Permanent magnet synchronous motor steady-state three-phase short-circuit characteristic evaluation method, device and medium

Abstract

This invention relates to the field of permanent magnet synchronous motor (PMSM) technology, specifically to a method, device, and medium for evaluating the steady-state three-phase short-circuit characteristics of a PMSM. The method includes: acquiring a pre-generated dataset characterizing the electromagnetic characteristics of the motor; correcting the dataset according to a preset operating temperature; and using a two-step iterative algorithm to determine the current operating point under short-circuit conditions. This algorithm first, under a fixed initial value for the d-axis current, performs a first iteration on the q-axis current to find the q-axis current that brings the d-axis voltage close to zero. Then, based on this q-axis current, a second iteration is performed to find the d-axis current that brings the q-axis voltage close to zero. Finally, the drag torque is calculated based on the determined current operating point. This invention eliminates the need for the original FEA model and achieves rapid and accurate evaluation of the three-phase short-circuit characteristics of the motor through an efficient dimensionality reduction iterative algorithm, making it particularly suitable for the safety analysis of the power system of electric vertical takeoff and landing (EVL) aircraft.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, specifically to a method, device, and medium for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors are widely used in high-performance fields such as electric vehicles and aerospace due to their advantages such as high power density and high efficiency. In applications with extremely high safety requirements, such as electric vertical takeoff and landing aircraft, the electric drive system may enter a three-phase winding short circuit state during flight due to controller failure or external physical impact.

[0003] Under three-phase short-circuit conditions, the motor rotor rotates like a windmill under the influence of airflow, generating a huge short-circuit current and a reverse electromagnetic torque, i.e., drag torque. The magnitude of this drag torque directly determines the stable speed of the motor under short-circuit conditions, thus affecting the thermal management and structural safety of the entire system. Therefore, accurately assessing the steady-state three-phase short-circuit characteristics of the motor at different speeds, especially the drag torque, is crucial for the safety design and airworthiness certification of aircraft.

[0004] Currently, there are two main methods for evaluating the three-phase short-circuit characteristics of motors. The first is the hardware bench test method, which involves using a dynamometer to drive the motor under test and directly measuring its torque, current, and other parameters under three-phase short-circuit conditions. While direct, this method is costly, time-consuming, and carries the risk of burning out the motor under extreme conditions. The second method is the software simulation method, which uses finite element analysis (FEA) software to model the motor and obtain an FEA model to simulate its electromagnetic behavior under three-phase short-circuit conditions. The accuracy of this method depends on a precise motor model, which typically contains the motor supplier's core design parameters and material information. For manufacturers, obtaining this original FEA model is often difficult, making it impossible to conduct detailed simulation evaluations independently.

[0005] Therefore, there is an urgent need for an evaluation scheme for the three-phase short-circuit characteristics of permanent magnet synchronous motors that can avoid high-cost and high-risk physical experiments, does not have to rely on the confidential original FEA model, and can also ensure the accuracy of the evaluation results. Summary of the Invention

[0006] This invention aims to address the problems of high cost, high risk, and difficulty in implementation due to the lack of access to the original FEA model when evaluating the three-phase short-circuit characteristics of permanent magnet synchronous motors (PMSMs) in existing technologies. This invention provides a method, apparatus, and medium for evaluating the steady-state three-phase short-circuit characteristics of PMSMs. This method does not rely on the original FEA model of the motor; instead, it utilizes only the generated discrete dataset and an efficient iterative algorithm to accurately and quickly evaluate key characteristics of the motor under three-phase short-circuit conditions, such as drag torque.

[0007] To achieve the above objectives, this invention provides a method for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor (PMSM) based on finite element analysis simulation data. The method includes: acquiring a pre-generated dataset characterizing the electromagnetic characteristics of the PMSM under different operating conditions; the dataset includes the stator resistance and permanent magnet flux linkage of the PMSM, as well as the d-axis and q-axis flux linkage recorded at different motor speeds, currents, and current angle scan points; performing temperature correction on the dataset according to a preset motor operating temperature to obtain a corrected dataset; and, in the dq rotating coordinate system, based on a fixed d-axis current, performing a first iteration... The process iteratively solves for the q-axis current value, and in each iteration, calculates the d-axis voltage using the q-axis flux linkage obtained from the corrected dataset, until the absolute value of the d-axis voltage reaches its minimum. Based on the solved q-axis current value, a second iteration process iteratively solves for the d-axis current value, and in each iteration, calculates the q-axis voltage using the d-axis flux linkage obtained from the corrected dataset, until the absolute value of the q-axis voltage reaches its minimum, thereby determining the current operating point under three-phase short-circuit conditions. Based on the current operating point, the drag torque of the motor under three-phase short-circuit conditions is determined from the corrected dataset. This scheme decomposes the two-dimensional search problem for finding the short-circuit operating point into two independent one-dimensional iterative processes, improving solution efficiency and convergence stability.

