A method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method

Abstract

The present invention provides a method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method, which relates to the technical field of motors. The method includes constructing a finite element model, setting the rotor angular frequency, and calculating the back electromotive force amplitude and synchronous reactance under specific working conditions; performing at least two groups of parameter settings on the model, short-circuiting the three-phase winding circuit, and calculating the three-phase short-circuit current waveform; for the three-phase short-circuit current waveforms under different groups of parameters, selecting a specific phase to calculate the waveform difference; performing a spectral analysis on the waveform difference, and calculating the subtransient reactance parameter under the initial rotor position condition according to the relevant parameters of specific spectral components, the back electromotive force amplitude, and the synchronous reactance; changing the initial rotor position, and taking the average value of the subtransient reactance parameters at multiple positions as the final result. The present invention considers the influence of rotor eddy currents, and based on the finite element method, accurately and efficiently estimates the subtransient reactance through multi-step calculations and parameter adjustments, helping to optimize the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of motors, and particularly to a method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method. Background Art

[0002] In the field of modern power engineering, with the continuous optimization of high-performance rare earth permanent magnet materials and the continuous progress of advanced electromagnetic design technologies, permanent magnet motors, especially permanent magnet wind generators, have achieved remarkable improvements in terms of power density, reliability, and adaptability to complex working conditions. Their applications in wind turbine generators are becoming increasingly widespread and gradually becoming one of the key technical solutions in the field of wind power generation. Relying on its unique advantages, permanent magnet wind generators demonstrate great potential in improving energy conversion efficiency and reducing maintenance costs, making important contributions to sustainable energy development.

[0003] The subtransient reactance is a crucial parameter in the field of motors. For wound synchronous motors, it plays an irreplaceable role in describing the current characteristics at the initial stage of motor short-circuit faults or other sudden disturbances. Although there is no traditional damping winding on the rotor of a permanent magnet wind generator, eddy currents are generated between the rotor permanent magnet and the iron core due to the alternating magnetic field, thereby producing an effect similar to that of the damping winding of a wound synchronous motor. As a result, the subtransient reactance parameter also becomes a key indicator for evaluating the performance of permanent magnet wind generators. Accurately calculating the subtransient reactance is of great significance for evaluating the short-circuit current level of the generator. This parameter is directly related to the optimization of the protection configuration of the power system and the improvement of operation reliability. In the actual operation of the power system, the setting values of protection devices must be accurately set based on the subtransient parameters of the generator. Accurately calculating the subtransient reactance can effectively improve the response accuracy of relay protection devices, reduce the risk of misoperation, ensure that the power system can quickly isolate faults when a fault occurs, minimize the scope of the fault impact, and ensure the safe and stable operation of the power system.

[0004] For wound synchronous motors, there are currently relatively mature methods for calculating subtransient reactance parameters. However, due to the essential difference in the rotor structure between permanent magnet wind generators and wound synchronous motors, there is no winding on their rotors. Although the eddy currents between the rotor permanent magnet and the iron core can produce an effect similar to that of the damping winding, the eddy current distribution is usually uneven. This structural difference makes the calculation methods for wound synchronous motors unable to be directly applied to the calculation of subtransient reactance parameters of permanent magnet wind generators and cannot accurately reflect the current characteristics of permanent magnet wind generators during short-circuit faults or transient processes.

[0005] A method for calculating the sub-transient reactance parameters of a permanent magnet wind generator is proposed in the literature "Short - Circuit Analysis of Permanent - Magnet Generators". Based on the structural parameters of the generator, this method first solves the inductance coefficient of the generator, then separates the inductance parameters into the air - gap main inductance and the slot leakage inductance, and multiplies the main inductance by a coefficient related to k to calculate the sub - transient inductance under the influence of rotor eddy currents. However, this method has obvious defects:

[0006] Calculation accuracy problem: The sub - transient reactance parameters mainly play a significant role in the fault state or transient process. However, the existing technology obtains the sub - transient reactance parameters through the operating parameters of the generator under steady - state operation, and cannot accurately capture the true electromagnetic characteristics of the motor in the initial stage of the fault or transient, resulting in inaccurate calculation results and unable to provide a reliable basis for the protection configuration of the power system.

