A method for offline identification of leakage inductance of asynchronous motor

Abstract

The present invention provides an asynchronous motor leakage inductance offline identification method, which includes obtaining a core saturation current, obtaining the sum of a stator leakage inductance and a rotor leakage inductance in an asynchronous motor model, obtaining a stator-rotor total leakage inductance measurement value, calculating a stator leakage inductance measurement value in the asynchronous motor model under a core saturation current bias, and calculating a rotor leakage inductance measurement value. The application of the asynchronous motor leakage inductance offline identification method of the present invention is conducive to improving the asynchronous motor offline identification accuracy and improving the effect of the asynchronous motor sensorless vector control.

Description

Technical Field

[0001] The present invention relates to the technical field of asynchronous motors, and in particular to an offline identification method for leakage inductance of an asynchronous motor. Background Art

[0002] Certain papers and methods will be described in the following discussion for background and introductory purposes. Nothing contained herein is to be construed as an admission of prior art. Applicants expressly reserve the right to demonstrate, where appropriate and in accordance with applicable statutory provisions, that the papers and methods cited herein do not constitute prior art.

[0003] The speed sensorless vector control system of asynchronous motor must rely on motor parameters to complete the observation of magnetic flux and speed. Its control accuracy and performance are greatly affected by the parameters. How to accurately obtain the motor parameters is the primary problem of the vector control system.

[0004] Asynchronous motor parameter identification can generally be divided into two categories: online and offline. Offline identification can ensure the safe and reliable start-up of the motor, provide more accurate initial values ​​for the online identification algorithm, and accelerate the convergence speed of the online identification algorithm.

[0005] The mathematical model of the asynchronous motor is generally represented by an equivalent T-type model converted to the stator side. Figure 1 As shown. The load is represented by an equivalent resistance Rload controlled by the slip rate s. The motor parameters include 6 quantities: stator resistance Rs, rotor resistance Rr, stator leakage inductance Lsl, rotor leakage inductance Lrl, mutual inductance Lm and core iron loss Rm. It is worth noting that the mutual inductance Lm is much larger than the leakage inductance Lsl and Lrl, and is greatly affected by the saturation of the core. The core loss Rm is the AC resistance, and under DC excitation, the resistance is zero.

[0006] The traditional offline identification method of electric motors is to conduct offline identification through three experiments: DC excitation, locked-rotor operation, and no-load operation (Tang Yunmiao. Electric Motors—Electromechanical Energy Conversion Volume 1 [M]. Machinery Industry Press, 1981.). Among them, the DC excitation experiment measures the stator resistance Rs; the no-load operation experiment measures the mutual inductance Lm and the core iron loss Rm; the locked-rotor experiment measures the rotor resistance Rr and the stator-rotor leakage inductance Lsl and Lrl.

[0007] In practical applications, since locked-rotor operation is difficult to achieve, single-phase AC excitation experiments or single-phase pulse vibration experiments are often used instead, such as an asynchronous motor parameter offline identification method with patent number CN104883112A and an asynchronous motor parameter identification method and system with patent number CN105846749A.

[0008] Among them, three unknown quantities need to be measured in the stall test. Usually, it is necessary to assume the ratio of stator leakage inductance Lsl to rotor leakage inductance Lrl according to the type of motor, as shown in Table 1. Table 1 is the empirical value of asynchronous motor leakage reactance distribution (Lin Youjie, Wu Hanguang. A new method for calculating equivalent circuit parameters of asynchronous motors [J]. Journal of Fuzhou University (Natural Science Edition), 2006(04):57-60.).

[0009] Table 1:

[0010]

[0011] Prior art 1: Traditional motor parameter experiments include three experiments: DC excitation, locked-rotor operation, and no-load operation. (Tang Yunmiao. Motors—Electromechanical Energy Conversion Volume 1 [M]. Machinery Industry Press, 1981.)

[0012] The specific process of determining the parameters is as follows:

[0013] DC experiment: Apply DC voltage excitation, then the equivalent circuit is as follows Figure 2 As shown,

[0014] Measure the input voltage and input current, and calculate the DC resistance R.

