SRM switching transistor short circuit fault diagnosis method based on new connection method of current sensor

Abstract

The application discloses a SRM switching tube short circuit fault diagnosis method based on a new connection method of a current sensor, and belongs to the field of switched reluctance motor control. According to the method, each phase current sensor is installed in a specific way, so that the size of the detected current is changed, and the sign and the numerical value of the measured value of the current sensor are used as fault monitoring variables, and a power switching tube short circuit fault judgment criterion of an asymmetric half-bridge power converter is formulated. The power switching tube short circuit fault diagnosis method has low requirements on hardware, can operate under dynamic conditions, is easy to implement, has the advantages of low cost, high precision and fast response speed. The installation mode of the current sensor does not affect the measurement of the actual current of each phase of the motor during normal operation, and can be applied to switched reluctance motors with different pole numbers.

Description

Technical Field

[0001] This invention belongs to the field of switched reluctance motor control technology, and particularly relates to a method for diagnosing short-circuit faults of SRM switching transistors based on a new connection method of current sensor. Background Technology

[0002] Switched reluctance motors (SRMs) possess a range of advantages, including simple structure, low cost, high reliability, and good speed regulation, making them widely used in electric vehicles, home appliances, and aerospace. A typical SRM power topology is an asymmetric half-bridge, where each arm requires two freewheeling diodes and two switching transistors for control. A short-circuit fault in one of these transistors can disrupt the motor's normal operation and potentially lead to serious accidents and significant economic losses. Rapid diagnosis of short-circuit faults in the switching transistors can improve system reliability. However, online diagnosis of short-circuit faults in switching transistors suffers from diagnostic lag, misdiagnosis, and high equipment costs. Existing research, largely employing complex diagnostic algorithms, suffers from long diagnostic lag times, high complexity, and expensive equipment. Therefore, timely diagnosis and location of the faulty switching transistor is essential. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a convenient and highly accurate method for diagnosing short-circuit faults in the switching transistor of a switched reluctance motor based on a new connection method of a current sensor.

[0004] Technical Solution: This invention provides a method for diagnosing short-circuit faults in SRM switching transistors based on a novel connection method for current sensors. Based on a switched reluctance motor and its asymmetrical half-bridge power converter, and taking each phase as the target phase, the method achieves real-time diagnosis of short-circuit faults in the target phase switching transistors through the following steps:

[0005] Step 1: Based on whether the short circuit fault of the target phase switch tube occurs in the conducting state or the non-conducting state, the diagnostic strategy is divided into fault diagnosis of switch tube in the conducting area and fault diagnosis of switch tube in the non-conducting area.

[0006] Step 2: Based on the acquisition of the target phase current value, and combined with the preset chopping upper and lower thresholds of the target phase conduction region, current chopping control of the target phase is achieved; the lower switch of the target phase conduction region is kept on, and when the target phase current value rises to the chopping upper threshold, the upper switch of the target phase is turned off to reduce the target phase current value; when the target phase current value drops to the chopping lower threshold, the upper switch of the target phase is turned on to increase the target phase current value.

[0007] Step 3: After the current chopping control of the target phase, if the position signal detects that the target phase is in the conducting region, the fault diagnosis of the switching transistor in the conducting region is adopted, and the process jumps to step 4. If the target phase is detected to be in the non-conducting region, the fault diagnosis of the switching transistor in the non-conducting region is adopted, and the process jumps to step 5.

[0008] Step 4: Use the dual current limiting value test method to diagnose the short circuit fault of the switching transistor in the conducting region;

[0009] Step 5: Detect the current sensor readings in the non-conducting area and perform differential analysis to check for short circuit faults. Then, perform a switching transistor continuity test to diagnose short circuit faults in the switching transistor in that area.

[0010] Furthermore, the three-phase motor includes a power converter, an A-phase winding, a B-phase winding, and a C-phase winding; the power converter is an asymmetrical half-bridge power converter, including a DC bus capacitor c, diodes, and switching transistors; the switching transistors include switching transistors S1, S2, S3, S4, S5, and S6, and the diodes include diodes D1, D2, D3, D4, D5, and D6; the positive terminal of the DC bus capacitor c is connected to one end of switching transistor S1, one end of switching transistor S3, one end of switching transistor S5, and the cathodes of diodes D1, D3, and D5, and is connected to an external DC power supply U. s The positive terminals of the capacitors are connected together, and the negative terminals of the DC bus capacitor c are connected to one end of the switching transistor S2, one end of the switching transistor S4, one end of the switching transistor S6, and the anodes of the diodes D2, D4, and D6, respectively, and are connected to the external DC power supply U. s The negative terminals are connected together; the current sensor includes current sensor CS1, current sensor CS2, and current sensor CS3;

[0011] The current sensor has three wires passing through it. One end of the first wire is connected to the upper switch in the corresponding target phase and passes through the current sensor in the positive direction to connect to one end of the target phase winding. One end of the second wire in the current sensor is connected to the cathode of the diode in the corresponding target phase and passes through the current sensor in the negative direction to connect to the same end of the target phase winding. One end of the third wire in the current sensor is connected to the anode of the diode in the corresponding target phase and passes through the current sensor in the positive direction to connect to the other end of the target phase winding.

