A self-learning method for the stator saturation inductance value of an asynchronous motor

Abstract

The invention discloses a self-learning method for the stator saturation inductance value of an asynchronous motor, comprising: changing the stator flux given value under vector control; a frequency converter controls the asynchronous motor to operate in a vector control mode under the stator flux given value; calculating the active power and reactive power of the asynchronous motor based on the three-phase stator current and stator voltage of the asynchronous motor output under the vector control mode; calculating the stator saturation inductance based on the active power and reactive power; judging whether the stator saturation inductance converges, and if so, taking the stator saturation inductance as the initial value, otherwise continuing vector control. The self-learning method of the invention does not need to separate the motor from the actual load machinery, and is suitable for low-speed heavy load and high-speed heavy load.

Description

Technical Field

[0001] The invention relates to the technical field of asynchronous motor variable frequency drive, and more particularly to a self-learning method for the stator saturation inductance value of an asynchronous motor. Background Art

[0002] At present, in the application field of asynchronous motor variable frequency drive (such as the hoisting mechanism of crane, the cutter head mechanism of shield machine, the traction mechanism of rail vehicle, etc.), in order to achieve better control effect, such as improving the response capability to load changes and obtaining better low-speed or high-speed load capacity, it is necessary to adopt closed-loop vector control with encoder feedback or open-loop vector control without encoder feedback to achieve accurate control of the excitation component and torque component of the motor. The premise of all vector control is to accurately obtain the relevant motor parameters in the vector control model, such as stator and rotor resistance, total leakage inductance, saturation inductance, etc. These parameters are usually not provided by motor manufacturers in public information, such as motor nameplate or manual.

[0003] The methods for obtaining these parameters can be divided into two categories according to whether external devices are used. The first category is to use the data collected by the hardware of the frequency converter that drives the asynchronous motor to calculate the motor parameters, without introducing external devices that are not used in actual applications; the second category is to use hardware other than the frequency converter that drives the asynchronous motor to collect data to calculate the motor parameters, such as additional voltmeters, ammeters, dynamometers and other equipment, such as patents CN106452241A, CN106452258A, and CN1157845C. Usually, in the application of asynchronous motor variable frequency drive, the frequency converter, motor and load equipment are all connected on site. The second method is generally not feasible for on-site implementation. Even if it can be implemented, the cost is huge. Therefore, the first method is widely used. In situations where high-performance vector control of asynchronous motors is required, the frequency converter that drives asynchronous motors needs to have the function of calculating asynchronous motor parameters, hereinafter referred to as self-learning function, and the process of calculating asynchronous motor parameters is called self-learning.

[0004] In addition, since the parameters of the asynchronous motor will change with the operating state of the motor, for example, the stator resistance and rotor resistance will change with the temperature change of the motor winding, there are various technical solutions for online parameter identification in response to the parameter changes during this operation process, such as the patent with authorization announcement number CN104201962B. This solution is different from the parameters targeted by self-learning. Self-learning is generally performed before the first operation of the motor, and its purpose is to find the initial values ​​of various motor parameters. Online parameter identification is required every time the motor runs. However, if the initial value of the parameter of the motor self-learning has a large error with the true value, the basis of the online parameter identification is unreliable, and its accuracy will be greatly affected, which in turn affects the control effect.

[0005] For the self-learning function of the frequency converter, self-learning of parameters such as stator resistance, rotor resistance, total stator leakage inductance, and total rotor leakage inductance can be completed when the motor is in a stationary state. However, for the motor stator saturation inductance parameter, there are both self-learning when the motor is in a stationary state and self-learning when the motor is in a rotating state.

