Dq axis current loop decoupling method for permanent magnet synchronous motor in high speed operation

Abstract

The application discloses a dq-axis current loop decoupling method for a permanent magnet synchronous motor in high-speed operation, and belongs to the technical field of motor control. The dq-axis current loop decoupling method for the permanent magnet synchronous motor in high-speed operation comprises the following steps: a permanent magnet synchronous motor current loop model considering additional cross coupling and model parameter variation is established; a decoupling control method is designed by using the permanent magnet synchronous motor current loop model; and the influence caused by model parameter variation is compensated by using an interference observer. The method solves the problem that traditional current feedback decoupling is not completely decoupled at high speed, expands the application working condition of the motor decoupling method, improves the decoupling performance on the basis of the traditional decoupling method, simultaneously adds the interference observer, observes and compensates the uncertain quantity of system parameters, and improves the system robustness and current response capability.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a method for decoupling the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation. Background Technology

[0002] In recent years, permanent magnet synchronous motors have been widely used in various mechanical equipment due to their advantages such as simple structure, small size, high efficiency and low failure rate. With the continuous advancement of permanent magnet synchronous motor technology, the difficulty of operating and controlling high-speed permanent magnet synchronous motors is also increasing. The model parameters of permanent magnet synchronous motors will change when operating at high speed, which puts forward new requirements for the decoupling design of the dq axis of permanent magnet synchronous motors.

[0003] In the vector control system of a permanent magnet synchronous motor (PMSM), the inner current loop typically uses a PI (Proportional-Integral) regulator to control the dq-axis current, aiming to bring the steady-state current error close to zero by appropriately adjusting the parameters. However, the dq-axis systems are not independent but mutually influential. Transforming the coordinate system from a stationary to a rotating coordinate system generates speed-dependent coupling terms, severely impacting the performance of the PSM current controller. The current loop control performance, in turn, affects the performance of the entire closed-loop system. Although vector control can resolve static current decoupling, dynamic coupling terms still exist, especially as the speed increases. and The impact will become increasingly severe, and may even lead to current loop control instability. To address these issues, a new decoupling method for the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation is urgently needed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for decoupling the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for decoupling the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation includes the following steps: Establish a current loop model for a permanent magnet synchronous motor that considers additional cross-coupling and changes in model parameters; Using the current loop model of the permanent magnet synchronous motor, a decoupling control method is designed. The effects of model parameter changes are compensated by using a disturbance observer.

[0006] Furthermore, the current loop model expression for the permanent magnet synchronous motor is as follows: In the formula, and d_last - q_last represent the voltage projection components of the reference voltage vector on the calculation axes d_last and q_last, respectively; id, iq, Ld, and Lq represent the direct-axis and quadrature-axis currents and inductances, respectively; Rs is the stator winding resistance; ψf is the permanent magnet flux linkage; ωr is the rotor electric angular velocity; and Ts is the inverter sampling period.

[0007] Furthermore, the construction process of the permanent magnet synchronous motor current loop model includes: S11, in the synchronous rotating coordinate system, the quadrature and direct axis voltage equations of the PMSM in the time domain can be expressed as: Among them, u d u q These are the direct-axis and quadrature-axis voltages, respectively. S12, after comprehensively considering the cross-coupling modeling during high-speed motor operation, the relationship between the actual voltage and the calculated voltage is as follows: Among them, U d_real U q_real U d_last U d_last These are the voltage projection components of the reference voltage vector onto the actual rotor axis d_real - q_real and the voltage projection components of the reference voltage vector onto the calculation axis d_last - q_last, respectively. d_real and q_real represent the current dq-axis positions, while d_last and q_last represent the previous dq-axis positions. Within one sampling period T... s Inside, the angle difference ω between the two reference axes r T s ; S13, using U d_real U q_real Replace u d (t), u q (t), U d_last U q_last Recorded as and have to: Then organized into and The expression.