[0015] According to the circuit model, R=Rs.

[0016] Stalling experiment: The motor is stalled and AC voltage is applied. The power frequency f = fn (rated frequency), and the slip rate s = 1. At this time, since the mutual inductance Lm is much larger than the leakage inductance Lsl and Lrl, it can be considered that the excitation circuit is open. Its equivalent circuit is as follows Figure 3 shown.

[0017] Measure the input voltage and input current, and calculate the input impedance R+jωL.

[0018] According to the circuit model, R=Rs+Rr and L=Lsl+Lrl.

[0019] In practical applications, the stall test can be replaced by a single-phase AC excitation test or a single-phase pulse vibration test. The circuit model and solution method are the same.

[0020] No-load experiment: The motor is unloaded, AC voltage is applied, power frequency f = fn (rated frequency), slip rate s ≈ 0, then the equivalent circuit is as follows Figure 4 shown.

[0021] Measure the input voltage and input current, and calculate the input impedance R+jωL.

[0022] According to the circuit model, R=Rs+Rm and L=Lsl+Lm.

[0023] The disadvantage of the prior art 1 is that it needs to assume the leakage inductance ratio, which is prone to misjudgment when the motor characteristics are not understood. The fixed leakage inductance ratio has limited accuracy.

[0024] Prior art 2, based on the above three experiments, a set of fixed load experiments is added. (Lin Youjie, Wu Hanguang. A new method for calculating equivalent circuit parameters of asynchronous motors [J]. Journal of Fuzhou University (Natural Science Edition), 2006 (04): 57-60.).

[0025] Load test: Apply a fixed load and apply AC voltage excitation. The power frequency f = fn (rated frequency), the slip rate is determined by the load condition s = sload, and the equivalent circuit is as follows Figure 5 shown.

[0026] Measure the input voltage and input current, and calculate the input impedance R+jωL.

[0027] According to the circuit model, R=f(Rs,Lsl,Rr,Lrl,Rm,Lm) and L=g(Rs,Lsl,Rr,Lrl,Rm,Lm).

[0028] Among them, f() and g() are linear circuit expressions corresponding to input impedance.

[0029] Disadvantages of the second prior art: harsh experimental conditions. Difficulty in solving the load test equations, requiring high measurement accuracy. Large amount of calculation. No consideration of motor nonlinearity.

[0030] Prior art three, in the stall test, the assumption that the mutual inductance Lm is much larger than the leakage inductance Lsl and Lrl is abandoned. Two sets of stall tests with different power supply frequencies are conducted. In addition, pulse current experiments are conducted, and the ratio of Lsl and Lrl can be obtained according to some formulas, such as a method for identifying asynchronous motor parameters with patent number CN103281033A.

[0031] The disadvantage of the prior art 3 is that the calculation formula used in the patent has obvious errors, especially the formula used to solve the rotor resistance when testing the horizontal stage using the trapezoidal current signal:

[0032]

[0033] Since the current change rate is zero in the horizontal stage, no voltage drop can be generated in the rotor circuit in the model. Therefore, there is a fundamental error in the above formula. Summary of the invention

[0034] The main purpose of the present invention is to provide an asynchronous motor leakage inductance offline identification method which directly measures the motor stator and rotor leakage inductance from the experimental data of the asynchronous motor by utilizing the motor core saturation.

[0035] In order to achieve the above main purpose, the present invention provides an asynchronous motor leakage inductance offline identification method, which includes obtaining a core saturation current; obtaining the sum of a stator leakage inductance and a rotor leakage inductance in an asynchronous motor model to obtain a stator-rotor total leakage inductance measurement value; calculating a stator leakage inductance measurement value in the asynchronous motor model under a core saturation current bias; and calculating a rotor leakage inductance measurement value.

[0036] In a further solution, a no-load running experiment is performed on the asynchronous motor to obtain a bias current amplitude corresponding to the core saturation as the core saturation current.

