Robust Sliding Mode Current Control Method and System for Long-line Drive System of Permanent Magnet Motor

Abstract

The present invention discloses a robust sliding mode current control method and system for a permanent magnet motor long line drive system, belonging to the field of power electronics and power transmission. First, the state variables of the system are sampled, and the reference of the filter inductor current is calculated by using the steady-state characteristics of the filter capacitor voltage dynamic model; then the resonant current component is extracted by using a high-pass filter, and the reference for suppressing the resonance of the filter inductor current is calculated; then the discrete state equation of the filter inductor current is established by using the second-order Taylor expansion method; a discrete sliding mode switching function matrix is designed based on the tracking error of the reference for suppressing the resonance of the filter inductor current; a robust sliding mode control command is obtained based on the discrete sliding mode switching function matrix; the robust sliding mode control command is transformed to the αβ coordinate system through Park inverse transformation and sent to the space vector modulation module to generate pulse signals to be applied to the inverter. The present invention can effectively suppress the resonance phenomenon of the permanent magnet motor long line drive system and improve the robustness of the system to the stator inductance parameter mismatch disturbance.

Description

Technical Field

[0001] The present invention relates to a robust sliding mode current control method and system for a permanent magnet motor long line drive system, belonging to the field of power electronics and electric drive. Background Art

[0002] Due to advantages such as simple structure, compact volume, and high power factor, permanent magnet synchronous motors are widely used in many fields such as industrial manufacturing, energy extraction, and aerospace. In fields such as oilfield drilling and coal transportation, an inverter is connected to a permanent magnet motor through an LC filter and a long cable for power supply, forming a permanent magnet motor long line drive system, aiming to prevent the permanent magnet motor from being damaged due to overvoltage. However, the LC filter and the motor stator inductance form an LCL third-order filtering system, which will cause resonance instability problems.

[0003] The traditional control method for a permanent magnet motor long line drive system is to use proportional-integral control plus resonant damping control. Under complex working conditions, the stator inductance parameters of the permanent magnet motor itself will change, resulting in parameter mismatch. Since the proportional-integral control method in the prior art does not have any control item to resist parameter mismatch, the optimal operating point shifts, thus greatly reducing the robustness to parameter mismatch; in contrast, sliding mode control, as a commonly used non-linear control strategy, has natural robustness to system parameter changes and external disturbances. Nevertheless, existing sliding mode control methods are all designed for a conventional permanent magnet motor drive system without an LC filter. Its current inner loop is designed based on the stator current vector control framework and is prone to resonance instability due to the influence of stator inductance parameter mismatch. In addition, there are essential differences in the structures between a conventional permanent magnet motor drive system and a permanent magnet motor long line drive system, making the existing sliding mode control methods inapplicable to the permanent magnet motor long line drive system.

[0004] The prior art with the publication number CN115118190A discloses a permanent magnet motor intelligent control drive system, including an input module, a human-machine intelligent interaction platform, a voice recognition module, a fault diagnosis module, a fault warning module, a control algorithm module, a motor bench module, and an energy conversion module. Each module is connected through a flexible combination topology structure; at the same time, a permanent magnet motor loss control method based on an improved whale optimization algorithm is provided, including building an FOC control system and inputting motor parameters, collecting motor operation signals, deriving a loss expression, optimizing with the improved whale optimization algorithm, coordinate transformation, and minimum loss control of the motor. Its structure is complex, requires the use of an artificial intelligence interaction platform, has high requirements for computing power and energy, and has a slow control response speed. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a robust sliding mode current control method and system for a permanent magnet motor long-line drive system. By designing a discrete sliding mode switching function matrix based on filtered current resonance suppression reference tracking to obtain a reference sliding mode control command, the resonance instability phenomenon can be effectively suppressed. Combining the switching control command with a variable gain coefficient to calculate a robust sliding mode control command, it solves the problem that the traditional proportional integral control has a reduced robustness and stability due to the deviation of the operating point when the stator inductance parameter is mismatched.

[0006] To achieve the above technical objectives, the present invention provides a robust sliding mode current control method for a permanent magnet motor long-line drive system, and the steps are as follows:

[0007] Collect the system information of the permanent magnet motor long-line drive system at time k using sensors;

[0008] Establish a dynamic model of the filtered capacitor voltage in the dq-axis rotating coordinate system of the permanent magnet motor long-line drive system using the system information, and calculate the reference of the filtered inductor current using the dynamic model of the filtered capacitor voltage;

[0009] Extract the resonant current component in the filtered capacitor voltage, and subtract this resonant current component from the reference of the filtered inductor current to obtain a reference for suppressing the resonant current component of the filtered inductor current without the resonant current component;

[0010] Calculate the discrete sliding mode switching function matrix at time k and time k+1;

[0011] Since the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, the discrete sliding mode switching function matrices at time k and time k+1 are equal, and calculate the reference sliding mode control command;

[0012] Based on the discrete sliding mode switching function matrix at time k, design a switching control command based on a variable gain coefficient, and superimpose the switching control command with the reference sliding mode control command to calculate a robust sliding mode control command;

[0013] Perform Park inverse transformation on the robust sliding mode control command to obtain the αβ-axis robust sliding mode control command, and convert it into a pulse using the space vector pulse width modulation principle and apply it to the inverter switching tubes to achieve the robust sliding mode current control of the permanent magnet motor long-line drive system.

