A method and related equipment for detecting short-circuit faults in a permanent magnet traction system

Abstract

This invention provides a short-circuit fault detection method and related equipment for a permanent magnet traction system. The method includes: Step 1, acquiring electrical signals from the inverter output side and decomposing the signals to obtain positive-sequence and negative-sequence electrical signals; Step 2, calculating the detection value for short-circuit fault detection; Step 3, obtaining the original short-circuit fault detection result based on the difference between the initial detection threshold and the detection value; Step 4, if the original short-circuit fault detection result indicates a short-circuit fault, controlling the three-level isolation controller to close and returning to the above steps; if the new short-circuit fault detection result is the same as the original short-circuit fault detection result, then the original short-circuit fault detection result is determined as the final short-circuit fault detection result; otherwise, updating the initial detection threshold according to a preset step, using the intermediate detection threshold as the initial detection threshold in Step 3, and returning to Step 3. This invention can improve the accuracy of short-circuit fault detection.

Description

Technical Field

[0001] This invention designs a permanent magnet motor traction system, specifically involving a short-circuit fault detection method and related equipment for a permanent magnet traction system. Background Technology

[0002] As a crucial component of the traction drive system in rail transit vehicles, the traction motor directly impacts the traction performance, acceleration, and operational capabilities of the trainset, and is also a vital factor in ensuring its safe operation. Permanent magnet synchronous traction motors, compared to asynchronous traction motors, offer advantages such as high efficiency, energy saving, high power density, and a high power factor. Their application in the domestic and international rail transit industry has gradually expanded from the subway sector to the high-speed train sector.

[0003] There are numerous methods for detecting short-circuit faults in traction motors, mainly including methods based on electrical signal analysis (current and voltage signal analysis), model-based methods (state observer method, parameter identification method), artificial intelligence-based methods (neural network method, support vector machine method, fuzzy logic method, etc.), and methods based on other physical quantities (vibration signal analysis method, temperature monitoring method). Currently, the rail transit industry mostly uses the results of current signal analysis to achieve online detection of inter-turn short-circuit faults in traction motors. The detection principle is that when an inter-turn short circuit occurs in the traction motor, the symmetry of the three-phase current is disrupted, generating a negative sequence current component. By detecting and analyzing the magnitude of the negative sequence current, it can be determined whether an inter-turn short-circuit fault exists in the motor.

[0004] However, traditional methods rely solely on fixed threshold values ​​to determine inter-turn short-circuit faults, which has limitations. In actual operation, the thresholds cannot be updated and corrected in real time, affecting the accuracy of short-circuit fault detection. Furthermore, the influence of the inverter itself on fault diagnosis (such as reverse power effects and current waveform distortion) is not considered, which can easily lead to misjudgments and reduce the accuracy of short-circuit fault detection. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a short-circuit fault detection method and related equipment for a permanent magnet traction system, so as to improve the accuracy of short-circuit fault detection.

[0006] In a first aspect, the present invention provides a short-circuit fault detection method for a permanent magnet traction system. The permanent magnet traction system includes a permanent magnet synchronous motor and an inverter connected to the permanent magnet synchronous motor in three phases. A three-level isolation controller is connected between the permanent magnet synchronous motor and the inverter. The method includes the following steps:

[0007] Step 1: Acquire the electrical signal from the inverter output side and decompose the electrical signal to obtain the positive sequence electrical signal and the negative sequence electrical signal; the electrical signal is a three-phase current signal or a three-phase voltage signal.

[0008] Step 2: Calculate the detection value used for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal;

[0009] Step 3: Obtain the original short-circuit fault detection result based on the difference between the initial detection threshold and the detected value; the initial detection threshold is determined by the positive sequence electrical signal and negative sequence electrical signal of the permanent magnet traction system under normal operating conditions, and the original short-circuit fault detection result is either a short-circuit fault has occurred or no short-circuit fault has occurred.

