Permanent magnet synchronous motor demagnetization accounting method and system

Abstract

The application provides a permanent magnet synchronous motor demagnetization accounting method and system, which comprises the following steps: in a synchronous rotating coordinate system, according to the parameters of the motor, the initial conditions of the motor are calculated in a steady state to obtain the steady state initial conditions of the motor; according to the first dq flux linkage and the first dq current, the first dq flux linkage is calculated in a differential manner to obtain the first dq flux linkage differential value; the first dq flux linkage differential value is calculated in an integral manner to obtain the second dq flux linkage; according to the first dq current and the parameters of the motor, the first permanent magnet flux linkage is updated to obtain the second permanent magnet flux linkage; according to the second permanent magnet flux linkage and the second dq flux linkage, the second dq current is calculated in a back solution manner; and according to the second dq current and a preset current convergence threshold value, when the current reaches a steady state, the demagnetization accounting result is obtained. The calculation efficiency of the demagnetization accounting of the grid-connected damping winding permanent magnet synchronous motor is greatly improved under the premise of ensuring a certain calculation precision.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a method and system for calculating the demagnetization of a permanent magnet synchronous motor. Background Technology

[0002] When a permanent magnet synchronous motor is running, the combined magnetomotive force of the stator and rotor acts on the permanent magnets. When the maximum demagnetizing magnetomotive force, opposite to the magnetization direction, occurs, the magnetic flux density of the permanent magnets will be minimized, maximizing the risk of demagnetization. When the operating point of the permanent magnet falls below the inflection point of the demagnetization curve, the residual magnetic density recovers along the new recovery line, decreasing compared to the initial residual magnetic density, thus resulting in irreversible demagnetization. Many factors can cause permanent magnet demagnetization, such as demagnetization due to extreme temperatures, reverse magnetic fields, high-frequency vibration, corrosion, and demagnetization in locally weak structural areas. Therefore, it is necessary to perform demagnetization calculations for permanent magnet synchronous motors under fault conditions.

[0003] In the study of irreversible demagnetization of permanent magnet synchronous motors, finite element analysis (FEA) is widely used for demagnetization fault modeling, local magnetic field analysis, and performance degradation assessment due to its high modeling accuracy and spatial resolution. Researchers typically simulate faults such as uniform demagnetization, local demagnetization, permanent magnet breakage, and pole demagnetization by changing the remanence, coercivity, or equivalent volume of the permanent magnet, and further analyze their effects on air gap magnetic flux density, back EMF, electromagnetic torque, and torque ripple.

[0004] Analytical methods for demagnetization calculation of permanent magnet synchronous motors include the subdomain method (SDM), the magnetic equivalent circuit (MEC), and the subdomain method analytical model based on Maxwell's equations.

[0005] However, demagnetization analysis usually requires repeated solutions under different currents, temperatures, speeds, and rotor positions. Due to the complexity of FEA modeling and mesh generation, the calculation time is long when performing multi-condition solutions. At the same time, in the preliminary design stage of the motor, repeated FEA modeling and mesh generation will significantly reduce design efficiency due to frequent modifications to the motor structural parameters.

[0006] Traditional magnetic equivalent circuit methods typically assume that the magnetic flux is uniformly distributed in each magnetic circuit and treat the permanent magnet as a whole. While this approach simplifies modeling, it is difficult to accurately describe complex air gap magnetic fields, local saturation, end leakage magnetic fields, and local demagnetization in different regions within a single permanent magnet. In particular, it is difficult to analyze local irreversible demagnetization at different locations within a single permanent magnet.

[0007] The analytical models established by the traditional subdomain method usually rely on regular geometric boundaries and idealized assumptions. They are mostly used for surface-mounted permanent magnet synchronous motors with regular structures. When the motor has special structures such as complex slots, built-in magnets, and magnetic bridges, the analytical solution becomes significantly more difficult, and the model's versatility is limited.

[0008] likeFigure 1 The diagram shows a schematic of a permanent magnet synchronous motor with grid-connected damping windings. Existing finite element method, magnetic equivalent circuit and subdomain method are generally used for demagnetization calculation of permanent magnet synchronous motors with grid-connected damping windings. However, they have problems such as long calculation time under multiple working conditions, cumbersome modeling and mesh generation, insufficient ability to analyze complex structures and local demagnetization, and difficulty in fully considering the transient demagnetization effect generated by the damping winding current and stator current. Summary of the Invention

[0009] This invention provides a method for demagnetizing permanent magnet synchronous motors. Based on transient equivalent circuit models and equivalent magnetic circuit models, it proposes an analytical calculation method for rapid demagnetizing permanent magnet synchronous motors with grid-connected damping systems. This method avoids the problems of repeated modeling, mesh generation, and large-scale numerical solutions in traditional finite element methods. It is particularly suitable for rapid demagnetizing calculations under multiple operating conditions and structural parameters in the initial design stage of permanent magnet synchronous motors with grid-connected damping systems. The aim is to improve the speed of demagnetizing calculations for permanent magnet synchronous motors with grid-connected damping systems and reduce computational costs.