[0008] In some embodiments, the step of temperature correction of the dataset may include:

[0009] Based on the preset stator winding operating temperature, the stator resistance is corrected using the resistance-temperature formula; and based on the preset rotor permanent magnet operating temperature, the permanent magnet flux linkage in the dataset is corrected using the permanent magnet demagnetization characteristics. This step allows the evaluation results to more closely approximate the actual physical performance of the motor at a specific operating temperature, thereby improving the accuracy of the evaluation.

[0010] In some embodiments, the first iteration process includes:

[0011] Based on the physical characteristic that the d-axis current dominates during a short circuit, an initial value for the d-axis current is fixed, and the value of the q-axis current is iteratively scanned until the absolute value of the d-axis voltage calculated according to the permanent magnet synchronous motor voltage equation and the corrected dataset reaches its minimum. The permanent magnet synchronous motor voltage equation includes the d-axis voltage equation. ,in The voltage along the d-axis. The corrected stator resistance. For d-axis current, The electrical angular velocity corresponding to the current motor speed. Let be the q-axis flux linkage.

[0012] In some embodiments, to improve the efficiency of the first iteration process, the method further includes: first determining the current amplitude that minimizes the peak value of the motor phase voltage at the current motor speed, and setting the initial value of the d-axis current to a negative value of the current amplitude. This utilizes the correlation between the short-circuit current and the current at the minimum voltage point, providing a good initial guess for the iteration.

[0013] In some embodiments, the second iteration process includes:

[0014] Based on the solved q-axis current value, the d-axis current value is iteratively fine-tuned until the absolute value of the q-axis voltage calculated according to the permanent magnet synchronous motor voltage equation and the corrected dataset reaches its minimum. The permanent magnet synchronous motor voltage equation includes the q-axis voltage equation. ,in This is the q-axis voltage. The corrected stator resistance. For q-axis current, The electrical angular velocity corresponding to the current motor speed. This step involves precise correction of the d-axis current to ensure that the final current operating point simultaneously satisfies the short-circuit condition where both the d-axis and q-axis voltages are zero.

[0015] In some embodiments, determining the drag torque of the motor under a three-phase short-circuit condition from the corrected dataset based on the current operating point includes:

[0016] Based on the d-axis current and q-axis current included in the current operating point, the corresponding d-axis flux linkage and q-axis flux linkage are obtained by interpolation from the corrected dataset;

[0017] The drag torque is calculated using the electromagnetic torque formula, which is as follows: ,in For drag torque, This represents the number of pole pairs of the motor. The d-axis flux linkage, The q-axis current is... For the q-axis magnetic flux, Let be the d-axis current.

[0018] In some embodiments, the method may further include: repeatedly performing iterative solutions to the current operating point and determining the drag torque for multiple different motor speed points within the operating speed range, to obtain the three-phase short-circuit drag torque characteristic curve of the motor within the operating speed range. This curve can fully show the law of drag torque variation with speed, and is a key basis for safety assessment.

[0019] In some embodiments, the method may further include: determining the final stable speed of the motor under a three-phase short-circuit state based on the drag torque characteristic curve, for use in the safety assessment of the electric vertical take-off and landing aircraft. For example, by comparing the drag torque curve with the aerodynamic torque curves of the aircraft propeller at different speeds, the torque balance point, i.e., the stable speed under the short-circuit state, can be found.

[0020] Secondly, the present invention also provides a device for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor, comprising: a data acquisition module for acquiring a pre-generated dataset characterizing the electromagnetic characteristics of the permanent magnet synchronous motor under different operating conditions; the dataset includes the stator resistance and permanent magnet flux linkage of the permanent magnet synchronous motor, as well as lookup tables recording the relationship between the d-axis flux linkage and the q-axis flux linkage and the current at different motor speeds and current scanning points;

[0021] The data correction module is used to perform temperature correction on the dataset according to the preset motor operating temperature to obtain the corrected dataset;

[0022] The first current calculation module is used to iteratively solve the q-axis current value in the dq rotating coordinate system based on the condition of a fixed d-axis current through a first iteration process, and to calculate the d-axis voltage in each iteration using the q-axis flux obtained from the corrected dataset, until the absolute value of the d-axis voltage reaches the minimum value.