[0012] Furthermore, the specific steps of step 1 are as follows:

[0013] Step 1-1: Classify the short-circuit fault types of the switching transistor as follows:

[0014] Based on the motor's operating status and the switching status, the areas where short-circuit faults occur are divided into conducting and non-conducting regions. Based on the type of switching transistor, short-circuit faults are further categorized into upper transistor short circuit, lower transistor short circuit, and double transistor short circuit. Therefore, a total of six fault types can be identified: upper transistor short circuit in conducting region, lower transistor short circuit in conducting region, double transistor short circuit in conducting region, upper transistor short circuit in non-conducting region, lower transistor short circuit in non-conducting region, and double transistor short circuit in non-conducting region. Thus, if a short-circuit fault occurs in phase A, there are a total of six possible short-circuit fault scenarios: short circuit of chopper transistor S1 in conducting region, short circuit of chopper transistor S1 in non-conducting region, short circuit of conducting transistor S2 in conducting region, short circuit of conducting transistor S2 in non-conducting region, double transistor short circuit in conducting region, and double transistor short circuit in non-conducting region. Therefore, there are a total of 18 possible short-circuit faults in the switching transistors of a three-phase 12 / 8 switched reluctance motor power converter. The following are examples of short circuits: A-phase chopper S1 short circuit in the conducting region; A-phase chopper S1 short circuit in the non-conducting region; A-phase conducting tube S2 short circuit in the conducting region; A-phase conducting tube S2 short circuit in the non-conducting region; A-phase dual tube short circuit in the conducting region; A-phase dual tube short circuit in the non-conducting region; B-phase chopper S3 short circuit in the conducting region; B-phase chopper S3 short circuit in the non-conducting region; B-phase conducting tube S4 short circuit in the conducting region. A short circuit occurs in the following situations: Phase B conducting tube S4 short circuit in the non-conducting area; Phase B dual tube short circuit in the conducting area; Phase B dual tube short circuit in the non-conducting area; Phase C chopper tube S5 short circuit in the conducting area; Phase C chopper tube S5 short circuit in the non-conducting area; Phase C conducting tube S6 short circuit in the conducting area; Phase C conducting tube S6 short circuit in the non-conducting area; Phase C dual tube short circuit in the conducting area; Phase C dual tube short circuit in the non-conducting area.

[0015] Step 1-2: Simplify the short-circuit fault types of the switching transistor, as follows:

[0016] Based on the current waveform analysis, it is concluded that since the conductor is always in the open state in the conducting region, the short circuit fault that occurs at this time will not affect the current change trend at the moment of the short circuit. The short circuit fault will affect the current in the non-conducting region. Therefore, the short circuit in the conducting region and the short circuit in the non-conducting region can be combined into a short circuit in the non-conducting region.

[0017] Steps 1-3: Summarize the types of short-circuit faults in the switching transistor, as follows:

[0018] The 18 types of short-circuit faults can be simplified to 15: Short circuit in the upper tube of phase A in the conducting region (Fault I), Short circuit in both tubes of phase A in the conducting region (Fault II), Short circuit in the upper tube of phase A in the non-conducting region (Fault IV), Short circuit in the lower tube of phase A in the non-conducting region (Fault III), and Short circuit in both tubes of phase A in the non-conducting region (Fault V). Fault V, Short circuit in the conducting area of ​​phase B chopper S3 - Fault I, Short circuit in the non-conducting area of ​​phase B chopper S3 - Fault IV, Short circuit in phase B conducting tube S4 - Fault III, Short circuit in the conducting area of ​​phase B dual tubes - Fault II, Short circuit in the non-conducting area of ​​phase B dual tubes - Fault V, Short circuit in the conducting area of ​​phase C chopper S5 - Fault I, Short circuit in the non-conducting area of ​​phase C chopper S5 - Fault IV, Short circuit in the non-conducting area of ​​phase C conducting tube S6 - Fault III, Short circuit in the conducting area of ​​phase C dual tubes - Fault II, Short circuit in the non-conducting area of ​​phase C dual tubes - Fault V.

[0019] Furthermore, the specific steps of step 2 are as follows:

[0020] Assuming the target phase current is i when all switches are operating normally a When the upper and lower switching transistors S1 and S2 are turned on, the phase current measurement value is i. a When the upper switch S1 is on and the lower switch S2 is off, the phase current measurement is 0; when the upper switch S1 is off and the lower switch S2 is on, the phase current measurement is -i. a When both upper and lower switching transistors S1 and S2 are turned off, the measured phase current value is -2i. a This distinguishes the different circuits through which the current flows. At the same time, by multiplying the current measurement value in the non-conducting region by a coefficient of -0.5 and processing the absolute value of the measurement value in the conducting region, the winding current waveform during normal motor operation is reconstructed.

[0021] Furthermore, the specific steps of step 4 are as follows:

[0022] Step 4-1: Set a current limit value i that is numerically greater than the chopper upper limit threshold. th1 i th2 , where i th1 For the first current limit value, i th2 The second current limit value and i th1 Less than i th2 When the absolute value measured by the current sensor in the target phase conduction region exceeds the first current value limit i th1If the absolute value measured by the current sensor does not exceed the first current limit value, the upper and lower switches of the target phase are diagnosed as operating normally, and the process jumps to step 4-3.

[0023] Step 4-2: If the current exceeds the first current limit value during the conduction interval, the test phase begins. At this time, the upper and lower switches of the target phase are forcibly turned off. If the current decreases, the absolute value of the sensor detection value is less than the first current limit value i. th1 If the fault is diagnosed as fault I, proceed to step 4-3; if the current increases and the absolute value of the sensor detection value is greater than the second current limit value i th2 If so, the diagnosis is fault II, and the process jumps to step 4-3;

[0024] Step 4-3: This diagnosis is now complete. If the target phase is still in the conduction region, proceed to the next diagnosis. If the target phase enters the non-conductivity region, proceed to step 5.

[0025] Furthermore, in step 4-1, the first current limiting value i th1 Take 120% of the current chopping upper limit, and the second current limit value i th2 Set the current chopping limit to 140%.

[0026] Furthermore, the specific steps of step 5 are as follows:

[0027] Step 5-1: Real-time detection of sensor values ​​in the non-conductive area and differential calculation; if the absolute value of the value after differential processing is not greater than the preset threshold δ, the preset threshold δ is set to 120% of the current differential value when the motor is running normally, then the switch transistors S1 and S2 are diagnosed to be working normally and the process jumps to step 5-6; if the absolute value of the value after differential processing is greater than the preset threshold, then a short circuit fault is initially diagnosed in the switch transistors and the process jumps to step 5-2.