[0006] The method of self-learning when the motor is in a stationary state is to let the motor be in a stationary state, inject single-phase DC or AC current into the motor, and then collect relevant data to calculate the saturation inductance value of the motor, such as the patents with authorization announcement numbers CN101944878B, CN102291080B, CN103208965B, and application publication numbers CN106842018A, CN108183647A. This type of method often performs self-learning of the motor mutual inductance value based on the static equivalent circuit of the asynchronous motor, such as Figure 1 As shown, when the motor is stationary and the rotor speed is 0, then jω r λ r =0, due to the mutual inductance value L m Generally much larger than the total rotor leakage inductance L ls , in order to calculate the mutual inductance L m , a very low frequency current (e.g. below 2 Hz) must be passed through the circuit to convert the equivalent circuit into Figure 2 In the form of , the mutual inductance branch can be effectively involved in the calculation. In the application of inverter-driven motors, the current with very low frequency is difficult to control accurately under the influence of the inverter IGBT dead zone and conduction voltage drop, so there is a problem of inaccurate calculation. In addition, most of these patents do not take into account the saturation characteristics of the mutual inductance value, and only calculate the mutual inductance value under the rated flux. Therefore, the parameters calculated by this method are prone to reduced control effect or even loss of control, especially when encountering low-speed heavy loads that require an increase in the flux given, and high-speed heavy loads that require a decrease in the flux given.

[0007] The method of self-learning when the motor is rotating usually requires the motor to be in a no-load state and run at a high speed (for example, 40-50Hz). By changing the given voltage, the degree of saturation of the motor's magnetic field is changed, and then the saturation inductance value is calculated by the collected voltage and current values, such as the patent with authorization announcement number CN105634362B. The biggest disadvantage of this method is that it cannot be self-learned with load. Its principle can be described by Figure 3 The equivalent circuit diagram of the asynchronous motor shown in the figure is analyzed in a two-phase coordinate system with a rotation speed of synchronous speed. r When the motor is rotating and the load is almost zero, ω r =ω e , the rotor circuit can be regarded as an open circuit, Figure 3 The equivalent circuit is converted to Figure 4 In the form of, the calculation method of active power and reactive power can be used to calculate the mutual inductance value, or the phase difference of voltage and current can be used to calculate the mutual inductance value. However, when the motor is loaded and the load cannot be accurately quantified, the rotor circuit cannot be regarded as an open circuit, and the mutual inductance value cannot be calculated. In addition, this method has many obstacles in practical application: First, the speed setting and running time under self-learning are not controlled by the outside world. It is easy to conflict with the actual allowed running distance on the hoisting mechanism of the crane and cannot be applied. In the case of multiple motors controlling the same load in the shield machine cutter head mechanism, high-speed rotation may cause mechanical biased drive and mechanical damage; Second, this method is essentially a voltage-frequency ratio control mode, not a vector control mode. When the equipment is running with load, this self-learning method cannot be used directly (for example, the hoisting mechanism of some cranes, the empty hoist will generate 30-50% of the rated load). Even if this self-learning method must be applied in industrial sites, it is necessary to separate the motor from the actual load machinery. And this requirement is often difficult to implement in industrial sites.

[0008] Therefore, how to provide a method that allows an asynchronous motor to self-learn the stator saturation inductance value of the motor under load is an urgent problem that those skilled in the art need to solve. Summary of the invention

[0009] In view of this, the present invention provides a self-learning method for the stator saturation inductance value of an asynchronous motor, which enables the asynchronous motor to operate in a vector control mode and self-learn the motor saturation inductance value at a low speed. Since the asynchronous motor can carry a load, the asynchronous motor does not need to be disconnected from the load. Due to the low-speed operation, it is not restricted in situations where the load running distance or angle is limited, and it is safe. Since the value of the motor inductance under different magnetic field saturation levels is accurately self-learned, the adaptability to low-speed heavy load and high-speed heavy load is stronger.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] A self-learning method for the stator saturation inductance value of an asynchronous motor, comprising:

[0012] Change the stator flux setpoint

[0013] The inverter controls the asynchronous motor to run at the stator flux given value Vector control mode under ;

[0014] Calculate the active power and reactive power of the asynchronous motor based on the three-phase stator current and stator voltage of the asynchronous motor output in the vector control mode;

[0015] Calculating a stator saturation inductance based on the active power and the reactive power;

[0016] It is determined whether the stator saturation inductance converges. If so, the stator saturation inductance is used as an initial value. Otherwise, the vector control mode is continued to wait for convergence.

