An asynchronous motor speed regulation method and system based on an improved super-twisting sliding mode algorithm

Abstract

This invention relates to the field of asynchronous motor control technology, specifically to an asynchronous motor speed control method and system based on an improved Super-Twisting sliding mode algorithm. The method includes: (1) deriving the fourth-order nonlinear differential equation of a three-phase squirrel-cage asynchronous motor in a rotating coordinate system d-q based on rotor magnetic field orientation theory; (2) designing a linear sliding surface based on the error between the set speed and the feedback speed; (3) using the first-order differential equation of rotor speed in step (1) and the linear sliding surface described in step (2), and introducing a variable proportional differential term based on the traditional Super-Twisting sliding mode algorithm to design a fast Super-Twisting sliding mode speed controller; (4) constructing a variable exponential switching function to replace the sign function in the fast Super-Twisting sliding mode speed controller described in step (3), thus completing the design of the improved Super-Twisting sliding mode speed controller. This solution effectively solves the problems of slow response speed and poor control accuracy in existing systems, thereby improving the overall robustness of asynchronous motor control.

Description

Technical Field

[0001] This invention relates to the field of asynchronous motor control technology, and in particular to an asynchronous motor speed regulation method or system based on an improved Super-Twisting sliding mode algorithm. Background Technology

[0002] An asynchronous motor, also known as an induction motor, is an AC motor that converts electromechanical energy into mechanical energy by generating electromagnetic torque through the interaction of a rotating magnetic field in the air gap and the induced current in the rotor windings. Asynchronous motors are widely used in electric vehicles and industrial production due to their simple structure, ease of manufacture, low cost, reliable operation, and convenient maintenance. However, in practical applications, asynchronous motors are often affected by uncertainties such as parameter perturbations and external load disturbances. Furthermore, traditional PI controllers are insufficient to meet the speed control and precision requirements of modern asynchronous motor systems, posing a challenge to high-performance control of asynchronous motors.

[0003] To improve the speed control performance of asynchronous motors, sliding mode control has received widespread attention in practical applications due to its ability to overcome system parameter uncertainties and its strong robustness. However, due to the discreteness of the reaching law in sliding mode control, chattering is an unavoidable problem. To address this issue, a common solution is to combine the Super-Twisting algorithm with sliding mode control to form Super-Twisting sliding mode control. This combination retains the advantages of the original sliding mode control algorithm in overcoming system parameter uncertainties and providing strong robustness, while also mitigating inherent chattering.

[0004] However, when the motor is actually started in the system, the ordinary Super-Twisting sliding mode control still has a slow response speed. Furthermore, due to the existence of the sign function, the non-smoothness of the switching during high-frequency speed switching can lead to a slight chattering problem in the system under ordinary Super-Twisting sliding mode control.

[0005] Therefore, a new technical solution is urgently needed to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of the prior art and provide an asynchronous motor speed control method and system based on an improved Super-Twisting sliding mode algorithm, so as to solve the technical problems of slow response speed when the motor starts and weak chattering when the speed is switched at high frequency in the prior art.

[0007] The above objectives are achieved through the following technical solutions:

[0008] A method for speed control of an asynchronous motor based on an improved Super-Twisting sliding mode algorithm includes:

[0009] Step (1) According to the rotor magnetic field orientation theory, the fourth-order nonlinear differential equation of the three-phase squirrel-cage asynchronous motor is obtained in the rotating coordinate system dq.

[0010] Step (2) Design a linear sliding surface based on the error between the set rotational speed and the feedback rotational speed;

[0011] Step (3) uses the first-order differential equation of rotor speed in step (1) and the linear sliding surface described in step (2), and introduces a variable proportional differential term based on the traditional Super-Twisting sliding mode algorithm to design a fast Super-Twisting sliding mode speed controller.

[0012] Step (4) Construct a variable exponential switching function to replace the sign function in the fast Super-Twisting sliding mode speed controller described in step (3), thus completing the design of the improved Super-Twisting sliding mode speed controller.