[0010] This invention provides a method for calculating the demagnetization of a permanent magnet synchronous motor, comprising the following steps: In a synchronous rotating coordinate system, steady-state calculations are performed on the initial conditions of the motor based on the motor parameters to obtain the steady-state initial conditions of the motor; wherein, the motor parameters include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current; The differential value of the first dq flux linkage is calculated based on the first dq flux linkage and the first dq current. The second dq flux linkage is obtained by integrating the differential value of the first dq flux linkage. Based on the first dq current and the parameters of the motor, the first permanent magnet flux linkage is updated to obtain the second permanent magnet flux linkage; The second dq current is obtained by inverse calculation based on the second permanent magnet flux linkage and the second dq flux linkage. Based on the second dq current and the preset current convergence threshold, the demagnetization calculation result is obtained when the current reaches a steady state.

[0011] The demagnetization calculation method for a permanent magnet synchronous motor provided by the present invention further includes: Based on the second dq current and the preset current convergence threshold, if it is determined that the current has not reached a steady state, the second dq current is assigned to the first dq current, the second dq flux is assigned to the first dq flux, and the second dq current is recalculated by inverse solving.

[0012] According to the present invention, a method for calculating the demagnetization of a permanent magnet synchronous motor includes, in which the steady-state initial conditions of the motor are calculated based on the motor parameters to obtain the steady-state initial conditions of the motor, comprising: Based on the three-phase current parameters, the stator current in the stationary coordinate system is calculated using Clark transformation; Based on the stator current in the stationary coordinate system, the first dq current in the synchronous rotating coordinate system is calculated using the Park transformation. The first dq flux linkage is calculated based on the first permanent magnet flux linkage and the first dq current.

[0013] According to the present invention, a method for demagnetizing a permanent magnet synchronous motor, wherein updating the first permanent magnet flux linkage based on the first dq current and motor parameters to obtain the second permanent magnet flux linkage includes: Based on the parameters of the permanent magnet, the magnetomotive force and magnetic reluctance within the permanent magnet are calculated. The demagnetizing magnetomotive force amplitude is calculated based on the motor parameters and the first dq current. Based on the motor parameters, the external magnetic reluctance of the motor's magnetic circuit is calculated; The magnetic flux of the permanent magnet is calculated based on the magnetomotive force inside the permanent magnet, the magnetic reluctance inside the permanent magnet, the amplitude of the demagnetizing magnetomotive force, and the external magnetic reluctance of the motor magnetic circuit. The magnetic flux density of the permanent magnet is calculated based on the magnetic flux and area of ​​the permanent magnet. Based on the magnetic flux density of the permanent magnet, and by using the demagnetization loop to determine when irreversible demagnetization of the permanent magnet occurs, the remanent magnetic flux density of the permanent magnet is updated to obtain the updated remanent magnetic flux density of the permanent magnet. The updated magnetomotive force within the permanent magnet is calculated based on the remanent magnetization of the permanent magnet. The magnetic flux of the permanent magnet is updated based on the magnetic potential within the permanent magnet to obtain the updated magnetic flux of the permanent magnet. The second permanent magnet flux is calculated based on the updated permanent magnet flux.

[0014] According to the demagnetization calculation method for a permanent magnet synchronous motor provided by the present invention, the step of calculating the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current includes:

[0015] in, , For the stator side voltage in the synchronous rotating coordinate system, For stator resistance, , , , For the first dq current, The angular frequency of the motor. , , , For the first dq magnet link, , This refers to the resistance of the damping winding in the synchronous rotating coordinate system.

[0016] According to the demagnetization calculation method for a permanent magnet synchronous motor provided by the present invention, the step of integrating the differential value of the first dq flux linkage to obtain the second dq flux linkage includes:

[0017] in, , , , This is the second dq magnet chain.

[0018] This invention also provides a demagnetization accounting system for permanent magnet synchronous motors, comprising the following modules: The steady-state initial condition module is used to perform steady-state calculations on the initial conditions of the motor in a synchronous rotating coordinate system based on the parameters of the motor, so as to obtain the steady-state initial conditions of the motor; wherein, the parameters of the motor include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current; The flux linkage differential module is used to calculate the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current. The flux linkage integration module is used to integrate the differential value of the first dq flux linkage to obtain the second dq flux linkage. The permanent magnet flux linkage update module is used to update the first permanent magnet flux linkage according to the first dq current and motor parameters to obtain the second permanent magnet flux linkage. The inverse calculation module is used to calculate the second dq current based on the magnetic flux linkage of the second permanent magnet and the second dq magnetic flux linkage. The demagnetization calculation module is used to determine the demagnetization calculation result when the current reaches a steady state based on the second dq current and the preset current convergence threshold.

[0019] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the demagnetization calculation method for a permanent magnet synchronous motor as described above.

