A high-precision dead zone compensation method based on duty cycle calibration

Abstract

The invention discloses a high-precision dead zone compensation method based on duty cycle calibration, and relates to the field of power electronics technology. The high-precision dead zone compensation method based on duty cycle calibration is characterized in that: the specific operations are as follows: S1, building an offline calibration system, the specific operations are as follows: S11, connecting the motor controller to the motor; S12, connecting the motor controller to the bus power supply, and the oscilloscope measures the VDS voltage of the lower bridge arm of the U-phase motor controller, wherein VDS is the voltage between the motor U and the negative power supply. The high-precision dead zone compensation method based on duty cycle calibration obtains the duty cycle data required for the actual output voltage under different phase current conditions during the calibration process. The data takes into account all factors affecting the compensation voltage, such as phase current amplitude, power tube nonlinearity, dead time, etc. The actual output voltage obtained is the actual measured voltage. The duty cycle under the current voltage instruction is obtained by looking up the table to achieve precise voltage compensation.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a high-precision dead zone compensation method based on duty cycle calibration. Background Art

[0002] In the field of power electronics, in order to prevent the upper and lower bridges of the inverter from being directly connected, a dead zone needs to be added to the drive signal. Although the existence of the dead zone prevents the upper and lower bridges from being directly connected, it will cause voltage distortion, which in turn causes current distortion, and will increase torque fluctuations and noise; in the field of speed sensorless, the existence of the dead zone will cause a deviation between the actual output voltage and the command voltage, which seriously affects the observer performance at low speeds of the motor. In order to improve the motor control performance, dead zone compensation must be performed.

[0003] Patent: CN115483858A, discloses a dead zone compensation method and system based on PI control in the current zero-crossing region, belonging to the field of permanent magnet synchronous motor control. The dead zone compensation method based on PI control in the current zero-crossing region proposed in the present invention only requires additional segmented judgment and PI parameter adjustment and selection. When the motor enters or exits the current zero-crossing region, the output voltage vector is smoothly transitioned before and after the region switching through the linearly changing PI parameter value. Compared with the traditional dead zone compensation method, the dead zone compensation method based on PI control in the current zero-crossing region proposed in the present invention can achieve effective compensation for the zero current clamping phenomenon without adding an additional current filter;

[0004] Patent: CN114123909A, discloses a dead zone compensation method, device and vehicle for a motor controller, wherein the method includes: obtaining the three-phase current in the abc coordinate system by transforming the current command of the motor controller in the dq rotating coordinate system; calculating the dead zone voltage and on-voltage required to be compensated for each phase according to the three-phase current with reference to the preset dead zone voltage curve and on-voltage curve; obtaining the compensation value of the motor controller based on the dead zone voltage and on-voltage, and compensating the current phase voltage of the motor controller based on the compensation value. The method according to the embodiment of the present invention can accurately compensate for the dead zone of the controller, and is suitable for working conditions such as changes in the controller switching frequency and bus voltage, reducing the degree of current distortion, improving motor performance, and is simple and easy to implement;

[0005] The dead zone compensation technologies currently available in literature and patent searches are all based on current polarity. Although there are various variants and optimization improvements, their essence remains unchanged, and they all rely on current polarity for compensation. This type of method has two disadvantages: ① It relies on current polarity, and actual current sampling inevitably has interference and harmonics, making it difficult to accurately determine the polarity; ② Whether it is the compensation duty cycle or the compensation command voltage, it is impossible to achieve accurate compensation. First of all, the voltage that needs to be compensated is not only affected by the dead zone, but also by the nonlinearity of the power device itself, so it is impossible to accurately compensate the dead zone voltage by directly compensating the duty cycle; in addition, even if the voltage that needs to be compensated can be accurately obtained, the compensation voltage is directly superimposed on the command voltage. Due to the nonlinear characteristics of the device, it is still impossible to output the ideal compensation voltage, which will lead to compensation deviations. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the deficiencies in the prior art, the present invention provides a high-precision dead zone compensation method based on duty cycle calibration, which solves the problem in the prior art that it relies on current polarity, while actual current sampling inevitably has interference and harmonics, and it is difficult to accurately judge the polarity; at the same time, whether it is the compensation duty cycle or the compensation command voltage, it is impossible to achieve accurate compensation. First of all, the voltage to be compensated is not only affected by the dead zone, but also by the nonlinearity of the power device itself, so the dead zone voltage cannot be accurately compensated by directly compensating the duty cycle; in addition, even if the voltage to be compensated can be obtained accurately, but the compensation voltage is directly superimposed on the command voltage, due to the nonlinear characteristics of the device, it is still impossible to output the ideal compensation voltage, which will lead to the problem of compensation deviation.

