Multi-fault diagnosis method for switched reluctance motor driving system based on current behavior

Abstract

The invention provides a switched reluctance motor driving system multi-fault diagnosis method based on current behaviors, and belongs to the field of motor driving system fault diagnosis. According to the method, the installation positions of three inherent current sensors of the motor are reselected without increasing the number of the sensors, the three-phase current value is accurately reconstructed by changing the measurement path and the measurement current branch number of each sensor, and after a fault occurs, the monitored current value of a corresponding device has a large deviation from the theoretical current value, and the fault is detected. Through analysis of the current deviation behavior, rapid diagnosis and positioning of various component faults, including current sensor faults, winding open-circuit faults, power diode open-circuit faults and switch tube open-circuit and short-circuit mixed faults, of the switch reluctance motor driving system can be realized. And the health condition of the switched reluctance motor driving system can be monitored conveniently.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault diagnosis of motor drive systems, and particularly relates to a multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior. Background Art

[0002] Compared with traditional motors, switched reluctance motors have the advantages of simple structure, high efficiency, flexible control, low cost, etc., which makes them widely used in specific fields such as electric vehicles, household appliances, the aviation industry, and industrial automation equipment. However, the unique magnetic circuit saturation effect, strong non-linear characteristics, and pulse power supply mode of switched reluctance motors make their drive systems present complex fault coupling characteristics when there are faults in the power converter (such as IGBT open circuit / short circuit, freewheeling diode failure) and winding faults (turn-to-turn short circuit, phase-to-phase short circuit), which poses a severe challenge to their online fault diagnosis technology.

[0003] In the prior art, the fault diagnosis method based on current signal analysis has become a research hotspot because it directly reflects the working state and health condition of the motor drive system. The traditional scheme usually adopts the method of configuring three current sensors in the motor winding circuit, but this architecture has significant technical limitations: First, for the three-phase asymmetric half-bridge power converter supporting a typical three-phase switched reluctance motor, it consists of 12 independent current branches composed of 6 IGBT power switching tubes and 6 freewheeling diodes. However, the existing sensor arrangement can only obtain the total current information of the three-phase windings, and cannot directly observe the current behavior characteristics of each branch where the power devices are located, resulting in some device faults not being monitored, or the fault monitoring taking a long time, affecting the operation of the entire electric drive system; Second, when a single-branch component fault occurs, the fault characteristic signal will be masked by the current of the normal branch, resulting in insufficient sensitivity of the existing method to early weak faults and difficulty in accurately locating the fault component. Therefore, the prior art solutions often need to configure current sensors separately for each power branch, which will lead to a significant additional increase in equipment cost and weight. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems existing in the prior art, and provides a multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior. By changing the installation position of the sensors without increasing the number of current sensors, each power device of the drive circuit can be monitored in real time. At the same time, a multi-fault diagnosis method combined with the installation method is proposed. By measuring and calculating the current behavior in real time, the health condition of the drive system is judged, so as to realize fast fault diagnosis and location.

[0005] To achieve the above purpose, the technical solution provided by the present invention is:

[0006] A multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior is provided, including the following steps:

[0007] Step 1, install a first current sensor, a second current sensor, and a third current sensor in the switched reluctance motor drive system; wherein, each phase drive circuit of the switched reluctance motor is composed of a winding branch LA, LB, LC, and two half-bridge power device branches on both sides. An H-bridge is formed by two switching tubes and two power diodes on both sides of each phase. Each phase includes a left-side switching tube branch xLH, a left-side power diode branch xLL, a right-side switching tube branch xRL, and a right-side power diode branch xRH, where x represents the phase A, B, or C;

[0008] The first current sensor is connected across the common node of the right-side switching tube branch CRL of phase C, the winding branch LA of phase A, and the left-side switching tube branch BLH of phase B to monitor its synthesized current; the second current sensor is connected across the common node of the right-side switching tube branch ARL of phase A, the winding branch LB of phase B, and the left-side switching tube branch CLH of phase C to monitor its synthesized current; the third current sensor is connected across the common node of the right-side switching tube branch BRL of phase B, the winding branch LC of phase C, and the left-side switching tube branch ALH of phase A to monitor its synthesized current;

