Motor control method, system and equipment and storage medium

Abstract

The invention discloses a motor control method, system and device and a storage medium, and is applied to the technical field of motors, and the method comprises the steps: obtaining the three-phase current of a motor based on a target sampling method; judging whether a preset switching condition is met or not; if not, controlling the motor through a space vector pulse width modulation mode based on the three-phase current; and if yes, controlling the motor through a discontinuous modulation mode based on the three-phase current. According to the scheme, the problem of sampling blind areas is avoided while three-resistor current sampling is used.

Description

Technical Field

[0001] The present invention relates to the field of motor technology, and in particular to a motor control method, system, device and storage medium. Background Art

[0002] At present, vector control technology is a relatively advanced and efficient technology in the field of inverter and servo motor control. The basis of vector control is current sampling. At this stage, there are three main methods for current sampling: phase current Hall sensor sampling, bus single resistor sampling, and three-resistor current sampling of the lower bridge arm. Phase current Hall sensor sampling is the sampling method with the highest sampling effect and accuracy, but the cost is high and it is not used in low-cost applications. The bus single resistor sampling method is low-cost, but the software program is complex and will limit the maximum output voltage. The three-resistor current sampling method takes into account the advantages of low cost and simple software implementation, and has become the preferred current sampling solution for low-cost inverters.

[0003] However, due to factors such as dead time, three-resistance current sampling cannot accurately and effectively collect current values ​​at any time, that is, there is a sampling blind area. Sampling in the sampling blind area will cause current distortion and even cause vector control failure. In order to avoid entering the sampling blind area, the current motor control system using three-resistance current sampling often limits the maximum output voltage, resulting in a reduction in the maximum DC voltage utilization rate.

[0004] In summary, how to avoid the problem of sampling blind area while using three-resistor current sampling is a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0005] The object of the present invention is to provide a motor control method, system, device and storage medium to avoid the problem of sampling blind area while using three-resistance current sampling.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a motor control method, comprising:

[0008] The three-phase current of the motor is obtained based on the target sampling method;

[0009] Determining whether a preset switching condition is met; wherein the switching condition includes a switching condition related to the modulation ratio or operating frequency of the motor;

[0010] If not, controlling the motor by space vector pulse width modulation based on the three-phase current;

[0011] If yes, the motor is controlled by discontinuous modulation based on the three-phase current.

[0012] In one implementation, determining whether a preset switching condition is met includes:

[0013] Determining whether the modulation ratio of the motor is higher than a preset modulation ratio threshold, or determining whether the operating frequency of the motor is higher than a preset rated frequency;

[0014] If the modulation ratio of the motor is higher than a preset modulation ratio threshold, or the operating frequency of the motor is higher than a preset rated frequency, determining that the preset switching condition is met;

[0015] If the modulation ratio of the motor is not higher than the modulation ratio threshold, or the operating frequency of the motor is not higher than the rated frequency, it is determined that the switching condition is not satisfied.

[0016] In one embodiment, the switching condition is related to the dead time length T of the motor. d And the switching tube noise duration T n The relevant switching conditions, correspondingly, determine whether the preset switching conditions are met, including:

[0017] Determine the dead time duration T of the motor d And the switching tube noise duration T n ;

[0018] Determine the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle; wherein the first duration T1 represents the duration from the X-phase upper bridge arm shutdown moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0019] If yes, it is determined that the preset switching condition is met;

[0020] If not, it is determined that the switching condition is not satisfied.

[0021] In one embodiment, the switching condition is related to the current sampling time T of the motor. s The relevant switching conditions, correspondingly, determine whether the preset switching conditions are met, including:

[0022] Determine the current sampling time T of the motor s ;

[0023] Determine the current sampling time T sWhether it is greater than the second time length T2 of the next carrier cycle; wherein the second time length T2 represents the time length from the default current sampling moment to the X-phase lower bridge arm shut-off moment of the next carrier cycle;

[0024] If yes, it is determined that the preset switching condition is met;

[0025] If not, it is determined that the switching condition is not satisfied.

[0026] In one embodiment, the switching condition is related to the dead time length T of the motor. d , the switching tube noise duration T n And the current sampling time T s The relevant switching conditions, correspondingly, determine whether the preset switching conditions are met, including:

[0027] Determine the dead time duration T of the motor d , the switching tube noise duration T n And the current sampling time T s ;

[0028] Determine the dead time length T of the motor d , the switching tube noise duration T n And the current sampling time T s is greater than the sum of the first duration T1 of the current carrier cycle and the second duration T2 of the next carrier cycle;

[0029] If yes, it is determined that the preset switching condition is met.

[0030] In one implementation, after determining that the switching condition is met, the method further includes:

[0031] Determine whether the preset sampling time shift condition is met; wherein the sampling time shift condition is the dead zone length T of the motor d , the switching tube noise duration T n And the current sampling time T s Related sampling instant shift conditions;

[0032] If not, the motor is controlled by discontinuous modulation based on the three-phase current, and the current sampling moment used in the control process is a default current sampling moment;

[0033] If yes, the motor is controlled by discontinuous modulation based on the three-phase current, and the current sampling time used in the control process is the shifted current sampling time, so that the current sampling time after the shift is not in the dead zone of the motor. d The motor switch noise duration T nThe time from the current sampling time after the shift to the X-phase lower bridge arm shutdown time of the next carrier cycle is greater than the motor current sampling time T s .

