Permanent magnet synchronous motor permanent magnet temperature online prediction method and system

Abstract

The invention relates to the technical field of permanent magnet temperature prediction, and particularly discloses a permanent magnet synchronous motor permanent magnet temperature online prediction method and system, and the method comprises the steps: obtaining a residual magnetism temperature coefficient according to the brand and category of a to-be-detected permanent magnet synchronous motor permanent magnet; according to a q-axis voltage equation of the permanent magnet synchronous motor, calculating a permanent magnet flux linkage amplitude at the current temperature; taking the permanent magnet flux linkage amplitude at the reference temperature point as a flux linkage base value; calculating a per-unit permanent magnet flux linkage amplitude according to the current permanent magnet flux linkage amplitude and the flux linkage base value; constructing a permanent magnet temperature prediction mathematical model according to the per-unit permanent magnet flux linkage amplitude, the residual magnetism temperature coefficient and the reference temperature point; and performing real-time prediction on the permanent magnet temperature in the operation process of the permanent magnet synchronous motor based on the permanent magnet temperature prediction mathematical model. The method does not need an additional sensor, can directly reflect the temperature state of the permanent magnet, and has high measurement precision.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet temperature prediction technology, and more specifically to an online prediction method and system for permanent magnet synchronous motor permanent magnet temperature. Background Technology

[0002] Magnetic synchronous motors are widely used in many industries due to their high efficiency, high power factor, and high power density. One of the core components of a permanent magnet synchronous motor is the permanent magnet, typically made of rare-earth materials such as neodymium iron boron. Its performance is closely related to temperature. Excessive temperature can not only cause irreversible demagnetization of the permanent magnet, potentially rendering the motor unusable, but also affect its operating efficiency and control accuracy, and even lead to system failures. Since the permanent magnet is generally mounted on the rotor, its temperature is difficult to measure directly, which increases the difficulty of providing overheat warnings and protection for the permanent magnet.

[0003] Traditional temperature measurement methods involve directly measuring the temperature by embedding a temperature sensor on or inside the permanent magnet. Although this method is intuitive and the measurement results are relatively reliable, it has significant drawbacks. The installation of the sensor requires special structural provisions during the motor design and manufacturing stage, which is complex and significantly increases the manufacturing cost of the motor. It may also damage the mechanical integrity and insulation performance of the motor. Furthermore, it is almost impossible to retrofit motors that are already in operation.

[0004] Another approach utilizes the characteristic that the resistance of the motor stator winding increases with temperature. The winding temperature is estimated by identifying the winding resistance online, and the permanent magnet temperature is indirectly inferred based on a certain thermal coupling relationship. However, since there is thermal resistance between the permanent magnet and the winding, the error in inferring the permanent magnet temperature indirectly from the winding temperature is relatively large, making it difficult to meet the requirement of accurate early warning of permanent magnet overheating in high-reliability applications.

[0005] Therefore, how to provide a method for predicting the temperature of permanent magnets with high accuracy that does not require external sensors and can directly reflect the temperature state of permanent magnets has become a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of the above problems, the present invention proposes an online prediction method and system for the permanent magnet temperature of a permanent magnet synchronous motor, so as to overcome the above problems or at least partially solve the above problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for online prediction of the temperature of permanent magnets in a permanent magnet synchronous motor, comprising the following steps: Based on the brand and type of the permanent magnet in the permanent magnet synchronous motor under test, obtain the remanence temperature coefficient; Calculate the permanent magnet flux linkage amplitude at the current temperature based on the q-axis voltage equation of the permanent magnet synchronous motor; The amplitude of the permanent magnet flux at the reference temperature point is used as the flux base value. Calculate the per-unit permanent magnet flux linkage amplitude based on the current permanent magnet flux linkage amplitude and flux linkage base value; A mathematical model for predicting the temperature of permanent magnets is constructed based on the standardized permanent magnet flux linkage amplitude, remanence temperature coefficient, and reference temperature point. The permanent magnet temperature is predicted in real time based on a mathematical model for permanent magnet temperature prediction during the operation of a permanent magnet synchronous motor.

