Electromagnetic-thermal dynamic coupling modeling method for permanent magnet synchronous motor based on equivalent magnetic network

Abstract

The invention discloses a method for modeling the electromagnetic thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network, which belongs to the technical field of motor simulation modeling. The method comprises obtaining the material properties and topological structure of the permanent magnet synchronous motor; obtaining the electromagnetic model of the motor according to the material properties and topological structure of the permanent magnet synchronous motor; equivalentizing the internal temperature field of the motor to a plurality of thermal resistance units according to the material properties and topological structure of the permanent magnet synchronous motor, and obtaining the equivalent thermal resistance structure of the motor; obtaining the motor loss based on the electromagnetic model of the motor, and updating the core magnetic permeability of the electromagnetic model of the motor according to the motor loss using the equivalent thermal resistance structure of the motor, realizing bidirectional coupling, and completing the electromagnetic thermal dynamic coupling modeling of the permanent magnet synchronous motor. The invention bidirectionally couples the motor equivalent magnetic circuit model and the motor thermal network model, and can continuously solve the electromagnetic thermal coupling of the motor through iterative updating of the magnetic permeability and magnetic flux with temperature, and realizes the real-time interaction between the electromagnetic parameters of the motor and the motor temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor simulation modeling, and in particular relates to an electromagnetic-thermal dynamic coupling modeling method for a permanent magnet synchronous motor based on an equivalent magnetic network. Background Art

[0002] As a complex system with multiple physical fields coupled, the permanent magnet synchronous motor will change its response characteristics during actual operation due to the temperature rise, magnetic circuit saturation, cross coupling, and electromagnetic field harmonics of the motor. For example, changes in motor temperature will mainly affect the stator resistance and the size of the alternating magnetic flux, changes in the magnetic permeability of ferromagnetic materials will cause nonlinear changes in the motor inductance and flux linkage, and electromagnetic field harmonics will affect the output characteristics of the electromagnetic torque. These nonlinear parameter couplings and motor electromagnetic thermal coupling will make the motor response characteristics more complex, so high-precision dynamic electromagnetic thermal coupling motor simulation models are extremely important in high-performance motor development and performance optimization.

[0003] At present, many scholars have carried out a lot of research on the modeling and characteristics of electromagnetic thermal coupling of permanent magnet synchronous motors. The main method is to establish the flux model, resistance model, and dq axis inductance model of the dq axis flux with respect to the dq axis current and rotor position angle to obtain the nonlinear electromagnetic model of the permanent magnet synchronous motor. The motor thermal model is based on the heat transfer principle and the thermal network method to establish the motor thermal network model. Using the motor loss as the heat source, the forward conduction relationship between the electromagnetic model and the motor thermal model is established. Among them, in the nonlinear electromagnetic model of the permanent magnet synchronous motor, the flux model, dq axis inductance model, and resistance model of the dq axis flux with respect to the dq axis current and rotor position angle are calculated by the nonlinear interpolation method through the lookup model of the relationship with the motor temperature.

[0004] The flux model of the dq axis flux with respect to the dq axis current and the rotor position angle is expressed in the following form:

[0005]

[0006] Among them, ψ d is the d-axis magnetic flux, ψ q is the q-axis magnetic flux, ψ d ,ψ q The value depends on the dq axis current value, the rotor position angle θ e and the motor temperature, A d , B d , A q , B q is the coefficient matrix, C(θ e )、S(θ e ) is shown in the following formula:

[0007]

[0008] Based on the quantitative calculation of the influence of the motor temperature rise characteristics on the motor electromagnetic characteristics, the relationship between the motor temperature rise and the dq axis current is obtained, which is expressed in the following form:

[0009]

[0010] Among them, i dT ,i qT is the temperature compensation current.

[0011] The dq-axis inductance model also adopts the same table lookup model as the dq-axis flux linkage, which is expressed as follows:

[0012]

[0013] Among them, L d ,L q are the dq axis inductance, C d , D d , C q , D q is the coefficient matrix, E(θ e )、R(θ e ) is shown in the following formula:

[0014]

[0015] The calculation model of motor resistance and motor temperature is expressed as:

[0016]

[0017] Among them, k se is the skin effect coefficient, a is the conductor height, h is the penetration depth, and m is the mth conductor. n is the slot width, σ cu The conductivity of copper, b is the wire width, and μ0 is the vacuum magnetic permeability. According to the relationship between motor resistance and temperature, a one-dimensional lookup table model of phase resistance is established, and the motor temperature is used as input to query the current state motor resistance value.

[0018] The node temperature calculated by the motor thermal network model is used as input, and the reverse conduction relationship is established through current, resistance, flux linkage, and inductance. The model is discretized to finally establish the electromagnetic-thermal coupling model of the permanent magnet synchronous motor.

[0019] Disadvantages of existing technology:

[0020] ① Low efficiency. Important electromagnetic parameters of the motor, such as inductance, flux linkage, resistance, etc., need to be calculated one by one by the finite element model according to different current conditions and temperatures at different times. Since the temperature and electromagnetic parameters of the motor at different times and conditions are very complex, the amount of calculation is large and the modeling efficiency is low.

[0021] ② Low accuracy and large error. The nonlinear model of the permanent magnet synchronous motor calculated by interpolation table ignores the change of core magnetic permeability and electromagnetic field flux with temperature. Therefore, the calculation accuracy of the electromagnetic thermal coupling of the motor is low, which will produce a large deviation from the actual data of the motor.

[0022] ③ Simplified model solution. The inductance, flux, resistance and other parameters of the motor at different temperatures are all obtained based on the finite element calculation results. However, the data obtained by the finite element calculation is not a continuous temperature change, which will lead to a simplification when solving the electromagnetic thermal coupling characteristics of the motor, that is, only the temperature coupling characteristic data of different single nodes can be obtained. Summary of the invention

[0023] In view of the above-mentioned deficiencies in the prior art, the present invention provides a permanent magnet synchronous motor electromagnetic-thermal dynamic coupling modeling method based on an equivalent magnetic network, which bidirectionally couples the motor equivalent magnetic circuit model and the motor thermal network model. By iteratively updating the magnetic permeability and magnetic flux with temperature, the motor electromagnetic-thermal coupling can be continuously solved to realize real-time interaction between the motor electromagnetic parameters and the motor temperature.

