Current sampling method and power equipment for three-phase motor

Abstract

The present application discloses a current sampling method and power equipment for a three-phase motor, wherein the current sampling method includes obtaining a current sampling value of each sampling phase current in the three-phase motor, the current sampling value including a current sampling value within a first sampling window, a current sampling value within a second sampling window, and a current sampling value at a first overflow point; then, filtering out a valid current sampling value from the current sampling value within the first sampling window, the current sampling value within the second sampling window, and the current sampling value at the first overflow point; finally, calculating the filtered three-phase current value of the motor based on the valid current sampling value. The power equipment includes a three-phase motor and a processor, and the processor can obtain the filtered three-phase current value of the three-phase motor through the current sampling method of the present application. The current sampling method and power equipment for the three-phase motor of the present application can realize multi-point sampling and filtering processing of the three-phase current, effectively reducing the influence of noise interference on the current, and is conducive to improving the control accuracy of the motor.

Description

Technical Field

[0001] The present application relates to the field of motor technology, and in particular to a current sampling method and power equipment for a three-phase motor. Background Art

[0002] In motor control, current sampling is often required to detect the motor's output torque. Therefore, current sampling is crucial for precise motor control. Common current sampling schemes for motor control include three-resistor sampling, two-resistor sampling, and single-resistor sampling. Three-resistor and two-resistor sampling schemes are relatively cost-effective and easy to implement, making them more widely used. However, current three-resistor and two-resistor sampling schemes only perform single-point sampling. When the motor current fluctuates due to noise interference, large errors in current sampling can occur, resulting in reduced motor control accuracy. Summary of the Invention

[0003] The main purpose of this application is to provide a current sampling method and power equipment for a three-phase motor, which can realize multi-point sampling and filtering processing of three-phase current, effectively reduce the impact of noise interference on current, and help improve motor control accuracy.

[0004] In order to achieve the above objectives, this application adopts the following technical solutions:

[0005] A current sampling method for a three-phase motor, comprising:

[0006] Acquire a current sampling value of each sampling phase current in the three-phase motor, wherein the current sampling value includes a current sampling value within a first sampling window, a current sampling value within a second sampling window, and a current sampling value at a first overflow point;

[0007] Filter out a valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value of the first overflow point;

[0008] The filtered three-phase current values ​​of the motor are calculated according to the effective current sampling values.

[0009] Preferably, the filtering out of the valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value at the first overflow point comprises the following steps:

[0010] Obtaining a switching duty cycle of a second switching cycle according to a loop calculation result of each sampling phase in the first switching cycle, thereby obtaining the first sampling window according to the switching duty cycle of the second switching cycle, wherein the first sampling window is located within the second switching cycle;

[0011] Obtaining a switching duty cycle of a third switching cycle according to a loop calculation result of each sampling phase in the second switching cycle, thereby obtaining a second sampling window according to the switching duty cycle of the third switching cycle, wherein the second sampling window is located within the third switching cycle;

[0012] The first sampling window, the time point of the first overflow point, and the second sampling window are sequentially connected to form a temporally continuous sampling window;

[0013] Taking the time point of the first overflow point as the symmetric center, the current sampling values ​​in symmetrical time regions are selected from the first sampling window and the second sampling window as valid current sampling values.

[0014] Furthermore, the method of selecting the current sampling values ​​in symmetrical time regions from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the effective current sampling values ​​includes the following steps:

[0015] Taking a shorter time period corresponding to the first sampling window and the second sampling window as a first time period, and intercepting a longer time period corresponding to the first sampling window and the second sampling window according to the first time period to obtain a second time period, where the second time period is symmetrical to the first time period about the time point of the first overflow point;

[0016] The sampling points in the time region formed by combining the first time period, the time point at which the first overflow point occurs, and the second time period are used as effective current sampling values.

[0017] Furthermore, the method of selecting the current sampling values ​​in symmetrical time regions from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the effective current sampling values ​​includes the following steps:

[0018] intercepting time periods corresponding to the first sampling window and the second sampling window respectively to obtain a third time period and a fourth time period, wherein the third time period and the fourth time period are symmetrical about a time point where the first overflow point is located;

[0019] The effective current sampling value is screened out from the time region formed by combining the third time period, the time point at which the first overflow point is located, and the fourth time period.

[0020] Furthermore, the loop calculation result is obtained according to the torque output requirement of the motor and the working condition of the motor.

[0021] Furthermore, the time region of the loop calculation within the third switching cycle is the time region from the end of the second sampling window to the second overflow point, the second overflow point is separated from the first overflow point by one switching cycle, and the time point of the second overflow point is later than the time point of the first overflow point.

[0022] A power device includes a three-phase motor and a processor, wherein the processor is connected to the three-phase motor and configured to:

[0023] Obtaining a current sampling value of each sampling phase current in the three-phase motor, wherein the current sampling value includes a current sampling value within a first sampling window, a current sampling value within a second sampling window, and a current sampling value at a first overflow point;

[0024] Filter out a valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value of the first overflow point;

[0025] The filtered three-phase current values ​​of the motor are calculated according to the effective current sampling values.

[0026] Preferably, the processor is configured to filter out a valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value at the first overflow point, specifically:

[0027] The processor is configured to obtain a switching duty cycle of a second switching cycle based on a loop calculation result of each sampling phase in the first switching cycle, thereby obtaining the first sampling window based on the switching duty cycle of the second switching cycle, wherein the first sampling window is located within the second switching cycle;

[0028] The processor is configured to obtain a switching duty cycle of a third switching cycle based on a loop calculation result of each sampling phase in the second switching cycle, thereby obtaining a second sampling window based on the switching duty cycle of the third switching cycle, wherein the second sampling window is located within the third switching cycle;

[0029] The first sampling window, the time point of the first overflow point, and the second sampling window are sequentially connected to form a temporally continuous sampling window;

[0030] The processor is further configured to filter the current sampling values ​​in a symmetrical time region from the first sampling window and the second sampling window with the time point of the first overflow point as a symmetrical center as valid current sampling values.

[0031] Furthermore, the processor is further configured to filter the current sampling values ​​in a symmetrical time region from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the valid current sampling values, specifically:

[0032] The processor is configured to use a shorter time period corresponding to the first sampling window and the second sampling window as a first time period, and intercept a longer time period corresponding to the first sampling window and the second sampling window according to the first time period to obtain a second time period, wherein the second time period is symmetrical to the first time period about a time point where the first overflow point is located;

[0033] The processor is configured to take a sampling point within the time region formed by combining the first time period, the time point at which the first overflow point occurs, and the second time period as an effective current sampling value.