[0034] In one implementation, determining whether a preset sampling time shift condition is met includes:

[0035] If the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle, or the current sampling duration T s , is greater than the second duration T2 of the next carrier cycle, it is determined that the sampling time shift condition is met, otherwise it is determined that the sampling time shift condition is not met;

[0036] Accordingly, the rules for shifting the current sampling time specifically include:

[0037] If the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle, the current sampling moment is shifted backward, and the duration of the backward shift is equal to the dead zone duration T d The switching tube noise duration T n The time difference is obtained by subtracting the first duration T1 of the current carrier cycle from the sum of

[0038] If the current sampling time T s , is greater than the second duration T2 of the next carrier cycle, the current sampling moment is shifted forward, and the duration of the forward shift is equal to the current sampling duration T s The time difference is obtained by subtracting the second duration T2 of the next carrier cycle.

[0039] In a second aspect, the present invention provides a motor control system, comprising:

[0040] A sampling module, used to obtain the three-phase current of the motor based on a target sampling method;

[0041] A modulation mode switching judgment module, used to judge whether a preset switching condition is met; wherein the switching condition includes a switching condition related to the modulation ratio or operating frequency of the motor;

[0042] If not, triggering a space vector pulse width modulation module, wherein the space vector pulse width modulation module is used to control the motor by means of space vector pulse width modulation based on the three-phase current;

[0043] If yes, a discontinuous modulation module is triggered, and the discontinuous modulation module is used to control the motor by discontinuous modulation based on the three-phase current.

[0044] In a third aspect, the present invention provides a motor control device, comprising:

[0045] Memory for storing computer programs;

[0046] A processor is used to execute the computer program to implement the steps of the motor control method as described above.

[0047] In a fourth aspect, the present invention provides a computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the motor control method as described above are implemented.

[0048] The technical solution provided by the embodiment of the present invention is applied. Considering the problem of sampling blind area when using three-resistance current sampling, it is because when the modulation ratio increases, the conduction time of the lower bridge arm will be reduced, so that in part of the carrier cycle, the conduction time of the lower bridge arm of a certain phase is very short, that is, the sampling window is too short, which leads to the inability to accurately and effectively collect the current value. Therefore, in the present application scheme, it will be judged whether the preset switching condition is met. If it is not met, it means that the modulation ratio is not high, and the motor can be directly controlled by space vector pulse width modulation based on the three-phase current, and there will be no problem. If the preset switching condition is met, it means that the modulation ratio is relatively high, and a sampling blind area may appear. The present application will switch the space vector pulse width modulation to discontinuous modulation, that is, at this time, the motor is controlled by discontinuous modulation based on the three-phase current. The use of discontinuous modulation can extend the effective vector action time, and at the same time, the scattered zero vector is concentrated at the carrier underflow moment, which also widens the sampling window, which is conducive to the three-resistance current sampling method to accurately and effectively collect the current value and solve the problem of sampling blind area.

[0049] In summary, in the present application, while using the target sampling method for three-resistance current sampling, the problem of sampling blind area is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1A flowchart of a motor control method provided in a specific embodiment of the present invention;

[0052] Figure 2 is a vector diagram of sector distribution and reference voltage;

[0053] Figure 3 Schematic diagram of current sampling time in a certain carrier cycle in sector I;

[0054] Figure 4 Schematic diagram of the switching signals of the U-phase upper bridge arm (U-High) and the lower bridge arm (U-Low) and the current waveform passing through the U-phase lower bridge arm in a specific implementation manner;

[0055] Figure 5 It is a schematic diagram of the switching signals of the U phase, the V phase and the W phase and the current waveform of the lower bridge arm of each phase after the modulation ratio is increased to a certain level in a specific implementation manner;

[0056] Figure 6 A schematic diagram of the switching signals of the U phase, the V phase and the W phase and the current waveforms of the lower bridge arms of each phase after switching to discontinuous modulation in a specific implementation manner;

[0057] Figure 7a A schematic diagram of a current sampling moment shifting backward in a specific implementation manner;

[0058] Figure 7b A schematic diagram of a current sampling moment shifting forward in a specific implementation manner;

[0059] Figure 8 A schematic diagram of the current sampling effect of the conventional sampling scheme and the current sampling effect of the scheme of the present application when the modulation ratio is relatively high;

[0060] Fig. 9 A schematic diagram of the structure of a motor control system provided by a specific embodiment of the present invention;

[0061] Fig.10 A schematic diagram of the structure of a motor control device provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0062] The core of the present invention is to provide a motor control method, which avoids the problem of sampling blind area while using the target sampling method for three-resistance current sampling.

[0063] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiment 908 is only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0064] Please refer to Figure 1 , Figure 1 The present invention provides a flow chart of a motor control method according to a specific embodiment of the present invention. The motor control method may include the following steps:

[0065] Step S101: obtaining the three-phase current of the motor based on the target sampling method.

[0066] Since the three-resistance current sampling method has the advantages of low cost and simple software implementation, the target sampling method described in the present application scheme can generally be the three-resistance current sampling method.

[0067] For the three-resistance current sampling method, in terms of circuit structure, three sampling resistors need to be set between the lower bridge arm of the U phase and the negative bus, between the lower bridge arm of the V phase and the negative bus, and between the lower bridge arm of the W phase and the negative bus. Only after the lower bridge arm switch tube of a certain phase is turned on, the current will flow through the sampling resistor of the phase, and then the current sampling of the phase can be performed. With the continuous increase of the modulation ratio, the conduction time of the lower bridge arm switch tube will continue to decrease. At this time, due to the influence of the dead zone time, the switch tube noise time and the current sampling time, it is very likely that the current noise point will be sampled or even no current will be sampled.

[0068] See also Figure 2 , which is a vector diagram of sector distribution and reference voltage. When the motor is controlled by space vector pulse width modulation, as shown in Figure 2 As shown, it can be divided into 6 sectors. Figure 2 U ref It is the synthetic voltage vector required for space vector pulse width modulation. At this time, the synthetic voltage vector is located in sector I.