[0024] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a permanent magnet synchronous motor electromagnetic thermal dynamic coupling modeling method based on an equivalent magnetic network, comprising the following steps:

[0025] S1. Obtain the material properties and topological structure of the permanent magnet synchronous motor;

[0026] S2. According to the material characteristics and topological structure of the permanent magnet synchronous motor, an equivalent magnetic network model is performed to obtain an electromagnetic model of the motor;

[0027] S3. According to the material properties and topological structure of the permanent magnet synchronous motor, the internal temperature field of the motor is equivalent to multiple thermal resistance units to obtain an equivalent thermal resistance structure of the motor;

[0028] S4. The motor loss is obtained based on the motor electromagnetic model, and according to the motor loss, the core magnetic permeability of the motor electromagnetic model is updated using the motor equivalent thermal resistance structure to achieve bidirectional coupling and complete the permanent magnet synchronous motor electromagnetic thermal dynamic coupling modeling.

[0029] Furthermore, the motor equivalent thermal resistance structure in step S3 is bilaterally symmetrical along the central axis; the central axis includes the casing and the medium convection thermal resistance R connected in sequence. med-housing 、Case thermal resistance R housing , Contact thermal resistance between housing and stator yoke R housing-yoke , stator yoke thermal resistance R yoke , stator tooth conduction thermal resistance R st , air gap convection thermal resistance R airgap , External rotor core conduction thermal resistance R rotor-iron1, conducted by the internal rotor core thermal resistance R rotor-iron2 and the convection thermal resistance R of the rotor core internal ventilation opening rotor-aircool The parallel group and the contact thermal resistance R between the rotor core and the shaft rotor-shf One side of the central axis includes convection thermal resistance R between the end cover, the housing and the medium med-housing The other end is connected to the external air convection thermal resistance R cap-air and bearing thermal resistance R bear , respectively with the external air convection thermal resistance R cap-air The other end of the winding is connected to the internal air convection thermal resistance R end-air , rotor core and internal air convection thermal resistance R rotor-air and permanent magnet axial conduction thermal resistance R pm-ax , and the convection thermal resistance R between the end winding and the internal air end-air The other end of the winding is connected to the end axial conduction thermal resistance R coil-end , and the axial conduction thermal resistance R between the winding and the end coil-end The other end of the core is connected to the winding contact thermal resistance R iron-coil , and the convection thermal resistance R between the rotor core and the internal air rotor-air The other end of the permanent magnet is connected to the axial conduction thermal resistance R rotor-ax , and the permanent magnet axial conduction thermal resistance R pm-ax The other end of the rotor core connected to the permanent magnet has a thermal resistance R rotor-pm and the bearing thermal resistance R bear The other end is connected to the shaft axial conduction thermal resistance R shf The core and winding contact thermal resistance R iron-coil The other end of the stator is connected to the stator tooth by a thermal conduction resistance R st The axial conduction thermal resistance R of the permanent magnet core rotor-ax The other end and the rotor core and permanent magnet contact thermal resistance R rotor-pm The other end is respectively connected to the external rotor core thermal resistance R rotor-iron1 And the thermal resistance R rotor-iron2 and the convection thermal resistance R of the rotor core internal ventilation opening rotor-aircool The parallel group is connected; the axial thermal conduction resistance R shf The other end of the rotor core and the shaft contact thermal resistance R rotor-shf The other end of the connection.

[0030] Furthermore, the step S4 is specifically as follows:

[0031] S401, obtaining electromagnetic parameters of different current working points under different rotor position angles according to the electromagnetic model of the motor, and performing position detection using the electromagnetic parameters of different current working points under different rotor position angles to obtain a mechanical angle;

[0032] S402, according to the motor electromagnetic model, obtain the d-axis voltage U d , stator voltage amplitude V m and three-phase current vector, and transform the three-phase current vector coordinates according to the mechanical angle to obtain the d-axis current i d and q-axis current i q ;

[0033] S403, according to the d-axis current i d , q-axis current i q , d-axis voltage amplitude V d and stator voltage amplitude V m , calculate the equivalent current of motor loss and iron loss;

[0034] S404, using the motor loss as a heat source input to the motor equivalent thermal resistance structure to obtain the node temperature of each motor component;

[0035] S405. According to the node temperatures of each motor component and the iron loss equivalent current, the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model are updated to achieve bidirectional coupling and complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

[0036] Furthermore, the motor loss in step S403 includes motor winding copper loss, core loss and mechanical loss:

[0037] P Cu =3I 2 R

[0038] P Fe =P Fe-oc +P Fe-sc

[0039]

[0040]

[0041] P m =k m n+k ω n 3

[0042] Among them, P Cu is the motor winding copper loss; I is the current value; R is the current temperature resistance value; P Fe is the core loss; P Fe-oc P is the core loss when the motor is unloaded; Fe-sc is the core loss when the motor is short-circuited; a h V is the hysteresis loss coefficient of the motor when the motor is unloaded; m is the stator voltage amplitude; ψ fis the permanent magnet flux; a e is the eddy current loss coefficient of the motor when the motor is unloaded; a x b is the additional loss coefficient of the motor when the motor is unloaded; h V is the motor hysteresis loss coefficient when the motor is short-circuited; d is the d-axis voltage amplitude; b e b is the eddy current loss coefficient of the motor when the motor is short-circuited; x is the additional loss coefficient of the motor when the motor is short-circuited; ω e is the motor electrical speed; d is the d-axis magnetic flux; ψ q is the q-axis magnetic flux; P m is the mechanical loss; k m is the friction coefficient; k ω is the drag coefficient; n is the motor speed.

[0043] Furthermore, the expression of the iron loss equivalent current in step S403 is:

[0044]

[0045] Among them, i dFe is the d-axis iron loss equivalent current; i qFe is the q-axis iron loss equivalent current; P Fe is the core loss; ω e is the motor electrical speed; d is the d-axis magnetic flux; ψ q is the q-axis magnetic flux.

[0046] Furthermore, the expression of the node temperature of each component of the motor in step S404 is:

[0047]

[0048] C x =ρ x V x C p,x

[0049] Among them, θ x is the temperature of node x; d is the differential sign; t is the time; C x is the component heat capacity at node x; R x,y is the thermal resistance between node x and node y; θ y is the temperature of node y; P x is the motor loss; x V is the material density of the component at node x; x is the material volume of the component at node x; C p,x is the specific heat capacity of the component material at node x.