[0008] Furthermore, the mathematical model for predicting the temperature of permanent magnets is expressed as follows:

[0009] in, This indicates the current temperature of the permanent magnet. This represents the per-unit amplitude of the permanent magnet flux linkage at the current moment. Indicates the temperature coefficient of remanence. This indicates the temperature at the reference point.

[0010] Furthermore, the per-unit permanent magnet flux linkage amplitude The calculation formula is:

[0011] in, Indicates the current temperature of the permanent magnet The amplitude of the permanent magnet flux linkage below, Indicates the reference temperature point The amplitude of the permanent magnet flux linkage.

[0012] Current permanent magnet temperature The formula for calculating the amplitude of the permanent magnet flux linkage is:

[0013] in, The rotor angular frequency, The voltage along the d-axis. For d-axis current, For q-axis current, For stator resistance, For D-axis inductance, It is the Q-axis inductance.

[0014] Furthermore, it also includes: pre-constructing a database to characterize the relationship between permanent magnet material brands, categories, and remanence temperature coefficients, where permanent magnet material brands serve as the first-level index, and the categories under each permanent magnet material serve as the second-level index, and the remanence temperature coefficients required at the moment are retrieved from the relational database.

[0015] In a second aspect, the present invention provides an online prediction system for the permanent magnet temperature of a permanent magnet synchronous motor, comprising a permanent magnet synchronous motor vector control module and a permanent magnet temperature prediction module; The permanent magnet temperature prediction module is used to predict the permanent magnet temperature of a permanent magnet synchronous motor online according to the prediction method described in any one of claims 1-5. The permanent magnet synchronous motor vector control module provides the relevant operating parameters required for the permanent magnet temperature prediction module to perform calculations.

[0016] Furthermore, the permanent magnet synchronous motor vector control module includes a current conversion unit, a d-axis current adjustment unit, a q-axis current adjustment unit, a PARK inverse conversion unit, an SVPWM unit, and a speed observation unit; The current conversion unit is used to convert the three-phase line current of the permanent magnet synchronous motor into current feedback values ​​in a two-phase rotating dq coordinate system. , ; The input to the d-axis current adjustment unit is the d-axis current command. and current feedback value The difference is output as the d-axis voltage. ; The input to the q-axis current adjustment unit is the q-axis current command. and current feedback value The difference is output as the q-axis voltage. ; The input to the velocity observation unit is the current feedback value in the two-phase rotating dq coordinate system. , and voltage , The output is the real-time speed of the permanent magnet synchronous motor. ; The PARK inverse transform unit converts the voltage in the two-phase rotating dq coordinate system. Transformed into two-phase stationary Voltage in coordinate system ; The SVPWM unit is based on two-phase stationary... Voltage in coordinate system Calculate the PWM pulse duty cycle of the three-phase inverter bridge, which is used to drive the three-phase inverter bridge of the permanent magnet synchronous motor.

[0017] Furthermore, the permanent magnet synchronous motor vector control module also includes an integrator unit, which calculates the real-time speed of the permanent magnet synchronous motor. Calculate the rotor position of a permanent magnet motor .

[0018] Furthermore, the permanent magnet synchronous motor vector control module provides the permanent magnet temperature prediction module with the relevant operating parameters required for calculation, including: voltage in the two-phase rotating dq coordinate system. Current feedback value and and real-time rotation speed .

[0019] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: This invention eliminates the need to install any temperature sensing elements on the permanent magnet or inside the motor. It calculates the electrical quantity of permanent magnet flux in real time using existing current and voltage signals, and infers the temperature by observing the changes in flux amplitude in real time. This allows for a more direct and sensitive reflection of the temperature rise of the permanent magnet itself, significantly improving prediction accuracy and reliability.