[0008] (II) Technical solution

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions: a high-precision dead zone compensation method based on duty cycle calibration, the specific operations are as follows:

[0010] S1. Build an offline calibration system. The specific operations are as follows:

[0011] S11, connecting the motor controller to the motor;

[0012] S12, connect the motor controller to the bus power supply, and use an oscilloscope to measure the VDS voltage of the lower bridge arm of the U-phase motor controller (the voltage between the motor U phase and the negative power supply);

[0013] S2, adjusting the motor controller so that the motor works in the current control mode, the motor controller controls the motor U phase current from the negative motor maximum phase current -Ismax interval 30A to the positive motor maximum phase current Ismax;

[0014] S3, output current in motor U phase;

[0015] S4, after the current value is stable, the duty cycle of the U-phase upper bridge output is increased from 0 to 100% at intervals. Due to the existence of motor inductance, after the U-phase current control is stable, changing the duty cycle of a PWM cycle will not cause a sudden change in the phase current;

[0016] S5, recording the VDS voltage of each duty cycle at each current point;

[0017] S6. Process the data and finally obtain a duty cycle data table based on the phase current and the actual output VDS voltage.

[0018] Preferably, in step S2, the interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirement.

[0019] Preferably, in step S4, after stabilization, the interval is adjusted according to the dead zone compensation accuracy requirement.

[0020] Preferably, in step S2, the inverter works in the current control mode, the motor electrical angle is manually set to 0°, and the motor D-axis current command idref is given from the negative motor maximum phase current -Ismax interval 30A (this interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirements) to the positive maximum phase current Ismax. At this time, the motor U-phase current will also follow idref from the negative motor maximum phase current -Ismax interval 30A (this interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirements) to the positive maximum phase current Ismax.

[0021] Preferably, during the actual operation of the motor, SVPWM first calculates the duty ratios DutyU, DutyV, and DutyW of the motor's three-phase UVW, and first calculates the motor's three-phase terminal voltages Vun, Vvn, and Vwn through these three command duty ratios, and then checks the motor's three-phase terminal voltages according to the motor's three-phase terminal voltages. Figure 3 , the duty cycle after three-phase compensation can be obtained. Using the compensated duty cycle for actual output can ensure that the actual output voltage is consistent with the command voltage.

[0022] (III) Beneficial effects

[0023] The present invention provides a high-precision dead zone compensation method based on duty cycle calibration. It has the following beneficial effects:

[0024] (1) The high-precision dead zone compensation method based on duty cycle calibration obtains the duty cycle data required for the actual output voltage under different phase current conditions during the calibration process. The data takes into account all factors affecting the compensation voltage, such as phase current amplitude, power tube nonlinearity, and dead zone time. The actual output voltage obtained is the actual measured voltage. The duty cycle under the current voltage command is obtained by looking up the table to achieve precise voltage compensation.

[0025] (2) The high-precision dead zone compensation method based on duty cycle calibration has a simple implementation process. It does not need to measure the on and off time of the power tube, nor does it need to calculate the influence of the nonlinearity of the power tube. It only needs to perform an offline calibration once. Both the offline calibration process and data processing can be automated. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the motor controller of the present invention being connected to the motor;

[0027] Figure 2 This is a schematic diagram of the VDS voltage recording result of the present invention;

[0028] Figure 3 It is a schematic diagram of the duty cycle data of the phase current and the actual output VDS voltage of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] See also Figure 1-3 The present invention provides a technical solution: a high-precision dead zone compensation method based on duty cycle calibration, the specific operation is as follows:

[0031] S1. Build an offline calibration system. The specific operations are as follows:

[0032] S11, connecting the motor controller to the motor;

[0033] S12, connect the motor controller to the bus power supply, and use an oscilloscope to measure the VDS voltage of the lower bridge arm of the U-phase motor controller (the voltage between the motor U phase and the negative power supply);

[0034] S2, adjusting the motor controller so that the motor works in the current control mode, the motor controller controls the motor U phase current from the negative motor maximum phase current -Ismax interval 30A to the positive motor maximum phase current Ismax, wherein the interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirement;