[0050] Furthermore, the step S405 is specifically as follows:

[0051] S4051. According to the node temperatures of each motor component, the thermal network state space equation is obtained:

[0052]

[0053]

[0054]

[0055]

[0056]

[0057] D=0

[0058] in, is the first-order derivative of the nodal temperature of each component of the motor with respect to time; t is time; A is the coefficient matrix of the thermal resistance and thermal capacity of the motor; θ(t) is the nodal temperature of each component of the motor; B is the coefficient matrix of the nodal thermal capacity of each component of the motor; p(t) is the motor loss at time t; y(t) is the algebra of the equation; C and D are both coefficient matrices; is the first derivative of the n'th row node temperature with respect to time; c n' is the heat capacity of the n'th row node; R 1,n' is the thermal resistance of the node in row 1 and column n'; R n',i is the thermal resistance of the node at the n'th row and the i-th column; i is the column number of the node matrix; n' is the row number of the node matrix;

[0059] S4052. Obtain the node temperature of each component under real-time working conditions according to the thermal network state space equation;

[0060] S4053. According to the node temperature of each component and the iron loss equivalent current under real-time working conditions, the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model are updated to achieve bidirectional coupling and complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

[0061] Furthermore, the step S4053 is specifically as follows:

[0062] S40531, set the target mechanical speed ω m ';

[0063] S40532: According to the mechanical rotation angle, the speed and position are fed back to obtain the actual mechanical speed ω m ;

[0064] S40533, according to the target mechanical speed ω m ' and actual mechanical speed ω m, perform PI control and obtain the three-phase current synthesis vector;

[0065] S40534, performing MTPA maximum torque current ratio control on the three-phase current synthesis vector to obtain a given d-axis current and a given q-axis current respectively;

[0066] S40535, according to the given d-axis current and d-axis current i d , get the d-axis current difference;

[0067] S40536, according to the given q-axis current and q-axis current i q , get the q-axis current difference;

[0068] S40537, performing PI control according to the d-axis current difference and the q-axis current difference, respectively, to obtain a d-axis voltage given value and a q-axis voltage given value;

[0069] S40538. Calculate the temperature compensation current based on the iron loss equivalent current and the node temperature of each component under real-time working conditions:

[0070] S40539, obtaining the d-axis voltage at the next moment and the q-axis voltage at the next moment respectively according to the d-axis voltage given value, the q-axis voltage given value and the temperature compensation current;

[0071] S405310, according to the d-axis voltage at the next moment and the q-axis voltage at the next moment, after Park transformation, obtain the α-β axis voltage command U αβ ;

[0072] S405311, according to the α-β axis voltage command U αβ , using the vector pulse width modulation algorithm SVPWM, the pulse signal controlled at the current moment is obtained;

[0073] S405312. According to the node temperature of each component under real-time working conditions, query the magnetization curves at different temperatures, and update the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model;

[0074] S405313. Using the motor electromagnetic model updated in S404312, based on the pulse signal operation controlled at the current moment, bidirectional coupling is achieved to complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

[0075] Furthermore, the step S40538 is specifically as follows:

[0076] S405381. Calculate the dq axis current at the current temperature according to the node temperature of each component under real-time working conditions:

[0077]

[0078] Among them, idT is the d-axis current at the current temperature; i qT is the q-axis current at the current temperature; T is the node temperature of each component of the motor; T0 is the initial temperature of the motor; i d (ψ d ,ψ q ,θ e ) is the inverse mapping function of d-axis flux and current; i q (ψ d ,ψ q ,θ e ) is the inverse mapping function of the q-axis flux and current; Δ is the sign of the change; θ e is the electrical angle;

[0079] S405382. Superimpose the dq axis current and the iron loss equivalent current at the current temperature to obtain the temperature compensation current.

[0080] Furthermore, the step S40539 is specifically as follows:

[0081] S405391. Calculate the stator winding resistance at the current temperature:

[0082] R=R0[1+α(T-T0)]

[0083] Where R is the stator winding resistance at the current temperature; R0 is the resistance value at the initial temperature; α is the resistance temperature coefficient;

[0084] S405392, obtaining a temperature compensation voltage according to the temperature compensation current and the stator winding resistance at the current temperature;

[0085] S405393. According to the temperature compensation voltage, the q-axis voltage given value and the d-axis voltage given value, the d-axis voltage at the next moment and the q-axis voltage at the next moment are obtained respectively.

[0086] The beneficial effects of the present invention are as follows: the present invention changes the nonlinear table lookup model of the permanent magnet synchronous motor into an equivalent magnetic circuit electromagnetic model, which, on the one hand, no longer requires the use of finite models to calculate data, thereby improving modeling and calculation efficiency; the nonlinear model of the permanent magnet synchronous motor is established using the equivalent magnetic circuit method, so that the core magnetic permeability and the internal magnetic flux of the motor can be iteratively updated with temperature, and the calculation error of the motor electromagnetic coupling model can be improved under the same simulation accuracy; the motor equivalent magnetic circuit model and the motor thermal network model are bidirectionally coupled, and the motor electromagnetic thermal coupling can be continuously solved through iterative updates of the magnetic permeability and the magnetic flux with temperature, thereby realizing real-time interaction between the motor electromagnetic parameters and the motor temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 The present invention is a flow chart of the method.

[0088] Figure 2 This is the motor equivalent thermal resistance structure diagram of the present invention.

[0089] Figure 3 The schematic diagram of the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor of the present invention DETAILED DESCRIPTION

[0090] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0091] like Figure 1 As shown, in one embodiment of the present invention, a method for modeling electromagnetic-thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network includes the following steps:

[0092] S1. Obtain the material properties and topological structure of the permanent magnet synchronous motor;

[0093] S2. According to the material characteristics and topological structure of the permanent magnet synchronous motor, an equivalent magnetic network model is performed to obtain an electromagnetic model of the motor;

[0094] S3. According to the material properties and topological structure of the permanent magnet synchronous motor, the internal temperature field of the motor is equivalent to multiple thermal resistance units to obtain an equivalent thermal resistance structure of the motor;

[0095] S4. The motor loss is obtained based on the motor electromagnetic model, and according to the motor loss, the core magnetic permeability of the motor electromagnetic model is updated using the motor equivalent thermal resistance structure to achieve bidirectional coupling and complete the permanent magnet synchronous motor electromagnetic thermal dynamic coupling modeling.

