A method for detecting a current of a three-phase motor

Abstract

The application provides a kind of detection method of three-phase motor current, belong to the control technical field of motor.The detection method includes: obtaining the sampling value of three-phase voltage;Three-phase voltage modulation signal is obtained according to the sampling value calculation;Determine the predetermined position of next current sampling point;According to the interval of the predetermined position, adjust the actual position of the current sampling point;Sample the three-phase current at the actual position.Through the above technical scheme, the three-phase motor current detection method provided by the application adjusts the sampling point interval for each current detection, so that each sampling can avoid sampling current spikes while ensuring to retain the change characteristics of current itself, thereby improving the accuracy of sampling current.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and more specifically to a method for detecting the current of a three-phase motor. Background Technology

[0002] In the field of motor control, motor current detection is a core and critical component affecting control performance. Deviations in the current sampling value can lead to increased motor harmonic components, increased electromagnetic noise, and torque pulsation. Large delays between current detection and current loop control reduce the current loop bandwidth, decrease the stability margin of the control system, increase dynamic overshoot, and prolong the settling time. Therefore, improving the accuracy and real-time performance of current sampling is of great significance to control performance.

[0003] Inverters typically sample the motor current using a Hall sensor or sampling resistor connected in series between the output side and the motor, or a sampling resistor connected in series between the lower bridge switch and the negative bus. When the inverter switch operates, a momentary spike in current appears, which is an interference signal that does not reflect the true motor current. Regardless of the sampling method used, this current spike must be avoided. However, conventional current detection methods in existing technology cannot effectively overcome this defect. Summary of the Invention

[0004] The purpose of this invention is to provide a method for detecting the current of a three-phase motor, which can improve the detection effect of the current.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for detecting the current of a three-phase motor, comprising:

[0006] Obtain sampled values ​​of the three-phase voltage;

[0007] The modulation signal of the three-phase voltage is calculated based on the sampled values;

[0008] Determine the predetermined location of the next current sampling point;

[0009] The actual position of the current sampling point is adjusted according to the range of the predetermined position;

[0010] The three-phase current is sampled at the actual location.

[0011] Optionally, the modulation signal for obtaining the three-phase voltage calculated based on the sampled values ​​includes:

[0012] The Clark and Park transforms are used to obtain the d-axis and q-axis currents based on the sampled values.

[0013] Based on the d-axis current and q-axis current, the d-axis voltage and q-axis voltage are generated using the current loop control principle.

[0014] The modulation signal is calculated based on the d-axis voltage, q-axis voltage, rotor angle, and switching period.

[0015] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0016] When the predetermined position is in the underflow interval of the triangular wave and / or the increment interval of the triangular wave counter, the modulation signal is sorted according to the relationship of pulse width from small to large to obtain the minimum pulse width, the median pulse width, and the maximum pulse width.

[0017] Calculate the pulse sampling time according to formula (1).

[0018] (1)

[0019] in, The pulse sampling time is... This is the minimum value of the pulse width.

[0020] Determine whether the pulse sampling time is greater than the preset minimum sampling window time;

[0021] If the pulse sampling time is determined to be greater than the preset minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (2).

[0022] (2)

[0023] in, The time interval is... The next underflow point after the current position. This is the current location.

[0024] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0025] If the pulse sampling time is determined to be less than or equal to the preset minimum sampling window time, the pulse midpoint difference is calculated according to formula (3).

[0026] (3)

[0027] in, The pulse midpoint difference, This is the median value of the pulse width. This is the minimum value of the pulse width;

[0028] Determine whether the pulse midpoint difference is greater than the minimum sampling window time;

[0029] If the pulse midpoint difference is determined to be greater than the minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (4).

[0030] , (4).

[0031] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0032] If the pulse midpoint difference is less than or equal to the minimum sampling window time, determine whether the current modulation mode is CPWM mode or DPWM mode;

[0033] If the current modulation mode is determined to be CPWM mode, the time interval between the actual position and the current position is calculated according to formula (5).

[0034] (5)

[0035] in, This is the maximum value of the pulse width.

[0036] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0037] If the current modulation mode is determined to be DPWM mode, the time interval between the actual position and the current position is calculated according to formula (6).

[0038] (6)

[0039] in, The period matching value of the triangular wave of the modulated signal. This is the time for program correction.

