Permanent magnet synchronous motor sampling current bias error compensation method and application

Abstract

The invention discloses a sampling current bias error compensation method for a permanent magnet synchronous motor. The sampling current bias error compensation method comprises the following steps: step 1, acquiring the shortest duration required by sampling current bias; 2, the permanent magnet synchronous motor is controlled in a vector mode; 3, the zero-voltage vector holding time is obtained, a sampling current compensation mode is selected according to the zero-voltage vector holding time and the shortest time needed by sampling current bias, and the compensation mode comprises the steps that when the zero-voltage vector holding time is larger than or equal to the shortest time needed by sampling current bias, a direct compensation mode is carried out; when the zero voltage vector holding duration is smaller than the shortest duration required by sampling current bias, terminal voltage integration is carried out to judge a compensation mode; and 4, performing vector control on the permanent magnet synchronous motor through the compensated sampling current, and performing closed-loop control. According to the invention, the operation precision of the permanent magnet synchronous motor can be improved, and the motor operation system can adapt to the dynamic change of the offset error.

Description

Technical Field

[0001] The design of the present invention relates to the technical field of permanent magnet synchronous motor control, and particularly to a method and application for compensating the sampling current bias error of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors have the advantages of high efficiency, fast response, low noise, etc. Therefore, permanent magnet synchronous motors have been widely used in more and more industries. Compensating the sampling current measurement bias error of permanent magnet synchronous motors, that is, compensating the current bias error measured under the influence of sensor drift, thermal drift and nonlinearity of related circuits, has wide applications in fields such as high-precision motor control, low-speed startup, torque control, and enhanced robustness to electromagnetic interference and temperature changes.

[0003] The traditional sampling current measurement bias error compensation scheme for permanent magnet synchronous motors is calibrated at startup or when the motor is stationary without load. In the traditional error compensation scheme, the steps are generally to keep the motor stationary in a no-load or non-powered state to ensure that no current flows through; read the current sampling values of each phase and record them as bias values; in subsequent sampling, subtract this bias value from the current sampling value to eliminate the bias error. However, this scheme requires the motor to be in a no-load or non-powered state during calibration, and it cannot effectively calibrate the zero drift caused by temperature drift or sensor aging, and is not suitable for real-time compensation. Therefore, in order to cope with more complex working conditions, other methods need to be combined to perform sampling current measurement bias compensation. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method and application for compensating the sampling current bias error of a permanent magnet synchronous motor to solve the technical problems in the prior art that the zero drift caused by temperature drift or sensor aging cannot be effectively calibrated and real-time compensation cannot be performed.

[0005] The present invention provides a method for compensating the sampling current bias error of a permanent magnet synchronous motor, and the steps are as follows:

[0006] Step 1: Obtain the shortest duration required for sampling current bias.

[0007] Step 2: Control the permanent magnet synchronous motor to be controlled in a vector mode.

[0008] Step 3: Obtain the duration of maintaining the zero voltage vector, and select the sampling current compensation method according to the duration of maintaining the zero voltage vector and the shortest duration required for sampling current bias. The compensation methods include:

[0009] When the duration of maintaining the zero voltage vector is greater than or equal to the shortest duration required for sampling current bias, perform the direct compensation method;

[0010] When the holding time of the zero voltage vector is less than the shortest time required for sampling current bias, the terminal voltage integration judgment compensation method is performed;

[0011] Step 4: Perform vector control on the permanent magnet synchronous motor through the compensated sampling current and conduct closed-loop control.

[0012] Further, in the said Step 1, the specific formula for obtaining the shortest time required for sampling current bias is:

[0013] T s_min = T on + T off + T DEAD + T ADC + T DELAY

[0014] In the formula, T on , T off are respectively the conduction time and the turn-off time of the power device in the permanent magnet synchronous motor driver; T DEAD is the dead time; T ADC is the ADC conversion time; T DELAY is the sampling delay.

[0015] Further, in the said Step 3, the holding time of the zero voltage vector is the duration when the three lower bridge arms in the permanent magnet synchronous motor driver conduct simultaneously.

[0016] Further, in the said Step 3, the direct compensation method is specifically:

[0017] Take a sample at the T0 moment in a PWM cycle to obtain the latest bias value, and compensate the sampling current according to the latest bias value.

