A current sampling method, device, motor and computer readable storage medium

Abstract

The present invention discloses a current sampling method, device, motor and computer-readable storage medium. The method includes being applied to a motor, wherein the operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor, and the method includes: determining whether the current synthetic vector of the motor is in an observable area or an unobservable area; if the current synthetic vector of the motor is in an unobservable area, adjusting the duty cycle of the three-phase voltage of the motor according to the load state of the motor; performing phase shifting on the adjusted three-phase voltage, and performing current sampling according to the three-phase voltage waveform after the phase shifting. Through the present invention, whether the motor is running under low load or high load, the accuracy of the current sampling result can be guaranteed, thereby improving the accuracy of motor control.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a current sampling method, device, motor and computer-readable storage medium. Background Art

[0002] Permanent magnet synchronous motor is a motor with simple structure, fast speed regulation and low cost, which is widely used in the field of household appliances. In practical applications, the operation of the motor is controlled by controlling the synthetic vector of the three-phase current. During the control process, the current of the motor needs to be sampled. At present, the motor current is generally obtained by the single resistor sampling method of the motor phase current. However, when the synthetic vector is in the unobservable area, the bus current of the drive system needs to be reconstructed for three phases. When the phase shifting method is currently used, when the motor load is small, the duty cycle of each phase is also low, the current distortion is more serious, and the current oscillation in the positive and negative directions will appear in a short time during the phase shifting; when the motor load is large, the duty cycle of each phase is also high, and the phase shifting space is relatively small, which will cause the problem of exceeding the adjustment range during the phase shifting.

[0003] In summary, when the motor is running at low load, the current waveform will oscillate, and when it is running at high load, there will be an over-modulation problem. Therefore, no matter whether the motor is running at low load or high load, there will be an inaccurate current sampling result when sampling the current in the unobservable area.

[0004] With respect to the problem in the prior art that when the synthetic vector of the motor is located in an unobservable area, the current sampling result is inaccurate, no effective solution has been proposed yet. Summary of the invention

[0005] The embodiments of the present invention provide a current sampling method, a device, a motor and a computer-readable storage medium to solve the problem in the prior art that when the synthetic vector of the motor is located in an unobservable area, the current sampling result is inaccurate.

[0006] In order to solve the above technical problems, the present invention provides a current sampling method, which is applied to a motor, wherein the operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor, and the method comprises:

[0007] Determine whether the current resultant vector of the motor is in the observable region or the unobservable region;

[0008] If the current synthetic vector of the motor is in an unobservable region, adjusting the duty cycle of the three-phase voltage of the motor according to the load state of the motor;

[0009] The adjusted three-phase voltage is phase-shifted, and current sampling is performed according to the three-phase voltage waveform after the phase shift.

[0010] Further, determining whether the current synthetic vector of the motor is located in the observable region or the unobservable region includes:

[0011] Calculate the time parameter according to the magnitude and angle of the synthetic vector;

[0012] It is determined whether the current synthetic vector of the motor is in the observable region or the unobservable region according to the numerical range of the time parameter.

[0013] Further, calculating the time parameter according to the magnitude and angle of the synthetic vector includes:

[0014] Decomposing the resultant vector into a first voltage vector and a second voltage vector according to the magnitude and angle of the resultant vector;

[0015] respectively calculating the action durations of the first voltage vector and the second voltage vector;

[0016] The time parameter is calculated according to the action durations of the first voltage vector and the second voltage vector.

[0017] Further, when the time parameter is calculated according to the action duration of the first voltage vector and the second voltage vector, it is implemented according to the following formula:

[0018] The time parameter=the action duration of the first voltage vector+the action duration of the second voltage vector×cos60°; wherein the angle of the second voltage vector is greater than the angle of the first voltage vector.

[0019] Further, determining whether the current synthetic vector of the motor is located in the observable region or the unobservable region according to the numerical range of the time parameter includes:

[0020] Determine whether the time parameter satisfies a condition greater than or equal to the first threshold and less than or equal to a second threshold;

[0021] If yes, it is determined that the current resultant vector of the motor is in the observable region;

[0022] If not, it is determined that the current resultant vector of the motor is in the unobservable region.

[0023] Further, adjusting the duty cycle of the three-phase voltage of the motor according to the load state of the motor includes:

[0024] Determine the current load state of the motor;

[0025] If the motor is currently in a low-load state, the duty cycle of the three-phase voltage is controlled to increase by a preset value simultaneously;

[0026] If the motor is currently in a high load state, the duty cycle of the three-phase voltage is controlled to be reduced by a preset value.