[0034] Furthermore, the processor is further configured to filter the current sampling values ​​in a symmetrical time region from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the valid current sampling values, specifically:

[0035] The processor is configured to intercept time periods corresponding to the first sampling window and the second sampling window respectively to obtain a third time period and a fourth time period, wherein the third time period and the fourth time period are symmetrical about a time point where the first overflow point is located;

[0036] The processor is configured to filter out the effective current sampling value from the time region formed by combining the third time period, the time point at which the first overflow point occurs, and the fourth time period.

[0037] Compared with the prior art, this application has the following advantages:

[0038] 1. This application can realize multi-point sampling and filtering processing of three-phase current, which can significantly reduce noise interference, obtain more accurate three-phase current values, and thus effectively improve the control accuracy of the three-phase motor.

[0039] 2. The present application can screen out effective current sampling values ​​whose sampling time points are symmetrical with respect to the time point where the first overflow point is located. Based on this, when performing mean filtering calculation on the effective current sampling values, the calculation results can be made basically equivalent to the current values ​​obtained by sampling at the time point where the first overflow point is located. The only difference is that the method of the present application performs noise filtering. Therefore, the method of the present application can obtain high-precision three-phase current values ​​without introducing additional loop delays.

[0040] 3. The present application can flexibly adjust the number of current sampling values ​​and the sampling window size according to actual conditions. For example, when filtering requirements are high, the number of current sampling values ​​can be appropriately increased, and the sampling window can be appropriately expanded. When it is necessary to limit the computation time, the number of current sampling values ​​can be appropriately reduced, and the sampling window can be appropriately narrowed. Moreover, the present application method is applicable to a variety of three-phase inverters, so the application of the present application method can be very flexible and extensive.

[0041] 4. This application can finely screen the current sampling values ​​according to the switching duty cycle of the historical switching cycle to ensure that the current sampling values ​​used to calculate the three-phase current values ​​are all available, thereby avoiding increasing the sampling error and ensuring the accuracy of the sampling.

[0042] 5. After obtaining the current sampling values ​​of the three sampling phases, the present application can discard the current sampling value of the sampling phase with the smallest sampling window, and then reconstruct the current value of the removed sampling phase through Kirchhoff's current law. This can reduce the error, ensure that the three-phase current value satisfies Kirchhoff's current law, and further improve the sampling accuracy of the three-phase current value.

[0043] 6. The three-phase motor control accuracy of the present application method can be adjusted along with the size of the switch duty cycle. For example, for the low-side current sampling method, the number of effective current sampling values ​​can increase as the switch duty cycle decreases, which can be beneficial to the improvement of the filtering effect. Therefore, in scenarios such as low current and low speed conditions that require high-precision motor control, the present application method can provide better motor control effects. For high current and high speed conditions, although the increase in duty cycle will weaken the current filtering effect, because the noise interference of high current and high speed conditions is relatively small, even if the filtering effect is weakened, it will basically not affect the motor control effect.

[0044] 7. In the present method, the timer can enter the loop calculation at any time point between the end of the sampling window and the underflow point of the second switching cycle. After the loop calculation is completed, the comparison value is updated. Then, the timer can normally update the switching duty cycle of the third switching cycle based on the updated comparison value. Therefore, the present method does not affect the normal operation of the timer, and the timer also has sufficient time to perform the loop calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0046] Figure 1 This is an application scenario diagram of the current sampling method for a three-phase motor in Example 1 of the present application.

[0047] Figure 2A This is a schematic diagram of the counting waveform of the timer and the switching state waveform of the A-phase bridge arm in Example 1 of the present application.

[0048] Figure 2B This is a schematic diagram of the counting waveform of the timer and the switching state waveform of the B-phase bridge arm in Example 1 of the present application.

[0049] Figure 2C This is a schematic diagram of the counting waveform of the timer and the switching state waveform of the C-phase bridge arm in Example 1 of the present application.

[0050] Figure 3 This is a flow chart of the current sampling method for a three-phase motor in Example 1 of the present application.

[0051] Figure 4 for Figure 3 Flowchart of step S32 in .

[0052] Figure 5 This is a schematic diagram of the power equipment of an embodiment of the present application.

[0053] Description of main component symbols

[0054] Power Equipment 100

[0055] Three-phase inverter 10

[0056] Timer 20

[0057] Three-phase motor 30

[0058] Processor 40

[0059] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings 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 in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0061] In the description of this application, it should be understood that the terms "first", "second" and "third" are used to distinguish different objects rather than to describe a specific order, and therefore should not be understood as limiting this application.

[0062] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0063] The terms "comprise," "comprising," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or modules is not limited to the listed steps or modules but may optionally include steps or modules not listed, or may optionally include other steps or modules inherent to the process, method, product, or apparatus.

[0064] In motor control, a three-phase motor is typically electrically connected to a three-phase inverter, which is then electrically connected to a timer. The timer can output a PWM signal to control the three-phase inverter, which converts DC power into three-phase current for the three-phase motor. Once energized, the three-phase motor can rotate and output torque. During this process, the three-phase current can be sampled using sampling resistors in the three-phase inverter, allowing precise control of the three-phase motor's output based on the collected three-phase current. However, currently, motor current is only sampled at a single point when the timer generates an overflow or underflow event. Due to the single sampling point, the sampling result is easily affected by noise interference and may produce deviations, resulting in reduced motor control accuracy.

[0065] To this end, the present invention proposes a current sampling method for a three-phase motor that can implement multi-point current sampling and filtering. This effectively filters out noise interference, reduces current sampling errors, and thus improves the control accuracy of the three-phase motor. The following uses Examples 1 to 6 as examples to describe the current sampling method for a three-phase motor provided by the present invention in detail.

[0066] Example 1

[0067] See also Figure 1 , Figure 1 The application scenario of the current sampling method of the three-phase motor in the embodiment 1 is shown. The application scenario includes a three-phase inverter 10, a timer 20 and a three-phase motor 30. Specifically, Figure 1As shown, the three-phase inverter 10 has three bridge arms. The upper power switch M1 and the lower power switch M4 are electrically connected to form the A-phase bridge arm, the upper power switch M3 and the lower power switch M6 are electrically connected to form the B-phase bridge arm, and the upper power switch M5 and the lower power switch M2 are electrically connected to form the C-phase bridge arm. The connections between the upper and lower power switches in the A-phase bridge arm, the B-phase bridge arm, and the C-phase bridge arm are electrically connected to the A, B, and C phase lines of the three-phase motor 30, respectively. The power switches M1-M6 can be power electronic switching devices such as transistors or field-effect transistors, and this application is not limited thereto.