[0007] Implementation difficulty and error problem: In terms of implementation means, this method requires separating the air - gap main inductance, which involves complex calculations and physical model processing, and has a greater implementation difficulty. And various errors are easily introduced during the separation process, such as inductance parameter measurement errors, model simplification errors, etc. These errors accumulate continuously during the calculation process, ultimately resulting in a large deviation between the calculated sub - transient reactance parameters and the actual values, affecting the safe and stable operation of the power system.

[0008] In summary, there are many deficiencies in the existing technology for calculating the sub - transient reactance parameters of permanent magnet wind generators. There is an urgent need for a method that can accurately and efficiently calculate this parameter to meet the requirements of the power system for the performance evaluation and protection configuration of permanent magnet wind generators. Summary of the Invention

[0009] Therefore, the embodiments of the present invention provide a method for estimating the sub - transient reactance of a surface - mounted permanent magnet motor based on the finite - element method, which is used to solve the problem that the calculation method of wound - rotor synchronous motors is not applicable due to the special rotor structure of permanent magnet wind generators in the existing technology, and the defects of the existing calculation methods for permanent magnet wind generators in terms of accuracy, implementation difficulty and error, and thus unable to accurately evaluate the short - circuit current level of the generator and optimize the protection configuration of the power system.

[0010] To solve the above problems, the embodiments of the present invention provide a method for estimating the sub - transient reactance of a surface - mounted permanent magnet motor based on the finite - element method, and this method includes:

[0011] S1: Construct a finite - element model of a surface - mounted permanent magnet wind motor, set the rotor angular frequency in the finite - element model to a specific value, and calculate the back - electromotive force amplitude and synchronous reactance of the finite - element model under specific working conditions;

[0012] S2: Perform at least two different parameter settings on the finite element calculation model. Under each set of parameter settings, keep the winding circuit in a three-phase short-circuit state, and calculate the three-phase short-circuit current waveforms within one electrical cycle. Each set of parameter settings includes the setting of the stator winding resistance, the setting of the electrical conductivities of the rotor core and the permanent magnet, and the setting of the initial rotor position.

[0013] S3: For the three-phase short-circuit current waveforms obtained under different sets of parameter settings, select the short-circuit current waveforms of a specific phase for difference calculation to obtain the differences in the short-circuit current waveforms of this specific phase under different sets of parameter settings.

[0014] S4: Conduct a frequency spectrum analysis on the differences in the short-circuit current waveforms to determine the relevant parameters of specific frequency spectrum components. Based on these relevant parameters, the back electromotive force amplitude, and the synchronous reactance, calculate the subtransient reactance parameters under the initial rotor position condition.

[0015] S5: Return to step S2, change the initial rotor position, obtain the subtransient reactance parameters under multiple initial rotor positions, and calculate their average value as the final subtransient reactance parameter.

[0016] Preferably, in step S1, the specific operating condition is the normal operating state of the motor, and the specific value is the rated value.

[0017] Preferably, in step S2, the setting of the stator winding resistance includes setting it to zero.

[0018] Preferably, in step S2, the setting of the electrical conductivities of the rotor core and the permanent magnet includes at least two different set values, one of which is zero and the other is within the conventional range.

[0019] Preferably, the conventional range is 10 4 S / m - 10 6 S / m.

[0020] Preferably, in step S4, the method for conducting a frequency spectrum analysis on the differences in the short-circuit current waveforms to determine the relevant parameters of specific frequency spectrum components is as follows:

[0021] Conduct a Fourier decomposition on the differences in the short-circuit current waveforms and select the amplitude of the first harmonic of the differences in the short-circuit current waveforms.