[0027] Furthermore, determining the current load state of the motor includes:

[0028] If the time parameter of the synthetic vector is less than a first threshold value, it is determined that the motor is currently in a low-load state;

[0029] If the time parameter of the resultant vector is greater than a second threshold, it is determined that the motor is currently in a high load state.

[0030] Furthermore, the adjusted three-phase voltage is phase-shifted, including:

[0031] Determine a maximum phase voltage, an intermediate phase voltage and a minimum phase voltage; wherein the maximum phase voltage is the phase voltage with the largest duty cycle among the three-phase voltages, the intermediate phase voltage is the phase voltage with an intermediate duty cycle among the three-phase voltages, and the minimum phase voltage is the phase voltage with the smallest duty cycle among the three-phase voltages;

[0032] The waveform of the intermediate phase voltage of the motor is controlled to move for a first preset time length, and the waveform of the maximum phase voltage of the motor is controlled to move for a second preset time length.

[0033] Further, when controlling the waveform of the intermediate phase voltage of the motor to move for a first preset time length, it is achieved according to the following formula:

[0034] The first preset duration=(Td-(Tb-Ta));

[0035] Wherein, the Td is the minimum sampling duration, the Tb is the duty cycle of the intermediate phase voltage, and the Ta is the duty cycle of the minimum phase voltage.

[0036] Further, when the waveform of the maximum phase voltage of the motor is controlled to move for a second preset time length, it is achieved according to the following formula:

[0037] The second preset time length=(Td-(Tc-Tb));

[0038] Wherein, the Td is the minimum sampling duration, the Tb is the duty cycle of the intermediate phase voltage, and the Tc is the duty cycle of the maximum phase voltage.

[0039] The present invention also provides a current sampling device, which is applied to a motor, wherein the operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor, and the device comprises:

[0040] A determination module, used to determine whether the region where the current synthetic vector of the motor is located is an observable region or an unobservable region;

[0041] An adjustment module, used for adjusting the duty cycle of the three-phase voltage of the motor according to the load state of the motor when the current synthetic vector of the motor is in an unobservable area;

[0042] The phase shift module is used to shift the phase of the adjusted three-phase voltage and perform current sampling according to the three-phase voltage waveform after the phase shift.

[0043] The present invention also provides a motor, comprising the above-mentioned current sampling device.

[0044] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the current sampling method is implemented.

[0045] By applying the technical solution of the present invention, when the current synthetic vector of the motor is in the unobservable area, the duty cycle of the three-phase voltage of the motor is adjusted according to the load state of the motor; the adjusted three-phase voltage is phase-shifted, and current sampling is performed based on the three-phase voltage waveform after the phase shift. Regardless of whether the motor is running under low load or high load, the accuracy of the current sampling result can be guaranteed, thereby improving the accuracy of motor control. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is an internal circuit diagram of a motor according to an embodiment of the present invention;

[0047] Figure 2 is a flow chart of a current sampling method according to an embodiment of the present invention;

[0048] Figure 3 A voltage vector sector diagram according to an embodiment of the present invention;

[0049] Figure 4 is a waveform diagram of the three-phase voltage at each stage under a low load state according to an embodiment of the present invention; wherein, Figure 4 (a) is a waveform diagram of three-phase voltage under low load condition according to an embodiment of the present invention; Figure 4 (b) is a waveform diagram of the three-phase voltage after the duty cycle is increased according to an embodiment of the present invention; Figure 4 (c) is a final waveform diagram of each phase voltage under low load condition according to an embodiment of the present invention;

[0050] Figure 5 is a waveform diagram of the three-phase voltage at each stage under a high load state according to an embodiment of the present invention; wherein, Figure 5 (a) is a waveform diagram of three-phase voltage under high load condition according to an embodiment of the present invention; Figure 5 (b) is a waveform diagram of the three-phase voltage after the duty cycle is reduced according to an embodiment of the present invention; Figure 5 (c) is a final waveform diagram of each phase voltage under high load condition according to an embodiment of the present invention;

[0051] Figure 6 A schematic diagram of dividing a non-zero region and a zero region of a waveform according to an embodiment of the present invention;

[0052] Figure 7 is a flow chart of a current sampling method according to another embodiment of the present invention;

[0053] Figure 8 is a structural diagram of a current sampling device according to an embodiment of the present invention;

[0054] Fig. 9 FIG. 4 is a structural diagram of a current sampling device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0057] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0058] It should be understood that, although the terms first, second, etc. may be used to describe voltage vectors in embodiments of the present invention, these voltage vectors should not be limited to these terms. These terms are only used to distinguish different voltage vectors. For example, without departing from the scope of embodiments of the present invention, the first voltage vector may also be referred to as the second voltage vector, and similarly, the second voltage vector may also be referred to as the first voltage vector.