[0068] The three-phase inverter 10 adopts a low-side current sampling method, that is, the upper power switches M1, M3, and M5 receive the DC voltage V DC , the lower power switches M4, M6, and M2 are grounded through the corresponding sampling resistors R1, R2, and R3 respectively. It can be understood that Figure 1 The A, B, and C phases of the three-phase motor 30 are all sampling phases.

[0069] In the first embodiment, the timer 20 uses an up / down counting (i.e., up-down) mode for counting. Specifically, the timer 20 starts counting up from 0. When the count reaches the set value, the timer 20 generates an overflow event, and then the timer 20 counts down from the set value. When the count reaches 0, the timer 20 generates an underflow event, thereby completing a cycle. At the moment of generating an underflow event, the timer 20 automatically enters the counting of the next cycle. The counting process of the next cycle is the same as that of the previous cycle, so it will not be repeated here. The counting waveform of the timer 20 is presented as a triangular wave, which can be seen in detail in FIG. Figures 2A to 2C .

[0070] Understandably, Figures 2A to 2C In the figure, the highest point of the count waveform of timer 20 represents that timer 20 has counted to the set value, generating an overflow event. Therefore, the overflow event generated by timer 20 (i.e., the highest point of the count waveform) is called the overflow point of timer 20. The lowest point of the count waveform of timer 20 represents that timer 20 has counted to 0, generating an underflow event. Therefore, the underflow event generated by timer 20 (i.e., the lowest point of the count waveform) is called the underflow point of timer 20.

[0071] Timer 20 sets a corresponding comparison value based on the torque output requirement and operating conditions of the three-phase motor 30. This allows the count value within each cycle to be compared with the set comparison value. When the count value is less than the comparison value, a first level (e.g., a high level) is generated. When the count value is greater than or equal to the comparison value, a second level (e.g., a low level) different from the first level is generated, thereby forming a pulse width modulation (PWM) signal. Based on this, timer 20 can generate six PWM signals to control the on / off status of each power switch within each cycle.

[0072] For examples, please refer to Figures 2A to 2C , Figures 2A to 2C The switching state waveforms for the A-phase, B-phase, and C-phase bridge arms are shown. The switching state waveforms for all three bridge arms appear as rectangular waves. In each bridge arm's switching state waveform, a high level of 1 indicates that the upper power switch of that bridge arm is on and the lower power switch of that bridge arm is off; a low level of 0 indicates that the lower power switch of that bridge arm is on and the upper power switch of that bridge arm is off.

[0073] It can be understood that since the timer 20 controls the switching states of the three bridge arms in each cycle, the cycle of the timer 20 can be referred to as a switching cycle. The proportion of the on-time duration of the upper power switch of each bridge arm in a switching cycle (i.e., the proportion of the high level in the switching state waveform of each bridge arm in a switching cycle) can be referred to as the switching duty cycle of the bridge arm in that switching cycle.

[0074] Among them, when the timer 20 controls the lower power switches M4, M6, and M2 to be turned on at the same time and the upper power switches M1, M3, and M5 to be turned off at the same time (including the time point where the underflow point is located), the three-phase currents of the three-phase motor 30 correspond one-to-one to the currents flowing through the three sampling resistors. Therefore, the currents flowing through the sampling resistors can be sampled at this time to obtain the current sampling values ​​of the three phases A, B, and C.

[0075] The timer 20 performs loop calculation in one switching cycle to update the comparison value. Therefore, in the next switching cycle, the corresponding PWM signal can be updated according to the updated comparison value, thereby updating the switching duty cycle of the next switching cycle.

[0076] Please refer to Figure 3 , below is Figure 1 Taking the three-phase motor 30, three-phase inverter 10 and timer 20 as an example, the current sampling method of the three-phase motor of the first embodiment of the present application is introduced in detail. Figures 2A to 2CAs shown, any three consecutive switching cycles of the timer 20 are defined as the first switching cycle T1, the second switching cycle T2, and the third switching cycle T3. The underflow point of the second switching cycle T2 is defined as the first overflow point, and the underflow point of the third switching cycle T3 is defined as the second overflow point.

[0077] like Figure 3 As shown, the current sampling method of the three-phase motor includes the following steps:

[0078] Step S31 : obtaining a current sampling value of each sampling phase current of the three-phase motor 30 .

[0079] It can be understood that in step S31, Figure 1 The three-phase inverter 10 shown performs current sampling, and specifically, the three-phase currents are sequentially sampled within a time period D that is symmetrical with respect to the time point of the first overflow point, thereby obtaining a plurality of current sampling values.

[0080] Among them, the size of the time period D that is symmetrical about the time point where the first overflow point is located can be adaptively set according to actual conditions, and this application does not impose any restrictions on this.

[0081] The number of current sampling values ​​obtained is an odd number, for example, 7, 15, 23 or other odd numbers, and this application does not impose any limitation on this.

[0082] The acquired current sampling values ​​specifically include the current sampling value at the first overflow point, the current sampling value in the second switching cycle T2 and before the time point of the first overflow point, and the current sampling value in the third switching cycle T3. The current sampling values ​​in the second switching cycle T2 and before the time point of the first overflow point and the current sampling values ​​in the third switching cycle T3 are not only the same in quantity, but also symmetrical in sampling time points about the time point of the first overflow point.

[0083] Step S32: Filter out effective current sampling values ​​from the current sampling values.

[0084] It can be understood that step S32 is mainly based on the consideration that the on-off of the power switch easily causes the current to jump. If multiple current sampling values ​​are obtained when the power switch of the three-phase inverter 10 is in different on-off states, the calculated three-phase current value may not satisfy Kirchhoff's current law (i.e., the sum of the three-phase currents A, B, and C is 0:I A +I B +I C=0), obviously, such current sampling values ​​have significant sampling errors and are therefore unusable. Although lower power switches M4, M6, and M2 are simultaneously turned on at the time of the first overflow point, they are not always turned on simultaneously during the period before the first overflow point in the second switching cycle T2 and during the period of the third switching cycle T3. Therefore, not all current sampling values ​​in step S31 are usable. Therefore, the current sampling values ​​need to be screened in step S32 to ensure sampling accuracy.

[0085] Step S33: Calculating the filtered three-phase current value of the three-phase motor 30 according to the effective current sampling value.