[0023] The second current solving module is used to iteratively solve the d-axis current value based on the solved q-axis current value through a second iteration process, and to calculate the q-axis voltage using the d-axis flux obtained from the corrected dataset in each iteration until the absolute value of the q-axis voltage reaches the minimum value, thereby determining the current operating point under the three-phase short-circuit state.

[0024] The torque determination module is used to determine the drag torque of the motor under three-phase short-circuit conditions from the corrected dataset based on the current operating point.

[0025] Thirdly, the present invention also provides a computer-readable storage medium having stored thereon computer program instructions, which, when executed by a processor, implement the method described in the first aspect above.

[0026] Compared with existing technologies, this invention has the following advantages: First, it eliminates the need for costly and risky physical bench tests and the acquisition of the motor supplier's confidential original FEA model; evaluation can be completed using only the discrete dataset provided by the supplier, effectively circumventing intellectual property barriers and reducing evaluation costs and risks. Second, the two-step one-dimensional iterative algorithm proposed in this invention reduces the dimensionality of the complex two-dimensional optimization problem, resulting in high computational efficiency and good convergence. Compared with traditional analytical formula methods, it has lower dependence on the accuracy of motor parameters and stronger robustness. Finally, this invention considers the influence of temperature on motor resistance and flux linkage and makes corresponding corrections, making the evaluation results closer to the actual physical conditions and improving the accuracy and reliability of the evaluation. Attached Figure Description

[0027] Figure 1 A flowchart illustrating a method for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor, provided in an embodiment of the present invention;

[0028] Figure 2 This is a structural block diagram of a device for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor, provided in an embodiment of the present invention.

[0029] Figure 3 This is an example diagram of the three-phase short-circuit drag torque characteristic curve of a permanent magnet synchronous motor calculated according to an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail 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. In the description of the present invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0031] This invention proposes an efficient and accurate evaluation method to address the challenge of rapidly and cost-effectively assessing the critical safety characteristics, particularly the drag torque, of permanent magnet synchronous motors (PMSMs) in advanced aircraft such as electric vertical takeoff and landing (eVTOL) systems when a three-phase short circuit occurs. In aircraft electric drive systems, three-phase short circuits can occur due to controller active protection or external physical impacts. Accurately assessing the drag torque under these conditions is crucial for predicting the stable speed of the motor in windmill mode and evaluating system safety. Traditional methods rely on costly and risky bench tests or require original finite element analysis (FEA) models with intellectual property barriers from motor suppliers, both of which have significant limitations. The method provided in this invention utilizes an electromagnetic characteristic dataset generated from the original FEA model, free of sensitive information, to achieve accurate evaluation, effectively avoiding the aforementioned problems.

[0032] To facilitate understanding of the technical solution of this invention, the core terms involved are first defined. A dataset refers to a set of data generated in advance through finite element analysis simulation, characterizing the electromagnetic characteristics of a permanent magnet synchronous motor under different operating conditions. Specifically, it includes d-axis and q-axis flux linkages recorded at different motor speeds and currents, as well as at current angle scan points. The generation process of this dataset does not consider the limitation of the DC bus voltage. Driving torque refers to the electromagnetic torque generated by the motor under a three-phase short-circuit state, which impedes rotor rotation. The current operating point is the d-axis current that uniquely determines the three-phase short-circuit state of the motor in the dq rotating coordinate system. ) and q-axis current ( The first iteration process refers to the calculation process in the dq rotating coordinate system, based on the condition of a fixed d-axis current, iteratively solving for the q-axis current value until the d-axis voltage reaches its minimum value. The second iteration process refers to the calculation process based on the obtained q-axis current value, iteratively solving for the d-axis current value until the absolute value of the q-axis voltage reaches its minimum value.