[0037] In a further scheme, in step S11, low-voltage AC excitation is applied to the stator at its rated operating frequency; in step S12, the three-phase current of the stator three-phase winding in step S11 when it reaches a steady state under low-voltage AC excitation is collected through the corresponding inverter, and the equivalent impedance of the asynchronous motor is calculated; in step S13, the AC excitation voltage applied to the stator in step S11 is slowly increased, and the equivalent impedance of the asynchronous motor in a metastable state is measured; in step S14, when the imaginary part of the equivalent impedance of the asynchronous motor reaches a maximum value, the three-phase current amplitude measured by the inverter is used as the core saturation current.

[0038] In a further scheme, a single-phase pulse vibration experiment is carried out on the asynchronous motor, and the imaginary part of the input AC impedance of the asynchronous motor is measured without DC current bias as the measurement value of the total stator-rotor leakage inductance.

[0039] In a further scheme, in step S21, a single-phase excitation pulse voltage is applied to any two-phase windings of the stator to perform a pulse test; in step S22, the duty cycle of the excitation pulse voltage applied to the stator is gradually increased until the current sampling value in the step S21 reaches a suitable value lower than the core saturation current; in step S23, based on the current sampling value obtained in the step S22, the imaginary part of the input AC impedance of the asynchronous motor is measured as the total leakage inductance measurement value of the stator and rotor.

[0040] In a further scheme, a single-phase pulse vibration experiment with a DC bias is performed on the asynchronous motor, and the imaginary part of the input AC impedance of the asynchronous motor is measured under the core saturation current bias as the stator leakage inductance measurement value.

[0041] In a further scheme, in step S31, a single-phase excitation pulse voltage with a DC bias is applied to any two-phase winding of the stator to perform a pulse test with a DC bias; in step S32, the duty cycle of the excitation pulse voltage applied to the stator is gradually increased until the current sampling average value in the step S21 reaches the core saturation current; in step S33, based on the current sampling value obtained in the step S32, the imaginary part of the input AC impedance of the asynchronous motor is measured as the stator leakage inductance measurement value.

[0042] In a further embodiment, the rotor leakage inductance measurement value is calculated based on the stator-rotor total leakage inductance measurement value and the stator leakage inductance measurement value.

[0043] In a further solution, the calculation formula of the rotor leakage inductance measurement value is as follows: Lrl=Ll–Lsl, wherein Ll is the stator-rotor total leakage inductance measurement value, and Lsl is the stator leakage inductance measurement value.

[0044] It can be seen that the present invention provides an asynchronous motor leakage inductance offline identification method. First, an improved no-load running experiment is used to obtain the bias current corresponding to the core saturation, which is used as the core saturation current. Then, a single-phase pulse vibration experiment without DC bias and a single-phase pulse vibration experiment with DC bias are performed. Then, the stator leakage inductance and rotor leakage inductance of the asynchronous motor are obtained according to the circuit model of the core in the unsaturated state and the saturated state. This is beneficial to improving the offline identification accuracy of the asynchronous motor and improving the effect of sensorless vector control of the asynchronous motor.

[0045] Furthermore, the present invention utilizes the circuit model equation to independently calculate the rotor leakage inductance of the asynchronous motor, thereby avoiding the use of empirical formulas to directly infer the rotor leakage inductance from the stator leakage inductance, and has high identification accuracy.

[0046] In addition, the present invention uses an improved asynchronous motor no-load experiment to infer the saturation current of the motor core, without the need for the user to provide prior information on the saturation current, further reducing the dependence of motor identification on user input parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural schematic diagram of an equivalent T-type model of an asynchronous motor of prior art one.

[0048] Figure 2 It is a structural schematic diagram of an equivalent circuit model of a DC experiment of prior art one.

[0049] Figure 3 It is a structural schematic diagram of an equivalent circuit model of a stall test in the prior art.

[0050] Figure 4 It is a structural schematic diagram of an equivalent circuit model of a no-load experiment of prior art one.

[0051] Figure 5 It is a structural schematic diagram of an equivalent circuit model of a load experiment of the second prior art.

[0052] Figure 6 It is a flowchart of an embodiment of an asynchronous motor leakage inductance offline identification method of the present invention.

