Model predictive current control method for induction motor based on generalized flux error and closed-loop flux-weakening strategy

Abstract

The model predictive current control method for induction motor based on generalized flux error and closed-loop flux-weakening strategy belongs to the field of induction motor speed regulation control.The method solves the problems that the existing control method cannot simultaneously meet the conditions of not needing to add an additional flux-weakening weight factor in the value function,not depending on motor parameters,being able to perform closed-loop control and not causing the current following error to increase under single-vector model predictive current control.The method specifically comprises the following steps: step one, defining a generalized flux vector reference value and a generalized flux prediction value, and obtaining the relationship between a basic generalized flux vector and a basic voltage vector according to the generalized flux prediction value; step two, obtaining a value function of single-vector model predictive current control for the induction motor according to the result of step one; and step three, obtaining an optimal voltage vector according to the value function, and generating a flux-weakening current component to perform compensation according to the basic generalized flux vector corresponding to the optimal voltage vector.The method can be applied to model predictive current control for the induction motor.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of induction motor speed regulation control, and particularly relates to an induction motor model predictive current control method based on generalized flux linkage error and closed-loop field weakening strategy. BACKGROUND

[0002] Single vector model predictive current control (SV-MPCC) has been widely concerned due to its high transient performance and small calculation amount. The introduction of field weakening control strategy into the MPC strategy is an important problem for high-speed operation of traction motors. Compared with vector control, the control object of SV-MPCC is no longer the fundamental current component, but the reference current vector prediction value directly generates the inverter switching state. Therefore, SV-MPCC can only obtain the fundamental voltage amplitude of the actual output according to the switching state to construct the voltage closed-loop field weakening structure. However, due to the inverter voltage limit, the actual fundamental voltage in the field weakening region is often smaller than the expected fundamental voltage, which means that compared with the expected fundamental voltage, the actual fundamental voltage as feedback cannot reflect the true voltage saturation condition. However, the expected fundamental voltage cannot be directly obtained in the SV-MPCC system, so that the existing closed-loop field weakening strategy has a dynamic problem. Therefore, the existing SV-MPCC system mostly adopts a field current open-loop calculation field weakening strategy based on the motor model, but has the problems of poor robustness and low modulation ratio control precision.

[0003] In order to realize the flux weakening operation in the MPC strategy, some scholars have proposed some solutions, but most of these methods belong to open-loop strategy, and the load capacity and the ability to further improve the motor speed are not strong. For example, the reference torque and flux size are set to be proportional to the inverse of the rotor speed in the document (Predictive Torque Control of Induction Motor Sensorless Drive Fed by a 3L-NPC Inverter). The document (IPMSM Model Predictive Control in Flux-Weakening Operation Using an Improved Algorithm) proposes a linear flux weakening method of voltage-current based on the MPCC algorithm, which has strong robustness to the change of motor parameters. The document (Low Switching Frequency Model Predictive Control of Three-Level Inverter-Fed IM Drives With Speed-Sensorless and Field-Weakening Operations) adjusts the torque and stator flux reference value online to improve the torque capacity during the FW operation. However, some of the existing methods only consider the voltage limit and ignore the change of the stator current. Some methods produce unstable voltage when the magnetic field is weakened, which reduces the control performance. Or due to the limitation of switching loss and neutral point voltage error, more weight factors are introduced in the value function. The single vector model predictive control directly generates the switching state according to the following of the control variable, and cannot obtain the voltage feedback information. The mature flux weakening control strategy based on voltage closed loop in the vector control strategy cannot be directly applied. At present, there is no good method that can simultaneously satisfy the following requirements in the SV-MPCC system: 1) no need to add additional flux weakening weight factor in the value function; 2) not dependent on motor parameters; 3) can be closed-loop controlled; 4) will not cause the increase of current following error in single vector model predictive current control. Therefore, it is urgent to develop a new control method that can meet the above requirements and improve the universality and practicability of the method. SUMMARY

[0004] The purpose of the present application is to solve the problem that the existing control method cannot simultaneously satisfy the requirements of not adding additional flux weakening weight factor in the value function, not being dependent on motor parameters, being able to be closed-loop controlled, and not causing the increase of current following error in single vector model predictive current control. Therefore, a model predictive current control method for induction motor based on generalized flux error and closed-loop flux weakening strategy is proposed.

