Permanent magnet traction motor fault detection method, traction device and train

Abstract

The invention discloses a permanent magnet traction motor fault detection method, a traction device and a train. The permanent magnet traction motor fault detection method comprises the steps of obtaining a current working condition of a permanent magnet traction motor and a negative sequence current of the permanent magnet traction motor under the current working condition; calculating a negative sequence current threshold value of the permanent magnet traction motor under the current working condition according to the current working condition of the permanent magnet traction motor and the dynamic threshold value model; if the negative sequence current of the permanent magnet traction motor under the current working condition is greater than the negative sequence current threshold value of the permanent magnet traction motor under the current working condition, determining that the permanent magnet traction motor has a turn-to-turn short circuit fault; and if the negative sequence current of the permanent magnet traction motor under the current working condition is smaller than or equal to the negative sequence current threshold value of the permanent magnet traction motor under the current working condition, determining that the permanent magnet traction motor does not have the turn-to-turn short circuit fault. According to the permanent magnet traction motor fault detection method provided by the embodiment of the invention, the fault detection accuracy of the permanent magnet traction motor can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor fault diagnosis, and in particular to a permanent magnet traction motor fault detection method, a traction device and a train. Background Art

[0002] Permanent magnet traction motors (PMTMs) are widely used in traction systems for rail transit, electric vehicles, and other applications due to their high efficiency and power density. However, over long-term operation, the motor windings can develop interturn short circuits due to insulation aging, mechanical damage, or overvoltage surges. These short circuits can cause circulating currents, localized overheating, and insulation degradation. In severe cases, they can cause motor burnout and threaten system safety. Therefore, fault detection is essential during operation to ensure safe operation of PMTMs.

[0003] In the prior art, fault detection of a permanent magnet traction motor is mostly achieved by comparing the negative sequence current limit during operation of the permanent magnet traction motor with a fixed threshold.

[0004] However, the negative sequence current of the permanent magnet traction motor is different under different operating conditions, and the fixed threshold judgment cannot cover all different operating conditions of the permanent magnet traction motor. Therefore, when using a fixed threshold to judge the fault of the permanent magnet traction motor, it is easy to make misjudgments and missed judgments, and the fault detection accuracy of the permanent magnet traction motor is poor. Summary of the Invention

[0005] The present invention provides a permanent magnet traction motor fault detection method, a traction device and a train, so as to improve the fault detection accuracy of the permanent magnet traction motor.

[0006] According to one aspect of the present invention, a method for detecting a fault in a permanent magnet traction motor is provided. The method comprises:

[0007] Obtaining a current operating condition of the permanent magnet traction motor and a negative sequence current of the permanent magnet traction motor under the current operating condition;

[0008] Calculating a negative-sequence current threshold of the permanent magnet traction motor under the current operating condition according to the current operating condition of the permanent magnet traction motor and a dynamic threshold model; wherein the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition is a maximum negative-sequence current of the permanent magnet traction motor when no turn-to-turn short circuit occurs under the current operating condition;

[0009] If the negative sequence current of the permanent magnet traction motor under the current working condition is greater than the negative sequence current threshold of the permanent magnet traction motor under the current working condition, it is determined that an inter-turn short circuit fault occurs in the permanent magnet traction motor;

[0010] If the negative sequence current of the permanent magnet traction motor under the current operating condition is less than or equal to the negative sequence current threshold of the permanent magnet traction motor under the current operating condition, it is determined that no inter-turn short circuit fault occurs in the permanent magnet traction motor.

[0011] Optionally, a specific method for obtaining the dynamic threshold model includes:

[0012] Obtaining a transient negative sequence current of the permanent magnet traction motor when a short turn fault with different numbers of turns occurs under different operating conditions; wherein the number of turns of the short turn fault of the permanent magnet traction motor is greater than or equal to zero;

[0013] A family of characteristic curves is obtained by fitting each transient negative sequence current of the permanent magnet traction motor under different operating conditions based on the number of turns of the permanent magnet traction motor with a short turn fault; wherein the family of characteristic curves includes characteristic curves of transient negative sequence current under short turn faults with different numbers of turns as a function of operating conditions;

[0014] The dynamic threshold model is established according to the family of characteristic curves; wherein, the dynamic threshold model is a lookup table, a mathematical function or a machine learning model that outputs the corresponding negative sequence current threshold according to the previous operating condition.