[0014] Furthermore, the permanent magnet motor long-line drive system includes a DC bus voltage V connected in sequence dc , a three-phase voltage source inverter, a three-phase LC filter, a long-distance cable, and a permanent magnet synchronous motor. The three-phase LC filter includes a filter inductor L f and a filter capacitor C f ; the system information includes collecting the filter inductor L at time k using voltage and current sensors fThe three-phase current i fa 、i fb and i fc , filter capacitor C f The three-phase voltage u sa 、u sb and u sc , the three-phase stator current i of the permanent magnet synchronous motor sa 、i sb 、i sc State variables, and the use of photoelectric encoders to collect the rotor electrical angle θ e The outer speed loop is regulated according to the traditional proportional integral, while the inner current loop adopts the robust sliding mode current control method.

[0015] Furthermore, the filter capacitor voltage dynamics model in the dq axis rotating coordinate system of the permanent magnet motor long-line drive system is as follows:

[0016] ;

[0017] In the formula, C f Represents the filter capacitor, u sd 、u sq Represents the dq axis filter capacitor voltage, and Indicates the rate of change of the dq-axis filter capacitor voltage, i fd 、i fq represents the dq axis filter inductor current, i sd 、i sq Represents the stator current of the dq-axis motor; ω e Represents the electrical angular velocity of the motor, which is determined by the rotor electrical angle θ e Taking the derivative with respect to time, we get;

[0018] Based on the property that the filter capacitor voltage has a zero rate of change when in steady state, that is: and Both are 0, and the filter inductor current reference is calculated through the filter capacitor voltage dynamics model:

[0019] ;

[0020] In the formula, and It is the reference of dq axis filter inductor current; and To realize the dq axis stator current reference of the permanent magnet synchronous motor vector control, Set to 0, is the output of the speed loop; k represents the k sampling time of the sensor.

[0021] Further, based on the principle that a high-pass filter only allows high-frequency signals to pass through, the resonant current component in the filter capacitor voltage is expressed as follows:

[0022] ;

[0023] In the formula, k and k - 1 represent the k sampling moment and the k - 1 sampling moment respectively, and are the dq-axis resonant current components, u sd , u sq are the dq-axis filter capacitor voltages, T s is the sampling period of each sensor, f c is the cut-off frequency of the high-pass filter;

[0024] Using the principle that a high-pass filter only allows high-frequency signals to pass through, the resonant current component in the filter capacitor voltage is extracted, and this resonant current component is subtracted from the filter inductor current reference to obtain a filter inductor current resonance suppression reference without the resonant current component:

[0025] ;

[0026] In the formula, and are the dq-axis filter inductor current resonance suppression references, is the damping coefficient used to adjust the resonance suppression intensity, taken as 0.707; and are the dq-axis resonant current components at the k sampling moment.

[0027] Further, the difference between the filter inductor current resonance suppression reference and the dq-axis filter inductor current at the k moment is calculated to obtain the discrete sliding mode switching function matrix at the k moment, and the expression is as follows:

[0028] ;

[0029] In the formula, is the discrete sliding mode switching function matrix at the k moment, and are the dq-axis components of the discrete sliding mode switching function matrix at the k moment; and are the dq-axis filter inductor current resonance suppression references, and are the filter inductor currents collected at the k moment;

[0030] The discrete sliding mode switching function matrix at the k + 1 moment is obtained by recursively advancing s(k) at the k moment by one step, and the expression is as follows:

[0031] ;

[0032] where, i fd (k + 1) and i fq (k + 1) are the dq-axis filter inductor currents at the (k + 1)-th moment discretized based on the second-order Taylor series expansion, and the specific expressions are as follows:

[0033] ;

[0034] In the formula, the coefficient matrices A, B, F, and G are respectively:

[0035] ; where, k and k + 1 respectively represent the k-th moment and the (k + 1)-th sampling moment, and are the filter inductor currents, and are the dq-axis inverter output voltages, u sd , u sq are the dq-axis filter capacitor voltages, i sd , i sq are the dq-axis motor stator currents, T s is the sampling period, L f represents the filter inductor, C f represents the filter capacitor, ω e represents the electrical angular velocity of the motor.