[0009] Step 2, collect the current values measured by the first current sensor, the second current sensor, and the third current sensor, and solve the winding phase current values according to the collected current sensor current values;

[0010] Step 3, set current sensor fault diagnosis variables according to the collected current sensor current values, and judge whether the first current sensor, the second current sensor, and the third current sensor are abnormal based on the current sensor fault diagnosis variables. If it is determined that there may be an abnormality, execute Step 4; if it is determined that there is no abnormality, execute Step 5;

[0011] Step 4, continuously monitor the current sensor fault diagnosis variables at two moments. If both are values close to zero, it is determined that a current sensor fault has occurred, and proceed to Step 8. If the values close to zero do not continuously appear, it is determined that no current sensor fault has occurred, and execute Step 5;

[0012] Step 5, set phase current fault diagnosis variables according to the solved winding phase current values, and judge whether the first current sensor, the second current sensor, and the third current sensor are abnormal based on the phase current fault diagnosis variables. If it is determined that there is an abnormality, execute Step 6; if it is determined that there is no abnormality, execute Step 7;

[0013] Step 6: Determine whether the phase current fault diagnosis variable at the next moment is normal. If it is normal, it is determined that a diode open circuit fault has occurred, and proceed to Step 8. If it is still abnormal, it is determined that a winding open circuit fault has occurred, and proceed to Step 8;

[0014] Step 7: Set the switching tube branch current fault diagnosis variable according to the current values measured by the current sensors and the solved winding phase current values, and determine whether a switching tube branch current fault has occurred based on the switching tube branch current fault diagnosis variable. If a switching tube open circuit or short circuit fault occurs, execute Step 8. If no fault occurs, return to Step 2 to continue the fault diagnosis;

[0015] Step 8: Output the fault diagnosis result.

[0016] Furthermore, in Step 2, the winding phase current is solved according to the following sub-steps:

[0017] Step 2.1: Establish the current equations measured by the first current sensor, the second current sensor, and the third current sensor:

[0018]

[0019] In the formula, are the phase currents of the three-phase windings respectively, and i1, i2, and i3 are the measured values of the first current sensor, the second current sensor, and the third current sensor respectively, are the conduction states of the switching tubes S1, S2, S3, S4, S5, and S6 respectively;

[0020] Step 2.2: Solve the winding phase current according to the established current equations:

[0021] .

[0022] Furthermore, 、 、 、 、 、 are determined as follows:

[0023]

[0024] In the formula, m = 、 、 、 、 、 .

[0025] Furthermore, in Step 3, the current sensor fault diagnosis variable is set as follows:

[0026]

[0027] In the formula, and are the current values at the k-th moment and the (k - 1)-th moment collected by the j-th current sensor respectively, where j = 1, 2, 3;

[0028] The abnormal judgment process is as follows: If the current sensor fault diagnosis variable is less than , being the error coefficient, it is determined that the current sensor may be abnormal. If the current sensor fault diagnosis variable is greater than or equal to , it is determined that the current sensor is normal.

[0029] Furthermore, in step 5, the phase current fault diagnosis variable is set as follows:

[0030]

[0031] In the formula, and represent the phase current values of the p-phase at the k-th moment and the (k - 1)-th moment respectively, where p = A, B, C;

[0032] The abnormal judgment process is as follows: When the phase current sensor fault diagnosis variable is less than , being the error coefficient, it is judged that the current sensor is abnormal. If the phase current sensor fault diagnosis variable is greater than or equal to , it is determined that the current sensor is normal.

[0033] Furthermore, in step 7, the switch tube branch current fault diagnosis variable is set as the difference between the actual branch current fault diagnosis variable and the theoretical branch current fault diagnosis variable :

[0034]

[0035]

[0036]

[0037] In the formula, and represent the switching signals of the n-th switch tube of the p-phase at the k-th moment and the (k - 1)-th moment respectively, and represent the phase current values of the p-phase at the k-th moment and the (k - 1)-th moment respectively, and They are the current values at time k and k - 1 collected by the j-th current sensor respectively, where p = A, B, C, n = 1, 2, j = 1, 2, 3 and the values are as follows:

[0038]

[0039] The fault judgment process is as follows: When the fault diagnosis variable of the switch tube branch current is less than , is the error coefficient, then it is determined that a short circuit fault of the switch tube has occurred. If the fault diagnosis variable of the switch tube branch current is greater than , then it is determined that an open circuit fault of the switch tube has occurred. If the fault diagnosis variable of the switch tube branch current is greater than or equal to and less than or equal to , then it is determined that there is no fault in the switch tube branch current.

