An electric drive system phase current sensor fault diagnosis method and electric drive system

Abstract

The application provides a kind of electric drive system phase current sensor fault diagnosis method and electric drive system, it is related to motor control technical field, comprising: setting motor speed works in pre-set range, real-time three-phase current is acquired by current sensor;Real-time three-phase current is filtered, and the current amplitude and bias value of each phase current are calculated;Real-time three-phase current is calculated by discrete fourier transform, obtains the harmonic amplitude and phase of each phase current;Based on current amplitude, pairwise difference value is calculated, when the difference value calculated exceeds first threshold value, confirm the current sensor failure corresponding to another phase;When the absolute value of the bias value of any phase current exceeds second threshold value, and / or the harmonic amplitude of any phase current exceeds third threshold value, and / or the phase of any phase current exceeds fourth threshold value, then confirm the current sensor failure corresponding to phase;Solve the problem that safety hidden danger is caused by that electric drive system cannot diagnose current sensor failure in time in prior art.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a method for diagnosing faults in phase current sensors of an electric drive system and an electric drive system. Background Technology

[0002] Permanent magnet synchronous motor drive systems require current sensors to collect motor phase current feedback signals. During variable frequency speed regulation, current and speed information are needed for control. During operation, current sensors can be affected by factors such as current surges, leading to malfunctions. When a current sensor malfunctions, the feedback phase current signal becomes unbalanced or distorted, affecting the motor's torque and speed control functions. If the sensor malfunction goes undetected, the system controller and / or the propulsion motor itself may be damaged, and the system user may be in a dangerous situation. Therefore, a phase current sensor fault diagnosis method is needed. Summary of the Invention

[0003] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide a method for diagnosing phase current sensor faults in electric drive systems, thereby solving the problem of safety hazards caused by the inability to diagnose current sensor faults in electric drive systems in a timely manner.

[0004] This invention provides a method for fault diagnosis of phase current sensor in an electric drive system, comprising:

[0005] The motor speed of the electric drive system is set to operate within a preset range, and the real-time three-phase current is collected through a current sensor.

[0006] The real-time three-phase current is filtered, and the current amplitude and bias value of each phase current within the cycle are calculated.

[0007] The real-time three-phase current is subjected to discrete Fourier transform calculation to obtain the harmonic amplitude and phase of each phase current;

[0008] Based on the current amplitude of each phase current, the pairwise difference is calculated. When the calculated difference exceeds the first threshold, the current sensor of the corresponding other phase is confirmed to be faulty.

[0009] If the absolute value of the bias value of any phase current exceeds the second threshold, and / or the harmonic amplitude of any phase current exceeds the third threshold, and / or the phase of any phase current exceeds the fourth threshold, then the current sensor of the corresponding phase is confirmed to be faulty.

[0010] Preferably, the step of confirming a fault in the current sensor of the corresponding other phase when a calculated difference exceeds a first preset threshold includes:

[0011] If the difference in current amplitude between phase U and phase V exceeds the first threshold, the current sensor of phase W is determined to be faulty; if the difference in current amplitude between phase U and phase W exceeds the first threshold, the current sensor of phase V is determined to be faulty; if the difference in current amplitude between phase V and phase W exceeds the first threshold, the current sensor of phase U is determined to be faulty.

[0012] Preferably, after calculating the pairwise differences based on the current amplitudes of each phase current, the process includes:

[0013] If any calculated difference exceeds the first threshold, the current sensor is determined to be faulty.

[0014] Preferably, the filtering of the real-time three-phase current includes:

[0015] For any phase current, the phase current is subjected to an iterative first-order low-pass digital filter based on a preset filter coefficient.

[0016] Preferably, the step of performing discrete Fourier transform calculations on the real-time three-phase currents to obtain the harmonic amplitude and phase of each phase current includes:

[0017] The phase current is processed according to the preset Fourier transform formula to obtain the analog signal of each sampling point in the phase current, so as to obtain the harmonic amplitude and phase of the phase current through trigonometric transformation.

[0018] Preferably, it further includes: when a current sensor fault is determined in any phase, a current sensor sampling fault is reported;

[0019] Once it is determined that the current sensors of all phases are fault-free, the control module is used to perform offset correction on the real-time three-phase current.

[0020] The present invention also discloses an electric drive system, comprising:

[0021] The data acquisition module is used to set the motor speed of the electric drive system to operate within a preset range and to acquire real-time three-phase current through a current sensor.

[0022] The first calculation module is used to filter the real-time three-phase current and calculate the current amplitude and bias value of each phase current within the cycle.