[0015] Optionally, the specific method for obtaining the transient negative sequence current when the permanent magnet traction motor has a short turn fault with different numbers of turns under different operating conditions includes:

[0016] Simulating the occurrence of short-turn faults with different numbers of turns in the permanent magnet traction motor under different operating conditions;

[0017] detecting the transient current of the permanent magnet traction motor when a short-turn fault with different numbers of turns occurs under different operating conditions;

[0018] The negative sequence component in the transient current of the permanent magnet traction motor when a short turn fault with different numbers of turns occurs under different working conditions is extracted to obtain the transient negative sequence current of the permanent magnet traction motor when a short turn fault with different numbers of turns occurs under different working conditions.

[0019] Optionally, a specific method for obtaining the negative sequence current of the permanent magnet traction motor under the current operating condition includes:

[0020] detecting an input current of the permanent magnet traction motor under a current operating condition;

[0021] A negative sequence component in the input current of the permanent magnet traction motor under the current working condition is extracted to obtain a negative sequence current of the permanent magnet traction motor under the current working condition.

[0022] Optionally, after determining that an inter-turn short circuit fault occurs in the permanent magnet traction motor, the method further includes:

[0023] determining a first fault threshold and a second fault threshold according to a negative sequence current threshold of the permanent magnet traction motor under a current operating condition;

[0024] If the negative sequence current of the permanent magnet traction motor under the current working condition is less than the first fault threshold, an alarm is issued to the user;

[0025] If the negative sequence current of the permanent magnet traction motor under the current working condition is greater than or equal to the first fault threshold and less than the second fault threshold, an alarm is issued to the user, and the permanent magnet traction motor is subjected to field weakening control;

[0026] If the negative sequence current of the permanent magnet traction motor under the current working condition is greater than or equal to the second fault threshold, an alarm is issued to the user, and the permanent magnet magnetic field of the permanent magnet traction motor is suppressed.

[0027] According to another aspect of the present invention, there is further provided a traction device, the traction device comprising: an inverter module, a detection module, a control module and a permanent magnet traction motor;

[0028] The inverter module is used to access direct current, the inverter module is connected to the permanent magnet traction motor through the detection module, and the control module is connected to the inverter module and the detection module respectively;

[0029] The inverter module is used to convert the direct current into the three-phase alternating current required for the operation of the permanent magnet traction motor; the permanent magnet traction motor is used to convert electrical energy into mechanical energy; the detection module is used to detect the input current of the permanent magnet traction motor; the control module is used to execute the permanent magnet traction motor fault detection method described in any of the above embodiments.

[0030] Optionally, the detection module includes: at least two current sensors;

[0031] Each of the current sensors is arranged on a different phase line between the inverter module and the permanent magnet traction motor.

[0032] Optionally, the traction device further comprises: an isolating switch module;

[0033] The isolating switch module is connected between the detection module and the permanent magnet traction motor, and the isolating switch module is also connected to the control module;

[0034] The isolating switch module is used to maintain the shutdown state when the permanent magnet traction motor is being repaired.

[0035] Optionally, the isolation switch module includes: a solid-state contactor, a circuit breaker or an integrated electronic switch.

[0036] According to yet another aspect of the present invention, a train is provided, comprising the traction device described in any one of the above embodiments.

[0037] An embodiment of the present invention calculates a negative-sequence current threshold value of a permanent magnet traction motor under the current operating condition based on the current operating condition of the permanent magnet traction motor and a dynamic threshold model. The permanent magnet traction motor is then judged to have an inter-turn circuit fault based on the negative-sequence current and the negative-sequence current threshold value. When the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than the negative-sequence current threshold value, the permanent magnet traction motor is judged to have an inter-turn short circuit fault. The embodiment of the present invention dynamically calculates the negative-sequence current threshold value under different operating conditions of the permanent magnet traction motor using the operating condition and dynamic threshold model of the permanent magnet traction motor. The dynamically calculated negative-sequence current threshold value under different operating conditions is used to perform targeted fault determination for the permanent magnet traction motor under different operating conditions. This reduces the possibility of the negative-sequence current generated by the inherent imbalance of the permanent magnet traction motor under low-load and low-speed operating conditions being misjudged as a fault, and reduces the possibility of minor inter-turn short circuit faults being missed due to excessively low threshold values ​​under high-load and high-speed operating conditions, thereby improving the fault detection accuracy of the permanent magnet traction motor.

