A method of verifying an initial position angle of a synchronous electric machine

Abstract

The application provides a method for verifying an initial position angle of a synchronous motor, which comprises the following steps: dragging the motor to a fixed rotating speed; giving the motor a first current, adjusting the angle change of a current control angle in a preset interval, measuring the torque of the motor, and obtaining a first curve according to the corresponding relationship between the current control angle and the torque, wherein the preset interval comprises the value of the current control angle corresponding to the condition that the current is completely loaded on the d-axis; giving the motor a second current, adjusting the angle change of the current control angle in the preset interval, measuring the torque of the motor, and obtaining a second curve according to the corresponding relationship between the current control angle and the torque, wherein the second current is different from the first current; and judging whether the initial position angle of the motor has a deviation according to the intersection position of the first curve and the second curve. The application solves the problems that the operation steps of the existing method for measuring the initial position angle of the synchronous motor are complicated and the efficiency is low, and achieves the effects of simplifying the operation and improving the efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor control, and in particular to a method for verifying an initial position angle of a synchronous motor. BACKGROUND

[0002] The synchronous motor is widely used in high-speed driving systems such as electric vehicles due to its high power density, high reliability and high efficiency. It is of great significance to control the torque of the synchronous motor and improve the peak performance at high speed. Therefore, the calibration of the initial position angle of the synchronous motor is very important for torque control.

[0003] The initial position angle of the motor rotor (hereinafter referred to as the initial position angle) is an important parameter in motor control, and its accuracy has an important influence on fully exerting the performance of the motor. Many practical problems encountered in the field, such as overcurrent failure, poor torque accuracy, and motor rotation in the opposite direction, are related to the error of the initial position angle of the motor rotor. Therefore, the measurement of the initial position angle of the motor rotor and the accuracy of the measurement are very important.

[0004] In the prior art, the method for measuring the initial position angle of the motor rotor includes using a rotor position sensor, obtaining the corresponding relationship between the motor back electromotive force zero-crossing point and the rotor position sensor angle, or obtaining a plurality of methods such as high-frequency signal coupling injection. In the process of implementing the present application, the inventors found that the existing measurement methods all have errors, and the d-axis or q-axis current is used as the judgment result, which requires separate observation of multiple variables, and the operation steps are complicated and difficult for field operators to master. SUMMARY

[0005] The present application aims to at least partially solve one of the problems in the related art.

[0006] To this end, the purpose of the present application is to provide a method for verifying the initial position angle of the motor rotor, which can effectively judge the error of the initial position angle of the motor rotor, verify the precision of the initial position angle and is simple to operate.

[0007] To achieve the above purpose, the present application provides a method for verifying the initial position angle of a synchronous motor, comprising:

[0008] dragging the motor to a fixed speed;

[0009] applying a first current to the motor, adjusting the angle change of the current control angle in a preset interval, measuring the torque of the motor, and obtaining a first curve according to the corresponding relationship between the current control angle and the torque, wherein the preset interval includes the value of the current control angle corresponding to the loading of the current to the d-axis;

[0010] a second current is given to the motor, an angle change of a current control angle in the preset interval is adjusted, a torque of the motor is measured, a second curve is obtained according to a corresponding relationship between the current control angle and the torque, wherein the second current is not equal to the first current;

[0011] whether the initial position angle of the motor exists deviation is judged according to a position of an intersection of the first curve and the second curve.

[0012] The method for verifying the initial position angle of the synchronous motor according to the present application obtains the first curve and the second curve, judges whether the initial position angle of the motor exists deviation according to the position of the intersection of the first curve and the second curve, verifies the accuracy of the initial position angle, the steps are simple, the problem of complicated operation steps in the prior art is solved, the operation personnel are easy to master, the engineering site is easy to implement, and thus the reliability and the usability of the motor product are improved.

[0013] According to an embodiment of the present application, the dragging of the motor to a fixed rotating speed comprises:

[0014] The motor is dragged to a fixed rotating speed by using a motor test bench device.

[0015] According to an embodiment of the present application, the angle of the preset interval is -85° to -95°, and the current control angle corresponding to the condition that the current is all loaded to the d-axis is -90°.

[0016] According to an embodiment of the present application, the measurement of the torque of the motor comprises:

[0017] The torque of the motor is measured by using a torque sensor, wherein the torque sensor is installed on an output shaft of the motor test bench.

[0018] According to an embodiment of the present application, the first current is less than the second current, and the second current is 2 times of the first current.

[0019] According to an embodiment of the present application, the measurement of the torque of the motor comprises:

[0020] The torque of the motor is measured every 0.5° interval in the preset interval.