[0008] Furthermore, the process of designing a decoupling control method is as follows: Will and The expression is rewritten as: Where Rd_eq, Rq_eq, Ld_eq, Lq_eq, dd_eq, and dq_eq are equivalent formulas for the dq axis resistance parameters, inductance parameters, and coupling, respectively; and: The given voltage equation is: In the formula, GPI d (s), GPI q (s) are the transfer functions of the PI controllers for the d-axis and q-axis, respectively.

[0009] in: ; ; In the formula, k p_d k i_d These are the proportional and integral coefficients of the d-axis PI controller transfer function, respectively; k p_q k i_q These are the proportional and integral coefficients of the q-axis PI controller transfer function, respectively.

[0010] Furthermore, the specific process of interference observer compensation is as follows: S31, based on the given voltage equation, further considering the structure with parameter uncertainties, external disturbances, and unmodeled objects, the following is provided: In the formula, , , , , , These are the model quantities of the dq-axis resistance parameters, inductance parameters, and equivalent parameters of coupling, calculated from the system resistance and inductance models, respectively. , , , , , These represent the changes in the equivalent parameters of the dq-axis resistance, inductance, and coupling, calculated from the system resistance and inductance models, respectively; dd_out and dq_out represent the dq-axis coupling, taking into account external disturbances and unmodeled parts of the system, respectively.

[0011] S32, further rewriting the above equation, gives the existence of a controlled object consisting of the system's nominal model and the total disturbance, as follows: S33, further, the above equation can be expressed as follows: Considering the additional cross-coupling of current and parameter uncertainties during high-speed operation, the PMSM current loop is: In the formula, f d_eq For the lumped disturbance along the d-axis; f q_eq For concentrated perturbations along the q-axis.

[0012] Without considering noise signals, a basic interference observer can be designed based on the above formula: in, f d_eq_dob、 f q_eq_dob are the interference compensations for the dq axes, respectively; Gf=ωc_dob / (s+ωc_dob), which is taken as a first-order low-pass filter, and ωc_dob is the bandwidth parameter of the first-order low-pass filter; This is the model quantity for permanent magnet flux linkage.

[0013] S34, using the above equation, a compensation method based on an interference observer is constructed, and the voltage control equation is: In the formula, , , , These are the voltage and current given for the dq axes, respectively.

[0014] A decoupling system for the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation includes: Model building module: Establishes a current loop model of a permanent magnet synchronous motor that considers additional cross-coupling and changes in model parameters; Method design module: Using the permanent magnet synchronous motor current loop model, a decoupling control method is designed; And, the compensation module: uses the interference observer to compensate for the effects of changes in model parameters.

[0015] A decoupling device for the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation includes: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the above method.

[0016] A storage medium containing computer-executable instructions, wherein when the computer-executable instructions are executed by a processor, the processor performs the method described above.

[0017] The beneficial effects of this invention are: This invention proposes an improved decoupling method that considers the additional cross-coupling of current during high-speed operation of permanent magnet synchronous motors. By incorporating the additional cross-coupling of current into the current loop model, the calculation expression of the dq axis coupling of the system is changed, which solves the problem of incomplete decoupling under high speed in traditional current feedback decoupling. This expands the application conditions of motor decoupling methods and improves the decoupling performance of traditional decoupling methods.