[0036] Furthermore, according to the principle that the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, that is: let the discrete sliding mode switching function matrix s(k) at the k-th moment be equal to the discrete sliding mode switching function matrix s(k + 1) at the (k + 1)-th moment, and the reference sliding mode control command is calculated as follows:

[0037] ;

[0038] In the formula, is the reference sliding mode control command at the k-th moment, I is the second-order identity matrix, A, B -1 , F, G are coefficient matrices.

[0039] Furthermore, a switching control command based on variable gain coefficients is designed based on the discrete sliding mode switching function matrix at the k-th moment, and the expression is as follows:

[0040] ;

[0041] In the formula, is the switching control command at the k-th moment; and are the dq-axis components of the discrete sliding mode switching function matrix at the k-th moment; and is a gain coefficient that adaptively decays and changes with the sliding mode switching function at time k. ε is greater than 0 and is set according to the upper bound when the maximum parameter mismatch perturbation occurs in the matrix coefficients in ; e is the base of the natural logarithm, represents the sign function;

[0042] By superimposing the switching control command with the reference sliding mode control command , the correct robust control command can be obtained. The robust sliding mode control command is as follows:

[0043] ;

[0044] In the formula, is the robust sliding mode control command at time k.

[0045] Furthermore, the robust sliding mode control command of the αβ axes is obtained according to the Park inverse transformation, and specifically as follows:

[0046] ;

[0047] In the formula, is the robust sliding mode control command of the αβ axes at time k, and are the α and β axis components of the robust sliding mode control command respectively, is the Park inverse transformation matrix, and θ e is the rotor electrical angle.

[0048] Furthermore, the robust sliding mode current control method of the permanent magnet motor long line drive system is stored in the memory of the computer device, and the computer device also includes a processor for executing the robust sliding mode current control method of the permanent magnet motor long line drive system.

[0049] A robust sliding mode current control system for a permanent magnet motor long line drive system includes a sensor detection unit, a Park transformation unit, and a robust sliding mode current control unit. The robust sliding mode current control unit includes a filter inductor current reference calculation unit, a filter inductor current resonance suppression reference unit, a discrete sliding mode switching function matrix, a robust sliding mode control command calculation unit, a Park inverse transformation unit, and a space vector modulation unit connected in sequence;

[0050] The sensor detection unit is used to obtain the three-phase currents of the filter inductor L f collected by the voltage and current sensors in the permanent magnet motor long line drive system, the three-phase voltages of the filter capacitor C f , the three-phase stator current state variables of the permanent magnet synchronous motor, and the rotor electrical angle θ e collected by the optical encoder;

[0051] The Park transformation unit is used to convert the data in the abc three-phase coordinate system into the dq-axis rotating coordinate system;

[0052] The filter inductor current reference calculation unit calculates the filter inductor current reference through the steady-state characteristics of the filter capacitor voltage dynamic model;

[0053] The filter inductor current resonance suppression reference unit extracts the resonance current component using a high-pass filter and calculates the filter inductor current resonance suppression reference;

[0054] The discrete sliding mode switching function matrix is used to design the discrete sliding mode switching function matrix based on the tracking error of the filter inductor current resonance suppression reference;

[0055] The robust sliding mode control command calculation unit calculates the robust sliding mode control command for controlling the permanent magnet motor long-line drive system using the discrete sliding mode switching function matrix;

[0056] The Park inverse transformation unit is used to transform the robust sliding mode control command to the αβ coordinate system through Park inverse transformation;

[0057] The space vector modulation unit is used to generate the pulse signal for controlling the inverter in the permanent magnet motor long-line drive system.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0059] The present invention obtains the reference sliding mode control command based on the discrete sliding mode switching function matrix for filtering current resonance suppression reference, which can effectively suppress the resonance in the permanent magnet motor long-line drive system; the method and system have simple steps and are convenient to use, and can quickly obtain the reference sliding mode control command of the control system and combine it with the switching control command with variable gain coefficient, ensuring the robustness and stability of the permanent magnet motor long-line drive system when the stator inductance parameter mismatch occurs. Description of the Drawings

[0060] Figure 1 It is a schematic block diagram of the robust sliding mode current control method for the permanent magnet motor long-line drive system of the present invention;

[0061] Figure 2 For the permanent magnet motor stator inductance parameter L in the traditional proportional-integral control method s When a 50% mismatch occurs, the dynamic and steady-state performance schematic diagrams of the motor speed, electromagnetic torque, d-axis stator current, q-axis stator current, and three-phase stator current;

