Motor three-phase current polarity prediction method, electronic device, and machine-readable storage medium

Abstract

The application provides a motor three-phase current polarity prediction method, an electronic device and a machine readable storage medium, which defines two prediction boundaries that are opposite to each other near a theoretical zero point of a sine / cosine waveform current, and the two prediction boundaries cover a clamping wave band of the theoretical zero point; a detection value of the current is obtained every interval time t; in a stage from a positive half cycle to a negative half cycle, the current near the zero point is equivalent to a decreasing proportional function according to the detection value between the prediction boundary of the positive half cycle and the theoretical zero point, and the current zero point in the stage is predicted according to the decreasing proportional function; in a stage from the negative half cycle to the positive half cycle, the current is equivalent to an increasing proportional function according to the detection value between the prediction boundary of the negative half cycle and the theoretical zero point, and the current zero point in the stage is predicted according to the increasing proportional function. The application solves the problems of current sector judgment and compensation voltage error caused by frequent inversion of the current near the zero point and filtering delay.

Description

Technical Field

[0001] This invention relates to the field of three-phase motors, and more particularly to a method for predicting the polarity of three-phase current in a motor, an electronic device, and a machine-readable storage medium. Background Technology

[0002] Current polarity can be used in scenarios such as current sector determination and inverter dead-zone compensation. The accuracy of current polarity determination affects the dead-zone compensation value. However, due to the characteristics of the motor itself, the nonlinearity of the power devices and the motor's magnetic field, the three-phase current exhibits slight fluctuations under pulse width modulation (PWM) mode, especially near zero current. The current near zero will be clamped for a period of time, at the millisecond level. The clamping is constant for a period of time, but it will fluctuate near zero. For example, a current that changes sinusoidally will change very slowly near zero, deviating from the sinusoidal waveform.

[0003] In existing technologies, one way to determine the polarity of current is to directly determine it using current information detected by a sensor. However, since the sensor acquires data in fluctuating conditions and has a certain level of accuracy, there is a certain deviation in the data acquired near zero. For example, when the sensor's accuracy is 2%, the range of 0.01 to -0.01 exceeds the sensor's resolution, but the actual current sign is already reversed. This causes the system to fill in an incorrect compensation voltage value, reducing the system's reliability. Furthermore, the frequent reversals of the current near zero and the high-frequency oscillation of the current polarity further affect the system's reliability.

[0004] Another way to determine the polarity of the current is to perform filtering to filter the current fluctuations near the zero point. The essence of filtering is delay processing, and the data obtained by filtering is also delayed, causing phase delay of the three-phase current. Dead zone compensation needs to be based on the current polarity to compensate the voltage. Different current polarities require different compensation voltages, and phase delay will lead to the filling of incorrect compensation voltage.

[0005] Therefore, it is necessary to propose a method and product that can more accurately determine the polarity of current. Summary of the Invention

[0006] This invention provides a method for predicting the polarity of three-phase current in a motor, an electronic device, and a machine-readable storage medium to solve the problems of frequent reversals of current near zero point, high-frequency oscillation of current polarity exceeding the resolution of the sensor, leading to incorrect filling of compensation voltage values, and to solve the problem of phase delay near the zero point of the current caused by filtering processing, resulting in incorrect filling of compensation voltage values.

[0007] This invention provides a method for predicting the polarity of three-phase current in a motor, comprising the following steps:

[0008] S10. Define a prediction boundary near the theoretical zero point of the current in the sine / cosine waveform. The two prediction boundaries corresponding to the same theoretical zero point are opposite numbers to each other, and the two prediction boundaries cover the clamping band of the theoretical zero point.

[0009] S20. Acquire the current detection value at each time interval t;

[0010] S30. When the current changes from the positive half-cycle to the negative half-cycle, based on the limiting principle of sine and cosine waves near the zero point, and according to the detection value between the predicted boundary of the positive half-cycle and the theoretical zero point, the sine / cosine wave near the zero point is equivalent to a decreasing proportional function, and the current zero point of this stage is predicted according to the decreasing proportional function.