[0040] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0041] When the predetermined position is in the overflow interval of the triangular wave and / or the count-down interval of the triangular wave counter, the modulation signal is sorted according to the relationship of pulse width from small to large to obtain the minimum pulse width, the median pulse width, and the maximum pulse width.

[0042] Calculate the pulse sampling time according to formula (7).

[0043] (7)

[0044] in, The pulse sampling time, The period matching value of the triangular wave of the modulated signal. The maximum value of the pulse width;

[0045] Determine whether the pulse sampling time is greater than the preset minimum sampling window time;

[0046] If the pulse sampling time is determined to be greater than the preset minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (8).

[0047] (8)

[0048] in, The time interval is... This is the next underflow point after the current position.

[0049] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0050] If the pulse sampling time is determined to be less than or equal to the preset minimum sampling window time, the pulse midpoint difference is calculated according to formula (9).

[0051] (9)

[0052] in, The pulse midpoint difference, This is the median value of the pulse width;

[0053] Determine whether the pulse midpoint difference is greater than the minimum sampling window time;

[0054] If the pulse midpoint difference is determined to be greater than the minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (10).

[0055] , (10).

[0056] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0057] If the pulse midpoint difference is less than or equal to the minimum sampling window time, determine whether the current modulation mode is CPWM mode or DPWM mode;

[0058] If the current modulation mode is determined to be CPWM mode, the time interval between the actual position and the current position is calculated according to formula (11).

[0059] (11)

[0060] in, This is the minimum value of the pulse width.

[0061] Optionally, adjusting the actual position of the current sampling point according to the interval where the predetermined position is located specifically includes:

[0062] If the current modulation mode is determined to be DPWM mode, the time interval between the actual position and the current position is calculated according to formula (12).

[0063] (12)

[0064] in, This is the time for program correction.

[0065] Through the above technical solution, the three-phase motor current detection method provided by the embodiments of the present invention adjusts the sampling point interval for each current detection, so that the current spikes are avoided while preserving the changing characteristics of the current itself during each sampling, thereby improving the accuracy of the sampled current.

[0066] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0067] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0068] Figure 1 This is a flowchart of a method for detecting the current of a three-phase motor according to an embodiment of the present invention;

[0069] Figure 2 This is a flowchart of a method for detecting the current of a three-phase motor according to an embodiment of the present invention;

[0070] Figure 3 This is a flowchart of a method for detecting the current of a three-phase motor according to an embodiment of the present invention;

[0071] Figure 4 This is a flowchart of a method for detecting the current of a three-phase motor according to an embodiment of the present invention;

[0072] Figure 5 This is a sampled waveform diagram of the current of a three-phase motor according to an embodiment of the present invention. Detailed Implementation

[0073] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0074] In embodiments of the present invention, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used to describe the relative positional relationships of components in relation to the directions shown in the accompanying drawings or in relation to the vertical, perpendicular, or gravitational directions.

[0075] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0076] like Figure 1 The diagram shows a flowchart of a three-phase motor current detection method according to an embodiment of the present invention. Figure 1 In this context, the detection method may include:

[0077] In step S10, sampled values ​​of the three-phase voltage are obtained;

[0078] In step S11, the modulation signal of the three-phase voltage is calculated based on the sampled values;

[0079] In step S12, the predetermined position of the next current sampling point is determined;

[0080] In step S13, the actual position of the current sampling point is adjusted according to the interval of the predetermined position;

[0081] In step S14, the three-phase current is sampled at the actual location.

[0082] In one embodiment of the present invention, steps S10 and S11 are used to acquire the modulation signal of the output three-phase voltage. Specifically, step S11 may include, for example: Figure 2 The method shown in the diagram. Figure 2 In this context, the method may include:

[0083] In step S20, Clark transform and Park transform are used to obtain the d-axis current and q-axis current based on the sampled values;

[0084] In step S21, the d-axis voltage and q-axis voltage are generated based on the current loop control principle according to the d-axis current and q-axis current;

[0085] In step S22, the modulation signal is calculated based on the d-axis voltage, q-axis voltage, rotor angle, and switching period.

