A control method for low-efficiency feeding of a permanent magnet synchronous motor

Abstract

This invention provides a control method for low-efficiency power feeding of a permanent magnet synchronous motor (PMSM). The method employs a motor controller to control the low-efficiency power feeding of the PMSM in generator mode. In practical applications, some operating conditions do not require the PMSM to operate in the high-efficiency region in generator mode. The motor control is adjusted according to actual needs to achieve the desired generator current. This method improves the problem of uncontrollable generator current when the PMSM continuously operates in the high-efficiency region in generator mode. The use of a closed-loop regulation method based on the actual bus current effectively ensures the robustness and controllability of the system.

Description

Technical Field

[0001] This invention relates to a control method for low-efficiency power supply of a permanent magnet synchronous motor, which is applied in the field of automotive control technology. Background Technology

[0002] Currently, permanent magnet synchronous motor (PMSM) vector control systems can achieve high precision, high dynamic performance, and a wide range of speed regulation or positioning control, and have been widely used in industries, agriculture, new energy vehicles, and other fields. Traditional PMSM control algorithms focus on control performance and high efficiency, but cannot fully meet the actual application scenarios of PMSMs. In order to address the shortcomings of PMSMs in low-efficiency and unstable control in specific power generation modes, new research and implementation have been carried out on the control methods and principles of PMSMs.

[0003] Permanent magnet synchronous motors (PMSMs) have advantages such as simple structure, small size, light weight, low loss, and high efficiency, and can be applied in a variety of flexible scenarios. However, in order to ensure the efficiency of power generation in the power generation mode, traditional PMSM control algorithms ignore key factors such as bus current, which leads to the problem of uncontrollable bus current in actual working conditions. Furthermore, the traditional PMSM control method for calculating the DQ axis command current is not flexible enough, resulting in limitations in the calculation of the DQ axis command current during actual control.

[0004] Therefore, it is necessary to design a new control method for the inefficient power supply of permanent magnet synchronous motors to overcome the above problems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a control method for low-efficiency power supply of permanent magnet synchronous motors, which can meet the needs of different operating conditions and make up for the lack of a single calculation method for DQ axis command current. At the same time, the control method provided by this invention can solve the problem of continuous high-efficiency power generation of permanent magnet synchronous motors and uncontrollable bus. The method of closed-loop regulation of actual bus current effectively ensures the robustness and controllability of the system.

[0006] This invention is implemented as follows:

[0007] This invention provides a control method for low-efficiency power supply of a permanent magnet synchronous motor, comprising steps S1, S2, S3, S4, S5, and S6. Step S1 includes steps S10 and S11, step S2 includes steps S21 and S22, and step S3 includes steps S31, S32, S33, and S34. The steps are as follows:

[0008] Step S10: In the power generation condition, calculate the D-axis command current by looking up the table based on the torque MTPA of the torque command;

[0009] Step S11: If the current system voltage utilization rate is greater than the threshold, activate the field weakening enable module and proceed to step S21; if the current system voltage utilization rate is less than the threshold, do not activate the field weakening enable module, and enable the low-efficiency power supply function, proceed to step S31; if the current system voltage utilization rate is less than the threshold, disable the low-efficiency power supply function and proceed to step S4.

[0010] Step S21: Perform field weakening closed-loop control. Based on the difference between the current system voltage utilization rate and the calibrable target value, perform closed-loop PID regulation and calculate the field weakening D-axis current.

[0011] Step S22: Perform D-axis current synthesis by superimposing the D-axis command current obtained from the MTPA lookup table and the field-weakening D-axis current.

[0012] Step S31: Perform closed-loop operation of low-efficiency power supply function. Based on the difference between the current actual bus current and the calibrable target value, perform closed-loop PID regulation and calculate the D-axis compensation current.

[0013] Step S32: Limit the D-axis compensation current in step S31;

[0014] Step S33: Perform slope processing on the D-axis compensation current in step S32 to ensure the smoothness and continuity of the D-axis compensation current;

[0015] Step S34: Superimpose the D-axis command current, field weakening D-axis current, and D-axis compensation current obtained by looking up the table through MTPA;

[0016] Step S4: Limit the actual D-axis command current;

[0017] Step S5: Look up the Q-axis command current table based on the current torque command and D-axis command current;

[0018] Step S6: Perform FOC control on the motor.

[0019] Furthermore, in step S11, the activation conditions for the field weakening enable module are as follows:

[0020] Weak magnetic activation: Current system voltage utilization rate > calibrable target voltage utilization rate;

[0021] Low-efficiency power supply function activation: No fault, motor temperature < calibrable threshold, IGBT temperature < calibrable threshold, low-efficiency power supply function enable command.

