Permanent magnet flux linkage online identification method of permanent magnet synchronous motor considering cross coupling effect

Abstract

The application discloses an online permanent magnet flux identification method of a permanent magnet synchronous motor considering cross coupling effect and belongs to the permanent magnet flux identification technology of the permanent magnet synchronous motor. The application aims at solving the problem that the existing permanent magnet synchronous motor flux identification method does not consider the cross coupling influence of the motor, thereby causing the error of the flux observation result to be large. The application comprises the following steps: under the online stable working condition of the motor, injecting a sinusoidal current signal into the dq axis of the motor to realize three-phase direct current signal injection; calculating the motor stator resistance; injecting two groups of direct current bias voltage into the d-axis of the motor through the current loop, establishing three motor voltage equations, and then obtaining two motor voltage difference equations which eliminate the flux terms; solving to obtain the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq ; establishing the dq-axis voltage equation considering the cross coupling, calculating the motor permanent magnet flux based on the motor stator resistance, the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq . The application is used for the online identification of the permanent magnet flux of the permanent magnet synchronous motor.

Description

TECHNICAL FIELD

[0001] The application relates to an online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effects and belongs to the technical field of permanent magnet flux linkage identification of a permanent magnet synchronous motor. BACKGROUND

[0002] With the development and application of permanent magnet materials, motors based on rare earth permanent magnet materials have attracted more and more attention. Since the rare earth permanent magnet can provide a stable and constant magnetic field without further excitation by current, the rotor structure of the permanent magnet synchronous motor can be simpler, and the overall motor can have higher power density and torque density. At the same time, due to the good dynamic performance and control accuracy of the permanent magnet synchronous motor, it has occupied an important position in many industrial fields, such as the aerospace field, the public transportation field and the high-end manufacturing field.

[0003] The control method used by the permanent magnet synchronous motor usually includes vector control and direct torque control. The motor vector control model needs to determine the motor cross-axis component and realize accurate regulation and control of the motor magnetic field, and the permanent magnet flux linkage is one of the core parameters in the voltage equation. The direct torque control also needs the motor flux linkage value to realize direct regulation and control of the motor torque. For the above control strategies, obtaining the motor permanent magnet flux linkage value has important value for the magnetic field orientation position in the control process and the maximum output torque control effect.

[0004] In addition, the motor permanent magnet flux linkage can also provide a basis for motor state monitoring and fault diagnosis. For example, due to factors such as motor stator winding resistance and harmonic loss, the motor rotor temperature rises, causing the permanent magnet operating point to deviate and thus the flux linkage to decrease. At the same time, observation of the permanent magnet flux linkage can realize monitoring of potential permanent magnet faults, such as local demagnetization and overall demagnetization. At present, the observation method for the flux linkage is mostly based on the motor voltage equation, but the traditional voltage equation modeling ignores the cross-coupling effect of the motor, so an error is generated in the flux linkage observation process.

[0005] In summary, it is of great significance to propose a high-precision permanent magnet motor flux linkage identification method that can consider the cross-coupling effect. SUMMARY

[0006] In view of the problem that the existing permanent magnet synchronous motor flux linkage identification method does not consider the cross-coupling effect of the motor, causing a large error in the flux linkage observation result, the application provides an online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effects.

[0007] The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effects provided by the application comprises the following steps.

[0008] Step one: in the online stable working condition of the motor, sinusoidal current signals are injected into the dq axis of the motor to realize three-phase direct current signal injection; the motor stator resistance is calculated according to three-phase voltage signals and three-phase current signals before and after the sinusoidal current signal injection;

[0009] Step two: two groups of direct current bias voltages are injected into the d-axis of the motor through the current loop, the q-axis current is adjusted through the PI controller to keep the motor working state stable; the dq-axis voltage and the dq-axis current before the direct current bias voltage injection, after the first group of direct current bias voltage injection and after the second group of direct current bias voltage injection are collected, three motor voltage equations are established; the second motor voltage equation is subtracted from the first motor voltage equation, and the third motor voltage equation is subtracted from the second motor voltage equation to obtain two motor voltage difference equations in which the flux linkage terms are eliminated; the recursive least square algorithm is used to solve the two motor voltage equations in which the flux linkage terms are eliminated to obtain the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq ;

[0010] Step three: the dq-axis voltage equation considering cross coupling is established, the motor permanent magnet flux is calculated based on the motor stator resistance, the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq .

[0011] According to the permanent magnet synchronous motor permanent magnet flux online identification method considering cross coupling effect of the application, in step one, according to the fact that the motor three-phase resistance, the dq-axis resistance and the motor stator resistance are equal, the motor three-phase resistance, the dq-axis resistance and the motor stator resistance are uniformly represented as R s ;

[0012] The three-phase voltage equation of the permanent magnet motor is established:

[0013]

[0014] In the formula, u a is the A-phase voltage, u b is the B-phase voltage, u c is the C-phase voltage, i a is the A-phase current, i b is the B-phase current, i c is the C-phase current, p is a differential operator, L aa is the stator A-phase winding self-inductance, L bb is the stator B-phase winding self-inductance, L cc is the stator C-phase winding self-inductance, M ab =M ba is the stator AB-phase winding mutual inductance, M ac =M ca is the stator AC-phase winding mutual inductance.bc = M cb is the mutual inductance of stator BC phase winding, ψ f is the permanent magnet flux linkage of motor, θ e is the rotor position angle.

[0015] According to the permanent magnet synchronous motor permanent magnet flux linkage online identification method considering cross coupling effect of the application, in step one, when the motor dq axis injects a sinusoidal current signal, the corresponding voltage equation is:

[0016]

[0017] In the formula, Δu a is the A-phase voltage difference before and after the injection of the sinusoidal current signal, Δu b is the B-phase voltage difference before and after the injection of the sinusoidal current signal, Δu c is the C-phase voltage difference before and after the injection of the sinusoidal current signal, Δi a is the A-phase current difference before and after the injection of the sinusoidal current signal, Δi b is the B-phase current difference before and after the injection of the sinusoidal current signal, Δi c is the C-phase current difference before and after the injection of the sinusoidal current signal.

[0018] According to the permanent magnet synchronous motor permanent magnet flux linkage online identification method considering cross coupling effect of the application, setting the injection of the sinusoidal current signal to the motor dq axis is:

[0019]

[0020] In the formula, Δi d_inj is the current signal injected to the d-axis, Δi q_inj is the current signal injected to the q-axis, I dc is the amplitude of the sinusoidal current signal;

[0021] The current signals injected to the dq axes Δi d_inj and Δi q_inj are subjected to coordinate transformation, and the injection current expression in the three-phase coordinate system is obtained:

[0022]

[0023] Then, for the A-phase, the motor stator resistance R s is:

[0024] R s = Δu a Δi a .

[0025] According to the permanent magnet synchronous motor permanent magnet flux linkage online identification method considering cross coupling effect of the application, in step two, three motor voltage equations are established:

[0026]

[0027] where u q0 is the q-axis voltage before DC bias voltage injection, u q1 is the q-axis voltage after the first set of DC bias voltage injection, u q2 is the q-axis voltage after the second set of DC bias voltage injection, i q0 is the q-axis current before DC bias voltage injection, i q1 is the q-axis current after the first set of DC bias voltage injection, i q2 is the q-axis current after the second set of DC bias voltage injection, ω e is the motor speed, i d0 is the d-axis current before DC bias voltage injection, i d1 is the d-axis current after the first set of DC bias voltage injection, i d2 is the d-axis current after the second set of DC bias voltage injection.

[0028] According to the permanent magnet synchronous motor permanent magnet flux online identification method considering cross coupling effect of the application, in step two, two motor voltage equations eliminating flux terms are:

[0029]

[0030] where u q01 is the difference between u q1 and u q0 , u q12 is the difference between u q2 and u q1 , i q01 is the difference between i q1 and i q0 , i q12 is the difference between i q2 and i q1 , i d01 is the difference between i d1 and i d0 , i d12 is the difference between i d2 and i d1 .