[0011] From the negative half-cycle to the positive half-cycle, based on the limiting principle of sine and cosine waves near zero, and according to the detected value between the predicted boundary of the negative half-cycle and the theoretical zero point, the current is equivalent to an increasing proportional function, and the zero point of the current in this stage is predicted based on the increasing proportional function.

[0012] Optionally, in step S10, the prediction boundary is set based on the variation range of the current in each phase, clamping information, and the real-time waveform of the current.

[0013] Optionally, in step S20, t is in the microsecond range.

[0014] Optionally, in step S30, during the phase from the positive half-cycle to the negative half-cycle, the polarity of the current is determined by the predicted value of the decreasing proportional function between the two predicted boundaries corresponding to the theoretical zero point, and the polarity of the current is determined by the detection value for the remaining part.

[0015] During the transition from the negative half-cycle to the positive half-cycle, the polarity of the current is determined by the predicted value of the incremental proportional function between the two predicted boundaries corresponding to the theoretical zero point, and by the detected value for the remaining portion.

[0016] Optionally, step S30 specifically includes the following steps:

[0017] S31. If the current is in the positive half-cycle of a sine / cosine wave, proceed to steps S32 to S33; otherwise, proceed to steps S34 to S35.

[0018] S32. Obtain the time T1 between the two prediction boundaries of the same group, where the current TBD1 and current TBD2 are both in the positive half-cycle; the decreasing proportional function is:

[0019]

[0020] Among them, I mThe current is the predicted value, and m represents the number of times the detection value is obtained after passing TBD2, with the m value corresponding to TBD2 being 0;

[0021] S33, Judgment I m If the current is less than -TBD1, then the detected value is used to determine the current polarity, and steps S34 to S35 are executed; otherwise, I is used. m Determine the polarity of the current and repeat step S33;

[0022] S34. Obtain the time T2 between the two prediction boundaries in the same set of conditions, where the current TBD3 and current TBD4 are both in the negative period; the incremental proportional function is:

[0023]

[0024] Among them, I n The current is the predicted value, and n represents the number of times the detection value is obtained after passing TBD4, with n being 0 for TBD4.

[0025] S35, Judgment I n If the current is greater than -TBD4, then the detected value is used to determine the current polarity, and steps S32 to S33 are executed; otherwise, I is used. n Determine the polarity of the current and repeat step S35.

[0026] Optionally, current TBD1 and current -TBD1 are the prediction boundaries for the positive half-cycle to negative half-cycle phase, and current TBD3 and -TBD3 are the prediction boundaries for the negative half-cycle to positive half-cycle phase.

[0027] Optionally, current TBD1 and current -TBD1 are in the two prediction boundary periods of the positive half-cycle to the negative half-cycle phase, and current TBD3 and current -TBD3 are in the two prediction boundary periods of the negative half-cycle to the positive half-cycle phase.

[0028] Optionally, the current variation is between 300A and -300A, with TBD1 at 5A, TBD2 at 2A, TBD3 at -5A, TBD4 at -2A, and t at 100 microseconds.

[0029] The present invention also provides an electronic device, including a processor and a memory, wherein the memory stores a program that can be called by the processor, wherein when the processor executes the program, it implements the motor three-phase current polarity prediction method as described in any of the preceding claims.

[0030] The present invention also provides a machine-readable storage medium having a program stored thereon, which, when executed, implements the motor three-phase current polarity prediction method as described above.

[0031] Beneficial effects:

[0032] In this invention, based on the mathematical limit principle of sine and cosine waves near zero, the rate of change of current is used to predict the polarity of the current. According to the calculation of the derivatives of sine and cosine, the three-phase current has monotonicity near zero. Using this monotonicity, the waveforms of sine and cosine are equivalent to monotonicity based on the detected values. The slope is used to predict and determine the polarity of the current at the next moment and predict its magnitude. Thus, the zero point of the current can be predicted, rather than relying solely on the fuzzy values ​​collected by the sensor in real time.