[0069] The following text will take sector I as an example for description. In sector I, the conduction time of the lower bridge arm of phase U is the shortest, the conduction time of the lower bridge arm of phase V is medium, and the conduction time of the lower bridge arm of phase W is the longest. Since the current of the phase with the longest conduction time can be accurately sampled, the key lies in the processing of the phase with the shortest conduction time and the middle phase, especially the processing of the phase with the shortest conduction time. Figure 3 , which is a schematic diagram of the current sampling time in a certain carrier cycle in sector I. Figure 3PWM1L, PWM2L, and PWM3L represent the PWM pulses of the lower bridge arms of phase U, phase V, and phase W respectively. When the PWM pulse is at a high level, the corresponding lower bridge arm is turned on. It can be seen that the lower bridge arm of phase W is turned on for the longest time, and the lower bridge arm of phase U is turned on for the shortest time.

[0070] See also Figure 4 , is a schematic diagram of the switching signals of the upper bridge arm (U-High) and the lower bridge arm (U-Low) of the U phase and the current waveform passing through the lower bridge arm of the U phase in a specific implementation. It can be seen that when the modulation ratio is not high, reliable sampling can be obtained at the default current sampling time, that is, the carrier underflow time (CTR=0).

[0071] CTR refers to the carrier count cycle value. CTR=0 is the carrier underflow moment, which is the default current sampling moment, or the default sampling point, reflecting the lowest point of the triangular carrier. In addition, Figure 4 The CTR=TBPRD in the equation indicates that the carrier count cycle value reaches the maximum value. The moment when CTR=TBPRD is the middle moment of a carrier cycle, reflecting the highest point of the triangular carrier. Therefore, it can be understood that Figure 4 The time from CTR=TBPRD on the left to CTR=0 is half the time of the previous carrier cycle, and the time from CTR=0 to CTR=TBPRD on the right is half the time of the next carrier cycle.

[0072] Figure 4 Reliable current sampling can be obtained in the modulation ratio, but when the modulation ratio increases to a certain extent, the lower bridge arm conduction time will be shortened, and the sampling point may be located in the dead zone length T d Or the switching tube noise duration T n or after the trigger sampling is less than T s The lower bridge arm is already shut down after a certain time. Figure 5 , is a schematic diagram of the switching signals of the U phase, V phase and W phase and the current waveforms of the lower bridge arms of each phase after the modulation ratio is increased to a certain level in a specific implementation method.

[0073] It can be seen that in Figure 5 In the example, the default current sampling time (CTR=0) is located at the switching tube noise duration T n At this time, the U-phase current can no longer obtain reliable current sampling, and the currents of the V-phase and W-phases also generate noise due to the action of the U-phase switching tube, which affects the current sampling quality of the V-phase and W-phases.

[0074] Step S102: Determine whether the preset switching condition is met. If not, execute step S103; if yes, execute step S104.

[0075] As described above, when the modulation ratio increases to a certain extent, the conduction time of the lower bridge arm will be shortened, and the sampling point may be located in the dead zone length T d Or the switching tube noise duration T n or after the trigger sampling is less than T s The lower bridge arm has been turned off within a certain period of time, so the present application presets a switching condition. The switching condition is a switching condition related to the modulation ratio of the motor, that is, the switching condition can reflect the modulation ratio of the motor. If the switching condition is met, it means that the current modulation is relatively high, so the space vector pulse width modulation will be switched to discontinuous modulation. Conversely, if the switching condition is not met, it means that the space vector pulse width modulation with better performance can still be used. The operating frequency is also a reflection of the modulation ratio. Therefore, the switching condition may include a switching condition related to the modulation ratio or operating frequency of the motor.

[0076] The specific content of the switching condition can be set according to actual needs, and the functional requirements of the present application can be met, that is, as long as it can directly or indirectly reflect that the modulation is relatively high. For example, in a specific implementation of the present invention, step S102 can specifically include:

[0077] Determining whether the modulation ratio of the motor is higher than a preset modulation ratio threshold, or determining whether the operating frequency of the motor is higher than a preset rated frequency;

[0078] If the modulation ratio of the motor is higher than a preset modulation ratio threshold, or the operating frequency of the motor is higher than a preset rated frequency, it is determined that the preset switching condition is met;

[0079] If the modulation ratio of the motor is not higher than the modulation ratio threshold, or the operating frequency of the motor is not higher than the rated frequency, it is determined that the switching condition is not satisfied.

[0080] This implementation takes into account that if the switching condition is met, it means that the modulation of the motor is relatively high. Therefore, a simple and convenient implementation is to directly judge based on the modulation ratio to determine whether the switching condition is met, that is, it can be directly judged whether the modulation ratio of the motor is higher than the preset modulation ratio threshold. If the modulation ratio is higher than the preset modulation ratio threshold, it can be determined that the switching condition is met, otherwise it can be determined that the switching condition is not met.

[0081] And this implementation also takes into account that the operating frequency of the motor is also a reflection of the modulation ratio. Therefore, it can also be determined whether the operating frequency is higher than the preset rated frequency. If the operating frequency is higher than the preset rated frequency, it can also be determined that the switching condition is met. Otherwise, it can be determined that the switching condition is not met. In practical applications, for the modulation ratio and the operating frequency, one can be selected for judgment. This implementation is based on the modulation ratio or the operating frequency of the motor, and can determine whether the switching condition is met by a simple threshold judgment method, which is very simple and convenient in implementation.

[0082] Step S103: Based on the three-phase current, the motor is controlled by space vector pulse width modulation.

[0083] When the switching condition is not met, there will be no sampling blind area, and reliable current sampling can be obtained. Therefore, space vector pulse width modulation with better performance can still be used without switching to discontinuous modulation.