[0086] Step S13 is used to determine the actual location of the next current sampling point. Specifically, before determining the actual location, a minimum sampling point can be pre-designed, and then the minimum sampling point can be corrected based on whether it is located within a preset interval, thereby determining the actual location. The sampling waveform diagram of the three-phase current can be as follows: Figure 5 As shown. In Figure 5 In the process, the single interval where the voltage of the triangular wave is lower than the minimum threshold of the three-phase voltage CMPU can be the underflow interval (interval T1), and the extreme value in this underflow interval is the underflow point (point value T0); the boost interval of the triangular wave can be the increment interval of the triangular wave counter (i.e., interval T2); the single interval where the voltage of the triangular wave is higher than the minimum threshold of the three-phase voltage CMPU can be the overflow interval (interval T3); the decrement interval of the triangular wave can be the decrement interval of the triangular wave counter (i.e., interval T4).

[0087] Specifically, methods for determining the actual location may include, for example: Figure 3 and Figure 4 The method shown is illustrated. Figure 3 In this context, the method may include:

[0088] In step S30, when the predetermined position is in the underflow interval of the triangular wave and / or the increment interval of the triangular wave counter, the modulation signal is sorted according to the relationship of pulse width from small to large to obtain the minimum pulse width, the median pulse width, and the maximum pulse width.

[0089] In step S31, the pulse sampling time is calculated according to formula (1).

[0090] (1)

[0091] in, The pulse sampling time, This is the minimum pulse width.

[0092] In step S32, it is determined whether the pulse sampling time is greater than the preset minimum sampling window time;

[0093] In step S33, if the pulse sampling time is determined to be greater than the preset minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (2).

[0094] (2)

[0095] in, For time intervals, The next underflow point after the current position. This is the current location.

[0096] In step S34, if the pulse sampling time is determined to be less than or equal to the preset minimum sampling window time, the pulse intermediate difference is calculated according to formula (3).

[0097] (3)

[0098] in, The pulse midpoint difference This is the median value of the pulse width. This is the minimum pulse width.

[0099] In step S35, it is determined whether the pulse mid-difference is greater than the minimum sampling window time;

[0100] In step S36, if the pulse midpoint difference is determined to be greater than the minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (4).

[0101] , (4).

[0102] In step S37, if the pulse mid-difference is less than or equal to the minimum sampling window time, it is determined whether the current modulation mode is CPWM mode or DPWM mode.

[0103] In step S38, if the current modulation mode is determined to be CPWM mode, the time interval between the actual position and the current position is calculated according to formula (5).

[0104] (5)

[0105] in, This represents the maximum pulse width.

[0106] In step S39, if the current modulation mode is determined to be DPWM mode, the time interval between the actual position and the current position is calculated according to formula (6).

[0107] (6)

[0108] in, The period matching value of the triangular wave of the modulated signal. This is the time for program correction.

[0109] exist Figure 4 In this context, the method may include:

[0110] In step S40, when the predetermined position is in the overflow interval of the triangular wave and / or the count-down interval of the triangular wave counter, the modulation signal is sorted according to the relationship of pulse width from small to large to obtain the minimum pulse width, the median pulse width, and the maximum pulse width.

[0111] In step S41, the pulse sampling time is calculated according to formula (7).

[0112] (7)

[0113] in, For pulse sampling time, The period matching value of the triangular wave of the modulated signal. This represents the maximum pulse width.

[0114] In step S42, it is determined whether the pulse sampling time is greater than the preset minimum sampling window time;

[0115] In step S43, if the pulse sampling time is determined to be greater than the preset minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (8).

[0116] (8)

[0117] in, For time intervals, This is the next underflow point after the current position.

[0118] In step S44, if the pulse sampling time is determined to be less than or equal to the preset minimum sampling window time, the pulse intermediate difference is calculated according to formula (9).

[0119] (9)

[0120] in, The pulse midpoint difference This is the median value of the pulse width;

[0121] In step S45, it is determined whether the pulse mid-difference is greater than the minimum sampling window time;

[0122] In step S46, if the pulse midpoint difference is determined to be greater than the minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (10).

[0123] , (10).

[0124] In step S47, if the pulse mid-difference is less than or equal to the minimum sampling window time, it is determined whether the current modulation mode is CPWM mode or DPWM mode.

[0125] In step S48, if the current modulation mode is determined to be CPWM mode, the time interval between the actual position and the current position is calculated according to formula (11).

[0126] (11)

[0127] in, This is the minimum pulse width.

[0128] In step S49, if the current modulation mode is determined to be DPWM mode, the time interval between the actual position and the current position is calculated according to formula (12).

[0129] (12)

[0130] in, This is the time for program correction.

[0131] Through the above technical solution, the three-phase motor current detection method provided by the embodiments of the present invention adjusts the sampling point interval for each current detection, so that the current spikes are avoided while preserving the changing characteristics of the current itself during each sampling, thereby improving the accuracy of the sampled current.