[0020] The core of the temperature prediction mathematical model constructed in this invention lies in the inherent remanence temperature coefficient of the permanent magnet material and the pre-calibrated reference temperature point flux linkage base value. These two parameters are easily obtained through factory testing and exhibit good material consistency and stability. It eliminates the need for knowledge of complex motor geometry, material thermal properties, heat dissipation boundary conditions, and other parameters that are difficult to obtain precisely, greatly reducing reliance on prior knowledge. The entire process involves minimal computation, making it highly suitable for embedding into existing motor drive controllers for real-time operation. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0022] Figure 1 This is a flowchart of the online prediction method for permanent magnet temperature of a permanent magnet synchronous motor provided in an embodiment of the present invention; Figure 2 This is a dynamic model of a permanent magnet synchronous motor in a two-phase rotating dq coordinate system provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure of the online temperature prediction system for permanent magnet synchronous motors provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1 As shown in the figure, an embodiment of the present invention discloses an online prediction method for the temperature of permanent magnets in a permanent magnet synchronous motor, comprising the following steps: Based on the brand and type of the permanent magnet in the permanent magnet synchronous motor under test, obtain the remanence temperature coefficient; Calculate the permanent magnet flux linkage amplitude at the current temperature based on the q-axis voltage equation of the permanent magnet synchronous motor; The amplitude of the permanent magnet flux at the reference temperature point is used as the flux base value. Calculate the per-unit permanent magnet flux linkage amplitude based on the current permanent magnet flux linkage amplitude and flux linkage base value; A mathematical model for predicting the temperature of permanent magnets is constructed based on the standardized permanent magnet flux linkage amplitude, remanence temperature coefficient, and reference temperature point. The permanent magnet temperature is predicted in real time based on a mathematical model for permanent magnet temperature prediction during the operation of a permanent magnet synchronous motor.

[0025] The mathematical model for predicting the temperature of permanent magnets is expressed as follows:

[0026] in, This indicates the current temperature of the permanent magnet. This represents the per-unit amplitude of the permanent magnet flux linkage at the current moment. Indicates the temperature coefficient of remanence. This indicates the temperature at the reference point.

[0027] The derivation process of the mathematical model for predicting the temperature of permanent magnets is explained in detail below: The permanent magnet materials used in permanent magnet synchronous motors are typically rare-earth permanent magnet materials, such as neodymium iron boron (NdFeB) magnets. These materials possess high coercivity and high remanence, making them ideal for manufacturing high-performance permanent magnet synchronous motors. The magnetic properties of permanent magnet materials are usually described by remanence and coercivity. Remanence Remanence refers to the magnetic flux density remaining in a magnet after the magnetic field disappears; it is an important parameter of permanent magnet materials after magnetization. Generally, the remanence density of permanent magnet materials increases with increasing temperature. It will decrease.

[0028] permanent magnet synchronous motor rotor permanent magnet flux amplitude With remanence density They are in a direct proportional relationship: (1) magnetic flux base value (2) Per unit value of permanent magnet flux linkage: (3) In the above formula, N is the number of turns of the coil, and S is the cross-sectional area. This is the base flux linkage value. The remanence density of the permanent magnet at 20℃.

[0029] As temperature increases, the remanence density of permanent magnet materials decreases. It will decrease, while the amplitude of the permanent magnet flux linkage With remanence density The relationship is directly proportional, therefore the amplitude of the permanent magnet flux linkage It also decreases as the temperature rises. Therefore, this invention calculates the amplitude of the permanent magnet flux linkage in real time using an observer during the operation of the permanent magnet motor. Based on the amplitude of the permanent magnet flux linkage The change in temperature can be used to predict the temperature of the permanent magnet motor magnet.

[0030] like Figure 2 As shown, the ABC axis is the vector reference axis of the permanent magnet motor in a three-phase stationary coordinate system, and the dq axis is the reference axis in a two-phase synchronous rotating coordinate system. These are the dq-axis voltage and dq-axis current components, respectively. This represents the amplitude of the permanent magnet flux linkage. The rotor angular frequency, This is the rotor position angle.

[0031] In the two-phase synchronous rotating dq coordinate system, the voltage equation of the permanent magnet synchronous motor is as follows: (4) In the above formula For stator resistance, For D-axis inductance, It is the Q-axis inductance.

[0032] The amplitude of the permanent magnet flux can be obtained from the q-axis voltage equation. The calculation formula is as follows: (5) Let the base value of the magnetic flux linkage be Divide both sides of the above equation by The standardized permanent magnet flux linkage amplitude can then be obtained. The calculation formula is as follows: (6) When performing online prediction of the permanent magnet temperature of a permanent magnet synchronous motor, it is necessary to query the brand and category of the permanent magnet material of the permanent magnet synchronous motor and obtain the remanence temperature coefficient from the permanent magnet material manufacturer. Based on this coefficient, the relationship between magnetic flux amplitude and temperature can be derived: (7) In the above formula, and At temperature T and reference temperature points, respectively. Remanence density (typically at 20℃).