[0023] The second calculation module is used to perform discrete Fourier transform calculations on the real-time three-phase current to obtain the harmonic amplitude and phase of each phase current.

[0024] The fault determination module is used to calculate the pairwise difference based on the current amplitude of each phase current. When the calculated difference exceeds the first threshold, the current sensor of the corresponding other phase is confirmed to be faulty. When the absolute value of the bias value of any phase current exceeds the second threshold, the current sensor of the corresponding phase is confirmed to be faulty. When the harmonic amplitude of any phase current exceeds the third threshold and / or the phase exceeds the fourth threshold, the current sensor of the corresponding phase is confirmed to be faulty.

[0025] Preferably, the fault determination module performs the following steps:

[0026] If the difference in current amplitude between phase U and phase V exceeds the first threshold, the current sensor of phase W is determined to be faulty; if the difference in current amplitude between phase U and phase W exceeds the first threshold, the current sensor of phase V is determined to be faulty; if the difference in current amplitude between phase V and phase W exceeds the first threshold, the current sensor of phase U is determined to be faulty.

[0027] Preferably, the fault determination module performs the following steps:

[0028] If any calculated difference exceeds the first threshold, the current sensor is determined to be faulty.

[0029] Preferably, it further includes:

[0030] The processing module is used to report a current sensor sampling fault when it is determined that the current sensor of any phase is faulty; and to use the control module to perform offset correction on the real-time three-phase current when it is determined that the current sensors of all phases are fault-free.

[0031] Compared with existing technologies, the above technical solution has the following advantages:

[0032] The present invention provides a method for diagnosing phase current sensors in an electric drive system. When the motor is operating within a preset speed range, the sensors collect the current of each phase. Then, the current amplitude and bias value are calculated after filtering the three-phase currents. Simultaneously, the harmonic amplitude and phase of each phase current are obtained through DFT calculation to confirm whether there is a fault in each phase current sensor. After confirming that a phase current sensor is faulty, the processing module can report it immediately so that the operator can handle it in time. This solves the problem of safety hazards caused by the inability to diagnose current sensor faults in electric drive systems in a timely manner in the prior art. Attached Figure Description

[0033] Figure 1 This is a flowchart of an embodiment of the fault diagnosis method for phase current sensor in an electric drive system according to the present invention;

[0034] Figure 2This is a flowchart illustrating the method for diagnosing phase current sensor faults in an electric drive system according to the present invention, as shown in Embodiment 1.

[0035] Figure 3 This is a schematic diagram of a module in a second embodiment of an electric drive system according to the present invention.

[0036] Figure label:

[0037] 6-Electric drive system; 61-Acquisition module; 62-First calculation module; 63-Second calculation module; 64-Fault determination module; 65-Processing module. Detailed Implementation

[0038] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0039] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0040] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0041] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0042] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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. Therefore, they should not be construed as limitations on this invention.

[0043] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0044] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0045] Example 1: This example provides a method for diagnosing faults in phase current sensors of an electric drive system. (See attached document.) Figure 1 ,include:

[0046] S100: Sets the motor speed of the electric drive system to operate within a preset range, and collects real-time three-phase current through a current sensor;

[0047] In this embodiment, when the fault diagnosis function is enabled and the motor speed threshold is kept within a certain threshold range (i.e., the current frequency is within a certain range), the pre-trigger condition for fault diagnosis in this application is to keep the output three-phase current relatively stable so that the current of each phase U, V and W can be collected by the current sensor.

[0048] S200: Filter the real-time three-phase current and calculate the current amplitude and bias value of each phase current within the cycle;

[0049] As a supplementary explanation, the current amplitude is the position of the deviation of the maximum and minimum current values ​​relative to the horizontal axis within a certain period, specifically = (MaxFlt - MinFlt) / 2, where MaxFlt is the maximum current value within a certain period, MinFlt is the minimum current value within a certain period, and the bias value is the difference between the maximum current value of one period and the maximum current value of the next period.

[0050] In the above steps, filtering the real-time three-phase current includes:

[0051] For any phase current, the phase current is subjected to an iterative first-order low-pass digital filter based on a preset filter coefficient.

[0052] Specifically, the first-order low-pass digital filter for the current signal is calculated using the following formula:

[0053] Y(n)=a*X(n)+(1-a)*Y(n-1) where X is the input and Y is the output value obtained after filtering. The current output result mainly depends on the previous filtered output value (i.e. Y(n-1)), where a is the filtering coefficient, which can be set as a calibrable parameter; it determines the weight of the new sampled value in the current filtering result.

