A short-circuit fault dynamic diagnosis method for switch tube of SRM using current translation

Abstract

The application discloses a kind of SRM switching tube short-circuit fault dynamic diagnosis method using current translation.The switching tube short-circuit fault diagnosis method uses the way of shifting actual current waveform by an electric period, the current waveform of last electric period is used as reference current waveform corresponding to current electric period, then the corresponding current difference value is obtained by comparing reference current with this electric period current, combined with the sign of current sensor measurement value and rotor position angle, the switching tube short-circuit fault of asymmetric half-bridge power converter is accurately judged.The SRM switching tube short-circuit fault dynamic diagnosis method using current translation of the application can meet the fault diagnosis when motor is in steady state and dynamic operation.The switching tube short-circuit fault diagnosis scheme is suitable for switching reluctance motor with various phase numbers.It has important application prospect in application occasions with extremely high motor reliability requirement, such as aviation starting generator and electric vehicle motor.

Description

Technical Field

[0001] This invention belongs to the field of switched reluctance motor control technology, and particularly relates to a dynamic diagnosis method for short-circuit faults of SRM switching transistors using current shifting. Background Technology

[0002] A power converter is an electronic device that integrates the control of the connection sequence of each phase winding to the power supply, the provision of a feedback loop for winding energy storage, and the power supply to the motor. If a short-circuit fault occurs in the power converter's switching transistors during normal motor operation, it will lead to a deterioration in the motor's operating condition and seriously affect its normal operation. Since a short circuit in the switching transistors can generate a large current, it poses a serious threat to the motor and related equipment. Therefore, it is crucial to diagnose short-circuit faults in the switching transistors quickly and accurately.

[0003] Traditional short-circuit fault diagnosis methods mostly involve using additional current sensors, which undoubtedly increases detection costs and operational complexity. Therefore, designing a technology for rapid fault diagnosis without the need for additional current sensors can significantly improve the reliability of switched reluctance motor systems, especially for applications with extremely high reliability requirements, such as precision servo motors, electric vehicles, and aerospace. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a dynamic diagnostic method for short-circuit faults of SRM switching transistors using current shifting. This diagnostic scheme does not require an additional current sensor, is simple to operate, easy to implement, and has high reliability.

[0005] When the system is in steady-state operation, the phase current waveform of the previous electrical cycle is shifted by one electrical cycle using the current translation method. This shifted waveform is then compared with the current waveform of the current electrical cycle, and the difference between the two is calculated in real time. The magnitude of this difference is used as the basis for fault diagnosis to quickly diagnose short-circuit faults in the switching transistors occurring in the current electrical cycle. When the system is in dynamic operation, a current threshold is set in the conduction region to diagnose whether a chopper transistor short-circuit fault has occurred. In the non-conducting region, the magnitude and sign of the current sensor measurements at rotor position angles of 22.5° and 25° are used to determine and locate the short-circuit faulty switching transistor. Dynamic diagnosis of short-circuit faults in the drive system's switching transistors is achieved by switching the diagnostic mode under different system operating states.

[0006] Technical Solution: This invention provides a dynamic diagnostic method for short-circuit faults of SRM switching transistors using current shifting. It employs an asymmetrical half-bridge power converter for a switched reluctance motor. During the conduction intervals of each phase of the switched reluctance motor, the upper switching transistor of each phase bridge arm of the power converter acts as a chopper, and the lower switching transistor acts as a conduction transistor. By combining phase current waveform shifting, and taking each phase as the target phase, the following steps are performed to achieve rapid diagnosis of short-circuit faults in the target phase switching transistors.

[0007] Step A: Obtain the position signal from the position sensor and calculate the actual speed of the switched reluctance motor drive system based on the position signal. Determine the state of the switched reluctance motor drive system. If the difference between the preset reference speed and the actual speed is Δ... n Less than the preset speed threshold n th If the condition is met, the switched reluctance motor drive system is determined to be in a steady-state operation and the process jumps to step B; otherwise, the switched reluctance motor drive system is determined to be in a dynamic operation and the process jumps to step J.

[0008] Step B: Enter the steady-state diagnostic process, obtain the current sensor measurement value by measuring the target phase using the current sensor, and then proceed to step C;

[0009] Step C: After processing the absolute value of the current sensor measurement to obtain the actual phase current value of the target phase, proceed to step D;

[0010] Step D: Calculate the electrical cycle and shift the current signal of the previous electrical cycle by one electrical cycle to achieve the shifting of the target phase current signal. Use the current waveform after shifting by one electrical cycle as the target phase current reference waveform for the current electrical cycle, and then obtain the reference current value for the current electrical cycle. Proceed to step E.