[0033] Reference Figure 1This paper illustrates the flowchart of a method for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor (PMSM) according to an embodiment of the present invention. The first step (S1) of this method is to obtain a pre-generated dataset characterizing the electromagnetic characteristics of the PMSM under different operating conditions. This dataset is typically generated by the motor designer using FEA software (such as JMAG, MotorCAD, etc.) to model the motor's geometry, materials, and other information, followed by electromagnetic simulation scanning. Specifically, the dataset exists in the form of a lookup table, recording the d-axis flux linkage and q-axis flux linkage corresponding to different current amplitudes and current angles at multiple discrete motor speed points. It should be noted that the generation process of this dataset does not include limitations on the DC bus voltage; that is, the simulation does not consider whether the back electromotive force will exceed the actual bus voltage. This approach ensures that the dataset itself does not contain operating limitation information related to a specific inverter, thereby avoiding intellectual property issues that may arise from directly using a complete FEA model and providing a pure electromagnetic characteristic of the motor itself for subsequent calculations.

[0034] After obtaining the original dataset, the method proceeds to the second step (S2), which involves temperature correction of the dataset based on a preset motor operating temperature to obtain the corrected dataset. Since the motor's resistance and the flux linkage of the permanent magnets are closely related to temperature, and the original dataset is typically generated at a reference temperature (e.g., 25°C), temperature correction is necessary to ensure that the evaluation results more closely reflect the actual physical state of the motor during a short-circuit fault. This step enables the evaluation results to reflect the motor performance under specific thermal conditions, significantly improving the accuracy and practical value of the evaluation.

[0035] Specifically, the step of temperature correction for the dataset can include two aspects. First, based on a preset stator winding operating temperature, the stator resistance is corrected using a resistance-temperature formula. For example, a reasonable stator copper wire operating temperature can be assumed, such as 120°C, and then the formula can be applied. The reference resistance values ​​used in the dataset are corrected, where It is the resistance at the target temperature. It is the reference temperature The resistance below, This refers to the temperature coefficient of resistance of copper. On the other hand, based on a preset rotor permanent magnet operating temperature, the permanent magnet flux linkage in the dataset is corrected using the demagnetizing characteristics of the permanent magnet. For example, a reasonable rotor magnet operating temperature, such as 100°C, can be assumed, and the permanent magnet flux linkage component in the dataset can be proportionally reduced according to the temperature-dependent demagnetizing coefficient of the permanent magnet material. These two corrections ensure that the motor parameters used in subsequent calculations better reflect actual harsh operating conditions, thereby guaranteeing the reliability of the final evaluation results.

[0036] After data preparation, the method proceeds to the third step (S3) iterative solution stage. The third step (S3) involves iteratively solving for the q-axis current value in the dq rotating coordinate system, based on the condition of a fixed d-axis current, through the first iteration process. The physical basis for this is that in a three-phase short-circuit steady-state permanent magnet synchronous motor, the d-axis current typically accounts for the majority of the short-circuit current, while the q-axis current component is relatively small. Utilizing this physical characteristic, the original solution that needed to be obtained in the (…) , The complex problem of searching for solutions in a two-dimensional plane is reduced to two one-dimensional search problems, which greatly simplifies the calculation and improves the convergence speed. In each iteration, the process uses the q-axis flux linkage obtained from the corrected dataset to calculate the corresponding d-axis voltage until d reaches its minimum value. The q-axis current value at this point is the result of the first step.

[0037] In the first iteration, the specific operation involves fixing an initial value for the d-axis current and iteratively scanning the value of the q-axis current. Setting the initial value of the d-axis current is crucial for efficient iteration. A preferred approach is to first determine, at the currently evaluated motor speed, the current amplitude that minimizes the peak value of the motor phase voltage by analyzing the dataset, and then set the initial value of the d-axis current to a negative value of that current amplitude. This is because, under short-circuit conditions, the d-axis current acts as a demagnetizer, and its sign is typically negative. The calculation of the d-axis voltage follows the standard voltage equation for permanent magnet synchronous motors, i.e. .in, The voltage along the d-axis. This is the stator resistance after correction in the previous step. Let be the initial value of the d-axis current. The electrical angular velocity corresponding to the current motor speed ( , (Number of pole pairs of the motor) (Revolutions Per Minute) refers to the number of revolutions per minute. In the current ( , The q-axis flux linkage is obtained by table lookup or interpolation from the corrected dataset under the combined conditions. The iterative process can be derived from... Initially, the system scans in the negative direction with a first iteration step size. This first iteration step size can be selected based on the required solution accuracy and computational efficiency, for example, it can be taken as 0.5% to 2% of the absolute value of the initial value of the d-axis current. In this embodiment, it is taken as 0.1A, until a solution is found that satisfies the given conditions. of .