[0005] The technical scheme adopted by the present application to solve the above technical problems is:

[0006] A model predictive current control method for induction motor based on generalized flux error and closed-loop flux-weakening strategy, the method specifically comprises the following steps:

[0007] Step one, define the generalized flux vector reference value According to the definition of the generalized flux prediction value in the single vector model predictive current control of the induction motor, the relationship between the basic generalized flux vector and the basic voltage vector is obtained according to the generalized flux prediction value;

[0008] Step two, according to the generalized flux vector reference value The generalized flux prediction value and the relationship between the basic generalized flux vector and the basic voltage vector are obtained, and the value function of the single vector model predictive current control of the induction motor is obtained;

[0009] Step three, the optimal voltage vector is obtained according to the value function in step two The flux-weakening controller generates a flux-weakening current component i According to the optimal voltage vector sdFW , and the flux-weakening current component i sdFW is used to compensate the excitation current;

[0010] And the optimal voltage vector is used for model predictive current control.

[0011] Further, the generalized flux vector reference value is:

[0012]

[0013] Wherein, represents the reference current, and sigma is the leakage factor, L s is the stator inductance.

[0014] Further, in step one, according to the definition of the generalized flux prediction value in the single vector model predictive current control of the induction motor, the relationship between the basic generalized flux vector and the basic voltage vector is obtained according to the generalized flux prediction value; the specific process is:

[0015] Step one, the discrete current expression in the single vector model predictive current control of the induction motor is:

[0016]

[0017] Wherein, represents the current in the single vector model predictive current control of the induction motor at k+1 time, represents the current in the single vector model predictive current control of the induction motor at k+2 time, T sis the sampling period, R s is the stator resistance, L m is the mutual inductance, L r is the rotor inductance, R r is the rotor resistance, L s is the stator inductance, T r is the rotor time constant, ω r is the mechanical speed, σ is the leakage factor, j represents the imaginary unit, represents the predicted value of the rotor flux linkage;

[0018] The generalized flux linkage prediction value ψ s1 is defined as:

[0019]

[0020] The generalized flux linkage initial value ψ s0 is set as:

[0021]

[0022] The transformed discrete current expression is:

[0023]

[0024] The basic generalized flux linkage vector and the basic voltage vector are related as:

[0025]

[0026] wherein,

[0027] Further, the rotor time constant is:

[0028] T r = L r / R r .

[0029] Further, the leakage factor σ is:

[0030]

[0031] Further, the specific process of step two is:

[0032] The value function J is defined as:

[0033]

[0034] wherein, |·| represents taking the absolute value;

[0035] According to ψ s1 and Transform the value function J into:

[0036]

[0037] in, Indicates the error value.

[0038] Furthermore, the specific process of step three is as follows:

[0039] Step 31: Calculate the basic generalized flux linkage vector corresponding to each voltage vector:

[0040] Δψ n =T s u n (4)

[0041] Where, Δψ n u represents the fundamental generalized flux linkage vector corresponding to the nth voltage vector. n This represents the nth voltage vector, where n = 0, 1, ..., 7;

[0042] Step 3.2: From the basic generalized flux linkage vectors corresponding to each voltage vector, select the basic generalized flux linkage vector that minimizes the value function.

[0043] Step 33, according to Calculate the optimal voltage vector Using the optimal voltage vector Generate the switching pulse signal for the inverter;

[0044] Based on the selected basic generalized flux linkage vector Generating a weak magnetic current component i sdFW Then utilize the weak magnetic current component i sdFW Compensate the excitation current.

[0045] Furthermore, the aforementioned according to Calculate the optimal voltage vector Specifically:

[0046]

[0047] Furthermore, the field weakening controller is based on the optimal voltage vector The corresponding basic generalized flux linkage vector generates the weak magnetic current component i sdFW Specifically:

[0048] 2×3 0.5 U dc T s / 9 is used as the setpoint for the PI controller in field weakening control, which will determine the optimal voltage vector. corresponding as the feedback value of the PI controller in the field weakening control;

[0049] When , the field weakening control generates a field weakening current component i sdFW :

[0050]

[0051] wherein K p represents the proportional parameter of the PI controller, K i represents the integral parameter of the PI controller, s represents a complex frequency domain variable, U dc represents the DC bus voltage;

[0052] When , the field weakening current component generated by the field weakening control is 0.