[0059] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0060] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0061] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0062] Example 1

[0063] This embodiment provides a current sampling method, which is applied to a motor. The operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor. In this embodiment, the motor is a permanent magnet synchronous motor. Figure 1 is an internal circuit diagram of a motor according to an embodiment of the present invention, as shown in Figure 1 As shown, the piezoelectric motor includes a DC voltage source VDC, an inverter module 1 and a winding 2, the inverter module 1 includes a first inverter bridge, a second inverter bridge and three inverter bridges, wherein the first inverter bridge includes a first upper bridge arm A_G1 and a first lower bridge arm A_G2, the line led out between the first upper bridge arm A_G1 and the first lower bridge arm A_G2 is connected to the first phase of the winding 2, the second inverter bridge includes a second upper bridge arm B_G1 and a second lower bridge arm B_G2, the line led out between the second upper bridge arm B_G1 and the second lower bridge arm B_G2 is connected to the second phase of the winding 2, the third inverter bridge includes a third upper bridge arm C_G1 and a third lower bridge arm C_G2, the line led out between the third upper bridge arm C_G1 and the third lower bridge arm C_G2 is connected to the third phase of the winding 2.

[0064] The motor further includes a sampling resistor R, which is arranged between the negative terminal of the DC voltage source VDC and the inverter module 1 .

[0065] Figure 2 is a flow chart of a current sampling method according to an embodiment of the present invention. Figure 2 As shown, the method includes:

[0066] S01, determining whether the current synthetic vector of the motor is in the observable region or the unobservable region.

[0067] Figure 3 is a voltage vector sector diagram according to an embodiment of the present invention, such as Figure 3 As shown, the first non-zero vector V1, the second non-zero vector V2, the third non-zero vector V3, the fourth non-zero vector V4, the fifth non-zero vector V5, and the sixth non-zero vector V6 are six non-zero vectors, and any two adjacent non-zero vectors are separated by 60°. The above six non-zero vectors divide the plane into six sectors. In the figure, the area between the two parallel dotted lines is the unobservable area, and the remaining area is the observable area. When the duty cycles of two of the three-phase voltages are similar, the reserved sampling time is insufficient, so it is necessary to move one or two of the phases to reserve enough sampling time.

[0068] S02: If the current synthetic vector of the motor is in an unobservable region, the duty cycle of the three-phase voltage of the motor is adjusted according to the load state of the motor.

[0069] The existing current sampling method fixes the widest pulse duty cycle and then shifts the middle pulse backward to obtain the second sampling point. Based on this processing, the narrowest pulse is shifted backward to obtain the first sampling point. In this way, two-phase currents are obtained by adjusting the sampling each time, and the third-phase current is obtained by calculation.

[0070] If the current synthetic vector of the motor is in the unobservable area, the current sampling result will be inaccurate regardless of whether the motor is in a low load state or a high load state. In order to solve this problem, it is necessary to adjust the duty cycle of the three-phase voltage of the motor according to the load state of the motor, that is, to adopt different duty cycle adjustment strategies for low load state and high load state respectively to ensure the accuracy of the current sampling result.

[0071] S03, phase-shifting the adjusted three-phase voltage, and sampling current according to the phase-shifted three-phase voltage waveform.

[0072] The current sampling method of this embodiment adjusts the duty cycle of the three-phase voltage of the motor according to the load state of the motor when the current synthetic vector of the motor is in the unobservable area; the adjusted three-phase voltage is phase-shifted, and current sampling is performed based on the three-phase voltage waveform after the phase shift. Regardless of whether the motor is running under low load or high load, the accuracy of the current sampling result can be guaranteed, thereby improving the accuracy of motor control.