[0038] After obtaining an approximate q-axis current value through the first iteration, the method proceeds to the fourth step (S4), which involves iteratively solving for the d-axis current value through a second iteration based on the obtained q-axis current value. The purpose of this step is to... Under these conditions, further fine-tune the d-axis current to simultaneously satisfy... The conditions are used to find a more accurate short-circuit current operating point. In each iteration, the process uses the d-axis flux linkage obtained from the corrected dataset to calculate the corresponding q-axis voltage until the absolute value of the q-axis voltage reaches its minimum. The final result is ( , The combination represents the precise current operating point under three-phase short-circuit conditions at that speed.

[0039] Specifically, the second iterative process includes: iteratively fine-tuning the d-axis current value while keeping the solved q-axis current value fixed. The iteration can begin with the initial d-axis current value used in the first iteration and scan towards 0 with finer step sizes. The calculation of the q-axis voltage also follows the voltage equation of a permanent magnet synchronous motor, i.e. .in, This is the q-axis voltage. The corrected stator resistance. The q-axis current is obtained from the previous iteration. Electric angular velocity, In the current ( , The d-axis flux linkage is obtained by table lookup or interpolation from the corrected dataset under the combined condition. When a satisfactory value is found... The iteration terminates when the time is reached. This two-step iterative method, proceeding from primary to secondary steps and approximating each step sequentially, ensures the stability and efficiency of the algorithm.

[0040] For example, the finer step size in the second iteration can be 1 / 10 of the step size in the first iteration.

[0041] After accurately determining the current operating point ( , Following this, the final step (S5) of the method is to determine the drag torque of the motor under three-phase short-circuit conditions from the corrected dataset based on the current operating point. This is the final target output of the evaluation. (Using known...) , This allows for precise interpolation from the corrected dataset to obtain the d-axis flux linkage corresponding to the operating point. and q-axis flux Then, the drag torque can be calculated using the standard electromagnetic torque formula.

[0042] Wherein, the electromagnetic torque formula is: .in, For drag torque, This represents the number of pole pairs of the motor. and The flux linkage value we just obtained. and This determines the final operating point for the current. Since the calculated torque value is negative under short-circuit conditions, representing a hindering torque, it is called drag torque. This calculation step directly correlates the solved electrical quantity (current) with the mechanical quantity (torque), providing direct input for safety analysis.

[0043] To achieve the above method, the present invention also provides a device for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor. (Refer to...) Figure 2 The evaluation device can be a standalone computing unit or a functional module integrated into the motor controller or flight control computer. The device includes: a data acquisition module 21, used to acquire a pre-generated dataset characterizing the electromagnetic characteristics of the permanent magnet synchronous motor under different operating conditions; the dataset includes the stator resistance and permanent magnet flux linkage of the permanent magnet synchronous motor, as well as the d-axis flux linkage and q-axis flux linkage recorded at different motor speeds, currents, and current angle scanning points; a data correction module 22, used to perform temperature correction on the dataset according to a preset motor operating temperature to obtain a corrected dataset; and a first current solving module 23, used to iteratively solve the q-axis current value in the dq rotating coordinate system based on a fixed d-axis current, through a first iteration process, and in each iteration... The first module calculates the d-axis voltage using the q-axis flux linkage obtained from the corrected dataset until the absolute value of the d-axis voltage is less than a first preset threshold. The second current solving module 24 is used to iteratively solve the d-axis current value through a second iteration process based on the solved q-axis current value, and calculates the q-axis voltage using the d-axis flux linkage obtained from the corrected dataset in each iteration until the absolute value of the q-axis voltage reaches a minimum value, thereby determining the current operating point under three-phase short-circuit conditions. The torque determining module 25 is used to determine the drag torque of the motor under three-phase short-circuit conditions from the corrected dataset based on the current operating point. These modules can be implemented by hardware, software, or a combination thereof. For example, one or more processors can execute program instructions stored in memory to perform their respective functions.