[0033] Although the method of this invention has some current value distortion when adapting to current clamping phenomena, it has no impact on determining the polarity of the current. When performing current loop control, the original acquired current can still be used, that is, current loop control is performed based on the detected value. However, when judging the current sector or dead zone compensation voltage, this method is used to predict the current zero point, which solves the problems of current sector judgment and compensation voltage error caused by frequent current reversal near the zero point and filtering delay. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of a method for predicting the polarity of three-phase current in a motor according to an embodiment of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be understood that the terms "upper," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0038] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0039] In the description of this invention, "a plurality of" means multiple, such as two, three, four, etc., unless otherwise explicitly specified.

[0040] In the description of this invention, unless otherwise explicitly specified and limited, the term "connection" and other such terms should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0042] Please refer to Figure 1 Understood. This invention provides a method for determining the polarity of three-phase current in a motor, used to identify the polarity of the sine and cosine waveforms of the three-phase current at zero-crossing points. This method can be programmed into a chip. The method obtains the polarity of each phase current by accurately detecting the zero point of each phase current.

[0043] The method includes the following steps:

[0044] S10. Define prediction boundaries near the theoretical zero point of the current in the sine / cosine waveform. The two prediction boundaries corresponding to the same theoretical zero point are opposites of each other, and the clamping effect is located between each set of prediction boundaries. In other words, each theoretical zero point corresponds to two prediction boundaries, which are distributed in the positive half-cycle and the negative half-cycle, respectively. The "sine / cosine waveform" involved in this invention is understood as a sine waveform or a cosine waveform. The prediction boundaries can be pre-stored in the chip or automatically set according to the information obtained when this method is running.

[0045] S20. The current detection value is acquired at intervals t. In specific applications, the current can be detected by a sensor, and the chip reads the sensor's detection result to obtain the detection value; t is in the microsecond range.

[0046] S30. Based on the detected values, the sine or cosine waveform during each prediction boundary period is equivalent to a proportional function, specifically:

[0047] From the positive half-cycle to the negative half-cycle, based on the limiting principle of sine and cosine waves near zero, and according to the detection value between the predicted boundary of the positive half-cycle and the theoretical zero point, the sine / cosine waveform near zero point is equivalent to a decreasing proportional function, and the current zero point in this stage is predicted based on the decreasing proportional function.

[0048] From the negative half-cycle to the positive half-cycle, based on the limiting principle of sine and cosine waves near zero, and according to the detected value between the predicted boundary of the negative half-cycle and the theoretical zero point, the current is equivalent to an increasing proportional function, and the zero point of the current in this stage is predicted based on the increasing proportional function.

[0049] In this invention, based on the mathematical limit principle of sine and cosine waves near zero:

[0050]

[0051] Near the zero point, trigonometric functions can be equivalent to proportional functions. Therefore, the rate of change of current can be used to predict the polarity of the current. According to the derivatives of sine and cosine, the three-phase current has monotonicity near the zero point. Using this monotonicity, the waveform of sine and cosine can be equivalent to monotonicity based on the detected value. The slope can be used to predict the polarity and magnitude of the current at the next moment, thus predicting the current zero point, instead of relying solely on the fuzzy judgment based on the real-time values ​​collected by the sensor. Although the method of this invention has some current value distortion due to the current clamping phenomenon, it has no impact on the determination of current polarity. When performing current loop control, the original collected current can still be used, that is, current loop control can be performed based on the detected value. However, when judging the current sector or dead zone compensation voltage, this method is used to predict the current zero point, which solves the problems of current sector judgment and compensation voltage error caused by frequent current reversal and filtering delay near the zero point.

[0052] In step S10, the prediction boundary is set based on the variation range of the current in each phase, clamping information, and the real-time waveform of the current. The prediction boundary corresponding to the current variation range of 300A to -300A is different from that of 20A to -20A; obviously, the absolute value of the prediction boundary for the latter is smaller. The current waveform reflects its frequency and amplitude; if these two parameters are different, the prediction boundary will adaptively change.

[0053] In step S30 of this embodiment, during the current transition from the positive half-cycle to the negative half-cycle, the polarity of the current between the two predicted boundaries corresponding to the theoretical zero point is determined using the predicted value of a decreasing proportional function, while the polarity of the current in the remaining portion is determined using the detected value. Similarly, during the current transition from the negative half-cycle to the positive half-cycle, the polarity of the current between the two predicted boundaries corresponding to the theoretical zero point is determined using the predicted value of the equivalent proportional function, while the polarity of the current in the remaining portion is determined using the actual detected value. In other words, not only is the current zero point predicted using the equivalent proportional function, but the polarity of the current between the same set of predicted boundaries is determined using the predicted value of the equivalent proportional function, while the polarity of the current in the remaining portion is determined using the actual detected value.