[0096] In this embodiment, firstly, according to the material characteristics and topological structure of the permanent magnet synchronous motor, the magnetic field and temperature field inside the motor are respectively analogized to the circuit theory in the electric field, and the magnetic field inside the motor is divided into a plurality of different equivalent magnetic permeability units, and the equivalent magnetic permeability units are used to accurately simulate the magnetic flux flow state inside the motor; the temperature field inside the motor is equivalent to a plurality of different thermal resistance units, and the main losses of the motor (winding copper loss, core loss, mechanical loss) are solved by the established equivalent magnetic network motor electromagnetic model, and these losses are used as the heat source of the motor equivalent thermal network model, and the node temperature of the main components of the motor is accurately solved according to the different energy transfer modes and heat transfer theory. Then, the main node temperature of the motor is fed back to the motor equivalent magnetic network model in real time, and the current motor temperature is queried and updated in real time, and the magnetic permeability, the residual magnetic flux density of the permanent magnet, and the current motor temperature compensation current are calculated and fed back, and the electromagnetic field response characteristics of the motor at the current temperature are further solved. As the motor temperature increases, the electromagnetic thermal coupling response characteristics of the motor at each temperature are continuously solved until the motor reaches thermal equilibrium. Realize the real-time interactive coupling of the motor electromagnetic field and the motor temperature field.

[0097] In this embodiment, the constructed motor electromagnetic model is specifically constructed using a motor dynamic magnetic network modeling method mentioned in the invention patent with publication number CN116992723A. According to the potential magnetic flux paths of different components and regions of the permanent magnet synchronous motor, grid magnetic permeability units of different modules are established to form a motor magnetic network model. In the magnetic network model, the scalar magnetic potential assigned to any node can be analogous to Kirchhoff's law in the electric field law. The sum of the output flux and the sum of the input flux are zero, so the equation for the magnetic network of any node can be established as:

[0098]

[0099] The node algebraic equations of the entire magnetic network are analyzed and solved by Gaussian elimination method. The equations are expressed as:

[0100]

[0101] In the above formula, the magnetic permeability matrix [Λ] n×n Obtained by magnetic network node analysis, [u] n×1 is the unknown nodal scalar magnetic potential, [pm] n×1 is the flux generated by the excitation source at the location. n is the number of nodes in the motor equivalent magnetic network.

[0102] Since the saturation level of the motor stator and rotor core material varies greatly under different temperatures and loads, the magnetic permeability of each core area and at each temperature needs to be considered separately. The nonlinear relationship between the core magnetic permeability and the magnetic flux density in the corresponding area is obtained from the magnetization curve, and the nonlinear relationship between the core magnetic permeability and the magnetic flux density at each temperature is obtained by querying the magnetization curve at different temperatures. The calculation of the magnetic flux density generated in the equivalent magnetic permeability unit can be expressed as:

[0103]

[0104] Where U A , U B is the magnetic potential at both ends of the node, and S is the cross-sectional area of ​​the grid between the nodes. After calculating B, the relative magnetic permeability can be obtained by interpolating on the BH curve of the ferromagnetic material. The permeability of each time step and temperature node is iterated compared with the previous time step and temperature node. The termination condition of the iteration is expressed as:

[0105]

[0106] The saturation degree of the stator and rotor cores of the motor under the current load and temperature is calculated, and the dynamic change of the core magnetic permeability of the motor equivalent magnetic network model is realized.

[0107] The windings in the stator slots will generate a rotating magnetic field under the excitation of three-phase current. The stator tooth flux is a function of the magnetic field state and the excitation state, which can be expressed as:

[0108] φ t,i =Λ st,i (U sy,i -U st,i -F mmf,i )

[0109] In the formula, φ t,i is the magnetic flux passing through the stator teeth, Λ st,i , U st,i , U sy,i 、F mmf,i They are the permeance of the i-th stator tooth, the scalar magnetic potential on both sides of the permeance, and the excitation magnetomotive force at the stator tooth. The flux of the corresponding phase winding of the motor is the sum of the magnetic flux hinged by the corresponding coil and the product of the number of turns. When the motor and winding structure are completely symmetrical, the winding phase flux is associated with the stator and rotor magnetic fields, and the winding flux equations can be expressed as:

[0110]

[0111] In the formula, λ A , B , C is the corresponding phase winding flux, N is the number of turns of the winding coil, Mt It is the phase flux calculation matrix within one pole pair of permanent magnet.

[0112] The winding coils are usually connected in series in the form of distributed windings in the motor. According to the winding distribution law and symmetry, and when the motor structure is completely symmetrical, the winding excitation magnetomotive force model can be expressed as:

[0113]

[0114] In the formula, F mm,i is the magnetomotive force of the i-th stator tooth, M I is the slot ampere-turn and phase current conversion matrix within one pole pair of the permanent magnet, I A ,I B ,I C They are the three-phase currents of the motor respectively.

[0115] The permanent magnet can be composed of an equivalent magnetomotive force source and the magnetic resistance inside the permanent magnet to form an equivalent voltage source, which can be expressed as:

[0116]

[0117] Where F pm is the output voltage of the equivalent voltage source, R pm is the equivalent voltage source internal resistance, H c is the coercive force of the permanent magnet, h pm is the magnetization thickness of the permanent magnet, A pm is the surface area of ​​the permanent magnet, μ0 is the vacuum permeability, μ r Recover the magnetic permeability for the permanent magnet.

[0118] When the motor and winding structure are completely symmetrical, a closed-loop motor electromagnetic model can be composed of a group of magnetic field node equations, a group of winding flux equations, a group of winding excitation magnetomotive force equations and a motor control system model. This model takes a constant speed as input and the magnetic field state and parameters as output.