[0084] Step S104: Based on the three-phase current, the motor is controlled by discontinuous modulation.

[0085] When the switching conditions are met, it means that the current motor modulation is relatively high. If space vector pulse width modulation is still used, reliable current sampling cannot be obtained due to the blind spot problem. In this application, it will be switched to discontinuous modulation. For the same basic voltage vector action time, when discontinuous modulation is used, the current noise caused by the switch tube can be effectively avoided by concentrating the zero vector action time, and the current sampling window can be effectively widened.

[0086] See also Figure 6 , is a schematic diagram of the switching signals of the U phase, V phase and W phase and the current waveform of the lower bridge arm of each phase after switching to discontinuous modulation. Due to the widening of the current sampling window, reliable current sampling can be performed. In addition, it should be noted that after switching to discontinuous modulation, the currents of the U phase, V phase and W phase can be obtained by sampling, and the currents of the V phase and W phase can also be obtained by sampling, and then the U phase current is obtained by Kirchhoff's current law, that is, the principle that the vector sum of the three-phase current is 0. In practical applications, after switching to discontinuous modulation, when the operating frequency of the motor exceeds a certain set frequency, the current of the minimum phase will be determined by the currents of the remaining two phases. The minimum phase described here is the phase with the shortest conduction time of the lower bridge arm in the current carrier cycle, such as the U phase in the above example. When the operating frequency of the motor does not exceed the set frequency, since the conduction time of the lower bridge arm of the minimum phase is not particularly short, the currents of the U phase, V phase and W phase can be obtained by sampling.

[0087] It should also be noted that after switching to discontinuous modulation, as the motor runs, when it is determined that the switching condition is not met, the space vector pulse width modulation mode can be restored. The performance of space vector pulse width modulation is better than discontinuous modulation.

[0088] In a specific implementation of the present invention, after determining that the switching condition is met, the following steps may also be included:

[0089] Determine whether the preset sampling time shift condition is met. The sampling time shift condition is the dead zone length T of the motor. d , the switching tube noise duration T nAnd the current sampling time T s The sampling time shift condition is related to the sampling time shift condition. When the sampling time shift condition is met, it means that the modulation ratio is particularly high.

[0090] If not, the motor is controlled by discontinuous modulation based on the three-phase current, and the current sampling moment used in the control process is the default current sampling moment;

[0091] If yes, the motor is controlled by discontinuous modulation based on the three-phase current, and the current sampling time used in the control process is the shifted current sampling time, so that the current sampling time after the shift is not in the dead zone of the motor. d The motor switch noise duration T n The time from the current sampling time after the shift to the X-phase lower bridge arm shutdown time of the next carrier cycle is greater than the motor current sampling time T s ;

[0092] Among them, the X phase represents the phase with the shortest conduction time of the lower bridge arm in the current carrier cycle.

[0093] This implementation takes into account that when the modulation ratio is particularly high, even if discontinuous modulation is used to control the motor, there may still be a blind spot in the current sampling moment resulting in distortion of the sampled current. This can be addressed in this implementation by shifting the current sampling moment.

[0094] Specifically, after determining that the switching condition is met, and thus controlling the motor through discontinuous modulation based on the three-phase current, this implementation further determines whether a preset sampling time shift condition is met.

[0095] If the sampling time shifting condition is not met, it means that the modulation ratio is not particularly high. At this time, there is no need to shift the current sampling time. That is, in the process of controlling the motor in a discontinuous modulation manner, the current sampling time used is still the default current sampling time, which is the carrier underflow time (CTR=0) described in the above example.

[0096] If the sampling time shift condition is met, it means that the modulation ratio is already very high. In this implementation, the current sampling time will be shifted, that is, in the process of controlling the motor in a discontinuous modulation manner, the current sampling time used is the shifted current sampling time.

[0097] The specific rules for shifting can be set as needed, but it is necessary to ensure that the current sampling time after the shift should not be in the dead zone of the motor. d The motor should not be in the switching noise period Tn The time from the current sampling time after the shift to the X-phase lower bridge arm shutdown time of the next carrier cycle is greater than the motor current sampling time T s .

[0098] In short, the current sampling time after the shift should not be in the dead zone time T d It should not be within the switching tube noise period T n , and when a phase current sampling begins, the subsequent current sampling time T s In this case, the lower bridge arm of the phase is not turned off to ensure the accuracy of current sampling.

[0099] In addition, in practical applications, if the current sampling time needs to be shifted, the shift distance can usually be converted into a CTR change value and assigned to the registers in the comparison modules such as CMPB, CMPC, and CMPD, and the relevant triggering mode is configured to make the shift operation described in this implementation effective. Of course, when it is determined that the shift is no longer needed, the value of the relevant register can be reset to zero, so that the current sampling time is restored to the default current sampling time of CTR=0.

[0100] In addition, it should be noted that the determination of whether shifting is required, that is, whether the shifting condition at the sampling moment is satisfied, can usually be performed in each carrier cycle, that is, even if shifting is required, it is only effective in a corresponding single carrier cycle.

[0101] In this implementation, by determining the sampling time shift condition, the current sampling time can be shifted when the modulation ratio is particularly high, so that the current sampling time after the shift is not within the dead zone length T of the motor. d The motor switch noise duration T n The time from the current sampling time after the shift to the X-phase lower bridge arm shutdown time of the next carrier cycle is greater than the motor current sampling time T s Therefore, the reliability of sampling is further guaranteed, that is, even if the modulation ratio is particularly high, this implementation method can still ensure the reliability of sampling by shifting the sampling time.