[0054] S300: Perform discrete Fourier transform calculation on the real-time three-phase current to obtain the harmonic amplitude and phase of each phase current;

[0055] Specifically, Discrete Fourier Transform (DFT) calculation is a common method for calculating harmonic amplitude and phase. The step of performing DFT calculation on the real-time three-phase current to obtain the harmonic amplitude and phase of each phase current includes:

[0056] The phase current is processed according to the preset Fourier transform formula to obtain the analog signal of each sampling point in the phase current, so as to obtain the harmonic amplitude and phase of the phase current through trigonometric transformation.

[0057] In the above steps, the preset Fourier transform formula is set as follows:

[0058] Where k = 0, 1, 2, ..., N-1.

[0059] In the above, t is the time variable; k represents the index, the frequency index being tested; N represents the number of samples; the original definition of the three-phase current is Iu=Im*cos(ωt); Iv=Im*cos(ωt-2π / 3); Iw=Im*cos(ωt+2π / 3); where Im is the amplitude of the sampled input current and ω is the angular frequency of the input current.

[0060] Specifically, the step of calculating the harmonic amplitude and phase of the phase current through trigonometric transformation includes: multiplying the analog signal of each sampling point with a cosine function at a certain frequency of the phase current and then summing the results to obtain the cosine component at the corresponding frequency; multiplying the analog signal of each sampling point with a sine function at a certain frequency of the phase current and then summing the results to obtain the sine component at the corresponding frequency; and calculating the harmonic amplitude and phase based on the cosine and sine components at each frequency of the phase current.

[0061] Specifically, the steps of obtaining the harmonic amplitude and phase of the phase current through the Fourier transform and trigonometric transformation include: multiplying x(n) of each sampling point of the current signal by cos(2π*kn / N); k = 0; n = 0, 1, 2, ... N-1; adding all the above results together, which is the cosine component with k = 0; multiplying x(n) of each point of the signal by sin(2π*kn / N); k = 0; n = 0, 1, 2, ... N-1; adding all the above results together, which is the sine component with k = 0; repeating steps 1 to 4 continuously until k = N-1. Based on the above operations and mathematical transformation, the following expression can be obtained: X[k] = Xcos[k] + j*Xsin[k]; let A = Xcos[k]; B = Xsin[k]; at a frequency of k, the amplitude... That is, the above harmonic amplitude; the phase is Phase[k] = arctan(A / B).

[0062] S400: Calculate the pairwise difference based on the current amplitude of each phase current. If the calculated difference exceeds the first threshold, the current sensor of the corresponding other phase is confirmed to be faulty. If the absolute value of the bias value of any phase current exceeds the second threshold, and / or the harmonic amplitude of any phase current exceeds the third threshold, and / or the phase of any phase current exceeds the fourth threshold, the current sensor of the corresponding phase is confirmed to be faulty.

[0063] In this embodiment, the current amplitude of each phase is subtracted pairwise, and the difference is compared with a set first threshold. If the difference exceeds the first threshold, the amplitude over-limit fault flag is set to 1 (if it does not exceed the threshold, the amplitude over-limit fault flag is set to 0). Then, the obtained amplitude fault detection flag is logically judged (through three-way voting of the three-phase amplitude detection flags) to confirm which phase current sensor has a specific fault. At the same time, the absolute value of the obtained bias value is compared with a set threshold (second threshold) to determine whether there is a bias fault. The frequency of the largest harmonic amplitude of the three-phase current after DFT calculation (i.e., the above-mentioned harmonic amplitude) is compared with a third threshold, and the corresponding fundamental phase of the three-phase current is compared with a fourth threshold to check for faults and confirm whether there is a fault.

[0064] Specifically, the above-mentioned trigger amplitude over-limit fault flag position 1 (see...) Figure 2 This is manifested in the following way: after calculating the pairwise differences based on the current amplitudes of each phase current, the following is included: if any calculated difference exceeds a first threshold, then a current sensor fault is determined. That is, when the amplitude detection fault flag is triggered to position 1, it indicates that the current sensor is faulty, but at this time it is not certain which phase current sensor is faulty, which can be determined by three-way voting of the three-phase amplitude detection flag bits as described above.

[0065] The above-mentioned three-way voting through the three-phase amplitude detection flag bit, specifically, when a calculated difference exceeds a first preset threshold, confirming the current sensor fault of the corresponding other phase, includes: when the difference in current amplitude between phase U and phase V exceeds the first threshold, determining the current sensor fault of phase W; when the difference in current amplitude between phase U and phase W exceeds the first threshold, determining the current sensor fault of phase V; when the difference in current amplitude between phase V and phase W exceeds the first threshold, determining the current sensor fault of phase U.