[0040] The advantages of the present invention are:

[0041] The multi-fault diagnosis method for switched reluctance motor drive systems based on current behavior proposed by the present invention, without increasing the number of sensors while using the three inherent current sensors of the motor, only by changing the measurement path of each sensor and the number of measured current branches, realizes the real-time monitoring of the health status of each sensor, multiple branches and motor windings, and can diagnose and locate multiple fault types, including current sensor faults, winding open circuit faults, power diode open circuit faults, and switch tube open circuit and short circuit hybrid faults. Therefore, the present invention does not require any additional hardware, does not depend on the control method, and can quickly judge the health status of the motor drive system only by real-time measurement and calculation of the current behavior, and has a strong diagnostic function, can simultaneously diagnose 12 faults of 6 fault types, realize fast fault diagnosis and location, and greatly improve the diagnostic accuracy and speed. Description of the Drawings

[0042] Through the following description with reference to the drawings, the above and / or other features and advantages of the present invention will become more readily understood. In the drawings:

[0043] Figure 1 is the installation diagram of the current sensor for the current reconstruction technology in the present invention;

[0044] Figure 2 is the flow chart of the fault diagnosis method proposed by the present invention;

[0045] Figure 3 are the current reconstruction experimental results under two steady-state conditions. (a) is the experimental waveform under no-load conditions at 300 r / min, and (b) is the experimental waveform under 1 Nm at 500 r / min;

[0046] Figure 4Experimental results of current reconstruction under two transient conditions. (a) Experimental waveforms under sudden change of rotational speed, 300 - 800 r / min, no-load condition; (b) Experimental waveforms under sudden change of load, 500 r / min, 0 - 0.8 Nm condition.

[0047] Figure 5 Experimental results of single open-circuit fault diagnosis of switch S1. (a) Experimental waveforms under 300 r / min, 0.2 Nm condition; (b) Experimental waveforms under 800 r / min, 1 Nm condition.

[0048] Figure 6 Experimental results of double open-circuit fault diagnosis of switches S1 and S2. (a) Experimental waveforms under 300 r / min, 0.2 Nm condition; (b) Experimental waveforms under 800 r / min, 1 Nm condition.

[0049] Figure 7 Experimental results of single short-circuit fault diagnosis of switch S1. (a) Experimental waveforms under 300 r / min, 0.2 Nm condition; (b) Experimental waveforms under 800 r / min, 1 Nm condition.

[0050] Figure 8 Experimental results of double short-circuit fault diagnosis of switches S1 and S2. (a) Experimental waveforms under 300 r / min, 0.2 Nm condition; (b) Experimental waveforms under 800 r / min, 1 Nm condition.

[0051] Figure 9 Experimental results of open-circuit and short-circuit hybrid fault diagnosis.

[0052] Figure 10 Experimental results of winding open-circuit fault diagnosis.

[0053] Figure 11 Experimental results of diode open-circuit fault diagnosis.

[0054] Figure 12 Experimental results of current sensor fault diagnosis. Specific implementation manners

[0055] The present invention will be described in detail below with reference to the accompanying drawings by means of exemplary embodiments of the present invention. It should be noted that the following detailed description of the present invention is for illustrative purposes only and does not limit the present invention.

[0056] Aiming at the problems in the fault diagnosis of switched reluctance motor drive systems, such as the unmeasurability of some device faults, high-cost sensor dependence, poor real-time performance and sensitivity, this invention proposes a multi-fault diagnosis method for switched reluctance motor drive systems based on current behavior, which is applicable to asymmetric half-bridge power converters. Without increasing the number of sensors, this method only reselects the installation positions of the current sensors, changes the measurement paths of each sensor and the number of current branches to be measured, accurately reconstructs the three-phase phase current values, and can realize the real-time monitoring of the health status of each sensor, multiple branches and motor windings inside the switched reluctance motor drive system. After a fault occurs, there is a large deviation between the monitored current value of the corresponding device and the theoretical current value. By analyzing this current deviation behavior, various component faults of the switched reluctance motor drive system can be diagnosed and accurately located.