[0033] Multiplying both the numerator and denominator on the right side of equation (7) by N*S, we get: (8) Substituting equation (1) into equation (8) above, we get: (9) In the above formula, and At temperature T and reference temperature points, respectively. (Generally 20℃) permanent magnet flux linkage; among which, during the commissioning phase, the inverter's own parameter self-learning function is utilized to ensure the motor is at a known reference temperature. In this state, an identification program is automatically run to measure and record the amplitude of the permanent magnet flux linkage at that temperature. .

[0034] make (10) Divide both the numerator and denominator on the right side of equation (9) by the magnetic flux base value. We can obtain: (11) Based on the above formula, the formula for calculating the temperature of permanent magnets can be derived: (12) Substituting equations (6) and (10) into the above equation, we can obtain the formula for predicting the temperature of permanent magnets: (13) In another embodiment, such as Figure 3 As shown, the present invention also provides an online prediction system for the permanent magnet temperature of a permanent magnet synchronous motor, including a permanent magnet synchronous motor vector control module and a permanent magnet temperature prediction module; The permanent magnet temperature prediction module is used to predict the permanent magnet temperature of the permanent magnet synchronous motor online according to the prediction method described above. The permanent magnet synchronous motor vector control module is connected to the permanent magnet synchronous motor (PMSM) and provides the relevant operating parameters required for calculation to the permanent magnet temperature prediction module.

[0035] The permanent magnet synchronous motor vector control module includes a current conversion unit, a d-axis current adjustment unit ACR-d, a q-axis current adjustment unit ACR-q, a PARK inverse conversion unit, an SVPWM unit, and a speed observation unit. The current conversion unit is used to convert the three-phase line current of the permanent magnet synchronous motor into current feedback values ​​in a two-phase rotating dq coordinate system. , ; The input to the d-axis current adjustment unit is the d-axis current command. and current feedback value The difference is output as the d-axis voltage. ; The input to the q-axis current adjustment unit is the q-axis current command. and current feedback value The difference is output as the q-axis voltage. ; The input to the velocity observation unit is the current feedback value in the two-phase rotating dq coordinate system. , and voltage , The output is the real-time speed of the permanent magnet synchronous motor. The speed regulator ASR adjusts the speed based on the speed error (given reference speed). Compared with actual speed The difference between the output and output q-axis current is given. ; The PARK inverse transform unit converts the voltage in the two-phase rotating dq coordinate system. Transformed into two-phase stationary Voltage in coordinate system ; The SVPWM unit is based on two-phase stationary... Voltage in coordinate system Calculate the PWM pulse duty cycle of the three-phase inverter bridge, which is used to drive the three-phase inverter bridge of the permanent magnet synchronous motor.

[0036] The permanent magnet synchronous motor vector control module provides the permanent magnet temperature prediction module with the relevant operating parameters required for calculation, including: voltage in the two-phase rotating dq coordinate system. Current feedback value and and real-time rotation speed The permanent magnet temperature prediction module predicts the temperature according to these parameters and its own stored intrinsic parameters in accordance with equation (13).

[0037] In other embodiments, the permanent magnet synchronous motor vector control module further includes an integrator unit, which adjusts the integrator unit based on the real-time rotational speed of the permanent magnet synchronous motor. Calculate the rotor position of a permanent magnet motor .

[0038] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for online prediction of permanent magnet temperature in a permanent magnet synchronous motor, characterized in that, Includes the following steps: Based on the brand and type of the permanent magnet in the permanent magnet synchronous motor under test, obtain the remanence temperature coefficient; Calculate the permanent magnet flux linkage amplitude at the current temperature based on the q-axis voltage equation of the permanent magnet synchronous motor; The amplitude of the permanent magnet flux at the reference temperature point is used as the flux base value. Calculate the per-unit permanent magnet flux linkage amplitude based on the current permanent magnet flux linkage amplitude and flux linkage base value; A mathematical model for predicting the temperature of permanent magnets is constructed based on the standardized permanent magnet flux linkage amplitude, remanence temperature coefficient, and reference temperature point. The permanent magnet temperature is predicted in real time based on a mathematical model for permanent magnet temperature prediction during the operation of a permanent magnet synchronous motor.