[0073] Example 2

[0074] This embodiment provides another current sampling method. In order to accurately determine whether the current synthetic vector of the motor is in the observable area or the unobservable area, the above step S101 specifically includes:

[0075] The time parameter is calculated according to the size and angle of the synthetic vector; and the current synthetic vector of the motor is determined to be in the observable area or the unobservable area according to the numerical range of the time parameter. Specifically, the time parameter is calculated according to the size and angle of the synthetic vector, including: decomposing the synthetic vector into a first voltage vector and a second voltage vector according to the size and angle of the synthetic vector; respectively calculating the action duration of the first voltage vector and the second voltage vector; and calculating the above time parameter according to the action duration of the first voltage vector and the second voltage vector. Wherein, when calculating the above time parameter according to the action duration of the first voltage vector and the second voltage vector, it is implemented according to the following formula: time parameter = action duration of the first voltage vector + action duration of the second voltage vector × cos60°; wherein, the angle of the second voltage vector is greater than the angle of the first voltage vector. Determining whether the current synthetic vector of the motor is in the observable area or the unobservable area according to the numerical range of the time parameter includes: judging whether the time parameter satisfies greater than or equal to the first threshold value and less than or equal to the second threshold value; if yes, determining that the current synthetic vector of the motor is in the observable area; if not, determining that the current synthetic vector of the motor is in the unobservable area.

[0076] The resultant vector is located at Figure 3 Taking the first sector in as an example, the vector is decomposed into the fourth non-zero vector V4 and the sixth non-zero vector V6 adjacent to it. According to the size of the resultant vector, the duration T4 of the first voltage vector decomposed in the direction of the fourth non-zero vector V4 and the duration T6 of the second voltage vector decomposed in the direction of the sixth non-zero vector V6 are determined. When T4+T6*cos60<the first threshold Tmin, it is determined that the resultant vector is located in the unobservable area and is in a low load state; when the first threshold Tmin≤T4+T6*cos60≤the second threshold Tmax, it is determined that the resultant vector is located in the observable area. When T4+T6*cos60>the second threshold Tmax, it is determined that the resultant vector is located in the unobservable area and is in a high load state.

[0077] When the motor is in a low-load state, the duty cycle of each phase voltage is small and the current distortion is serious. If the three-phase voltage waveform is directly shifted, current oscillations in the positive and negative directions will appear in a short period of time; when the motor is in a high-load state, the duty cycle of each phase is also high, and the phase shift space is relatively small. Directly shifting the phase of the three-phase voltage waveform will cause it to exceed the adjustment range. It can be seen that different duty cycle adjustment strategies are required for different load states. Therefore, the duty cycle of the three-phase voltage of the motor is adjusted according to the load state of the motor, specifically including: judging the current load state of the motor; if the motor is currently in a low-load state, the duty cycle of the three-phase voltage is controlled to increase by a preset value at the same time, and after the duty cycle increases, the phase is shifted to avoid current oscillations; if the motor is currently in a high-load state, the duty cycle of the three-phase voltage is controlled to decrease by a preset value at the same time, so that the phase shift adjustment range can be widened to avoid the problem of exceeding the adjustment range after the three-phase voltage waveform is phase shifted.

[0078] According to the numerical range of the time parameter mentioned above, it is possible to determine not only whether the synthetic vector is in the observable area or the unobservable area, but also whether the motor is currently in a low load state or a high load state. Specifically, the current load state of the motor is determined, including: if the time parameter of the synthetic vector is less than a first threshold value, then it is determined that the motor is currently in a low load state, that is, the synthetic vector is in a low load unobservable area; if the time parameter of the synthetic vector is greater than a second threshold value, then it is determined that the motor is currently in a high load state, that is, the synthetic vector is in a high load unobservable area.

[0079] After the duty cycle of the three-phase voltage is adjusted through the above steps, in order to realize current sampling, the adjusted three-phase voltage needs to be phase-shifted, specifically including: determining the maximum phase voltage C, the middle phase voltage B and the minimum phase voltage A; wherein the maximum phase voltage C is the phase voltage with the largest duty cycle among the three-phase voltages, the middle phase voltage B is the phase voltage with the middle duty cycle among the three-phase voltages, and the minimum phase voltage A is the phase voltage with the smallest duty cycle among the three-phase voltages; controlling the waveform of the middle phase voltage B of the motor to move for a first preset time length, and controlling the waveform of the maximum phase voltage C of the motor to move for a second preset time length; when controlling the waveform of the middle phase voltage B of the motor to move for the first preset time length, it is realized according to the following formula: first preset time length = (Td-(Tb-Ta)); wherein Td is the minimum sampling time length, Tb is the duty cycle of the middle phase voltage B, and Ta is the duty cycle of the minimum phase voltage A. When the waveform of the maximum phase voltage C of the motor is controlled to move the second preset time length, it is implemented according to the following formula: second preset time length = (Td-(Tc-Tb)); wherein Td is the minimum sampling time length, Tb is the duty cycle of the intermediate phase voltage B, and Tc is the duty cycle of the maximum phase voltage C.

