A permanent magnet synchronous motor control method and system

Abstract

The present invention discloses a control method for a permanent magnet synchronous motor, which includes the following steps: S1. Taking the difference between the mechanical angular velocity expectation value ω * and the current mechanical angular velocity value of the rotor as the system state variable x; S2. Detecting whether the system is far from the sliding surface, that is, whether |s| is greater than 1. If the detection result is yes, the power term exponent α in the reaching law #imgabs0# is 0. Otherwise, the power term exponent α in the reaching law #imgabs1# takes a value of: 0 < α < 1; S3. Based on the reaching law #imgabs2#, constructing the expected q-axis current i q * of the permanent magnet synchronous motor in the current d-q axis coordinate system, and using the expected q-axis current i q * to control the input of the current q-axis current of the permanent magnet synchronous motor. The present invention proposes a new reaching law, selects different power term exponents according to the distance from the sliding surface, introduces the system state variable into the exponent term, constructs a new reaching law with variable exponent power terms and variable exponent term coefficients, and effectively weakens the chattering of the system while maintaining a relatively fast reaching speed of the control system.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor control, and more specifically, the present invention relates to a permanent magnet synchronous motor control method and system. Background Art

[0002] Permanent Magnet Synchronous Motor (PMSM) is widely used in various industries due to its simple structure, high power density, and good dynamic performance. However, the permanent magnet synchronous motor is a typical nonlinear multivariable coupling system. In the actual operation of the motor, parameters such as magnetic flux and dq axis inductance change due to magnetic saturation. The uncertainty caused by these changes has a great impact on the control performance. In addition, different external environments will also affect the stability of the drive system. Traditional PID control relies on the accuracy of the system model, and when the internal parameters of the system change or the system is subjected to external disturbances, it will be difficult to meet the requirements of high-precision control systems. Therefore, it is necessary to adopt a method with better control effect to solve the above problems.

[0003] Sliding mode control is widely used in the field of motor control because of its strong robustness, fast response speed, and insensitivity to internal parameter perturbations and external disturbances of the system. However, the chattering problem existing in traditional sliding mode control restricts the performance of sliding mode control. In order to solve the chattering problem of sliding mode control, solutions have been proposed from many different angles. For example, the concepts of "quasi-sliding mode" and "boundary layer" are introduced in the design of sliding mode control. In addition, saturation function is used instead of switching function to effectively avoid or weaken chattering. In addition, there are sliding mode control methods based on reaching law. Among these chattering reduction methods, the reaching law method can ensure the dynamic characteristics and stability of the system, but the traditional exponential and power reaching laws cannot achieve fast convergence to the sliding surface while avoiding chattering. Summary of the invention

[0004] The present invention provides a permanent magnet synchronous motor control method, aiming to improve the above-mentioned problem.

[0005] The present invention is implemented as follows: a permanent magnet synchronous motor control method, the method specifically comprising the following steps:

[0006] S1, the mechanical angular velocity is the expected value ω * and the current rotor mechanical angular velocity value z 1 The difference is taken as the system state variable x;

[0007] S2, whether the detection system is far away from the sliding surface, that is, whether |s| is greater than or equal to 1. If the detection result is yes, then the approach law The power term index α in is 0, otherwise, the reaching law The power term exponent α in is: 0<α<1;

[0008] S3, based on the reaching law The expected q-axis current i of the permanent magnet synchronous motor in the dq-axis coordinate system is constructed by using the ESO observation value q * , the expected q-axis current i q * To control the current q-axis current input of the permanent magnet synchronous motor.

[0009] Furthermore, the law of approach The specific expression of is as follows:

[0010]

[0011] Among them, x is the system state variable, λ and β are constants greater than zero, k is a constant greater than zero, s represents the sliding surface, ε is a constant greater than zero, α represents the power term exponent, when |s|>=1, α=0, when |s|<1, 0<α<1.

[0012] Furthermore, the expected q-axis current i q * The calculation formula is as follows:

[0013]

[0014] in, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia; B is the viscous friction coefficient, D is the comprehensive disturbance of the system; c is the sliding surface coefficient, c>0, and s represents the sliding surface.

[0015] Furthermore, before step S3, the method further includes:

[0016] S4. Obtain the observed value z of the comprehensive disturbance 2 (t), the observed value z 2 (t) is the comprehensive disturbance D of the system. Further, the observation value z of the comprehensive disturbance 2 (t) is calculated based on the following formula:

[0017]

[0018] Among them, e 1 (t) is the error between the observed mechanical angular velocity and the current actual mechanical angular velocity, z 1 (t) is the observed value of mechanical angular velocity, z 2 (t) is the total disturbance value of observation, β 1 , β 2 is the observer gain coefficient, β 3>0 is the hyperbolic tangent function adjustment parameter, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia, B is the viscous friction coefficient.