[0038] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 This is a flow chart of a permanent magnet traction motor fault detection method provided by an embodiment of the present invention;

[0041] Figure 2 This is a flow chart of a method for obtaining a dynamic threshold model provided by an embodiment of the present invention;

[0042] Figure 3 is a schematic diagram of a turn-end fault with different numbers of turns provided by an embodiment of the present invention;

[0043] Figure 4 is a schematic diagram of a family of characteristic curves provided by an embodiment of the present invention;

[0044] Figure 5 is a schematic diagram of another characteristic curve family provided by an embodiment of the present invention;

[0045] Figure 6 is a flow chart of another permanent magnet traction motor fault detection method provided by an embodiment of the present invention;

[0046] Figure 7 1 is a schematic diagram of a three-phase short circuit of a permanent magnet traction motor provided by an embodiment of the present invention;

[0047] Figure 8 is a schematic diagram of a traction device provided by an embodiment of the present invention;

[0048] Figure 9 Schematic diagram of a train provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0050] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0051] An embodiment of the present invention provides a permanent magnet traction motor fault detection method. This permanent magnet traction motor fault detection method is applicable to permanent magnet traction motor fault detection. By dynamically calculating the negative-sequence current threshold under different operating conditions of the permanent magnet traction motor using the operating conditions and dynamic threshold model of the permanent magnet traction motor, the method uses the dynamically calculated negative-sequence current threshold under different operating conditions to perform targeted fault determination on the permanent magnet traction motor under different operating conditions, thereby improving the accuracy of permanent magnet traction motor fault detection. Figure 1 This is a flow chart of a method for detecting a permanent magnet traction motor fault provided by an embodiment of the present invention. Figure 1 , the permanent magnet traction motor fault detection method includes:

[0052] S110: Obtain the current operating condition of the permanent magnet traction motor and the negative sequence current of the permanent magnet traction motor under the current operating condition.

[0053] Specifically, the operating conditions of the permanent magnet traction motor include speed, torque, traction force, and load state. The load state includes starting, acceleration, constant speed, and braking. For example, the operating conditions of the permanent magnet traction motor can be detected by sensors.

[0054] The negative-sequence current of the permanent magnet traction motor under the current operating condition can be obtained by analyzing the input current of the permanent magnet traction motor under the current operating condition. The negative-sequence current of the permanent magnet traction motor under the current operating condition can be obtained by extracting the negative-sequence component of the input current of the permanent magnet traction motor under the current operating condition. The negative-sequence component of the input current of the permanent magnet traction motor under the current operating condition can be extracted by fast Fourier transform or discrete wavelet transform. For example, the negative-sequence current of the permanent magnet traction motor under the current operating condition can also be obtained by sensor detection.

[0055] S120. Calculate the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition based on the current operating condition of the permanent magnet traction motor and a dynamic threshold model; wherein the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition is the maximum negative-sequence current of the permanent magnet traction motor when no turn-to-turn short circuit occurs under the current operating condition.

[0056] Specifically, the dynamic threshold model characterizes the relationship between the operating condition of the permanent magnet traction motor and the negative-sequence current threshold. The input current of the permanent magnet traction motor is related to the motor's operating condition, requiring different input currents for different operating conditions. Furthermore, the negative-sequence current of the permanent magnet traction motor is related to the motor's input current. Therefore, the negative-sequence current of the permanent magnet traction motor varies under different operating conditions. Consequently, the negative-sequence current threshold for the permanent magnet traction motor varies under different operating conditions.

[0057] S130. Determine whether the negative sequence current of the permanent magnet traction motor under the current operating condition is greater than the negative sequence current threshold of the permanent magnet traction motor under the current operating condition; if so, execute S140; if not, execute S150.

[0058] Specifically, the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition is the maximum negative-sequence current when the permanent magnet traction motor does not have an inter-turn short circuit under the current operating condition. When an inter-turn short circuit occurs in the permanent magnet traction motor, the impedance of the permanent magnet traction motor decreases, the input current of the permanent magnet traction motor increases, and the negative-sequence current of the permanent magnet traction motor also increases accordingly. Therefore, when the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition, it indicates that an inter-turn short circuit has occurred in the permanent magnet traction motor; when the negative-sequence current of the permanent magnet traction motor under the current operating condition is less than or equal to the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition, it indicates that the permanent magnet traction motor is in a normal state.