[0022] Preferably, in step S4, the method for calculating the subtransient reactance parameters under the initial rotor position condition based on these relevant parameters, the back electromotive force amplitude, and the synchronous reactance is as follows:

[0023] ;

[0024] where represents the subtransient reactance, represents the back electromotive force amplitude, represents the synchronous reactance, represents the amplitude of the first harmonic of the short-circuit current waveform difference.

[0025] Preferably, in step S5, the range for changing the initial rotor position is 0 - 180°, and the step size is a preset value.

[0026] The embodiment of the present invention also provides a system for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method. This system is used to implement the method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method as described above, and specifically includes:

[0027] A model construction and parameter acquisition module, which is used to construct a finite element model of a surface-mounted permanent magnet wind power motor, set the rotor angular frequency in the finite element model to a specific value, and calculate the back electromotive force amplitude and synchronous reactance of the finite element model under specific working conditions;

[0028] A short-circuit current calculation module, which is used to perform at least two sets of different parameter settings on the finite element calculation model, make the winding circuit in a three-phase short-circuit state under each set of parameter settings, and calculate the three-phase short-circuit current waveforms within one electrical cycle, where each set of parameter settings includes stator winding resistance setting, rotor core and permanent magnet conductivity setting, and rotor initial position setting;

[0029] A current waveform processing module, which is used to perform difference calculation on the short-circuit current waveforms of a specific phase selected from the three-phase short-circuit current waveforms obtained under different sets of parameter settings, and obtain the short-circuit current waveform differences of this specific phase under different sets of parameter settings;

[0030] A spectrum analysis and reactance calculation module, which is used to perform spectrum analysis on the short-circuit current waveform differences, determine the relevant parameters of specific spectral components, and calculate the subtransient reactance parameters under the rotor initial position condition based on these relevant parameters, back electromotive force amplitude, and synchronous reactance;

[0031] An average calculation module, which is used to return to the short-circuit current calculation module, change the rotor initial position, obtain the subtransient reactance parameters under multiple rotor initial positions, and calculate their average value as the final subtransient reactance parameter.

[0032] Preferably, the short-circuit current calculation module includes:

[0033] A first short-circuit current calculation unit, which is used to calculate the three-phase short-circuit current waveforms when the stator winding resistance is a specific value, the rotor core and permanent magnet conductivity are specific values representing no rotor eddy current effect, and the rotor initial position is a specific value;

[0034] The second short-circuit current calculation unit is used to calculate the three-phase short-circuit current waveform when the stator winding resistance is a same specific value, the conductivities of the rotor core and the permanent magnet are specific values representing the actual or approximate actual rotor eddy current effect, and the initial rotor position is a same specific value.

[0035] As can be seen from the above technical solutions, the present invention application has the following beneficial effects:

[0036] (1) Based on the finite element method, the present invention comprehensively considers various factors and accurately calculates the subtransient reactance parameters. By constructing a model and performing calculation and analysis under different parameter settings, the problem of inaccurate calculation in the prior art is effectively solved, providing a reliable basis for accurately evaluating the short-circuit current and dynamic response level of the generator, strongly promoting the optimization of the power system protection configuration, and enhancing the stability and reliability of the power system.

[0037] (2) The present invention proposes a clear and feasible estimation method with definite operation steps. It overcomes the defects of great implementation difficulty and large error in the prior art, avoids complex operations, and has strong operability. General R & D personnel can quickly calculate parameters accordingly, improving the calculation efficiency, facilitating wide application in the industry, and promoting the development of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly describe the drawings required in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be construed as limiting the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0039] Figure 1 It is a flowchart of a method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method provided in the embodiment;

[0040] Figure 2 It is a schematic diagram of the finite element model of a surface-mounted permanent magnet wind turbine in the embodiment;

[0041] Figure 3 It is a schematic diagram of the three-phase short-circuit current waveform when the rotor eddy current is not considered in the embodiment;