[0054] Step S30 specifically includes the following steps:

[0055] S31. If the current is in the positive half-cycle of a sine / cosine wave, proceed to steps S32 to S33; otherwise, proceed to steps S34 to S35.

[0056] S32. Within the prediction boundary, obtain the time T1 elapsed for each phase current to change from TBD1 to TBD2. Both TBD1 and TBD2 are in the positive half-cycle and are both positive numbers. TBD1 and TBD2 are selected according to the degree of distortion, and their values ​​are pre-stored in the chip. The detected value in step S20 is compared with the pre-stored value to capture the two values ​​and their corresponding time information. The time T1 is calculated, and the decreasing ratio function is:

[0057]

[0058] Among them, I m Let m be the predicted value of the current, and m represent the number of times the detection value is obtained after passing TBD2. The value of m corresponding to TBD2 is 0, and m is a positive integer. Substituting m into the value of m yields the predicted value I. m m can be represented by the chip's clock.

[0059] S33, Judgment I m If the current is less than -TBD1, then the detected value is used as the current value, and steps S34 to S35 are executed; otherwise, I is... m As the current value, step S33 is repeated; where I m If the value is less than -TBD1, it is considered that the prediction boundary of the negative half-cycle has been crossed. At this point, the clamping band has been crossed, and the current can be used as the actual detected value.

[0060] S34. Within the prediction boundary, obtain the time T2 elapsed for each phase current to change from TBD3 to TBD4. Both TBD3 and TBD4 are within positive and negative cycles, and are both negative. TBD3 and TBD4 are selected according to the degree of distortion. Their values ​​are pre-stored in the chip. The detected value in step S20 is compared with the pre-stored value to capture the two values ​​and their corresponding time information, and the time T2 is calculated. The incrementing ratio function is:

[0061]

[0062] Among them, I n Let I be the predicted current value, and n represent the number of times the detection value is obtained after passing TBD4. The value of n corresponding to TBD4 is 0, and n is a positive integer. Substituting n into the value yields the predicted value I. n n can be represented by the chip's clock.

[0063] S35, Judgment I n If the value is greater than -TBD4, then the detected value is used as the current value, and steps S32 to S33 are executed; otherwise, I is... n As the current value, step S35 is repeated; where I n When the value is greater than -TBD4, it is considered that the prediction boundary of the positive half-cycle has been exceeded. At this point, the clamping band has been exceeded, and the actual detected value of the current can be used.

[0064] In this embodiment, current TBD1 and current -TBD1 are the prediction boundaries for the positive half-cycle to negative half-cycle phase, and current TBD3 and -TBD3 are the prediction boundaries for the negative half-cycle to positive half-cycle phase. In other embodiments, current TBD1 and -TBD1 are within the two prediction boundary periods of the positive half-cycle to negative half-cycle phase, and current TBD3 and -TBD3 are within the two prediction boundary periods of the negative half-cycle to positive half-cycle phase.

[0065] In this embodiment, the current variation is between 300A and -300A, TBD1 is 5A, TBD2 is 2A, TBD3 is -5A, TBD4 is -2A, and t is 100 microseconds.

[0066] This invention provides an electronic device, including a processor and a memory. The memory stores a program that can be called by the processor. When the processor executes the program, it implements the motor three-phase current polarity prediction method as described in any of the above embodiments.

[0067] This invention provides a machine-readable storage medium storing a program that, when executed, implements the motor three-phase current polarity prediction method as described in any of the above embodiments.