[0013] Furthermore, the fourth-order nonlinear differential equation of the three-phase squirrel-cage asynchronous motor described in step (1) is expressed as follows:

[0014]

[0015] Where h = 1 / σL S ; g = 1 / T r =L r / R r ;

[0016] i sd i sq The stator current components are in the d and q coordinate system; u sd u sq R represents the stator voltage components in the d and q coordinate systems. s R r These are the stator resistance and rotor resistance, respectively; L s L r These are the stator self-inductance and the rotor self-inductance, respectively; L m Mutual inductance; ψ r For rotor flux linkage; n p ω is the pole pair number; J is the moment of inertia; r ω is the rotor speed; ω1 is the synchronous speed; T L This represents the load torque.

[0017] Furthermore, the expression for the linear sliding surface mentioned in step (2) is as follows:

[0018]

[0019] Among them, is the set rotational speed, ω r is the feedback rotational speed.

[0020] Furthermore, the expression of the traditional Super-Twisting sliding mode algorithm described in step (3) is as follows:

[0021]

[0022] Among them, λ and α are adjustment coefficients;

[0023] Then the expression of the fast Super-Twisting sliding mode speed controller is as follows:

[0024]

[0025] Among them, k is an adjustment coefficient, and the system response speed can be improved by adjusting the value of k.

[0026] Furthermore, the expression of the variable exponent switching function described in step (4) is as follows:

[0027]

[0028] Among them, n is an adjustable exponent, and the adjustment range is 0 < n < 1. The smaller the value of n, the more stable the system rotational speed and the higher the control accuracy;

[0029] Then the expression of the improved Super-Twisting sliding mode speed controller is as follows:

[0030]

[0031] An asynchronous motor speed regulation system based on an improved Super-Twisting sliding mode algorithm includes:

[0032] A speed controller module, which is used to design a linear sliding mode surface according to the error between the set rotational speed and the feedback rotational speed, and complete the design of the speed loop by using the improved Super-Twisting sliding mode algorithm based on the linear sliding mode surface.

[0033] A current controller module, which adopts PI control with voltage feedforward decoupling; <>

[0034] A pulse width modulation module, which is used to realize inversion by controlling the on and off of six switching devices in a three-phase full-bridge circuit after receiving the SVPWM control signal;

[0035] The rotor flux linkage phase angle identification module uses a voltage model to obtain the current rotor flux linkage phase information after arctangent transformation based on the rotor flux linkage components along the αβ axis.

[0036] Furthermore, the pulse width modulation module achieves inversion by controlling the on / off state of six switching devices in the three-phase full-bridge circuit. Specifically, the stator voltage reference value output from the voltage loop is input to the pulse width modulation module, and the inversion is achieved by controlling the on / off state of the six switching devices in the three-phase full-bridge circuit using the space vector pulse width modulation method, including:

[0037] Sector determination is performed based on the stator voltages on the α and β axes;

[0038] Calculate the working time of the main vector and sub-vector for each sector;

[0039] Calculate the switching time for each sector vector.

[0040] Furthermore, the rotor flux linkage phase angle identification module employs a voltage model, and obtains the current rotor flux linkage phase information after arctangent transformation based on the rotor flux linkage components along the αβ axis, specifically as follows:

[0041] After coordinate transformation, the traditional voltage model expression under the αβ axis is:

[0042]

[0043] in, The rotor flux is estimated under the α-axis. The rotor flux linkage is estimated under the β axis;

[0044] Based on the rotor flux linkage components obtained under the αβ axis, the phase information of the current rotor flux linkage can be obtained after arctangent transformation. Then, this information can be transmitted to the Park transformation to realize the transformation between the rotating coordinate system and the stationary coordinate system.