[0010] Step 4: If the original short-circuit fault detection result indicates a short-circuit fault has occurred, control the three-level isolation controller to close, return to steps 1 to 3, and obtain a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, then the original short-circuit fault detection result is determined as the final short-circuit fault detection result; otherwise, update the initial detection threshold according to the preset step to obtain an intermediate detection threshold, and use the intermediate detection threshold as the initial detection threshold in step 3, then return to step 3.

[0011] Optionally, the electrical signal can be decomposed to obtain positive-sequence and negative-sequence electrical signals, including:

[0012] When the electrical signal is a three-phase current signal, it is calculated using the formula.

[0013]

[0014] in, Indicates a positive sequence current signal. This represents the U-phase output current of the inverter, where α represents the U-phase current, and α = e j120 =e -j240 , This indicates the V-phase output current of the inverter. Indicates the inverter output phase W current, α 2 =e j240 =e -j120 , This represents the negative sequence current signal, and a, b, and c represent the three phases U, V, and W on the inverter output side.

[0015] When the electrical signal is a three-phase voltage signal, it is calculated using the formula.

[0016]

[0017] in, This indicates a positive sequence voltage signal. This indicates the inverter output UV line voltage. This indicates the inverter output line voltage VW. This indicates the inverter's output UW line voltage.

[0018] Optionally, based on the positive-sequence and negative-sequence electrical signals, the detection values ​​used for short-circuit fault detection are calculated, including:

[0019] When the electrical signal is a three-phase current signal, it is calculated using the formula.

[0020]

[0021] or

[0022]

[0023] or

[0024]

[0025] The detection value J was obtained. K Where F(·) represents the negative sequence current threshold that is linearly related to the rotational speed, and V represents the rotational speed of the permanent magnet synchronous motor.

[0026] When the electrical signal is a three-phase voltage signal, it is calculated using the formula.

[0027]

[0028] or

[0029]

[0030] or

[0031]

[0032] The detection value J was obtained. K .

[0033] Optionally, the initial detection threshold is calculated in the same way as the detection value, using the positive and negative sequence electrical signals of the permanent magnet traction system under normal operating conditions.

[0034] Optionally, the original short-circuit fault detection result is obtained based on the difference between the initial detection threshold and the detected value, including:

[0035] If the difference is greater than zero, the original short-circuit fault detection result is determined to be a short-circuit fault; otherwise, the original short-circuit fault detection result is determined to be no short-circuit fault.

[0036] Optionally, the initial detection threshold is updated according to a preset step to obtain an intermediate detection threshold, including:

[0037] Through calculation formula

[0038]

[0039] Obtain the intermediate detection threshold in, This indicates the initial detection threshold.

[0040] Optionally, before decomposing the electrical signal, the short-circuit fault detection method may also include:

[0041] For any two phases of the electrical signal, calculate the theoretical value of the third phase based on those two phases;

[0042] If the error between the theoretical value of the third-phase electrical signal and the actual value of the acquired third-phase electrical signal is greater than the preset threshold, the third-phase electrical signal will be reacquired until the error is less than or equal to the preset threshold.

[0043] Secondly, the present invention provides a short-circuit fault detection device for a permanent magnet traction system, comprising:

[0044] The feature extraction module is used to collect electrical signals from the inverter output side and decompose the electrical signals to obtain positive-sequence and negative-sequence electrical signals; the electrical signals are three-phase current signals or three-phase voltage signals.

[0045] The detection calculation module is used to calculate the detection value for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal.

[0046] The preliminary detection module is used to obtain the original short-circuit fault detection result based on the difference between the initial detection threshold and the detected value. The initial detection threshold is determined by the positive sequence electrical signal and the negative sequence electrical signal of the permanent magnet traction system under normal operating conditions. The original short-circuit fault detection result is whether a short-circuit fault has occurred or not.

[0047] The re-detection module is used to control the three-level isolation controller to close if the original short-circuit fault detection result indicates that a short-circuit fault has occurred. It then returns to the feature extraction module and proceeds to the preliminary detection module to obtain a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, the original short-circuit fault detection result is determined as the final short-circuit fault detection result. Otherwise, the initial detection threshold is updated according to a preset step to obtain an intermediate detection threshold. This intermediate detection threshold is then used as the initial detection threshold in the preliminary detection module, and the process returns to the preliminary detection module.