[0057] Referring to Figure 1 , in the multi-fault diagnosis method for switched reluctance motor drive systems based on current behavior provided by this invention, the first step S1 is to install the first sensor, the second sensor and the third sensor in the switched reluctance motor drive system according to the method shown in this figure (corresponding to the current sensors "CURRENT SENSOR" 1, 2 and 3 in Figure 1 respectively).

[0058] As Figure 1 shown, each phase drive circuit of the switched reluctance motor consists of winding branches L A , L B , L C , and the half-bridge power device branches on both sides. The two switching tubes and two power diodes on both sides of each phase form an H-bridge. The switching tubes are S1, S2, S3, S4, S5 and S6, and the power diodes are D1, D2, D3, D4, D5 and D6. Each phase includes a left-side switching tube branch xLH, a left-side power diode branch xLL, a right-side switching tube branch xRL, and a right-side power diode branch xRH, where x represents the phase A, B or C.

[0059] The first current sensor is connected across the common node of the right-side switching tube branch CRL of phase C, the winding branch LA of phase A, and the left-side switching tube branch BLH of phase B to monitor its synthesized current; the second current sensor is connected across the common node of the right-side switching tube branch ARL of phase A, the winding branch LB of phase B, and the left-side switching tube branch CLH of phase C to monitor its synthesized current; the third current sensor is connected across the common node of the right-side switching tube branch BRL of phase B, the winding branch LC of phase C, and the left-side switching tube branch ALH of phase A to monitor its synthesized current.

[0060] Referring to Figure 2, Next, start the fault diagnosis. First, in step S2, collect the current values measured by three current sensors, and according to the current sensor installation method in step S1, the current equations measured by the three current sensors can be established as follows:

[0061] (1)

[0062] In the formula, , , are the phase currents of the three-phase windings respectively, and i1, i2, and i3 are the measured values of the first current sensor, the second current sensor, and the third sensor respectively. , , , , , are the conduction conditions of the switching tubes S1, S2, S3, S4, S5, and S6 respectively, and their conduction and cutoff amplitudes are as follows:

[0063] (2)

[0064] where m = , , , , , .

[0065] Thus, the following solution results can be obtained by reconstructing the three-phase current:

[0066] (3)

[0067] Then, in step S3, set the current sensor fault diagnosis variable according to the current values of the current sensors collected:

[0068] (4)

[0069] where, is the current value at the kth moment collected by the jth (j = 1, 2, 3) current sensor, is the current value at the (k - 1)th moment collected by the jth current sensor.

[0070] When the current sensor fault diagnosis variable is less than , where is the error coefficient set considering environmental influences such as sampling errors, and its value is in [0, 1], it is determined that the current sensor may be abnormal, and proceed to step S4. When the current sensor fault diagnosis variable is greater than or equal to , it is determined that the current sensor is not abnormal, and step S5 is performed.

[0071] Step S4 is as follows: Continuously monitor the current sensor fault diagnosis variables at two moments. If both are values close to zero, it is determined that a current sensor fault has occurred, and go to step S8. If values close to zero do not continuously appear, it is determined that no current sensor fault has occurred, and step S5 is performed;

[0072] Step S5 is as follows: Set the phase current fault diagnosis variable according to the solved winding phase current value:

[0073] (5)

[0074] where and respectively represent the phase current values of phase p (p = A, B, C) at the k-th moment and the (k - 1)-th moment.

[0075] When the phase current fault diagnosis variable is less than where is an error coefficient set considering environmental influences such as sampling errors and is a value in [0, 1], it is determined that the current sensor is abnormal, and step S6 is performed. If the phase current fault diagnosis variable is greater than or equal to , it is determined that the current sensor is not abnormal, and step S7 is performed.