[0059] It should be noted that when the negative-sequence current of the permanent magnet traction motor under the current operating condition is less than or equal to the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition, the current operating condition of the permanent magnet traction motor and the negative-sequence current of the permanent magnet traction motor under the current operating condition are reacquired, and the negative-sequence current threshold of the reacquired permanent magnet traction motor under the current operating condition is calculated to continuously detect faults of the permanent magnet traction motor.

[0060] S140: Determine whether an inter-turn short circuit fault occurs in the permanent magnet traction motor.

[0061] For example, when an inter-turn short circuit fault occurs in the permanent magnet traction motor, an alarm may be issued to the user, so that the user can further investigate the short circuit fault of the permanent magnet traction motor.

[0062] S150: Determine that no inter-turn short circuit fault occurs in the permanent magnet traction motor.

[0063] The embodiment of the present invention calculates the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition based on the current operating condition and a dynamic threshold model of the permanent magnet traction motor, and determines whether an inter-turn circuit fault occurs in the permanent magnet traction motor based on the negative-sequence current of the permanent magnet traction motor under the current operating condition and the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition. When the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition, it is determined that an inter-turn short circuit fault occurs in the permanent magnet traction motor. The embodiment of the present invention dynamically calculates the negative-sequence current threshold of the permanent magnet traction motor under different operating conditions through the operating condition and dynamic threshold model of the permanent magnet traction motor, and uses the dynamically calculated negative-sequence current threshold under different operating conditions to perform targeted fault determination on the permanent magnet traction motor under different operating conditions, which is beneficial to improving the fault detection accuracy of the permanent magnet traction motor.

[0064] Figure 2 This is a flow chart of a method for obtaining a dynamic threshold model provided by an embodiment of the present invention. Based on the above embodiments, optionally, refer to Figure 2 , the specific method of obtaining the dynamic threshold model includes:

[0065] S210. Obtain each transient negative sequence current when a short-turn fault with different numbers of turns occurs in the permanent magnet traction motor under different operating conditions; wherein the number of turns of the short-turn fault of the permanent magnet traction motor is greater than or equal to zero.

[0066] Specifically, the transient negative-sequence current of a permanent magnet traction motor is related to the motor's operating conditions and the number of turn-to-turn short circuits. That is, the transient negative-sequence current of the permanent magnet traction motor under the same operating conditions varies depending on the number of turns experiencing short circuits. Therefore, when establishing a dynamic threshold model, the permanent magnet traction motor needs to detect the transient negative-sequence current corresponding to different numbers of turn-to-turn short circuits under different operating conditions. The transient negative-sequence current when the number of turn-to-turn short circuits is zero represents the transient negative-sequence current of the permanent magnet traction motor during normal operation under different operating conditions.

[0067] Since the negative sequence current of the permanent magnet traction motor can be obtained through the input current of the permanent magnet traction motor, the transient negative sequence current of the permanent magnet traction motor can be obtained through the transient input current of the permanent magnet traction motor.

[0068] To obtain the transient input currents of a permanent magnet traction motor under different operating conditions when a short-turn fault with different turns occurs, it is necessary to simulate various scenarios of the motor under these conditions. Since an inter-turn short circuit is a fault condition of the permanent magnet traction motor, to prevent the motor from burning out, the duration of the inter-turn short circuit must be limited during the simulation of the motor's short-turn fault. For example, the short-turn fault simulation duration can be limited to between 5 and 50 milliseconds. Therefore, the input current of the permanent magnet traction motor during the short-turn fault simulation is a transient current. By detecting the input current of the permanent magnet traction motor during the short-turn fault simulation, the transient input currents of the permanent magnet traction motor under different operating conditions when a short-turn fault with different turns occurs can be obtained. By extracting the negative-sequence component from the transient input currents of the permanent magnet traction motor under different operating conditions when a short-turn fault with different turns occurs, the transient negative-sequence currents of the permanent magnet traction motor under these conditions can be obtained. For example, the negative sequence components in each transient input current when a short-turn fault with different numbers of turns occurs in a permanent magnet traction motor under different operating conditions can be extracted by fast Fourier transform or discrete wavelet transform.