[0019] Furthermore, the current rotor mechanical angular velocity value is the current rotor mechanical angular velocity observation value z 1 Or the current rotor mechanical angular velocity detection value ω m .

[0020] The present invention is implemented as follows: a permanent magnet synchronous motor control system, the system comprising:

[0021] Permanent magnet synchronous motor, sliding mode controller, observer, q-axis PI current regulator, d-axis PI current regulator, and three-phase inverter;

[0022] The detected three-phase current i a 、i b 、i c After CLARK transformation and PARK transformation, we can get the i in the dq axis coordinate system. d 、i q , the current mechanical angular velocity ω of the rotor of the permanent magnet synchronous motor m and the current q-axis current i q Input observer, observer outputs comprehensive disturbance D to sliding mode controller, mechanical angular velocity given value ω * and the mechanical angular velocity observed value z 1 Or the mechanical angular velocity observation value ω m The difference is input to the sliding mode controller, which outputs the expected q-axis current i of the permanent magnet synchronous motor in the dq-axis coordinate system. q * , let the desired d-axis current i d * =0, the expected q-axis current i q * With the current q-axis current i q The difference is used as the input of the q-axis PI current regulator, and the desired d-axis current i d * and d-axis current i d The difference is used as the input of the d-axis current regulator, and the d- and q-axis current regulators output u in the rotating coordinate system. d 、u q As the input of PARK inverse transformation, the output stator voltage u α 、u β , as the reference voltage vector generated by SVPWM, generates switching signals acting on the three-phase inverter, and finally drives the permanent magnet synchronous motor to operate.

[0023] Furthermore, the sliding mode controller integrates the desired q-axis current i q * The calculation model is as follows:

[0024]

[0025] in, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia; B is the viscous friction coefficient, D is the comprehensive disturbance of the system; c is the sliding surface coefficient, c>0.

[0026] Convergence Law The specific expression of is as follows:

[0027]

[0028] Among them, x is the system state variable, λ and β are constants greater than zero, k is a constant greater than zero, s represents the sliding surface, ε is a constant greater than zero, α represents the power term exponent, when |s|>=1, α=0, when |s|<1, 0<α<1.

[0029] Furthermore, the observer integrates the state observation equation, and calculates the observation value z of the comprehensive disturbance based on the state observation equation. 2 (t), the observed value of the integrated disturbance z 2 (t) is the comprehensive disturbance D, and the state observation equation is as follows:

[0030]

[0031] Among them, e 1 (t) is the error between the observed mechanical angular velocity and the current actual mechanical angular velocity, z 1 (t) is the observed value of mechanical angular velocity, z 2 (t) is the total disturbance value of observation, β 1 , β 2 is the observer gain coefficient, β 3 Tuning parameters for the hyperbolic tangent function, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia, B is the viscous friction coefficient.

[0032] The present invention proposes a new convergence law, selects different power term exponents according to the distance from the sliding mode surface, introduces system state variables in the exponential term, and constructs a new convergence law with variable exponential power terms and variable exponential term coefficients, which effectively weakens the system jitter while maintaining a faster convergence speed of the control system; in addition, an extended state observer based on the hyperbolic tangent function is designed to realize real-time observation and precise tracking of the motor angular velocity and load disturbance, and then feed-forwards the observed values ​​to the sliding mode controller for compensation, which reduces the switching gain of the controller, weakens the jitter, and improves the dynamic performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flow chart of a permanent magnet synchronous motor control method provided by an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the structure of a permanent magnet synchronous motor control system provided by an embodiment of the present invention;

[0035] Figure 3 A comparison diagram of PMSM simulation speed under traditional PID control and NRLASMC control provided by an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of torque output of PMSM simulation provided in an embodiment of the present invention, wherein (a) is the torque output under traditional PID control, and (b) is the torque output under NRLASMC control;

[0037] Figure 5 A comparison diagram of three-phase current input of PMSM simulation provided by an embodiment of the present invention, wherein (a) is the three-phase input current under traditional PID control, and (b) is the three-phase input current under NRLASMC control;

[0038] Figure 6 The simulated load torque ESO observation result provided by the embodiment of the present invention;

[0039] Figure 7 The simulated angular velocity ESO tracking error provided by the embodiment of the present invention;

[0040] Figure 8 A speed comparison diagram of PMSM starting and speed increase under PID control and NRLASMC control provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The specific implementation modes of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0042] The present invention proposes a new reaching law, selects different power term exponents according to the distance from the sliding surface, introduces system state variables in the exponential term, and constructs a new reaching law with variable exponential power terms and variable exponential term coefficients, which effectively weakens the system chattering while maintaining a faster reaching speed of the control system.