[0021] According to an embodiment of the present application, whether the initial position angle of the motor exists deviation is judged according to the position of the intersection of the first curve and the second curve, comprising:

[0022] the current control angle corresponding to the condition that the current is all loaded to the d-axis is an error-free angle;

[0023] if the current control angle corresponding to the intersection position of the first curve and the second curve is equal to the error-free angle, it is determined that the initial position angle has no error;

[0024] if the current control angle corresponding to the intersection position of the first curve and the second curve is not equal to the error-free angle, it is determined that the initial position angle has error.

[0025] According to one embodiment of the present application, the if the current control angle corresponding to the intersection position of the first curve and the second curve is not equal to the error-free angle, it is determined that the initial position angle has error includes:

[0026] if the current control angle corresponding to the intersection position of the first curve and the second curve is greater than the error-free angle, it is determined that the deviation of the initial position angle is positive;

[0027] if the current control angle corresponding to the intersection position of the first curve and the second curve is less than the error-free angle, it is determined that the deviation of the initial position angle is negative.

[0028] According to one embodiment of the present application, the given of the first current and the second current, the adjustment of the current control angle, and the modification of the initial position angle are all realized through the control of the host computer on the motor controller, the motor controller is connected with the motor, and the host computer is communicatively coupled with the motor controller.

[0029] According to one embodiment of the present application, the motor is a permanent magnet synchronous motor or an electrically excited synchronous motor.

[0030] Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0031] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the application. Moreover, the same reference numerals are used throughout the same figures. Among them:

[0032] Figure 1 is a schematic diagram of the trigonometric function relationship between the electronic stator d-axis and q-axis voltages.

[0033] Figure 2 is a flowchart of the method for verifying the initial position angle of the synchronous motor according to one embodiment of the present application.

[0034] Figure 3 is a relationship diagram of the current control angle and the torque when the initial position angle is correct.

[0035] Figure 4 is a graph of the relationship between the current control angle and the torque when the initial position angle deviation is large.

[0036] Figure 5 is a graph of the relationship between the current control angle and the torque when the initial position angle deviation is small. DETAILED DESCRIPTION

[0037] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein the same or like component have the same or similar designations. The embodiments described below are presented by way of example only and are not intended to limit the present application. Rather, the present application encompasses all modifications, equivalents and alternatives falling within the spirit and scope of the appended claims.

[0038] Referring to Figure 1 , when defining the rotor synchronous coordinate system in the synchronous motor, the d-axis is defined at the rotor N-pole, the q-axis is orthogonal to the d-axis and leads the d-axis by 90 degrees. The physical quantities of the stator and the rotor of the synchronous motor can be converted to be expressed in this coordinate system. This coordinate axis rotates with the rotor on the rotor.

[0039] The initial position angle is the mechanical angle of rotation for aligning the d-axis of the rotor with the A-phase axis of the stator winding. When there is an initial position angle deviation θerr, the d-axis and the q-axis of the stator relative to the rotor magnetic pole position in the rotor synchronous coordinate system will have an angle deviation θerr, which results in that the physical quantities converted to the rotor synchronous coordinate system for calculation are not accurate.

[0040] A method for verifying the initial position angle of a synchronous motor according to an embodiment of the present application is described below with reference to the accompanying drawings. Figure 2 is a flowchart of the method for verifying the initial position angle of a synchronous motor according to an embodiment of the present application. In Figure 2 , the execution subject of the flow is the method for verifying the initial position angle of a synchronous motor in Figure 2 . In combination with Figures 2-5 , the implementation flow of the method is described in detail as follows:

[0041] Step S102, drag the motor to a fixed speed.

[0042] In this embodiment, the fixed speed can be set according to actual requirements. The fixed speed is determined by the highest speed of the motor and the field weakening speed. The motor tested is a synchronous motor, which can be a permanent magnet synchronous motor or an electrically excited synchronous motor.

[0043] Step S104, a first current is given to the motor, an angle change of the current control angle in a preset interval is adjusted, a torque of the motor is measured, a first curve is obtained according to a corresponding relationship between the current control angle and the torque, and the preset interval includes a value of the current control angle corresponding to the current being loaded to the d-axis entirely.

[0044] In the embodiment, the given value of the first current can be directly written into the motor controller by a digital quantity. In an implementation, the range of the rotor position angle is 0-360 degrees, and after digitization, the corresponding digital value ranges from 0 to 4095, that is, the digital value 0 corresponds to the angle 0°, and the digital value 4095 corresponds to the angle 360°. The current control angle is the included angle between the three-phase resultant current is and the q-axis. It can be seen that the value of the current control angle corresponding to the current being loaded to the d-axis entirely is -90°. The current control angle and the initial position angle can also be written into the motor controller by a digital quantity to achieve adjustment. In an implementation, the first curve can be displayed on a display, the display is connected to an upper computer, the upper computer is communicatively coupled to the motor controller, and the motor controller is connected to the motor. The upper computer can realize adjustment of the current amplitude, adjustment of the current control angle, and modification of the initial position angle by controlling the motor controller. In an implementation, the maximum current output by the motor controller is 600 A, and the first current can be selected as 100 A. The upper computer and the motor controller realize communication through CAN.