[0080] Figure 4is a waveform diagram of the three-phase voltage at each stage under a low-load state according to an embodiment of the present invention. In a specific implementation, after determining that the motor is in a low-load state, the action time Ta (i.e., the duty cycle Ta of the minimum phase voltage A), Tb (i.e., the duty cycle of the middle phase voltage B), and Tc (i.e., the duty cycle of the maximum phase voltage C) of each phase high level are calculated. Figure 4 (a) is a waveform diagram of the three-phase voltage under low load condition according to an embodiment of the present invention. Figure 4 As shown in (a), at this time, Ta, Tb, and Tc are arranged from small to large, and Ta, Tb, and Tc are controlled to increase by a preset value Tx1. Figure 4 (b) is a waveform diagram of the three-phase voltage after the duty cycle is increased according to an embodiment of the present invention, the minimum sampling time is Td, the phase shift time required for the waveform of the intermediate phase voltage B is (Td-(Tb-Ta)), and the phase shift time required for the waveform of the maximum phase voltage C is (Td-(Tc-Tb)), Figure 4 (c) is the final waveform diagram of the voltage of each phase under the low load state according to an embodiment of the present invention. At this time, the action interval of each switch tube is relatively long, and the reserved sampling time is sufficient, so that the sampled value is close to the actual current value.

[0081] Figure 5 is a waveform diagram of the three-phase voltage at each stage under a high load state according to an embodiment of the present invention. In a specific implementation, after determining that the motor is in a high load state, the action time Ta (i.e., the duty cycle Ta of the minimum phase voltage A), Tb (i.e., the duty cycle of the middle phase voltage B), and Tc (i.e., the duty cycle of the maximum phase voltage C) of each phase high level are calculated. Figure 5 (a) is a waveform diagram of the three-phase voltage under low load condition according to an embodiment of the present invention. Figure 5 As shown in (a), at this time, Ta, Tb, and Tc are arranged from small to large, and Ta, Tb, and Tc are controlled to decrease by a preset value Tx2. Figure 5 (b) is a waveform diagram of the three-phase voltage after the duty cycle is reduced according to an embodiment of the present invention, the minimum sampling time is Td, the phase shift time required for the waveform of the intermediate phase voltage B is (Td-(Tb-Ta)), and the phase shift time required for the waveform of the maximum phase voltage C is (Td-(Tc-Tb)), Figure 4 (c) is a final waveform diagram of the voltages of each phase under low load according to an embodiment of the present invention. At this time, time is reserved for phase shifting, so that the phase shift adjustment range is widened.

[0082] Figure 6 Schematic diagram of dividing the non-zero area and the zero area of ​​a waveform according to an embodiment of the present invention. Figure 6 As shown, when at most two phases of the three-phase voltage are at high level, it is a non-zero area, and when all three phases of the three-phase voltage are at high level, it is a zero area.

[0083] The present invention will be described in detail below by taking the synthetic vector in the first sector as an example. Figure 7 is a flow chart of a current sampling method according to another embodiment of the present invention. Figure 7 As shown, the method includes:

[0084] S1, calculating the action duration T4 of the first voltage vector and the action duration T6 of the second voltage vector according to the synthesized vector.

[0085] The first voltage vector is obtained by decomposing the composite vector in the direction of the fourth non-zero vector V4, and the second voltage vector is obtained by decomposing the composite vector in the direction of the sixth non-zero vector V6.

[0086] S2, determining whether the action time length T4 of the first voltage vector + the action time length T6 of the second voltage vector × cos60° < the first threshold value Tmin holds, if so, executing step S3, if not, executing step S4.

[0087] S3, control the duty cycle of the three-phase voltage to increase by Tx1, and then execute step S7.

[0088] S4, determining whether the action time length T4 of the first voltage vector + the action time length T6 of the second voltage vector × cos60°> the second threshold value Tmax is established, if yes, executing step S5, if no, executing step S6.