[0069] Among them, the simulation of various situations in which the permanent magnet traction motor has short-turn faults with different numbers of turns under different working conditions can be achieved through a test bench or a simulation model. Among them, the simulation model can be, for example, a finite element analysis model. It should be noted that the permanent magnet traction motor used in the simulation must be the same as the permanent magnet traction motor in actual application, that is, the same model of permanent magnet traction motor is used. Exemplarily, the inter-turn short circuit of the permanent magnet traction motor can be achieved by connecting a contactor in parallel to the winding of the permanent magnet traction motor. When the contactor is closed, an inter-turn short circuit occurs in the permanent magnet traction motor. When the number of windings connected in series between the two ends of the contactor is different, the number of turns of the permanent magnet traction motor that has short-turn faults is also different. Figure 3 FIG. 1 is a schematic diagram of a turn-end fault with different numbers of turns provided by an embodiment of the present invention. Figure 3For example, if the contactor is set in loop A1, when the contactor is closed, a one-turn short-circuit fault occurs in the permanent magnet traction motor; if the contactor is set in loop A2, when the contactor is closed, a three-turn short-circuit fault occurs in the permanent magnet traction motor; if the contactor is set in loop A3, when the contactor is closed, a five-turn short-circuit fault occurs in the permanent magnet traction motor. Optionally, in actual application, a protective device can be set in the circuit where the contactor is located to shut down the circuit or limit the current in the circuit when the contactor closing time reaches the maximum limit of the short-turn fault simulation time, thereby avoiding long-term short-circuit of the permanent magnet traction motor. For example, the protective device can be a fast fuse or an IGBT (Insulated Gate Bipolar Transistor) current limiting circuit.

[0070] It should be noted that the transient negative-sequence current is the transient value of the negative-sequence current detected when simulating a permanent magnet traction motor interturn short-circuit fault. In actual applications, the negative-sequence current of the permanent magnet traction motor under current operating conditions, as measured in actual usage scenarios, is also a transient value. The physical meaning of the two is the same; only the scenarios in which they are obtained differ.

[0071] S220. Fit the transient negative-sequence currents of the permanent magnet traction motor under different operating conditions based on the number of turns of the permanent magnet traction motor short-turn fault to obtain a family of characteristic curves under short-turn faults with different numbers of turns; wherein the family of characteristic curves includes a characteristic curve of the transient negative-sequence current under a short-turn fault with the same number of turns varying with the operating condition.

[0072] Specifically, fitting the transient negative-sequence current under short-turn faults with different numbers of turns can be achieved through machine learning algorithms, such as support vector machines (SVM) and convolutional neural networks (CNN). It should be noted that the transient negative-sequence current when the number of turns of the short-turn fault is zero is the transient negative-sequence current of the permanent magnet traction motor without a short-turn fault. Figure 4 This is a schematic diagram of a characteristic curve family provided by an embodiment of the present invention. When the number of turns of a short-turn fault is greater than zero, the negative sequence current changes with the working condition as shown in FIG. Figure 4 As shown. For example, referring to Figure 4 Curve 41 is the curve of negative sequence current changing with speed under 0 kN traction force, curve 42 is the curve of negative sequence current changing with speed under 25 kN traction force, curve 43 is the curve of negative sequence current changing with speed under 50 kN traction force, and curve 44 is the curve of negative sequence current changing with speed under 75 kN traction force.

[0073] When fitting the transient negative sequence currents under short-turn faults with different numbers of turns, the transient negative sequence current when the number of turns of the short-turn fault is zero also needs to be fitted. Figure 5 This is a schematic diagram of another characteristic curve family provided by an embodiment of the present invention. Figure 5 When the number of turns of the short-turn fault is zero, the negative sequence current changes with the working condition as shown in the following example: Figure 5 As shown. For example, referring to Figure 5 Curve 51 shows the negative sequence current versus speed curve under a traction force of 0 kN, curve 52 shows the negative sequence current versus speed curve under a traction force of 20 kN, curve 53 shows the negative sequence current versus speed curve under a traction force of 50 kN, curve 54 shows the negative sequence current versus speed curve under a traction force of 70 kN, and curve 55 shows the negative sequence current versus speed curve under a traction force of 98 kN.

[0074] S230. Establish a dynamic threshold model based on the family of characteristic curves; wherein the dynamic threshold model is a lookup table, mathematical function, or machine learning model that outputs a corresponding negative sequence current threshold based on the previous operating condition.

[0075] For example, the characteristic curves in the characteristic curve family are integrated by an optimization algorithm to establish a dynamic threshold model, wherein the optimization algorithm may be, for example, particle swarm optimization (PSO).