[0011] Step E: Calculate the difference Δ between the actual current value of the target phase and the reference current value corresponding to the current electrical cycle. If the absolute value of the difference Δ is greater than the preset threshold i th1 If the absolute value of the difference Δ is less than or equal to the preset threshold i, then proceed to step F; th1 If so, proceed to step I;

[0012] Step F: Obtain the current position angle of the target phase through the position sensor. If the current position angle is greater than or equal to 0° and less than or equal to 17°, it is determined that the detection phase is in the conducting region and the process jumps to step G; if the current position angle is greater than 17° and less than 45°, it is determined that the detection phase is in the non-conducting region and the process jumps to step H.

[0013] Step G: When the target phase is detected to be in the conduction region, the absolute value of the difference Δ between the actual phase current value and the reference current value corresponding to the current electrical cycle is greater than the preset threshold i. th1If the test result is positive, the chopper tube is diagnosed as short-circuited. The diagnosis ends, and the process jumps to step I.

[0014] Step H: When the target phase is detected to be in the non-conducting region, if the absolute value of the difference Δ between the actual phase current value and the reference current value corresponding to the current electrical cycle is greater than the preset threshold i th1 And the current sensor measured value i csa If the sign is positive, the diagnosis is a short circuit in the detection phase chopper; if the absolute value of the difference Δ between the actual phase current value and the reference current value corresponding to the current electrical cycle is greater than the preset threshold i... th1 And the current sensor measured value i csa If the sign is negative, the diagnosis is a short circuit in the detection phase conductive tube, the diagnosis ends, and the process jumps to step I;

[0015] Step I: Proceed to the next diagnostic cycle, then skip to Step A;

[0016] Step J: Enter the dynamic diagnostic process, then proceed to step K;

[0017] Step K: Obtain the current position angle through the position sensor. If the current position angle is greater than or equal to 0° and less than or equal to 17°, it is determined that the detection phase is in the conducting region, and the process jumps to step M; if the current position angle is greater than 17° and less than 45°, it is determined that the detection phase is in the non-conducting region, and the process jumps to step L.

[0018] Step M: Set the current threshold i th2 If the current i is measured in the conduction interval csa The absolute value exceeds the current threshold i th2 If the current is less than the current threshold i during the conduction interval, the system will terminate the diagnosis and proceed to step P. th2 If the system detects that no short circuit fault has occurred in the detected phase, the system will end the diagnosis and jump to step P.

[0019] Step L: Obtain the current values ​​at position angles of 22.5° and 25° respectively using the rotor position signal and current signal of the target phase, and then proceed to step N;

[0020] Step N: Compare the current values ​​corresponding to these two position angles. If the absolute value of the current value corresponding to position angle 22.5° or 25° is found to be greater than the preset current threshold i, then... th3 If the circuit is short-circuited, it is determined that a short circuit fault has occurred in the switching transistor, and the process jumps to step O.

[0021] Step O: When the current sensor measurement value i of the target phase is at this time csa When the value is less than 0, the system diagnoses a short circuit fault in the conductive tube, terminates the diagnosis, and jumps to step P; when the current sensor measurement value i at this time... csaWhen the value is greater than 0, the system diagnoses a chopper tube short-circuit fault, the system terminates the diagnosis, and jumps to step P; when the current sensor measurement value i at this time... csa When the value is equal to 0, the diagnostic process continues running in step O until the current sensor measurement value i is reached. csa The signs can be positive or negative;

[0022] Step P: The dynamic diagnostic process ends, and the next diagnostic cycle begins. Proceed to Step A.

[0023] Furthermore, the current sensor is connected as follows: the other end of the switch S1 passes through the current sensor CS1 in the forward direction and is connected to one end of the A-phase winding. Then, the wire connected to the cathode of the diode D2 passes through the current sensor CS1 in the reverse direction and is connected to the same end of the A-phase winding. The other end of the switch S3 passes through the current sensor CS2 in the forward direction and is connected to one end of the B-phase winding. Then, the wire connected to the cathode of the diode D4 passes through the current sensor CS2 in the reverse direction and is connected to the same end of the B-phase winding. The other end of the switch S5 passes through the current sensor CS3 in the forward direction and is connected to one end of the C-phase winding. Then, the wire connected to the cathode of the diode D6 passes through the current sensor CS3 in the reverse direction and is connected to the same end of the C-phase winding.