[0053] Figure 7It is a schematic diagram of impedance values ​​measured under different voltage inputs of a YE2-90-4 high-efficiency three-phase asynchronous motor in an embodiment of an asynchronous motor leakage inductance offline identification method of the present invention in an improved no-load operation experiment.

[0054] Figure 8 It is an excitation waveform diagram of a single-phase pulse vibration experiment without DC bias on an asynchronous motor in an embodiment of an asynchronous motor leakage inductance offline identification method of the present invention.

[0055] Fig. 9 It is an excitation waveform diagram of a single-phase pulse vibration experiment with a DC bias on an asynchronous motor in an embodiment of an asynchronous motor leakage inductance offline identification method of the present invention.

[0056] Fig.10 The present invention is a schematic diagram of an inverter circuit in an embodiment of an asynchronous motor leakage inductance offline identification method.

[0057] Fig.11 It is the first equivalent circuit diagram of a single-phase pulse vibration experiment without DC bias on an asynchronous motor in an embodiment of an asynchronous motor leakage inductance offline identification method of the present invention.

[0058] Fig.12 It is a second equivalent circuit diagram of a single-phase pulse vibration experiment without DC bias on an asynchronous motor in an embodiment of an asynchronous motor leakage inductance offline identification method of the present invention.

[0059] Fig.13 The invention discloses an equivalent circuit diagram of a method for offline identification of leakage inductance of an asynchronous motor in which a single-phase pulse vibration experiment with a DC bias is performed on the asynchronous motor.

[0060] The present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment 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.

[0062] Unless otherwise defined, the technical terms or scientific terms used in this disclosure should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, similar words such as "one", "one" or "the" do not indicate quantity restrictions, but indicate that there is at least one. Similar words such as "include" or "comprise" mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Similar words such as "connect" or "connected" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0063] In the offline identification experiment of asynchronous motor, the traditional method assumes the ratio of stator leakage inductance Lsl to rotor leakage inductance Lrl according to the motor type. The present invention uses the core saturation characteristics and a pulse test experiment with a large DC current bias to achieve independent measurement of the stator leakage inductance Lsl.

[0064] See also Figure 6 The present invention provides an asynchronous motor leakage inductance offline identification method suitable for offline identification of parameters of high power density asynchronous motors with high magnetic circuit saturation. When performing offline identification of parameters of the asynchronous motor, first, step S1 is executed to obtain the core saturation current. The asynchronous motor is subjected to a no-load operation experiment, and the bias current amplitude corresponding to the core saturation is obtained as the core saturation current Isat.

[0065] In this embodiment, a no-load operation experiment (improved no-load experiment of asynchronous motor) is performed on the asynchronous motor, which specifically includes the following steps:

[0066] Step S11, applying low voltage AC excitation to the stator according to its rated operating frequency.

[0067] Step S12, collecting the three-phase current of the stator three-phase winding when reaching a steady state under low-voltage AC excitation in step S11 through the corresponding inverter, and calculating the equivalent impedance of the asynchronous motor at this time.

[0068] Step S13, slowly increasing the AC excitation voltage applied to the stator in step S11, and measuring the equivalent impedance of the asynchronous motor in the metastable state.

[0069] Step S14, when the imaginary part of the asynchronous motor equivalent impedance reaches a maximum value, the three-phase current amplitude measured by the inverter at this time is used as the core saturation current Isat.

[0070] Since high power density motors optimize the utilization of the magnetic core, the saturation current of the magnetic core is generally less than the rated working current of the motor. At no-load rated speed, when the input voltage is increased, the imaginary part of the input impedance of the motor increases first and then decreases. The former stage is due to the decrease in the slip rate of the motor, and the latter stage is due to the gradual saturation of the magnetic core. The present invention uses the current when the imaginary part of the impedance begins to decrease as the current Isat corresponding to the saturation of the magnetic core. Taking the YE2-90-4 high-efficiency three-phase asynchronous motor as an example, when the driving frequency is 50Hz, the impedance values ​​measured under different voltage inputs are as follows: Figure 7 shown.