[0062] Figure 3 For the permanent magnet motor stator inductance parameter L in the embodiment of the present invention sSchematic diagrams of the dynamic and steady-state performance of the motor speed, electromagnetic torque, d-axis stator current, q-axis stator current, and three-phase stator current at 50% mismatch. Detailed implementation manners

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0064] The robust sliding-mode current control method for the permanent magnet motor long-line drive system disclosed in the present invention uses the permanent magnet motor long-line drive system as Figure 1 shown, where the DC bus voltage V dc is converted into an AC voltage through a three-phase voltage source inverter, and then connected to the permanent magnet motor through a three-phase LC filter. Each phase filter inductor L f of the three-phase LC filter is connected in series with the output side of the inverter, and each phase filter capacitor C f has one end connected to the output side of the filter inductor L f , and the other ends are connected together to form a star connection. The three-phase filter inductor currents i fa , i fb , and i fc at the kth moment, the three-phase filter capacitor voltages u sa , u sb , and u sc , the three-phase stator currents i sa , i sb , i sc state variables and the rotor electrical angle θ e of the permanent magnet synchronous motor are collected in sequence. Among them, the rotor electrical angle θ e is used for Park transformation and Park inverse transformation. The speed loop still adopts the traditional proportional-integral method for regulation, and the current inner loop adopts the robust sliding-mode current control method provided by the present invention.

[0065] Figure 1 In dc , V f represents the DC bus voltage; L f represents the filter inductor, C e represents the filter capacitor, θ e is the electrical angle of the motor rotor; d / dt represents the derivative link, which is used to obtain the electrical angular velocity ω e * of the rotor; ω sd * , i sq * represent the dq-axis stator current references; u d (k) and u q (k), i fd(k) and i fq (k), u sd (k) and u sq (k), i sd (k) and i sq (k) respectively represents the dq-axis inverter output voltage, filter inductor current, filter capacitor voltage, and stator current obtained after Park transformation; i fd * 、i fq * represents the dq-axis filter inductor current reference; i fdh * 、i fqh * represents the dq-axis filter inductor current resonance suppression reference; s(k), s(k + 1) respectively represent the discrete sliding mode switching function matrices at times k and k + 1; u dq ref (k) represents the dq-axis robust sliding mode control command; u αβ ref (k) represents u dq ref (k) is the αβ-axis robust sliding mode control command obtained after Park inverse transformation.

[0066] The robust sliding mode current control method for a permanent magnet motor long line drive system includes the following steps:

[0067] S1. Use sensors to collect the system information of the permanent magnet motor long line drive system at time k; the system information includes collecting the three-phase currents i f of the filter inductor L fa 、i fb and i fc at time k by voltage and current sensors, the three-phase voltages u f of the filter capacitor C sa 、u sb and u sc 、the three-phase stator currents i sa 、i sb 、i sc state variables of the permanent magnet synchronous motor, and the rotor electrical angle θ e collected by an optical encoder; the speed outer loop is adjusted according to the traditional proportional integral, and the current inner loop adopts the said robust sliding mode current control method.

[0068] S2. Use the system information to establish the dynamic model of the filter capacitor voltage in the dq-axis rotating coordinate system of the permanent magnet motor long line drive system, and calculate the dq-axis filter inductor current reference using the dynamic model of the filter capacitor voltage; the dynamic model of the filter capacitor voltage in the dq-axis rotating coordinate system of the permanent magnet motor long line drive system is as follows:

[0069] ;

[0070] In the formula, C f represents the filter capacitor, and u sd , u sq represent the dq-axis filter capacitor voltages, and represent the rates of change of the dq-axis filter capacitor voltages, and i fd , i fq represent the dq-axis filter inductor currents, i sd , i sq represent the dq-axis motor stator currents; ω e represents the electrical angular velocity of the motor, which is obtained by differentiating the rotor electrical angle θ e with respect to time;

[0071] Based on the property that the rate of change of the filter capacitor voltage is zero at steady state, that is: let and both be 0, and calculate the reference of the filter inductor current through the dynamic model of the filter capacitor voltage:

[0072] ;

[0073] In the formula, and are the references of the dq-axis filter inductor currents; and are the references of the dq-axis stator currents for implementing the vector control of the permanent magnet synchronous motor, where is set to 0, is the output of the speed loop; k represents the k sampling moment of the sensor.