[0035] Inverter operation and current control mode, the motor electrical angle is artificially set to 0°, and the motor D-axis current command idref is given from the negative motor maximum phase current - Ismax interval 30A (this interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirements) to the positive maximum phase current Ismax. At this time, the motor U-phase current will also follow idref from the negative motor maximum phase current - Ismax interval 30A (this interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirements) to the positive maximum phase current Ismax;

[0036] S3, output current in motor U phase;

[0037] S4, after the current value is stable, the duty cycle of the U-phase upper bridge output is increased from 0 to 100% by 1%. Due to the existence of motor inductance, after the U-phase current control is stable, changing the duty cycle of a PWM cycle will not cause a sudden change in the phase current. Among them, this interval is adjusted according to the dead zone compensation accuracy requirements;

[0038] S5, recording the VDS voltage of each duty cycle at each current point;

[0039] S6. Process the data and finally obtain a duty cycle data table based on the phase current and the actual output VDS voltage.

[0040] During the actual operation of the motor, SVPWM will first calculate the duty ratios DutyU, DutyV, and DutyW of the motor's three-phase UVW. Through these three command duty ratios, the motor's three-phase terminal voltages Vun, Vvn, and Vwn are first calculated. Figure 3 , the duty cycle after three-phase compensation can be obtained. Using the compensated duty cycle for actual output can ensure that the actual output voltage is consistent with the command voltage.

[0041] In summary, the high-precision dead zone compensation method based on duty cycle calibration obtains the duty cycle data required for the actual output voltage under different phase current conditions during the calibration process. This data takes into account all factors affecting the compensation voltage, such as phase current amplitude, power tube nonlinearity, and dead time. The actual output voltage obtained is the real measured voltage. The duty cycle under the current voltage command is obtained by looking up the table to achieve precise voltage compensation.

[0042] The high-precision dead zone compensation method based on duty cycle calibration has a simple implementation process, does not need to measure the on and off time of the power tube, does not need to calculate the influence of the nonlinearity of the power tube, and only needs to do an offline calibration once. The offline calibration process and data processing can be automated.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-precision dead zone compensation method based on duty cycle calibration, characterized in that: The specific operations are as follows: S1. Build an offline calibration system. The specific operations are as follows: S11, connecting the motor controller to the motor; S12, connect the motor controller to the bus power supply, and use an oscilloscope to measure the VDS voltage of the lower bridge arm of the U-phase motor controller, where VDS is the voltage between the motor U phase and the negative power supply; S2, adjusting the motor controller so that the motor works in the current control mode, the motor controller controls the motor U phase current from the negative motor maximum phase current -Ismax interval 30A to the positive motor maximum phase current Ismax; S3, output current in motor U phase; S4, after the current value is stable, the duty cycle of the U-phase upper bridge output is increased from 0 to 100% at intervals. Due to the existence of motor inductance, after the U-phase current control is stable, changing the duty cycle of a PWM cycle will not cause a sudden change in the phase current; S5, recording the VDS voltage of each duty cycle at each current point; S6. Process the data and finally obtain a duty cycle data table based on the phase current and the actual output VDS voltage.

2. The high-precision dead zone compensation method based on duty cycle calibration according to claim 1, characterized in that: In step S2, the interval is adjusted according to the actual maximum phase current of the motor and the dead zone compensation accuracy requirement.

3. The high-precision dead zone compensation method based on duty cycle calibration according to claim 1, characterized in that: In step S4, after stabilization, the interval is adjusted according to the dead zone compensation accuracy requirement.

4. The high-precision dead zone compensation method based on duty cycle calibration according to claim 1, characterized in that: In step S2, the inverter works in current control mode, the motor electrical angle is manually set to 0°, and the motor D-axis current command idref is given from the negative motor maximum phase current -Ismax interval 30A to the positive maximum phase current Ismax. At this time, the motor U-phase current will also follow idref from the negative motor maximum phase current -Ismax interval 30A to the positive maximum phase current Ismax.

5. The high-precision dead zone compensation method based on duty cycle calibration according to claim 1, characterized in that: During the actual operation of the motor, SVPWM will first calculate the duty ratios DutyU, DutyV, and DutyW of the three-phase UVW of the motor, and use DutyU, DutyV, and DutyW to search the duty ratio data table of the VDS voltage in step S6 to obtain the three-phase terminal voltages Vun, Vvn, and Vwn of the motor. Then, the duty ratio after three-phase compensation is calculated based on the three-phase terminal voltages of the motor. The compensated duty ratio is used for actual output to ensure that the actual output voltage is consistent with the command voltage.

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