[0068] In the description of this specification, references to terms such as "an embodiment," "an example," and "a specific implementation process" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of predicting the polarity of three-phase currents of an electric machine, characterized in that, The method comprises the following steps: S10, defining a prediction boundary near a theoretical zero point of a sinusoidal / cosine wave current, two prediction boundaries corresponding to the same theoretical zero point being opposite numbers, and the two prediction boundaries covering a clamping wave band of the theoretical zero point; S20, acquiring a detection value of the current every interval time t; S30, during a positive half cycle to negative half cycle stage of the current, according to a limit principle of the sinusoidal and cosine waves near the zero point, and according to the detection value between the prediction boundary and the theoretical zero point of the positive half cycle, the sinusoidal / cosine wave near the zero point is equivalent to a decreasing proportional function, the decreasing proportional function being: Wherein, T1 is used to represent the time that each phase current changes from TBD1 to TBD2, the current TBD1 and the current TBD2 are both located in the positive half cycle, I m is the predicted value of the current, m represents the number of times that the detection value is obtained after passing TBD2, and the m value corresponding to TBD2 is 0; According to the decreasing proportional function, the current zero point of the stage is predicted, and between the two prediction boundaries corresponding to the theoretical zero point, the prediction value of the decreasing proportional function is used to judge the current polarity, and the rest is used to judge the current polarity by using the detection value; During a negative half cycle to positive half cycle stage of the current, according to a limit principle of the sinusoidal and cosine waves near the zero point, and according to the detection value between the prediction boundary and the theoretical zero point of the negative half cycle, the current is equivalent to an increasing proportional function, the increasing proportional function being: Wherein, T2 is used to represent the time that each phase current changes from TBD3 to TBD4, the current TBD3 and the current TBD4 are both located in the negative period, I n is the predicted value of the current, n represents the number of times that the detection value is obtained after passing through TBD4, and the n value corresponding to TBD4 is 0; According to the increasing proportional function, the current zero point of the stage is predicted, and between the two prediction boundaries corresponding to the theoretical zero point, the prediction value of the increasing proportional function is used to judge the current polarity, and the rest is used to judge the current polarity by using the detection value.

2. The motor three-phase current polarity prediction method of claim 1, wherein, In step S10, the prediction boundary is set according to the variation range of each phase current, clamping information and real-time waveforms of the current.

3. The motor three-phase current polarity prediction method of claim 1, wherein, In step S20, t is microsecond level.

4. The motor three-phase current polarity prediction method of claim 1, wherein, Step S30 specifically comprises the following steps: S31, judging whether the current is in a positive half cycle of a sinusoidal / cosine wave, if yes, steps S32 to S33 are executed, otherwise, steps S34 to S35 are executed; S32, acquiring a time T1 during which the current varies from TBD1 to TBD2 between the two prediction boundaries of the same group; S33, judging I m whether it is less than -TBD1, if yes, judging current polarity by using the detected value, and executing steps S34 to S35, if no, judging current polarity by using I m and repeating step S33; S34, acquiring a time T2 during which the current varies from TBD3 to TBD4 between the two prediction boundaries of the same group; S35, judging I n whether it is greater than -TBD4, if yes, judging current polarity by using the detected value, and executing steps S32 to S33, if no, judging current polarity by using I n and repeating step S35.

5. The motor three-phase current polarity prediction method of claim 4, wherein, The current TBD1 and the current-TBD1 are the prediction boundaries of the positive half cycle to negative half cycle stage, and the current TBD3 and the current-TBD3 are the prediction boundaries of the negative half cycle to positive half cycle stage.

6. The motor three-phase current polarity prediction method of claim 4, wherein, The current TBD1 and the current-TBD1 are in the two prediction boundaries during the positive half cycle to negative half cycle stage, and the current TBD3 and the current-TBD3 are in the two prediction boundaries during the negative half cycle to positive half cycle stage.

7. A method of predicting the polarity of three-phase currents of an electrical machine according to any one of claims 4-6, characterized in that, The current varies between 300A to-300A, TBD1 is 5A, TBD2 is 2A, TBD3 is-5A, and TBD4 is-2A, and t is 100 microseconds.

8. An electronic device, comprising: The method comprises a processor and a memory, the memory storing a program which can be called by the processor, wherein when the processor executes the program, the motor three-phase current polarity prediction method of any one of claims 1-7 is realized.

9. A machine-readable storage medium having stored thereon a program, characterized in that The program is executed to realize the motor three-phase current polarity prediction method of any one of claims 1-7.

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