[0119] In step S3, the motor equivalent thermal resistance structure is symmetrical along the central axis; the central axis includes the casing and the medium convection thermal resistance R connected in sequence. med-housing 、Case thermal resistance R housing , Contact thermal resistance between housing and stator yoke R housing-yoke , stator yoke thermal resistance R yoke , stator tooth conduction thermal resistance R st , air gap convection thermal resistance R airgap , External rotor core conduction thermal resistance R rotor-iron1 , conducted by the internal rotor core thermal resistance R rotor-iron2 and the convection thermal resistance R of the rotor core internal ventilation opening rotor-aircool The parallel group and the contact thermal resistance R between the rotor core and the shaftrotor-shf One side of the central axis includes convection thermal resistance R between the end cover, the housing and the medium med-housing The other end is connected to the external air convection thermal resistance R cap-air and bearing thermal resistance R bear , respectively with the external air convection thermal resistance R cap-air The other end of the winding is connected to the internal air convection thermal resistance R end-air , rotor core and internal air convection thermal resistance R rotor-air and permanent magnet axial conduction thermal resistance R pm-ax , and the convection thermal resistance R between the end winding and the internal air end-air The other end of the winding is connected to the end axial conduction thermal resistance R coil-end , and the axial conduction thermal resistance R between the winding and the end coil-end The other end of the core is connected to the winding contact thermal resistance R iron-coil , and the convection thermal resistance R between the rotor core and the internal air rotor-air The other end of the permanent magnet is connected to the axial conduction thermal resistance R rotor-ax , and the permanent magnet axial conduction thermal resistance R pm-ax The other end of the rotor core connected to the permanent magnet has a thermal resistance R rotor-pm and the bearing thermal resistance R bear The other end is connected to the shaft axial conduction thermal resistance R shf The core and winding contact thermal resistance R iron-coil The other end of the stator is connected to the stator tooth by a thermal conduction resistance R st The axial conduction thermal resistance R of the permanent magnet core rotor-ax The other end and the rotor core and permanent magnet contact thermal resistance R rotor-pm The other end is respectively connected to the external rotor core thermal resistance R rotor-iron1 And the thermal resistance R rotor-iron2 and the convection thermal resistance R of the rotor core internal ventilation opening rotor-aircool The parallel group is connected; the axial thermal conduction resistance R shf The other end of the rotor core and the shaft contact thermal resistance R rotor-shf The other end of the connection.

[0120] In this embodiment, based on the thermal characteristics of the permanent magnet synchronous motor, a thermal network model of the motor internal loss and the motor temperature change (i.e., the motor equivalent thermal resistance structure) is established. The main losses of the motor include winding copper loss, core loss, and mechanical loss. These losses, as heat sources, will cause the motor to rise in temperature during actual operation. The present invention uses an equivalent thermal network model to simulate the motor temperature rise. The thermal resistance and thermal capacity of each component of the motor are equivalent, and they are connected according to the internal heat transfer direction of the motor to form a Figure 2The motor dynamic thermal network model is shown in Figure . The equivalent motor thermal resistance structure and thermal resistance parameters are as follows: Figure 2 As shown in Table 1. The calculation of the motor thermal capacity parameters is expressed as:

[0121] C=ρVC p

[0122] In the formula, ρ, V, C p They are the material density of each motor component, the material volume of each motor component, and the specific heat capacity of each component material. Therefore, the heat capacity parameters of each motor component can be obtained by referring to the manual and information, and the calculated motor heat capacity parameters are added to the dynamic thermal network model of the conductive machine.

[0123] Table 1

[0124]

[0125]

[0126] The step S4 is specifically as follows:

[0127] S401, obtaining electromagnetic parameters of different current working points under different rotor position angles according to the electromagnetic model of the motor, and performing position detection using the electromagnetic parameters of different current working points under different rotor position angles to obtain a mechanical angle;

[0128] S402, according to the motor electromagnetic model, obtain the d-axis voltage U d , stator voltage amplitude V m and three-phase current vector, and transform the three-phase current vector coordinates according to the mechanical angle to obtain the d-axis current i d and q-axis current i q ;

[0129] S403, according to the d-axis current i d , q-axis current i q , d-axis voltage amplitude V d and stator voltage amplitude V m , calculate the equivalent current of motor loss and iron loss;

[0130] S404, using the motor loss as a heat source input to the motor equivalent thermal resistance structure to obtain the node temperature of each motor component;

[0131] S405. According to the node temperatures of each motor component and the iron loss equivalent current, the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model are updated to achieve bidirectional coupling and complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

[0132] The motor loss in step S403 includes motor winding copper loss, core loss and mechanical loss:

[0133] P Cu =3I 2 R

[0134] P Fe =P Fe-oc +P Fe-sc

[0135]

[0136]

[0137] P m =k m n+k ω n 3

[0138] Among them, P Cu is the motor winding copper loss; I is the current value; R is the current temperature resistance value; P Fe is the core loss; P Fe-oc P is the core loss when the motor is unloaded; Fe-sc is the core loss when the motor is short-circuited; a h V is the hysteresis loss coefficient of the motor when the motor is unloaded; m is the stator voltage amplitude; ψ f is the permanent magnet flux; a e is the eddy current loss coefficient of the motor when the motor is unloaded; a x b is the additional loss coefficient of the motor when the motor is unloaded; h V is the motor hysteresis loss coefficient when the motor is short-circuited; d is the d-axis voltage amplitude; b e b is the eddy current loss coefficient of the motor when the motor is short-circuited; x is the additional loss coefficient of the motor when the motor is short-circuited; ω e is the motor electrical speed; d is the d-axis magnetic flux; ψ q is the q-axis magnetic flux; P m is the mechanical loss; k m is the friction coefficient; k ω is the drag coefficient; n is the motor speed.

[0139] In this embodiment, the copper loss of the motor winding is mainly due to the thermal effect of the current. When the current flows through the winding, the current generates heat by doing work. Therefore, the copper loss is mainly related to the current size. For a three-phase motor, the copper loss calculation formula is:

[0140] P Cu =3I 2 R

[0141] Where I is the current value, and R is the current temperature resistance value.

[0142] Core loss occurs in the magnetic core of the stator and rotor. The classic Bertotti core loss model mainly consists of two parts: hysteresis loss and eddy current loss. In order to compensate for the loss associated with the existence of magnetic domains, an additional component of eddy current loss is also included, which leads to various dependent uncontrollable properties in the magnetization process, that is, additional losses. Therefore, the core loss can be expressed as:

[0143]

[0144] In the formula, B m is the peak value of the core magnetic flux density, k h , k c , k e They are hysteresis loss coefficient, eddy current loss coefficient and additional loss coefficient respectively, and f is the electrical frequency.