[0076] Step S6 is as follows: Determine whether the phase current fault diagnosis variable at the next moment is normal. If it is normal, it is determined that a diode open circuit fault has occurred, and step S8 is performed. If it is still abnormal, it is determined that a winding open circuit fault has occurred, and step S8 is also performed;

[0077] Step S7 is as follows: Set the fault diagnosis variables of each switching tube according to the current value of the current sensor collected and the solved winding phase current value, that is, the branch current fault diagnosis variable , which consists of two parts, namely the theoretical branch current fault diagnosis variable and the actual branch current fault diagnosis variable :

[0078] (6)

[0079] (7)

[0080] where and respectively represent the switching signals of the n-th (n = 1, 2) switching tubes of phase p (p = A, B, C) at the k-th moment and the (k - 1)-th moment, and are the current values at time k and time k-1 collected by the j-th current sensor respectively. In the formula j takes values according to the following table:

[0081]

[0082] The branch current fault diagnosis variable is:

[0083] (8)

[0084] Whether a fault occurs can be judged according to the difference between the actual branch current fault diagnosis variable and the theoretical branch current fault diagnosis variable. When is less than , where is an error coefficient set considering environmental influences such as sampling errors and is a value in [0, 1], it can be determined that a switch tube short-circuit fault has occurred. When is greater than it can be judged that a switch tube open-circuit fault has occurred, and step S8 is entered. If is greater than or equal to and less than or equal to , it is determined that there is no switch tube branch current fault, and step 2 is returned to continue fault diagnosis;

[0085] Finally, in step S8, the fault diagnosis result is output, that is, all fault types and fault points are output.

[0086] Therefore, as described above, the present invention does not require any additional hardware. Only three inherent current sensors of the motor are used. It does not depend on the control method. Only by changing the measurement path of each sensor and the number of measured current branches, and measuring and calculating the current behavior in real time, the real-time monitoring of the health status of each sensor, multiple branches and motor windings in the drive system is realized. In only 1 control cycle (the fault diagnosis variable is set for time k and time k-1 in the switch tube fault, which reflects one control cycle), 2 control cycles (the next moment in the diode open-circuit fault diagnosis in step S6 and the winding fault detection reflects two control cycles), 4 control cycles (the current sensor fault detection reflects four control cycles), the health status of the motor drive system can be quickly judged, and the diagnosis function is strong. 12 faults of 6 fault types can be diagnosed simultaneously, namely current sensor fault, winding open-circuit fault, power diode open-circuit fault and switch tube open-circuit short-circuit hybrid fault, realizing the rapid fault diagnosis and location of the switched reluctance motor drive system, and greatly improving the diagnosis accuracy and diagnosis speed.

[0087] Next, the multi-fault diagnosis method for the switched reluctance motor drive system based on current behavior provided by the present invention is further described in combination with an example, and the proposed method is verified through a large number of experiments.

[0088] In this instance, after installing three current sensors according to the above description, the fault diagnosis of the switched reluctance motor drive system is started.

[0089] Figure 3 In (a), the waveforms of the actual current and the reconstructed current are shown under no-load conditions at 300 r / min, and in (b), the actual current and the reconstructed current are shown under load conditions of 800 r / min and 1 Nm. It can be seen that the reconstructed current and the actual current can match well, verifying the accuracy of the current reconstruction method proposed by the present invention.

[0090] Figure 4 In (a), the waveforms of the actual current and the reconstructed current are shown under transient speed conditions, and in (b), the waveforms of the actual current and the reconstructed current are shown under transient load conditions. It can be seen that whether under transient speed conditions or under transient load conditions, the reconstructed current is consistent with the actual phase current, verifying that the proposed current reconstruction method has good robustness.

[0091] Figure 5 In (a) and (b), when an open-circuit fault suddenly occurs under conditions of 300 r / min, a load of 0.2 Nm and 800 r / min, a load of 1 Nm, the theoretical current diagnosis variable and the actual current diagnosis variable quickly become abnormal after the fault occurs. At the same time, the theoretical diagnosis variable is less than the actual diagnosis variable, then it is diagnosed that an open-circuit fault has occurred, and the location where the fault occurs is determined.

[0092] Figure 6 In (a), it is the experimental waveform diagram at 300 r / m and 0.2 Nm. After an open-circuit fault occurs in two switching tubes, the fault diagnosis variables of the corresponding devices will have a large difference from the theoretical variables, thus realizing the fault diagnosis. Similarly, in Figure 6 In (b) shown, when the load is 800 r / min and 1 Nm, the two switching tube faults set can also realize the diagnosis function.