[0028] Step 5-2: Check if the sensor detection value is greater than 0; if the sensor detection value is greater than 0, determine fault V and jump to step 5-6; otherwise, jump to step 5-3;

[0029] Step 5-3: Enter the testing phase and turn on the lower switch S2; jump to step 5-4;

[0030] Step 5-4: During the testing phase, if the sensor detection value is greater than 0, fault IV is identified, and the process proceeds to step 5-6.

[0031] Step 5-5: During the testing phase, if the sensor detection value is less than or equal to 0, fault III is identified, and the process proceeds to step 5-6.

[0032] Steps 5-6: Output the diagnostic results, and this diagnosis ends; if the phase is still in the non-conductive region, proceed to the next diagnosis; if the phase enters the conductive region, jump to step 4.

[0033] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0034] (1) The diagnostic scheme of the present invention adjusts the installation method of the current sensor, classifies and summarizes the short circuit faults of the switching transistor, and uses different diagnostic methods in the conducting and non-conducting regions to quickly diagnose the short circuit faults of the switching transistor.

[0035] (2) While not affecting current detection, it can quickly diagnose short-circuit faults in the switching transistor. The controller can still obtain the actual phase current value through the current sensor. This diagnostic scheme is applicable to both current chopper control and APC angle control, and is not limited by the control method. This diagnostic scheme has good dynamic performance and can perform fault diagnosis in both steady-state and dynamic states. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the installation position of the current sensor used in this invention;

[0037] Figure 2 This is a schematic diagram of the current reconfiguration scheme;

[0038] Figure 3 This is a simplified diagram of fault classification;

[0039] Figure 4 This is the overall logic flowchart for short-circuit fault diagnosis;

[0040] Figure 5 This is a flowchart of the logic for diagnosing short-circuit faults in the conduction zone;

[0041] Figure 6 This is a flowchart of the logic for diagnosing short-circuit faults in the non-conductive zone. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0043] This invention presents a novel SRM (Short Circuit Reduction) switch short-circuit fault diagnosis method based on a new current sensor connection. Based on the fault characteristics of the phase current waveform corresponding to the short-circuit fault in each phase switch, it achieves real-time and rapid diagnosis of short-circuit faults in each phase switch. The motor employs single-tube current chopper control or single-pulse control. If the motor is under chopper control, in phase A, the upper switch S1 is set as the chopper and the lower switch S2 as the conducting switch; in phase B, the upper switch S3 is set as the chopper and the lower switch S4 as the conducting switch; and in phase C, the upper switch S5 is set as the chopper and the lower switch S6 as the conducting switch.

[0044] like Figure 1 As shown in the figure, this is a schematic diagram of the installation position of the current sensors used in this invention. The connection methods of each current sensor are as follows: The current sensor CS1 has three wires passing through it. One end of the first wire is connected to the upper switching transistor S1 and passes through the current sensor CS1 in the positive direction to connect to one end of the A-phase winding. One end of the second wire in sensor CS1 is connected to the cathode of diode D2 and passes through the current sensor in the negative direction to connect to the same end of the A-phase winding. One end of the third wire in sensor CS1 is connected to the anode of diode D1 and passes through the current sensor in the positive direction to connect to the other end of the A-phase winding. Since each phase of the asymmetrical half-bridge is independent, the connection methods of CS2 and CS3 are the same as CS1. The only difference is that the names of the upper and lower switching transistors are different. The specific wiring methods of CS2 and CS3 are described below. The current sensor CS2 has three wires passing through it. One end of the first wire is connected to the upper switching transistor S3 and passes through the current sensor CS2 in the positive direction to connect to one end of the B-phase winding. One end of the second wire in sensor CS2 is connected to the cathode of diode D4 and passes through the negative direction of the current sensor to connect to the same end of the B-phase winding. One end of the third wire in sensor CS2 is connected to the anode of diode D3 and passes through the positive direction of the current sensor to connect to the other end of the B-phase winding. Current sensor CS3 has three wires passing through it, with one end of the first wire connected to the upper switching transistor S5 and passing through the positive direction of current sensor CS3 to connect to one end of the C-phase winding. One end of the second wire in sensor CS3 is connected to the cathode of diode D6 and passes through the negative direction of the current sensor to connect to the same end of the C-phase winding. One end of the third wire in sensor CS3 is connected to the anode of diode D5 and passes through the positive direction of the current sensor to connect to the other end of the C-phase winding.

[0045] like Figure 2 As shown, this diagram illustrates the current reconstruction scheme. Taking phase A as an example, when the motor is running normally using this current sensor connection, the sensor measurement value i exists in the non-conducting region. csa For the actual winding current i a -2 times. To obtain the winding current when the motor is running normally, the following method is used: Figure 2 The current reconstruction method shown involves multiplying the current measurement value in the non-conducting region by a factor of -0.5, i.e., changing the original current sensor measurement value from -2i... a After numerical processing, it becomes i. a Furthermore, the absolute values ​​of the measured values ​​in the conduction range are processed to reconstruct the winding current waveform during normal motor operation. Therefore, this current sensor placement method does not affect the actual current measurement, and the winding current waveform during normal motor operation can be reconstructed through current reconstruction.