[0076] Figure 6 This is a flow chart of another method for detecting a permanent magnet traction motor fault provided by an embodiment of the present invention. Figure 6 After determining that a turn-to-turn short circuit fault occurs in the permanent magnet traction motor, the following steps are also included:

[0077] S160. Determine a first fault threshold and a second fault threshold according to the negative sequence current threshold under the current operating condition of the permanent magnet traction motor.

[0078] Specifically, the first and second fault thresholds are the magnitudes of the negative-sequence current used to determine fault severity. The first and second fault thresholds are smaller than the negative-sequence current threshold. Because the input current of the permanent magnet traction motor is dependent on its operating conditions, different operating conditions require different input currents. Furthermore, the negative-sequence current of the permanent magnet traction motor is dependent on its input current. Therefore, the first and second fault thresholds used to determine fault severity when a permanent magnet traction motor fault occurs are also different. In other words, the first and second fault thresholds are also dependent on the operating conditions of the permanent magnet traction motor.

[0079] In practical applications, the proportional relationship between different degrees of permanent magnet traction motor faults and the negative-sequence current threshold can be determined experimentally. Based on the proportional relationship between the permanent magnet traction motor fault severity and the negative-sequence current threshold, combined with the negative-sequence current threshold under the current operating condition of the permanent magnet traction motor, the first fault threshold and the second fault threshold under the current operating condition of the permanent magnet traction motor can be determined.

[0080] S170. Determine the range of the negative-sequence current of the permanent magnet traction motor under the current operating condition; if the negative-sequence current of the permanent magnet traction motor under the current operating condition is less than the first fault threshold, execute S171; if the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than or equal to the first fault threshold and less than the second fault threshold, execute S172; if the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than or equal to the second fault threshold, execute S173.

[0081] Specifically, the magnitude of the negative-sequence current during operation of a permanent magnet traction motor is related to the number of windings experiencing short-circuit faults. The greater the number of windings experiencing short-circuit faults, that is, the greater the number of turns experiencing short-circuit faults, the greater the negative-sequence current. The smaller the number of windings experiencing short-circuit faults, that is, the smaller the number of turns experiencing short-circuit faults, the smaller the negative-sequence current. In practical applications, the first and second fault thresholds can be set according to actual needs to correspond to different degrees of inter-turn short-circuit fault severity, thereby quantitatively determining the degree of fault in the permanent magnet traction motor.

[0082] When the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition and is less than the first fault threshold, it indicates that the permanent magnet traction motor has a fault at this time, but the impact of this fault on the operation of the permanent magnet traction motor can be ignored; when the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than or equal to the first fault threshold and less than the second fault threshold, it indicates that the permanent magnet traction motor has a fault at this time, the permanent magnet traction motor can still operate, but the operating voltage of the permanent magnet traction motor needs to be reduced; when the negative-sequence current of the permanent magnet traction motor under the current operating condition is greater than or equal to the second fault threshold and less than the third fault threshold, it indicates that the permanent magnet traction motor has a fault at this time, the permanent magnet traction motor cannot continue to operate, and the permanent magnet traction motor needs to be shut down.

[0083] S171. Alarm the user.

[0084] For example, the form of warning to the user may be a text message warning or an audible and visual warning.

[0085] S172. Alarm the user and perform magnetic weakening control on the permanent magnet traction motor.

[0086] Specifically, the weak magnetic control of the permanent magnet traction motor can use the negative stator direct-axis current to generate a demagnetizing direct-axis armature reaction flux, partially offsetting the effect of the permanent magnet excitation flux, thereby reducing the direct-axis flux and the speed electromotive force generated thereby, reducing the electromotive force of the short-circuit loop between the drive turns, and reducing the thermal shock and mechanical stress of the short-circuit current on the winding.

[0087] S173. Alarm the user and suppress the permanent magnet magnetic field of the permanent magnet traction motor.

[0088] Specifically, suppressing the permanent magnet magnetic field of the permanent magnet traction motor can be achieved by short-circuiting the three phases of the permanent magnet traction motor. The three-phase short-circuiting of the permanent magnet traction motor can be achieved by simultaneously turning on the three upper bridge arms or the three lower bridge arms of the inverter connected to the three input terminals of the permanent magnet traction motor. Figure 7 Schematic diagram of a three-phase short circuit of a permanent magnet traction motor provided by an embodiment of the present invention. Figure 7 When the three upper bridge arms in the inverter are turned on at the same time, the three input terminals of the permanent magnet traction motor are short-circuited, and the three phases of the permanent magnet traction motor are short-circuited.