[0031] According to the permanent magnet synchronous motor permanent magnet flux online identification method considering cross coupling effect of the application, in step two, the method for solving motor d-axis self-inductance L d and motor dq-axis mutual inductance L dq by using recursive least squares algorithm includes:

[0032]

[0033] Wherein e is the error matrix of the least square algorithm, y is the output matrix of the least square algorithm, lambda is the feedback matrix of the least square algorithm, and rho is the parameter matrix of the least square algorithm.

[0034] According to the permanent magnet synchronous motor permanent magnet flux online identification method considering cross coupling effect of the application, in step three, the dq axis voltage equation considering cross coupling is:

[0035]

[0036] Wherein u d is the d-axis voltage of the motor under online stable working condition, u q is the q-axis voltage of the motor under online stable working condition, i d is the d-axis current of the motor under online stable working condition, i q is the q-axis current of the motor under online stable working condition, and L q is the q-axis self-inductance of the motor.

[0037] According to the permanent magnet synchronous motor permanent magnet flux online identification method considering cross coupling effect of the application, in step three, the calculation formula of the motor permanent magnet flux is:

[0038]

[0039] The application has the advantages that the method solves the problem that the existing permanent magnet flux online identification method does not consider the cross coupling effect, and the method is realized based on composite signal injection, wherein the resistance identification is realized based on three-phase signal injection, two groups of signals are injected based on the d-axis to realize the construction of the voltage difference equation, and the flux is finally solved by obtaining the inductance. The mutual inductance and angle error caused by the cross coupling effect are considered in the flux solving model, and the flux identification accuracy is improved.

[0040] The method takes the permanent magnet flux identification as the target, realizes the step-by-step elimination of the rank number in the identification process based on the composite signal injection method, avoids the coupling error problem between different electrical parameters while considering the cross coupling effect, and improves the robustness of the flux identification process. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is the permanent magnet synchronous motor dq axis system reference model considering the cross coupling effect of the application method; the figure includes abc phase position, dq axis system position, and offset axis system d r q r axis system generated by cross coupling, and alpha beta is the motor static axis system; N and S respectively correspond to the positive and negative poles of the permanent magnet; theta r is the cross coupling effect angle.

[0042] Figure 2is the magnetic chain online identification block diagram of the method of the application; it mainly includes intermediate parameter (resistance and inductance) estimation link and magnetic chain solving link; i d * is the d-axis current instruction, i q * is the q-axis current instruction;

[0043] Figure 3 is the motor stator resistance identification method block diagram;

[0044] Figure 4 is the inductance identification process signal injection strategy; the signal injection shown in the figure ensures that the motor operating point always exists on the constant torque curve of the current working condition;

[0045] Figure 5 is the permanent magnet synchronous motor permanent magnet magnetic chain online identification method flow chart considering the cross coupling effect according to the application; the figure contains resistance identification link, inductance identification link and magnetic chain identification link;

[0046] Figure 6 is the magnetic chain identification result under all working conditions obtained by using the method of the application. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the application.

[0048] It should be noted that, in the case of no conflict, the embodiments in the application and the features in the embodiments can be combined with each other.

[0049] The application will be further described below with reference to the drawings and specific embodiments, but not as a limitation of the application.

[0050] DETAILED DESCRIPTION Figures 1 to 6 According to the application, a permanent magnet synchronous motor permanent magnet magnetic chain online identification method considering cross coupling effect is provided, which comprises,

[0051] Step 1: The magnetic chain identification process contains resistance value, and the value is usually unknown, so the resistance is identified first. In order to make the magnetic chain solving model full rank, under the condition of online stable working condition of the motor, the sinusoidal current signal is injected into the motor dq axis to realize three-phase direct current signal injection; when the motor state reaches stability, the three-phase voltage and current information before and after signal injection are recorded respectively, and then the motor stator resistance is calculated according to the three-phase voltage signal and three-phase current signal before and after sinusoidal current signal injection;