[0024] Furthermore, in step A, the rotational speed threshold n th Take 120% of the speed fluctuation value when the motor is running in normal steady state.

[0025] Furthermore, the steps for shifting the phase current in step D are as follows:

[0026] Step A: Measure the rotor position angle of the detection phase using a position sensor, then differentiate the rotor position angle to obtain the angular velocity, and finally convert the angular velocity into the rotational speed n using the quantitative relationship between the angular velocity and the rotational speed.

[0027] Step B, since the electric cycle T and the rotational speed n have the following numerical relationship, the relationship is as follows:

[0028]

[0029] Since the motor used is a 12 / 8 switched reluctance motor, N r It is 8;

[0030] Step C: Based on the calculated rotational speed, shift the current measurement signal backward by one electrical cycle in real time. Then, subtract the real-time current value obtained through the current sensor from the reference current value corresponding to the current electrical cycle to obtain the current error value Δ.

[0031] Furthermore, in step G, if the absolute value of the difference Δ between the actual phase current value and the reference current value corresponding to the current electrical cycle is greater than a preset threshold i, then... th1 When the switching transistor is operating normally, the current error calculated by the current shift method is between (-0.2, 0.2). A threshold i is set. th1 It is 0.4.

[0032] Furthermore, in step M, the current threshold i th2 Take 130% of the current chopping limit value when the motor is running.

[0033] Furthermore, in step N, the current threshold i th3 Take the current value of 4A when the motor is in normal operation at a position angle of 22.5°.

[0034] When the system is in steady state, the phase current waveform of the previous electrical cycle is shifted by one electrical cycle using the current shift method. Then, the shifted current waveform is used as a reference current waveform and compared with the current waveform of the current electrical cycle. The difference between the two is calculated in real time, and the magnitude of the difference is used as the basis for fault judgment to quickly diagnose short-circuit faults of the switching transistors that occur in the current electrical cycle.

[0035] When the system is running dynamically, a chopper tube short-circuit fault is diagnosed by setting a current threshold during the conduction interval; during the non-conducting interval, the short-circuit fault switch is determined and located by the magnitude and sign of the current sensor measurements at rotor position angles of 22.5° and 25°.

[0036] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0037] (1) The present invention provides a dynamic diagnostic method for short-circuit faults of SRM switching transistors using current shifting, which can meet the fault diagnosis requirements of motors during steady-state and dynamic operation. The aforementioned short-circuit fault diagnosis scheme is applicable to switched reluctance motors with various phase numbers. It has significant application prospects in applications where motor reliability requirements are extremely high, such as aircraft starter generators and electric vehicle motors.

[0038] (2) The diagnostic scheme of this invention does not require an additional current sensor, is simple to operate, easy to implement, and has high reliability; it can quickly diagnose short-circuit faults of switching transistors without affecting current detection. The controller can still obtain the actual phase current value through the current sensor. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the current sensor connection method;

[0040] Figure 2 This is a schematic diagram of the translation current waveform;

[0041] Figure 3 This is the overall logic flowchart for short-circuit fault diagnosis;

[0042] Figure 4 This is a flowchart of the short-circuit fault diagnosis logic during steady-state operation;

[0043] Figure 5 This is a flowchart of the logic for diagnosing short-circuit faults during dynamic runtime. Detailed Implementation

[0044] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0045] This invention designs a dynamic diagnostic method for short-circuit faults in SRM (Short-Circuit Resistor) switches using current shifting. When the system is in steady-state operation, the phase current waveform of the previous electrical cycle is shifted by one electrical cycle using the current shifting method. This shifted waveform is then compared with the current waveform of the current electrical cycle, and the difference between the two is calculated in real time. The magnitude of this difference is used as the basis for fault judgment to quickly diagnose short-circuit faults in the switch that occurred in the current electrical cycle. When the system is in dynamic operation, a current threshold is set in the conduction region to diagnose whether a chopper tube short-circuit fault has occurred. In the non-conducting region, the magnitude and sign of the current sensor measurements at rotor position angles of 22.5° and 25° are used to determine and locate the short-circuit faulty switch. Dynamic diagnosis of short-circuit faults in the drive system's switches is achieved by switching the diagnostic mode under different system operating states. The motor adopts a voltage pulse width modulation single-transistor control strategy, and fixes the turn-on and turn-off angles and current chopping limits. In phase A, the upper switch S1 is set as the chopper and the lower switch S2 is set as the conduction tube; in phase B, the upper switch S3 is set as the chopper and the lower switch S4 is set as the conduction tube; and in phase C, the upper switch S5 is set as the chopper and the lower switch S6 is set as the conduction tube.