[0022] Further, in step S21, based on the difference between the current system voltage utilization rate and the calibrable target value, closed-loop PID control is performed to calculate the field weakening D-axis current:

[0023] Us = √(Uα)2 +Uβ 2 > (Udc / (√3) × coefficient); the coefficient can be calibrated;

[0024] Δ = Us - (Udc / (√3) × coefficient)

[0025] Id = P × Δ + ∫Δ;

[0026] In the formula, Us is the voltage vector magnitude, Uα is the α-axis voltage, Uβ is the β-axis voltage, and Udc is the bus voltage; Δ is the deviation between the voltage vector magnitude and the available voltage magnitude; P is the proportional parameter, ∫ is the deviation integral; and Id is the D-axis current.

[0027] Furthermore, in step S31, based on the difference between the current actual bus current and the calibrable target value, closed-loop PID control is performed, and the method for calculating the D-axis compensation current is as follows:

[0028] The current actual bus current is filtered to ensure its accuracy and smoothness.

[0029] y (n+1)= y (n) ×a+x (n) ×(1-a)

[0030] Δ = Idc_back – Idc_ref;

[0031] Id = P × Δ + ∫Δ;

[0032] In the formula, y (n+1) This is the output result after filtering, y (n) The output result after the last filtering, x (n) The input data is denoted as 'a', where 'a' is the filter coefficient; 'Idc_back' is the actual bus current value, 'Idc_ref' is the target bus current value, 'Δ' is the deviation between the actual bus current value and the target bus current value; 'P' is the proportional parameter, '∫' is the deviation integral, and 'Id' is the D-axis current.

[0033] Furthermore, in step S4, the method for limiting the actual D-axis command current is as follows:

[0034] During motor calibration, the measured data of the motor are recorded, and the maximum D-axis current of the external characteristics across the entire speed range is calculated using an offline analysis method. This data is used to limit the D-axis command current.

[0035] Furthermore, in step S5, the method for looking up the Q-axis command current based on the current torque command and D-axis command current is as follows:

[0036] During motor calibration, the measured data of the motor are recorded. Through script processing, different combinations of Id and Iq commands across the entire torque range are calculated to ensure that the torque remains constant regardless of the combination. This data is used for the Q-axis command current lookup table in actual applications. By inputting the current torque command and D-axis command current, the Q-axis command current is obtained from the table.

[0037] The present invention has the following beneficial effects:

[0038] The control method for low-efficiency power supply of permanent magnet synchronous motor provided by this invention adopts a flexible and varied combination of DQ axis command current calculation methods, which can meet the needs of different operating conditions and make up for the shortcomings of the single DQ axis command current calculation method. Furthermore, it adopts an algorithm for low-efficiency power generation of permanent magnet synchronous motor under specific operating conditions with controllable actual bus current, which can solve the problem of continuous high-efficiency power generation of permanent magnet synchronous motor with uncontrollable bus. Attached Figure Description

[0039] 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, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 The control flowchart is provided in the embodiment of the present invention for the control method of low-efficiency power supply for permanent magnet synchronous motors.

[0041] Figure 2 A schematic diagram of the control algorithm for the control method of low-efficiency power supply for permanent magnet synchronous motors provided in an embodiment of the present invention;

[0042] Figure 3 A comparison chart of current commands;

[0043] Figure 4 A schematic diagram of the Q-axis command current for torque lookup table. Detailed Implementation

[0044] 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.

[0045] like Figure 1 and Figure 2As shown, the present invention provides a control method for low-efficiency power supply of a permanent magnet synchronous motor, including steps S1, S2, S3, S4, S5 and S6. Step S1 includes steps S10 and S11, step S2 includes steps S21 and S22, and step S3 includes steps S31, S32, S33 and S34. The above steps are as follows:

[0046] Step S10: In the power generation condition, calculate the D-axis command current by looking up the table based on the torque MTPA of the torque command;

[0047] Step S11: If the current system voltage utilization rate is greater than the threshold, activate the field weakening enable module and proceed to step S21; if the current system voltage utilization rate is less than the threshold, do not activate the field weakening enable module, and enable the low-efficiency power supply function, proceed to step S31; if the current system voltage utilization rate is less than the threshold, disable the low-efficiency power supply function and proceed to step S4.