[0089] S5, control the duty cycle of the three-phase voltage to decrease by Tx2 respectively, and then execute step S7.

[0090] S6, current sampling is performed according to the current three-phase voltage waveform.

[0091] S7, shift the phase of the three-phase voltage and then perform current sampling.

[0092] The current sampling method of this embodiment aims at the situation that when the motor load is small, the modulation ratio is also low, the duty cycle of each phase voltage is also low, the current distortion is relatively serious, and direct phase shifting of each phase voltage will cause current oscillation in the positive and negative directions in a relatively short time, and the sampling accuracy is also relatively low. The modulation ratio at low load is improved, and the situation that the low load current oscillates too fast and causes inaccurate sampling is improved; similarly, when the motor load is large, the modulation ratio is also high, the duty cycle of each phase voltage is also high, and the current sampling phase shift space is relatively small. When the duty cycle is relatively large, directly shifting the phase of each phase voltage will cause the situation to exceed the adjustment range, thereby reducing the modulation ratio at high load and widening the phase shift adjustment range.

[0093] Example 3

[0094] This embodiment provides a current sampling device, which is applied to a motor. The operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor. Figure 8 is a structural diagram of a current sampling device according to an embodiment of the present invention, such as Figure 8 As shown, the device comprises:

[0095] The determination module 10 is used to determine whether the region where the current synthetic vector of the motor is located is an observable region or an unobservable region.

[0096] As mentioned above Figure 3 As shown in , the first non-zero vector V1, the second non-zero vector V2, the third non-zero vector V3, the fourth non-zero vector V4, the fifth non-zero vector V5, and the sixth non-zero vector V6 are six non-zero vectors, and any two adjacent non-zero vectors are separated by 60°. The above six non-zero vectors divide the plane into six sectors. In the figure, the area between the two parallel dotted lines is the unobservable area, and the remaining area is the observable area. When the duty cycles of two of the three-phase voltages are similar, the reserved sampling time is insufficient, so it is necessary to move one or two of the phases to reserve enough sampling time.

[0097] The adjustment module 20 is used to adjust the duty cycle of the three-phase voltage of the motor according to the load state of the motor when the current synthetic vector of the motor is in the unobservable area.

[0098] The existing current sampling method fixes the widest pulse duty cycle and then shifts the middle pulse backward to obtain the second sampling point. Based on this processing, the narrowest pulse is shifted backward to obtain the first sampling point. In this way, two-phase currents are obtained by adjusting the sampling each time, and the third-phase current is obtained by calculation.

[0099] If the current synthetic vector of the motor is in the unobservable area, no matter the motor is in a low load state or a high load state, there is a problem of inaccurate current sampling results. In order to solve this problem, it is necessary to adjust the duty cycle of the three-phase voltage of the motor according to the load state of the motor, that is, adopt different duty cycle adjustment strategies for low load state and high load state respectively to ensure the accuracy of the current sampling results.

[0100] The phase shift module 30 is used to perform phase shift on the adjusted three-phase voltage and perform current sampling according to the three-phase voltage waveform after the phase shift.

[0101] The current sampling device of this embodiment determines whether the area where the current synthetic vector of the motor is located is an observable area or an unobservable area through the determination module 10, and adjusts the duty cycle of the three-phase voltage of the motor according to the load state of the motor when the current synthetic vector of the motor is in the unobservable area through the adjustment module 20; the adjusted three-phase voltage is phase-shifted through the phase shifting module 30, and current sampling is performed based on the three-phase voltage waveform after the phase shift. Regardless of whether the motor is running under low load or high load, the accuracy of the current sampling result can be guaranteed, thereby improving the accuracy of motor control.

[0102] Example 2

[0103] This embodiment provides another current sampling device. Fig. 9 This is a structural diagram of a current sampling device according to another embodiment of the present invention. In order to accurately determine whether the current synthetic vector of the motor is in the observable region or the unobservable region, as shown in FIG. Fig. 9 As shown, the above-mentioned determination module 10 includes:

[0104] The calculation unit 101 is used to calculate the time parameter according to the size and angle of the synthetic vector; the first determination unit 102 is used to determine whether the current synthetic vector of the motor is located in the observable area or the unobservable area according to the numerical range of the time parameter. The calculation unit 101 is specifically used to: decompose the synthetic vector into a first voltage vector and a second voltage vector according to the size and angle of the synthetic vector; calculate the action duration of the first voltage vector and the second voltage vector respectively; calculate the time parameter according to the action duration of the first voltage vector and the second voltage vector. Wherein, when calculating the time parameter according to the action duration of the first voltage vector and the second voltage vector, it is implemented according to the following formula: time parameter = action duration of the first voltage vector + action duration of the second voltage vector × cos60°; wherein, the angle of the second voltage vector is greater than the angle of the first voltage vector.