[0020] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the demagnetization calculation method for permanent magnet synchronous motors as described above.

[0021] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the demagnetization calculation method for permanent magnet synchronous motors as described above.

[0022] The demagnetization calculation method for permanent magnet synchronous motors provided by this invention involves: performing steady-state calculations on the initial conditions of the motor in a synchronous rotating coordinate system based on the motor parameters to obtain the steady-state initial conditions; performing differential calculations on the first dq flux linkage based on the first dq current to obtain the first dq flux linkage differential value; performing integral calculations on the first dq flux linkage differential value to obtain the second dq flux linkage; updating the first permanent magnet flux linkage based on the first dq current and the motor parameters to obtain the second permanent magnet flux linkage; performing inverse calculations on the second permanent magnet flux linkage and the second dq flux linkage to obtain the second dq current; and determining when the current reaches a steady state based on the second dq current and a preset current convergence threshold to obtain the demagnetization calculation result. This method significantly improves the computational efficiency of demagnetization calculation for permanent magnet synchronous motors with grid-connected damping windings while maintaining a certain level of computational accuracy. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a permanent magnet synchronous motor with grid-connected damping windings.

[0025] Figure 2 This is a flowchart of the demagnetization calculation method for permanent magnet synchronous motors provided by the present invention.

[0026] Figure 3 This is a flowchart illustrating the demagnetization calculation method for permanent magnet synchronous motors provided by the present invention.

[0027] Figure 4 This is a flowchart of the permanent magnet demagnetization judgment and parameter update calculation in the permanent magnet synchronous motor demagnetization calculation method provided by the present invention.

[0028] Figure 5 This is the equivalent magnetic circuit model of the present invention.

[0029] Figure 6 This is a schematic diagram of the demagnetization calculation system for a permanent magnet synchronous motor.

[0030] Figure 7 This is a schematic diagram of the structure of the electronic device provided by the present invention.

[0031] Figure 8 This is the demagnetization curve from Example 1.

[0032] Figure 9 This is a comparison of the calculation results of the stator d-axis current in Example 1.

[0033] Figure 10 This is a comparison of the calculation results of the permanent magnet flux linkage in Example 1.

[0034] Figure label: 1-Stator; 2-Stator winding; 3-Damping winding; 4-Permanent magnet; 5-Rotor. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] The core idea of ​​this invention is to construct a mathematical model at the analytical level through spatial subdivision and nonlinear dual iteration, which can be dynamically updated and can finely characterize the demagnetization at any position inside a single magnet.

[0037] First, a steady-state electromagnetic calculation model of the motor is established based on the dq coordinate system. The stator side and damping winding side dq axis currents are obtained through Clark transformation and Park transformation. Then, the stator side and damping winding side dq axis flux linkages are solved to serve as the initial inputs for the motor transient electromagnetic calculation model and the permanent magnet magnetic circuit calculation model. Secondly, based on the transient equivalent circuit model of the permanent magnet synchronous motor in the dq coordinate system, a transient electromagnetic calculation model of the motor is established. By using the flux linkage differential calculation equation, the forward Euler integration method and the flux linkage inverse current calculation equation, the time-step solution of the current and flux linkage during the transient process of the motor is realized. Then, based on the equivalent magnetic circuit model, a permanent magnet magnetic circuit calculation model is constructed. The permanent magnet under the first pole is divided into 12 independent equivalent magnetic circuits according to the position of the stator teeth. The external demagnetizing magnetomotive force on each segment is calculated, and the local irreversible demagnetization situation is judged according to the demagnetization criterion. At the same time, the remanent magnetization and permanent magnet flux of each region are updated. Finally, the analytical calculation results were verified through two-dimensional transient finite element simulation and prototype no-load back EMF test.

[0038] The following is combined Figures 2 to 7 This invention is described.

[0039] Figure 2 This is a flowchart of the demagnetization calculation method for permanent magnet synchronous motors provided by the present invention. Figure 3 This is a flowchart illustrating the demagnetization calculation method for permanent magnet synchronous motors provided by the present invention.

[0040] like Figure 2 and Figure 3 As shown, the method includes the following: Step 101: In the synchronous rotating coordinate system, perform steady-state calculations on the initial conditions of the motor based on the motor parameters to obtain the steady-state initial conditions of the motor; wherein, the motor parameters include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current.

[0041] Step 102: Calculate the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current.

[0042] Step 103: Integrate the differential value of the first dq flux linkage to obtain the second dq flux linkage.

[0043] Step 104: Update the first permanent magnet flux linkage based on the first dq current and the parameters of the motor to obtain the second permanent magnet flux linkage.

[0044] Step 105: Based on the second permanent magnet flux linkage and the second dq flux linkage, the second dq current is calculated by inverse calculation.

[0045] Step 106: Based on the second dq current and the preset current convergence threshold, determine when the current reaches a steady state and obtain the demagnetization calculation result.