[0042] Figure 4 It is a schematic diagram of the three-phase short-circuit current waveform when the rotor eddy current is considered in the embodiment;

[0043] Figure 5 It is a schematic diagram of the current difference when the rotor eddy current is considered and not considered in the embodiment;

[0044] Figure 6 It is a schematic diagram of the subtransient reactance under different initial rotor positions in the embodiment;

[0045] Figure 7 It is a block diagram of a system for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method provided in the embodiment. Specific implementation manner

[0046] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0047] To solve the problems in the prior art that the calculation method of the wound synchronous motor is not applicable due to the special rotor structure of the permanent magnet wind turbine generator, and the existing calculation methods of the permanent magnet wind turbine generator have defects in terms of accuracy, implementation difficulty and error, and thus it is impossible to accurately evaluate the short-circuit current level of the generator and optimize the protection configuration of the power system. As Figure 1 shown, an embodiment of the present invention proposes a method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method, and the method includes:

[0048] S1: Construct a finite element model of a surface-mounted permanent magnet wind turbine motor, set the rotor angular frequency in the finite element model to a specific value, and calculate the back electromotive force amplitude and synchronous reactance of the finite element model under specific working conditions;

[0049] S2: Perform at least two groups of different parameter settings on the finite element calculation model, and make the winding circuit in a three-phase short-circuit state under each group of parameter settings, and calculate the three-phase short-circuit current waveforms within one electrical cycle, where each group of parameter settings includes the setting of the stator winding resistance, the setting of the conductivity of the rotor core and the permanent magnet, and the setting of the initial rotor position;

[0050] S3: For the three-phase short-circuit current waveforms obtained under different groups of parameter settings, select the short-circuit current waveforms of a specific phase for difference calculation to obtain the short-circuit current waveform differences of the specific phase under different groups of parameter settings;

[0051] S4: Perform spectral analysis on the short-circuit current waveform differences, determine the relevant parameters of a specific spectral component, and calculate the subtransient reactance parameters under the initial rotor position condition based on the relevant parameters, the back electromotive force amplitude and the synchronous reactance;

[0052] S5: Return to step S2, and change the initial rotor position to obtain subtransient reactance parameters under multiple initial rotor positions, and calculate their average value as the final subtransient reactance parameter.

[0053] As can be seen from the above technical solution, the present invention proposes a method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method. By constructing a finite element model of a surface-mounted permanent magnet wind turbine and setting the rotor angular frequency to a specific value, the back electromotive force amplitude and synchronous reactance under specific working conditions are calculated, laying a foundation for subsequent calculations. Then, multiple groups of different parameter settings (covering the stator winding resistance, the conductivity of the rotor core and permanent magnet, and the initial rotor position) are carried out. Under the three-phase short-circuit state, the three-phase short-circuit current waveform is obtained. The waveform difference is calculated for a specific phase. After determining the relevant parameters through spectrum analysis, the subtransient reactance parameter under the initial rotor position condition is calculated. Then, the rotor initial position is changed and the operation is repeated to obtain the average value. This technical solution fully considers the rotor structure characteristics of the permanent magnet wind turbine and the influence of rotor eddy current under short-circuit faults, overcomes the defects of the existing technology such as the inapplicability of the calculation method due to the special rotor structure, poor accuracy, high implementation difficulty, and large error, can accurately estimate the subtransient reactance parameter, thereby accurately evaluating the short-circuit current and dynamic response level, effectively optimizing the power system protection configuration, and is easy to operate. Generally, R & D personnel can quickly calculate based on this, and the operability is strong.

[0054] In step S1, a finite element model of a surface-mounted permanent magnet wind turbine is constructed using finite element simulation software, as Figure 2 shown ( Figure 2 PM1, PM2, ···, PM10 in it refer to the permanent magnet part in the surface-mounted permanent magnet wind turbine of the present invention), and its main parameters are shown in Table 1. The rotor angular frequency in the finite element model is set to the rated value, and the back electromotive force amplitude and synchronous reactance of the finite element model under the normal operation state of the motor are calculated.