[0048] Thirdly, the present invention provides a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described method.

[0049] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0050] The beneficial effects of this invention are:

[0051] The short-circuit fault detection method provided by this invention, when the original short-circuit fault detection result indicates a short-circuit fault, controls the three-level isolation controller to close, disconnects the inverter, re-acquires and detects electrical signals, and obtains a new short-circuit fault detection result. Only when the original short-circuit fault detection result and the new short-circuit fault detection result are the same, is the original short-circuit fault detection result determined as the final short-circuit fault detection result. This effectively avoids the interference of the inverter on short-circuit fault detection and improves the accuracy of short-circuit fault detection. When the original short-circuit fault detection result and the new short-circuit fault detection result are different, the initial detection threshold can be updated. Real-time updating and correction of the threshold is beneficial to improving the accuracy of short-circuit fault detection. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the permanent magnet traction system in one embodiment of this application;

[0053] Figure 2 This is a flowchart of a short-circuit fault detection method in one embodiment of this application;

[0054] Figure 3 This is a schematic diagram of the structure of a short-circuit fault detection device in one embodiment of this application;

[0055] Figure 4 This is a schematic diagram of the structure of a terminal device in one embodiment of this application. Detailed Implementation

[0056] To address the low accuracy of traditional short-circuit fault detection methods, this invention provides a short-circuit fault detection method and related equipment for a permanent magnet traction system. When the initial short-circuit fault detection result indicates a short circuit, the method controls the three-level isolation controller to close, disconnecting the inverter, and re-acquiring and detecting the electrical signal to obtain a new short-circuit fault detection result. Only when the initial and new short-circuit fault detection results are identical is the initial result determined as the final short-circuit fault detection result. This effectively avoids inverter interference in short-circuit fault detection and improves accuracy. Furthermore, when the initial and new short-circuit fault detection results differ, the initial detection threshold can be updated. Real-time updating and correction of the threshold further enhances the accuracy of short-circuit fault detection.

[0057] For ease of understanding, the structural principle of the permanent magnet traction system in the embodiments of the present invention will be explained below.

[0058] like Figure 1As shown, the permanent magnet traction system includes a permanent magnet synchronous motor 101 and an inverter 102 connected to the permanent magnet synchronous motor 101 in three phases. A three-level isolation controller 103 is connected between the permanent magnet synchronous motor 101 and the inverter 102.

[0059] The permanent magnet synchronous motor 101, used as a drive motor to drive electric vehicles or rail transit, employs permanent magnets to generate a magnetic field, thus eliminating the need for current-excited windings. The main components of the permanent magnet synchronous motor 101 include a stator, a rotor, and bearings.

[0060] Inverter 102 is a key device connecting permanent magnet synchronous motor 101 to the power supply. It is responsible for converting DC or AC power into three-phase AC power suitable for the operation of permanent magnet synchronous motor 101, and controlling the motor's speed, torque and other operating parameters.

[0061] The three-level isolation controller 103 is used to ensure electrical isolation, protection and control between the permanent magnet synchronous motor 101 and the inverter 102, in order to ensure the safety and reliability of the motor drive system.

[0062] The short-circuit fault detection method provided by the present invention will be described below.

[0063] like Figure 2 As shown, the short-circuit fault detection method includes steps 1 to 4.

[0064] Step 1: Collect the electrical signal from the inverter output side and decompose the electrical signal to obtain the positive sequence electrical signal and the negative sequence electrical signal.

[0065] In embodiments of the present invention, the aforementioned electrical signal is a three-phase current signal or a three-phase voltage signal. Correspondingly, the aforementioned electrical signal can be acquired by a current sensor or a voltage sensor.

[0066] To avoid detection errors caused by abnormal sampling of a single sensor signal, the short-circuit fault detection method provided by this invention will also verify the collected electrical signal before decomposing the electrical signal. The verification process includes steps I to II.

[0067] Step I: For any two phases of the electrical signal, calculate the theoretical value of the third phase signal based on those two phases.