[0093] Figure 7 In (a) and (b), when a short-circuit fault suddenly occurs under conditions of 300 r / min with a load of 0.2 Nm and 800 r / min with a load of 1 Nm, the theoretical current diagnosis variable and the actual current diagnosis variable quickly become abnormal after the fault occurs. At the same time, the theoretical diagnosis variable is greater than the actual diagnosis variable, then it is diagnosed that a short-circuit fault has occurred, and the location where the fault occurs is determined.

[0094] Figure 8In (a), it is the experimental waveform diagram at 300 r / m and 0.2 Nm. After open-circuit faults occur in two switching tubes, the fault diagnosis variables of the corresponding devices will have a large difference from the theoretical variables, thus realizing the fault diagnosis. Similarly, in Figure 8 under the load condition of 800 r / min and 1 Nm shown in (b), the two switching tube faults set can also achieve the diagnosis function.

[0095] Figure 9 In, set the S1 tube in phase A to have an open-circuit fault and the S2 tube to have a short-circuit fault, and conduct experimental verification under the conditions of 800 rpm and 1 Nm load. As Figure 9 shown, when an open-circuit fault occurs in S1, the corresponding open-circuit fault anomaly will appear in the S1 diagnosis variable. Similarly, a short-circuit fault anomaly will appear in the S2 diagnosis variable.

[0096] From Figure 10 it can be seen that after setting an open-circuit in the winding of phase A, the current value will continuously remain 0. In order to distinguish between the winding open-circuit fault and the diode open-circuit fault, all the switching devices of the asymmetric half-bridge where it is located will be turned on at the moment when the phase current becomes zero, but the phase current does not increase, and it is judged that an open-circuit fault has occurred in the winding.

[0097] From Figure 11 it can be seen that after setting an open-circuit fault in D1, the phase current will quickly drop to 0 within one control cycle. After one cycle is turned on, the current increases, indicating that it is not a winding open-circuit fault. After continuously turning on for two control cycles and turning off S1, the current becomes 0 at the next moment, indicating that the fault point is at D1, thus realizing the diagnosis and location of the diode open-circuit fault.

[0098] Figure 12 In, set a sudden current sensor fault under no-load conditions at 500 rpm. When the fault occurs, the current changes from the normal value to 0. Therefore, the fault diagnosis variable set for the current sensor will become zero at the next moment, thus realizing the diagnosis and location of the current sensor fault. Thus, this example verifies that the method proposed by the present invention can quickly judge the health status of the motor drive system within only 1, 2, 4 control cycles, and can accurately diagnose 12 faults of 6 fault types at the same time, greatly improving the fault diagnosis accuracy and diagnosis speed.

[0099] Finally, it should be noted that the features mentioned and / or shown in the above description of the exemplary embodiments of the present invention can be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or replace the corresponding features in other embodiments. The technical solutions obtained by such combination or replacement should also be regarded as being included within the protection scope of the present invention.