[0048] In step S11, the activation conditions for the magnetic weakening enable module are as follows:

[0049] Weak magnetic activation: Current system voltage utilization rate > calibrable target voltage utilization rate;

[0050] Low-efficiency power supply function activation: No fault, motor temperature < calibrable threshold, IGBT temperature < calibrable threshold, low-efficiency power supply function enable command;

[0051] Weakening the field is disabled: No operation is performed, and the D-axis command current remains unchanged.

[0052] Step S21: Perform field weakening closed-loop control. Based on the difference between the current system voltage utilization rate and the calibrable target value, perform closed-loop PID adjustment to calculate the field weakening D-axis current. Specifically, the calculation method is as follows:

[0053] Us = √(Uα) 2 +Uβ 2 > (Udc / (√3) × coefficient); the coefficient can be calibrated;

[0054] Δ = Us - (Udc / (√3) × coefficient)

[0055] Id = P × Δ + ∫Δ;

[0056] In the formula, Us is the voltage vector magnitude, Uα is the α-axis voltage, Uβ is the β-axis voltage, and Udc is the bus voltage; Δ is the deviation between the voltage vector magnitude and the available voltage magnitude; P is the proportional parameter, ∫ is the deviation integral; and Id is the D-axis current.

[0057] Step S22: Perform D-axis current synthesis by superimposing the D-axis command current obtained by looking up the table through MTPA and the field weakening D-axis current.

[0058] Step S31: Perform closed-loop operation of the low-efficiency power supply function. Based on the difference between the current actual bus current and the calibrable target value, perform closed-loop PID control to calculate the D-axis compensation current. Specifically, the calculation method is as follows:

[0059] Filtering the actual bus current ensures its accuracy and smoothness.

[0060] y (n+1)= y (n) ×a+x (n) ×(1-a) ;

[0061] Δ = Idc_back – Idc_ref;

[0062] Id = P × Δ + ∫Δ;

[0063] In the formula, y (n+1) This is the output result after filtering, y (n) The output result after the last filtering, x (n) The input data is denoted as 'a', where 'a' is the filter coefficient; 'Idc_back' is the actual bus current value, 'Idc_ref' is the target bus current value, 'Δ' is the deviation between the actual bus current value and the target bus current value; 'P' is the proportional parameter, '∫' is the deviation integral, and 'Id' is the D-axis current.

[0064] Step S32: Limit the D-axis compensation current in step S31.

[0065] Step S33: The slope of the D-axis current in step S32 is processed to ensure the smoothness and continuity of the compensation current.

[0066] Step S34: The D-axis command current, the field weakening D-axis current, and the D-axis compensation current are superimposed by looking up the table through MTPA.

[0067] Step S4: Limit the actual D-axis command current; specifically, the method for limiting the actual D-axis command current is as follows: during the motor calibration process, record the actual measured data of the motor, and calculate the maximum Id current of the external characteristics across the entire speed range through offline analysis. This data is used to limit the D-axis command current.

[0068] Step S5: Based on the current torque command and D-axis command current, perform a table lookup for the Q-axis command current. (See [reference]) Figure 4 The specific method is as follows: During the motor calibration process, the actual measured data of the motor is recorded. Through script processing, different combinations of Id and Iq commands across the entire torque range are calculated to ensure that the torque remains constant regardless of the combination. This data is used for the Q-axis command current lookup table in actual applications. The current torque command and D-axis current command are input, and the Q-axis command current is obtained by looking up the table.

[0069] like Figure 3 As shown in step S5, the effect diagram of the D and Q axis command currents is shown. Curve b is the command current curve for disabling the low-efficiency power generation control of the permanent magnet synchronous motor, and curve a is the command current curve for enabling the low-efficiency power generation control of the permanent magnet synchronous motor.

[0070] Step S6: Perform FOC control on the motor to control the low-efficiency power supply of the permanent magnet synchronous motor.