[0145] However, since the peak value of the flux density at each working point and the coefficients in the formula are difficult to obtain, the above iron loss calculation model is difficult to use for electromagnetic thermal coupling. The present invention adopts an analytical method to calculate the core loss by using electromagnetic parameters such as motor flux, voltage, and current under different working conditions. The core loss model of the motor under no-load and short-circuit conditions can be expressed as:

[0146]

[0147]

[0148] Therefore, the core loss can be calculated using the electromagnetic parameters such as motor flux, voltage, current, etc., which can be expressed as:

[0149] P Fe =P Fe-oc +P Fe-sc

[0150] The mechanical loss of the motor is usually composed of friction loss and wind friction loss. Friction loss is mainly generated at the motor bearing installation and is related to the lubrication conditions. Since the friction torque is constant, it is generally believed that its loss value is proportional to the motor speed. Wind friction loss is related to the motor's structural shape and fluid state. It is generally believed that wind resistance loss is proportional to the cube of the motor speed. Therefore, friction and wind friction losses can be expressed as:

[0151] P m =k m n+k ω n 3

[0152] In the formula, k m , k ω , n are the friction coefficient, wind resistance coefficient and motor speed respectively, and these coefficients can be obtained through engineering experience fitting.

[0153] The expression of the iron loss equivalent current in step S403 is:

[0154]

[0155] Among them, i dFe is the d-axis iron loss equivalent current; i qFe is the q-axis iron loss equivalent current; P Fe is the core loss; ω e is the motor electrical speed; d is the d-axis magnetic flux; ψ q is the q-axis magnetic flux.

[0156] In this embodiment, the motor electromagnetic thermal dynamic coupling model is obtained by bidirectionally coupling the established motor electromagnetic model and motor equivalent thermal network model. The specific implementation steps are:

[0157] The motor loss is calculated based on the motor closed-loop model, and the loss is input into the motor equivalent thermal network model as the heat source. The real-time node temperature is used to update the core magnetic permeability and permanent magnet residual magnetic density in the motor equivalent magnetic network model in real time to quantify the impact of motor temperature on the motor magnetic field. At the same time, it is necessary to quantify the impact of temperature on electromagnetic characteristics. The impact of temperature on electromagnetic characteristics can be attributed to the change of temperature on current.

[0158] When the total core loss and dq-axis flux are known, the relationship between the iron loss equivalent current and the total iron loss is expressed as:

[0159]

[0160] In the formula, id Fe andiq Fe It will be added to the electromagnetic model in the form of compensation current, and after superposition it will be fed back to the motor electromagnetic model to adjust the stator current at the next moment.

[0161] The expression of the node temperature of each component of the motor in step S404 is:

[0162]

[0163] C x =ρ x V x C p,x

[0164] Among them, θ x is the temperature of node x; d is the differential sign; t is the time; C x is the component heat capacity at node x; R x,y is the thermal resistance between node x and node y; θ y is the temperature of node y; P xis the motor loss; x V is the material density of the component at node x; x is the material volume of the component at node x; C p,x is the specific heat capacity of the component material at node x.

[0165] The step S405 is specifically as follows:

[0166] S4051. According to the node temperatures of each motor component, the thermal network state space equation is obtained:

[0167]

[0168]

[0169]

[0170]

[0171]

[0172] D=0

[0173] in, is the first-order derivative of the nodal temperature of each component of the motor with respect to time; t is time; A is the coefficient matrix of the thermal resistance and thermal capacity of the motor; θ(t) is the nodal temperature of each component of the motor; B is the coefficient matrix of the nodal thermal capacity of each component of the motor; p(t) is the motor loss at time t; y(t) is the algebra of the equation; C and D are both coefficient matrices; is the first derivative of the n'th row node temperature with respect to time; c n' is the heat capacity of the n'th row node; R 1,n' is the thermal resistance of the node in row 1 and column n'; R n',i is the thermal resistance of the node at the n'th row and the i-th column; i is the column number of the node matrix; n' is the row number of the node matrix;

[0174] S4052. Obtain the node temperature of each component under real-time working conditions according to the thermal network state space equation;

[0175] S4053. According to the node temperature of each component and the iron loss equivalent current under real-time working conditions, the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model are updated to achieve bidirectional coupling and complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

[0176] The step S4053 is specifically as follows:

[0177] S40531, set the target mechanical speed ω m ';

[0178] S40532: According to the mechanical rotation angle, the speed and position are fed back to obtain the actual mechanical speed ωm ;

[0179] S40533, according to the target mechanical speed ω m ' and actual mechanical speed ω m , perform PI control and obtain the three-phase current synthesis vector;

[0180] S40534, performing MTPA maximum torque current ratio control on the three-phase current synthesis vector to obtain a given d-axis current and a given q-axis current respectively;

[0181] S40535, according to the given d-axis current and d-axis current i d , get the d-axis current difference;

[0182] S40536, according to the given q-axis current and q-axis current i q , get the q-axis current difference;

[0183] S40537, performing PI control according to the d-axis current difference and the q-axis current difference, respectively, to obtain a d-axis voltage given value and a q-axis voltage given value;

[0184] S40538. Calculate the temperature compensation current based on the iron loss equivalent current and the node temperature of each component under real-time working conditions:

[0185] S40539, obtaining the d-axis voltage at the next moment and the q-axis voltage at the next moment respectively according to the d-axis voltage given value, the q-axis voltage given value and the temperature compensation current;

[0186] S405310, according to the d-axis voltage at the next moment and the q-axis voltage at the next moment, after Park transformation, obtain the α-β axis voltage command U αβ ;

[0187] S405311, according to the α-β axis voltage command U αβ , using the vector pulse width modulation algorithm SVPWM, the pulse signal controlled at the current moment is obtained;

[0188] S405312. According to the node temperature of each component under real-time working conditions, query the magnetization curves at different temperatures, and update the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model;

[0189] S405313. Using the motor electromagnetic model updated in S404312, based on the pulse signal operation controlled at the current moment, bidirectional coupling is achieved to complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

[0190] The step S40538 is specifically as follows:

[0191] S405381. Calculate the dq axis current at the current temperature according to the node temperature of each component under real-time working conditions:

[0192]

[0193] Among them, i dT is the d-axis current at the current temperature; i qT is the q-axis current at the current temperature; T is the node temperature of each component of the motor; T0 is the initial temperature of the motor; i d (ψ d ,ψ q ,θ e ) is the inverse mapping function of d-axis flux and current; i q (ψ d ,ψ q ,θ e ) is the inverse mapping function of the q-axis flux and current; Δ is the sign of the change; θ e is the electrical angle;

[0194] S405382. Superimpose the dq axis current and the iron loss equivalent current at the current temperature to obtain the temperature compensation current.