[0074] S3. Extract the resonant current component from the filter capacitor voltage, and subtract this resonant current component from the reference of the filter inductor current to obtain the resonant suppression reference of the filter inductor current without the resonant current component; According to the principle that the high-pass filter only allows high-frequency signals to pass, the resonant current component in the filter capacitor voltage is expressed as follows:

[0075] ;

[0076] In the formula, k and k - 1 represent the k moment and the k - 1 sampling moment respectively, and are the dq-axis resonant current components, u sd , u sq are the dq-axis filter capacitor voltages, T s is the sampling period of each sensor, and f c is the cut-off frequency of the high-pass filter;

[0077] Based on the principle that a high-pass filter only allows high-frequency signals to pass through, the resonant current component in the voltage of the filter capacitor is extracted, and this resonant current component is subtracted from the reference of the filter inductor current to obtain a reference for suppressing the resonant current of the filter inductor without the resonant current component:

[0078] ;

[0079] In the formula, and are the references for suppressing the resonant current of the dq-axis filter inductor, is the damping coefficient used to adjust the intensity of resonant suppression, taken as 0.707; and are the resonant current components of the dq-axis at the k sampling moment.

[0080] S4. Calculate the discrete sliding mode switching function matrix at the k moment and the k+1 moment;

[0081] Subtract the reference for suppressing the resonant current of the filter inductor from the dq-axis filter inductor current at the k moment to obtain the discrete sliding mode switching function matrix at the k moment, and the expression is as follows:

[0082] ;

[0083] In the formula, is the discrete sliding mode switching function matrix at the k moment, and are the dq-axis components of the discrete sliding mode switching function matrix at the k moment; and are the references for suppressing the resonant current of the dq-axis filter inductor, and are the filter inductor currents collected at the k moment;

[0084] Push the s(k) at the k moment one step forward to obtain the discrete sliding mode switching function matrix at the k+1 moment, and the expression is as follows:

[0085] ;

[0086] Among them, i fd (k + 1) and i fq (k + 1) are the dq-axis filter inductor currents at the k+1 moment obtained by discretization based on the second-order Taylor series expansion, and the specific expressions are as follows:

[0087] ;

[0088] In the formula, the coefficient matrices A, B, F, and G are respectively:

[0089] ; where, k and k + 1 represent the k-th moment and the (k + 1)-th sampling moment respectively, and is the filter inductor current, and are the dq-axis inverter output voltages, u sd 、u sq are the dq-axis filter capacitor voltages, i sd 、i sq are the dq-axis motor stator currents, T s is the sampling period, L f represents the filter inductor, C f represents the filter capacitor, ω e represents the electrical angular velocity of the motor.

[0090] S5. Since the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, the discrete sliding mode switching function matrices at the k-th moment and the (k + 1)-th moment are equal, and the reference sliding mode control command is calculated;

[0091] According to the principle that the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, that is: making the discrete sliding mode switching function matrix s(k) at the k-th moment equal to the discrete sliding mode switching function matrix s(k + 1) at the (k + 1)-th moment, the reference sliding mode control command is calculated as follows:

[0092] ;

[0093] In the formula, is the reference sliding mode control command at the k-th moment, I is the second-order identity matrix, A, B -1 , F, G are coefficient matrices.

[0094] S6. Based on the discrete sliding mode switching function matrix at the k-th moment, a switching control command based on a variable gain coefficient is designed, and the switching control command is superimposed with the reference sliding mode control command to calculate the robust sliding mode control command;

[0095] According to the principle that the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, the switching control command based on a variable gain coefficient designed based on the discrete sliding mode switching function matrix at the k-th moment is as follows:

[0096] ;

[0097] In the formula, is the switching control command at the k-th moment; and are the dq-axis components of the discrete sliding mode switching function matrix at the k-th moment; and is a gain coefficient that adaptively decays with the sliding mode switching function at time k. ε is greater than 0 and is set according to the upper bound when the maximum parametric mismatch perturbation occurs in the matrix coefficients in ; e is the base of the natural logarithm,

[0098] The switching control command is superimposed with the reference sliding mode control command to obtain the correct robust control command. The robust sliding mode control command is as follows:

[0099] ;

[0100] In the formula, is the robust sliding mode control command at time k.

[0101] S7. Perform the Park inverse transformation on the robust sliding mode control command to obtain the αβ-axis robust sliding mode control command, and convert it into pulses by using the space vector pulse width modulation principle and apply them to the inverter switching tubes to achieve the robust sliding mode current control of the permanent magnet motor long line drive system;

[0102] The αβ-axis robust sliding mode control command obtained by performing the Park inverse transformation on the robust sliding mode control command is specifically as follows:

[0103] ;

[0104] In the formula, is the αβ-axis robust sliding mode control command at time k, and are the α and β-axis components of the robust sliding mode control command respectively, is the Park inverse transformation matrix, and θ e is the rotor electrical angle.

[0105] A computer device includes a processor and a memory. The processor is electrically connected to the memory. The memory is used to store instructions and data, and the processor is used to execute the robust sliding mode current control method of the permanent magnet motor long line drive system.