[0045] Step S106, a second current is given to the motor, an angle change of the current control angle in a preset interval is adjusted, a torque of the motor is measured, a second curve is obtained according to a corresponding relationship between the current control angle and the torque, and the second current is not equal to the first current.

[0046] In the embodiment, the given value of the second current can be directly written into the motor controller by a digital quantity. In an implementation, the second current can be selected as 200 A. The principle of selecting the second current is to make the second curve have a larger included angle with the first curve. The larger the included angle, the easier it is to observe the intersection position, and the error is also reduced. In addition, the second current also cannot exceed the maximum current output by the motor controller. In an implementation, the second current is twice the first current. The inventors find that under this relationship, the first curve and the second curve have a larger included angle, and it is easy to observe the intersection position.

[0047] Step S108, whether the initial position angle of the motor has a deviation is judged according to the intersection position of the first curve and the second curve.

[0048] In the embodiment, by comparing the current control angle corresponding to the intersection position of the first curve and the second curve with the current control angle corresponding to the current being loaded to the d-axis entirely, whether the initial position angle of the motor has a deviation can be judged.

[0049] The method for verifying the initial position angle of the synchronous motor according to the application obtains the first curve and the second curve, and determines whether the initial position angle of the motor has deviation according to the intersection position of the first curve and the second curve, thereby verifying the accuracy of the initial position angle. The method has simple steps, solves the problem of complicated operation steps in the prior art, is easy for the operator to master, and is easy to implement in the engineering field, thereby improving the reliability and usability of the motor product.

[0050] In some embodiments, the step of dragging the motor to a fixed rotating speed further comprises: dragging the motor to a fixed rotating speed by using a motor test bench device. The motor test bench device is a kind of motor test device, which is used to simulate various working conditions of the motor during operation, and meanwhile collects relevant data of the motor such as rotating speed, torque, current, power and the like. The step of measuring the torque of the motor further comprises: measuring the torque of the motor by using a torque sensor, wherein the torque sensor is installed on the output shaft of the motor test bench.

[0051] In some embodiments, the angle of the preset interval is -85° to -95°, and the current control angle corresponding to the case that the current is fully loaded to the d-axis is -90°. The preset interval can be set according to actual needs. In motor control, the motor is controlled by the amplitude of the current and the current control angle, different current control angles will make the motor output different torques, and the direction and size of the torque will be different. In the embodiments, the current control angle is -90° to 0°, which is the motoring working condition, at this time the motor output torque is in the same direction as the rotating speed, and the mechanical power is positive; when the current control angle is -90° to -180°, it is the generating working condition, at this time the motor output torque is opposite to the rotating speed, and the mechanical power is negative. In an example, the step of measuring the torque of the motor comprises: measuring the torque of the motor every 0.5° interval in the preset interval. The degree of each interval can be set according to actual needs.

[0052] In some embodiments, the step of determining whether the initial position angle of the motor has deviation according to the intersection position of the first curve and the second curve in step S108 comprises:

[0053] Suppose that the current control angle corresponding to the case that the current is fully loaded to the d-axis is an error-free angle; if the current control angle corresponding to the intersection position of the first curve and the second curve is equal to the error-free angle, it is determined that the initial position angle has no error; if the current control angle corresponding to the intersection position of the first curve and the second curve is not equal to the error-free angle, it is determined that the initial position angle has an error. The first curve and the second curve are displayed on the display. When the included angle of the first curve and the second curve is small, the view at the intersection position can be enlarged to better identify the degree of the current control angle corresponding to the intersection position.

[0054] Specifically, if the current control angle corresponding to the intersection position of the first curve and the second curve is not equal to the error-free angle, determining that the initial position angle has an error includes: if the current control angle corresponding to the intersection position of the first curve and the second curve is greater than the error-free angle, determining that the deviation of the initial position angle is positive; if the current control angle corresponding to the intersection position of the first curve and the second curve is less than the error-free angle, determining that the deviation of the initial position angle is negative. The angle of the deviation can be calculated, and the deviation can be used by an on-site operator as a basis for correcting the initial angle of the rotor next time.