[0046] like Figure 3As shown, based on the different areas where short-circuit faults occur, they are divided into short-circuit faults occurring in the conducting region and short-circuit faults occurring in the non-conducting region. Combining these with the types of short-circuit faults, there are a total of 6 types. Taking phase A as an example, if a short-circuit fault occurs in phase A, there are 6 possible short-circuit fault scenarios: short circuit of chopper S1 in the conducting region, short circuit of chopper S1 in the non-conducting region, short circuit of conducting tube S2 in the conducting region, short circuit of conducting tube S2 in the non-conducting region, short circuit of both tubes in the conducting region, and short circuit of both tubes in the non-conducting region. Therefore, there are a total of 18 types of short-circuit faults in the switching transistors of the three-phase 12 / 8 switched reluctance motor power converter, namely: short circuit in the conducting region of phase A chopper S1, short circuit in the non-conducting region of phase A chopper S1, short circuit in the conducting region of phase A conductor S2, short circuit in the non-conducting region of phase A conductor S2, short circuit in the conducting region of phase A dual transistors, short circuit in the non-conducting region of phase A dual transistors, short circuit in the conducting region of phase B chopper S3, and short circuit in the non-conducting region of phase B chopper S3. The following are examples of short-circuit faults in switching transistors: Short circuit in the non-conducting region; Short circuit in the conducting region of phase B conducting transistor S4; Short circuit in the non-conducting region of phase B conducting transistor S4; Short circuit in the conducting region of phase B dual transistors; Short circuit in the non-conducting region of phase B dual transistors; Short circuit in the conducting region of phase C chopper transistor S5; Short circuit in the non-conducting region of phase C chopper transistor S5; Short circuit in the conducting region of phase C conducting transistor S6; Short circuit in the non-conducting region of phase C conducting transistor S6; Short circuit in the conducting region of phase C dual transistors; Short circuit in the non-conducting region of phase C dual transistors. To facilitate fault diagnosis, these 18 types of short-circuit faults in switching transistors are summarized. Based on the short-circuit current waveform characteristics of conducting transistor S2, it can be found that the fault characteristics of short-circuit faults in conducting transistor S2 are not obvious in the conducting region. Therefore, the two types of faults—short circuits in the conducting and non-conducting regions of the conductive tube S2—can be considered as one. That is, regardless of when a short circuit fault occurs in S2, it is considered to have occurred in the non-conducting region. Thus, the 18 types of short circuit faults can be simplified to 15 types, namely: short circuit in the conducting region of phase A chopper tube S1 (Fault I), short circuit in the non-conducting region of phase A chopper tube S1 (Fault IV), short circuit in phase A conductive tube S2 (Fault III), short circuit in the conducting region of phase A dual tubes (Fault II), short circuit in the non-conducting region of phase A dual tubes (Fault V), short circuit in the conducting region of phase B chopper tube S3 (Fault I), and short circuit in the non-conducting region of phase B chopper tube S3. Short circuit (Fault IV), short circuit of phase B conducting tube S4 (Fault III), short circuit of phase B dual tubes in the conducting region (Fault II), short circuit of phase B dual tubes in the non-conducting region (Fault V), short circuit of phase C chopper tube S5 in the conducting region (Fault I), short circuit of phase C chopper tube S5 in the non-conducting region (Fault IV), short circuit of phase C conducting tube S6 (Fault III), short circuit of phase C dual tubes in the conducting region (Fault II), short circuit of phase C dual tubes in the non-conducting region (Fault V). Simplifying fault types by analyzing the short-circuit current waveform characteristics greatly reduces the complexity of the diagnostic logic, making the diagnostic logic easier to implement and operate.

[0047] 1. The steps for distinguishing and simplifying short-circuit fault types are as follows:

[0048] In APC control mode, if a short-circuit fault occurs in the conducting zone, it will not affect motor operation because both the upper and lower switches of the conducting phase are on in this mode. However, if the fault extends into the non-conducting zone, it will affect normal motor operation. Therefore, if a short-circuit fault occurs in the conducting zone during APC angle control, it can be considered as the fault occurring in the non-conducting zone. However, CCC chopper control differs from APC control because the on / off state of the switches in the conducting zone is related to the winding current. Therefore, faults occurring in the conducting zone will also affect motor operation. The following analysis examines the changes in current sensor measurements under different modes for CCC control.

[0049] Under current chopper (CCC) control, assuming the upper switch S1 acts as the chopper and the lower switch S2 acts as the conductor, we first analyze the changes in phase A current under normal operating conditions.

[0050] Under normal operating conditions of the switching transistor, the A-phase current under single-transistor chopper control is analyzed based on the motor control principle. During the conduction interval, the current rises rapidly and P... S2 Always set to 1, P is set to 1 when the current is below the chopper lower limit. S1 With chopper S1 turned on, current flows through the S1-S2 circuit, and this phase enters the positive voltage excitation mode (M1). Since the current flows in the positive direction through the current sensor, its measured value is i. a When the current exceeds the chopper limit, P S1 With chopper S1 turned off, current flows through the D2-S2 circuit, and this phase enters zero-voltage freewheeling mode (M2). Since the current flows through the current sensor in the negative direction, its measured value is -i. a When this correlation breaks, P S1 P S2 Always set to 0, S1 and S2 are off. The current drops rapidly through the D2-D1 circuit, and this phase enters the negative voltage demagnetization mode (M3). Since the current flows through the current sensor in the negative direction, its measured value is -2i. a Then, when the motor reaches the next phase-on position, the above process is repeated. Based on the analysis, the actual phase current and detection current under normal conditions of the upper and lower switching transistors change with the drive signal, as shown in Table 1. Specifically, in Table 1, P... s1 P is the drive signal for chopper S1. s2 The driving signal for chopper S1, i a Let i be the current value of phase A winding. csa This is the value measured by the current sensor.

[0051] Based on the type of short-circuit fault in the switching transistors, there are three types: short circuit in chopper transistor S1, short circuit in conducting transistor S2, and short circuit in both upper and lower switching transistors S1 and S2. Based on the location of the fault, there are two types: short circuit in the conducting region and short circuit in the non-conducting region. The regional divisions are as follows: Figure 3 As shown. Therefore, there are 6 types of short-circuit faults for phase A.