[0089] When the three input terminals of the permanent magnet traction motor are short-circuited, a zero voltage vector is formed, and the winding voltage excitation is instantaneously eliminated. At this time, the synthetic rotating magnetic field is significantly weakened, and the inter-turn short-circuit loop current decays rapidly in a passive state, thereby suppressing current peaks, thermal shock and electromagnetic stress.

[0090] An embodiment of the present invention further provides a traction device. Figure 8 Schematic diagram of a traction device provided by an embodiment of the present invention. Figure 8 The traction device includes: an inverter module 110, a detection module 120, a control module 130 and a permanent magnet traction motor 140.

[0091] The inverter module 110 is used to access direct current (DC). The inverter module 110 is connected to the permanent magnet traction motor 140 via the detection module 120. The control module 130 is connected to the inverter module 110 and the detection module 120 respectively. The inverter module 110 is used to convert direct current (DC) into three-phase alternating current (AC) required for the operation of the permanent magnet traction motor 140. The permanent magnet traction motor 140 is used to convert electrical energy into mechanical energy. The detection module 120 is used to detect the input current of the permanent magnet traction motor 140. The control module 130 is used to execute the permanent magnet traction motor fault detection method provided in any of the above embodiments. For example, the control module 130 can be a microcontroller unit (MCU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application-specific integrated circuit (ASIC).

[0092] Specifically, the inverter module 110 converts direct current (DC) into three-phase alternating current (AC) to supply the permanent magnet traction motor 140. The inverter module 110 may be composed of multiple power electronic devices, such as insulated gate bipolar transistors (IGBTs). The switching logic of these power electronic devices is modulated in real time by the control module 130 to control the operating state of the permanent magnet traction motor 140.

[0093] The detection module 120 collects the three-phase current signal output by the inverter module 110 to the permanent magnet traction motor 140. For example, the detection module 120 can be composed of a current sensor. Figure 8 At least two current sensors 121 are provided in the detection module 120. Each current sensor 121 is provided on a different phase line between the inverter module 110 and the permanent magnet traction motor 140.

[0094] The control module 130 obtains the operating instructions issued by the user and the three-phase current signals collected by the detection module 120 in real time, and generates control instructions based on the operating instructions and the three-phase current signals to control the operation of the inverter module 110, thereby controlling the operating state of the permanent magnet traction motor 140. For example, the control instructions can be space vector pulse width modulation (SVPWM) signals or pulse width modulation (PWM) signals.

[0095] On the basis of the above embodiments, optionally, continue to refer to Figure 8The traction device also includes: an isolation switch module 150.

[0096] The isolating switch module 150 is connected between the detection module 120 and the permanent magnet traction motor 140 , and is also connected to the control module 130 ; the isolating switch module 150 is used to maintain the permanent magnet traction motor 140 closed during maintenance.

[0097] Specifically, the isolation switch module 150 electrically isolates the permanent magnet traction motor 140 from the inverter module 110 during fault repair of the permanent magnet traction motor 140, ensuring that the permanent magnet traction motor 140 is de-energized. When the permanent magnet traction motor 140 is undergoing repair, the control module 140 controls the isolation switch module 150 to shut down, electrically isolating the permanent magnet traction motor 140 from the inverter module 110. Exemplarily, the isolation switch module can be a solid-state contactor, a circuit breaker, or an integrated electronic switch.

[0098] An embodiment of the present invention further provides a train. Figure 9 Schematic diagram of a train provided by an embodiment of the present invention. Figure 9 The train 10 includes the traction device 100 provided by any of the above embodiments.

[0099] The train 10 provided in this embodiment has the beneficial effects of the traction device 100 provided in any of the above embodiments, which will not be described in detail here.

[0100] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0101] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A permanent magnet traction motor fault detection method, characterized in that: include: Obtaining a current operating condition of the permanent magnet traction motor and a negative sequence current of the permanent magnet traction motor under the current operating condition; Calculating a negative-sequence current threshold of the permanent magnet traction motor under the current operating condition according to the current operating condition of the permanent magnet traction motor and a dynamic threshold model; wherein the negative-sequence current threshold of the permanent magnet traction motor under the current operating condition is a maximum negative-sequence current of the permanent magnet traction motor when no turn-to-turn short circuit occurs under the current operating condition; If the negative sequence current of the permanent magnet traction motor under the current working condition is greater than the negative sequence current threshold of the permanent magnet traction motor under the current working condition, it is determined that an inter-turn short circuit fault occurs in the permanent magnet traction motor; If the negative sequence current of the permanent magnet traction motor under the current operating condition is less than or equal to the negative sequence current threshold of the permanent magnet traction motor under the current operating condition, it is determined that no inter-turn short circuit fault occurs in the permanent magnet traction motor.