[0053] The beneficial effects of the present application are:

[0054] 1. The field weakening controller designed in the present application takes the generalized flux linkage error as the control variable to perform closed-loop field weakening control, thereby expanding the speed range of the induction motor system and improving the load carrying capacity of the system;

[0055] 2. Compared with the traditional field weakening control method based on the motor model, the field weakening control strategy of the present application does not introduce motor parameters, so it does not need to rely on motor parameters and has high robustness;

[0056] 3. The method of the present application compensates the current in real time through a closed-loop control strategy, that is, when the change in speed causes the expected generalized flux linkage error to change, the real-time compensation of the exciting current in the field weakening zone is realized through the feedback of the generalized flux linkage error, so the present application will not cause the increase of the current following error under the SV-MPCC control strategy;

[0057] 4. The present application can be realized based on the traditional value function without adding an additional field weakening weight factor in the value function. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is the system control block diagram of the field weakening control strategy based on the generalized flux linkage error;

[0059] The generalized flux linkage given value is obtained from the given current, and the generalized flux linkage initial value ψ s0 is obtained from the feedback current, and the difference between the two is the expected generalized flux linkage error in the current period According to , the basic generalized flux linkage vector Δψ s0～7 corresponding to the output different basic voltage vector is obtained, and finally one of Δψ s0～7 is selected and The closest vector is used as the output for the current cycle. Depend on It can be seen that, The basic voltage vector is used as the output for this cycle, and the switching pulse signal of the inverter is generated based on this basic voltage vector. Simultaneously, the generalized flux linkage error is considered. With the basic generalized magnetic flux vector The relationship, to obtain The maximum value is 2×3 0.5 U dc T s / 9. Using 2×3 0.5 U dc T s / 9 is the setpoint for the field weakening controller. The feedback value is used to obtain the field weakening current component i through a PI controller. sdFW This enables real-time compensation of the excitation current in the field weakening zone, thus completing closed-loop field weakening control.

[0060] Figure 2 It is the spatial flux linkage vector plane and the basic flux linkage vector;

[0061] Figure 3 This is a schematic diagram of the change in magnetic flux linkage vector in the weak magnetic region;

[0062] Figure 4a This is a performance diagram of the motor without field weakening when the initial speed is given as the rated speed and a step speed of 1.6 times the rated speed (2400 rpm) is applied in 0.2 seconds.

[0063] In the diagram, ω r i represents rotational speed sd i represents the d-axis component of the stator current. sq This represents the q-axis component of the stator current, and M represents the modulation ratio.

[0064] Figure 4b This is a schematic diagram of the performance of the open-loop field weakening method calculated based on the motor model when the initial speed of the motor is given as the rated speed and a step speed of 1.6 times the rated speed (2400 rpm) is applied in 0.2 seconds.

[0065] Figure 4c The diagram shows the performance of the closed-loop field weakening method proposed in this invention when the initial speed of the motor is given as the rated speed and a step speed of 1.6 times the rated speed (2400 rpm) is added in 0.2 seconds to accelerate to the field weakening region.

[0066] Figure 5a This is a schematic diagram of the load-carrying capacity of the system in the weak magnetic region before incorporating the method proposed in this invention;

[0067] Figure 5bis a schematic diagram of the load capacity of the system in the field weakening region after the method proposed in the application is added;

[0068] Figure 6a is a schematic diagram of the control performance of the closed-loop field weakening method proposed in the application when the stator inductance parameter deviates from the actual value;

[0069] Figure 6b is a schematic diagram of the control performance of the traditional model-based field weakening method when the stator inductance parameter deviates from the actual value;

[0070] Figure 7a is a test result diagram of the step acceleration capability of the field weakening method proposed in the application;

[0071] Figure 7b is a test result diagram of the field weakening region reversal capability of the field weakening method proposed in the application. DETAILED DESCRIPTION

[0072] Specific implementation one: combined with Figure 1 This embodiment is described. The induction motor model predictive current control method based on generalized flux linkage error and closed-loop field weakening strategy described in this embodiment specifically includes the following steps:

[0073] Step one, define the generalized flux linkage vector reference value According to the current in the single-vector model predictive current control (SV-MPCC) of the induction motor, define the generalized flux linkage prediction value, and obtain the relationship between the basic generalized flux linkage vector and the basic voltage vector according to the generalized flux linkage prediction value;

[0074] Step two, obtain the value function of the single-vector model predictive current control of the induction motor according to the generalized flux linkage vector reference value , the generalized flux linkage prediction value, and the relationship between the basic generalized flux linkage vector and the basic voltage vector;

[0075] Step three, obtain the optimal voltage vector according to the value function in step two The field weakening controller generates a field weakening current component i corresponding to the optimal voltage vector sdFW , and then compensates the field current by using the field weakening current component i sdFW ;

[0076] And perform model predictive current control (i.e., complete inverter control according to the optimal voltage vector) by using the optimal voltage vector .