[0055] Table 1 Motor parameters

[0056]

[0057] Furthermore, the current expression under the three-phase short-circuit state is:

[0058] ;

[0059] where the known quantities include the current , time , back electromotive force amplitude , armature time constant , synchronous reactance , frequency , rotor initial position angle , and the two unknown quantities, subtransient reactance and subtransient time constant .

[0060] In step S2, at least two different sets of parameter settings are made for the finite element calculation model. Under each set of parameter settings, the winding circuit is in a three-phase short-circuit state, and the three-phase short-circuit current waveforms within one electrical cycle are calculated. Each set of parameter settings includes the stator winding resistance setting, the conductivity settings of the rotor core and the permanent magnet, and the rotor initial position setting, specifically including:

[0061] In the above finite element model, the stator winding resistance is set to 0, the conductivity of the rotor core and the permanent magnet is set to 0, the rotor initial position is set to 0, the winding circuit is connected in a three-phase short-circuit state, and the three-phase short-circuit current within one electrical cycle is calculated. The three-phase current waveforms are respectively denoted as A1, B1, and C1.

[0062] Specifically, the stator winding resistance is set to 0, the conductivity of the rotor core and the permanent magnet is set to 0. The calculated back electromotive force amplitude is 800V and the synchronous reactance is 1.466Ω. At the same time, the three-phase short-circuit current waveforms of the motor within one electrical cycle with the rotor initial position being 0 are calculated, as Figure 3 shown.

[0063] Further, based on the same finite element model, the stator winding resistance is set to 0, the conductivities of the rotor core and the permanent magnet are respectively set to the conventional levels, generally 10 4 S / m - 10 6 S / m, the rotor initial position is set to 0, the winding circuit is connected in a three-phase short-circuit state, and the three-phase short-circuit current within one electrical cycle is calculated. The three-phase current waveforms are respectively denoted as A2, B2, and C2.

[0064] The stator winding resistance remains set to 0, the conductivities of the rotor core and the permanent magnet are respectively set to 9930000 S / m and 625000 S / m. The three-phase short-circuit current waveforms of the motor within one electrical cycle with the rotor initial position being 0 are calculated, as Figure 4 shown.

[0065] In step S3, for the three-phase short-circuit current waveforms obtained under different sets of parameter settings, the short-circuit current waveforms of a specific phase (phase A) are selected for difference calculation to obtain the short-circuit current waveform differences of this specific phase under different sets of parameter settings, and the waveforms are as shown in Figure 5 shown.

[0066] In step S4, the short-circuit current waveform differences are subjected to Fourier decomposition, and the amplitude of the 1st harmonic of the short-circuit current waveform differences is selected, which is 2457.5A. And based on the 1st harmonic amplitude, the back electromotive force amplitude, and the synchronous reactance, the subtransient reactance parameters under the rotor initial position condition are calculated :

[0067] ;

[0068] Among them, represents the amplitude of the back electromotive force represents the synchronous reactance represents the amplitude of the first harmonic of the difference in short-circuit current waveforms. Then, under the current conditions, the subtransient reactance parameter can be calculated according to the above formula as 1.401 Ω

[0069] In step S5, return to step S2 and change the initial rotor position, where the range of changing the initial rotor position is 0 - 180°, and the step size of change is a preset value (preferably 10°). Repeat steps S2 to S4 to obtain the subtransient reactance parameters under multiple initial rotor positions and calculate their average value as the final subtransient reactance parameter. As Figure 6 shown, the average value of the subtransient reactance under different initial rotor positions finally is 1.400 Ω Embodiment 2

[0070] As Figure 7 shown, the present invention provides a system for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method. This system is used to implement the method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method in the above-mentioned Embodiment 1, and specifically includes:

[0071] A model construction and parameter acquisition module 100, which is used to construct a finite element model of a surface-mounted permanent magnet wind turbine, set the rotor angular frequency in the finite element model to a specific value, and calculate the amplitude of the back electromotive force and the synchronous reactance of the finite element model under specific working conditions

[0072] A short-circuit current calculation module 200, which is used to perform at least two groups of different parameter settings on the finite element calculation model, make the winding circuit in a three-phase short-circuit state under each group of parameter settings, and calculate the three-phase short-circuit current waveforms within one electrical cycle, where each group of parameter settings includes the setting of the stator winding resistance, the setting of the conductivity of the rotor core and the permanent magnet, and the setting of the initial rotor position

[0073] A current waveform processing module 300, which is used to select the short-circuit current waveforms of a specific phase for difference calculation for the three-phase short-circuit current waveforms obtained under different groups of parameter settings, and obtain the difference in the short-circuit current waveforms of this specific phase under different groups of parameter settings

[0074] A spectrum analysis and reactance calculation module 400, which is used to perform spectrum analysis on the difference in short-circuit current waveforms, determine the relevant parameters of specific spectral components, and calculate the subtransient reactance parameters under the initial rotor position conditions based on these relevant parameters, the amplitude of the back electromotive force, and the synchronous reactance

[0075] The average calculation module 500 is used to return the short-circuit current calculation module 200, change the initial rotor position, obtain the sub-transient reactance parameters under multiple initial rotor positions, and calculate their average value as the final sub-transient reactance parameter.

[0076] Furthermore, the short-circuit current calculation module 200 includes:

[0077] The first short-circuit current calculation unit is used to calculate the three-phase short-circuit current waveform when the stator winding resistance is a specific value, the conductivities of the rotor core and the permanent magnet are specific values representing no rotor eddy current effect, and the initial rotor position is a specific value.

[0078] The second short-circuit current calculation unit is used to calculate the three-phase short-circuit current waveform when the stator winding resistance is the same specific value, the conductivities of the rotor core and the permanent magnet are specific values representing the actual or approximate actual rotor eddy current effect, and the initial rotor position is the same specific value.

[0079] A system for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method in this embodiment is used to implement the foregoing method for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method. Therefore, the specific implementation manners in the system for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method can be seen in the embodiment part of the foregoing method for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method. For example, the model construction and parameter acquisition module 100, the short-circuit current calculation module 200, the current waveform processing module 300, the spectrum analysis and reactance calculation module 400, and the average calculation module 500 are respectively used to implement steps S1, S2, S3, S4, and S5 in the foregoing method for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method. Therefore, their specific implementation manners can refer to the descriptions of the corresponding individual embodiment parts. To avoid redundancy, they will not be elaborated here.

[0080] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0081] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, so that the instructions executed by the processors of the computer or other programmable data processing devices generate means for implementing the functions specified in one or more flows and / or one or more blocks. Figure 1 in one or more flows and / or one or more blocks Figure 1 of the means for implementing the functions specified in the block or blocks.

[0082] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in one or more flows and / or one or more blocks. Figure 1 in one or more flows and / or one or more blocks Figure 1 of the block or blocks. These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more flows and / or one or more blocks. Figure 1 in one or more flows and / or one or more blocks Figure 1 of the block or blocks.