[0086] In the first embodiment, because timer 20 updates the switching duty cycle for each switching cycle, the switching duty cycles of the second switching cycle T2 and the third switching cycle T3 are not necessarily the same. That is, the on-time periods of the lower power switches M4, M6, and M2 in the second switching cycle T2 and the third switching cycle T3 are not necessarily the same. This means that the number of current sampling values ​​obtained during the on-time period of the second switching cycle T2 is not necessarily the same as the number of current sampling values ​​obtained during the on-time period of the third switching cycle T3. Therefore, in step S32, the current sampling values ​​of the second switching cycle T2 and the third switching cycle T3 can be finely filtered based on their respective switching duty cycles.

[0087] For examples, please refer to Figure 4 , step S32 may include the following steps:

[0088] Step S321: Based on the loop calculation results of each sampling phase in the first switching cycle T1 (i.e., the comparison value used by the timer 20 in the second switching cycle T2), the switching duty cycle of the second switching cycle T2 is obtained, thereby obtaining a first sampling window based on the switching duty cycle of the second switching cycle T2. The first sampling window is located during the low-level period of the second switching cycle T2.

[0089] Step S322: Based on the loop calculation results of each sampling phase in the second switching cycle T2 (i.e., the comparison value used by timer 20 in the third switching cycle T3), the switching duty cycle of the third switching cycle T3 is obtained, thereby obtaining a second sampling window based on the switching duty cycle of the third switching cycle T3. The second sampling window is located during the low-level period of the third switching cycle T3.

[0090] Step S323: The first sampling window, the time point where the first overflow point is located, and the second sampling window are sequentially connected to form a temporally continuous sampling window.

[0091] For example, Figures 2A to 2C As shown, the first sampling window of phase A is expressed as Figure 2AW in 1A , the second sampling window of phase A is expressed as Figure 2A W in 2A , the time point of the first overflow point is expressed as tp. 1A , tp and W 2A Connected to the sampling window W of phase A A .

[0092] The first sampling window of phase B is expressed as Figure 2B W in 1B , the second sampling window of phase B is expressed as Figure 2B W in 2B .W 1B , tp and W 2B The sampling window W of phase B is connected B .

[0093] The first sampling window of phase C is expressed as Figure 2C W in 1C , the second sampling window of phase C is expressed as Figure 2C W in 2C .W 1C , tp and W 2C Sampling window W connected to phase C C .

[0094] The size of the first sampling window and the size of the second sampling window of each sampling phase can be adaptively set according to actual conditions, and this application does not impose any restrictions on this. Based on this, it can be understood that the size of the sampling window of each sampling phase in the first embodiment of this application is adjustable.

[0095] It can be understood that the sampling window obtained in step S323 can filter out the current sampling value when the lower power switches M4 , M6 , and M2 are turned on simultaneously for the corresponding sampling phase.

[0096] However, because the first and second sampling windows are not necessarily equal in size, the number of current sampling values ​​within the first sampling window and the number of current sampling values ​​within the second sampling window may differ in the sampling window screening results. This makes the sampling time points of the current sampling values ​​within the first and second sampling windows symmetrical about the time point of the first overflow point. This situation introduces loop delay in the subsequent calculation of the three-phase current values, resulting in increased sampling error.

[0097] Therefore, after step S323, the following steps may be further included:

[0098] Step S324: taking the time point of the first overflow point as the symmetric center, current sampling values ​​in symmetrical time regions are selected from the first sampling window and the second sampling window as valid current sampling values.

[0099] For example, in some cases, step S324 may include the following steps:

[0100] Step a: Take the shorter time period of the first sampling window and the second sampling window as the first time period, and intercept the longer time period of the first sampling window and the second sampling window according to the first time period to obtain the second time period. The second time period and the first time period are symmetrical about the time point of the first overflow point.

[0101] Step b: taking a sampling point in a time region where the first time period, the time point where the first overflow point is located, and the second time period as an effective current sampling value.

[0102] In this way, the sampling time point of the effective current sampling value in the first time period and the sampling time point of the effective current sampling value in the second time period can be symmetrical about the time point of the first overflow point, thereby avoiding the introduction of loop delay into the subsequent calculation of the three-phase current value and preventing the increase of sampling error.

[0103] It can be understood that the size of the second time period can be adaptively set according to actual conditions (such as filtering requirements for current sampling values, time consumption of filtering calculation, etc.), and this application does not impose any restrictions on this.

[0104] Of course, in other cases, step S324 may also include the following steps:

[0105] Step c: intercepting the time periods corresponding to the first sampling window and the second sampling window respectively to obtain a third time period and a fourth time period, wherein the third time period and the fourth time period are symmetrical about the time point of the first overflow point.

[0106] Step d: Filter out effective current sampling values ​​from a time region that is a combination of the third time period, the time point at which the first overflow point occurs, and the fourth time period.

[0107] In this way, the sampling time point of the effective current sampling value in the third time period and the sampling time point of the effective current sampling value in the fourth time period can be symmetrical about the time point of the first overflow point, thereby avoiding the introduction of loop delay into the subsequent calculation of the three-phase current value and preventing the increase of sampling error.

[0108] It can be understood that the sizes of the third time period and the fourth time period can be adaptively set according to actual conditions (such as filtering requirements for current sampling values, time consumption of filtering calculation, etc.), and this application does not impose any restrictions on this.

[0109] It can be understood that the effective current sampling values ​​of phases A, B, and C can all be screened using steps a to b above.

[0110] For example, Figures 2A to 2C As shown, the first period of phase A is expressed as Figure 2A L in 1A , the second period of phase A is expressed as Figure 2A L in 2A . L 1A With L 2A Symmetrical about the time point tp where the first overflow point is located. 1A , tp and L 2A The time zone L connected to phase A A . L A The current sampling value within is the effective current sampling value of phase A.

[0111] The first period of phase B is expressed as Figure 2B L in 1B , the second period of phase B is expressed as Figure 2B L in 2B . L 1B With L 2B Symmetric about tp. L 1B , tp and L 2B The time zone L connected to the B phase B . L B The current sampling value within is the effective current sampling value of phase B.

[0112] The first period of phase C is expressed as Figure 2C L in 1C , the second period of phase C is expressed as Figure 2C L in 2C . L 1C With L 2C Symmetric about tp. L 1C , tp and L 2C The time region L that forms phase C C . L C The current sampling value within is the effective current sampling value of phase C.

[0113] Of course, the above steps c to d may also be used to filter the effective current sampling values ​​for phases A, B, and C.

[0114] Of course, phase A, phase B, and phase C can also be a part of the sampling phases that use the above steps a to b to filter the effective current sampling values, and the other part of the sampling phases that use the above steps c to d to filter the effective current sampling values. This application does not limit this.