[0045] This invention provides an asynchronous motor speed control method based on an improved Super-Twisting sliding mode algorithm, which effectively solves the problems of slow response speed and poor control accuracy in existing systems, thereby improving the robustness of the overall asynchronous motor control. As an improved Super-Twisting sliding mode speed controller, it retains the advantages of the traditional Super-Twisting sliding mode controller, and only requires adjusting one system parameter value to improve the system response speed. Furthermore, to address the system chattering problem caused by the sign function in the traditional Super-Twisting sliding mode controller, a variable exponential switching function is constructed, which solves the inherent chattering while also improving the system's control accuracy. Attached Figure Description

[0046] Figure 1The flowchart is a method for speed control of an asynchronous motor based on an improved Super-Twisting sliding mode algorithm as described in this invention.

[0047] Figure 2 This is a structural block diagram of an asynchronous motor speed control system based on an improved Super-Twisting sliding mode algorithm, as described in this invention.

[0048] Figure 3 This is a schematic diagram of the speed controller structure in the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention;

[0049] Figure 4 This is the asynchronous motor parameter table in the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention;

[0050] Figure 5 The speed comparison response curves are shown for three different control strategies in the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention.

[0051] Figure 6 The graph shows the speed error comparison response curves for three different control strategies in the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention.

[0052] Figure 7 The graph shows the response curves of sudden speed changes for three different control strategies in the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention.

[0053] Figure 8 This is a comparison of the response curves of sudden loads for three different control strategies in an asynchronous motor speed control method based on an improved Super-Twisting sliding mode algorithm, as described in this invention. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. The described embodiments are merely some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] like Figure 1 As shown, an asynchronous motor speed control method based on an improved Super-Twisting sliding mode algorithm is proposed to improve system response speed and control accuracy, including the following steps:

[0056] Step (1) According to the rotor magnetic field orientation theory, the fourth-order nonlinear differential equation of the three-phase squirrel-cage asynchronous motor is obtained in the rotating coordinate system dq.

[0057] Step (2) Design a linear sliding surface based on the error between the set rotational speed and the feedback rotational speed;

[0058] Step (3) utilizes the first-order differential equation of rotor speed in step (1) and the linear sliding surface described in step (2), and introduces a variable proportional differential term based on the traditional Super-Twisting sliding mode algorithm to design a fast Super-Twisting sliding mode speed controller, thereby improving the system response speed;

[0059] Step (4) constructs a variable exponential switching function to replace the sign function in the fast Super-Twisting sliding mode speed controller described in step (3), thus completing the design of the improved Super-Twisting sliding mode speed controller; it retains the advantage of S3 speed while reducing the chattering problem inherent in sliding mode control, thereby improving the system control accuracy.

[0060] Specifically, the fourth-order nonlinear differential equation of the three-phase squirrel-cage asynchronous motor described in step (1) of this embodiment is expressed as follows:

[0061]

[0062] Where h = 1 / σL S ; g = 1 / T r =L r / R r ;

[0063] i sd i sq The stator current components are in the d and q coordinate system; u sd u sq R represents the stator voltage components in the d and q coordinate systems. s R r These are the stator resistance and rotor resistance, respectively; L s L r These are the stator self-inductance and the rotor self-inductance, respectively; L m Mutual inductance; ψ r For rotor flux linkage; n p ω is the pole pair number; J is the moment of inertia; r ω is the rotor speed; ω1 is the synchronous speed; T L This represents the load torque.

[0064] The expression for the linear sliding surface in step (2) of this embodiment is as follows:

[0065]

[0066] Among them, is the set rotational speed, ω r is the feedback rotational speed.

[0067] The expression of the traditional Super-Twisting sliding mode algorithm described in step (3) of this embodiment is as follows:

[0068]

[0069] Among them, λ and α are adjustment coefficients;

[0070] Then the expression of the fast Super-Twisting sliding mode speed controller is as follows:

[0071]

[0072] Among them, k is an adjustment coefficient, and the system response speed can be improved by adjusting the value of k.