[0106] A computer-readable storage medium, characterized in that a computer program is stored in the computer-readable storage medium, and the computer program is suitable for being loaded and executed by the processor to execute the robust sliding mode current control method of the permanent magnet motor long line drive system.

[0107] A robust sliding mode current control system for a permanent magnet motor long line drive system, including a sensor detection unit, a Park transformation unit, and a robust sliding mode current control unit. The robust sliding mode current control unit includes a filter inductor current reference calculation unit, a filter inductor current resonance suppression reference unit, a discrete sliding mode switching function matrix, a robust sliding mode control command calculation unit, a Park inverse transformation unit, and a space vector modulation unit in sequence;

[0108] The sensor detection unit is used to obtain the three-phase current of the filter inductor, the three-phase voltage of the filter capacitor, the three-phase stator current state variables of the permanent magnet synchronous motor, and the rotor electrical angle collected by the photoelectric encoder at the moment when the voltage and current sensors in the permanent magnet motor long line drive system collect; k the moment of the filter inductor L f the three-phase current of, the three-phase voltage of the filter capacitor C f and the three-phase stator current state variables of the permanent magnet synchronous motor, as well as the rotor electrical angle collected by the photoelectric encoder; θ e ;

[0109] The Park transformation unit is used to convert the data in the abc three-phase coordinate system to the dq-axis rotating coordinate system;

[0110] The filter inductor current reference calculation unit calculates the filter inductor current reference through the steady-state characteristics of the filter capacitor voltage dynamics model;

[0111] The filter inductor current resonance suppression reference unit extracts the resonance current component by using a high-pass filter and calculates the filter inductor current resonance suppression reference;

[0112] The discrete sliding mode switching function matrix is used to design the discrete sliding mode switching function matrix based on the filter inductor current resonance suppression reference tracking error;

[0113] The robust sliding mode control command calculation unit calculates the robust sliding mode control command for controlling the permanent magnet motor long line drive system by using the discrete sliding mode switching function matrix;

[0114] The Park inverse transformation unit is used to transform the robust sliding mode control command to the αβ coordinate system through Park inverse transformation;

[0115] The space vector modulation unit is used to generate the pulse signal for controlling the inverter in the permanent magnet motor long line drive system.

[0116] To verify the robust sliding mode current control method for the permanent magnet motor long line drive system provided by the present invention, this method is applied to the embodiment of the permanent magnet motor long line drive system. The parameters in the embodiment are shown in Table 1:

[0117] Table 1

[0118] ;

[0119] Figure 2 and Figure 3 are the reference speed of 1000 rpm, the load torque of 4.5 Nm, and the stator inductance L of the permanent magnet motor s Performance comparison waveforms from start-up to steady state of the traditional proportional-integral control and the method proposed in the present invention when 50% parameter mismatch occurs. From top to bottom are the motor speed, electromagnetic torque, d-axis stator current, q-axis stator current, and three-phase stator current respectively.

[0120] From Figure 2 and Figure 3 it can be seen that although the system speed can also reach 1000 rpm under traditional control, at this time, due to the L s parameter mismatch, obvious resonant oscillation phenomena occur, the dq-axis stator current ripple is very large, and it is no longer possible to accurately track its reference value, and the torque T e also shows large and severe resonant oscillations. In contrast, the control method of the present invention does not involve any stator inductance and there is a variable gain switching control term dedicated to resisting parameter mismatch. Therefore, it can always maintain excellent tracking performance of the dq-axis stator current when 50% parameter mismatch occurs in L s , shows strong robustness to L s parameter mismatch and does not show any resonant phenomena. It can be seen that this method can ensure the strong robustness and stability of the permanent magnet motor long-line drive system.