[0115] In the first embodiment, considering that the phase with the smallest time region among the three sampling phases has the shortest conduction time of the lower power switch, resulting in the fewest number of effective current sampling values, and the effective current sampling values ​​of this sampling phase are also more susceptible to fluctuations caused by the switching state of the power switch, resulting in large errors. Therefore, to further improve the accuracy of three-phase current sampling, step S324 may further include the following steps:

[0116] Step e: discard the current sampling value of the sampling phase with the smallest sampling window.

[0117] In this way, in subsequent processing, the current value of the removed sampling phase is reconstructed based on the effective current sampling values ​​of the two retained sampling phases using Kirchhoff's current law.

[0118] It can be understood that a, b, c, d and e are only used to distinguish different steps and do not limit the order of the steps.

[0119] In the first embodiment, the timer 20 sets a corresponding comparison value (ie, a loop calculation result) according to the torque output requirement of the three-phase motor 30 and the working condition of the three-phase motor 30 to control the three-phase inverter to provide the three-phase current required by the three-phase motor 30.

[0120] Therefore, in step S321 and step S322, the corresponding loop calculation results can be obtained according to the torque output requirements of the three-phase motor 30 and the working conditions of the three-phase motor 30. Based on the loop calculation results, the current sampling values ​​that meet the motor torque output requirements and the motor working conditions can be accurately sampled, and finally the three-phase current that meets the motor torque output requirements and the motor working conditions can be accurately calculated.

[0121] In the first embodiment, to prevent current sampling from affecting the loop calculation and comparison value update, the timer 20 can be configured to perform the loop calculation within the third switching period T3 in the time region between the end of the second sampling window and the second overflow point, and the comparison value is updated after the loop calculation is completed.

[0122] For example, see Figures 2A to 2C , the timer 20 can start the loop calculation at the time of the overflow point of the second switching period T2 to obtain the comparison value to be used in the third switching period T3, and then update the comparison value at the time of the second overflow point, so as to reserve enough time for the loop calculation.

[0123] In the first embodiment, the three-phase current calculation process of step S33 can be as follows:

[0124] Step S331: performing mean filtering calculation on the effective current sampling values ​​of the two sampling phases respectively to obtain filtered two-phase current values.

[0125] Step S332: Based on Kirchhoff's current law, the current value of another phase in the three-phase is calculated using the filtered two-phase current values.

[0126] To better understand the method of the first embodiment, the method of the first embodiment will be described below with examples.

[0127] For example, it is assumed that within a time period symmetrical to the time point at which the first overflow point is located, the currents of the sampling phases A, B, and C are uniformly sampled at 15 points respectively, thereby obtaining 15 current sampling values ​​A(1) to A(15), B(1) to B(15), and B(1) to B(15) with continuous sampling time. Among them, the 1st to 7th current sampling values ​​A(1) to A(7), B(1) to B(7), and B(1) to B(7) are obtained by sampling in sequence within the second switching cycle T2, the 8th current sampling values ​​A(8), B(8), and B(8) are obtained by sampling at the time point at which the first overflow point is located, and the 9th to 15th current sampling values ​​A(9) to A(15), B(9) to B(9), and B(9) to B(9) are obtained by sampling in sequence within the third switching cycle T3.

[0128] Since among the three sampling phases, the switching duty cycle of phase C in the second switching cycle T2 and the third switching cycle T3 is the largest, it means that the low-level period of phase C in the second switching cycle T2 and the third switching cycle T3 is the shortest, which will make the first sampling window located in the low-level period in T2 also the smallest, and the second sampling window located in the low-level period in T3 also the smallest. Therefore, the sampling window of phase C is the smallest, so the current sampling value of phase C can be discarded.

[0129] As for the current sampling value of phase A, since it can be determined based on the switching duty cycle of phase A at T2, the sampling time points of A(3) to A(7) are located in the low-level period before the time point of the first overflow point in T2, therefore, this low-level period can be used as the first sampling window.

[0130] According to the switching duty cycle of phase A at T3, it can be determined that the sampling time points of A(9) to A(12) are located within the low-level period of the third switching cycle T3. Therefore, this low-level period can be used as the second sampling window. Therefore, the sampling window composed of the first sampling window, the time point of the first overflow point, and the second sampling window can be used to filter out A(3) to A(7) and A(9) to A(12).

[0131] Since the sampling time points of A(4) to A(7) and the sampling time points of A(9) to A(12) are symmetrical about the time point of the first overflow point, and A(3) is a redundant current sampling value, the first sampling window is larger than the second sampling window. Therefore, the low-level period corresponding to the second sampling window is taken as the first period, and the low-level period corresponding to the first sampling window is intercepted to obtain a second period that is equal to the first period and symmetrical about the time point of the first overflow point. The time region synthesized by the second period, the time point of the first overflow point, and the first period can screen out the valid current sampling values ​​A(4) to A(12).

[0132] Then use A(4) to A(12) to perform the following mean filtering calculation:

[0133]

[0134] Wherein, A(j) represents the effective current sampling value of phase A, and j represents the sampling sequence numbers 4 to 12 of the effective current sampling value of phase A.

[0135] After calculation, the filtered A-phase current value Ia can be obtained.

[0136] Similarly, for the current sampling value of phase B, since it can be determined based on the switching duty cycle of phase B at T2, the sampling time points of B(1) to B(7) are all located in the low-level period before the time point of the first overflow point in T2, so this low-level period can be used as the first sampling window.

[0137] According to the switching duty cycle of phase B at T3, it can be determined that the sampling time points of B(9) to B(15) are all located within the low-level period in the third switching cycle T3, so this low-level period can be used as the second sampling window.

[0138] Since the sampling time points of B(1) to B(7) and the sampling time points of B(9) to B(15) are symmetrical about the time point of the first overflow point, B(1) to B(15) selected by the sampling window synthesized by the first sampling window, the time point of the first overflow point and the second sampling window are all effective current sampling values.

[0139] Therefore, use B(1) to B(15) to perform the following mean filtering calculation:

[0140]

[0141] Wherein, B(k) represents the effective current sampling value of phase B, and k represents the sampling sequence number 1 to 15 of the effective current sampling value of phase B.

[0142] After calculation, the filtered B-phase current value Ib can be obtained.

[0143] Finally, substitute Ia and Ib into formula I A +I B +I C =0, the C phase current value Ic can be calculated.