[0073] Since the existence of the sign function during high-frequency switching of the system will bring a weak chattering problem, in order to improve the system control accuracy, a variable exponent switching function is constructed.

[0074] Specifically, the expression of the variable exponent switching function described in step (4) of this embodiment is as follows:

[0075]

[0076] Among them, n is an adjustable exponent, and the adjustment range is 0 < n < 1. The smaller the value of n, the more stable the system rotational speed and the higher the control accuracy;

[0077] Replacing the above-designed function with the traditional sign function, the expression of the improved Super-Twisting sliding mode speed controller is as follows:

[0078]

[0079] As Figure 2 shown, in addition, this solution also designs an asynchronous motor speed regulation system based on the improved Super-Twisting sliding mode algorithm to implement the above-mentioned asynchronous motor speed regulation method based on the improved Super-Twisting sliding mode algorithm. This system includes:

[0080] As Figure 3As shown, the speed controller module is used to design a linear sliding surface based on the error between the set speed and the feedback speed, and to complete the design of the speed loop using an improved Super-Twisting sliding mode algorithm based on the linear sliding surface, thereby improving the system response speed and control accuracy.

[0081] The current controller module employs PI control with voltage feedforward decoupling;

[0082] The pulse width modulation module is used to achieve voltage modulation by controlling the on and off of six switching devices (thyristor switches in the full-bridge inverter) in the three-phase full-bridge circuit after receiving the SVPWM control signal.

[0083] The rotor flux linkage phase angle identification module uses a voltage model to obtain the current rotor flux linkage phase information based on the rotor flux linkage components along the αβ axis after an arctangent transformation. After coordinate transformation, the traditional voltage model expression along the αβ axis is:

[0084]

[0085] in, The rotor flux is estimated under the α-axis. The rotor flux linkage is estimated under the β axis;

[0086] Based on the rotor flux linkage components obtained under the αβ axis, the phase information of the current rotor flux linkage can be obtained after arctangent transformation. Then, this information can be transmitted to the Park transformation to realize the transformation between the rotating coordinate system and the stationary coordinate system.

[0087] It should be noted that the asynchronous motor parameters in this embodiment are as follows: Figure 4 As shown.

[0088] In this embodiment, the pulse width modulation module achieves inversion by controlling the on / off state of six switching devices in the three-phase full-bridge circuit. Specifically, the stator voltage reference value output from the voltage loop is input to the pulse width modulation module, and the inversion is achieved by controlling the on / off state of the six switching devices in the three-phase full-bridge circuit using the space vector pulse width modulation method. This includes:

[0089] Sector determination is performed based on the stator voltages on the α and β axes;

[0090] Calculate the working time of the main vector and sub-vector for each sector;

[0091] Calculate the switching time for each sector vector.

[0092] To verify the effectiveness of the controller, a simulation model of asynchronous motor vector control was built in the MATLAB / Simulink platform.

[0093] Experiments have shown that, under the same data conditions:

[0094] like Figures 5-8 As shown, by comparison, the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention can improve the system response speed.

[0095] like Figure 6 As shown, by comparison, the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention can improve the system control accuracy.

[0096] like Figure 8 As shown, by comparison, the asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm described in this invention can be seen to retain the advantages of the original algorithm and also increase the overall system robustness.

[0097] It is evident that this invention can improve the control accuracy of asynchronous motors under vector control and achieve accurate orientation of the rotor magnetic field.