[0046] In one embodiment, step 101 establishes a mathematical model of three-phase current-dq current-magnetic flux under steady-state conditions, representing the functional relationship between the three-phase stator current of the motor at the initial moment and the dq current and magnetic flux in the synchronous rotating coordinate system, thus providing initial input conditions for transient calculation of the transient process.

[0047] Specifically, the three-phase current parameters are expressed as follows:

[0048] in, , , The stator current is in the natural coordinate system ABC. For frequency, The angular frequency of the motor. This is the initial phase angle.

[0049] In one embodiment, step 101 includes steps A1 to A3: Step A1: Based on the three-phase current parameters, calculate the stator current in the stationary coordinate system using Clark transformation; Step A2: Based on the stator current in the stationary coordinate system, calculate the first dq current in the synchronous rotating coordinate system using the Park transformation; Step A3: Calculate the first dq flux linkage based on the first permanent magnet flux linkage and the first dq current.

[0050] Specifically, in step A1, the stator current in the stationary coordinate system is calculated using the Clark transformation as follows:

[0051] in, , Let be the stator current in the stationary coordinate system α-β.

[0052] In step A2, the first dq current in the synchronous rotating coordinate system is calculated using the Park transformation:

[0053] in, , The stator current in the synchronously rotating coordinate system dq, also known as the first dq current. Let d be the electrical angle of the d-axis relative to the α-axis.

[0054] In step A3, based on the first permanent magnet flux linkage and the first dq current, the first dq flux linkage is calculated as follows:

[0055] in, , For the stator-side flux linkage in the synchronous rotating coordinate system dq, , The damping winding side flux in the synchronous rotating coordinate system dq. , , , Collectively referred to as the first dq magnet chain; , For synchronous inductance in synchronous rotating coordinate system dq; , The excitation inductance is in the synchronous rotating coordinate system dq; It is a permanent magnet flux linkage.

[0056] In one embodiment, step 102, calculating the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current, includes:

[0057] in, , For the stator side voltage in the synchronous rotating coordinate system, For stator resistance, , , , For the first dq current, The angular frequency of the motor. , , , For the first dq magnet link, , This refers to the resistance of the damping winding in the synchronous rotating coordinate system.

[0058] In one embodiment, step 103, which involves integrating the differential value of the first dq flux linkage to obtain the second dq flux linkage, includes:

[0059] in, , , , This is the second dq magnet chain.

[0060] Figure 4 This is a flowchart of the permanent magnet demagnetization judgment and parameter update calculation in the permanent magnet synchronous motor demagnetization calculation method provided by the present invention.

[0061] In order to describe the local demagnetization of non-uniform, small regions inside a single permanent magnet, the method proposed in this invention differs from the traditional magnetic equivalent circuit that treats the permanent magnet as a whole. Instead, the permanent magnet is subdivided into multiple small segments along the magnetization direction, and each segment is assigned an independent remanent magnetization. When irreversible demagnetization occurs in a certain segment, the remanent magnetization of that segment of the permanent magnet is updated and reduced accordingly.

[0062] This method breaks through the limitation of the traditional magnetic equivalent circuit method, which can only calculate the average degree of demagnetization of permanent magnets, and can effectively identify the local demagnetization differences at different spatial locations of permanent magnets.

[0063] In step 104 of the method of this invention, the stator side of the motor is divided into several parts according to the stator tooth position, and the demagnetizing magnetomotive force is evenly distributed in each part. Similarly, the permanent magnet is divided into equal parts, that is, the motor magnetic circuit is simplified into several independently distributed magnetic circuit segments. Each magnetic circuit segment is calculated and determined separately to determine whether the permanent magnet has undergone irreversible demagnetization. See [link to relevant documentation]. Figure 5 , is the equivalent magnetic circuit model.

[0064] like Figure 4As shown, in one embodiment, step 104 includes steps B1 to B9: Step B1: Calculate the magnetomotive force and magnetic reluctance within the permanent magnet based on its parameters. Step B2: Calculate the demagnetizing magnetomotive force amplitude based on the motor parameters and the first dq current; Step B3: Calculate the external magnetic reluctance of the motor's magnetic circuit based on the motor's parameters; Step B4: Calculate the magnetic flux of the permanent magnet based on the magnetomotive force inside the permanent magnet, the magnetic reluctance inside the permanent magnet, the amplitude of the demagnetizing magnetomotive force, and the external magnetic reluctance of the motor magnetic circuit. Step B5: Calculate the magnetic flux density of the permanent magnet based on the magnetic flux and area of ​​the permanent magnet; Step B6: Based on the magnetic flux density of the permanent magnet, determine when irreversible demagnetization of the permanent magnet occurs by using the demagnetization loop, and update the remanent magnetic flux density of the permanent magnet to obtain the updated remanent magnetic flux density of the permanent magnet. Step B7: Calculate the updated magnetomotive force within the permanent magnet based on the remanent magnetization of the permanent magnet. Step B8: Update the magnetic flux of the permanent magnet according to the magnetomotive force in the permanent magnet to obtain the updated magnetic flux of the permanent magnet. Step B9: Calculate the second permanent magnet flux based on the updated permanent magnet flux.