[0046] like Figure 1 The diagram shows a schematic of the current sensor connection. The connection methods for each current sensor are as follows: The other end of the wire of the switching transistor S1 passes through the current sensor CS1 in the forward direction and is connected to one end of the A-phase winding. Then, the wire connecting to the cathode of diode D2 passes through the current sensor CS1 in the reverse direction and is connected to the same end of the A-phase winding. The other end of the wire of the switching transistor S3 passes through the current sensor CS2 in the forward direction and is connected to one end of the B-phase winding. Then, the wire connecting to the cathode of diode D4 passes through the current sensor CS2 in the reverse direction and is connected to the same end of the B-phase winding. The other end of the wire of the switching transistor S5 passes through the current sensor CS3 in the forward direction and is connected to one end of the C-phase winding. Then, the wire connecting to the cathode of diode D6 passes through the current sensor CS3 in the reverse direction and is connected to the same end of the C-phase winding.

[0047] 1. Short circuit fault types of power converter switching transistors, including: short circuit of A-phase chopper S1 in the conduction area, short circuit of A-phase chopper S1 in the non-conducting area, short circuit of A-phase conducting transistor S2, short circuit of B-phase chopper S3 in the conduction area, short circuit of B-phase chopper S3 in the non-conducting area, short circuit of B-phase conducting transistor S4, short circuit of C-phase chopper S5 in the conduction area, short circuit of C-phase chopper S5 in the non-conducting area, and short circuit of C-phase conducting transistor S6.

[0048] For the nine types of short-circuit faults of the switching transistors mentioned above, since each phase of the asymmetrical half-bridge power converter is independent, this paper takes a short-circuit fault of the switching transistor in phase A as an example to illustrate the dynamic diagnosis scheme of short-circuit faults of the switching transistors based on reference current shifting and reconstruction. First, the changes in the phase A current under normal operating conditions of the switching transistors are analyzed.

[0049] When the switching transistor is working normally and the phase is in the conduction region, if the chopper S1 drive signal P s1 =1 and the drive signal P of the conducting transistor S2 is 1. s2 When the current is 1, the current rises rapidly. Since the current flows through the current sensor in the positive direction, the current sensor's measured value i... csa The sign is positive; if P s1 =0 and P s2 When i = 1, the phase current decreases. Since the current flows through the current sensor in the negative direction, its measured value i csa The sign is negative; when the correlation is broken, P S1 P S2 Always set to 0, S1 and S2 are off. The current decreases rapidly through the freewheeling diodes D2 and D1, causing rapid demagnetization of this phase. Since the current flows through the current sensor in the negative direction, its measured value i... csa The sign is negative. Using the current shift method, the phase current from the previous electrical cycle is shifted to the current electrical cycle for comparison. Since no short-circuit fault occurred in the switching transistor, the current in the current electrical cycle did not change significantly compared to the previous cycle. Therefore, the current error will stabilize within a certain range, fluctuating around zero, generally between (-0.2, 0.2). The changes in the sign of the current error and the sensor measurement value are shown in Table 1.

[0050] Table 1. Phase current variation under normal operating conditions of the switching transistor.

[0051]

[0052] Specifically, as shown in Table 1, * indicates that there are cases where the value is 0. P s1 P is the PWM drive signal for chopper S1. s2 The driving signal for the conducting transistor S2, i real i represents the actual phase winding current value.csa i is the value measured by the current sensor. ref This represents the current value of the shifted phase winding.

[0053] If chopper S1 is short-circuited in the conduction region, if P s1 =1 and P s2 When the current is 1, the current rises rapidly. Since the current flows through the current sensor in the positive direction, its measured value i csa The sign is positive; if P s1 =0 and P s2 When P = 1, but due to the short circuit of S1, this phase is still in the positive voltage excitation stage, and the current error increases, exceeding the preset threshold. If the chopper S1 is short-circuited in the non-conducting region, when P s1 =0 and P s2 When the current is 0, due to the short circuit of S1, S1 is turned on and S2 is turned off, and the current continues through the S1-D1 circuit. At this time, the measured value i csa The sign is positive. Because the freewheeling current decreases slowly, the difference between the actual current and the shifted current gradually increases. The changes in the sign of the current error and the sensor measurement are shown in Table 2.