[0098] The above description is merely illustrative of the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for speed control of an asynchronous motor based on an improved Super-Twisting sliding mode algorithm, characterized in that, including Step (1): According to the rotor magnetic field orientation theory, in the rotating coordinate system d-q, obtain the fourth-order nonlinear differential equation of the three-phase squirrel-cage asynchronous motor; Step (2): Design a linear sliding surface based on the error between the set speed and the feedback speed; Step (3) utilizes the first-order differential equation of rotor speed from step (1) and the linear sliding surface described in step (2), and introduces a variable proportional differential term based on the traditional Super-Twisting sliding mode algorithm to design a fast Super-Twisting sliding mode speed controller; the expression of the linear sliding surface described in step (2) is as follows: , in, To set the rotation speed, For feedback rotational speed; The expression of the traditional Super-Twisting sliding mode algorithm described in Step (3) is as follows: ， in, , This is the adjustment coefficient; Then the expression of the fast Super-Twisting sliding mode speed controller is as follows: ， in, , This is an adjustment coefficient, which can be adjusted... Values ​​are used to improve system response speed; Step (4): Construct a variable exponent switching function to replace the sign function in the fast Super-Twisting sliding mode speed controller described in Step (3), and complete the design of the improved Super-Twisting sliding mode speed controller; The expression of the variable exponent switching function described in Step (4) is as follows: ， where n is an adjustable exponent, and the adjustment range is 0 < n < 1. The smaller the value of n, the more stable the system speed and the higher the control accuracy; Then the expression of the improved Super-Twisting sliding mode speed controller is as follows: 。 2. The asynchronous motor speed control method based on the improved Super-Twisting sliding mode algorithm according to claim 1, characterized in that, The fourth-order nonlinear differential equation of the three-phase squirrel-cage asynchronous motor described in Step (1) is expressed as follows: ， in, ; , These are the stator current components in the d and q coordinate systems. , The stator voltage components are in the d and q coordinate system. , These are the stator resistance and the rotor resistance, respectively. , These are the stator self-inductance and the rotor self-inductance, respectively. Mutual induction; For rotor flux linkage; It is the extreme logarithm; It is the moment of inertia; This refers to the rotor speed; Synchronous speed; This represents the load torque.

3. An asynchronous motor speed control system based on an improved Super-Twisting sliding mode algorithm, used to implement the asynchronous motor speed control method based on an improved Super-Twisting sliding mode algorithm as described in any one of claims 1-2, characterized in that, including: A speed controller module, which is used to design a linear sliding surface based on the error between the set speed and the feedback speed, and complete the design of the speed loop by using the improved Super-Twisting sliding mode algorithm on the basis of the linear sliding surface; A current controller module, which adopts PI control with voltage feedforward decoupling; A pulse width modulation module, which is used to realize inversion by controlling the on and off of six switching devices in the three-phase full-bridge circuit after receiving the SVPWM control signal; The rotor flux linkage phase angle identification module uses a voltage model and is based on... The rotor flux linkage component of the shaft is transformed by arctangent to obtain the current rotor flux linkage phase information.

4. The asynchronous motor speed control system based on the improved Super-Twisting sliding mode algorithm according to claim 3, characterized in that, In the pulse width modulation module, inversion is realized by controlling the on and off of six switching devices in the three-phase full-bridge circuit. Specifically, the stator voltage reference value output by the voltage loop is input into the pulse width modulation module, and the on and off of six switching devices in the three-phase full-bridge circuit are controlled by the space vector pulse width modulation method to realize inversion, including: According to the stator shaft and Sector determination is performed based on the voltage of the shaft; Calculate the working time of the main vector and the sub-vector in each sector; Calculate the switching time of the vector in each sector.

5. The asynchronous motor speed control system based on the improved Super-Twisting sliding mode algorithm according to claim 4, characterized in that, The rotor flux linkage phase angle identification module uses a voltage model, based on... The rotor flux linkage component of the shaft, after undergoing arctangent transformation, yields the current rotor flux linkage phase information, specifically: After coordinate transformation, The traditional on-axis voltage model expression is: ， in, In order to be in The rotor flux estimated under the shaft, In order to be in The rotor flux estimated under the shaft; According to the above The rotor flux component obtained from the shaft can be transformed by arctangent to obtain the phase information of the current rotor flux. This information can then be transmitted to the Park transformation to realize the transformation between the rotating coordinate system and the stationary coordinate system.

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