Claims

1. A robust sliding mode current control method for a permanent magnet motor long-line drive system, characterized in that, The steps are as follows: Collect the system information of the permanent magnet motor long-line drive system at time k using sensors. The permanent magnet motor long-line drive system includes a DC bus voltage V connected in sequence dc , a three-phase voltage source inverter, a three-phase LC filter, a long-distance cable, and a permanent magnet synchronous motor. The three-phase LC filter includes a filter inductor L f and a filter capacitor C f ; The system information includes the three-phase currents i f of the filter inductor L collected at time k using voltage and current sensors fa , i fb and i fc , the three-phase voltages u f of the filter capacitor C sa , u sb and u sc , the three-phase stator currents i sa , i sb , i sc state variables of the permanent magnet synchronous motor, and the rotor electrical angle θ collected using an optical encoder e ; The speed outer loop is adjusted according to the traditional proportional integral, and the current inner loop adopts the robust sliding mode current control method; Establish a dynamic model of the filter capacitor voltage in the dq-axis rotating coordinate system of the permanent magnet motor long-line drive system using system information, and calculate the reference of the filter inductor current based on the dynamic model of the filter capacitor voltage; Extract the resonant current component in the filter capacitor voltage, and subtract this resonant current component from the reference of the filter inductor current to obtain a reference for suppressing the resonant current of the filter inductor current without the resonant current component; Calculate the discrete sliding mode switching function matrices at time k and time k+1. Subtract the reference for suppressing the resonant current of the filter inductor current from the dq-axis filter inductor current at time k to obtain the discrete sliding mode switching function matrix at time k; recursively advance the s(k) at time k by one step to obtain the discrete sliding mode switching function matrix at time k+1; Since the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, the discrete sliding mode switching function matrices at time k and time k+1 are equal, and calculate the reference sliding mode control command; Based on the discrete sliding mode switching function matrix at time k, design a switching control command based on a variable gain coefficient, and superimpose the switching control command on the reference sliding mode control command to calculate a robust sliding mode control command; Perform an inverse Park transformation on the robust sliding mode control command to obtain the αβ-axis robust sliding mode control command, and convert it into pulses using the space vector pulse width modulation principle and apply them to the inverter switching tubes to achieve the robust sliding mode current control of the permanent magnet motor long-line drive system.

2. The robust sliding mode current control method for the permanent magnet motor long line drive system according to claim 1, wherein The dynamic model of the filter capacitor voltage in the dq-axis rotating coordinate system of the permanent magnet motor long-line drive system is as follows: ； where C f represents the filter capacitor, u sd , u sq represent the filter capacitor voltages on the dq axes, and represent the rates of change of the filter capacitor voltages on the dq axes, i fd , i fq represent the filter inductor currents on the dq axes, i sd , i sq represent the stator currents of the dq-axis motor; ω e represents the electrical angular velocity of the motor, which is obtained by differentiating the rotor electrical angle θ e with respect to time; Based on the property that the rate of change of the filter capacitor voltage is zero at steady state, i.e.: Let and both be 0, and calculate the reference of the filter inductor current through the dynamic model of the filter capacitor voltage: ； Wherein, and are the reference values of the dq-axis filter inductor currents; and are the reference values of the dq-axis stator currents for realizing the vector control of the permanent magnet synchronous motor, where is set to 0, is the output of the speed loop; k represents the k-th sampling moment of the sensor.

3. The robust sliding mode current control method for the permanent magnet motor long line drive system according to claim 2, wherein According to the principle that the high-pass filter only allows high-frequency signals to pass through, the resonant current component in the filter capacitor voltage is expressed as follows: ； where k and k-1 represent the k-th sampling moment and the (k-1)-th sampling moment respectively, and are the dq-axis resonant current components, u sd and u sq are the dq-axis filter capacitor voltages, T s is the sampling period of each sensor, f c is the cut-off frequency of the high-pass filter; Utilize the principle that the high-pass filter only allows high-frequency signals to pass through, extract the resonant current component in the filter capacitor voltage, and subtract this resonant current component from the reference of the filter inductor current to obtain a reference for suppressing the resonant current of the filter inductor current without the resonant current component: ； In the formula, and are the dq-axis filter inductor current resonance suppression references, is the damping coefficient used to adjust the resonance suppression intensity, and is taken as 0.707; and are the dq-axis resonant current components at the k sampling moment.

4. The robust sliding mode current control method for the permanent magnet motor long line drive system according to claim 3, characterized in that Subtract the reference for suppressing the resonant current of the filter inductor current from the dq-axis filter inductor current at time k to obtain the discrete sliding mode switching function matrix at time k, and the expression is as follows: ； Wherein, is the discrete sliding mode switching function matrix at time k, and are the dq-axis components of the discrete sliding mode switching function matrix at time k; and are the dq-axis filter inductor current resonance suppression references, and are the filter inductor currents collected at time k; Recursively advance the s(k) at time k by one step to obtain the discrete sliding mode switching function matrix at time k+1, and the expression is as follows: ； where, i fd (k + 1) and i fq (k + 1) are the dq-axis filter inductor currents at the (k + 1)-th moment obtained by discretization based on the second-order Taylor series expansion, and the specific expressions are as follows: ； In the formula, the coefficient matrices A, B, F, and G are respectively: ; where k and k + 1 represent the k-th moment and the (k + 1)-th sampling moment respectively, and is the filtered inductor current, and are the dq-axis inverter output voltages, u sd , u sq are the dq-axis filtered capacitor voltages, i sd , i sq are the dq-axis motor stator currents, T s is the sampling period, L f represents the filtered inductor, C f represents the filtered capacitor, ω e represents the electrical angular velocity of the motor.