[0054] Table 2. Changes in phase current before and after short circuit in the chopper tube.

[0055]

[0056] If conductor S2 is short-circuited in the conducting region, since the conductor remains open in the conducting region, the short-circuit fault current in this region will not change significantly. If conductor S2 is short-circuited in the non-conducting region, when P... s1 =0 and P s2 When i = 0, due to the short circuit of S2, S1 is turned off and S2 is turned on, and the current continues through the S2 and D2 circuit. At this time, the measured value i csa The sign is negative. Because the freewheeling current decreases slowly, the difference between the actual current and the shifted current gradually increases. The changes in the sign of the current error and the sensor measurement are shown in Table 3.

[0057] Table 3. Changes in phase current before and after a short circuit in the conductor.

[0058]

[0059] like Figure 2 As shown, this figure is a schematic diagram of the translational current waveform. In this figure, i a It is the winding current of phase A, i a Equal to the absolute value of the current sensor measurement i csa P s2 It is the drive signal for the A-phase switch S2, θ on It is the positional opening angle, θ offIt is the position turn-off angle. Assuming the current time is k in electrical cycle k, then i real Let i be the A-phase winding current at time k of this electrical cycle k. a i ref The shifted current value is the A-phase winding current i at time k of the previous electrical cycle k-1. a The current shift method calculates the required shift time based on the real-time rotational speed, assuming a constant rotational speed between two consecutive electrical cycles. However, in reality, the rotational speed may change, and the rotational speeds corresponding to two adjacent electrical cycles are not entirely consistent. Therefore, during the shift, the current signal of the previous electrical cycle may lead or lag behind the current current signal. To address this, the absolute value of the current difference between two adjacent electrical cycles can be used as a fault characteristic for short-circuit fault diagnosis of the switching transistor.

[0060] like Figure 3 As shown, this diagram is the overall logic flowchart for short-circuit fault diagnosis. The system operating status is determined based on the real-time rotational speed, with the difference between the preset reference speed and the real-time rotational speed being Δ. n Greater than the speed threshold n th If the on-state value is within the specified range, the system is considered to be in a dynamic operating state; otherwise, it is considered to be in a steady-state operating state. Furthermore, 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 waveform is within the conducting range (e.g., when the current waveform is within the conducting range, it is considered to be in the conducting range), the system determines it to be in the conducting range. Conversely, when the current waveform is within the conducting range, it is considered to be in the non-conducting range. When the system is in steady-state operation, the phase current waveform of the previous electrical cycle is shifted by one electrical cycle and used as a reference current waveform for comparison with the current waveform of the current electrical cycle. The difference between the two is calculated in real time, and the magnitude of the difference is used as the basis for fault judgment to quickly diagnose short-circuit faults of switching transistors occurring in the current electrical cycle. When the system is in dynamic operation, in the conducting range, a current threshold is set to diagnose whether a chopper tube short-circuit fault has occurred. In the non-conducting range, the magnitude and sign of the current sensor measurements at rotor position angles of 22.5° and 25° are used to determine and locate the short-circuit faulty switching transistor.

[0061] like Figure 4 As shown, this diagram is a flowchart of the short-circuit fault diagnosis logic during steady-state operation of the system. When the drive system is running in steady state, the phase current waveform of the previous electrical cycle is shifted by one electrical cycle and used as a reference current waveform. This waveform is compared with the current waveform of the current electrical cycle, and the difference between the two is calculated in real time. The magnitude of this difference is used as the basis for fault judgment to quickly diagnose short-circuit faults in the switching transistors occurring in the current electrical cycle. Taking phase A as an example, the following steps are executed in real time:

[0062] Step A involves performing voltage pulse width modulation single-transistor control on the motor, fixing the turn-on and turn-off angles and the current chopping limit, and obtaining the current signal through a current sensor.

[0063] Step A-1: ​​Detect the current signal of phase A of the motor using a current sensor and collect the current value of phase A.

[0064] Step A-2: Phase A winding is turned on between 0° and 17°, and the controller performs voltage pulse width modulation single-transistor chopping control. The implementation method is as follows:

[0065] During the conduction range of this phase, a PWM signal with a certain duty cycle obtained from the speed loop is used as the drive signal for the chopper. The position logic signal, current chopper signal, and PWM signal are logically ANDed to obtain the final chopper control signal, which is then sent to the chopper, while the position logic signal is sent to the conducting transistor. When P... s1 =1 and P s2 When P = 1, the current rises rapidly. Since the current flows through the current sensor in the positive direction, the measured value is positive. s1 =0 and P s2 When =1, the phase current decreases. Since the current flows through the current sensor in the negative direction, its measured value is negative. In addition, in this conducting region, the conducting tube S2 always remains conducting.