Claims

1. A multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior, characterized in that The method includes the following steps: Step 1: Install a first current sensor, a second current sensor, and a third current sensor in the switched reluctance motor drive system. Each phase drive circuit of the switched reluctance motor consists of a winding branch LA, LB, LC, and two half-bridge power device branches on both sides. An H-bridge is formed by two switching tubes and two power diodes on both sides of each phase. Each phase includes a left switching tube branch xLH, a left power diode branch xLL, a right switching tube branch xRL, and a right power diode branch xRH, where x represents the phase A, B, or C. The first current sensor is connected across the common node of the right switching tube branch CRL of phase C, the winding branch LA of phase A, and the left switching tube branch BLH of phase B to monitor the synthesized current. The second current sensor is connected across the common node of the right switching tube branch ARL of phase A, the winding branch LB of phase B, and the left switching tube branch CLH of phase C to monitor the synthesized current. The third current sensor is connected across the common node of the right switching tube branch BRL of phase B, the winding branch LC of phase C, and the left switching tube branch ALH of phase A to monitor the synthesized current. Step 2: Collect the current values measured by the first current sensor, the second current sensor, and the third current sensor, and solve for the winding phase current values based on the collected current sensor current values. Step 3: Set a current sensor fault diagnosis variable based on the collected current sensor current values, and determine whether the first current sensor, the second current sensor, and the third current sensor are abnormal based on the current sensor fault diagnosis variable. If it is determined that there may be an abnormality, go to Step 4; if it is determined that there is no abnormality, go to Step 5. Step 4: Continuously monitor the current sensor fault diagnosis variable at two consecutive moments. If both values are close to zero, it is determined that a current sensor fault has occurred, and proceed to Step 8. If the values close to zero do not continuously appear, it is determined that no current sensor fault has occurred, and execute Step 5. Step 5: Set a phase current fault diagnosis variable based on the solved winding phase current values, and determine whether the first current sensor, the second current sensor, and the third current sensor are abnormal based on the phase current fault diagnosis variable. If it is determined that there is an abnormality, go to Step 6; if it is determined that there is no abnormality, go to Step 7. Step 6: Determine whether the phase current fault diagnosis variable at the next moment is normal. If it is normal, it is determined that a diode open circuit fault has occurred, and proceed to Step 8. If it is still abnormal, it is determined that a winding open circuit fault has occurred, and proceed to Step 8. Step 7: Set a switching tube branch current fault diagnosis variable based on the collected current sensor current values and the solved winding phase current values, and determine whether a switching tube branch current fault has occurred based on the switching tube branch current fault diagnosis variable. If a switching tube open circuit or short circuit fault occurs, execute Step 8. If no fault occurs, return to Step 2 to continue the fault diagnosis. Step 8: Output the fault diagnosis result.

2. The multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior according to claim 1, wherein In Step 2, the winding phase current is solved according to the following sub-steps: Step 2.1, establish the current equations measured by the first current sensor, the second current sensor, and the third current sensor: Wherein, , , are the phase currents of the three-phase windings respectively, and i1, i2, and i3 are the measured values of the first current sensor, the second current sensor, and the third current sensor respectively, , , , , , are the turn-on conditions of the switching transistors S1, S2, S3, S4, S5, and S6 respectively; Step 2.2, solve the winding phase current according to the established current equations: 。 3. The multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior according to claim 2, wherein , , , , , The value is determined as follows: Where m = , , , , , .

4. The multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior according to claim 1 or 2, characterized in that In step 3, the current sensor fault diagnosis variables are set as follows: In the formula, and are the current values at the k-th moment and the (k - 1)-th moment collected by the j-th current sensor respectively, where j = 1, 2, 3; The abnormal judgment process is as follows: If the fault diagnosis variable of the current sensor is less than , is the error coefficient, it is determined that the current sensor may be abnormal. If the fault diagnosis variable of the current sensor is greater than or equal to , it is determined that the current sensor is normal.

5. The multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior according to claim 1 or 2, characterized in that, In step 5, the phase current fault diagnosis variables are set as follows: Wherein, and respectively represent the phase current values of phase p at time k and time k-1, where p = A, B, C; The abnormal judgment process is as follows: When the fault diagnosis variable of the phase current sensor is less than , is the error coefficient, then it is judged that the current sensor is abnormal. If the fault diagnosis variable of the phase current sensor is greater than or equal to , it is determined that the current sensor is normal.

6. The multi-fault diagnosis method for a switched reluctance motor drive system based on current behavior according to claim 1 or 2, characterized in that, In step 7, the switching transistor branch current fault diagnosis variable is set as the difference between the actual branch current fault diagnosis variable and the theoretical branch current fault diagnosis variable : Wherein, and respectively represent the switching signals of the nth switching device of phase p at the kth moment and the (k - 1)th moment, and respectively represent the phase current values of phase p at the kth moment and the (k - 1)th moment, and are respectively the current values at the kth moment and the (k - 1)th moment collected by the jth current sensor, where p = A, B, C, n = 1, 2, j = 1, 2, 3 and the values are as follows: The fault judgment process is as follows: When the fault diagnosis variable of the switch tube branch current is less than , is the error coefficient, then it is determined that a short-circuit fault of the switch tube has occurred. If the fault diagnosis variable of the switch tube branch current is greater than , then it is determined that an open-circuit fault of the switch tube has occurred. If the fault diagnosis variable of the switch tube branch current is greater than or equal to and less than or equal to , then it is determined that there is no fault in the switch tube branch current.

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