[0071] Then, step S2 is performed to obtain the sum of the stator leakage inductance and the rotor leakage inductance in the asynchronous motor model to obtain the stator-rotor total leakage inductance measurement value L1. Wherein, the obtaining of the sum of the stator leakage inductance and the rotor leakage inductance in the asynchronous motor model includes performing a single-phase pulse vibration experiment on the asynchronous motor, measuring the imaginary part of the input AC impedance of the asynchronous motor without DC current bias, as the stator-rotor total leakage inductance measurement value L1.

[0072] In this embodiment, the single-phase pulse vibration experiment (single-phase pulse vibration experiment without DC bias) on the asynchronous motor specifically includes the following steps:

[0073] Step S21, applying a single-phase excitation pulse voltage to any two-phase windings of the stator to perform a pulse test, and the excitation waveform is as follows: Figure 8 shown.

[0074] Step S22, to improve the identification accuracy, gradually increase the duty cycle of the excitation pulse voltage applied to the stator until the current sampling value in step S21 reaches a suitable value lower than the core saturation current.

[0075] Step S23: According to the current sampling value obtained in step S22, the imaginary part of the input AC impedance of the asynchronous motor is measured as the total leakage inductance measurement value of the stator and rotor.

[0076] Next, step S3 is performed to calculate the stator leakage inductance measurement value Lsl in the asynchronous motor model under the core saturation current Isat bias. A single-phase pulse vibration experiment with a DC bias is performed on the asynchronous motor, and the imaginary part of the input AC impedance of the asynchronous motor is measured under the core saturation current Isat bias as the stator leakage inductance measurement value Lsl.

[0077] In this embodiment, the single-phase pulse vibration experiment with DC bias on the asynchronous motor specifically includes the following steps:

[0078] Step S31, applying a single-phase excitation pulse voltage with a DC bias to any two-phase winding of the stator, and performing a pulse test with a DC bias, wherein the excitation waveform is as follows: Fig. 9 shown.

[0079] Step S32, gradually increasing the duty cycle of the excitation pulse voltage applied to the stator until the current sampling average value in step S21 reaches the core saturation current Isat.

[0080] Step S33: According to the current sampling value obtained in step S32, the imaginary part of the input AC impedance of the asynchronous motor is measured as the stator leakage inductance measurement value Lsl.

[0081] Then, step S4 is executed to calculate the rotor leakage inductance measurement value Lrl. In step S4, the rotor leakage inductance measurement value Lrl is calculated according to the stator-rotor total leakage inductance measurement value Ll and the stator leakage inductance measurement value Lsl.

[0082] Specifically, the calculation formula of the rotor leakage inductance measurement value is as follows:

[0083] Lrl = Ll – Lsl (1)

[0084] Wherein, L1 is the measured value of the total stator-rotor leakage inductance, and Lsl is the measured value of the stator leakage inductance.

[0085] In practical applications, the present invention provides an offline identification method for leakage inductance of an asynchronous motor using core saturation, which is based on a three-phase asynchronous motor and an inverter connected to the input end of the asynchronous motor, wherein the asynchronous motor includes a rotor and a stator with a multi-phase winding.

[0086] In step S11, Fig.10 As shown, the left module represents the inverter PWM modulation and current sampling ADC and related coordinate transformation calculations inside the inverter, such as three-phase PWM inverter output and UV two-phase current sampling.

[0087] In step S11, the coordinate transformation of current and voltage is performed using equal amplitude Clarke transformation. Taking current as an example, as shown in formula (2):

[0088]

[0089] Among them, Ialpha and Ibeta are the current vectors collected by the inverter on the motor, and iu, iv, and iw are the instantaneous values ​​of the line current collected by the inverter on the phase lines of the three-phase motor.

[0090] In step S12, the motor equivalent impedance Z is calculated as follows:

[0091]

[0092] Among them, Ualpha and Ubeta are the instantaneous values ​​of the voltage vector applied by the inverter to the motor, Ialpha and Ibeta are the instantaneous values ​​of the current vector collected by the inverter on the motor, and imag(Z) and real(Z) are the real and imaginary parts of the motor equivalent impedance respectively.