[0065] Specifically, in step B1, based on the parameters of the permanent magnet, the magnetomotive force and magnetic reluctance within the permanent magnet are calculated as follows:

[0066] in, This refers to the magnetic potential within the permanent magnet. The remanence density of a permanent magnet. The thickness of the permanent magnet along the magnetization direction. The permeability of free space, The relative permeability of a permanent magnet. The magnetic reluctance within the permanent magnet is [missing information]. The area is the permanent magnet.

[0067] In step B2, based on the motor parameters and the first dq current, the demagnetizing magnetomotive force amplitude is calculated as follows:

[0068]

[0069] in, The magnitude of the demagnetizing magnetomotive force in the synchronously rotating coordinate system dq. The stator spatial position angle, The no-load leakage flux coefficient is This represents the effective number of series turns per pole per phase.

[0070] In addition, there are:

[0071] in, The number of stator slots Number of conductors per slot This represents the number of phases of the motor. This represents the number of pole pairs of the motor. This represents the number of parallel branches of the stator winding.

[0072] In step B3, based on the motor parameters, the external magnetic reluctance of the motor magnetic circuit is calculated as follows:

[0073] in, The external magnetic reluctance of the motor's magnetic circuit. The length of the air gap. The magnetic circuit saturation coefficient is... The air gap coefficient, To calculate the polar arc coefficient, For polar distance, Calculate the length of the iron core.

[0074] in:

[0075] in, The diameter is the armature diameter.

[0076] In step B4, based on the magnetomotive force within the permanent magnet, the magnetic reluctance within the permanent magnet, the amplitude of the demagnetizing magnetomotive force, and the external magnetic reluctance of the motor magnetic circuit, the magnetic flux of the permanent magnet is calculated as follows:

[0077] in, The magnetic flux provided by the permanent magnet in the i-th magnetic path to the external magnetic path. Let be the demagnetizing magnetomotive force under the i-th magnetic circuit.

[0078] In step B5, based on the permanent magnet flux and the permanent magnet area, the magnetic flux density of the permanent magnet is calculated as follows:

[0079] in, Let be the magnetic flux density of the permanent magnet in the i-th magnetic path.

[0080] In step B6, based on the magnetic flux density of the permanent magnet, and by using the demagnetization loop, when it is determined that irreversible demagnetization of the permanent magnet has occurred, the remanent magnetic flux density of the permanent magnet is updated, resulting in the updated remanent magnetic flux density of the permanent magnet:

[0081] in, This refers to the remanence density of the updated permanent magnet. Let be the magnetic field strength corresponding to the magnetic flux density of the permanent magnet in the demagnetization loop under the i-th magnetic circuit.

[0082] In step B7, the updated magnetomotive force within the permanent magnet is calculated based on the updated remanent magnetization:

[0083] in, This represents the updated magnetic potential within the permanent magnet.

[0084] In step B8, the magnetic flux of the permanent magnet is updated based on the remaining internal magnetomotive force of the permanent magnet, and the updated magnetic flux of the permanent magnet is obtained using the following formula:

[0085] When calculating the updated permanent magnet flux, the updated magnetomotive force within the permanent magnet is used. Substitution .

[0086] In step B9, based on the updated permanent magnet flux, the second permanent magnet flux linkage is calculated as follows:

[0087] in, The effective number of series turns per phase, To determine the number of independently distributed magnetic circuits of the permanent magnet based on the stator tooth positions on the lower stator side of the motor, according to the position of the stator teeth. The value is generally determined based on the stator tooth groove structure.

[0088] In one embodiment, in step 105, the second dq current is calculated by inverse calculation based on the second permanent magnet flux linkage and the second dq flux linkage. The method is as follows:

[0089] in, The stator-side d-axis flux linkage, excluding permanent magnet flux linkage, is defined in the synchronous rotating coordinate system dq. For the damping winding side d-axis flux linkage in the synchronous rotating coordinate system dq, excluding permanent magnet flux linkage. , To calculate the inductance parameters in the synchronously rotating coordinate system dq, , The damping winding inductance is in the synchronous rotating coordinate system dq.

[0090] In one embodiment, in step 106, the method for determining whether the current has reached a steady state based on the second dq current and a preset current convergence threshold is as follows:

[0091] in, To calculate the number of steps in the iteration, The preset current convergence threshold is used to achieve steady state when the above conditions are met.

[0092] In summary, since irreversible demagnetization is often intertwined with strong reverse magnetic fields and material nonlinearity, the model of this invention designs two nested iterative loops: Inner loop iteration (handling strong reverse magnetic field): Based on the flux linkage calculated in the dq coordinate system in the current step, the flux linkage inverse solution current is performed based on the voltage equation and flux linkage equation of the permanent magnet synchronous motor with grid-connected damping winding under transient conditions. The demagnetizing current is continuously updated iteratively until the current converges.