[0018] The method proposed in this invention also adds an interference observer to observe and compensate for uncertainties in system parameters, thereby improving the system robustness and current response capability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the current feedback decoupling control structure designed based on additional cross-coupling modeling proposed in this invention; Figure 2 This is a schematic diagram of the compensation control structure based on the interference observer proposed in this invention; Figure 3 To ensure ideal inductor parameters, the impact of different current-added cross-coupling degrees on decoupling control is considered. Comparison diagram between current feedback decoupling and the method proposed in this invention; Figure 4 A comparison diagram of flow feedback decoupling and the method proposed in this invention under different inductor parameter variations with the same degree of cross-coupling applied to the same current; Figure 5 To further consider the loading experiment of the method proposed in this invention under parameter changes after adding current-added cross-coupling in the control loop, (a) is the dq-axis current when the inductance model quantity is equal to 0.7 times the true value, and (b) is the dq-axis current when the inductance model quantity is equal to 1.5 times the true value. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0022] like Figure 1 and Figure 2 As shown, a method for decoupling the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation includes the following steps: S1. Establish a current loop model for a permanent magnet synchronous motor that considers additional cross-coupling and changes in model parameters; The specific construction process is as follows: 1) In the synchronous rotating coordinate system, the quadrature and direct axis voltage equations of a permanent magnet synchronous motor (PMSM) in the time domain can be expressed as: Among them, u d u q i d i q L d L q These represent the direct-axis and quadrature-axis voltage, current, and inductance, respectively; Rs is the stator winding resistance; ψ f For permanent magnet flux linkage; ω r ω is the rotor's electric angular velocity.

[0023] 2) After comprehensively considering the cross-coupling modeling during high-speed motor operation, the relationship between the actual voltage and the calculated voltage is as follows: Among them, U d_real U q_real U d_last U d_last These are the voltage projection components of the reference voltage vector onto the actual rotor axis d_real - q_real and the voltage projection components of the reference voltage vector onto the calculation axis d_last - q_last, respectively. d_real and q_real represent the current dq-axis positions, while d_last and q_last represent the previous dq-axis positions. Within one sampling period T... s Inside, the angle difference ω between the two reference axes r T s .

[0024] 3) Use U d_real U q_real Replace u d (t), u q (t), and U d_last Uq_last Abbreviated as and get: Organized into and The expression is: In the formula, and d_last - q_last represent the voltage projection components of the reference voltage vector on the calculation axes d_last and q_last, respectively; id, iq, Ld, and Lq represent the direct-axis and quadrature-axis currents and inductances, respectively; Rs is the stator winding resistance; ψf is the permanent magnet flux linkage; ωr is the rotor electric angular velocity; and Ts is the inverter sampling period.

[0025] S2, using the permanent magnet synchronous motor current loop model established in S1 that considers additional cross-coupling and model parameter changes, designs a decoupling control method; The specific process includes: Will and The expression can be rewritten as follows: Where Rd_eq, Rq_eq, Ld_eq, Lq_eq, dd_eq, and dq_eq are equivalent formulas for the dq axis resistance parameters, inductance parameters, and coupling, respectively; and: When used and When describing a high-speed PMSM current loop system using expressions, a current-added cross-coupling model can be introduced to make the model description more accurate. The equivalent resistance and equivalent inductance parameters do not contain current or voltage information and can be considered as equivalent model parameters in current loop control. When system parameters are determined and the model is clearly defined, current feedback decoupling can achieve complete decoupling. Therefore, utilizing... and The model yields current feedback decoupling control based on current-added cross-coupling modeling, with the voltage setpoint equation as follows: In the formula, GPI d (s), GPI q (s) are the transfer functions of the PI controllers for the d-axis and q-axis, respectively.

[0026] in: ; ; In the formula, k p_d k i_d These are the proportional and integral coefficients of the d-axis PI controller transfer function, respectively; k p_q k i_q These are the proportional and integral coefficients of the q-axis PI controller transfer function, respectively.