[0052] Step two: in the process of online operation of the motor, two groups of direct current bias voltage are injected to the d-axis of the motor through the current loop, the q-axis current is adjusted through the PI controller to realize self-adjustment, each group of d-axis signal injection time is long enough to make the motor enter steady state and the working state remains stable, ensuring the constant output performance of the motor in the parameter identification process; since the working point of the motor before and after the injection signal is always on the constant torque curve, the working condition of the motor in the parameter identification process is unchanged;

[0053] Under the steady state of the motor, the dq-axis voltage and dq-axis current before the direct current bias voltage injection, after the first group of direct current bias voltage injection and after the second group of direct current bias voltage injection are collected respectively, three motor voltage equations are established; then through the difference method, the second motor voltage equation and the first motor voltage equation are subtracted, and the third motor voltage equation and the second motor voltage equation are subtracted, two motor voltage difference equations which eliminate the flux linkage term and only contain the inductance parameter are obtained; then recursive least squares algorithm (RLS) is used to solve the two motor voltage equations which eliminate the flux linkage term, the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq are obtained.

[0054] Step three: the dq-axis voltage equation considering cross-coupling is established, and the general solution formula of the permanent magnet flux linkage of the motor under different operating conditions is constructed. Considering that the motor voltage and current signals can be obtained through the controller, the identification of the motor resistance and inductance is realized preferentially; then the motor stator resistance, the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq are calculated to obtain the motor permanent magnet flux linkage.

[0055] The embodiment constructs the general voltage equation mathematical model after cross-coupling error correction by considering the influence of cross-coupling effect on the voltage equation model of the permanent magnet synchronous motor. Based on the relationship between the current and voltage before and after the composite signal injection, the motor resistance and inductance are solved preferentially, and finally the online observation of the flux linkage is realized based on the proposed motor model.

[0056] The motor shaft system model considering cross-coupling is constructed as shown in Figure 1 , and the motor coordinate system considering cross-coupling is defined as d r q r shaft system in view of the phenomenon that the q-axis armature reaction caused by cross-coupling makes the coordinate system deviate; the angle between the motor dq-axis system and the shaft system d r q r after armature reaction is θ r ; the general voltage equation mathematical model considering cross-coupling is constructed, the mathematical relationship between the permanent magnet flux linkage and other electrical parameters is determined, and the flux linkage identification method is given.

[0057] Further, in combination with Figure 3 As shown in the step one, by motor coordinate system change relationship can prove that the motor three-phase resistance and dq axis resistance value is equal. The motor three-phase resistance, dq axis resistance and stator resistance in the application is uniformly expressed as R s ;

[0058] The three-phase voltage equation of the permanent magnet motor is established:

[0059]

[0060] In the formula, u a is the A-phase voltage, u b is the B-phase voltage, u c is the C-phase voltage, i a is the A-phase current, i b is the B-phase current, i c is the C-phase current, p is the differential operator, L aa is the self-inductance of the stator A-phase winding, L bb is the self-inductance of the stator B-phase winding, L cc is the self-inductance of the stator C-phase winding, M ab =M ba is the mutual inductance of the stator AB-phase winding, M ac =M ca is the mutual inductance of the stator AC-phase winding, M bc =M cb is the mutual inductance of the stator BC-phase winding, ψ f is the permanent magnet flux linkage of the motor, θ e is the rotor position angle.

[0061] In step one, when the motor dq axis injects a sinusoidal current signal, there is a direct current component in the motor three-phase, and the voltage equation corresponding to the direct current component is:

[0062]

[0063] In the formula, Δu a is the A-phase voltage difference before and after the injection of the sinusoidal current signal, Δu b is the B-phase voltage difference before and after the injection of the sinusoidal current signal, Δu c is the C-phase voltage difference before and after the injection of the sinusoidal current signal, Δi a is the A-phase current difference before and after the injection of the sinusoidal current signal, Δi b is the B-phase current difference before and after the injection of the sinusoidal current signal, Δi c is the C-phase current difference before and after the injection of the sinusoidal current signal.