[0093] Outer loop iteration (handling irreversible demagnetization evolution): After the inner loop solves for the demagnetizing current, the outer loop program calculates the actual operating point of each small segment of the permanent magnet under each specific demagnetizing current. When the operating point of a certain segment crosses the demagnetization inflection point of the permanent magnet material, the remanence density of that segment of the permanent magnet is permanently updated according to the demagnetization loop, and the magnetic flux of the permanent magnet calculated after the update is used as the new input for the next inner loop iteration.

[0094] Thanks to the dynamic update of the outer remanent magnetization density, the method proposed in this invention has a certain demagnetization state feedback update mechanism, which can describe the coupling process of fault condition impact current-strong demagnetization magnetomotive force-local irreversible demagnetization-permanent magnet parameter change-evolution of electromagnetic state, rather than just performing a one-time performance evaluation after demagnetization after the calculation.

[0095] This invention provides a demagnetization calculation method for a permanent magnet synchronous motor. The method involves performing steady-state calculations on the initial conditions of the motor in a synchronous rotating coordinate system based on the motor parameters to obtain the steady-state initial conditions. Then, based on the first dq flux linkage and the first dq current, the method performs differential calculations on the first dq flux linkage to obtain a first dq flux linkage differential value. Finally, the method integrates the first dq flux linkage differential value to obtain a second dq flux linkage. Based on the first dq current and the motor parameters, the method updates the first permanent magnet flux linkage to obtain a second permanent magnet flux linkage. Based on the second permanent magnet flux linkage and the second dq flux linkage, the method performs inverse calculations to obtain the second dq current. Finally, based on the second dq current and a preset current convergence threshold, the method determines when the current reaches a steady state, thus obtaining the demagnetization calculation result. This method significantly improves the computational efficiency of demagnetization calculations for permanent magnet synchronous motors with grid-connected damping windings while maintaining a certain level of computational accuracy.

[0096] Compared with traditional demagnetization calculation methods, this invention not only considers the demagnetization effect of the stator-side dq-axis current on the permanent magnet, but also takes into account the dq-axis current on the damping winding side, which can more realistically describe the demagnetizing magnetomotive force generated by the stator winding and damping winding together during the transient process of a permanent magnet synchronous motor with grid-connected damping system.

[0097] Meanwhile, this invention divides the permanent magnet under one pole into multiple independent magnetic circuit units according to spatial position, and calculates the demagnetizing magnetomotive force, operating point and remanent magnetization changes in each region. This breaks through the limitation of the traditional magnetic equivalent circuit method, which can only calculate the average degree of demagnetization of the permanent magnet, and can accurately identify the local demagnetization differences at different locations inside the permanent magnet.

[0098] This invention establishes an analytical relationship between motor operating parameters, structural parameters, and demagnetization criteria, which is beneficial for preliminary motor design, parameter adjustment, and optimization of demagnetization resistance. This invention is applicable to demagnetization calculations of permanent magnet synchronous motors with grid-connected damping systems and general permanent magnet synchronous motors under fault conditions such as grid disturbances, short circuits, and transient impacts. It can achieve rapid assessment of local demagnetization risks while ensuring high computational efficiency, providing an effective means for motor safety operation evaluation, fault analysis, and design verification.

[0099] The demagnetization calculation system for permanent magnet synchronous motors provided by this invention is described below. The demagnetization calculation system for permanent magnet synchronous motors described below can be referred to in correspondence with the demagnetization calculation method for permanent magnet synchronous motors described above.

[0100] Figure 6 This is a schematic diagram of the demagnetization calculation system for permanent magnet synchronous motors provided by the present invention, as shown below. Figure 6 As shown, the system includes the following: The steady-state initial condition module 201 is used to perform steady-state calculations on the initial conditions of the motor in a synchronous rotating coordinate system based on the parameters of the motor, so as to obtain the steady-state initial conditions of the motor; wherein, the parameters of the motor include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current; The flux linkage differential module 202 is used to calculate the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current. The flux linkage integration module 203 is used to integrate the differential value of the first dq flux linkage to obtain the second dq flux linkage. The permanent magnet flux linkage update module 204 is used to update the first permanent magnet flux linkage according to the first dq current and motor parameters to obtain the second permanent magnet flux linkage. The inverse calculation module 205 is used to calculate the second dq current based on the magnetic flux of the second permanent magnet and the second dq magnetic flux. The demagnetization calculation module 206 is used to determine the demagnetization calculation result when the current reaches a steady state based on the second dq current and the preset current convergence threshold.