[0044] The implementation process of the present invention will be described below with reference to a specific embodiment. Taking a 150kW built-in permanent magnet synchronous motor as an example, the steady-state three-phase short circuit situation of the motor at a speed of 1000rpm will be evaluated. First, execute... Figure 1The first step in the illustrated process is to acquire the dataset. Next, the actual operating temperatures are set; for example, assuming the stator winding operating temperature is 120℃ and the rotor permanent magnet operating temperature is 100℃, and the stator resistance and permanent magnet flux linkage in the dataset are corrected accordingly. Then, the iterative solution phase begins. At a speed of 1000 rpm, the current amplitude (388.2A) that minimizes the peak phase voltage of the motor (2.59V) is determined, and its negative value (-388.2A) is used as the initial value of the d-axis current. Subsequently, this value is fixed. Initial values, start the first iteration process, from Begin scanning in the negative direction, using the formula calculate until one is found The value makes It is close to zero (-0.0044V). Based on this, the value obtained is fixed. The value is used to initiate the second iteration process for fine-tuning. Using the formula calculate until It is also close to zero (-0.0015V). Through these two iterations, the final calculated current operating point under this condition is... A, At this point, the calculated voltage values ​​are verified as follows: V, The absolute values ​​of V are all very small, indicating that the solution is accurate. Finally, based on the obtained current operating point, the corresponding flux linkage value is obtained by interpolation from the corrected dataset. Wb, Wb. Substituting these values ​​into the electromagnetic torque formula The drag torque at that speed was calculated to be -40.0124 Nm. The entire process required no physical experiments or access to the complete FEA model; accurate evaluation was achieved solely through datasets and efficient algorithms.

[0045] Based on the above embodiments, the method of the present invention can be further extended to obtain the short-circuit characteristics of the motor throughout its entire operating range. Specifically, the complete steps from iteratively solving for the current operating point to determining the drag torque can be repeatedly executed for multiple different motor speed points within the motor's operating speed range. For example, in addition to the 1000 rpm speed point, other key speed points such as 5000 rpm and 10000 rpm can be selected to repeat the same evaluation process. For the same 150kW motor, at 5000 rpm, the current operating point calculated using the method of the present invention is... A, A corresponds to a drag torque of -9.4 Nm. At 10000 rpm, the calculated current operating point is... A, The corresponding drag torque is -6.4 Nm.

[0046] Reference Figure 3 By plotting these calculated data points on a coordinate system with motor speed as the horizontal axis and drag torque as the vertical axis, an exemplary three-phase short-circuit drag torque characteristic curve of a permanent magnet synchronous motor can be obtained. Figure 3 In the curve, data point P1 corresponds to (1000 rpm, -36 Nm), data point P2 corresponds to (5000 rpm, -8 Nm), and data point P3 corresponds to (10000 rpm, -5.8 Nm). This curve visually demonstrates the trend of drag torque as a function of rotational speed, providing a comprehensive data foundation for the safety analysis of eVTOL during short-circuit faults in different flight phases (such as high-speed cruise and low-speed hovering). This drag torque characteristic curve has high engineering application value, especially in the safety assessment of electric vertical takeoff and landing (EVL) aircraft. It can be used to determine the final stable speed of the motor under aerodynamic (windmill effect) drive only after a three-phase short-circuit fault. The motor speed reaches stability when the drag torque of the motor is balanced with the aerodynamic torque generated by the propeller under specific flight conditions. Through this stable speed, the relevant thermal effects and structural stresses can be evaluated, thus providing crucial data support for aircraft failure mode analysis and airworthiness certification.

[0047] The present invention also provides a computer-readable storage medium having computer program instructions stored thereon. The storage medium can be any form of non-volatile or volatile memory, such as read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive, or optical disk. When the computer program instructions stored on the computer-readable storage medium are loaded and executed by a processor, the processor will execute the aforementioned method for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor.

Claims

1. A method for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor, characterized in that, include: Obtain a pre-generated dataset characterizing the electromagnetic properties of the permanent magnet synchronous motor under different operating conditions; The dataset includes the stator resistance and permanent magnet flux linkage of the permanent magnet synchronous motor, as well as the d-axis flux linkage and q-axis flux linkage recorded at different motor speeds and currents, and current angle scan points. Based on the preset motor operating temperature, the dataset is temperature-corrected to obtain the corrected dataset; In the dq rotating coordinate system, based on the condition of a fixed d-axis current, the q-axis current value is iteratively solved through the first iteration process, and the d-axis voltage is calculated in each iteration using the q-axis flux obtained from the corrected dataset, until the absolute value of the d-axis voltage reaches the minimum value. Based on the solved q-axis current value, the d-axis current value is iteratively solved through the second iteration process, and the q-axis voltage is calculated using the d-axis flux obtained from the corrected dataset in each iteration until the absolute value of the q-axis voltage reaches the minimum value, thereby determining the current operating point under the three-phase short-circuit state. Based on the current operating point, the drag torque of the motor under three-phase short-circuit conditions is determined from the corrected dataset.