[0027] S3 uses an interference observer to compensate for the effects of parameter changes in the model established in S1; The disturbance observer can aggregate the effects of system parameter uncertainties and external disturbances into a total disturbance and compensate for it; the specific process is as follows: 1) Based on the voltage given equation established in S2, further considering the structure with parameter uncertainties, external disturbances, and unmodeled objects, the following is proposed: in, , , , , , These are the model quantities of the dq-axis resistance parameters, inductance parameters, and equivalent parameters of coupling, calculated from the system resistance and inductance models, respectively. , , , , , These represent the changes in the equivalent parameters of the dq-axis resistance, inductance, and coupling, respectively, calculated from the system resistance and inductance models. d d_out、 d q_out represents the dq-axis coupling amount, taking into account external disturbances and unmodeled parts of the system, respectively; 2) Further rewriting the above equation, we have a controlled object consisting of the system's nominal model and the total disturbance, as follows: 3) Furthermore, the above equation can be expressed as follows: Considering the additional cross-coupling of current and parameter uncertainties during high-speed operation, the PMSM current loop is: In the formula, f d_eq For the lumped disturbance along the d-axis; f q_eq For concentrated perturbations along the q-axis.

[0028] in, Without considering noise signals, a basic interference observer can be designed based on the above formula: in, f d_eq_dob、 f q_eq_dob are the interference compensations for the dq axes, respectively; Gf=ωc_dob / (s+ωc_dob), which is taken as a first-order low-pass filter, and ωc_dob is the bandwidth parameter of the first-order low-pass filter; This is the model quantity for permanent magnet flux linkage.

[0029] 4) Using the above equation, a compensation method based on an interference observer is constructed, and the voltage control equation is: In the formula, , , , These are the voltage and current given for the dq axes, respectively.

[0030] The compensation control structure based on the disturbance observer constructed by S3, such as Figure 2 As shown.

[0031] Experimental comparison: To better illustrate the improvement in system parameter robustness brought about by the method proposed in this invention, a comparison is made between current feedback decoupling (CFD) and the method proposed in this invention: With ideal inductor parameters, simulation results considering the impact of different current-added cross-coupling degrees on control decoupling are as follows: Figure 3 As shown; the simulation gives the q-axis step response as follows: Figure 3 As shown in (a), the d-axis current fluctuation is as follows: Figure 3 As shown in (b) above. According to Figure 3 As the degree of cross-coupling of the current increases, there is a steady-state coupling current in the current feedback decoupling. However, the present invention can restore the steady state afterward without any coupling residue.

[0032] Simulation results for the same current with varying degrees of cross-coupling and different inductor parameters are as follows: Figure 4 As shown; the simulation gives the q-axis step response as follows: Figure 4 As shown in (a), the d-axis current fluctuation is as follows: Figure 4 As shown in (b) above. According to Figure 4 When the degree of current-added cross-coupling is small, both current feedback decoupling and this invention can still maintain steady-state decoupling effects. However, when the degree of current-added cross-coupling is large, current feedback decoupling introduces steady-state coupling current and cannot maintain system stability. In this case, this invention can still guarantee d-axis current convergence.

[0033] Figure 5 This shows the change in dq-axis current after a sudden load application, where... Figure 5 In the figure, (a) represents the dq-axis current when the inductance model value is equal to 0.7 times the actual value. Figure 5 In (b), the current along the dq axis is when the inductance model value is 1.5 times the actual value. From... Figure 5 As can be seen, regardless of whether the inductance parameter model value is greater or less than the actual value, the d-axis current fluctuation is very small. Figure 5 Experimental results show that the method proposed in this invention can achieve more complete decoupling.