[0064] When DC appears in three-phase, the resistance can be calculated based on the relationship between three-phase voltage and current. Since motor control is realized through dq axis, the injection of three-phase DC signal is realized by injecting signal to dq axis in the present application.

[0065] The sinusoidal fundamental frequency current signal injected to the motor dq axis is set as:

[0066]

[0067] In the formula, Δi d_inj is the current signal injected to d-axis, Δi q_inj is the current signal injected to q-axis, I dc is the amplitude of sinusoidal current signal.

[0068] The current signals Δi d_inj and Δi q_inj injected to dq axis are subjected to coordinate transformation to obtain the expression of injected current in three-phase coordinate system:

[0069]

[0070] Then, for phase A, the DC components of motor three-phase voltage and current are extracted when the signal is injected to obtain the motor stator resistance R s The online identification formula is:

[0071] R s = Δu a / Δi a .

[0072] The inductances required in the flux identification process are L d and L dq , and the mathematical model used in identification is the q-axis voltage equation considering cross coupling.

[0073] Since the resistance value does not change with the motor operating state, and the value changes relatively small compared to the rest of the electrical parameters when the motor is online, the resistance can be identified first. The resistance identification block diagram is shown in Figure 3 .

[0074] Further, considering that the flux identification needs to obtain the motor self-inductance and mutual inductance information at the same time, the identification of motor inductance needs to be realized before the flux identification. A method of inductance identification based on d-axis signal injection is described in Figure 4 The inductances required in the flux identification process are L d and L dq , and the mathematical model used in identification is the q-axis voltage equation considering cross coupling. Specifically as follows:

[0075] In step two, two different DC signals are injected to the d-axis of the motor when the motor is running online. At this time, the motor control is still realized by PI. When the d-axis signal injection process is in progress, the q-axis current is self-adjusted by PI, so that the motor output characteristic remains unchanged, thereby ensuring that the motor remains stable in the signal injection process. The signal injection schematic is shown in FIG. 1. Figure 4 As shown in the figure, the motor state before and after injection always moves along the constant torque curve.

[0076] The three motor voltage equations established before and after the two signal injections are as follows:

[0077]

[0078] In the formula, u q0 is the q-axis voltage before the DC bias voltage injection, u q1 is the q-axis voltage after the first group of DC bias voltage injection, u q2 is the q-axis voltage after the second group of DC bias voltage injection, i q0 is the q-axis current before the DC bias voltage injection, i q1 is the q-axis current after the first group of DC bias voltage injection, i q2 is the q-axis current after the second group of DC bias voltage injection, ω e is the motor speed, i d0 is the d-axis current before the DC bias voltage injection, i d1 is the d-axis current after the first group of DC bias voltage injection, i d2 is the d-axis current after the second group of DC bias voltage injection.

[0079] Since the above voltage equation still contains the flux linkage term, in order to preferentially realize the solution of inductance, it is necessary to first ensure that the motor reaches a steady state during each signal injection process, and then real-time sampling of the voltage and current in the voltage equation. In step two, by combining the voltage equations before and after the signal injection, the voltage equation difference equation can be obtained, that is, two motor voltage equations that eliminate the flux linkage term are as follows:

[0080]

[0081] In the formula, u q01 is the difference between u q1 and u q0 , u q12 is the difference between u q2 and u q1 , i q01 is the difference between i q1 and i q0 , i q12 is the difference between i q2 and i q1 , i d01 is the difference between id1 the difference between i d0 and i d12 ; d2 the difference between i d1 and i

[0082] The elimination of the flux linkage term in the voltage equation is achieved by the difference operation, and the solution of L d and L dq is achieved.

[0083] In combination with the solution formula of the motor inductance, the steady-state motor voltage and current information before and after the signal injection of each group is sampled when each group of signal injection reaches the steady state, and the solution of the resistance is directly achieved based on the online sampling data.