[0105] The determination unit 102 is specifically used to: determine whether the time parameter satisfies a value greater than or equal to the first threshold and less than or equal to the second threshold; if yes, determine that the current synthetic vector of the motor is in the observable area; if not, determine that the current synthetic vector of the motor is in the unobservable area.

[0106] When the motor is in a low-load state, the duty cycle of each phase voltage is small, and the current distortion is serious. If the waveform of the three-phase voltage is directly phase-shifted, current oscillations in the positive and negative directions will occur in a short time; when the motor is in a high-load state, the duty cycle of each phase is also high, and the phase shift space is relatively small. Directly shifting the waveform of the three-phase voltage will cause the adjustment range to be exceeded. It can be seen that different duty cycle adjustment strategies are required for different load states. Therefore, the above adjustment module 20 specifically includes: a load state judgment unit 201, which is used to judge the current load state of the motor; a first adjustment unit 202, which is used to control the duty cycle of the three-phase voltage and increase the preset value when the motor is currently in a low-load state. After the duty cycle increases, phase shifting is performed again to avoid current oscillations; a second adjustment unit 203 is used to control the duty cycle of the three-phase voltage and reduce the preset value when the motor is currently in a high-load state. The above can widen the phase shift adjustment range and avoid the problem of exceeding the adjustment range after the waveform of the three-phase voltage is phase-shifted.

[0107] According to the numerical range of the time parameter mentioned above, not only can it be determined whether the synthetic vector is in the observable area or the unobservable area, but also it can be determined whether the motor is currently in a low load state or a high load state. The load state judgment unit 201 is specifically used for: when the time parameter of the synthetic vector is less than the first threshold value, it is determined that the motor is currently in a low load state, that is, the synthetic vector is in the low load unobservable area; when the time parameter of the synthetic vector is greater than the second threshold value, it is determined that the motor is currently in a high load state, that is, the synthetic vector is in the high load unobservable area.

[0108] After the duty cycle of the three-phase voltage is adjusted through the above steps, in order to realize current sampling, the adjusted three-phase voltage needs to be phase-shifted. In order to realize the phase shifting function, the above-mentioned phase shifting module 30 specifically includes: a second determination unit 301, used to determine the maximum phase voltage C, the intermediate phase voltage B and the minimum phase voltage A; wherein the maximum phase voltage C is the phase voltage with the largest duty cycle among the three-phase voltages, the intermediate phase voltage B is the phase voltage with the intermediate duty cycle among the three-phase voltages, and the minimum phase voltage A is the phase voltage with the smallest duty cycle among the three-phase voltages; a control unit 302, used to control the waveform of the intermediate phase voltage B of the motor to move by a first preset time length, and control the waveform of the maximum phase voltage C of the motor to move by a second preset time length; wherein, when the waveform of the intermediate phase voltage B of the motor is controlled to move by the first preset time length, it is realized according to the following formula: the first preset time length = (Td-(Tb-Ta)); Td is the minimum sampling time length, Tb is the duty cycle of the intermediate phase voltage B, and Ta is the duty cycle of the minimum phase voltage A. When the waveform of the maximum phase voltage C of the motor is controlled to move the second preset time length, it is achieved according to the following formula: second preset time length = (Td-(Tc-Tb)); wherein Td is the minimum sampling time length, Tb is the duty cycle of the intermediate phase voltage B, and Tc is the duty cycle of the maximum phase voltage C.

[0109] Example 5

[0110] This embodiment provides a motor, including the current sampling device of the above embodiment, which is used to ensure sampling accuracy and thus improve the control accuracy of the motor.

[0111] Example 6

[0112] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above-mentioned current sampling method is implemented.