[0132] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0133] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0134] Those skilled in the art will understand that all or part of the steps in the methods described above can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0135] Furthermore, various different embodiments of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A method for detecting the current of a three-phase motor, characterized in that, The detection method includes: Obtain sampled values ​​of the three-phase voltage; The modulation signal of the three-phase voltage is calculated based on the sampled values; Determine the predetermined location of the next current sampling point; The actual position of the current sampling point is adjusted according to the range of the predetermined position; The three-phase current is sampled at the actual location; Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: When the predetermined position is in the underflow interval of the triangular wave and / or the increment interval of the triangular wave counter, the modulation signal is sorted according to the relationship of pulse width from small to large to obtain the minimum pulse width, the median pulse width, and the maximum pulse width. Calculate the pulse sampling time according to formula (1). ，（1） in, The pulse sampling time is... This is the minimum value of the pulse width; Determine whether the pulse sampling time is greater than the preset minimum sampling window time; If the pulse sampling time is determined to be greater than the preset minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (2). ，（2） in, The time interval is... The next underflow point after the current position. Current position; Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: If the pulse sampling time is determined to be less than or equal to the preset minimum sampling window time, the pulse midpoint difference is calculated according to formula (3). ，（3） in, The pulse midpoint difference is denoted as , and the pulse width midpoint is denoted as . This is the minimum value of the pulse width; Determine whether the pulse midpoint difference is greater than the minimum sampling window time; If the pulse midpoint difference is determined to be greater than the minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (4). ，（4）。 2. The detection method according to claim 1, characterized in that, The modulation signal for obtaining the three-phase voltage calculated based on the sampled values ​​includes: The Clark and Park transforms are used to obtain the d-axis and q-axis currents based on the sampled values. Based on the d-axis current and q-axis current, the d-axis voltage and q-axis voltage are generated using the current loop control principle. The modulation signal is calculated based on the d-axis voltage, q-axis voltage, rotor angle, and switching period.

3. The detection method according to claim 2, characterized in that, Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: If the pulse midpoint difference is less than or equal to the minimum sampling window time, determine whether the current modulation mode is CPWM mode or DPWM mode; If the current modulation mode is determined to be CPWM mode, the time interval between the actual position and the current position is calculated according to formula (5). ，（5） in, This is the maximum value of the pulse width.

4. The detection method according to claim 3, characterized in that, Specifically, it includes: If the current modulation mode is determined to be DPWM mode, the time interval between the actual position and the current position is calculated according to formula (6). ，（6） in, The period matching value of the triangular wave of the modulated signal. This is the time for program correction.

5. The detection method according to claim 1, characterized in that, Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: When the predetermined position is in the overflow interval of the triangular wave and / or the count-down interval of the triangular wave counter, the modulation signal is sorted according to the relationship of pulse width from small to large to obtain the minimum pulse width, the median pulse width, and the maximum pulse width. Calculate the pulse sampling time according to formula (7). ，（7） in, The pulse sampling time, The period matching value of the triangular wave of the modulated signal. The maximum value of the pulse width; Determine whether the pulse sampling time is greater than the preset minimum sampling window time; If the pulse sampling time is determined to be greater than the preset minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (8). ，（8） in, The time interval is... This is the next underflow point after the current position.

6. The detection method according to claim 5, characterized in that, Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: If the pulse sampling time is determined to be less than or equal to the preset minimum sampling window time, the pulse midpoint difference is calculated according to formula (9). ，（9） in, The pulse midpoint difference, This is the median value of the pulse width; Determine whether the pulse midpoint difference is greater than the minimum sampling window time; If the pulse midpoint difference is determined to be greater than the minimum sampling window time, the time interval between the actual position and the current position is calculated according to formula (10). ，（10）； Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: If the pulse midpoint difference is less than or equal to the minimum sampling window time, determine whether the current modulation mode is CPWM mode or DPWM mode; If the current modulation mode is determined to be CPWM mode, the time interval between the actual position and the current position is calculated according to formula (11). ，（11） in, This is the minimum value of the pulse width.

7. The detection method according to claim 6, characterized in that, Adjusting the actual position of the current sampling point according to the interval of the predetermined position specifically includes: If the current modulation mode is determined to be DPWM mode, the time interval between the actual position and the current position is calculated according to formula (12). ，（12） in, This is the time for program correction.

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