[0052] To facilitate subsequent fault diagnosis, it is necessary to analyze the short-circuit waveform characteristics of each of these six short-circuit fault types, and then summarize and organize them. Next, we will analyze the situation where the chopper tube S1 fails.

[0053] When chopper S1 is short-circuited and conductor S2 is working normally, taking phase A as an example, the current of phase A under single-tube chopper control is analyzed. If this fault occurs when the motor is in positive voltage excitation mode (M1), the current rises rapidly in the conduction interval and P S2 Always set to 1, consistent with normal conditions, since the current flows through the current sensor in the positive direction, its measured value is i. a If this fault occurs when the motor is in zero-voltage freewheeling mode (M2), due to the short circuit of chopper S1, the current still flows through the S1-S2 circuit and cannot be chopped. In the subsequent conduction range, the current in that phase will continue to rise until it enters the non-conducting range. Only then will the current be forced into zero-voltage freewheeling mode (M2) due to the turn-off of conductor S2. Since the current flows in the positive direction through the current sensor, its measured value is i. a If this fault occurs while the motor is in negative pressure demagnetization mode (M3), P S1 P S2 The current is always set to 0, but due to the short circuit of chopper S1, the current in that phase continues through the D1-S1 loop, and that phase enters the zero-voltage freewheeling mode (M2). Since the current flows through the current sensor in the positive direction and then in the negative direction, its measured value is 0, indicating a clear fault. This process repeats when the motor reaches the next on-state of that phase. Based on the analysis, we can roughly obtain the changes in the actual phase current and detected current with the drive signal under short-circuit faults in both the conducting and non-conducting regions of chopper S1, as shown in Table 1.

[0054] Then, the scenario of a fault in the conducting tube S2 is analyzed. When a short-circuit fault occurs in the conducting tube S2, the current change during the conduction phase is consistent with that under normal switching conditions. Single-tube current chopping control can be performed normally, and the current amplitude remains near the chopping limit throughout the conduction range. However, if this fault occurs when the motor is in negative voltage demagnetization mode (M3), in the non-conducting range, the short-circuit fault in the conducting tube causes the chopper tube S1 to turn off and the conducting tube S2 to turn on, and the current in this phase freewheels through the conducting tube S2 and diode D2. Because the current in this phase cannot demagnetize quickly, a large current will be generated in the freewheeling circuit. Unlike the short-circuit fault in the chopper tube S1, after this fault occurs, the current measurement value in the non-conducting range is still negative, and its measured value is -i. a Based on the analysis, we can roughly obtain the changes in the actual phase current and detection current of the conducting tube S2 with the drive signal under short-circuit faults in the conducting and non-conducting regions, as shown in Table 1.

[0055] Finally, the scenario where both switches S1 and S2 experience short-circuit faults is analyzed. When both switches S1 and S2 experience short-circuit faults, regardless of whether the faulty phase is on or off, the short circuit forces that phase to remain on, keeping it in positive voltage excitation mode (M1). The current therefore increases uncontrollably. After the fault occurs, the current measurement value from the current sensor remains constant. a The fault characteristics are obvious. Based on the analysis, we can roughly obtain the changes in the actual phase current and detection current with the drive signal when a short circuit fault occurs in the conduction and non-conducting regions of switching transistors S1 and S2, as shown in Table 1.

[0056] Table 1. Changes in current measurements during normal operation and short-circuit faults of the switching transistor.

[0057]

[0058] Therefore, if a short circuit fault occurs in the switching transistors of phase A, there are a total of 6 short circuit fault scenarios: short circuit of chopper S1 in the conducting region, short circuit of chopper S1 in the non-conducting region, short circuit of conducting transistor S2 in the conducting region, short circuit of conducting transistor S2 in the non-conducting region, short circuit of both transistors in the conducting region, and short circuit of both transistors in the non-conducting region. Thus, there are a total of 18 short circuit fault scenarios for the switching transistors of a three-phase 12 / 8 switched reluctance motor power converter: short circuit of chopper S1 in the conducting region of phase A, short circuit of chopper S1 in the non-conducting region of phase A, short circuit of conducting transistor S2 in the conducting region of phase A, short circuit of conducting transistor S2 in the non-conducting region of phase A, short circuit of both transistors in the conducting region of phase A, short circuit of both transistors in the non-conducting region of phase A, short circuit of chopper S3 in the conducting region of phase B, and short circuit of both transistors in the conducting region of phase B. The following are examples of short-circuit faults in switching transistors: Short circuit in the non-conducting region; Short circuit in the conducting region of phase B conducting transistor S4; Short circuit in the non-conducting region of phase B conducting transistor S4; Short circuit in the conducting region of phase B dual transistors; Short circuit in the non-conducting region of phase B dual transistors; Short circuit in the conducting region of phase C chopper transistor S5; Short circuit in the non-conducting region of phase C chopper transistor S5; Short circuit in the conducting region of phase C conducting transistor S6; Short circuit in the non-conducting region of phase C conducting transistor S6; Short circuit in the conducting region of phase C dual transistors; Short circuit in the non-conducting region of phase C dual transistors. To facilitate fault diagnosis, these 18 types of short-circuit faults in switching transistors are summarized. Based on the short-circuit current waveform characteristics of conducting transistor S2, it can be found that the fault characteristics of short-circuit faults in conducting transistor S2 are not obvious in the conducting region. Therefore, the two types of faults—short circuits in the conducting and non-conducting regions of the conductive tube S2—can be considered as one. That is, regardless of when a short circuit fault occurs in S2, it is considered to have occurred in the non-conducting region. Thus, the 18 types of short circuit faults can be simplified to 15 types, namely: short circuit in the conducting region of phase A chopper tube S1 (Fault I), short circuit in the non-conducting region of phase A chopper tube S1 (Fault IV), short circuit in phase A conductive tube S2 (Fault III), short circuit in the conducting region of phase A dual tubes (Fault II), short circuit in the non-conducting region of phase A dual tubes (Fault V), short circuit in the conducting region of phase B chopper tube S3 (Fault I), and short circuit in the non-conducting region of phase B chopper tube S3. Short circuit (Fault IV), short circuit of phase B conducting tube S4 (Fault III), short circuit of phase B dual tubes in the conducting region (Fault II), short circuit of phase B dual tubes in the non-conducting region (Fault V), short circuit of phase C chopper tube S5 in the conducting region (Fault I), short circuit of phase C chopper tube S5 in the non-conducting region (Fault IV), short circuit of phase C conducting tube S6 (Fault III), short circuit of phase C dual tubes in the conducting region (Fault II), short circuit of phase C dual tubes in the non-conducting region (Fault V). Simplifying fault types by analyzing the short-circuit current waveform characteristics greatly reduces the complexity of the diagnostic logic, making the diagnostic logic easier to implement and operate.