[0055] In the correction of the initial angle of the rotor, reference is made to Figure 5 When the intersection position is close to the 0° direction, that is, the current control angle corresponding to the intersection position of the first curve and the second curve is less than the error-free angle, it indicates that the initial angle of the rotor is too small at this time, and the increased initial angle of the rotor should be written to the motor controller by the upper computer. Reference is made to Figure 4 When the intersection position is close to the -180° direction, that is, the current control angle corresponding to the intersection position of the first curve and the second curve is greater than the error-free angle, it indicates that the initial angle of the rotor is too large at this time, and the decreased initial angle of the rotor should be written to the motor controller by the upper computer. After the motor controller writes the modified initial angle of the rotor, steps S102 to S108 are executed again to verify whether the initial position angle of the motor has a deviation, and if there is still a deviation, the initial angle of the rotor is modified again and steps S102 to S108 are executed again until the initial position angle of the motor has no deviation.

[0056] The method for verifying the initial position angle of the synchronous motor in the embodiment of the application has a measurement error of only ±3 digital quantities through actual measurement, compared with a measurement error of ±10 digital quantities in the prior art, and the accuracy of verifying the initial position angle of the synchronous motor is improved.

[0057] It should be noted that, in the description of the application, the terms "first", "second", etc. are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, in the description of the application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0058] In the application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixed connection, or detachable connection, or integrated; can be mechanical connection, or electrical connection or communication with each other; can be directly connected, or indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0059] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature is "over", "above" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature is "under", "below" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0060] In the description of the present application, the terms "left", "right", "front", "back", and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0061] Any process or method descriptions or any other descriptions herein can be understood as representing embodiments of implementations comprising a computer- readable medium or machine-readable medium encoded with a set of instructions for implementation for one or more steps or functions represented in the flow diagram or described in this specification, and the terms "coupled", "connected", and "responsive", along with the like terms, should not be understood in an actual physical sense, but can be understood more conceptually unless otherwise indicated herein with actual physical descriptions.

[0062] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0063] Although the embodiments of the present application have been shown and described above, it should be understood that the above-described embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method of verifying an initial position angle of a synchronous electric machine, characterized in that, The method comprises: dragging the motor to a fixed speed; applying a first current to the motor, adjusting the angle change of the current control angle in a preset interval, measuring the torque of the motor, and obtaining a first curve according to the correspondence between the current control angle and the torque, wherein the preset interval includes the value of the current control angle corresponding to the case that the current is fully loaded to the d-axis; applying a second current to the motor, adjusting the angle change of the current control angle in the preset interval, measuring the torque of the motor, and obtaining a second curve according to the correspondence between the current control angle and the torque, wherein the second current is not equal to the first current; determining whether the initial position angle of the motor has a deviation according to the intersection position of the first curve and the second curve; The determination of whether the initial position angle of the motor has a deviation according to the intersection position of the first curve and the second curve specifically comprises: the current control angle corresponding to the case that the current is fully loaded to the d-axis is an error-free angle; if the current control angle corresponding to the intersection position of the first curve and the second curve is equal to the error-free angle, it is determined that the initial position angle has no error; if the current control angle corresponding to the intersection position of the first curve and the second curve is not equal to the error-free angle, it is determined that the initial position angle has an error; if the current control angle corresponding to the intersection position of the first curve and the second curve is greater than the error-free angle, it is determined that the deviation of the initial position angle is positive; if the current control angle corresponding to the intersection position of the first curve and the second curve is less than the error-free angle, it is determined that the deviation of the initial position angle is negative.

2. The method of verifying an initial position angle of a synchronous electric machine of claim 1, wherein, The dragging of the motor to a fixed speed comprises: dragging the motor to a fixed speed by using a motor test bench device.

3. The method of verifying an initial position angle of a synchronous machine of claim 1, wherein, The angle of the preset interval is -85° to -95°, and the current control angle corresponding to the case that the current is fully loaded to the d-axis is -90°.

4. The method of verifying an initial position angle of a synchronous machine of claim 2, wherein, The measurement of the torque of the motor comprises: measuring the torque of the motor by using a torque sensor, wherein the torque sensor is installed on the output shaft of the motor test bench.

5. The method of verifying an initial position angle of a synchronous machine of claim 1, wherein, The first current is less than the second current, and the second current is twice the first current.

6. The method of verifying an initial position angle of a synchronous machine of claim 1, wherein, The measurement of the torque of the motor comprises: in the preset interval, the torque of the motor is measured every 0.5°.

7. The method of verifying an initial position angle of a synchronous machine of claim 1, wherein, The application of the first current and the second current, the adjustment of the current control angle, and the modification of the initial position angle are all realized by the control of an upper computer on a motor controller, the motor controller is connected with the motor, and the upper computer is communicatively coupled with the motor controller.

8. The method of verifying an initial position angle of a synchronous machine according to any one of claims 1 to 7, characterized in that, The motor is a permanent magnet synchronous motor or an electrically excited synchronous motor.

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