[0017] Preferably, the vector control mode specifically includes the following steps:

[0018] Set the speed to the given value ω γ * The speed feedback from the motor speed encoder ω γ After subtraction, the torque current set value is generated by the first PT regulator The torque current given value and torque current feedback value Subtract and generate the torque voltage set value through the second PI regulator

[0019] The stator flux set value And stator flux feedback value Subtract and generate the excitation torque current given value through the third PI regulator The excitation torque current given value and excitation torque current feedback value Subtract and generate the excitation voltage given value through the fourth PI regulator

[0020] The torque voltage set value and the excitation voltage given value After the stationary coordinate system to rotating coordinate system conversion unit, the torque voltage given value v in the stationary coordinate system is generated accordingly. ds * and the excitation voltage given value v in the stationary coordinate system qs * , the angle between the rotating coordinate system and the stationary coordinate system is θ;

[0021] The torque voltage given value v in the stationary coordinate system ds * and the excitation voltage given value v in the stationary coordinate system qs * The PWM pulse modulation unit generates a modulated bus voltage V DC The duty cycle data DutyCycle drives the inverter to generate three-phase voltage to control the rotation of the asynchronous motor;

[0022] The three-phase current i of the asynchronous motor as ,i bs ,i csIt is detected by the current detection unit and converted into the current i in the two-phase stationary coordinate system by the stator current 3 / 2 conversion unit. ds and i qs , the current i in the two-phase stationary coordinate system ds and i qs The torque current feedback value is obtained by converting the rotating coordinate system to the stationary coordinate system. and the excitation torque current feedback value

[0023] The three-phase current i of the asynchronous motor as ,i bs ,i cs , the inverter bus voltage V DC And the duty cycle data DutyCycle is passed through the motor voltage reconstruction unit to obtain the voltage v on the two-phase stationary coordinate system ds and v qs ;

[0024] The voltage v on the two-phase stationary coordinate system ds and v qs , the current i in the two-phase stationary coordinate system ds and i qs The angle between the rotating coordinate system and the stationary coordinate system and the stator flux feedback value are calculated by the stator flux amplitude and angle calculation unit.

[0025] Preferably, the calculation formula used by the stationary coordinate system to rotating coordinate system conversion unit is:

[0026]

[0027]

[0028] Among them, θ represents the angle between the rotating coordinate system and the stationary coordinate system, Indicates the torque voltage given value, Indicates the given value of excitation voltage, v ds * Represents the torque voltage given value in the stationary coordinate system, v qs * It represents the given value of the excitation voltage in the stationary coordinate system.

[0029] Preferably, the calculation formula adopted by the stator current 3 / 2 conversion unit is as follows:

[0030]

[0031]

[0032] Among them, ias ,i bs ,i cs Represents the three-phase current of the asynchronous motor, i ds and i qs Represents the current in the two-phase stationary coordinate system.

[0033] Preferably, the calculation formula used by the rotating coordinate system to stationary coordinate system conversion unit is as follows:

[0034]

[0035]

[0036] in, Indicates the torque current feedback value, Indicates the excitation torque current feedback value, i ds and i qs represents the current in the two-phase stationary coordinate system, and θ represents the angle between the rotating coordinate system and the stationary coordinate system.

[0037] Preferably, the calculation formula used by the stator flux amplitude and angle calculation unit is as follows:

[0038] λ ds =∫(v ds -R s i ds )dt

[0039] λ qs =∫(v qs -R s i qs )dt

[0040]

[0041]

[0042]

[0043] Among them, R s represents the stator resistance, i ds and i qs represents the current in the two-phase stationary coordinate system, v ds and v qs represents the voltage on the two-phase stationary coordinate system, and θ represents the angle between the rotating coordinate system and the stationary coordinate system.

[0044] Preferably, the calculation formula for the active power and reactive power of the asynchronous motor is:

[0045]

[0046]

[0047] Among them, p e Indicates the active power of the asynchronous motor, Q e Represents the reactive power of the asynchronous motor, R s represents the stator resistance, w e represents the stator frequency, P represents the differential operation, Represents the power combined stator flux used to calculate the stator saturation inductance.