[0043] Figure 1 This is a flow chart of a permanent magnet synchronous motor control method provided by an embodiment of the present invention, and the method specifically comprises the following steps:

[0044] S1, the mechanical angular velocity is the expected value ω * and the current mechanical angular velocity observation value z 1 Or the current mechanical angular velocity observation value ω m The difference is taken as the system state variable x;

[0045] S2, whether the detection system is far away from the sliding surface, that is, whether |s| is greater than or equal to 1. If the detection result is yes, then the approach law The power term index α in is 0, otherwise, the reaching law The power term exponent α in is: 0<α<1;

[0046] Among them, the approach law The specific expression of is as follows:

[0047]

[0048] Among them, x is the system state variable, λ and β are constants greater than zero, k is a constant greater than zero, s represents the sliding surface, ε is a constant greater than zero, α represents the power term exponent, when |s|>=1, α=0, when |s|<1, 0<α<1.

[0049] In order to further suppress system chattering and improve system regulation accuracy, the integral sliding surface s is selected as:

[0050]

[0051] Among them, t represents the current moment, c is the sliding surface coefficient, which is a constant greater than zero, and τ is the time integral variable.

[0052] When |s|≥1, it is considered that the system state variable x is far away from the sliding surface, then the power term exponent α=0, the system state variable |x| is relatively large, and at this time e -β|x| When |s| < 1, that is, the system state variable x approaches the sliding surface, the power term exponent ranges from 0 < α < 1, the system state variable |x| is small, and e -β|x|Approaches 1, the exponential term approaches zero, the power term plays a major role in the approach, and the system has a lower approach speed when approaching the sliding surface. Due to the introduction of the state variable x, the system chattering is further weakened.

[0053] S3, based on the reaching law The expected q-axis current i of the permanent magnet synchronous motor in the dq-axis coordinate system is constructed with ESO q * , the expected q-axis current i q * To control the current q-axis current input of the permanent magnet synchronous motor.

[0054]

[0055] in, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia; B is the viscous friction coefficient, D is the comprehensive disturbance of the system, c is the sliding surface coefficient, c>0.

[0056] Establish the equation of the permanent magnet synchronous motor in the dq axis coordinate system, using the expected d axis current i d * =0 control strategy, the PMSM voltage equation is:

[0057]

[0058] Among them, u d 、u q 、i d 、i q are the d-axis and q-axis stator voltage and current respectively, L d , L q are the inductances of the d and q axes respectively, p is the number of pole pairs, R s is the stator resistance, ψ f is the permanent magnet flux, ω m is the rotor mechanical angular velocity.

[0059] The torque T of PMSM in the dq axis coordinate system e The equation is:

[0060] T e =1.5pψ f i q (5)

[0061] The PMSM motion equation is:

[0062]

[0063] Among them, T e 、TL are electromagnetic torque and load torque respectively, J is the moment of inertia, and B is the viscous friction coefficient.

[0064] Substituting equation (5) into equation (6), the motion equation of the permanent magnet synchronous motor can be written as:

[0065]

[0066] Taking into account the influence of system disturbance and system parameter changes, equation (7) can be written as:

[0067]

[0068] Obviously, in formula (6) D is the comprehensive disturbance of the system, which involves the influence of load disturbance and changes in system parameters. where Δ 1 , Δ 2 , Δ 3 For each parameter i q ,ω m and T L The amount of change.

[0069] The speed tracking error is defined as:

[0070] x=ω * -ω m (9)

[0071] ω * It is the mechanical angular velocity given value.

[0072] The derivative of the speed tracking error is:

[0073]

[0074] Then, from equations (1), (2), and (10), we can get the expected q-axis current i q * The expression is as follows:

[0075]

[0076] In an embodiment of the present invention, the present invention also designs an extended state observer based on a hyperbolic tangent function to achieve real-time observation and precise tracking of the motor angular velocity and load disturbance, and then feeds forward the observed value to the sliding mode controller for compensation, thereby reducing the switching gain of the controller, weakening the jitter, and improving the dynamic performance of the system.