[0077] Specific implementation two: the difference between this embodiment and specific implementation one is that the generalized flux linkage vector reference value is:

[0078]

[0079] in, The reference current is represented by σ, the leakage inductance factor is L. s It is the stator inductor.

[0080] The other steps and parameters are the same as in Specific Implementation Method 1.

[0081] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that, in step one, the generalized flux linkage prediction value is defined based on the current in the induction motor single vector model predicted current control (SV-MPCC), and the relationship between the basic generalized flux linkage vector and the basic voltage vector is obtained based on the generalized flux linkage prediction value; the specific process is as follows:

[0082] Step 11: The discrete current expression in the single-vector model predictive current control of the induction motor is:

[0083]

[0084] in, This represents the current in the current control predicted by the single-vector model of the induction motor at time k+1. T represents the current in the single-vector model predictive current control of the induction motor at time k+2. s R is the sampling period. s L is the stator resistance. m For mutual inductance, L r R is the rotor inductance. r L is the rotor resistance. s For stator inductance, T r ω is the rotor time constant. r Where σ is the mechanical speed, σ is the leakage inductance factor, and j represents the imaginary unit. This represents the predicted value of the rotor flux linkage;

[0085] Define the generalized flux linkage prediction value ψ s1 :

[0086]

[0087] And set the initial value ψ of the generalized magnetic flux. s0 for:

[0088]

[0089] The transformed discrete current expression is:

[0090]

[0091] The basic generalized magnetic flux vector The relationship with the fundamental voltage vector is as follows:

[0092]

[0093] in,

[0094] Other steps and parameters are the same as in specific implementation method one or two.

[0095] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the rotor time constant is:

[0096] T r =L r / R r

[0097] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0098] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the leakage inductance factor σ is:

[0099]

[0100] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0101] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the specific process of step two is as follows:

[0102] In the predictive current control of a classic induction motor using a single-vector model, the value function J is defined as:

[0103]

[0104] Where |·| represents taking the absolute value;

[0105] Then according to ψ s1 and Transform the value function J into:

[0106]

[0107] in, Indicates the error value.

[0108] The other steps and parameters are the same as those in one of the specific implementation methods one to five.

[0109] In this embodiment, the defined generalized flux linkage is substituted into the classical value function in the single-vector model predictive current control of the induction motor to obtain a new value function, without the need to add an additional field weakening weight factor to the value function.

[0110] Specific implementation seven: different from one of the specific implementations one to six, the specific process of the step three is:

[0111] Step three one, respectively calculate the basic generalized flux linkage vector corresponding to each voltage vector:

[0112] Δψ n = T s u n (4)

[0113] Wherein, Δψ n represents the basic generalized flux linkage vector corresponding to the nth voltage vector, u n represents the nth voltage vector, n = 0, 1,..., 7;

[0114] Step three two, from the basic generalized flux linkage vector corresponding to each voltage vector, select the basic generalized flux linkage vector that makes the value function value minimum (i.e. from Δψ n , n = 0, 1,..., 7);

[0115] Step three three, according to Calculate the optimal voltage vector Use the optimal voltage vector To generate the switching pulse signal of the inverter, and control the inverter;

[0116] According to the selected basic generalized flux linkage vector (i.e. the basic generalized flux linkage vector corresponding to the optimal voltage vector Generate the field weakening current component i sdFW , and then use the field weakening current component i sdFW To compensate the excitation current.

[0117] The other steps and parameters are the same as one of the specific implementations one to six.

[0118] In this specific implementation, by selecting the basic generalized flux linkage vector that makes the value function value minimum, the tracking error of the stator current vector can be minimized.

[0119] Specific implementation eight: different from one of the specific implementations one to seven, the specific implementation of calculating the optimal voltage vector According to Specifically:

[0120]

[0121] The other steps and parameters are the same as one of the specific implementations one to seven.