[0018] Among them, the formula for obtaining the T0 moment is:

[0019] T0 = (1 - D max )T PWM - T on - T DEAD - T ADC - T DELAY

[0020] In the formula, D max is the maximum duty cycle in the three phases of the permanent magnet synchronous motor; T PWM is the duration of a PWM cycle; T DEAD is the dead time; T ADC is the ADC conversion time; T DELAY is the sampling delay.

[0021] Further, the specific method for compensating the sampling current according to the latest bias value is:

[0022] When the latest bias value is greater than the original bias value, the original bias value is incremented by one to obtain the compensated sampling current bias.

[0023] When the latest bias value is less than the original bias value, the original bias value is decremented by one to obtain the compensated sampling current bias.

[0024] Compensate the sampling current with the compensated sampling current bias.

[0025] Further, in step 3, the specific method for compensating the end voltage integral judgment is as follows:

[0026] Obtain the voltage integral values of the upper and lower half cycles of the end voltage respectively. When the voltage integral value of the upper half cycle is greater than that of the lower half cycle, there is a positive error in the current bias; when the voltage integral value of the upper half cycle is less than that of the lower half cycle, there is a negative error in the current bias. Compensate the sampling current according to the positive and negative error states of the current bias.

[0027] Further, the specific method for compensating the sampling current according to the positive and negative error states of the current bias is as follows:

[0028] When there is a positive error in the current bias, the original bias value is decremented by one to obtain the compensated sampling current bias.

[0029] When there is a negative error in the current bias, the original bias value is incremented by one to obtain the compensated sampling current bias.

[0030] Compensate the sampling current with the compensated sampling current bias.

[0031] The present invention also provides an application of a method for compensating the sampling current bias error of a permanent magnet synchronous motor, which is applied to the control of permanent magnet synchronous motors with single-resistance, double-resistance, and triple-resistance sampling.

[0032] Advantages of the present invention:

[0033] By detecting and calibrating the bias error of the sampling current in real time during the zero voltage vector period, the present invention ensures effective calibration of the current bias compensation during the dynamic operation of the system, which is beneficial to improving the operation accuracy of the permanent magnet synchronous motor and realizes the adaptation of the motor operation system to the dynamic change of the bias error.

[0034] The method for updating the bias value of the present invention has strong adaptability and can be applied to the drive systems of permanent magnet synchronous motors with single-resistance, double-resistance, and triple-resistance sampling; fully considering factors such as the conduction time, turn-off time, dead time, ADC conversion time, and sampling delay of power devices in the permanent magnet synchronous motor driver in different systems, it has high engineering practice value.

[0035] The present invention determines whether there is a current bias error by checking whether the integral values of the upper and lower half cycles within one electrical cycle of the sampled terminal voltage are equal. Utilizing the voltage-current relationship of a permanent magnet synchronous motor and adopting the method of voltage sampling, there are no sampling biases and errors, and it can effectively and accurately determine whether there is an error in the current bias. Description of the Drawings

[0036] The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings. The drawings are schematic and should not be construed as imposing any limitation on the present invention. In the drawings:

[0037] Figure 1 is a schematic flowchart of a specific embodiment of the present invention. Detailed Embodiments

[0038] 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. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0039] The present invention will be further illustrated below with specific embodiments. Those skilled in the art should understand that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. Modifications of various equivalent forms of the present invention all fall within the scope defined by the appended claims of this application.

[0040] As Figure 1 shown, the present invention provides a method for compensating the sampling current bias error of a permanent magnet synchronous motor. Taking a permanent magnet synchronous motor system with double-resistance sampling as an example, where the sampling resistors are at the low ends of phases A and B, and the current of phase C is reconstructed from phases A and B, the method includes the following steps:

[0041] Step 1: Obtain the shortest duration required for sampling the current bias. The specific formula is:

[0042] T s_min = T on + T off + T DEAD + T ADC + T DELAY

[0043] In the formula, T on , T off are respectively the conduction time and the turn-off time of the power devices in the permanent magnet synchronous motor driver; T DEAD is the dead time; T ADC is the ADC conversion time; T DELAYis the sampling delay;

[0044] For example, T on = 1.2 μs, T off = 0.8 μs, T DEAD = 0.8 μs, T ADC = 0.1 μs, T DELAY = 0.2 μs, then T s_min = 3.1 μs;