[0048] Preferably, the stator saturation inductance calculation process is:

[0049] From the expression for active power we get the component R s (i ds 2 +i qs 2 ) is found from the known quantities, In steady state, it is 0, and the component is obtained from the expression of reactive power It is 0 in steady state, so two variables including power and stator flux are calculated:

[0050]

[0051] The power combined with the stator flux is calculated by the above formula:

[0052]

[0053] The stator saturation inductance calculation formula is:

[0054]

[0055] Among them, LPF represents low-pass filter, Ls represents stator saturation inductance, Lr represents the rotor inductance value given before self-learning, Ls represents the stator saturation inductance given before self-learning, and Lm represents the mutual inductance value between the stator and the rotor.

[0056] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a self-learning method for the stator saturation inductance value of an asynchronous motor. Under low-speed steady state, the active power related to the load and the reactive power independent of the load are calculated separately (the calculation only requires the motor voltage and current, and does not require motor parameters). The components related to the load are removed from the calculation formula of the reactive power, and only the components related to the flux, stator frequency and reactive components are retained. After the flux is calculated, the stator saturation inductance is calculated based on the relationship between the flux and the stator saturation inductance, so that the result of self-learning is not affected by the load size. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0058] Figure 1 It is the equivalent circuit diagram of an asynchronous motor in a stationary two-phase coordinate system.

[0059] Figure 2 It is the equivalent circuit diagram of the asynchronous motor in a stationary two-phase coordinate system when the Vs power supply frequency is very low.

[0060] Figure 3 It is the equivalent circuit diagram of an asynchronous motor in a two-phase coordinate system with a rotation speed of synchronous speed.

[0061] Figure 4 It is the equivalent circuit diagram of the asynchronous motor in the no-load state in the two-phase coordinate system with the rotating speed being the synchronous speed.

[0062] Figure 5 It is a closed-loop vector control principle diagram adopted by the present invention.

[0063] Figure 6 This is a flow chart of self-learning the stator saturation inductance value provided by the present invention.

[0064] Figure 7 It is a schematic diagram of self-learning the stator saturation inductance value under different stator magnetic field saturation degrees provided by the present invention.

[0065] Figure 1 In, R s is the stator resistance, L ls is the stator leakage inductance, L m is the mutual inductance of the stator and rotor, L lr is the leakage inductance of the rotor, R r is the rotor resistance, V qds is the composite expression of the stator voltage, jω r λ r It is the electric potential generated by the rotor rotation speed under the action of the rotor magnetic flux.

[0066] Figure 2 In, R s is the stator resistance, L ls is the stator leakage inductance, L m is the mutual inductance of the stator and rotor, L lr is the leakage inductance of the rotor, R r is the rotor resistance, V qds is a composite expression for the stator voltage.

[0067] Figure 3 In, R s is the stator resistance, L ls is the stator leakage inductance, L m is the mutual inductance of the stator and rotor, L lr is the leakage inductance of the rotor, R r is the rotor resistance, is the composite expression of the stator voltage in the synchronous rotating coordinate system, jω e λ qds is the potential generated by the synchronous rotation speed of the coordinate system under the action of the stator flux, j(ω e -ω r ) qdr It is the potential generated by the speed difference between the stator rotation speed and the rotor rotation speed under the action of the rotor magnetic flux. They are the composite expressions of stator current and rotor current in synchronous rotating coordinate system.

[0068] Figure 4 In, R s is the stator resistance, L ls is the stator leakage inductance, L m is the mutual inductance of the stator and rotor, jω e λ qds It is the electric potential generated by the synchronous rotation speed of the coordinate system under the action of the stator magnetic flux.