[0102] In a specific implementation of the present invention, determining whether a preset sampling time shift condition is met includes:

[0103] If the dead zone duration is T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle, or the current sampling duration T s, is greater than the second duration T2 of the next carrier cycle, it is determined that the sampling time shift condition is met, otherwise it is determined that the sampling time shift condition is not met;

[0104] Accordingly, the rules for shifting the current sampling time include:

[0105] If the dead zone duration is T d The switching tube noise duration T n If the sum of is greater than the first duration T1 of the current carrier cycle, the current sampling moment is shifted backward, and the duration of the backward shift is equal to the dead zone duration T d The switching tube noise duration T n The time difference is obtained by subtracting the first duration T1 of the current carrier cycle from the sum of

[0106] Among them, the first duration T1 represents the duration from the X-phase upper bridge arm shutdown moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0107] If the current sampling time is T s , is greater than the second duration T2 of the next carrier cycle, the current sampling moment is shifted forward, and the duration of the forward shift is equal to the current sampling duration T s The time difference obtained by subtracting the second duration T2 of the next carrier cycle;

[0108] The second time duration T2 represents the time duration from the default current sampling moment to the X-phase lower bridge arm shut-off moment of the next carrier cycle.

[0109] In this implementation, a specific sampling time shift condition and shift rule are set.

[0110] Dead zone duration T d , the switching tube noise duration T n And the current sampling time T s , which can be obtained by measuring with an oscilloscope, consulting the chip manual, etc., and will not change with the carrier period.

[0111] For easier understanding, please refer to Figure 7a and Figure 7b ,exist Figure 7a In the example, the dead time is T d The switching tube noise duration T nThe sum of is greater than the first duration T1 of the current carrier cycle. Since in this example, the phase with the shortest conduction time of the lower bridge arm in the current carrier cycle is the U phase, X is the U phase among the U phase, V phase and W phase. The first duration T1 of the current carrier cycle is the duration from the U phase upper bridge arm shutdown moment to the default current sampling moment (CTR=0), which is convenient for viewing Figure 7a The first duration T1 of the current carrier cycle has been shown in FIG.

[0112] It can be seen that in Figure 7a In the example, due to the short sampling window, a dead zone duration T d The switching tube noise duration T n The sum of is greater than the first duration T1 of the current carrier cycle, so that the default current sampling time (CTR=0) is located at the switch tube noise duration T n Within, the reliability of current sampling cannot be guaranteed at this time, so the current sampling time needs to be shifted back, and the length of the shift is = T d +T n -T1.

[0113] And in Figure 7b In the example, at the moment when CTR=0, the previous carrier cycle ends. If current sampling is performed at this time, since current sampling takes a certain amount of time, that is, at least the current sampling time T is required. s Therefore, after CTR=0, the lower bridge arm of phase X (in this example, phase U) must be at least T s Then turn off to ensure the reliability of current sampling. Therefore, if the current sampling time is T s If it is greater than the second time length T2 of the next carrier cycle, the current sampling time needs to be shifted forward, and the forward shift time length is = T s -T2. Easy to see Figure 7b The second time duration T2 is also shown in FIG.

[0114] In addition, it should be noted that in actual applications, after switching to discontinuous modulation, T d +T n is greater than T1, and T s When the current sampling time is greater than T2, the problem cannot be solved by shifting the current sampling time forward or backward.

[0115] In this implementation, a specific sampling time shift condition is set. Whether the sampling time shift condition is met accurately corresponds to whether a sampling blind area will occur. In addition, this implementation discloses a specific shift rule. From the above description, it can be seen that by shifting forward or backward according to the description of this implementation, the sampling blind area can be effectively avoided and the sampling reliability can be guaranteed. In addition, the shift rule of this implementation is simple and easy to implement.

[0116] In a specific implementation of the present invention, step S102 may specifically include:

[0117] Determine the dead time T of the motor d And the switching tube noise duration T n ;

[0118] Determine the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle; wherein the first duration T1 represents the duration from the X-phase upper bridge arm shut-off moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0119] If yes, it is determined that the preset switching condition is met;

[0120] If not, it is determined that the switching condition is not satisfied.

[0121] In the above implementation, an example is given for step S102. For example, whether the switching condition is met can be directly determined based on the modulation ratio or the operating frequency, which is very simple and convenient to implement.

[0122] This implementation further takes into account that when the modulation is relatively high, there will indeed be a current sampling blind spot, which affects the reliability of current sampling. However, this situation does not occur in every carrier cycle. Therefore, other more accurate judgment methods can be used as switching conditions. Under the premise of ensuring the reliability of current sampling, the motor can be controlled as much as possible through the space vector pulse width modulation method with better performance.

[0123] Specifically, in this implementation, based on the dead zone duration T d , the switching tube noise duration T n and the first time length T1 to determine whether the switching condition is met. Therefore, in this embodiment, the switching condition is specifically the dead zone time length T of the motor. d And the switching tube noise duration T nThe relevant switching conditions, that is, this implementation method does not directly determine whether the switching conditions are met by judging the modulation ratio, but indirectly reflects that the current modulation ratio of the motor is relatively high through other means.

[0124] In this implementation, the dead zone duration T is determined. d The switching tube noise duration T n Is the sum of the current sampling time greater than the first time length T1 of the current carrier cycle? If this happens, it means that the default current sampling time is T d or T n If the modulation mode is not switched, the accuracy of current sampling cannot be guaranteed, so it is determined that the switching condition is met to switch the modulation mode. Otherwise, it is determined that the switching condition is not met and there is no need to switch the modulation mode.