[0045] Step 2: Control the permanent magnet synchronous motor in a vector control mode: There are 7 vector combinations (000), (001), (010), (011), (100), (101), (110), (111). Among them, (000) is the zero vector, that is, the power devices of the three lower bridge arms in the permanent magnet synchronous motor driver are turned on simultaneously, and the power devices of the upper bridge arms are all turned off;

[0046] Step 3: Take the duration when the three lower bridge arms in the permanent magnet synchronous motor driver are turned on simultaneously as the zero voltage vector holding duration, and select the sampling current compensation method according to the zero voltage vector holding duration and the shortest duration required for sampling current offset. The compensation methods include:

[0047] When the zero voltage vector holding duration is greater than or equal to the shortest duration required for sampling current offset, perform the direct compensation method. The specific method is:

[0048] Take a sample at the T0 moment in a PWM cycle to obtain the latest offset value. Among them, the formula for obtaining the T0 moment is:

[0049] T0 = (1 - D max )T PWM - T on - T DEAD - T ADC - T DELAY

[0050] In the formula, D max is the maximum duty cycle in the three phases of the permanent magnet synchronous motor; T PWM is the duration of a PWM cycle; T DEAD is the dead time; T ADC is the ADC conversion time; T DELAY is the sampling delay;

[0051] For example, if the PWM cycle is 50 μs and the maximum duty cycle is 70%, the zero voltage holding time can be calculated as (1 - D max )T PWM = 0.3 × 50 = 15 μs, T s_min = 3.1 μs, and the T0 moment is calculated as:

[0052] T0 = (1 - D max )T PWM -T on -T DEAD -T ADC -T DELAY

[0053] = 15 - 1.2 - 0.8 - 0.1 - 0.2

[0054] = 12.7 μs

[0055] For the dual - resistance sampling permanent - magnet synchronous motor system, for phases A and B, sampling can be triggered simultaneously at time T0;

[0056] When the latest bias value is greater than the original bias value, the original bias value is incremented by one to be the compensated sampling current bias;

[0057] When the latest bias value is less than the original bias value, the original bias value is decremented by one to be the compensated sampling current bias;

[0058] For example, when the latest bias value is 1500 and the original bias value is 1490, the compensated sampling current bias is 1490 + 1 = 1491;

[0059] Compensate the sampling current with the compensated sampling current bias;

[0060] When the holding duration of the zero - voltage vector is less than the shortest duration required for the sampling current bias, perform terminal - voltage integration to determine the compensation method. The specific method is as follows:

[0061] Obtain the voltage integration values of the upper and lower half - cycles of the terminal voltage respectively. When the voltage integration value of the upper half - cycle is greater than that of the lower half - cycle, there is a positive error in the current bias; when the voltage integration value of the upper half - cycle is less than that of the lower half - cycle, there is a negative error in the current bias. Compensate the sampling current according to the positive and negative error states of the current bias;

[0062] When there is a positive error in the current bias, the original bias value is decremented by one to be the compensated sampling current bias;

[0063] When there is a negative error in the current bias, the original bias value is incremented by one to be the compensated sampling current bias;

[0064] Compensate the sampling current with the compensated sampling current bias.

[0065] For example, in a permanent magnet synchronous motor drive system with single-resistor sampling, calculate the upper and lower half-cycle voltage integral values of any phase terminal voltage within one electrical cycle; when the upper half-cycle voltage integral value Ui1 and the lower half-cycle voltage integral value Ui2 satisfy |Ui1| > |Ui2|, there is a positive error in the current bias; when the upper half-cycle voltage integral value Ui1 and the lower half-cycle voltage integral value Ui2 satisfy |Ui1| < |Ui2|, there is a positive error in the current bias;

[0066] For another example, in a permanent magnet synchronous motor drive system with double- or triple-resistor sampling, calculate the upper and lower half-cycle voltage integral values of the terminal voltages corresponding to the double or triple resistors within one electrical cycle; when the upper half-cycle voltage integral value Ui1 and the lower half-cycle voltage integral value Ui2 satisfy |Ui1| > |Ui2|, there is a positive error in the current bias of the corresponding phase; if the upper half-cycle voltage integral value Ui1 and the lower half-cycle voltage integral value Ui2 satisfy |Ui1| < |Ui2|, there is a negative error in the current bias of the corresponding phase;

[0067] The principle is as follows: According to the voltage equation of the permanent magnet synchronous motor as follows:

[0068]

[0069] Under ideal conditions, i Aerr = 0, then the absolute values of the upper and lower half-cycle integral values of U A are equal. In the case of positive deviation, that is, i Aerr > 0, which results in the absolute value of the upper half-cycle integral value of U A being greater than the absolute value of the lower half-cycle integral value. In the case of negative deviation, that is, i Aerr < 0, which results in the absolute value of the upper half-cycle integral value of U A being less than the absolute value of the lower half-cycle integral value.