[0059] like Figure 4As shown, this diagram is the overall logic flowchart for short-circuit fault diagnosis. The determination of the conducting and non-conducting regions is based on the setting of the turn-on and turn-off angles. When the rotor position angle θ of the motor is within (θ... on ,θ off When the current is within the specified range, the system determines it to be in the conducting range. Otherwise, it is in the non-conducting range. In the conducting range, short-circuit fault diagnosis of the switching transistor is performed by setting dual current limiting values ​​and detecting the phase current in real time. In the non-conducting range, short-circuit faults of the switching transistor in this range are diagnosed by detecting whether a short-circuit fault has occurred by differentially analyzing the current sensor measurements and performing a simple switching transistor on / off test.

[0060] like Figure 5 As shown, this diagram is a flowchart of the short-circuit fault diagnosis logic in the conduction region. By setting dual current limiting values ​​and monitoring the phase current in real time within the conduction region, short-circuit fault diagnosis is performed on the switching transistor. Taking phase A as an example, the following steps are executed in real time:

[0061] Step A: Sample the current of phase A and perform current chopping control on the motor to keep the current constant in the conduction region.

[0062] Step A-1: ​​Detect the current signal on the A-phase winding of the motor using a current sensor and collect the A-phase current value.

[0063] Step A-2: Phase A winding is conducting within the 0-17° range, and the controller performs single-tube current chopping control. The implementation is as follows: An upper chopping threshold is set for the current in the conduction range of this phase. When the current rises to the upper chopping threshold, chopper S1 for that phase is turned off to reduce the current. Simultaneously, a lower chopping threshold is set for the current in this conduction range. When the current drops to the lower threshold, chopper S1 for that phase is turned on to increase the current. Furthermore, in this conduction region, conductor S2 remains continuously conducting.

[0064] Step B: When the position signal detects that the phase is in the conduction range, proceed to step C.

[0065] Step C: Set dual current limiting values ​​to perform real-time diagnosis of short-circuit faults in the switching transistor during the conduction range. Follow these steps:

[0066] Step C-1: Set a current limit value i that is slightly larger than the upper limit threshold of the chopper. th1 i th2 , where i th1 The first current limit value (first current limit value i) th1 (Take 120% of the current chopping upper limit), i th2 The second current limit value and i th1 Less than i th2 (Second current limit value i) th2(Take 140% of the current chopping upper limit). When the absolute value measured by the current sensor in the conduction region of this phase exceeds the first current value limit i th1 If the absolute value measured by the current sensor does not exceed the first current limit value, the upper and lower switches of the phase are diagnosed as operating normally, and the process jumps to step D.

[0067] Step C-2: If the current exceeds the first current limit value during the conduction interval, the test phase begins. At this time, the upper and lower switches of that phase are forcibly turned off. If the current decreases, the absolute value of the sensor detection value is less than the first current limit value i. th1 If the fault is diagnosed as fault I, proceed to step D; if the current increases and the absolute value of the sensor detection value is greater than the second current limit value i th2 If the diagnosis is fault II, proceed to step D.

[0068] Step D: This diagnosis ends. If the phase is still in the conducting region, proceed to the next diagnosis; if the phase enters the non-conducting region, jump to the non-conducting region diagnosis step.

[0069] like Figure 6 As shown, this diagram is a flowchart of the short-circuit fault diagnosis logic in the non-conducting region. The short-circuit fault in this section is diagnosed by detecting the difference between the current sensor measurements and performing a simple switching transistor continuity test. Taking phase A as an example, the following steps are executed in real time:

[0070] Step A: Sample the A-phase current and perform chopper control on the motor.

[0071] Step A-1: ​​Detect the current signal on the A-phase winding of the motor using a current sensor and collect the A-phase current value.

[0072] Step A-2: Phase A winding is conducting within the 0-17° range, and the controller performs single-tube current chopping control. The implementation is as follows: An upper chopping threshold is set for the current in the conduction range of this phase. When the current rises to the upper chopping threshold, chopper S1 for that phase is turned off to reduce the current. Simultaneously, a lower chopping threshold is set for the current in this conduction range. When the current drops to the lower threshold, chopper S1 for that phase is turned on to increase the current. Furthermore, in this conduction region, conductor S2 remains continuously conducting.

[0073] Step B: When the position signal detects that the phase is in the non-conducting range, proceed to step C.

[0074] Step C: Real-time detection of sensor values ​​in the non-conductive region and differential analysis. If the absolute value of the differential value is not greater than a preset threshold δ (the preset threshold δ is set to 120% of the current differential value when the motor is running normally), then the switch transistors S1 and S2 are diagnosed as working normally, and the process proceeds to step F. If the absolute value of the differential value is greater than the preset threshold, then a preliminary diagnosis of a short circuit fault in the switch transistors is made, and the process proceeds to step D.