[0125] In a specific implementation of the present invention, step S102 may specifically include:

[0126] Determine the current sampling time T of the motor s ;

[0127] Determine the current sampling time T s Whether it is greater than the second duration T2 of the next carrier cycle; wherein the second duration T2 represents the duration from the default current sampling moment to the X-phase lower bridge arm shut-off moment of the next carrier cycle; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0128] If yes, it is determined that the preset switching condition is met;

[0129] If not, it is determined that the switching condition is not satisfied.

[0130] As described above, when the modulation is relatively high, there will indeed be a current sampling blind area, which affects the reliability of current sampling, but this situation does not occur in every carrier cycle. Therefore, other more accurate judgment methods can be used as the content of the switching condition. Under the premise of ensuring the reliability of current sampling, the motor can be controlled as much as possible through the space vector pulse width modulation method with better performance.

[0131] In one embodiment of the above, based on the dead zone duration T d , the switching tube noise duration T n and the first time length T1 to determine whether the switching condition is met. In this implementation, the current sampling time length T sThe second time period T2 is compared to determine whether the switching condition is satisfied. This also achieves the effect of controlling the motor by using a space vector pulse width modulation method with better performance as much as possible while ensuring the reliability of current sampling.

[0132] In this implementation, the switching condition is specifically related to the motor current sampling time T s Related switching conditions.

[0133] This implementation method takes into account that if the current sampling time T is determined s is greater than the second duration T2 of the next carrier cycle, indicating that from the default current sampling moment, less than T s Within the time length, the lower bridge arm of the X phase will be turned off. If the modulation mode is not switched, the accuracy of current sampling cannot be guaranteed. Therefore, it is determined that the switching condition is met to switch the modulation mode. Otherwise, it is determined that the switching condition is not met and there is no need to switch the modulation mode.

[0134] In a specific implementation of the present invention, step S102 may specifically include:

[0135] Determine the dead time T of the motor d , the switching tube noise duration T n And the current sampling time T s ;

[0136] Determine the dead time T of the motor d , the switching tube noise duration T n And the current sampling time T s is greater than the sum of the first duration T1 of the current carrier cycle and the second duration T2 of the next carrier cycle;

[0137] If yes, it is determined that the switching condition is met;

[0138] If not, it is determined that the switching condition is not satisfied;

[0139] Among them, the first time length T1 represents the time length from the X-phase upper bridge arm shutdown moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction time in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle; the second time length T2 represents the time length from the default current sampling moment to the X-phase lower bridge arm shutdown moment of the next carrier cycle.

[0140] This implementation method is the comprehensive dead zone time T d , the switching tube noise duration T n And the current sampling time T s Therefore, the switching condition is specifically related to the dead time length T of the motor.d , the switching tube noise duration T n And the current sampling time T s Related switching conditions.

[0141] Dead zone duration T d , the switching tube noise duration T n And the current sampling time T s The sum of the first duration T1 of the current carrier cycle and the second duration T2 of the next carrier cycle can be regarded as the conduction width of the lower bridge arm of the minimum phase (eg, the U phase in the above embodiments).

[0142] If the sampling window length is greater than the sum of the first duration T1 of the current carrier cycle and the second duration T2 of the next carrier cycle, it means that no matter when sampling at any time in the sampling window, the current sampling time will be T d or T n or the remaining window length after the current sampling moment is less than T s In this case, the accuracy of current sampling cannot be guaranteed, so it is determined that the switching conditions are met to switch the modulation mode.

[0143] This implementation also achieves the effect of controlling the motor by using the space vector pulse width modulation method with better performance as much as possible while ensuring the reliability of current sampling. In addition, since this implementation also takes into account the dead zone time length T d , the switching tube noise duration T n And the current sampling time T s , making this implementation highly reliable, that is, if this implementation is used and it is determined that the preset switching condition is met, it can be reliably determined that if the modulation mode is not switched, there will be a sampling blind area. Conversely, if this implementation is used and it is determined that the preset switching condition is not met, it can be reliably determined that the current use of space vector pulse width modulation is sufficient, and there will be no sampling blind area. Therefore, this implementation is also the implementation that is usually commonly used in practical applications.

[0144] The technical solution provided by the embodiment of the present invention is applied. Considering the problem of sampling blind area when using three-resistance current sampling, it is because when the modulation ratio increases, the conduction time of the lower bridge arm will be reduced, so that in part of the carrier cycle, the conduction time of the lower bridge arm of a certain phase is very short, that is, the sampling window is too short, which leads to the inability to accurately and effectively collect the current value. Therefore, in the present application scheme, it will be judged whether the preset switching condition is met. If it is not met, it means that the modulation ratio is not high, and the motor can be directly controlled by space vector pulse width modulation based on the three-phase current, and there will be no problem. If the preset switching condition is met, it means that the modulation ratio is relatively high, and a sampling blind area may appear. The present application will switch the space vector pulse width modulation to discontinuous modulation, that is, at this time, the motor is controlled by discontinuous modulation based on the three-phase current. The discontinuous modulation method can extend the effective vector action time, and at the same time, the scattered zero vector is concentrated at the carrier underflow moment, which also widens the sampling window, which is conducive to the three-resistance current sampling method to accurately and effectively collect the current value and solve the problem of sampling blind area.

[0145] In summary, in the present application, while using the target sampling method for three-resistance current sampling, the problem of sampling blind area is avoided.

[0146] See also Figure 8 , which is a schematic diagram of the current sampling effect of the traditional sampling scheme and the current sampling effect of the present application scheme when the modulation is relatively high. It can be seen that the present application scheme effectively avoids the problem of blind spots and can accurately and effectively collect current values.

[0147] Corresponding to the above method embodiment, an embodiment of the present invention further provides a motor control system, which can be referred to in correspondence with the above.