[0093] In step S13, the AC excitation voltage applied in step S11 is slowly increased. In this embodiment, the increase starts from 0.3 times of the rated voltage of the motor, which can ensure that the motor core operates in a non-saturated state.

[0094] In step S21, the equivalent circuit model of the asynchronous motor is as follows: Fig.11 As shown,

[0095] In step S21, since the mutual inductance Lm of the asynchronous motor is generally much larger than the stator leakage inductance and the rotor leakage inductance, it can be generally considered that when the magnetic core is unsaturated, the Lm branch of the equivalent circuit model is open. The equivalent circuit model of the asynchronous motor based on Fig.12 shown.

[0096] In step S22, in order to keep the current DC bias at zero, it is necessary to generate a positive and negative alternating voltage pulse group to drive the motor winding, and its excitation waveform is as follows: Figure 8 As shown, the input to the winding is as follows Figure 8 The pulse voltage shown can be used to calculate the total resistance Rs+Rr and the total leakage inductance Ll by sampling the current. The number of pulses in each pulse group can be adjusted according to the DC bus voltage of the inverter and the rated current value of the motor. Generally, 3 to 7 pulses are taken, and the last pulse of each pulse group is used as the sample for the final calculation.

[0097] In step S22, the voltage excitation duty cycle is gradually increased. In order to fully utilize the range of the sampling unit, this embodiment uses 80% of the saturation current value Isat as the target. If the maximum value of the current sampling value is greater than or equal to 0.8*Isat in the last cycle of each pulse group, the duty cycle of the pulse voltage excitation is stopped.

[0098] In step S23, the stator rotor total leakage inductance measurement value L1 is calculated as shown in formulas (4) and (5):

[0099]

[0100]

[0101] Among them, Udc represents the DC bus voltage of the inverter, dIup and dIdown represent the change values ​​of the current in the rising stage and the falling stage of the current in the pulse oscillation experiment respectively, and I represents the last pulse in the pulse oscillation experiment (the last pulse cycle in each direction is used as the sample in the pulse oscillation experiment).

[0102] In step S31, a single-phase pulse test with a DC bias is applied to any two-phase winding of the stator, and the excitation waveform is as follows: Fig. 9 As shown, the input to the winding is as follows Fig. 9 The stator leakage inductance Lsl can be calculated by sampling the current. Since most asynchronous motors use cold-rolled silicon steel sheets as core materials, and the saturation characteristics of silicon steel are relatively hard, when magnetic saturation occurs, its dynamic magnetic permeability is close to the vacuum magnetic permeability. At this time, the Lm branch in the equivalent circuit model is equivalent to a short circuit, and the equivalent circuit model of the asynchronous motor when magnetic saturation occurs is as follows: Fig.13 shown.

[0103] In step S33, the stator leakage inductance measurement value Lsl is calculated using equations such as formulas (6) and (7):

[0104]

[0105]

[0106] Among them, Udc represents the DC bus voltage of the inverter, dIup and dIdown represent the change values ​​of the current in the rising and falling stages of the current in the pulse vibration experiment respectively, and Ibias represents the bias current, that is, the average value of the current sampling, which is equal to the motor core saturation current Isat in the experiment.

[0107] It can be seen that the present invention provides an asynchronous motor leakage inductance offline identification method. First, an improved no-load running experiment is used to obtain the bias current corresponding to the core saturation, which is used as the core saturation current. Then, a single-phase pulse vibration experiment without DC bias and a single-phase pulse vibration experiment with DC bias are performed. Then, the stator leakage inductance and rotor leakage inductance of the asynchronous motor are obtained according to the circuit model of the core in the unsaturated state and the saturated state. This is beneficial to improving the offline identification accuracy of the asynchronous motor and improving the effect of sensorless vector control of the asynchronous motor.

[0108] Furthermore, the present invention uses a circuit model equation to independently calculate the rotor leakage inductance of the asynchronous motor, avoiding the use of empirical formulas to directly infer the rotor leakage inductance from the stator leakage inductance, and has high identification accuracy.