[0068] For example, let the theoretical values ​​of the electrical signals be a(t), b(t), and c(t), and the phase difference between each phase of the electrical signals be 120 degrees. Then the theoretical values ​​of each phase of the electrical signals are a(t) = A cos(ωt), b(t) = A cos(ωt-120°), and c(t) = A cos(ωt+120°).

[0069] Step II: If the error between the theoretical value of the third-phase electrical signal and the actual value of the acquired third-phase electrical signal is greater than the preset threshold, then the third-phase electrical signal is reacquired until the error is less than or equal to the preset threshold.

[0070] If the error exceeds a preset threshold (e.g., 0.05), it indicates that the sensor collecting the third-phase electrical signal is malfunctioning and the third-phase electrical signal needs to be collected again. If the error continues to exceed the preset threshold multiple times, a new sensor should be used to collect the third-phase electrical signal.

[0071] The process of decomposing the electrical signal to obtain positive-sequence and negative-sequence electrical signals will be explained below.

[0072] Depending on the type of electrical signal collected, it is divided into Case A and Case B.

[0073] Case A: When the electrical signal is a three-phase current signal, it can be calculated using the formula...

[0074]

[0075] in, Indicates a positive sequence current signal. This represents the U-phase output current of the inverter, where α represents the U-phase current, and α = e j120 =e -j240 , This indicates the V-phase output current of the inverter. Indicates the inverter output phase W current, α 2 =e j240 =e -j120 , This represents the negative sequence current signal, and a, b, and c represent the three phases U, V, and W on the inverter output side.

[0076] Case B, when the electrical signal is a three-phase voltage signal, is calculated using the formula...

[0077]

[0078] in, This indicates a positive sequence voltage signal. This indicates the inverter output UV line voltage. This indicates the inverter output line voltage VW. This indicates the inverter's output UW line voltage.

[0079] Step 2: Calculate the detection value used for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal.

[0080] Specifically, for case A, the calculation formula is used.

[0081]

[0082] or

[0083]

[0084] or

[0085]

[0086] The detection value J was obtained. K Where F(·) represents the negative sequence current threshold that is linearly related to the rotational speed, and V represents the rotational speed of the permanent magnet synchronous motor.

[0087] For case B, the calculation formula is used.

[0088]

[0089] or

[0090]

[0091] or

[0092]

[0093] The detection value J was obtained. K .

[0094] It should be noted that the above method of detecting inter-turn short circuits by detecting negative sequence current / voltage is simple to implement; the ratio method described above can more accurately reflect the inter-turn short circuit situation; and the method described above, combined with the rotational speed factor, can better adapt to different operating conditions, but requires the establishment of an accurate linear relationship model. In practical applications, any of these methods can be selected for calculating the detection values ​​according to the operating conditions required.

[0095] Step 3: Obtain the original short-circuit fault detection result based on the difference between the initial detection threshold and the detected value.

[0096] The initial detection threshold is determined by the positive-sequence and negative-sequence electrical signals of the permanent magnet traction system under normal operating conditions. The original short-circuit fault detection result is either a short-circuit fault occurred or no short-circuit fault occurred. When the difference is less than zero, the original short-circuit fault detection result is no short-circuit fault occurred; when the difference is greater than zero, the original short-circuit fault detection result is a short-circuit fault occurred.

[0097] In the embodiments of the present invention, the calculation method of the initial detection threshold is the same as the calculation method of the detection value, which uses the positive sequence electrical signal and negative sequence electrical signal of the permanent magnet traction system under normal operating conditions.

[0098] Step 4: If the original short-circuit fault detection result indicates a short-circuit fault has occurred, the three-level isolation controller is closed, and steps 1 to 3 are executed again to obtain a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, the original short-circuit fault detection result is determined as the final short-circuit fault detection result. Otherwise, the initial detection threshold is updated according to the preset step size to obtain an intermediate detection threshold, and this intermediate detection threshold is used as the initial detection threshold in step 3. Step 3 is then executed again.

[0099] It should be noted that the purpose of controlling the closure of the three-level isolation controller is to avoid interference from the inverter on short-circuit fault detection and improve the accuracy of short-circuit fault detection.