[0144] Example 2

[0145] It will be appreciated that in the first embodiment described above, the three-phase inverter 10 connected to the three-phase motor 30 is provided with three sampling resistors R1 to R3. Of course, in other embodiments, such as the second embodiment, the three-phase inverter 10 may also be provided with two sampling resistors. The two sampling resistors are respectively connected to two of the three phases A, B, and C of the three-phase motor 30. In this way, two of the three phases A, B, and C of the three-phase motor 30 serve as sampling phases.

[0146] In the second embodiment, the current sampling method for a three-phase motor is to define any three consecutive switching cycles of the timer 20 as the first switching cycle T1, the second switching cycle T2, and the third switching cycle T3. The underflow point of the second switching cycle T2 is defined as the first overflow point, and the underflow point of the third switching cycle T3 is defined as the second overflow point.

[0147] Since two of the three phases A, B, and C of the three-phase motor 30 are used as sampling phases in the second embodiment, correspondingly, in the second embodiment, step S31 obtains the current sampling values ​​of the two sampling phases of the three-phase motor 30. The specific current sampling process can be found in the first embodiment above and will not be repeated here. Similarly, step S32 of the second embodiment only requires screening the valid current sampling values ​​of the two sampling phases. The specific screening process can be found in the first embodiment above and will not be repeated here.

[0148] Furthermore, as described above, since step S32 of the second embodiment obtains the effective current sampling values ​​of two phases, the effective current sampling values ​​of these two phases can be directly used in step S33 to calculate the filtered three-phase current values. Therefore, when the three-phase inverter 10 is equipped with two sampling resistors, step e can be omitted in the current sampling method of the second embodiment.

[0149] Example 3

[0150] It will be appreciated that in the first embodiment, the three-phase inverter 10 connected to the three-phase motor 30 employs a low-side current sampling method, i.e., the three lower power switches M4, M6, and M2 of the three-phase inverter 10 are grounded via corresponding sampling resistors R1, R2, and R3, respectively. Of course, in other embodiments, such as the third embodiment, the three-phase inverter 10 may also employ a high-side current sampling method, i.e., sampling resistors are provided on the lines used by each upper power switch to access DC power, the three upper power switches of the three-phase inverter 10 are connected to DC power via corresponding sampling resistors, and the three lower power switches are grounded. In this manner, phases A, B, and C of the three-phase motor 30 are all sampling phases.

[0151] Correspondingly, in Example 3, when the timer 20 controls the three lower power switches of the three-phase inverter 10 to be turned off at the same time and the three upper power switches of the three-phase inverter 10 to be turned on at the same time (including the time point where the overflow point is located), the three-phase current of the three-phase motor 30 corresponds one-to-one to the current flowing through the three sampling resistors, so the current flowing through the sampling resistors is sampled at this time.

[0152] Since current sampling is performed when the three upper power switches of the three-phase inverter 10 are simultaneously turned on in the third embodiment, correspondingly, in the third embodiment, the current sampling method for the three-phase motor is to define any three consecutive switching cycles of the timer 20 as the first switching cycle T1, the second switching cycle T2, and the third switching cycle T3. The overflow point of the second switching cycle T2 is defined as the first overflow point, and the overflow point of the third switching cycle T3 is defined as the second overflow point.

[0153] Correspondingly, in step S31 of the third embodiment, the time period D symmetrical to the time point of the first overflow point is within the second switching cycle T2. The specific current sampling process can be found in the above-mentioned first embodiment and will not be repeated here. The sampling time points corresponding to the current sampling values ​​are all within the second switching cycle T2.

[0154] Since the sampling time points corresponding to the current sampling values ​​in step S31 are all within the second switching period T2, step S32 in embodiment 3 may include the following steps:

[0155] Step i: Based on the loop calculation result of each sampling phase in the first switching period T1 (i.e., the comparison value used by the timer 20 in the second switching period T2), the switching duty cycle of the second switching period T2 is obtained, thereby obtaining a time-continuous sampling window based on the switching duty cycle of the second switching period T2.

[0156] The sampling window of each sampling phase is located within the second switching cycle T2, specifically, is located in the high level period of the second switching cycle T2, and includes the time point of the first overflow point.

[0157] It can be understood that the sampling window can filter out the current sampling value when the three upper power switches are turned on at the same time for the corresponding sampling phase.

[0158] It can be understood that the time period before the first overflow point in the sampling window can be used as the first sampling window, and the time period after the first overflow point in the sampling window can be used as the second sampling window.

[0159] It is understandable that because the first sampling window and the second sampling window are not necessarily symmetrical about the time point of the first overflow point, the sampling window screening results may result in different numbers of current sampling values ​​in the first sampling window and the second sampling window, making the sampling time points of the current sampling values ​​in the sampling windows not symmetrical about the time point of the first overflow point. This situation will introduce loop delay in the subsequent calculation of the three-phase current values, resulting in increased sampling error.

[0160] Therefore, after step i, the following steps may also be included:

[0161] Step ii: Taking the time point of the first overflow point as the symmetric center, current sampling values ​​within symmetrical time regions are selected from the first sampling window and the second sampling window as valid current sampling values.

[0162] The process of step ii may be specifically referred to step S324 in the above embodiment 1, which will not be described in detail here.

[0163] The process of step S33 can also refer to step S33 in the above embodiment 1, and will not be repeated here.

[0164] Furthermore, because the sampling window in the third embodiment is within the second switching cycle T2, accordingly, in the third embodiment, the timer 20 performs loop calculations within the third switching cycle T3 in the time period between the end of the second sampling window and the underflow point of the second switching cycle T2, and updates the comparison value after the loop calculations are completed. For example, the timer 20 begins the loop calculation at the time of the underflow point of the second switching cycle T2, obtains the comparison value to be used in the third switching cycle T3, and then updates the comparison value at the time of the second overflow point.

[0165] Example 4

[0166] It will be appreciated that in the third embodiment described above, the three-phase inverter 10 connected to the three-phase motor 30 is provided with three sampling resistors. Of course, in other embodiments, such as the fourth embodiment, the three-phase inverter 10 may also be provided with two sampling resistors. The two sampling resistors are respectively connected to two of the three phases A, B, and C of the three-phase motor 30. In this way, two of the three phases A, B, and C of the three-phase motor 30 serve as sampling phases.

[0167] In the fourth embodiment, a current sampling method for a three-phase motor is performed by sequentially defining any three consecutive switching cycles of timer 20 as a first switching cycle T1, a second switching cycle T2, and a third switching cycle T3. The overflow point of the second switching cycle T2 is defined as a first overflow point, and the overflow point of the third switching cycle T3 is defined as a second overflow point.