2. The permanent magnet traction motor fault detection method according to claim 1, characterized in that: The specific method for obtaining the dynamic threshold model includes: Obtaining a transient negative sequence current of the permanent magnet traction motor when a short turn fault with different numbers of turns occurs under different operating conditions; wherein the number of turns of the short turn fault of the permanent magnet traction motor is greater than or equal to zero; A family of characteristic curves is obtained by fitting each transient negative sequence current of the permanent magnet traction motor under different operating conditions based on the number of turns of the permanent magnet traction motor with a short turn fault; wherein the family of characteristic curves includes characteristic curves of transient negative sequence current under short turn faults with different numbers of turns as a function of operating conditions; The dynamic threshold model is established according to the family of characteristic curves; wherein, the dynamic threshold model is a lookup table, a mathematical function or a machine learning model that outputs the corresponding negative sequence current threshold according to the previous operating condition.

3. The permanent magnet traction motor fault detection method according to claim 2, characterized in that: The specific method for obtaining the transient negative sequence current when the permanent magnet traction motor has a short turn fault with different numbers of turns under different working conditions includes: Simulating the occurrence of short-turn faults with different numbers of turns in the permanent magnet traction motor under different operating conditions; detecting the transient current of the permanent magnet traction motor when a short-turn fault with different numbers of turns occurs under different operating conditions; The negative sequence component in the transient current of the permanent magnet traction motor when a short turn fault with different numbers of turns occurs under different working conditions is extracted to obtain the transient negative sequence current of the permanent magnet traction motor when a short turn fault with different numbers of turns occurs under different working conditions.

4. The permanent magnet traction motor fault detection method according to claim 1, characterized in that: The specific method for obtaining the negative sequence current of the permanent magnet traction motor under the current working condition includes: detecting an input current of the permanent magnet traction motor under a current operating condition; A negative sequence component in the input current of the permanent magnet traction motor under the current working condition is extracted to obtain a negative sequence current of the permanent magnet traction motor under the current working condition.

5. The permanent magnet traction motor fault detection method according to any one of claims 1 to 4, characterized in that: After determining that an inter-turn short circuit fault occurs in the permanent magnet traction motor, the method further includes: determining a first fault threshold and a second fault threshold according to a negative sequence current threshold of the permanent magnet traction motor under a current operating condition; If the negative sequence current of the permanent magnet traction motor under the current working condition is less than the first fault threshold, an alarm is issued to the user; If the negative sequence current of the permanent magnet traction motor under the current working condition is greater than or equal to the first fault threshold and less than the second fault threshold, an alarm is issued to the user, and the permanent magnet traction motor is subjected to field weakening control; If the negative sequence current of the permanent magnet traction motor under the current working condition is greater than or equal to the second fault threshold, an alarm is issued to the user, and the permanent magnet magnetic field of the permanent magnet traction motor is suppressed.

6. A traction device, characterized in that: include: Inverter module, detection module, control module and permanent magnet traction motor; The inverter module is used to access direct current, the inverter module is connected to the permanent magnet traction motor through the detection module, and the control module is connected to the inverter module and the detection module respectively; The inverter module is used to convert the direct current into the three-phase alternating current required for the operation of the permanent magnet traction motor; the permanent magnet traction motor is used to convert electrical energy into mechanical energy; the detection module is used to detect the input current of the permanent magnet traction motor; the control module is used to execute the permanent magnet traction motor fault detection method as described in any one of claims 1-5.

7. The traction device according to claim 6, characterized in that The detection module includes: at least two current sensors; Each of the current sensors is arranged on a different phase line between the inverter module and the permanent magnet traction motor.

8. The traction device according to claim 6, characterized in that: Also includes: Isolating switch module; The isolating switch module is connected between the detection module and the permanent magnet traction motor, and the isolating switch module is also connected to the control module; The isolating switch module is used to maintain the shutdown state when the permanent magnet traction motor is being repaired.

9. The traction device according to claim 8, characterized in that The isolating switch module includes: a solid-state contactor, a circuit breaker or an integrated electronic switch.

10. A train, characterized in that: The invention comprises a traction device according to any one of claims 6 to 9.

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