[0100] If the new short-circuit fault detection result is different from the original short-circuit fault detection result, it may indicate that the inverter power device is malfunctioning or the pulse signal link is abnormal, resulting in an unbalanced inverter output and thus a misdiagnosis of the short-circuit fault.

[0101] The following explains the process of updating the initial detection threshold to obtain the intermediate detection threshold.

[0102] Specifically, through calculation formula

[0103]

[0104] Obtain the intermediate detection threshold in, This indicates the initial detection threshold.

[0105] It is worth mentioning that the present invention improves the accuracy of short-circuit fault detection by updating and correcting the threshold in real time.

[0106] It should be noted that when the final short-circuit fault detection result indicates a short-circuit fault, the corresponding fault information can be sent to the driver's terminal or dispatch command center for timely vehicle maintenance and repair to prevent safety accidents. Because permanent magnet synchronous motors use permanent magnets for rotor excitation, their no-load back EMF increases accordingly with motor speed. This means that after an inter-turn short-circuit fault occurs, even if the inverter stops and the isolating contactor disconnects, the back EMF generated by the continued operation of the vehicle driving the faulty motor will create a large short-circuit current at the short-circuit location, generating additional heat that causes the motor temperature to rise sharply and may even lead to a fire. Therefore, currently, when an inter-turn short circuit occurs in a permanent magnet synchronous traction motor, in addition to shutting down the inverter and disconnecting the isolating switch, based on the motor's back EMF characteristics, the train is required to run at a certain speed limit to the next station for a change of train.

[0107] In summary, the short-circuit fault detection method provided by this invention, when the original short-circuit fault detection result indicates a short-circuit fault, controls the three-level isolation controller to close, disconnects the inverter, re-acquires and detects electrical signals, and obtains a new short-circuit fault detection result. Only when the original short-circuit fault detection result and the new short-circuit fault detection result are the same is the original short-circuit fault detection result determined as the final short-circuit fault detection result. This effectively avoids the interference of the inverter on short-circuit fault detection and improves the accuracy of short-circuit fault detection. When the original short-circuit fault detection result and the new short-circuit fault detection result are different, the initial detection threshold can be updated, and the threshold can be updated and corrected in real time, which is beneficial to improving the accuracy of short-circuit fault detection.

[0108] The short-circuit fault detection device provided by the present invention will be described below.

[0109] like Figure 3 As shown, the short-circuit fault detection device 300 includes:

[0110] The feature extraction module 301 is used to collect electrical signals from the output side of the inverter and decompose the electrical signals to obtain positive-sequence electrical signals and negative-sequence electrical signals; the electrical signals are three-phase current signals or three-phase voltage signals.

[0111] The detection calculation module 302 is used to calculate the detection value for short-circuit fault detection based on the positive sequence electrical signal and the negative sequence electrical signal.

[0112] The preliminary detection module 303 is used to obtain the original short-circuit fault detection result based on the difference between the initial detection threshold and the detection value; the initial detection threshold is determined by the positive sequence electrical signal and the negative sequence electrical signal of the permanent magnet traction system under normal operating conditions, and the original short-circuit fault detection result is whether a short-circuit fault has occurred or not.

[0113] The re-detection module 304 is used to control the three-level isolation controller to close if the original short-circuit fault detection result is a short-circuit fault, and return to the execution feature extraction module 301 to the preliminary detection module 303 to obtain a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, the original short-circuit fault detection result is determined as the final short-circuit fault detection result; otherwise, the initial detection threshold is updated according to the preset step to obtain the intermediate detection threshold, and the intermediate detection threshold is used as the initial detection threshold in the preliminary detection module 303, and the execution of the preliminary detection module 303 is returned.

[0114] It should be noted that the information interaction and execution process between the above-mentioned devices / units are different from the method of this application.