5. The robust sliding mode current control method for the permanent magnet motor long line drive system according to claim 4, characterized in that According to the principle that the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, that is: make the discrete sliding mode switching function matrix s(k) at time k equal to the discrete sliding mode switching function matrix s(k+1) at time k+1, and calculate the reference sliding mode control command as follows: ； In the formula, is the reference sliding mode control command at time k, I is the second-order identity matrix, A, B -1 , F, and G are coefficient matrices.

6. The robust sliding mode current control method for the permanent magnet motor long line drive system according to claim 5, wherein Design a switching control command based on a variable gain coefficient based on the discrete sliding mode switching function matrix at time k, and the expression is as follows: ； wherein, is the switching control instruction at time k; and are the dq-axis components of the discrete sliding mode switching function matrix at time k; and are gain coefficients that adaptively decay and change with the sliding mode switching function at time k. ε is greater than 0 and is set according to the upper bound when the maximum parameter mismatch perturbation occurs in the matrix coefficients in; e is the base of the natural logarithm, represents the sign function; The switching control instruction is superimposed with the reference sliding mode control instruction to obtain the correct robust control instruction. The robust sliding mode control instruction is as follows: ； wherein, is the robust sliding mode control command at time k.

7. The robust sliding mode current control method for the long-line drive system of a permanent magnet motor according to claim 6, characterized in that, The robust sliding mode control command is obtained by performing an inverse Park transformation to obtain the αβ-axis robust sliding mode control command as follows: ； where is the αβ-axis robust sliding mode control command at time k, and are the α and β-axis components of the robust sliding mode control command respectively, is the Park inverse transformation matrix, and θ e is the rotor electrical angle.

8. The robust sliding mode current control method for the long-line drive system of a permanent magnet motor according to claim 7, characterized in that, The robust sliding mode current control method of the permanent magnet motor long-line drive system is stored in the memory of the computer device, and the computer device also includes a processor for executing the robust sliding mode current control method of the permanent magnet motor long-line drive system.

9. A robust sliding mode current control system for a long-line drive system of a permanent magnet motor, characterized in that: It includes a sensor detection unit, a Park transformation unit, and a robust sliding mode current control unit. The robust sliding mode current control unit includes a filter inductor current reference calculation unit, a filter inductor current resonance suppression reference unit, a discrete sliding mode switching function matrix, a robust sliding mode control command calculation unit, a Park inverse transformation unit, and a space vector modulation unit connected in sequence; A sensor detection unit for obtaining the filtered inductance at the moment when the voltage and current sensors in the long-line drive system of the permanent magnet motor collect k the three-phase current of the L f filter capacitor, the three-phase voltage of the C f filter capacitor, the state variables of the three-phase stator current of the permanent magnet synchronous motor, and the rotor electrical angle collected by using an optical encoder θ e ; The Park transformation unit is used to transform the data in the abc three-phase coordinate system into the dq-axis rotating coordinate system; The filter inductor current reference calculation unit calculates the filter inductor current reference based on the steady-state characteristics of the filter capacitor voltage dynamic model; The filter inductor current resonance suppression reference unit extracts the resonance current component in the filter capacitor voltage using the principle that a high-pass filter only allows high-frequency signals to pass through, and subtracts this resonance current component from the filter inductor current reference to obtain a filter inductor current resonance suppression reference without the resonance current component; The discrete sliding mode switching function matrix is used to design the discrete sliding mode switching function matrix based on the tracking error of the filter inductor current resonance suppression reference; The difference between the filter inductor current resonance suppression reference and the dq-axis filter inductor current at time k is taken to obtain the discrete sliding mode switching function matrix at time k; The robust sliding mode control command calculation unit recursively advances s(k) at time k by one step to obtain the discrete sliding mode switching function matrix at time k+1; calculates the robust sliding mode control command for controlling the permanent magnet motor long line drive system by using the discrete sliding mode switching function matrix; according to the principle that the discrete sliding mode switching function matrix remains unchanged in the neighborhood near the sliding mode surface, that is: making the discrete sliding mode switching function matrix s(k) at time k equal to the discrete sliding mode switching function matrix s(k+1) at time k+1, calculates the reference sliding mode control command; designs a switching control command based on variable gain coefficients based on the discrete sliding mode switching function matrix at time k, and superimposes the switching control command with the reference sliding mode control command to obtain the correct robust control command; The Park inverse transformation unit is used to transform the robust sliding mode control command to the αβ coordinate system through Park inverse transformation; The space vector modulation unit is used to generate pulse signals for controlling the inverter in the magneto long-line drive system.

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