2. The online prediction method for permanent magnet temperature of a permanent magnet synchronous motor as described in claim 1, characterized in that, The mathematical model for predicting the temperature of permanent magnets is expressed as follows: in, This indicates the current temperature of the permanent magnet. This represents the per-unit amplitude of the permanent magnet flux linkage at the current moment. Indicates the temperature coefficient of remanence. This indicates the temperature at the reference point.

3. The online prediction method for permanent magnet temperature of a permanent magnet synchronous motor as described in claim 1, characterized in that, Perimeter-sized permanent magnet flux linkage amplitude The calculation formula is: in, Indicates the current temperature of the permanent magnet The amplitude of the permanent magnet flux linkage below, Indicates the reference temperature point The amplitude of the permanent magnet flux linkage.

4. The method for online prediction of permanent magnet temperature in a permanent magnet synchronous motor as described in claim 1, characterized in that, Current permanent magnet temperature The formula for calculating the amplitude of the permanent magnet flux linkage is: in, The rotor angular frequency, The voltage along the d-axis. For d-axis current, For q-axis current, For stator resistance, For D-axis inductance, It is the Q-axis inductance.

5. The method for online prediction of permanent magnet temperature in a permanent magnet synchronous motor as described in claim 1, characterized in that, Also includes: A database is pre-built to characterize the relationship between permanent magnet material brand, category, and remanence temperature coefficient. The permanent magnet material brand serves as the first-level index, and the category under each permanent magnet material serves as the second-level index. The required remanence temperature coefficient is retrieved from the relational database.

6. An online temperature prediction system for permanent magnet synchronous motor permanent magnets, characterized in that, Includes a permanent magnet synchronous motor vector control module and a permanent magnet temperature prediction module; The permanent magnet temperature prediction module is used to predict the permanent magnet temperature of a permanent magnet synchronous motor online according to the prediction method described in any one of claims 1-5. The permanent magnet synchronous motor vector control module provides the relevant operating parameters required for the permanent magnet temperature prediction module to perform calculations.

7. The online temperature prediction system for permanent magnet synchronous motor permanent magnets as described in claim 6, characterized in that, The permanent magnet synchronous motor vector control module includes a current conversion unit, a d-axis current adjustment unit, a q-axis current adjustment unit, a PARK inverse conversion unit, an SVPWM unit, and a speed observation unit; The current conversion unit is used to convert the three-phase line current of the permanent magnet synchronous motor into current feedback values ​​in a two-phase rotating dq coordinate system. , ; The input to the d-axis current adjustment unit is the d-axis current command. and current feedback value The difference is output as the d-axis voltage. ; The input to the q-axis current adjustment unit is the q-axis current command. and current feedback value The difference is output as the q-axis voltage. ; The input to the velocity observation unit is the current feedback value in the two-phase rotating dq coordinate system. , and voltage , The output is the real-time speed of the permanent magnet synchronous motor. ; The PARK inverse transform unit converts the voltage in the two-phase rotating dq coordinate system. Transformed into two-phase stationary Voltage in coordinate system ; The SVPWM unit is based on two-phase stationary... Voltage in coordinate system Calculate the PWM pulse duty cycle of the three-phase inverter bridge, which is used to drive the three-phase inverter bridge of the permanent magnet synchronous motor.

8. The online temperature prediction system for permanent magnet synchronous motor permanent magnets as described in claim 7, characterized in that, The permanent magnet synchronous motor vector control module also includes an integrator unit, which calculates the real-time speed of the permanent magnet synchronous motor. Calculate the rotor position of a permanent magnet motor .

9. The online temperature prediction system for permanent magnet synchronous motor permanent magnets as described in claim 7, characterized in that, The permanent magnet synchronous motor vector control module provides the permanent magnet temperature prediction module with the relevant operating parameters required for calculation, including: voltage in the two-phase rotating dq coordinate system. Current feedback value and and real-time rotation speed .

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