[0075] Step D: Check if the sensor reading is greater than 0. If the sensor reading is greater than 0, fault V is identified, and proceed to step F. Otherwise, proceed to step E.

[0076] Step E: Enter the testing phase and turn on the lower switch S2. Jump to step E-1.

[0077] Step E-1: During the testing phase, if the sensor detection value is greater than 0, fault IV is identified, and the process jumps to step F.

[0078] Step E-2: During the testing phase, if the sensor detection value is less than or equal to 0, fault III is identified, and the process jumps to step F.

[0079] Step F: Output the diagnostic result, and the current diagnosis ends. If the phase is still in the non-conductive region, proceed to the next diagnosis; if the phase enters the conductive region, jump to the conductive region diagnosis step.

[0080] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for diagnosing short-circuit faults in SRM switching transistors based on a new connection method of current sensors, characterized in that, Based on a switched reluctance motor and its asymmetrical half-bridge power converter, the switched reluctance motor includes a power converter, an A-phase winding, a B-phase winding, and a C-phase winding; the power converter is an asymmetrical half-bridge power converter, including a DC bus capacitor c, diodes, and switching transistors; the switching transistors include switching transistors S1, S2, S3, S4, S5, and S6, and the diodes include diodes D1, D2, D3, D4, D5, and D6; the positive terminal of the DC bus capacitor c is connected to one end of switching transistor S1, one end of switching transistor S3, one end of switching transistor S5, and the cathodes of diodes D1, D3, and D5, and is connected to an external DC power supply U. s The positive terminals of the capacitors are connected together, and the negative terminals of the DC bus capacitor c are connected to one end of the switching transistor S2, one end of the switching transistor S4, one end of the switching transistor S6, and the anodes of the diodes D2, D4, and D6, respectively, and are connected to the external DC power supply U. s The negative terminals are connected together; the current sensor includes current sensor CS1, current sensor CS2, and current sensor CS3; Each current sensor has three wires passing through it. One end of the first wire is connected to the upper switch in the corresponding target phase and passes through the current sensor in the positive direction to connect to one end of the target phase winding. One end of the second wire in the current sensor is connected to the cathode of diode D2, D4, or D6 in the corresponding target phase and passes through the current sensor in the negative direction to connect to the same end of the target phase winding. One end of the third wire in the current sensor is connected to the anode of diode D1, D3, or D5 in the corresponding target phase and passes through the current sensor in the positive direction to connect to the other end of the target phase winding. Using each phase as the target phase, the following steps are used to achieve real-time diagnosis of short-circuit faults in the target phase's switching transistors: Step 1: Based on whether the short circuit fault of the target phase switch tube occurs in the conducting state or the non-conducting state, the diagnostic strategy is divided into fault diagnosis of switch tube in the conducting area and fault diagnosis of switch tube in the non-conducting area. Step 2: Based on the acquisition of the target phase current value, and combined with the preset chopping upper and lower thresholds of the target phase conduction region, current chopping control of the target phase is achieved; the lower switch of the target phase conduction region is kept on, and when the target phase current value rises to the chopping upper threshold, the upper switch of the target phase is turned off to reduce the target phase current value; when the target phase current value drops to the chopping lower threshold, the upper switch of the target phase is turned on to increase the target phase current value. Step 3: After the current chopping control of the target phase, if the position signal detects that the target phase is in the conducting region, the fault diagnosis of the switching transistor in the conducting region is adopted, and the process jumps to step 4. If the target phase is detected to be in the non-conducting region, the fault diagnosis of the switching transistor in the non-conducting region is adopted, and the process jumps to step 5. Step 4: Use the dual current limiting value test method to diagnose the short circuit fault of the switching transistor in the conduction region; the specific steps of Step 4 are as follows: Step 4-1: Set a current limit value that is numerically greater than the chopper upper limit threshold. i th1 , i th2 ,in i th1 The first current limit value, i th2 The second current limit value and i th1 Less than i th2 When the absolute value measured by the current sensor in the target phase conduction region exceeds the first current value limit. i th1 If the target phase is diagnosed as having a short circuit fault in the switching transistor, proceed to step 4-2. If the absolute value measured by the current sensor does not exceed the first current limit value, it is diagnosed that the upper and lower switches of the target phase are operating normally, and the process jumps to step 4-3. Step 4-2: If the current exceeds the first current limit value during the conduction interval, the test phase begins. At this time, the upper and lower switches of the target phase are forcibly turned off. If the current decreases, the absolute value of the sensor detection value is less than the first current limit value. i th1 If the fault is diagnosed as fault I, proceed to step 4-3; if the current increases and the absolute value of the sensor detection value is greater than the second current limit value. i th2 If so, the diagnosis is fault II, and the process jumps to step 4-3; Step 4-3: This diagnosis is now complete. If the target phase is still in the conduction region, proceed to the next diagnosis. If the target phase has entered the non-conductivity region, proceed to step 5. Step 5: Detect the current sensor readings in the non-conducting area and perform differential analysis to check for short circuit faults. Then, perform a switching transistor continuity test to diagnose short circuit faults in the switching transistor in that area. The specific steps of step 5 are as follows: Step 5-1: Real-time detection of sensor values ​​in the non-conductive area and differential calculation; if the absolute value of the value after differential processing is not greater than the preset threshold... d Preset threshold d If the current difference value is set to 120% of the value when the motor is running normally, the switch transistors S1 and S2 are diagnosed as working normally and the process jumps to step 5-6; if the absolute value of the value after differential processing is greater than the preset threshold, a short circuit fault is initially diagnosed in the switch transistors and the process jumps to step 5-2. Step 5-2: Check if the sensor detection value is greater than 0; if the sensor detection value is greater than 0, determine fault V and jump to step 5-6; otherwise, jump to step 5-3; Step 5-3: Enter the testing phase and turn on the lower switch S2; Jump to step 5-4; Step 5-4: During the testing phase, if the sensor detection value is greater than 0, fault IV is identified, and the process proceeds to step 5-6. Step 5-5: During the testing phase, if the sensor detection value is less than or equal to 0, fault III is identified, and the process proceeds to step 5-6. Steps 5-6: Output the diagnostic results, and this diagnosis ends; if the phase is still in the non-conductive region, proceed to the next diagnosis; if the phase enters the conductive region, jump to step 4.