[0070] Step 4: Perform vector control on the permanent magnet synchronous motor with the compensated sampled current and conduct closed-loop control.

[0071] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for compensating a sampling current bias error of a permanent magnet synchronous motor, characterized in that: The steps include: Step 1: Obtain the shortest time required for sampling current bias; Step 2: Control the permanent magnet synchronous motor in a vector manner; Step 3: Obtain the zero voltage vector holding time, and select the sampling current compensation method according to the zero voltage vector holding time and the shortest time required for the sampling current bias. The compensation methods include: When the zero voltage vector is maintained for a time greater than or equal to the shortest time required for the sampling current bias, direct compensation is performed; When the zero voltage vector is maintained for a time shorter than the shortest time required for sampling current bias, the terminal voltage is integrated to determine the compensation method; Step 4: Perform vector control on the permanent magnet synchronous motor through the compensated sampling current to perform closed-loop control.

2. The method for compensating the sampling current bias error of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 1, the specific formula for obtaining the shortest time required for sampling current bias is: T s_min =T on +T off +T DEAD +T ADC +T DELAY Where, T on , T off are the on-time and off-time of the power devices in the permanent magnet synchronous motor driver; T DEAD is the dead time; T ADC is the ADC conversion time; T DELAY is the sampling delay.

3. The method for compensating the sampling current bias error of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 3, the zero voltage vector is maintained for a period of time during which the three lower bridge arms in the permanent magnet synchronous motor driver are simultaneously turned on.

4. The method for compensating the sampling current bias error of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 3, the direct compensation method is specifically: A sample is taken at the T0 time in a PWM cycle to obtain the latest offset value, and the sampled current is compensated according to the latest offset value. Among them, the formula for obtaining the time T0 is: T0=(1-D max )T PWM -T on -T DEAD -T ADC -T DELAY Where D max is the maximum duty cycle of the three-phase permanent magnet synchronous motor; T PWM is the duration of a PWM cycle; T DEAD is the dead time; T ADC is the ADC conversion time; T DELAY is the sampling delay.

5. The method for compensating the sampling current bias error of a permanent magnet synchronous motor according to claim 4, characterized in that: The specific method for compensating the sampling current according to the latest offset value is: When the latest offset value is greater than the original offset value, the original offset value is increased by one to serve as the compensated sampling current offset; When the latest offset value is less than the original offset value, the original offset value is reduced by one to serve as the compensated sampling current offset; The sampled current is offset compensated with the compensated sampled current.

6. The method for compensating the sampling current bias error of a permanent magnet synchronous motor according to claim 1, characterized in that: In step 3, the terminal voltage integral judgment compensation method is specifically: The voltage integral values ​​of the upper and lower half cycles of the terminal voltage are obtained respectively. When the voltage integral value of the upper half cycle is greater than that of the lower half cycle, there is a positive error in the current bias; when the voltage integral value of the upper half cycle is less than that of the lower half cycle, there is a negative error in the current bias. The sampling current is compensated according to the positive and negative error states of the current bias.

7. The method for compensating the sampling current bias error of a permanent magnet synchronous motor according to claim 6, characterized in that: The specific method for compensating the sampling current according to the positive and negative error states of the current bias is: When there is a positive error in the current bias, the original bias value is reduced by one to serve as the compensated sampling current bias; When there is a negative error in the current offset, the original offset value is increased by one to serve as the compensated sampling current offset; The sampled current is offset compensated with the compensated sampled current.

8. An application of a method for compensating a sampling current bias error of a permanent magnet synchronous motor, characterized in that: The method is applied to the control of permanent magnet synchronous motors with single-resistance, double-resistance and triple-resistance sampling.

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