[0122] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the field weakening controller is based on the optimal voltage vector. The corresponding basic generalized flux linkage vector generates the weak magnetic current component i sdFW Specifically:

[0123] 2×3 0.5 U dc T s / 9 is used as the setpoint for the PI controller in field weakening control, which will determine the optimal voltage vector. corresponding As the feedback value of the PI controller in field weakening control;

[0124] when At that time, the field weakening control generates a field weakening current component i. sdFW :

[0125]

[0126] Among them, K p K represents the proportional parameter of the PI controller. i The integral parameter of the PI controller is represented by s, which represents the complex frequency domain variable, and U is the integral parameter of the PI controller. dc Indicates the DC bus voltage;

[0127] when At that time, the magnetic weakening current component generated by the magnetic weakening control is 0.

[0128] The other steps and parameters are the same as those in one of the specific implementation methods one to eight.

[0129] like Figure 2 and Figure 3 As shown, This represents the length of line segment OA. It is derived from the fundamental generalized magnetic flux linkage vector Δψ. s1 , Δψ s2 and Δψ s0 / Δψ s7 In the triangle formed, for any generalized flux linkage error whose endpoint is not at point A, Generalized flux linkage error The difference between the value and the four basic generalized flux linkage vectors must be less than 1. The situation exists. Therefore, this invention uses the length of line segment OA as the setpoint for the PI controller in the field weakening control. The field weakening current component i is obtained through the PI controller. sdFW The output of the field weakening controller is limited to [-2×3]. 0.5 U dc T s Within the range of [9, 0], and using this as the compensation value to construct a magnetic weakening closed loop, the magnetic weakening zone can be used to compensate the excitation current in real time.

[0130] The effectiveness of the method proposed in this invention is verified below using experimental results shown in the attached figures:

[0131] Figure 4a , Figure 4b and Figure 4c The figures show a performance comparison of accelerating to the field weakening region using the non-field weakening method, the open-loop field weakening method based on the motor model, and the closed-loop field weakening method proposed in this invention. The initial motor speed is given as the rated speed, and a step speed of 1.6 times the rated speed (2400 rpm) is added in 0.2 seconds. It can be seen that the field weakening strategies of the traditional method and the method proposed in this invention can improve the operating range of the motor, but the acceleration time of the method proposed in this invention is faster and the voltage saturation duration is shorter.

[0132] Figure 5a and Figure 5b This is a comparison of the system's load-carrying capacity in the weak magnetic region before and after incorporating the method proposed in this invention. The motor speed is 1650 rpm, and the load suddenly increases from 35% of the rated torque to 70% of the rated torque in 0.2 seconds; this means that the addition of the method proposed in this invention improves the system's load-carrying capacity in the weak magnetic region.

[0133] Figure 6a and Figure 6b The comparison focuses on the control performance of the proposed closed-loop field weakening method and the traditional model-based field weakening method when the stator inductance parameters deviate from their actual values. Specifically, it compares the performance of L in the field weakening region (1800 rpm). s Starting from 1.0s, it changes to 1.2 times the actual value (1.2L). s At 3.0s, it begins to change to 0.8 times the actual value (0.8L). s ), and returns to the initial value (L) after 5.0s. s The experimental results show that when the parameters change, the rotational speed, current and voltage of the closed-loop field weakening method proposed in this invention do not fluctuate significantly. Therefore, the field weakening method proposed in this invention is much less dependent on the parameters than the traditional method and has better parameter robustness.

[0134] Figure 7a and Figure 7b This test examines the stepwise acceleration and reversal capability of the magnetic weakening method proposed in this invention. During acceleration, the rotational speed increases from the base speed, progressively increasing by 1.2 times, 1.4 times, and 1.6 times the rated speed. The initial speed for reversal is 1.2 times the rated speed (1800 rpm), and the speed reverses to -1.2 times the rated speed within 0.2 seconds. This demonstrates that the magnetic weakening method based on error voltage proposed in this invention can simultaneously meet the requirements of acceleration and reversal within the magnetic weakening region.

[0135] The above calculation examples of the present application are only used to illustrate the calculation model and calculation process of the present application, and are not used to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art, and all the embodiments cannot be exhausted here. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.