[0195] The step S40539 is specifically as follows:

[0196] S405391. Calculate the stator winding resistance at the current temperature:

[0197] R=R0[1+α(T-T0)]

[0198] Where R is the stator winding resistance at the current temperature; R0 is the resistance value at the initial temperature; α is the resistance temperature coefficient;

[0199] S405392, obtaining a temperature compensation voltage according to the temperature compensation current and the stator winding resistance at the current temperature;

[0200] S405393. According to the temperature compensation voltage, the q-axis voltage given value and the d-axis voltage given value, the d-axis voltage at the next moment and the q-axis voltage at the next moment are obtained respectively.

[0201] In this embodiment, the effect of temperature on the stator winding resistance is expressed as:

[0202] R=R0[1+α(T-T0)]

[0203] Where T0 is the initial temperature of the motor, T is the current temperature of the motor, α is the resistance temperature coefficient, and R0 is the resistance value at the initial temperature.

[0204] The permanent magnet temperature affects both the d-axis and q-axis fluxes, and this effect also varies with the current (load) and rotor position. In order to consider the effect of temperature in the established electromagnetic model, it is necessary to correct the d-axis and q-axis currents according to the temperature change of the rotor permanent magnet. Adding the temperature compensation current to the original current gives the current temperature characteristic formula.

[0205] Therefore, the motor electromagnetic model and the motor thermal network model are forwardly conducted through loss, and reversely conducted through magnetic permeability, magnetic flux, current, and resistance. Figure 3 The schematic diagram of the modeling principle of the permanent magnet synchronous motor electromagnetic thermal dynamic coupling is shown in the figure. As the motor temperature increases, the electromagnetic thermal coupling response characteristics of the motor at each temperature are continuously solved until the motor reaches thermal equilibrium. Real-time interactive coupling of the motor electromagnetic field and the motor temperature field is achieved.

Claims

1. A method for modeling electromagnetic-thermal dynamic coupling of permanent magnet synchronous motor based on equivalent magnetic network, characterized in that: The following steps are involved: S1. Obtain the material properties and topological structure of the permanent magnet synchronous motor; S2. According to the material characteristics and topological structure of the permanent magnet synchronous motor, an equivalent magnetic network model is performed to obtain an electromagnetic model of the motor; S3. According to the material properties and topological structure of the permanent magnet synchronous motor, the internal temperature field of the motor is equivalent to multiple thermal resistance units to obtain an equivalent thermal resistance structure of the motor; S4, based on the motor electromagnetic model, the motor loss is obtained, and according to the motor loss, the core magnetic permeability of the motor electromagnetic model is updated using the motor equivalent thermal resistance structure to achieve bidirectional coupling and complete the permanent magnet synchronous motor electromagnetic thermal dynamic coupling modeling; the step S4 is specifically as follows: S401, obtaining electromagnetic parameters of different current working points under different rotor position angles according to the electromagnetic model of the motor, and performing position detection using the electromagnetic parameters of different current working points under different rotor position angles to obtain a mechanical angle; S402, according to the motor electromagnetic model, obtain the d-axis voltage U d , stator voltage amplitude V m and three-phase current vector, and transform the three-phase current vector coordinates according to the mechanical angle to obtain the d-axis current i d and q-axis current i q ; S403, according to the d-axis current i d , q-axis current i q , d-axis voltage amplitude V d and stator voltage amplitude V m , calculate the equivalent current of motor loss and iron loss; S404, using the motor loss as a heat source input to the motor equivalent thermal resistance structure to obtain the node temperature of each motor component; S405, according to the node temperature of each component of the motor and the iron loss equivalent current, update the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model, realize bidirectional coupling, and complete the electromagnetic thermal dynamic coupling modeling of the permanent magnet synchronous motor; the step S405 is specifically as follows: S4051. According to the node temperatures of each motor component, the thermal network state space equation is obtained: D＝0 in, is the first-order derivative of the nodal temperature of each component of the motor with respect to time; t is time; A is the coefficient matrix of the thermal resistance and thermal capacity of the motor; θ(t) is the nodal temperature of each component of the motor; B is the coefficient matrix of the nodal thermal capacity of each component of the motor; p(t) is the motor loss at time t; y(t) is the algebra of the equation; C and D are both coefficient matrices; is the first derivative of the n'th row node temperature with respect to time; c n' is the heat capacity of the n'th row node; R 1,n' is the thermal resistance of the node in row 1 and column n'; R n',i is the thermal resistance of the node at the n'th row and the i-th column; i is the column number of the node matrix; n' is the row number of the node matrix; S4052. Obtain the node temperature of each component under real-time working conditions according to the thermal network state space equation; S4053, according to the node temperature of each component and the iron loss equivalent current under real-time working conditions, the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model are updated to achieve bidirectional coupling and complete the electromagnetic thermal dynamic coupling modeling of the permanent magnet synchronous motor; the step S4053 is specifically as follows: S40531, set the target mechanical speed ω m '; S40532: According to the mechanical rotation angle, the speed and position are fed back to obtain the actual mechanical speed ω m ; S40533, according to the target mechanical speed ω m ' and actual mechanical speed ω m , perform PI control and obtain the three-phase current synthesis vector; S40534, performing MTPA maximum torque current ratio control on the three-phase current synthesis vector to obtain a given d-axis current and a given q-axis current respectively; S40535, according to the given d-axis current and d-axis current i d , get the d-axis current difference; S40536, according to the given q-axis current and q-axis current i q , get the q-axis current difference; S40537, performing PI control according to the d-axis current difference and the q-axis current difference, respectively, to obtain a d-axis voltage given value and a q-axis voltage given value; S40538, calculating the temperature compensation current according to the iron loss equivalent current and the node temperature of each component under real-time working conditions; the step S40538 is specifically as follows: S405381. Calculate the dq axis current at the current temperature according to the node temperature of each component under real-time working conditions: Among them, i dT is the d-axis current at the current temperature; i qT is the q-axis current at the current temperature; T is the node temperature of each component of the motor; T0 is the initial temperature of the motor; i d (ψ d ,ψ q ,θ e ) is the inverse mapping function of d-axis flux and current; i q (ψ d ,ψ q ,θ e ) is the inverse mapping function of the q-axis flux and current; Δ is the sign of the change; θ e is the electrical angle; S405382, superimposing the dq axis current and the iron loss equivalent current at the current temperature to obtain a temperature compensation current; S40539, obtaining the d-axis voltage at the next moment and the q-axis voltage at the next moment respectively according to the d-axis voltage given value, the q-axis voltage given value and the temperature compensation current; S405310, according to the d-axis voltage at the next moment and the q-axis voltage at the next moment, after Park transformation, obtain the α-β axis voltage command U αβ ; S405311, according to the α-β axis voltage command U αβ , using the vector pulse width modulation algorithm SVPWM, the pulse signal controlled at the current moment is obtained; S405312. According to the node temperature of each component under real-time working conditions, query the magnetization curves at different temperatures, and update the core magnetic permeability and permanent magnet residual flux density of the motor electromagnetic model; S405313. Using the motor electromagnetic model updated in S404312, based on the pulse signal operation controlled at the current moment, bidirectional coupling is achieved to complete the electromagnetic-thermal dynamic coupling modeling of the permanent magnet synchronous motor.