[0066] In the above embodiment, after confirming whether the three-phase current sensors are faulty, the following step S500 is further included: when it is determined that the current sensor of any phase is faulty, the current sensor sampling fault is reported; when it is determined that the current sensors of all phases are fault-free, the real-time three-phase current is offset corrected using the control module.

[0067] As can be seen, if any current sensor malfunction is diagnosed as described above, the malfunction can be reported so that the operator can handle it immediately. If all current sensors are in normal condition, no action is required and the system can operate under normal conditions. The control module can use common correction methods to correct the offset of the real-time three-phase current, including but not limited to obtaining the correction value by looking up a table or using a preset function for real-time correction.

[0068] In the above steps, when the current amplitude is abnormal, the three-way voting of the three-phase amplitude detection flags allows determination of which phase current sensor is malfunctioning based on the current amplitude. Simultaneously, the calculated bias value, harmonic amplitude, and phase determine if other faults exist. This approach eliminates the need for complex mathematical calculations, enabling fault diagnosis of the current sensor with low software load, making it suitable for low-cost solutions. Furthermore, this implementation allows for phase current acquisition after the motor speed is within a preset range, enabling sensor fault diagnosis of the real-time operating electric drive system over a wider speed range.

[0069] Example 2: This example provides an electric drive system 6, see reference. Figure 3 ,include:

[0070] The acquisition module 61 is used to set the motor speed of the electric drive system to operate within a preset range and to acquire real-time three-phase current through a current sensor; specifically, it acquires the current of each of the U, V, and W phases.

[0071] The first calculation module 62 is used to filter the real-time three-phase current and calculate the current amplitude and bias value of each phase current within the cycle; specifically, a first-order low-pass digital filter is performed using preset filter coefficients.

[0072] The second calculation module 63 is used to perform discrete Fourier transform (DFT) calculation on the real-time three-phase current to obtain the harmonic amplitude and phase of each phase current.

[0073] The fault determination module 64 is used to perform pairwise difference calculations based on the current amplitude of each phase current. When the calculated difference exceeds a first threshold, the current sensor of the corresponding other phase is confirmed to be faulty. When the absolute value of the bias value of any phase current exceeds a second threshold, the current sensor of the corresponding phase is confirmed to be faulty. When the harmonic amplitude of any phase current exceeds a third threshold and / or the phase exceeds a fourth threshold, the current sensor of the corresponding phase is confirmed to be faulty.

[0074] Specifically, the fault determination module performs the following steps:

[0075] If any calculated difference exceeds the first threshold, the current sensor is determined to be faulty.

[0076] That is, when any difference exceeds the first threshold, the amplitude detection fault flag is triggered to 1, indicating that the current sensor is faulty. However, it is not clear which phase current sensor is faulty at this time. It can be determined by a three-way voting of the three-phase amplitude detection flag bits. The specific operation is as follows: the fault determination module performs the following steps:

[0077] If the difference in current amplitude between phase U and phase V exceeds the first threshold, the current sensor of phase W is determined to be faulty; if the difference in current amplitude between phase U and phase W exceeds the first threshold, the current sensor of phase V is determined to be faulty; if the difference in current amplitude between phase V and phase W exceeds the first threshold, the current sensor of phase U is determined to be faulty.

[0078] Specifically, it also includes:

[0079] The processing module 65 is used to report a current sensor sampling fault when it is determined that the current sensor of any phase is faulty; and to use the control module to perform offset correction on the real-time three-phase current when it is determined that the current sensors of all phases are fault-free.

[0080] In the above implementation, the acquisition module controls the sensors to acquire the current of each phase. Then, the first calculation module filters the three-phase current and calculates the current amplitude and bias value. At the same time, the second module calculates the harmonic amplitude and phase of each phase current through DFT. Based on the current amplitude and bias value, harmonic amplitude and phase obtained by the first and second calculation modules, the fault determination module compares them with preset thresholds (first threshold, second threshold, third threshold or fourth threshold) to confirm whether each phase current sensor is faulty. Specifically, this includes determining whether another phase current sensor is faulty by the difference between the current amplitudes of any two phases, and confirming whether the bias value of each phase exceeds the threshold to confirm whether a fault exists. Finally, after confirming that a phase current sensor is faulty, the processing module can report it immediately so that the operator can handle it in time. This solves the problem in the prior art that the current sensor fault cannot be diagnosed in time in the electric drive system, causing safety hazards, while the fault-free current sensor continues to be used in the electric drive system.