[0115] The embodiments are based on the same concept, and their specific functions and technical effects can be found in the method embodiment section, which will not be repeated here. Those skilled in the art will understand that, for ease of description and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0116] like Figure 4 As shown, embodiments of the present invention provide a terminal device, such as... Figure 4 As shown, the terminal device D10 of this embodiment includes: at least one processor D100 ( Figure 4 The diagram shows only one processor, a memory D101, and a computer program D102 stored in the memory D101 and executable on the at least one processor D100, wherein the processor D100 executes the computer program D102 to implement the steps in any of the above method embodiments.

[0117] Specifically, when the processor D100 executes the computer program D102, it performs the following steps: Step 1: Acquires the electrical signal from the inverter output side and decomposes the electrical signal to obtain a positive-sequence electrical signal and a negative-sequence electrical signal; Step 2: Calculates the detection value for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal; Step 3: Obtains the original short-circuit fault detection result based on the difference between the initial detection threshold and the detection value; Step 4: If the original short-circuit fault detection result indicates a short-circuit fault, it controls the three-level isolation controller to close, returns to steps 1 to 3, and obtains a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, the original short-circuit fault detection result is determined as the final short-circuit fault detection result; otherwise, it updates the initial detection threshold according to a preset step to obtain an intermediate detection threshold, and uses the intermediate detection threshold as the initial detection threshold in step 3, then returns to step 3. Specifically, when the initial short-circuit fault detection result indicates a short-circuit fault, the three-level isolation controller is closed to disconnect the inverter, and the electrical signal is re-acquired and detected to obtain a new short-circuit fault detection result. Only when the initial short-circuit fault detection result and the new short-circuit fault detection result are the same is the initial short-circuit fault detection result determined as the final short-circuit fault detection result. This effectively avoids the inverter's interference with short-circuit fault detection and improves the accuracy of short-circuit fault detection. When the initial short-circuit fault detection result and the new short-circuit fault detection result are different, the initial detection threshold can be updated. Real-time updating and correction of the threshold is beneficial to improving the accuracy of short-circuit fault detection.

[0118] The processor D100 can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0119] In some embodiments, the memory D101 may be an internal storage unit of the terminal device D10, such as a hard disk or memory of the terminal device D10. In other embodiments, the memory D101 may be an external storage device of the terminal device D10, such as a plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, etc., equipped on the terminal device D10. Furthermore, the memory D101 may include both internal and external storage units of the terminal device D10. The memory D101 is used to store the operating system, applications, bootloader, data, and other programs, such as the program code of the computer program. The memory D101 can also be used to temporarily store data that has been output or will be output.

[0120] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps described in the various method embodiments above.

[0121] This application provides a computer program product that, when run on a terminal device, enables the terminal device to implement the steps described in the various method embodiments above.

[0122] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0123] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A short-circuit fault detection method for a permanent magnet traction system, the permanent magnet traction system comprising a permanent magnet synchronous motor and an inverter connected to the permanent magnet synchronous motor in three phases, wherein a three-level isolation controller is connected between the permanent magnet synchronous motor and the inverter, characterized in that, The short-circuit fault detection method includes: Step 1: Acquire the electrical signal from the output side of the inverter and decompose the electrical signal to obtain the positive sequence electrical signal and the negative sequence electrical signal; the electrical signal is a three-phase current signal or a three-phase voltage signal. Step 2: Calculate the detection value for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal; Step 3: Obtain the original short-circuit fault detection result based on the difference between the initial detection threshold and the detected value; the initial detection threshold is determined by the positive-sequence electrical signal and the negative-sequence electrical signal of the permanent magnet traction system under normal operating conditions; the original short-circuit fault detection result is either a short-circuit fault has occurred or no short-circuit fault has occurred. Step 4: If the original short-circuit fault detection result indicates a short-circuit fault has occurred, control the three-level isolation controller to close, and return to execute steps 1 to 3 to obtain a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, then the original short-circuit fault detection result is determined as the final short-circuit fault detection result; otherwise, update the initial detection threshold according to a preset step to obtain an intermediate detection threshold, and use the intermediate detection threshold as the initial detection threshold in step 3, then return to execute step 3. Updating the initial detection threshold according to a preset step to obtain the intermediate detection threshold includes: using a calculation formula... The intermediate detection threshold is obtained. ;in, This represents the initial detection threshold.