[0101] This invention provides a demagnetization calculation system for permanent magnet synchronous motors. The system performs steady-state calculations on the initial conditions of the motor in a synchronous rotating coordinate system based on the motor parameters to obtain the steady-state initial conditions. It then performs differential calculations on the first dq flux linkage based on the first dq current to obtain a first dq flux linkage differential value. Next, it integrates this differential value to obtain a second dq flux linkage. Finally, it updates the first permanent magnet flux linkage based on the first dq current and the motor parameters to obtain a second permanent magnet flux linkage. Based on the second permanent magnet flux linkage and the second dq flux linkage, it performs inverse calculations to obtain the second dq current. Finally, based on the second dq current and a preset current convergence threshold, it determines when the current reaches a steady state and obtains the demagnetization calculation result. This significantly improves the computational efficiency of demagnetization calculations for permanent magnet synchronous motors with grid-connected damping windings while maintaining a certain level of computational accuracy.

[0102] Figure 7 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 7 As shown, the electronic device may include: a processor 810, a communication interface 820, a memory 830, and a communication bus 840, wherein the processor 810, the communication interface 820, and the memory 830 communicate with each other through the communication bus 840. The processor 810 can call logical instructions in the memory 830 to execute a demagnetization calculation method for a permanent magnet synchronous motor, including: In a synchronous rotating coordinate system, steady-state calculations are performed on the initial conditions of the motor based on the motor parameters to obtain the steady-state initial conditions of the motor; wherein, the motor parameters include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current; The differential value of the first dq flux linkage is calculated based on the first dq flux linkage and the first dq current. The second dq flux linkage is obtained by integrating the differential value of the first dq flux linkage. Based on the first dq current and the parameters of the motor, the first permanent magnet flux linkage is updated to obtain the second permanent magnet flux linkage; The second dq current is obtained by inverse calculation based on the second permanent magnet flux linkage and the second dq flux linkage. Based on the second dq current and the preset current convergence threshold, the demagnetization calculation result is obtained when the current reaches a steady state.

[0103] Furthermore, the logical instructions in the aforementioned memory 830 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0104] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the permanent magnet synchronous motor demagnetization calculation method provided by the above methods.

[0105] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to perform the permanent magnet synchronous motor demagnetization calculation method provided by the above methods.

[0106] The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0107] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0108] Example 1

[0109] This embodiment uses a 72-slot, 6-pole PMSM with grid-connected damping winding for research. The main structural parameters and rated parameters of the motor are shown in Table 1.

[0110] Table 1:

[0111] Based on the parameters in the table, a two-dimensional simulation model of the motor was established in the finite element simulation software. The model includes the main structures such as the stator core, stator windings, air gap, permanent magnets, rotor core, and damping windings. It can be used to simulate and analyze the internal magnetic field distribution and the variation law of key electromagnetic quantities during the transient process of the motor. The permanent magnet material of the motor is NdFeB50. According to the BH scatter data in the finite element software material library, PCHIP smooth interpolation fitting was used to obtain the following results: Figure 8 The NdFeB50 demagnetization curve shown was simulated at a temperature of 70℃. The effect of temperature changes on the permanent magnet demagnetization curve was not considered during the simulation; therefore, the demagnetization inflection point of the permanent magnet material used at this temperature is... When the operating point of the permanent magnet in a certain region is lower than the above-mentioned critical point, it is considered that irreversible demagnetization has occurred in that region.

[0112] In this embodiment, a three-phase short circuit is selected as a typical demagnetization condition. After the three-phase short circuit occurs, the stator winding terminal voltage drops rapidly, and a transient short-circuit current with a large amplitude will be generated in the winding. This forms a strong armature reaction magnetic field in the demagnetization direction, causing the permanent magnet operating point to move to the vicinity of the demagnetization curve inflection point or even below the inflection point, resulting in irreversible demagnetization of the permanent magnet.

[0113] In this embodiment, the current convergence threshold is set to 0.5%, and the analytical calculation results span over 150 cycles. To ensure the clarity of the analysis process and the readability of the results, this embodiment selects the first 30 cycles as the typical analysis interval, focusing on the response characteristics and variation patterns within this stage. During this interval, the motor tends to reach a steady state, reflecting the main variation patterns of the motor's transient response; therefore, it can serve as a representative interval for subsequent results discussion.

[0114] Figure 9 The results of the stator d-axis current calculation are compared, where the analytical results are obtained using the present invention, and the finite element results are obtained using the finite element analysis method.

[0115] Figure 10 The results of the calculation of permanent magnet flux linkage are compared, where the analytical results are obtained using the present invention, and the finite element results are obtained using the finite element analysis method.

[0116] Table 2 shows a comparison of the results of the method of the present invention and the finite element analysis method.

