-axis flux linkage as a function of the d-axis current, represents that the q-axis flux is a function of the q-axis current, The magnetic flux generated by the permanent magnet; The d-axis magnetic flux and the q-axis magnetic flux are derived respectively, and combined with the chain rule, the following relationship is obtained: （4）； Substitute formula (4) into formula (2) to obtain the permanent magnet synchronous motor model.

9. A test device for flux linkage and inductance of a permanent magnet synchronous motor, characterized in that: include: A sampling unit, the sampling unit is connected to an input end of a permanent magnet synchronous motor and samples a three-phase current flowing through the permanent magnet synchronous motor. The sampling unit is also used to sample position information of a rotor of the permanent magnet synchronous motor; A computing unit, the computing unit is used to perform the following steps: Receiving the three-phase current, and determining the dq axis current of the permanent magnet synchronous motor according to the three-phase current; Determine a current command input to the permanent magnet synchronous motor model according to a pre-planned current operating point, and adjust a current control loop of the permanent magnet synchronous motor based on a difference between the current command and the dq axis current, so that the current control loop of the permanent magnet synchronous motor operates in a stable state, so as to obtain a dq axis voltage for controlling the permanent magnet synchronous motor; Generate a space vector pulse width modulation signal according to the dq axis voltage of the permanent magnet synchronous motor; an inverter unit, configured to output a three-phase AC voltage according to the space vector pulse width modulation signal, so as to drive the permanent magnet synchronous motor to operate according to the current instruction; Wherein, when the current control loop operates in a stable state, the calculation unit tests the inductance of the permanent magnet synchronous motor and performs the following means to obtain the cross incremental inductance and self-axis incremental inductance of the dq axis: The d-axis current is fixed, and the q-axis current is changed, and a plurality of first test points are selected from the d-axis current in a first range, each of the first test points representing a different current; Selecting the first test point, within a first set time interval, so that the q-axis current changes linearly to obtain the cross-incremental inductance of the d-axis and the self-axis incremental inductance of the q-axis; The q-axis current is fixed, and the d-axis current is changed, and a plurality of second test points are selected from the q-axis current in a second range, each of the second test points representing a different current; Selecting a second test point, within a second set time interval, so that the d-axis current changes linearly to obtain the self-axis incremental inductance of the d-axis and the cross-incremental inductance of the q-axis; The flux equation is integrated according to the cross incremental inductance and self-axis incremental inductance of the dq axis and the defined flux establishment path to obtain the dq axis flux under different currents.

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