[0148] See also Fig. 9 FIG. 1 is a schematic diagram of a motor control system provided by a specific embodiment of the present invention, comprising:

[0149] A sampling module 901 is used to obtain the three-phase current of the motor based on a target sampling method;

[0150] The modulation mode switching judgment module 902 is used to judge whether a preset switching condition is met; wherein the switching condition includes a switching condition related to the modulation ratio or the operating frequency of the motor;

[0151] If not, the space vector pulse width modulation module 903 is triggered, and the space vector pulse width modulation module 903 is used to control the motor by space vector pulse width modulation based on the three-phase current;

[0152] If yes, the discontinuous modulation module 904 is triggered, and the discontinuous modulation module 904 is used to control the motor through discontinuous modulation based on the three-phase current.

[0153] In a specific implementation of the present invention, the modulation mode switching determination module 902 is specifically used to:

[0154] Determining whether the modulation ratio of the motor is higher than a preset modulation ratio threshold, or determining whether the operating frequency of the motor is higher than a preset rated frequency;

[0155] If the modulation ratio of the motor is higher than a preset modulation ratio threshold, or the operating frequency of the motor is higher than a preset rated frequency, it is determined that the preset switching condition is met;

[0156] If the modulation ratio of the motor is not higher than the modulation ratio threshold, or the operating frequency of the motor is not higher than the rated frequency, it is determined that the switching condition is not satisfied.

[0157] In a specific embodiment of the present invention, the switching condition is the dead time length T of the motor. d And the switching tube noise duration T n The modulation mode switching determination module 902 is specifically used for:

[0158] Determine the dead time T of the motor d And the switching tube noise duration T n ;

[0159] Determine the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle; wherein the first duration T1 represents the duration from the X-phase upper bridge arm shut-off moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0160] If yes, it is determined that the preset switching condition is met;

[0161] If not, it is determined that the switching condition is not satisfied.

[0162] In a specific embodiment of the present invention, the switching condition is the current sampling time T of the motor. s The modulation mode switching determination module 902 is specifically used for:

[0163] Determine the current sampling time T of the motor s ;

[0164] Determine the current sampling time T sWhether it is greater than the second duration T2 of the next carrier cycle; wherein the second duration T2 represents the duration from the default current sampling moment to the X-phase lower bridge arm shut-off moment of the next carrier cycle; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0165] If yes, it is determined that the preset switching condition is met;

[0166] If not, it is determined that the switching condition is not satisfied.

[0167] In a specific embodiment of the present invention, the switching condition is the dead time length T of the motor. d , the switching tube noise duration T n And the current sampling time T s The modulation mode switching determination module 902 is specifically used for:

[0168] Determine the dead time T of the motor d , the switching tube noise duration T n And the current sampling time T s ;

[0169] Determine the dead time T of the motor d , the switching tube noise duration T n And the current sampling time T s is greater than the sum of the first duration T1 of the current carrier cycle and the second duration T2 of the next carrier cycle;

[0170] If yes, it is determined that the preset switching condition is met;

[0171] If not, it is determined that the switching condition is not satisfied;

[0172] Among them, the first time length T1 represents the time length from the X-phase upper bridge arm shutdown moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction time in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle; the second time length T2 represents the time length from the default current sampling moment to the X-phase lower bridge arm shutdown moment of the next carrier cycle.

[0173] In a specific embodiment of the present invention, it also includes:

[0174] The sampling point shift judgment module is used to judge whether the preset sampling time shift condition is met; wherein the sampling time shift condition is the dead zone length T of the motor. d , the switching tube noise duration T n And the current sampling time T s Related sampling instant shift conditions;

[0175] If not, triggering the first execution module to control the motor based on the three-phase current through discontinuous modulation, and the current sampling moment used in the control process is the default current sampling moment;

[0176] If yes, the second execution module is triggered to control the motor based on the three-phase current by discontinuous modulation, and the current sampling time used in the control process is the shifted current sampling time, so that the current sampling time after the shift is not in the dead zone length T of the motor d The motor switch noise duration T n The time from the current sampling time after the shift to the X-phase lower bridge arm shutdown time of the next carrier cycle is greater than the motor current sampling time T s ;

[0177] Among them, the X phase represents the phase with the shortest conduction time of the lower bridge arm in the current carrier cycle.

[0178] In a specific implementation of the present invention, the sampling point shift judgment module is specifically used to:

[0179] If the dead zone duration is T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle, or the current sampling duration T s , is greater than the second duration T2 of the next carrier cycle, it is determined that the sampling time shift condition is met, otherwise it is determined that the sampling time shift condition is not met;

[0180] Accordingly, the rules for shifting the current sampling time specifically include:

[0181] If the dead zone duration is T d The switching tube noise duration T n If the sum of is greater than the first duration T1 of the current carrier cycle, the current sampling moment is shifted backward, and the duration of the backward shift is equal to the dead zone duration T d The switching tube noise duration T n The time difference is obtained by subtracting the first duration T1 of the current carrier cycle from the sum of

[0182] Among them, the first duration T1 represents the duration from the X-phase upper bridge arm shutdown moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle;

[0183] If the current sampling time is T s, is greater than the second duration T2 of the next carrier cycle, the current sampling moment is shifted forward, and the duration of the forward shift is equal to the current sampling duration T s The time difference obtained by subtracting the second duration T2 of the next carrier cycle;

[0184] The second time duration T2 represents the time duration from the default current sampling moment to the X-phase lower bridge arm shut-off moment of the next carrier cycle.

[0185] Corresponding to the above method and system embodiments, an embodiment of the present invention further provides a motor control device and a computer-readable storage medium, which can be referred to in correspondence with the above.

[0186] See also Fig.10 As shown, the device may include:

[0187] Memory 301, used for storing computer programs;

[0188] The processor 302 is used to execute a computer program to implement the steps of the motor control device method in any of the above embodiments.