[0117] Table 2:

[0118] The results show that the method of the present invention can significantly improve the calculation efficiency while ensuring high calculation accuracy, and provides a theoretical basis for the anti-demagnetization design of PMSM with grid-connected damping winding.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the demagnetization of a permanent magnet synchronous motor, characterized in that, include: In a synchronous rotating coordinate system, steady-state calculations are performed on the initial conditions of the motor based on the motor parameters to obtain the steady-state initial conditions of the motor; wherein, the motor parameters include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current; The differential value of the first dq flux linkage is calculated based on the first dq flux linkage and the first dq current. The second dq flux linkage is obtained by integrating the differential value of the first dq flux linkage. Based on the first dq current and the parameters of the motor, the first permanent magnet flux linkage is updated to obtain the second permanent magnet flux linkage; The second dq current is obtained by inverse calculation based on the second permanent magnet flux linkage and the second dq flux linkage. Based on the second dq current and the preset current convergence threshold, the demagnetization calculation result is obtained when the current reaches a steady state.

2. The method for calculating the demagnetization of a permanent magnet synchronous motor according to claim 1, characterized in that, Also includes: Based on the second dq current and the preset current convergence threshold, if it is determined that the current has not reached a steady state, the second dq current is assigned to the first dq current, the second dq flux is assigned to the first dq flux, and the second dq current is recalculated by inverse solving.

3. The method for calculating the demagnetization of a permanent magnet synchronous motor according to claim 1, characterized in that, The step of performing steady-state calculations on the initial conditions of the motor based on its parameters to obtain the steady-state initial conditions of the motor includes: Based on the three-phase current parameters, the stator current in the stationary coordinate system is calculated using Clark transformation; Based on the stator current in the stationary coordinate system, the first dq current in the synchronous rotating coordinate system is calculated using the Park transformation. The first dq flux linkage is calculated based on the first permanent magnet flux linkage and the first dq current.

4. The method for calculating the demagnetization of a permanent magnet synchronous motor according to claim 1, characterized in that, The step of updating the first permanent magnet flux linkage based on the first dq current and motor parameters to obtain the second permanent magnet flux linkage includes: Based on the parameters of the permanent magnet, the magnetomotive force and magnetic reluctance within the permanent magnet are calculated. The demagnetizing magnetomotive force amplitude is calculated based on the motor parameters and the first dq current. Based on the motor parameters, the external magnetic reluctance of the motor's magnetic circuit is calculated; The magnetic flux of the permanent magnet is calculated based on the magnetomotive force, magnetic reluctance, demagnetization magnetomotive force amplitude, and external magnetic reluctance of the motor magnetic circuit. The magnetic flux density of the permanent magnet is calculated based on the magnetic flux and area of ​​the permanent magnet. Based on the magnetic flux density of the permanent magnet, and by using the demagnetization loop to determine when irreversible demagnetization of the permanent magnet occurs, the remanent magnetic flux density of the permanent magnet is updated to obtain the updated remanent magnetic flux density of the permanent magnet. The updated magnetomotive force within the permanent magnet is calculated based on the remanent magnetization of the permanent magnet. The magnetic flux of the permanent magnet is updated based on the magnetic potential within the permanent magnet to obtain the updated magnetic flux of the permanent magnet. The second permanent magnet flux is calculated based on the updated permanent magnet flux.

5. The method for calculating the demagnetization of a permanent magnet synchronous motor according to claim 1, characterized in that, The step of calculating the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current includes: in, , For the stator side voltage in the synchronous rotating coordinate system, For stator resistance, , , , For the first dq current, The angular frequency of the motor. , , , For the first dq magnet link, , This refers to the resistance of the damping winding in the synchronous rotating coordinate system.

6. The method for calculating the demagnetization of a permanent magnet synchronous motor according to claim 5, characterized in that, The step of integrating the differential value of the first dq flux linkage to obtain the second dq flux linkage includes: in, , , , This is the second dq magnet chain.

7. A demagnetization accounting system for a permanent magnet synchronous motor, characterized in that, include: The steady-state initial condition module is used to perform steady-state calculations on the initial conditions of the motor in a synchronous rotating coordinate system based on the parameters of the motor, so as to obtain the steady-state initial conditions of the motor; wherein, the parameters of the motor include three-phase current parameters and the first permanent magnet flux linkage, and the steady-state initial conditions include the first dq flux linkage and the first dq current; The flux linkage differential module is used to calculate the differential value of the first dq flux linkage based on the first dq flux linkage and the first dq current. The flux linkage integration module is used to integrate the differential value of the first dq flux linkage to obtain the second dq flux linkage. The permanent magnet flux linkage update module is used to update the first permanent magnet flux linkage according to the first dq current and motor parameters to obtain the second permanent magnet flux linkage. The inverse calculation module is used to calculate the second dq current based on the magnetic flux linkage of the second permanent magnet and the second dq magnetic flux linkage. The demagnetization calculation module is used to determine the demagnetization calculation result when the current reaches a steady state based on the second dq current and the preset current convergence threshold.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the demagnetization calculation method for permanent magnet synchronous motors as described in any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the demagnetization calculation method for permanent magnet synchronous motors as described in any one of claims 1 to 6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the demagnetization calculation method for permanent magnet synchronous motors as described in any one of claims 1 to 6.

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