[0084] In step two, to ensure the accuracy and robustness of the inductance identification, the solution of the motor d-axis self-inductance and mutual inductance is achieved based on the RLS algorithm (recursive least square method).

[0085] The method for solving the motor d-axis self-inductance L d and the motor dq-axis mutual inductance L dq includes:

[0086]

[0087] In the formula, e is the error matrix of the least square method algorithm, y is the output matrix of the least square method algorithm, λ is the feedback matrix of the least square method algorithm, and ρ is the parameter matrix of the least square method algorithm.

[0088] Based on RLS, the d-axis self-inductance and dq-axis mutual inductance identification with high robustness and high accuracy can be achieved. Furthermore, in combination with the identified inductance information, the d-axis voltage equation is used to achieve the identification of the motor flux linkage.

[0089] In step three, when the motor is running online, cross-coupling phenomenon occurs between the dq axes, resulting in q-axis armature reaction, and further causing the motor magnetic field to deflect. Since motor control is usually achieved by the dq-axis voltage equation, the dq-axis voltage equation needs to be modified to consider the influence of the actual cross-coupling phenomenon. The modified dq-axis voltage equation considering cross-coupling is:

[0090]

[0091] The above formula takes into account the motor dq-axis mutual inductance term L dq ;

[0092] In the formula, u d is the d-axis voltage of the motor under online stable working conditions, u q is the q-axis voltage of the motor under online stable working conditions, i d is the d-axis current of the motor under online stable working conditions, and iq L is the q-axis current of the motor under stable online operating conditions. q The self-inductance of the q-axis of the motor.

[0093] u d u q i d i q and ω e Both can be obtained directly through the controller or position sensor. s L d L q L dq ψ f Electrical parameters such as flux linkage require identification based on specific algorithms. The flux linkage identification process is as follows: Figure 2 As shown.

[0094] In step three, combined with Figure 1 As shown, if the motor cross-coupling effect is not considered, only self-inductance exists in the inductance matrix. Considering the cross-coupling effect, the motor's dq axis experiences an offset angle θ. r This results in the mutual inductance term being non-zero. Therefore, this term needs to be considered during the flux linkage identification process. Thus, the motor permanent magnet flux linkage identification formula based on the voltage equation is:

[0095]

[0096] In summary, the overall algorithm flowchart of this invention is as follows: Figure 5 As shown. Figure 6 Based on the full-condition flux linkage identification results of the method of the present invention, it can be determined that the method of the present invention can achieve stable and accurate flux linkage identification under different operating conditions, which proves the effectiveness and feasibility of the method of the present invention.

[0097] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for online identification of permanent magnet flux linkage in a permanent magnet synchronous motor considering cross-coupling effects, characterized in that... include, Step 1: Under stable online operating conditions, inject a sinusoidal current signal into the dq axis of the motor to achieve three-phase DC signal injection; calculate the stator resistance of the motor based on the three-phase voltage and current signals before and after the sinusoidal current signal injection. Step 2: Inject two sets of DC bias voltages into the d-axis of the motor through the current loop, and adjust the q-axis current through the PI controller to keep the motor working state stable; collect the dq-axis voltage and dq-axis current before the DC bias voltage injection, after the first set of DC bias voltage injection, and after the second set of DC bias voltage injection, and establish three motor voltage equations; Subtracting the second and first motor voltage equations, and subtracting the third and second motor voltage equations, yields two motor voltage difference equations with flux linkage terms eliminated. Then, a recursive least squares algorithm is used to solve these two motor voltage equations with flux linkage terms eliminated, yielding the motor's d-axis self-inductance L. d Mutual inductance L between the motor dq axis and dq ; Step 3: Establish the dq-axis voltage equations considering cross-coupling, based on the motor stator resistance and the motor's d-axis self-inductance L. d Mutual inductance L between the motor dq axis and dq The permanent magnet flux linkage of the motor is calculated.

2. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 1, characterized in that, In step one, based on the fact that the three-phase resistance, dq-axis resistance, and stator resistance of the motor are equal, the three-phase resistance, dq-axis resistance, and stator resistance of the motor are uniformly represented as R. s ; Establish the three-phase voltage equations for the permanent magnet motor: In the formula u a Let u be the voltage of phase A. b For phase B voltage, u c For phase C voltage, i a Let i be the phase A current. b Let i be the phase B current. c Let C be the phase current, p be the differential operator, and L be the phase current. aa For the self-inductance of stator phase A winding, L bb For the self-inductance of the stator B-phase winding, L cc For the self-inductance of the stator C-phase winding, M ab =M ba For the mutual inductance of the stator AB phase windings, M ac =M ca For the mutual inductance of the stator AC phase windings, M bc =M cb For the mutual inductance of the stator BC phase windings, ψ f For the permanent magnet flux linkage of the motor, θ e This is the rotor position angle.

3. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 2, characterized in that, In step one, after a sinusoidal current signal is injected into the dq axis of the motor, the corresponding voltage equation is: In the formula Δu a The voltage difference Δu between phase A and phase A before and after the sinusoidal current signal is injected. b The voltage difference Δu between phase B and the phase B before and after the sinusoidal current signal is injected. c The voltage difference Δi between phase C and the phase C before and after the sinusoidal current signal is injected. a The difference in phase A current before and after the injection of a sinusoidal current signal is Δi. b The difference in B-phase current before and after the injection of a sinusoidal current signal is Δi. c The difference in C-phase current before and after the sinusoidal current signal is injected.

4. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 3, characterized in that, The sinusoidal current signal injected into the dq axis of the motor is set as follows: In the formula Δi d_inj For the current signal injected along the d-axis, Δi q_inj For the current signal injected into the q-axis, I dc The amplitude of the sinusoidal current signal; For the current signal Δi injected into the dq axis d_inj and Δi q_inj By performing a coordinate transformation, we obtain the expression for the injected current in the three-phase coordinate system: For phase A, the stator resistance R of the motor is... s for: R s =Δu a / Δi a 。 5. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 4, characterized in that, In step two, the three motor voltage equations are established as follows: In the formula u q0 The q-axis voltage before DC bias voltage injection, u q1 The q-axis voltage after the first set of DC bias voltages is injected, u q2 i is the q-axis voltage after the second set of DC bias voltages is injected. q0 i is the q-axis current before DC bias voltage injection. q1 i is the q-axis current after the first set of DC bias voltages is injected. q2 The q-axis current after the second set of DC bias voltage injection, ω e i represents the motor speed. d0 i is the d-axis current before DC bias voltage injection. d1 i is the d-axis current after the first set of DC bias voltages is injected. d2 This refers to the d-axis current after the second set of DC bias voltages is injected.

6. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 5, characterized in that, In step two, the two motor voltage equations with flux linkage terms eliminated are: In the formula u q01 For u q1 with u q0 The difference, u q12 For u q2 with u q1 The difference, i q01 For i q1 with i q0 The difference, i q12 For i q2 with i q1 The difference, i d01 For i d1 with i d0 The difference, i d12 For i d2 with i d1 The difference.

7. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 6, characterized in that, In step two, the recursive least squares algorithm is used to solve for the self-inductance L of the motor's d-axis. d Mutual inductance L between the motor dq axis and dq The methods include: In the formula, e is the least squares algorithm error matrix, y is the least squares algorithm output matrix, λ is the least squares algorithm feedback matrix, and ρ is the least squares algorithm parameter matrix.

8. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 7, characterized in that, In step three, considering the cross-coupling, the dq-axis voltage equation is: In the formula u d U represents the d-axis voltage of the motor under stable online operating conditions. q i is the q-axis voltage of the motor under stable online operating conditions. d For the d-axis current of the motor under stable online operating conditions, i q L is the q-axis current of the motor under stable online operating conditions. q The self-inductance of the q-axis of the motor.

9. The online identification method for permanent magnet flux linkage of a permanent magnet synchronous motor considering cross-coupling effect according to claim 8, characterized in that, In step three, the formula for calculating the permanent magnet flux linkage of the motor is:

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