[0168] Since two of the three phases A, B, and C of the three-phase motor 30 are used as sampling phases in the fourth embodiment, correspondingly, in the fourth embodiment, step S31 obtains the current sampling values ​​of the two sampling phases of the three-phase motor 30. The specific current sampling process can be found in the third embodiment above and will not be repeated here. Similarly, step S32 of the fourth embodiment only requires screening the valid current sampling values ​​of the two sampling phases. The specific screening process can be found in the third embodiment above and will not be repeated here.

[0169] In addition, as described above, since the effective current sampling values ​​of two phases are obtained in step S32 of the fourth embodiment, the effective current sampling values ​​of the two phases can be directly used in step S33 to calculate the filtered three-phase current values.

[0170] Example 5

[0171] It is understood that in the first embodiment, the three-phase inverter 10 connected to the three-phase motor 30 adopts a low-side current sampling method. Of course, in other embodiments, such as the fifth embodiment, the three-phase inverter 10 may also adopt a built-in current sampling method, that is, three sampling resistors are respectively provided on the A, B, and C phase lines of the three-phase motor 30, and the three bridge arms of the three-phase inverter 10 are connected to the three-phase motor 30 through the sampling resistors. The three upper power switches all receive DC power, and the three lower power switches are all grounded. In this way, the A, B, and C phases of the three-phase motor 30 are all sampling phases.

[0172] In the fifth embodiment, the current sampling method for a three-phase motor is to define any three consecutive switching cycles of the timer 20 as the first switching cycle T1, the second switching cycle T2, and the third switching cycle T3. Furthermore, the overflow point or underflow point of the second switching cycle T2 can be defined as the first overflow point, and the overflow point or underflow point of the third switching cycle T3 can be defined as the second overflow point.

[0173] When the fifth embodiment defines the underflow point of the second switching cycle T2 as the first overflow point and the underflow point of the third switching cycle T3 as the second overflow point, the current sampling process of the three-phase motor can refer to the first embodiment and will not be repeated here.

[0174] When the overflow point of the second switching cycle T2 is defined as the first overflow point and the overflow point of the third switching cycle T3 is defined as the second overflow point in the fifth embodiment, the current sampling process of the three-phase motor can refer to the third embodiment and will not be repeated here.

[0175] Example 6

[0176] It will be appreciated that in the fifth embodiment described above, the three-phase inverter 10 connected to the three-phase motor 30 is provided with three sampling resistors. Of course, in other embodiments, such as the sixth embodiment, the three-phase inverter 10 may also be provided with two sampling resistors. The two sampling resistors are respectively connected to two of the three phases A, B, and C of the three-phase motor 30. In this way, two of the three phases A, B, and C of the three-phase motor 30 serve as sampling phases.

[0177] In the sixth embodiment, the current sampling method for a three-phase motor defines any three consecutive switching cycles of the timer 20 as the first switching cycle T1, the second switching cycle T2, and the third switching cycle T3. Furthermore, the overflow point or underflow point of the second switching cycle T2 can be defined as the first overflow point, and the overflow point or underflow point of the third switching cycle T3 can be defined as the second overflow point.

[0178] When the sixth embodiment defines the underflow point of the second switching cycle T2 as the first overflow point and the underflow point of the third switching cycle T3 as the second overflow point, the current sampling process of the three-phase motor can refer to the second embodiment and will not be repeated here.

[0179] When the overflow point of the second switching cycle T2 is defined as the first overflow point and the overflow point of the third switching cycle T3 is defined as the second overflow point in the sixth embodiment, the current sampling process of the three-phase motor can refer to the fourth embodiment and will not be repeated here.

[0180] In summary, the current sampling methods of the three-phase motor in Examples 1 to 6 of the present application can all realize multi-point sampling and filtering processing of the three-phase current of the three-phase motor. Without introducing additional loop delay, they can significantly reduce the current sampling noise and obtain more accurate three-phase current values, thereby effectively improving the control accuracy of the three-phase motor.

[0181] It should be noted that, for the sake of simplicity of description, the aforementioned method embodiments are all expressed as a series of action combinations. However, those skilled in the art should be aware that this application is not limited to the described order of actions, because according to this application, certain steps can be performed in other orders or simultaneously.

[0182] Please refer to Figure 5 The embodiment of the present application further provides a power device 100. The power device 100 includes a three-phase motor 30 and a processor 40, and the processor 40 is connected to the three-phase motor 30.

[0183] It is understood that the power device 100 can be any device equipped with a three-phase motor 30 and a processor 40, such as a robot, a vehicle, a household appliance, etc. This application does not impose any limitation on this.

[0184] The processor 40 can be a central processing unit (CPU), or other general-purpose processors 40, digital signal processors 40 (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0185] The processor 40 can run program instructions to execute part or all of the method steps of at least one of the schemes in Examples 1 to 6 of the present application, and thus can accurately control the output of the three-phase motor 30 based on the filtered three-phase current value.

[0186] It will be understood that the program instructions for executing the above scheme may be stored in a memory. The memory may be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto.

[0187] In some embodiments, the processor 40 may include a memory, a three-phase inverter 10, and a timer 20. It will be appreciated that the method steps executed by the processor 40 are adapted to the circuit topology of the three-phase inverter 10. For example, when the three-phase inverter 10 adopts the circuit topology of the first embodiment, the processor 40 executes some or all of the method steps of the first embodiment of the present application. When the three-phase inverter 10 adopts the circuit topology of the second embodiment, the processor 40 executes some or all of the method steps of the second embodiment of the present application.

[0188] Of course, in some other embodiments, the memory, the three-phase inverter 10 and the timer 20 may also exist independently and be connected to the processor 40 via a bus.

[0189] Of course, in some other embodiments, the memory, the three-phase inverter 10, the timer 20, and the processor 40 may also be integrated together, and this application does not impose any limitation on this.

[0190] The power device 100 of the embodiment of the present application can implement filtering processing on the sampled current, effectively reducing the impact of noise interference on the sampled current, and thus having higher three-phase motor control accuracy.

[0191] The present application also provides a computer-readable storage medium having program instructions stored therein. When executed on a computing device, the program instructions cause the computing device to execute the current sampling method for a three-phase motor provided by at least one of the first to sixth embodiments above, thereby obtaining accurate three-phase current values ​​and improving the control accuracy of the three-phase motor.

[0192] The present application also provides a current sampling device for a three-phase motor. The current sampling device for a three-phase motor may include a current sampling value acquisition module, a screening module, and a calculation module connected in sequence.

[0193] The current sampling value acquisition module is used to acquire the current sampling value of each sampling phase current in the three-phase motor. The current sampling value includes the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value at the first overflow point.