[0189] The computer readable storage medium stores a computer program, and when the computer program is executed by the processor, the steps of the motor control device method in any of the above embodiments are implemented. The computer readable storage medium mentioned here includes random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the technical field.

[0190] It should also be noted that, in this application, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0191] Those skilled in the art may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this application can be implemented with electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0192] The present application uses specific examples to illustrate the principles and implementation methods of the present invention, and the description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the present invention.

Claims

1. A motor control method, characterized in that: include: The three-phase current of the motor is obtained based on the target sampling method; Determining whether a preset switching condition is met; wherein the switching condition includes a switching condition related to the modulation ratio or operating frequency of the motor; If not, controlling the motor by space vector pulse width modulation based on the three-phase current; If yes, the motor is controlled by discontinuous modulation based on the three-phase current.

2. The motor control method according to claim 1, characterized in that: Determine whether the preset switching conditions are met, including: Determining whether the modulation ratio of the motor is higher than a preset modulation ratio threshold, or determining whether the operating frequency of the motor is higher than a preset rated frequency; If the modulation ratio of the motor is higher than a preset modulation ratio threshold, or the operating frequency of the motor is higher than a preset rated frequency, determining that the preset switching condition is met; If the modulation ratio of the motor is not higher than the modulation ratio threshold, or the operating frequency of the motor is not higher than the rated frequency, it is determined that the switching condition is not satisfied.

3. The motor control method according to claim 1, characterized in that: The switching condition is related to the dead time length T of the motor. d And the switching tube noise duration T n The relevant switching conditions, correspondingly, determine whether the preset switching conditions are met, including: Determine the dead time duration T of the motor d And the switching tube noise duration T n ; Determine the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle; wherein the first duration T1 represents the duration from the X-phase upper bridge arm shutdown moment to the default current sampling moment; the X-phase represents the phase with the shortest lower bridge arm conduction duration in the current carrier cycle; the default current sampling moment represents the carrier underflow moment of the current carrier cycle; If yes, it is determined that the preset switching condition is met; If not, it is determined that the switching condition is not satisfied.

4. The motor control method according to claim 1, characterized in that: The switching condition is related to the current sampling time T of the motor. s The relevant switching conditions, correspondingly, determine whether the preset switching conditions are met, including: Determine the current sampling time T of the motor s ; Determine the current sampling time T s Whether it is greater than the second time length T2 of the next carrier cycle; wherein the second time length T2 represents the time length from the default current sampling moment to the X-phase lower bridge arm shut-off moment of the next carrier cycle; If yes, it is determined that the preset switching condition is met; If not, it is determined that the switching condition is not satisfied.

5. The motor control method according to claim 1, characterized in that: The switching condition is related to the dead time length T of the motor. d , the switching tube noise duration T n And the current sampling time T s The relevant switching conditions, correspondingly, determine whether the preset switching conditions are met, including: Determine the dead time duration T of the motor d , the switching tube noise duration T n And the current sampling time T s ; Determine the dead time length T of the motor d , the switching tube noise duration T n And the current sampling time T s is greater than the sum of the first duration T1 of the current carrier cycle and the second duration T2 of the next carrier cycle; If yes, it is determined that the preset switching condition is met.

6. The motor control method according to any one of claims 1 to 5, characterized in that: After determining that the switching condition is met, the method further includes: Determine whether the preset sampling time shift condition is met; wherein the sampling time shift condition is the dead zone length T of the motor d , the switching tube noise duration T n And the current sampling time T s Related sampling instant shift conditions; If not, the motor is controlled by discontinuous modulation based on the three-phase current, and the current sampling moment used in the control process is a default current sampling moment; If yes, the motor is controlled by discontinuous modulation based on the three-phase current, and the current sampling time used in the control process is the shifted current sampling time, so that the current sampling time after the shift is not in the dead zone of the motor. d The motor switch noise duration T n The time from the current sampling time after the shift to the X-phase lower bridge arm shutdown time of the next carrier cycle is greater than the motor current sampling time T s .

7. The motor control method according to claim 6, characterized in that: Determine whether the preset sampling time shift condition is met, including: If the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle, or the current sampling duration T s , is greater than the second duration T2 of the next carrier cycle, it is determined that the sampling time shift condition is met, otherwise it is determined that the sampling time shift condition is not met; Accordingly, the rules for shifting the current sampling time specifically include: If the dead zone duration T d The switching tube noise duration T n is greater than the first duration T1 of the current carrier cycle, the current sampling moment is shifted backward, and the duration of the backward shift is equal to the dead zone duration T d The switching tube noise duration T n The time difference is obtained by subtracting the first duration T1 of the current carrier cycle from the sum of If the current sampling time T s , is greater than the second duration T2 of the next carrier cycle, the current sampling moment is shifted forward, and the duration of the forward shift is equal to the current sampling duration T s The time difference is obtained by subtracting the second duration T2 of the next carrier cycle.

8. A motor control system, characterized in that: include: A sampling module, used to obtain the three-phase current of the motor based on a target sampling method; A modulation mode switching judgment module, used to judge whether a preset switching condition is met; wherein the switching condition includes a switching condition related to the modulation ratio or operating frequency of the motor; If not, triggering a space vector pulse width modulation module, wherein the space vector pulse width modulation module is used to control the motor by means of space vector pulse width modulation based on the three-phase current; If yes, a discontinuous modulation module is triggered, and the discontinuous modulation module is used to control the motor by discontinuous modulation based on the three-phase current.

9. A motor control device, characterized in that: include: Memory for storing computer programs; A processor is used to execute the computer program to implement the steps of the motor control method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the motor control method according to any one of claims 1 to 7 are implemented.

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