[0077] In order to accurately observe the total disturbance D and improve the adaptive and dynamic response capabilities of the extended state observer, a new extended state observation equation based on the hyperbolic tangent function is designed. The observation equation is as follows:

[0078]

[0079] Among them, e 1 (t) is the mechanical angular velocity observation value (z 1 (t)) and the current actual mechanical angular velocity value (ω m ), z 1 (t) is the observed value of mechanical angular velocity, z 2 (t) is the total disturbance value of observation, β 1 , β 2 is the observer gain coefficient, β 3 >0 is a hyperbolic tangent function adjustment parameter, therefore, before step S3, the following is also included:

[0080] S4. Obtain the observed value z of the comprehensive disturbance 2 (t), the observed value z 2 (t) is the comprehensive disturbance D of the system.

[0081] Figure 2 The structure diagram of the permanent magnet synchronous motor control system provided by the embodiment of the present invention is shown. For the convenience of description, only the part related to the embodiment of the present invention is shown. The system includes:

[0082] Permanent magnet synchronous motor (PMSM), sliding mode controller (NRLSMC), observer (ESO), q-axis PI current regulator, d-axis PI current regulator, and three-phase inverter;

[0083] The detected three-phase current i a 、i b 、i c After CLARK transformation and PARK transformation, we can get the i in the dq axis coordinate system. d 、i q ;

[0084] The current mechanical angular velocity ω of the rotor of the permanent magnet synchronous motor m Input observer, observer outputs comprehensive disturbance D to sliding mode controller, mechanical angular velocity given value ω * OR mechanical angular velocity detection value ω m The difference is input to the sliding mode controller, which outputs the expected q-axis current i of the permanent magnet synchronous motor in the dq-axis coordinate system. q * , let the desired d-axis current i d * =0, the expected q-axis current i q * With the current q-axis current i q The difference is used as the input of the q-axis PI current regulator, and the desired d-axis current i d *and d-axis current i d The difference is used as the input of the d-axis current regulator, and the d- and q-axis current regulators output u in the rotating coordinate system. d 、u q As the input of PARK inverse transformation, the output stator voltage u α 、u β , as the reference voltage vector generated by SVPWM, generates switching signals acting on the three-phase inverter, and finally drives the permanent magnet synchronous motor to operate.

[0085] In the embodiment of the present invention, the desired q-axis current i recorded in formula (3) is q * The calculation model of is stored in the sliding mode controller, and the state observation equation recorded in formula (12) is integrated on the observer.

[0086] Stability analysis:

[0087] Let s = z 1 (t)-ω m , then the reachability condition to the sliding mode is:

[0088] Use Lyapunov function to verify the stability of the control system and construct Lyapunov function V:

[0089]

[0090] The Lyapunov stability condition is:

[0091] According to equations (2), (10) and (11), the above equation can be written as

[0092]

[0093] The parameters satisfy ε>0, k>0, 0=<α<1, 0<λ, 0<β. When s→0, According to the Lyapunov function stability theorem, the designed sliding mode controller is asymptotically stable.

[0094] Figure 3 , Figure 4 , Figure 5 They are the simulation comparison diagrams of the speed, output torque and three-phase input current of the NRLASMC control of the present invention and the traditional PID control. It can be clearly seen that the PMSM under the NRLASMC control can reach the steady state quickly and without overshoot, the speed fluctuation is small under the condition of sudden load increase, the steady state recovery time is short, and the control performance is obviously better than the PID control.

[0095] Figure 6 , Figure 7The figures are respectively the ESO torque tracking and angular velocity tracking error result diagrams. It can be seen that the proposed ESO has a fast response speed for observing the given torque, a small observation error, a small angular velocity tracking error, and a fast convergence speed. Figure 8 This is a speed comparison diagram when PMSM is started and accelerated under PID control and NRLASMC control. From the experimental results, it can be seen that the superior control performance of the present invention is further illustrated.

[0096] The present invention has been described exemplarily. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A permanent magnet synchronous motor control method, characterized in that: The method specifically comprises the following steps: S1, the mechanical angular velocity is the expected value ω * The difference between the current rotor mechanical angular velocity value is taken as the system state variable x; S2, whether the detection system is far away from the sliding surface, that is, whether |s| is greater than or equal to 1. If the detection result is yes, then the approach law The power term index α in is 0, otherwise, the reaching law The power term exponent α in is: 0<α<1; S3, based on the reaching law The expected q-axis current i of the permanent magnet synchronous motor in the dq-axis coordinate system is constructed by using the ESO observation value q * , the expected q-axis current i q * To control the current q-axis current input of the permanent magnet synchronous motor; Convergence Law The specific expression of is as follows: Among them, x is the system state variable, λ and β are constants greater than zero, k is a constant greater than zero, s represents the sliding surface, ε is a constant greater than zero, α represents the power term exponent, when |s|>=1, α=0, when |s|<1, 0<α<1.