[0081] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for diagnosing faults in phase current sensors of an electric drive system, characterized in that, include: The motor speed of the electric drive system is set to operate within a preset range, and the real-time three-phase current is collected through a current sensor. The real-time three-phase current is filtered, and the current amplitude and bias value of each phase current within the cycle are calculated. The real-time three-phase current is subjected to discrete Fourier transform calculation to obtain the harmonic amplitude and phase of each phase current; Based on the current amplitude of each phase current, the pairwise difference is calculated. When one of the calculated differences exceeds the first threshold and the other difference does not exceed the first threshold, it is confirmed that the current sensor of the other phase corresponding to the two phase current sensors that did not exceed the first threshold is faulty. If the absolute value of the bias value of any phase current exceeds the second threshold, and / or the harmonic amplitude of any phase current exceeds the third threshold, and / or the phase of any phase current exceeds the fourth threshold, then the current sensor of the corresponding phase is confirmed to be faulty.

2. The fault diagnosis method according to claim 1, characterized in that, If one calculated difference exceeds a first threshold, and another difference does not exceed the first threshold, a fault is confirmed in the current sensor of the other phase corresponding to the two phase current sensors for which the calculated difference does not exceed the first threshold, including: If the difference in current amplitude between phase U and phase V does not exceed the first threshold, the current sensor of phase W is determined to be faulty. If the difference in current amplitude between phase U and phase W does not exceed the first threshold, the current sensor of phase V is determined to be faulty. If the difference in current amplitude between phase V and phase W does not exceed the first threshold, the current sensor of phase U is determined to be faulty.

3. The fault diagnosis method according to claim 1, characterized in that, After calculating the pairwise differences based on the current amplitudes of each phase current, the calculation includes: If any calculated difference exceeds the first threshold, the current sensor is determined to be faulty.

4. The fault diagnosis method according to claim 1, characterized in that, The filtering of the real-time three-phase current includes: For any phase current, the phase current is subjected to an iterative first-order low-pass digital filter based on a preset filter coefficient.

5. The fault diagnosis method according to claim 1, characterized in that, The step of performing discrete Fourier transform calculations on the real-time three-phase currents to obtain the harmonic amplitude and phase of each phase current includes: The phase current is processed according to the preset Fourier transform formula to obtain the analog signal of each sampling point in the phase current, so as to obtain the harmonic amplitude and phase of the phase current through trigonometric transformation.

6. The fault diagnosis method according to claim 1, characterized in that, Also includes: If a current sensor fault is detected in any phase, a current sensor sampling fault report is submitted. Once it is determined that all phase current sensors are fault-free, the control module is used to perform offset correction on the real-time three-phase current.

7. An electric drive system, characterized in that, include: The data acquisition module is used to set the motor speed of the electric drive system to operate within a preset range and to acquire real-time three-phase current through a current sensor. The first calculation module is used to filter the real-time three-phase current and calculate the current amplitude and bias value of each phase current within the cycle. The second calculation module is used to perform discrete Fourier transform calculations on the real-time three-phase current to obtain the harmonic amplitude and phase of each phase current. The fault determination module is used to calculate the pairwise difference based on the current amplitude of each phase current. When one of the calculated differences exceeds the first threshold and the other difference does not exceed the first threshold, the current sensor of the other phase corresponding to the two phase current sensors that did not exceed the first threshold is confirmed to be faulty. When the absolute value of the bias value of any phase current exceeds the second threshold, the current sensor of the corresponding phase is confirmed to be faulty. When the harmonic amplitude of any phase current exceeds the third threshold and / or the phase exceeds the fourth threshold, the current sensor of the corresponding phase is confirmed to be faulty.

8. The electric drive system according to claim 7, characterized in that, The fault determination module performs the following steps: If the difference in current amplitude between phase U and phase V does not exceed the first threshold, the current sensor of phase W is determined to be faulty. If the difference in current amplitude between phase U and phase W does not exceed the first threshold, the current sensor of phase V is determined to be faulty. If the difference in current amplitude between phase V and phase W does not exceed the first threshold, the current sensor of phase U is determined to be faulty.

9. The electric drive system according to claim 7, characterized in that, The fault determination module performs the following steps: If any calculated difference exceeds the first threshold, the current sensor is determined to be faulty.

10. The electric drive system according to claim 7, characterized in that, Also includes: The processing module is used to report a current sensor sampling fault when a current sensor fault is determined in any phase. Once it is determined that all phase current sensors are fault-free, the control module is used to perform offset correction on the real-time three-phase current.

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