[0194] The screening module is used to screen out valid current sampling values ​​from the current sampling values ​​in the first sampling window, the current sampling values ​​in the second sampling window, and the current sampling values ​​at the first overflow point.

[0195] The calculation module is used to calculate the filtered three-phase current value of the motor according to the effective current sampling value.

[0196] It can be understood that the division of the various modules in the above-mentioned current sampling device for the three-phase motor is only for illustration. In other embodiments, the current sampling device for the three-phase motor can be divided into different modules as needed to complete all or part of the functions of the above-mentioned current sampling device for the three-phase motor.

[0197] The specific implementation of each module in the embodiment of the present application can also refer to the corresponding description of the current sampling method of the three-phase motor provided by at least one of the above-mentioned embodiments one to six, and will not be described in detail here.

[0198] The current sampling device of the three-phase motor of the embodiment of the present application can realize multi-point sampling and filtering processing of the three-phase current of the three-phase motor, obtain accurate three-phase current values, and thus improve the control accuracy of the three-phase motor.

[0199] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A current sampling method for a three-phase motor, characterized in that: include: Acquire a current sampling value of each sampling phase current in the three-phase motor, wherein the current sampling value includes a current sampling value within a first sampling window, a current sampling value within a second sampling window, and a current sampling value at a first overflow point; Filter out a valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value of the first overflow point; Calculating filtered three-phase current values ​​of the motor according to the effective current sampling values; The first sampling window and the second sampling window are respectively located in two consecutive switching cycles, and the first sampling window, the time point of the first overflow point and the second sampling window are sequentially connected to form a time-continuous sampling window.

2. The current sampling method according to claim 1, wherein: The step of selecting a valid current sampling value from the current sampling values ​​in the first sampling window, the current sampling values ​​in the second sampling window, and the current sampling values ​​at the first overflow point comprises the following steps: Obtaining a switching duty cycle of a second switching cycle according to a loop calculation result of each sampling phase in the first switching cycle, thereby obtaining the first sampling window according to the switching duty cycle of the second switching cycle, wherein the first sampling window is located within the second switching cycle; Obtaining a switching duty cycle of a third switching cycle according to a loop calculation result of each sampling phase in the second switching cycle, thereby obtaining a second sampling window according to the switching duty cycle of the third switching cycle, wherein the second sampling window is located within the third switching cycle; Taking the time point of the first overflow point as the symmetric center, the current sampling values ​​in symmetrical time regions are selected from the first sampling window and the second sampling window as valid current sampling values.

3. The current sampling method according to claim 2, wherein: The step of selecting the current sampling values ​​in symmetrical time regions from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the effective current sampling values ​​includes the following steps: Taking a shorter time period corresponding to the first sampling window and the second sampling window as a first time period, and intercepting a longer time period corresponding to the first sampling window and the second sampling window according to the first time period to obtain a second time period, where the second time period is symmetrical to the first time period about the time point of the first overflow point; The sampling points in the time region formed by combining the first time period, the time point at which the first overflow point occurs, and the second time period are used as effective current sampling values.

4. The current sampling method according to claim 2, wherein: The step of selecting the current sampling values ​​in symmetrical time regions from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the effective current sampling values ​​includes the following steps: intercepting time periods corresponding to the first sampling window and the second sampling window respectively to obtain a third time period and a fourth time period, wherein the third time period and the fourth time period are symmetrical about a time point where the first overflow point is located; The effective current sampling value is screened out from the time region formed by combining the third time period, the time point at which the first overflow point is located, and the fourth time period.

5. The current sampling method according to claim 2, wherein: The loop calculation result is obtained according to the torque output requirement of the motor and the working condition of the motor.

6. The current sampling method according to claim 2, wherein: The time region of the loop calculation within the third switching cycle is the time region from the end of the second sampling window to the second overflow point, the second overflow point is separated from the first overflow point by one switching cycle, and the time point of the second overflow point is later than the time point of the first overflow point.

7. A power equipment, characterized in that: The power device includes a three-phase motor and a processor, wherein the processor is connected to the three-phase motor and configured to: Obtaining a current sampling value of each sampling phase current in the three-phase motor, wherein the current sampling value includes a current sampling value within a first sampling window, a current sampling value within a second sampling window, and a current sampling value at a first overflow point; Filter out a valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value of the first overflow point; Calculating filtered three-phase current values ​​of the motor according to the effective current sampling values; The first sampling window and the second sampling window are respectively located in two consecutive switching cycles, and the first sampling window, the time point of the first overflow point and the second sampling window are sequentially connected to form a time-continuous sampling window.

8. The power equipment according to claim 7, characterized in that The processor is configured to filter out a valid current sampling value from the current sampling value in the first sampling window, the current sampling value in the second sampling window, and the current sampling value at the first overflow point, specifically: The processor is configured to obtain a switching duty cycle of a second switching cycle based on a loop calculation result of each sampling phase in the first switching cycle, thereby obtaining the first sampling window based on the switching duty cycle of the second switching cycle, wherein the first sampling window is located within the second switching cycle; The processor is configured to obtain a switching duty cycle of a third switching cycle based on a loop calculation result of each sampling phase in the second switching cycle, thereby obtaining a second sampling window based on the switching duty cycle of the third switching cycle, wherein the second sampling window is located within the third switching cycle; The processor is further configured to filter the current sampling values ​​in a symmetrical time region from the first sampling window and the second sampling window with the time point of the first overflow point as a symmetrical center as valid current sampling values.

9. The power equipment according to claim 8, characterized in that The processor is further configured to filter the current sampling values ​​within a symmetrical time region from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the valid current sampling values, specifically: The processor is configured to use a shorter time period corresponding to the first sampling window and the second sampling window as a first time period, and intercept a longer time period corresponding to the first sampling window and the second sampling window according to the first time period to obtain a second time period, wherein the second time period is symmetrical to the first time period about a time point where the first overflow point is located; The processor is configured to take a sampling point within the time region formed by combining the first time period, the time point at which the first overflow point occurs, and the second time period as an effective current sampling value.

10. The power equipment according to claim 8, characterized in that The processor is further configured to filter the current sampling values ​​within a symmetrical time region from the first sampling window and the second sampling window with the time point of the first overflow point as the symmetrical center as the valid current sampling values, specifically: The processor is configured to intercept time periods corresponding to the first sampling window and the second sampling window respectively to obtain a third time period and a fourth time period, wherein the third time period and the fourth time period are symmetrical about a time point where the first overflow point is located; The processor is configured to filter out the effective current sampling value from the time region formed by combining the third time period, the time point at which the first overflow point occurs, and the fourth time period.

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