[0071] The control method for low-efficiency power supply of permanent magnet synchronous motors provided in this invention addresses the problem of the permanent magnet synchronous motor continuously operating in the high-efficiency region during power generation by modifying the DQ axis current command through a control algorithm based on bus current. This allows the bus current to be controllable even when the permanent magnet synchronous motor operates in the low-efficiency region. Furthermore, by using torque command and D-axis current lookup table to derive the Q-axis current command, the method solves the problem of flexible combination of DQ commands while keeping the torque command constant. The method employs a closed-loop adjustment of the actual bus current, effectively ensuring system robustness and controllability. This approach also broadens the application scenarios for permanent magnet synchronous motors.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for low-efficiency power supply of a permanent magnet synchronous motor, characterized in that, The process includes steps S1, S2, S3, S4, S5, and S6. Step S1 includes steps S10 and S11, step S2 includes steps S21 and S22, and step S3 includes steps S31, S32, S33, and S34. The steps are as follows: Step S10: In the power generation condition, calculate the D-axis command current by looking up the table based on the torque MTPA of the torque command; Step S11: If the current system voltage utilization rate is greater than the threshold, activate the field weakening enable module and proceed to step S21; if the current system voltage utilization rate is less than the threshold, do not activate the field weakening enable module, and enable the low-efficiency power supply function, proceed to step S31; if the current system voltage utilization rate is less than the threshold, disable the low-efficiency power supply function and proceed to step S4. Step S21: Perform field weakening closed-loop control. Based on the difference between the current system voltage utilization rate and the calibrable target value, perform closed-loop PID regulation and calculate the field weakening D-axis current. Step S22: Perform D-axis current synthesis by superimposing the D-axis command current obtained from the MTPA lookup table and the field-weakening D-axis current. Step S31: Perform closed-loop operation of low-efficiency power supply function. Based on the difference between the current actual bus current and the calibrable target value, perform closed-loop PID regulation and calculate the D-axis compensation current. Step S32: Limit the D-axis compensation current in step S31; Step S33: Perform slope processing on the D-axis compensation current in step S32 to ensure the smoothness and continuity of the D-axis compensation current; Step S34: Superimpose the D-axis command current, field weakening D-axis current, and D-axis compensation current obtained by looking up the table through MTPA; Step S4: Limit the actual D-axis command current; Step S5: Look up the Q-axis command current table based on the current torque command and D-axis command current; Step S6: Perform FOC control on the motor.

2. The control method for low-efficiency power supply of a permanent magnet synchronous motor as described in claim 1, characterized in that: In step S11, the activation conditions for the field weakening enable module are as follows: Weak magnetic activation: Current system voltage utilization rate > calibrable target voltage utilization rate; Low-efficiency power supply function activation: No fault, motor temperature < calibrable threshold, IGBT temperature < calibrable threshold, low-efficiency power supply function enable command.

3. The control method for low-efficiency power supply of a permanent magnet synchronous motor as described in claim 1, characterized in that: In step S21, based on the difference between the current system voltage utilization rate and the calibrable target value, closed-loop PID control is performed to calculate the field weakening D-axis current: Us = √(Uα) 2 +Uβ 2 > (Udc / (√3) × coefficient); the coefficient can be calibrated; Δ = Us - (Udc / (√3) × coefficient) Id = P × Δ + ∫Δ; In the formula, Us is the voltage vector magnitude, Uα is the α-axis voltage, Uβ is the β-axis voltage, and Udc is the bus voltage; Δ is the deviation between the voltage vector magnitude and the available voltage magnitude; P is the proportional parameter, ∫ is the deviation integral; and Id is the D-axis current.

4. The control method for low-efficiency power supply of a permanent magnet synchronous motor as described in claim 1, characterized in that: In step S31, based on the difference between the current actual bus current and the calibrable target value, closed-loop PID control is performed, and the method for calculating the D-axis compensation current is as follows: The current actual bus current is filtered to ensure its accuracy and smoothness. and (n+1)= and (n) ×a+x (n) ×(1-a); Δ = Idc_back – Idc_ref; Id = P × Δ + ∫Δ; In the formula, y (n+1) This is the output result after filtering, y (n) The output result after the last filtering, x (n) The input data is denoted as 'a', where 'a' is the filter coefficient; 'Idc_back' is the actual bus current value, 'Idc_ref' is the target bus current value, 'Δ' is the deviation between the actual bus current value and the target bus current value; 'P' is the proportional parameter, '∫' is the deviation integral, and 'Id' is the D-axis current.

5. The control method for low-efficiency power supply of a permanent magnet synchronous motor as described in claim 1, characterized in that: In step S4, the method for limiting the actual D-axis command current is as follows: During motor calibration, the measured data of the motor are recorded, and the maximum D-axis current of the external characteristics across the entire speed range is calculated using an offline analysis method. This data is used to limit the D-axis command current.

6. The control method for low-efficiency power supply of a permanent magnet synchronous motor as described in claim 1, characterized in that: In step S5, the method for looking up the Q-axis command current based on the current torque command and D-axis command current is as follows: During motor calibration, the measured data of the motor are recorded. Through script processing, different combinations of Id and Iq commands across the entire torque range are calculated to ensure that the torque remains constant regardless of the combination. This data is used for the Q-axis command current lookup table in actual applications. By inputting the current torque command and D-axis command current, the Q-axis command current is obtained from the table.

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