[0113] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0114] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A current sampling method, applied to a motor, wherein the operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor, characterized in that: The method comprises: Determine whether the current resultant vector of the motor is in the observable region or the unobservable region; If the current synthetic vector of the motor is in an unobservable area, the duty cycle of the three-phase voltage of the motor is adjusted according to the load state of the motor; including: judging the current load state of the motor; if the motor is currently in a low load state, controlling the duty cycle of the three-phase voltage to increase a preset value; if the motor is currently in a high load state, controlling the duty cycle of the three-phase voltage to decrease a preset value; The adjusted three-phase voltage is phase-shifted, and current sampling is performed according to the three-phase voltage waveform after the phase shift.

2. The method according to claim 1, characterized in that Determining whether the current synthetic vector of the motor is in the observable area or the unobservable area includes: Calculate the time parameter according to the magnitude and angle of the synthetic vector; It is determined whether the current synthetic vector of the motor is in the observable region or the unobservable region according to the numerical range of the time parameter.

3. The method according to claim 2, characterized in that Calculating a time parameter according to the magnitude and angle of the synthetic vector includes: Decomposing the resultant vector into a first voltage vector and a second voltage vector according to the magnitude and angle of the resultant vector; respectively calculating the action durations of the first voltage vector and the second voltage vector; The time parameter is calculated according to the action durations of the first voltage vector and the second voltage vector.

4. The method according to claim 3, characterized in that When calculating the time parameter according to the action duration of the first voltage vector and the second voltage vector, it is implemented according to the following formula: The time parameter=the action duration of the first voltage vector+the action duration of the second voltage vector×cos60°; wherein the angle of the second voltage vector is greater than the angle of the first voltage vector.

5. The method according to claim 2, characterized in that: Determining whether the current synthetic vector of the motor is in the observable region or the unobservable region according to the numerical range of the time parameter includes: Determine whether the time parameter satisfies a value greater than or equal to a first threshold and less than or equal to a second threshold; If yes, it is determined that the current resultant vector of the motor is in the observable region; If not, it is determined that the current resultant vector of the motor is in the unobservable region.

6. The method according to any one of claims 2 to 4, characterized in that Determine the current load state of the motor, including: If the time parameter of the synthetic vector is less than a first threshold value, it is determined that the motor is currently in a low-load state; If the time parameter of the resultant vector is greater than a second threshold, it is determined that the motor is currently in a high load state.

7. The method according to claim 1, characterized in that The adjusted three-phase voltage is phase-shifted, including: Determine a maximum phase voltage, an intermediate phase voltage and a minimum phase voltage; wherein the maximum phase voltage is the phase voltage with the largest duty cycle among the three-phase voltages, the intermediate phase voltage is the phase voltage with an intermediate duty cycle among the three-phase voltages, and the minimum phase voltage is the phase voltage with the smallest duty cycle among the three-phase voltages; The waveform of the intermediate phase voltage of the motor is controlled to move for a first preset time length, and the waveform of the maximum phase voltage of the motor is controlled to move for a second preset time length.

8. The method according to claim 7, characterized in that When controlling the waveform of the intermediate phase voltage of the motor to move for the first preset time length, it is achieved according to the following formula: The first preset duration=(Td-(Tb-Ta)); Wherein, the Td is the minimum sampling duration, the Tb is the duty cycle of the intermediate phase voltage, and the Ta is the duty cycle of the minimum phase voltage.

9. The method according to claim 7, characterized in that: When the waveform of the maximum phase voltage of the motor is controlled to move for a second preset time length, it is achieved according to the following formula: The second preset time length=(Td-(Tc-Tb)); Wherein, the Td is the minimum sampling duration, the Tb is the duty cycle of the intermediate phase voltage, and the Tc is the duty cycle of the maximum phase voltage.

10. A current sampling device, applied to a motor, wherein the operating parameters of the motor are controlled by a synthetic vector formed by synthesizing the three-phase voltage input to the motor, characterized in that: The device comprises: A determination module, used to determine whether the region where the current synthetic vector of the motor is located is an observable region or an unobservable region; An adjustment module, for adjusting the duty cycle of the three-phase voltage of the motor according to the load state of the motor when the current synthetic vector of the motor is in an unobservable area; including: judging the current load state of the motor; if the motor is currently in a low load state, controlling the duty cycle of the three-phase voltage to increase by a preset value; if the motor is currently in a high load state, controlling the duty cycle of the three-phase voltage to decrease by a preset value; The phase shift module is used to shift the phase of the adjusted three-phase voltage and perform current sampling according to the three-phase voltage waveform after the phase shift.

11. A motor, characterized in that: Includes the current sampling device as claimed in claim 10.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 9 is implemented.

Images