2. The method according to claim 1, characterized in that, The temperature correction of the dataset includes: Based on the preset stator winding operating temperature, the stator resistance is corrected using the resistance-temperature formula; and based on the preset rotor permanent magnet operating temperature, the permanent magnet flux linkage in the dataset is corrected using the permanent magnet demagnetization characteristics.

3. The method according to claim 1, characterized in that, The first iteration process includes: A fixed initial value for the d-axis current is obtained, and the value of the q-axis current is iteratively scanned until the absolute value of the d-axis voltage calculated based on the permanent magnet synchronous motor voltage equation and the corrected dataset reaches its minimum value. The voltage equations of the permanent magnet synchronous motor include the d-axis voltage equations. ,in The voltage along the d-axis. The corrected stator resistance. For d-axis current, The electrical angular velocity corresponding to the current motor speed. Let be the q-axis flux linkage.

4. The method according to claim 3, characterized in that, The method further includes: determining the current amplitude that minimizes the peak value of the motor phase voltage at the current motor speed, and setting the initial value of the d-axis current to a negative value of the current amplitude.

5. The method according to claim 1, characterized in that, The second iterative process includes: Based on the solved q-axis current value, the d-axis current value is iteratively fine-tuned until the absolute value of the q-axis voltage calculated according to the permanent magnet synchronous motor voltage equation and the corrected dataset reaches the minimum value. The voltage equations of the permanent magnet synchronous motor include the q-axis voltage equations. ,in This is the q-axis voltage. The corrected stator resistance. For q-axis current, The electrical angular velocity corresponding to the current motor speed. denoted as d-axis flux linkage.

6. The method according to claim 1, characterized in that, The step of determining the drag torque of the motor under three-phase short-circuit conditions from the corrected dataset based on the current operating point includes: Based on the d-axis current and q-axis current included in the current operating point, the corresponding d-axis flux linkage and q-axis flux linkage are obtained by interpolation from the corrected dataset; The drag torque is calculated using the electromagnetic torque formula, which is as follows: ,in For drag torque, This represents the number of pole pairs of the motor. The d-axis flux linkage, The q-axis current is... For the q-axis magnetic flux, Let be the d-axis current.

7. The method according to claim 1, characterized in that, The method further includes: For multiple different motor speed points within the operating speed range, the iterative steps of solving the current operating point and determining the drag torque are repeatedly executed to obtain the three-phase short-circuit drag torque characteristic curve of the motor within the operating speed range.

8. The method according to claim 7, characterized in that, The method further includes: Based on the towing torque characteristic curve, the final stable speed of the motor under three-phase short circuit conditions is determined, and the final stable speed is used for the safety assessment of the electric vertical take-off and landing aircraft.

9. A device for evaluating the steady-state three-phase short-circuit characteristics of a permanent magnet synchronous motor, characterized in that, include: The data acquisition module is used to acquire a pre-generated dataset that characterizes the electromagnetic properties of the permanent magnet synchronous motor under different operating conditions; The dataset includes the stator resistance and permanent magnet flux linkage of the permanent magnet synchronous motor, as well as the d-axis flux linkage and q-axis flux linkage recorded at different motor speeds and currents and circuit angle scan points. The data correction module is used to perform temperature correction on the dataset according to the preset motor operating temperature to obtain the corrected dataset; The first current calculation module is used to iteratively solve the q-axis current value in the dq rotating coordinate system based on the condition of a fixed d-axis current through a first iteration process, and to calculate the d-axis voltage in each iteration using the q-axis flux obtained from the corrected dataset, until the absolute value of the d-axis voltage reaches the minimum value. The second current solving module is used to iteratively solve the d-axis current value based on the solved q-axis current value through a second iteration process, and to calculate the q-axis voltage using the d-axis flux obtained from the corrected dataset in each iteration until the absolute value of the q-axis voltage reaches the minimum value, thereby determining the current operating point under the three-phase short-circuit state. The torque determination module is used to determine the drag torque of the motor under three-phase short-circuit conditions from the corrected dataset based on the current operating point.

10. A computer-readable storage medium having computer program instructions stored thereon, characterized in that, When the instruction is executed by the processor, it implements the method as described in any one of claims 1-8.

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