2. The permanent magnet synchronous motor control method according to claim 1, characterized in that: Expected q-axis current i q * The calculation formula is as follows: in, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia; B is the viscous friction coefficient, D is the comprehensive disturbance of the system; c is the sliding surface coefficient, c>0, s represents the sliding surface, is the reaching law, ω m is the rotor mechanical angular velocity.

3. The permanent magnet synchronous motor control method according to claim 1, characterized in that: Before step S3, the method further includes: S4. Obtain the observation value z2(t) of the comprehensive disturbance, and use the observation value z2(t) as the comprehensive disturbance D of the system.

4. The permanent magnet synchronous motor control method according to claim 3, characterized in that: The observed value of the comprehensive disturbance z2(t) is calculated based on the following formula: Among them, e1(t) is the error between the mechanical angular velocity observation value and the current actual mechanical angular velocity value, z1(t) is the mechanical angular velocity observation value, z2(t) is the observed total disturbance value, β1 and β2 are observer gain coefficients, β3>0 is the hyperbolic tangent function adjustment parameter, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia, B is the viscous friction coefficient, ω m is the rotor mechanical angular velocity, i q is the q-axis stator current.

5. The permanent magnet synchronous motor control method according to claim 4, characterized in that: The current rotor mechanical angular velocity value is the current rotor mechanical angular velocity observation value z1 or the current rotor mechanical angular velocity detection value ω m .

6. A permanent magnet synchronous motor control system, characterized in that: The system comprises: Permanent magnet synchronous motor, sliding mode controller, observer, q-axis PI current regulator, d-axis PI current regulator, and three-phase inverter; The detected three-phase current i a 、i b 、i c After CLARK transformation and PARK transformation, we can get the i in the dq axis coordinate system. d 、i q , the current mechanical angular velocity ω of the rotor of the permanent magnet synchronous motor m and the current q-axis current i q Input observer, observer outputs comprehensive disturbance D to sliding mode controller, mechanical angular velocity given value ω * With the mechanical angular velocity observation value z1 or the mechanical angular velocity detection value ω m The difference is input to the sliding mode controller, which outputs the expected q-axis current i of the permanent magnet synchronous motor in the dq-axis coordinate system. q * , let the desired d-axis current i d * =0, the expected q-axis current i q * With the current q-axis current i q The difference is used as the input of the q-axis PI current regulator, and the desired d-axis current i d * and d-axis current i d The difference is used as the input of the d-axis current regulator, and the d- and q-axis current regulators output u in the rotating coordinate system. d 、u q As the input of PARK inverse transformation, the output stator voltage u α 、u β , as the reference voltage vector generated by SVPWM, generates the switching signal acting on the three-phase inverter, and finally drives the permanent magnet synchronous motor to operate; The sliding mode controller integrates the desired q-axis current i q * The calculation model is as follows: in, p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia; B is the viscous friction coefficient, D is the comprehensive disturbance of the system; c is the sliding surface coefficient, c>0, is the reaching law, ω m is the rotor mechanical angular velocity; The expression of the reaching law s is as follows: Among them, x is the system state variable, λ and β are constants greater than zero, k is a constant greater than zero, s represents the sliding surface, ε is a constant greater than zero, α represents the power term exponent, when |s|>=1, α=0, when |s|<1, 0<α<1.

7. The permanent magnet synchronous motor control system according to claim 6, characterized in that: The observer is integrated with the state observation equation. The observation value z2(t) of the comprehensive disturbance is calculated based on the state observation equation. The observation value z2(t) of the comprehensive disturbance is the comprehensive disturbance D. The specific state observation equation is as follows: Among them, e1(t) is the error between the mechanical angular velocity observation value and the current actual mechanical angular velocity value, z1(t) is the mechanical angular velocity observation value, z2(t) is the observed total disturbance value, β1 and β2 are observer gain coefficients, and β3 is the hyperbolic tangent function adjustment parameter. p is the number of pole pairs, ψ f is the permanent magnet flux, J is the moment of inertia, B is the viscous friction coefficient, ω m is the rotor mechanical angular velocity, i q is the q-axis stator current.

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