[0069] Figure 5 Among them, 1. the first PI regulator, 2. the second PI regulator, 3. the third PI regulator, 4. the fourth PI regulator, 5. the stationary coordinate system to the rotating coordinate system conversion unit, 6. the PWM pulse modulation unit, 7. the frequency converter, 8. the current detection unit, 9. the asynchronous motor, 10. the motor speed encoder, 11. the motor voltage reconstruction unit 12. the stator flux amplitude and angle calculation unit, 13. the stator current 3 / 2 transformation unit, 14. the rotating coordinate system to the stationary coordinate system conversion unit. DETAILED DESCRIPTION

[0070] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] The embodiment of the present invention discloses a self-learning method for the stator saturation inductance value of an asynchronous motor, such as Figure 6 As shown, including:

[0072] Step 1: Change the stator flux setpoint For example, from 70% rated flux linkage to 130% rated flux linkage, or other values, which are not specifically limited and can be set according to needs;

[0073] Step 2: The inverter controls the asynchronous motor to run at the given value of stator flux The vector control mode under Figure 5 As shown:

[0074] Step 21: Set the speed to the given value ω γ * The speed feedback from the motor speed encoder ω γ After subtraction, the torque current set value is generated by the first PT regulator 1 Torque current setting and torque current feedback value Subtract, and generate torque voltage given value through the second PI regulator 2

[0075] Stator flux set value And stator flux feedback value Subtract, and generate the excitation torque current given value through the third PI regulator 3 Excitation torque current setting value and excitation torque current feedback value Subtract, and generate the excitation voltage given value through the fourth PI regulator 4

[0076] Step 22: Torque voltage setpoint and excitation voltage given value The torque voltage given value v in the stationary coordinate system is generated by the stationary coordinate system to rotating coordinate system conversion unit 5. ds * and the given value of the excitation voltage v in the stationary coordinate system qs * , the angle between the rotating coordinate system and the stationary coordinate system is θ, and the calculation formula used by the stationary coordinate system to rotating coordinate system conversion unit 5 is:

[0077]

[0078]

[0079] Step 23: Torque voltage given value v in the stationary coordinate system ds * and the given value of the excitation voltage v in the stationary coordinate system qs * The PWM pulse modulation unit 6 generates a modulated bus voltage V DCThe duty cycle data DutyCycle drives the frequency converter to generate a three-phase voltage to control the asynchronous motor 9 to rotate;

[0080] Step 24: Three-phase current i of asynchronous motor as ,i bs ,i cs The current is detected by the current detection unit 8 and converted into the current i in the two-phase stationary coordinate system by the stator current 3 / 2 conversion unit 13. ds and i qs , the current i in the two-phase stationary coordinate system ds and i qs The torque current feedback value is obtained by converting the rotating coordinate system to the stationary coordinate system through the unit 14. and excitation torque current feedback value The calculation formula used by the stator current 3 / 2 conversion unit 13 is as follows:

[0081]

[0082]

[0083] The calculation formula used by the rotating coordinate system to stationary coordinate system conversion unit 14 is as follows:

[0084]

[0085]

[0086] The three-phase current i of the asynchronous motor as ,i bs ,i cs , the inverter bus voltage V DC The duty cycle data DutyCycle is passed through the motor voltage reconstruction unit 11 to obtain the voltage v on the two-phase stationary coordinate system ds and v qs ;

[0087] Step 25: Voltage v on the two-phase stationary coordinate system ds and v qs , the current i in the two-phase stationary coordinate system ds and i qs The angle between the rotating coordinate system and the stationary coordinate system and the stator flux feedback value are calculated by the stator flux amplitude and angle calculation unit 12. The calculation formula used by the stator flux amplitude and angle calculation unit 12 is as follows:

[0088] λ ds =∫(v ds -R s i ds )dt

[0089] λ qs =∫(v qs -R s i qs )dt

[0090]

[0091]

[0092]

[0093] Among them, R s represents the stator resistance, i ds and i qs represents the current in the two-phase stationary coordinate system, v ds and v qs represents the voltage on the two-phase stationary coordinate system, and θ represents the angle between the rotating coordinate system and the stationary coordinate system.