[0109] In addition, the present invention uses an improved asynchronous motor no-load experiment to infer the saturation current of the motor core, without the need for the user to provide prior information on the saturation current, further reducing the dependence of motor identification on user input parameters.

[0110] It should be noted that the above are only preferred embodiments of the present invention, but the design concept of the invention is not limited thereto, and any non-substantial modifications made to the present invention using this concept also fall within the protection scope of the present invention.

Claims

1. A method for offline identification of leakage inductance of an asynchronous motor, characterized in that: include; Obtaining a core saturation current, including performing a no-load running experiment on the asynchronous motor, and obtaining a bias current amplitude corresponding to the core saturation as the core saturation current; Obtain the sum of the stator leakage inductance and the rotor leakage inductance in the asynchronous motor model to obtain the measured value of the total stator and rotor leakage inductance; Calculating the stator leakage inductance measurement value in the asynchronous motor model under the core saturation current bias, including performing a single-phase pulse vibration experiment with a DC bias on the asynchronous motor, and measuring the imaginary part of the input AC impedance of the asynchronous motor under the core saturation current bias as the stator leakage inductance measurement value; The rotor leakage inductance measurement value is calculated; The no-load running experiment of the asynchronous motor specifically comprises the following steps: Step S11, applying low voltage AC excitation to the stator according to its rated operating frequency; Step S12, collecting the three-phase current of the stator three-phase winding when reaching a steady state under low-voltage AC excitation in step S11 through the corresponding inverter, and calculating the equivalent impedance of the asynchronous motor; Step S13, slowly increasing the AC excitation voltage applied to the stator in step S11, and measuring the equivalent impedance of the asynchronous motor in a metastable state; Step S14: when the imaginary part of the asynchronous motor equivalent impedance reaches a maximum value, the three-phase current amplitude measured by the inverter is used as the core saturation current.

2. The method according to claim 1, characterized in that The step of obtaining the sum of the stator leakage inductance and the rotor leakage inductance in the asynchronous motor model includes: A single-phase pulse vibration experiment is carried out on the asynchronous motor. The imaginary part of the input AC impedance of the asynchronous motor is measured without DC current bias as the total leakage inductance measurement value of the stator and rotor.

3. The method according to claim 2, characterized in that The single-phase pulse vibration experiment on the asynchronous motor specifically includes the following steps: Step S21, applying a single-phase excitation pulse voltage to any two-phase windings of the stator to perform a pulse test; Step S22, gradually increasing the duty cycle of the excitation pulse voltage applied to the stator until the current sampling value in step S21 reaches a suitable value lower than the core saturation current; wherein 80% of the saturation current value Isat is used as the target; if the maximum value of the current sampling value in the last cycle of each pulse group is greater than or equal to 0.8xIsat, then stop increasing the duty cycle of the pulse voltage excitation; Step S23: According to the current sampling value obtained in step S22, the imaginary part of the input AC impedance of the asynchronous motor is measured as the total leakage inductance measurement value of the stator and rotor.

4. The method according to claim 3, characterized in that The single-phase pulse vibration experiment with a DC bias on the asynchronous motor specifically includes the following steps: Step S31, applying a single-phase excitation pulse voltage with a DC bias to any two-phase windings of the stator to perform a pulse test with a DC bias; Step S32, gradually increasing the duty cycle of the excitation pulse voltage applied to the stator until the current sampling average value in the step S21 reaches the core saturation current; Step S33: According to the current sampling value obtained in step S32, the imaginary part of the input AC impedance of the asynchronous motor is measured as the stator leakage inductance measurement value.

5. The method according to any one of claims 1 to 4, characterized in that: The calculation to obtain the rotor leakage inductance measurement value includes: The rotor leakage inductance measurement value is calculated based on the stator-rotor total leakage inductance measurement value and the stator leakage inductance measurement value.

6. The method according to claim 5, characterized in that: The rotor leakage inductance measurement is calculated as follows: Lrl = Ll – Lsl Wherein, L1 is the measured value of the total leakage inductance of the stator and rotor, and Ls1 is the measured value of the stator leakage inductance.

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