[0083] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method, characterized in that Including: S1: Construct a finite element model of a surface-mounted permanent magnet wind turbine generator, set the rotor angular frequency in the finite element model to the rated value, and calculate the back electromotive force amplitude and synchronous reactance of the finite element model under the normal operating state of the motor; S2: Perform at least two different parameter settings on the finite element model. Under each parameter setting, make the winding circuit in a three-phase short-circuit state, and calculate the three-phase short-circuit current waveform within one electrical cycle, where each parameter setting includes stator winding resistance setting, rotor core and permanent magnet conductivity setting, and rotor initial position setting; S3: For the three-phase short-circuit current waveforms obtained under different parameter settings, select the short-circuit current waveform of phase A for difference calculation to obtain the short-circuit current waveform difference of phase A under different parameter settings; S4: Perform spectral analysis on the short-circuit current waveform difference to determine the fundamental harmonic amplitude of the short-circuit current waveform difference. Calculate the subtransient reactance parameter under the rotor initial position condition based on the fundamental harmonic amplitude, back electromotive force amplitude, and synchronous reactance. The method for calculating the subtransient reactance parameter under the rotor initial position condition based on the fundamental harmonic amplitude, back electromotive force amplitude, and synchronous reactance is: where X d ″ represents the subtransient reactance, E q1 represents the magnitude of the back electromotive force, X d represents the synchronous reactance, and I1 represents the magnitude of the first harmonic of the difference in the short-circuit current waveform; S5: Return to step S2, change the rotor initial position, obtain the subtransient reactance parameters under multiple rotor initial positions, and calculate their average value as the final subtransient reactance parameter.

2. The method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method according to claim 1, characterized in that, In step S2, the stator winding resistance setting includes setting it to zero.

3. The method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method according to claim 1, characterized in that, In step S2, the rotor core and permanent magnet conductivity setting includes at least two different setting values, one of which is zero and the other is within the conventional range.

4. The method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method according to claim 3, wherein The conventional range is 10 4 S / m - 10 6 S / m.

5. The method for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method according to claim 1, characterized in that In step S4, the method for performing spectral analysis on the short-circuit current waveform difference to determine the fundamental harmonic amplitude of the short-circuit current waveform difference is: Perform Fourier decomposition on the short-circuit current waveform difference and select the fundamental harmonic amplitude of the short-circuit current waveform difference.

6. The method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method according to claim 1, wherein In step S5, the range for changing the rotor initial position is 0 - 180°, and the step size for change is a preset value.

7. A system for estimating the sub-transient reactance of a surface-mounted permanent magnet motor based on the finite element method, characterized in that, The system is used to implement the method for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method according to any one of claims 1 to 6, specifically including: A model construction and parameter acquisition module, which is used to construct a finite element model of a surface-mounted permanent magnet wind turbine generator, set the rotor angular frequency in the finite element model to the rated value, and calculate the back electromotive force amplitude and synchronous reactance of the finite element model under the normal operating state of the motor; A short-circuit current calculation module, which is used to perform at least two different parameter settings on the finite element model. Under each parameter setting, make the winding circuit in a three-phase short-circuit state, and calculate the three-phase short-circuit current waveform within one electrical cycle, where each parameter setting includes stator winding resistance setting, rotor core and permanent magnet conductivity setting, and rotor initial position setting; A current waveform processing module, which is used to, for the three-phase short-circuit current waveforms obtained under different parameter settings, select the short-circuit current waveform of phase A for difference calculation to obtain the short-circuit current waveform difference of phase A under different parameter settings; A spectrum analysis and reactance calculation module is used to perform spectrum analysis on the difference in short-circuit current waveforms, determine the fundamental harmonic amplitude of the difference in short-circuit current waveforms, and calculate the sub-transient reactance parameters under the initial rotor position condition based on the fundamental harmonic amplitude, back electromotive force amplitude, and synchronous reactance; An average calculation module is used to return to the short-circuit current calculation module, change the initial rotor position, obtain the sub-transient reactance parameters under multiple initial rotor positions, and calculate their average value as the final sub-transient reactance parameter.

8. The system for estimating the subtransient reactance of a surface-mounted permanent magnet motor based on the finite element method according to claim 7, characterized in that, The short-circuit current calculation module includes: A first short-circuit current calculation unit is used to calculate the three-phase short-circuit current waveform when the stator winding resistance is 0, the rotor core and permanent magnet conductivity are 0, and the initial rotor position is 0; The second short-circuit current calculation unit is used to calculate the three-phase short-circuit current waveform when the stator winding resistance is 0, the conductivity of the rotor core and the permanent magnet is 10 4 S / m - 10 6 S / m, and the initial position of the rotor is 0

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