[0094] Step 3: Calculate the active power and reactive power of the asynchronous motor based on the three-phase stator current and stator voltage of the asynchronous motor output in the vector control mode; specifically:

[0095]

[0096]

[0097] In the coordinate system of stator flux orientation, the expression of motor stator voltage is (Formula 7) (Formula 8), where Represents the power combined with the stator flux used to calculate the stator saturation inductance:

[0098]

[0099]

[0100]

[0101] Substituting formula (7) and (8) into formula (5) and (6), we get

[0102]

[0103]

[0104] Among them, p e Indicates the active power of the asynchronous motor, Q e Represents the reactive power of the asynchronous motor, R s represents the stator resistance, w e represents the stator frequency, P represents the differential operation, represents the projection of the stator voltage vector on the synchronously rotating coordinate axis, Represents the projection of the stator voltage vector on the vertical axis of the synchronously rotating coordinate axis.

[0105] From the expression for active power we get the component R s (i ds 2 +i qs 2 ) is found from the known quantities, In steady state, it is 0, and the component is obtained from the expression of reactive power It is 0 in steady state, so two variables including stator flux are calculated:

[0106]

[0107]

[0108] Step 4: Calculate the stator saturation inductance based on the active power and reactive power; specifically:

[0109] From formulas (12) and (13), we can get the expression of power combined with stator flux:

[0110]

[0111] It can be seen from the expression that when the motor is running in a steady state, the final expression of the stator flux on the right side of the equal sign is the same as the motor load torque current. Not relevant.

[0112] In the stator field oriented coordinate system, the expression of power combined with stator flux and slip frequency is:

[0113]

[0114]

[0115] When the motor is running in steady state, the results of all differential operations p are 0, so substituting formula (16) into formula (15) yields:

[0116]

[0117] The expression of stator saturation inductance can be obtained from formula (17):

[0118]

[0119] Therefore, the method for obtaining the stator saturation inductance is as follows:

[0120]

[0121] Among them, LPF represents low-pass filter, Ls represents stator saturation inductance, Lr represents the rotor inductance value given before self-learning, Ls represents the stator saturation inductance given before self-learning, and Lm represents,

[0122] It can be seen from formula (19) that the acquisition of stator saturation inductance is related to the motor load torque current It has nothing to do with the motor excitation torque current. related.

[0123] Before learning the stator saturation inductance value, the motor parameters required for vector control, such as stator resistance Rs, rotor resistance Rr, stator total leakage inductance σL s It can be obtained through public technology, and the stator saturation inductance Ls given before self-learning and the rotor inductance value Lr given before self-learning, although not yet self-learned, can be given through empirical formulas.

[0124] Step 5: Determine whether the stator saturation inductance converges. Convergence means that the change value of the stator saturation inductance value within a period of time (for example, 0.5 seconds) is less than a certain threshold. If converged, the self-learned stator saturation inductance is used as the initial value of the stator saturation inductance used by the vector control, and the flux linkage given value is changed. Otherwise, return to step 2 to continue vector control and continue to wait for convergence (if it still does not converge after a certain preset time, it means that the self-learning has failed.