[0034] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for decoupling the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation, characterized in that, Includes the following steps: Establish a current loop model for a permanent magnet synchronous motor that considers additional cross-coupling and changes in model parameters; Using the current loop model of the permanent magnet synchronous motor, a decoupling control method is designed. The effects of model parameter variations are compensated using a disturbance observer. The expression for the current loop model of the permanent magnet synchronous motor is: In the formula, and d_last - q_last represent the voltage projection components of the reference voltage vector on the calculation axes d_last - q_last; id, iq, Ld, and Lq represent the direct-axis and quadrature-axis currents and inductances, respectively; Rs is the stator winding resistance; ψf is the permanent magnet flux linkage; and ωr is the rotor electric angular velocity. Ts is the inverter sampling period; The construction process of the permanent magnet synchronous motor current loop model includes: S11, in the synchronous rotating coordinate system, the quadrature and direct axis voltage equations of the PMSM in the time domain can be expressed as: Among them, u d u q These are the direct-axis and quadrature-axis voltages, respectively. S12, after comprehensively considering the cross-coupling modeling during high-speed motor operation, the relationship between the actual voltage and the calculated voltage is as follows: Among them, U d_real U q_real U d_last U d_last These are the voltage projection components of the reference voltage vector onto the actual rotor axis d_real - q_real and the voltage projection components of the reference voltage vector onto the calculation axis d_last - q_last, respectively. d_real and q_real represent the current dq-axis positions, while d_last and q_last represent the previous dq-axis positions. Within one sampling period T... s Inside, the angle difference ω between the two reference axes r T s ; S13, using U d_real U q_real Replace u d (t), u q (t), U d_last U q_last Recorded as and ,have to: Then organized into and The expression; The process of designing a decoupling control method is as follows: Will and The expression is rewritten as: Where Rd_eq, Rq_eq, Ld_eq, Lq_eq, dd_eq, and dq_eq are equivalent formulas for the dq axis resistance parameters, inductance parameters, and coupling, respectively; and: The given voltage equation is: In the formula, GPI d (s), GPI q (s) are the transfer functions of the PI controller for the d-axis and q-axis, respectively; in: ； ； In the formula, kp_d and ki_d are the proportional coefficient and integral coefficient of the transfer function of the d-axis PI controller, respectively; kp_q and ki_q are the proportional coefficient and integral coefficient of the transfer function of the q-axis PI controller, respectively. The specific process of the disturbance observer compensation is as follows: S31, based on the given voltage equation, further considering the structure with parameter uncertainties, external disturbances, and unmodeled objects, the following is provided: In the formula, , , , , , These are the model quantities of the dq-axis resistance parameters, inductance parameters, and equivalent parameters of coupling, calculated from the system resistance and inductance models, respectively. , , , , , These represent the changes in the equivalent parameters of the dq-axis resistance, inductance, and coupling, calculated from the system resistance and inductance models, respectively; dd_out and dq_out represent the dq-axis coupling, taking into account external disturbances and unmodeled parts of the system, respectively. S32, further rewriting the above equation, gives the existence of a controlled object consisting of the system's nominal model and the total disturbance, as follows: S33, further, the above equation can be expressed as follows: Considering the additional cross-coupling of current and parameter uncertainties during high-speed operation, the PMSM current loop is: In the formula, f d_eq For the lumped disturbance along the d-axis; f q_eq For concentrated perturbations along the q-axis; Without considering noise signals, a basic interference observer can be designed based on the above formula: in, f d_eq_dob、 f q_eq_dob are the interference compensations for the dq axes, respectively; Gf=ωc_dob / (s+ωc_dob), which is taken as a first-order low-pass filter, and ωc_dob is the bandwidth parameter of the first-order low-pass filter; For the model quantity of permanent magnet flux linkage; S34, using the above equation, a compensation method based on an interference observer is constructed, and the voltage control equation is: In the formula, , , , These are the voltage and current given for the dq axes, respectively.

2. A dq-axis current loop decoupling system for a permanent magnet synchronous motor operating at high speed, comprising the method described in claim 1, characterized in that, include: Model building module: Establishes a current loop model of a permanent magnet synchronous motor that considers additional cross-coupling and changes in model parameters; Method design module: Using the permanent magnet synchronous motor current loop model, a decoupling control method is designed; And, the compensation module: uses the interference observer to compensate for the effects of changes in model parameters.

3. A decoupling device for the dq-axis current loop of a permanent magnet synchronous motor during high-speed operation, characterized in that, include: One or more processors; Memory, used to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method of claim 1.

4. A storage medium containing computer-executable instructions, characterized in that, When the computer-executable instructions are executed by a processor, the processor performs the method of claim 1.

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