Claims

1. A model predictive current control method for induction machines based on generalized flux linkage error and closed-loop flux-weakening strategy, characterized in that, The method specifically comprises the following steps: Step one, define the generalized flux linkage vector reference value , define the generalized flux linkage prediction value according to the current in the current control of the induction motor single vector model, and obtain the relationship between the basic generalized flux linkage vector and the basic voltage vector according to the generalized flux linkage prediction value; Step two, according to the generalized flux linkage vector reference value , the generalized flux linkage prediction value and the relationship between the basic generalized flux linkage vector and the basic voltage vector, the value function of the induction motor single vector model prediction current control is obtained; Step three, obtaining the optimal voltage vector according to the value function in step two The optimal voltage vector is obtained by the field weakening controller The corresponding basic generalized flux linkage vector generates a field weakening current component i sdFW The field weakening current component i sdFW is used to compensate for the excitation current; the specific process is as follows: Step three one, respectively calculate each voltage vector corresponding to the basic generalized flux linkage vector: (4) wherein, represents the basic generalized flux vector corresponding to the th voltage vector, represents the basic generalized flux vector corresponding to the th voltage vector, ; T s is the sampling period; Step three two, from the basic generalized flux vector corresponding to each voltage vector, select the basic generalized flux vector that makes the value function value minimum ; Step three, according to calculating the optimal voltage vector , using the optimal voltage vector generating a switching pulse signal of the inverter; According to the selected basic generalized flux linkage vector Generating a field-weakening current component i sdFW Reusing the field-weakening current component i sdFW Compensating the field current; and using the optimal voltage vector model predictive current control.

2. The model predictive current control method for induction machines based on generalized flux error and closed-loop flux-weakening strategy according to claim 1, characterized in that, the generalized flux linkage vector reference value is: (1) wherein, represents the reference current, σ is the leakage factor, L s is the stator inductance.

3. The model predictive current control method for induction machines based on generalized flux error and closed-loop flux-weakening strategy according to claim 2, characterized in that, In the step one, the generalized flux linkage prediction value is defined according to the current in the induction motor single vector model prediction current control, and the relationship between the basic generalized flux linkage vector and the basic voltage vector is obtained according to the generalized flux linkage prediction value; the specific process is: Step one, the discrete current expression in the induction motor single vector model prediction current control is: wherein denotes the current in the induction machine single vector model predictive current control at time instant denotes the current in the induction machine single vector model predictive current control at time instant R s is the stator resistance, L m is the mutual inductance, L r is the rotor inductance, R r is the rotor resistance, L s is the stator inductance, T r is the rotor time constant, ω r is the mechanical speed, σ is the leakage factor, denotes the imaginary unit, denotes the predicted value of the rotor flux; Definition of generalized flux prediction value : and set the initial value of the generalized magnetic flux is: (2) Then the discrete current expression after deformation is: the basic generalized flux vector has the following relationship with the basic voltage vector: wherein .

4. The model predictive current control method for induction machines based on generalized flux error and closed-loop flux-weakening strategy according to claim 3, characterized in that, The rotor time constant is: T r =L r / R r .

5. The model predictive current control method for induction machines based on generalized flux error and closed-loop flux-weakening strategy according to claim 4, characterized in that, The leakage inductance factor sigma is: 。 6. The model predictive current control method of an induction motor based on generalized flux error and closed-loop flux-weakening strategy according to claim 5, characterized in that, The specific process of the step two is: Defining the value function is: wherein denotes taking the absolute value; Then according to , and value function Convert to: (3) wherein represents an error value, .

7. The model predictive current control method of induction machines based on generalized flux error and closed-loop flux-weakening strategy according to claim 6, characterized in that, The method comprises the following steps: Calculating the optimal voltage vector Specifically, 。 8. The model predictive current control method of induction machines based on generalized flux error and closed-loop flux-weakening strategy according to claim 7, characterized in that, The field-weakening controller generates the field-weakening current component i The corresponding basic generalized flux linkage vector generates the field-weakening current component i sdFW ; Specifically: 2x3 0.5 U dc T s / 9 as a given value of the PI controller in the field weakening control, the optimal voltage vector corresponding as a feedback value of the PI controller in the field weakening control; When field control generates a field current component i sdFW : where K p represents a proportional parameter of the PI controller, K i represents an integral parameter of the PI controller, represents a complex frequency domain variable, U dc represents a DC bus voltage; When The component of the field-weakening current generated by the field-weakening control is 0.

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