2. The short-circuit fault detection method according to claim 1, characterized in that, The process of decomposing the electrical signal to obtain positive-sequence and negative-sequence electrical signals includes: When the electrical signal is a three-phase current signal, it is calculated using the formula. in, Indicates a positive sequence current signal. This indicates the U-phase output current of the inverter. Indicates U phase, , This indicates the V-phase output current of the inverter. This indicates the output W-phase current of the inverter. , This indicates a negative sequence current signal. This indicates the three phases U, V, and W on the inverter output side; When the electrical signal is a three-phase voltage signal, it is calculated using the formula. in, This indicates a positive sequence voltage signal. This indicates the inverter output UV line voltage. This indicates the inverter output line voltage VW. This indicates the inverter's output UW line voltage.

3. The short-circuit fault detection method according to claim 2, characterized in that, The step of calculating the detection value for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal includes: When the electrical signal is a three-phase current signal, it is calculated using the formula. or or The detection value is obtained ;in, The negative sequence current threshold represents the linear relationship with rotational speed. This indicates the rotational speed of the permanent magnet synchronous motor; When the electrical signal is a three-phase voltage signal, it is calculated using the formula. or or The detection value is obtained .

4. The short-circuit fault detection method according to claim 3, characterized in that, The calculation method for the initial detection threshold is the same as that for the detection value, using the positive-sequence electrical signal and negative-sequence electrical signal of the permanent magnet traction system under normal operating conditions.

5. The short-circuit fault detection method according to claim 4, characterized in that, The step of obtaining the original short-circuit fault detection result based on the difference between the initial detection threshold and the detected value includes: If the difference is greater than zero, the original short-circuit fault detection result is determined to be a short-circuit fault; otherwise, the original short-circuit fault detection result is determined to be no short-circuit fault.

6. The short-circuit fault detection method according to claim 1, characterized in that, Before decomposing the electrical signal, the short-circuit fault detection method further includes: For any two phases of the electrical signal, calculate the theoretical value of the third phase electrical signal based on those two phases. If the error between the theoretical value of the third-phase electrical signal and the actual value of the acquired third-phase electrical signal is greater than a preset threshold, the third-phase electrical signal is reacquired until the error is less than or equal to the preset threshold.

7. A short-circuit fault detection device for a permanent magnet traction system, the permanent magnet traction system comprising a permanent magnet synchronous motor and an inverter connected to the permanent magnet synchronous motor in three phases, wherein a three-level isolation controller is connected between the permanent magnet synchronous motor and the inverter, characterized in that, include: The feature extraction module is used to collect the electrical signal on the output side of the inverter and decompose the electrical signal to obtain the positive sequence electrical signal and the negative sequence electrical signal. The electrical signal is a three-phase current signal or a three-phase voltage signal; The detection calculation module is used to calculate the detection value for short-circuit fault detection based on the positive-sequence electrical signal and the negative-sequence electrical signal. The preliminary detection module is used to obtain the original short-circuit fault detection result based on the difference between the initial detection threshold and the detection value; the initial detection threshold is determined by the positive sequence electrical signal and the negative sequence electrical signal of the permanent magnet traction system under normal operating conditions; the original short-circuit fault detection result is either a short-circuit fault has occurred or no short-circuit fault has occurred. The re-detection module is used to control the three-level isolation controller to close if the original short-circuit fault detection result indicates a short-circuit fault has occurred, and return to the preliminary detection module to execute the feature extraction module to obtain a new short-circuit fault detection result. If the new short-circuit fault detection result is the same as the original short-circuit fault detection result, the original short-circuit fault detection result is determined as the final short-circuit fault detection result; otherwise, the initial detection threshold is updated according to a preset step to obtain an intermediate detection threshold, and the intermediate detection threshold is used as the initial detection threshold in the preliminary detection module, returning to execute the preliminary detection module. The step of updating the initial detection threshold according to a preset step to obtain the intermediate detection threshold includes: using a calculation formula... The intermediate detection threshold is obtained. ;in, This represents the initial detection threshold.

8. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 6.

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