[0125] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0126] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A self-learning method for the stator saturation inductance value of an asynchronous motor, characterized in that: include: Change the stator flux setpoint The inverter controls the asynchronous motor to run at the stator flux given value Vector control mode under ; Calculate the active power and reactive power of the asynchronous motor based on the three-phase stator current and stator voltage of the asynchronous motor output in the vector control mode; Calculating a stator saturation inductance based on the active power and the reactive power; Determine whether the stator saturation inductance converges, if so, use the stator saturation inductance as an initial value, otherwise continue to perform vector control mode and wait for convergence; The vector control mode is specifically The following steps are involved: Set the speed to the given value ω γ * The speed feedback from the motor speed encoder ω γ After subtraction, the torque current set value is generated through the first PI regulator The torque current given value and torque current feedback value Subtract and generate the torque voltage set value through the second PI regulator The stator flux set value And stator flux feedback value Subtract and generate the excitation torque current given value through the third PI regulator The excitation torque current given value and excitation torque current feedback value Subtract and generate the excitation voltage given value through the fourth PI regulator The torque voltage set value and the excitation voltage given value After the stationary coordinate system is converted to the rotating coordinate system, the torque voltage given value in the stationary coordinate system is generated accordingly. And the excitation voltage given value in the stationary coordinate system The angle between the rotating coordinate system and the stationary coordinate system is θ; The torque voltage given value in the stationary coordinate system and the excitation voltage given value in the stationary coordinate system The PWM pulse modulation unit generates a modulated bus voltage V DC The duty cycle data DutyCycle drives the inverter to generate three-phase voltage to control the asynchronous motor to rotate; The three-phase current i of the asynchronous motor as ,i bs ,i cs It is detected by the current detection unit and converted into the current i in the two-phase stationary coordinate system by the stator current 3 / 2 conversion unit. ds and i qs , the current i in the two-phase stationary coordinate system ds and i qs The torque current feedback value is obtained by converting the rotating coordinate system to the stationary coordinate system. and the excitation torque current feedback value The three-phase current i of the asynchronous motor as ,i bs ,i cs , the inverter bus voltage V DC And the duty cycle data DutyCycle is passed through the motor voltage reconstruction unit to obtain the voltage v on the two-phase stationary coordinate system ds and v qs ; The voltage v on the two-phase stationary coordinate system ds and v qs , the current i in the two-phase stationary coordinate system ds and i qs The angle between the rotating coordinate system and the stationary coordinate system and the stator flux feedback value are calculated by the stator flux amplitude and angle calculation unit. The calculation formulas for the active power and reactive power of the asynchronous motor are: Among them, p e Indicates the active power of the asynchronous motor, Q e Represents the reactive power of the asynchronous motor, R s is the stator resistance, ω e represents the stator frequency, P represents the differential operation, represents the power combined with the stator flux; The stator saturation inductance calculation process is: From the expression for active power we get the component R s (i ds 2 +i qs 2 ) is found from the known quantities, In steady state, it is 0, and the component is obtained from the expression of reactive power It is 0 in steady state, so two variables including stator flux are calculated: The power combined with the stator flux is calculated by the above formula It can be seen from the expression that when the motor is running in a steady state, the final expression of the stator flux on the right side of the equal sign is the same as the motor load torque current. Not relevant; In the stator field oriented coordinate system, the expression of power combined with stator flux and slip frequency is: When the motor is running in steady state, the results of all differential operations p are 0, so the slip frequency is substituted into the stator flux to obtain: The stator saturation inductance calculation formula is: Among them, LPF means low-pass filter, L r Indicates the rotor inductance value given before self-learning, L S Indicates the stator saturation inductance given before self-learning, L m Represents the mutual inductance between the stator and the rotor.

2. The method for self-learning the stator saturation inductance of an asynchronous motor according to claim 1, characterized in that: The calculation formula used by the stationary coordinate system to rotating coordinate system conversion unit is: Among them, θ represents the angle between the rotating coordinate system and the stationary coordinate system, Indicates the torque voltage given value, Indicates the given value of excitation voltage, Indicates the torque voltage given value in the stationary coordinate system, It represents the given value of the excitation voltage in the stationary coordinate system.

3. The self-learning method of the stator saturation inductance value of an asynchronous motor according to claim 1, characterized in that: The calculation formula used by the stator current 3 / 2 conversion unit is as follows: Among them, i as ,i bs ,i cs Represents the three-phase current of the asynchronous motor, i ds and i qs Represents the current in the two-phase stationary coordinate system.

4. The method for self-learning the stator saturation inductance of an asynchronous motor according to claim 1, characterized in that: The calculation formula used by the rotating coordinate system to stationary coordinate system conversion unit is as follows: in, Indicates the torque current feedback value, Indicates the excitation torque current feedback value, i ds and i qs represents the current in the two-phase stationary coordinate system, and θ represents the angle between the rotating coordinate system and the stationary coordinate system.

5. The method for self-learning the stator saturation inductance of an asynchronous motor according to claim 1, characterized in that: The calculation formula used by the stator flux amplitude and angle calculation unit is as follows: λ ds =∫(v ds -R s i ds )dt λ qs =∫(v qs -R s i qs )dt Among them, R s represents the stator resistance, i ds and i qs represents the current in the two-phase stationary coordinate system, v ds and v qs represents the voltage on the two-phase stationary coordinate system, and θ represents the angle between the rotating coordinate system and the stationary coordinate system.

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