2. The method for diagnosing short-circuit faults of SRM switching transistors based on a new connection method of current sensors according to claim 1, characterized in that, The specific steps of step 1 are as follows: Step 1-1: Classify the short-circuit fault types of the switching transistor as follows: Based on the motor's operating status and the switching status, the areas where short-circuit faults occur are divided into conducting and non-conducting regions. Based on the type of switching transistor, short-circuit faults are further categorized into upper transistor short circuit, lower transistor short circuit, and double transistor short circuit. Therefore, a total of six fault types are derived: upper transistor short circuit in conducting region, lower transistor short circuit in conducting region, double transistor short circuit in conducting region, upper transistor short circuit in non-conducting region, lower transistor short circuit in non-conducting region, and double transistor short circuit in non-conducting region. Thus, if a short-circuit fault occurs in phase A, there are a total of six possible short-circuit fault scenarios: short circuit of chopper transistor S1 in conducting region, short circuit of chopper transistor S1 in non-conducting region, short circuit of conducting transistor S2 in conducting region, short circuit of conducting transistor S2 in non-conducting region, double transistor short circuit in conducting region, and double transistor short circuit in non-conducting region. Therefore, there are a total of 18 possible short-circuit faults in the switching transistors of a three-phase 12 / 8 switched reluctance motor power converter. The following are examples of short circuits: Phase A chopper S1 short circuit in the conducting region; Phase A chopper S1 short circuit in the non-conducting region; Phase A conducting tube S2 short circuit in the conducting region; Phase A conducting tube S2 short circuit in the non-conducting region; Phase A dual tube short circuit in the conducting region; Phase A dual tube short circuit in the non-conducting region; Phase B chopper S3 short circuit in the conducting region; Phase B chopper S3 short circuit in the non-conducting region; Phase B conducting tube S4 short circuit in the conducting region. A short circuit occurs in the following situations: Phase B conducting tube S4 short circuit in the non-conducting area; Phase B dual tube short circuit in the conducting area; Phase B dual tube short circuit in the non-conducting area; Phase C chopper tube S5 short circuit in the conducting area; Phase C chopper tube S5 short circuit in the non-conducting area; Phase C conducting tube S6 short circuit in the conducting area; Phase C conducting tube S6 short circuit in the non-conducting area; Phase C dual tube short circuit in the conducting area; Phase C dual tube short circuit in the non-conducting area. Step 1-2: Simplify the short-circuit fault types of the switching transistor, as follows: Based on the current waveform analysis, it is concluded that since the conductor is always in the open state in the conducting region, the short circuit fault that occurs at this time will not affect the current change trend at the moment of the short circuit. The short circuit fault will affect the current in the non-conducting region. Therefore, the short circuit in the conducting region and the short circuit in the non-conducting region are combined into a short circuit in the non-conducting region. Steps 1-3: Summarize the types of short-circuit faults in the switching transistor, as follows: The 18 types of short-circuit faults are simplified to 15: Short circuit in the conducting region of upper tube (Fault I), Short circuit in the conducting region of both tubes (Fault II), Short circuit in the non-conducting region of upper tube (Fault IV), Short circuit in the non-conducting region of lower tube (Fault III), and Short circuit in the non-conducting region of both tubes (Fault V). V. Short circuit fault occurred in the conducting area of ​​phase B chopper S3 - Fault I; Short circuit fault occurred in the non-conducting area of ​​phase B chopper S3 - Fault IV; Short circuit fault occurred in the conducting area of ​​phase B chopper S4 - Fault III; Short circuit fault occurred in the conducting area of ​​phase B dual-tube - Fault II; Short circuit fault occurred in the non-conducting area of ​​phase B dual-tube - Fault V; Short circuit fault occurred in the conducting area of ​​phase C chopper S5 - Fault I; Short circuit fault occurred in the non-conducting area of ​​phase C chopper S5 - Fault IV; Short circuit fault occurred in the conducting area of ​​phase C chopper S6 - Fault III; Short circuit fault occurred in the conducting area of ​​phase C dual-tube - Fault II; Short circuit fault occurred in the non-conducting area of ​​phase C dual-tube - Fault V.

3. The method for diagnosing short-circuit faults of SRM switching transistors based on a new current sensor connection method according to claim 1, characterized in that, The specific steps for step 2 are as follows: Assuming all switches are operating normally, the target phase current is: i a When the upper and lower switching transistors S1 and S2 are turned on, the measured phase current value is i a When the upper switch S1 is on and the lower switch S2 is off, the phase current measurement is 0; when the upper switch S1 is off and the lower switch S2 is on, the phase current measurement is - i a When both upper and lower switching transistors S1 and S2 are turned off, the measured phase current value is -2. i a This distinguishes the different circuits through which the current flows. At the same time, by multiplying the current measurement value in the non-conducting region by a coefficient of -0.5 and processing the absolute value of the measurement value in the conducting region, the winding current waveform during normal motor operation is reconstructed.

4. The method for diagnosing short-circuit faults of SRM switching transistors based on a new current sensor connection method according to claim 1, characterized in that, In step 4-1, the first current limiting value i th1 Take 120% of the current chopping upper limit, and the second current limit value. i th2 Take 140% of the current chopping limit.

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