2. The method for modeling the electromagnetic-thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network according to claim 1 is characterized in that: In step S3, the motor equivalent thermal resistance structure is symmetrical along the central axis; the central axis includes the casing and the medium convection thermal resistance R connected in sequence. med-housing 、Case thermal resistance R housing , Contact thermal resistance between housing and stator yoke R housing-yoke , stator yoke thermal resistance R yoke , stator tooth conduction thermal resistance R st , air gap convection thermal resistance R airgap , External rotor core conduction thermal resistance R rotor-iron1 , conducted by the internal rotor core thermal resistance R rotor-iron2 and the convection thermal resistance R of the rotor core internal ventilation opening rotor-aircool The parallel group and the contact thermal resistance R between the rotor core and the shaft rotor-shf One side of the central axis includes convection thermal resistance R between the end cover, the housing and the medium med-housing The other end is connected to the external air convection thermal resistance R cap-air and bearing thermal resistance R bear , respectively with the external air convection thermal resistance R cap-air The other end of the winding is connected to the internal air convection thermal resistance R end-air , rotor core and internal air convection thermal resistance R rotor-air and permanent magnet axial conduction thermal resistance R pm-ax , and the convection thermal resistance R between the end winding and the internal air end-air The other end of the winding is connected to the end axial conduction thermal resistance R coil-end , and the axial conduction thermal resistance R between the winding and the end coil-end The other end of the core is connected to the winding contact thermal resistance R iron-coil , and the convection thermal resistance R between the rotor core and the internal air rotor-air The other end of the permanent magnet is connected to the axial conduction thermal resistance R rotor-ax , and the permanent magnet axial conduction thermal resistance R pm-ax The other end of the rotor core connected to the permanent magnet has a thermal resistance R rotor-pm and the bearing thermal resistance R bear The other end is connected to the shaft axial conduction thermal resistance R shf The core and winding contact thermal resistance R iron-coil The other end of the stator is connected to the stator tooth by a thermal conduction resistance R st The axial conduction thermal resistance R of the permanent magnet core rotor-ax The other end and the rotor core and permanent magnet contact thermal resistance R rotor-pm The other end is respectively connected to the external rotor core thermal resistance R rotor-iron1 And the thermal resistance R rotor-iron2 and the convection thermal resistance R of the rotor core internal ventilation opening rotor-aircool The parallel group is connected; the axial thermal conduction resistance R shf The other end of the rotor core and the shaft contact thermal resistance R rotor-shf The other end of the connection.

3. The method for modeling the electromagnetic-thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network according to claim 1 is characterized in that: The motor loss in step S403 includes motor winding copper loss, core loss and mechanical loss: P Cu =3I 2 R P Fe =P Fe-oc +P Fe-sc P m =k m n+k ω n 3 Among them, P Cu is the motor winding copper loss; I is the current value; R is the current temperature resistance value; P Fe is the core loss; P Fe-oc P is the core loss when the motor is unloaded; Fe-sc is the core loss when the motor is short-circuited; a h V is the hysteresis loss coefficient of the motor when the motor is unloaded; m is the stator voltage amplitude; ψ f is the permanent magnet flux; a e is the eddy current loss coefficient of the motor when the motor is unloaded; a x b is the additional loss coefficient of the motor when the motor is unloaded; h V is the motor hysteresis loss coefficient when the motor is short-circuited; d is the d-axis voltage amplitude; b e b is the eddy current loss coefficient of the motor when the motor is short-circuited; x is the additional loss coefficient of the motor when the motor is short-circuited; ω e is the motor electrical speed; d is the d-axis magnetic flux; ψ q is the q-axis magnetic flux; P m is the mechanical loss; k m is the friction coefficient; k ω is the drag coefficient; n is the motor speed.

4. The method for modeling the electromagnetic-thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network according to claim 1 is characterized in that: The expression of the iron loss equivalent current in step S403 is: Among them, i dFe is the d-axis iron loss equivalent current; i qFe is the q-axis iron loss equivalent current; P Fe is the core loss; ω e is the motor electrical speed; d is the d-axis magnetic flux; ψ q is the q-axis magnetic flux.

5. The method for modeling the electromagnetic-thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network according to claim 1 is characterized in that: The expression of the node temperature of each component of the motor in step S404 is: C x =ρ x V x C p,x Among them, θ x is the temperature of node x; d is the differential sign; t is the time; C x is the component heat capacity at node x; R x,y is the thermal resistance between node x and node y; θ y is the temperature of node y; P x is the motor loss; x V is the material density of the component at node x; x is the material volume of the component at node x; C p,x is the specific heat capacity of the component material at node x.

6. The method for modeling the electromagnetic-thermal dynamic coupling of a permanent magnet synchronous motor based on an equivalent magnetic network according to claim 1 is characterized in that: The step S40539 is specifically as follows: S405391. Calculate the stator winding resistance at the current temperature: R=R0[1+α(T-T0)] Where R is the stator winding resistance at the current temperature; R0 is the resistance value at the initial temperature; α is the resistance temperature coefficient; S405392, obtaining a temperature compensation voltage according to the temperature compensation current and the stator winding resistance at the current temperature; S405393. According to the temperature compensation voltage, the q-axis voltage given value and the d-axis voltage given value, the d-axis voltage at the next moment and the q-axis voltage at the next moment are obtained respectively.

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