[0066] Step B: Determine the system's state based on the real-time rotational speed, and preset the difference Δ between the reference speed and the real-time rotational speed. n Less than the speed threshold n th (Speed ​​threshold n) th If the speed fluctuation value of the motor is 120% of the value during normal and stable operation, it is determined that the system is in a steady state of operation, and the process jumps to step C.

[0067] Step C: Shift the current signal from the previous current cycle and calculate the current difference.

[0068] Step C-1: Calculate the translation time based on the position signal and translate the current signal by one electrical cycle T. The calculation formula is as follows:

[0069]

[0070] Step C-2: Subtract the actual current value obtained by the current sensor from the reference current value shifted by one electrical cycle (corresponding to the reference current value of the current electrical cycle) to obtain the current error value Δ. The expression is as follows:

[0071] Δ=i real -i ref (2)

[0072] Among them, i real i represents the actual current value.ref This is the reference current value.

[0073] Step D: Determine the current position range. If θ is greater than or equal to 0° and less than or equal to 17°, proceed to step E; otherwise, proceed to step G.

[0074] Step E involves calculating the difference between the actual current and the reference current in real time to diagnose short-circuit faults in the switching transistor within the conduction range. Follow these steps:

[0075] Step E-1: Set a threshold i that is slightly larger than the normal value for current error. th1 In practice, the current error calculated by the current shift method during normal operation of the switching transistor is generally between -0.2 and 0.2. Therefore, a diagnostic threshold i needs to be set. th1 Take the diagnostic threshold i th1 If the value is 0.4 (twice the normal value), proceed to step E-2.

[0076] Step E-2: If the absolute value of the current error in the conduction interval exceeds the preset threshold i th1 At this point, a short-circuit fault is diagnosed in chopper S1, and the process jumps to step F; if the absolute value of the current error in the conduction interval is less than the preset threshold i th1 If the diagnosis is that the switching transistors S1 and S2 are working normally, the process jumps to step F.

[0077] Step F: This diagnosis ends. If the phase is still in the conducting region, proceed to the next diagnosis and repeat the above steps to step E. If the phase enters the non-conducting region, proceed to the non-conducting region diagnosis step G.

[0078] Step G involves calculating the current difference in real time within the non-conducting region and detecting the sensor readings to perform real-time diagnosis of short-circuit faults in the switching transistor. The calculation is performed as follows:

[0079] Step G-1: Set a threshold i that is slightly larger than the normal value for current error. th1 In practice, the current error calculated by the current shift method during normal operation of the switching transistor is generally between -0.2 and 0.2. Therefore, a diagnostic threshold i needs to be set. th1 Take the diagnostic threshold i th1 If the value is 0.4 (twice the normal value), proceed to step G-1.

[0080] Step G-2: If the absolute value of the current error in the non-conducting region exceeds the preset threshold i th1 And at this time, the current sensor measures i csa If the sign is positive, a short circuit fault in chopper S1 is diagnosed, and the process jumps to step H; if the absolute value of the current error exceeds the preset threshold i in the non-conducting region... th1 And at this time, the current sensor measures icsa If the sign is negative, a short circuit fault in the conducting tube S2 is diagnosed, and the process jumps to step H; if the absolute value of the current error in the conducting interval is less than the preset threshold i th1 If the diagnosis is that the switching transistors S1 and S2 are working normally, proceed to step H.

[0081] Step H: This diagnosis ends. If the phase is still in the non-conductive region, proceed to the next diagnosis, repeating the above steps and jumping to step G; if the phase enters the conductive region, jump to the conductive region diagnosis step E.

[0082] like Figure 5 As shown, this diagram is a flowchart of the short-circuit fault diagnosis logic during dynamic system operation. When the system is running dynamically, a chopper tube short-circuit fault is diagnosed by setting a current threshold during the conduction phase; during the non-conducting phase, the short-circuit fault switch is determined and located by the magnitude and sign of the current sensor measurements at rotor position angles of 22.5° and 25°. Taking phase A as an example, the following steps are executed in real time:

[0083] Step A involves performing voltage pulse width modulation single-transistor control on the motor, fixing the turn-on and turn-off angles and the current chopping limit, and obtaining the current signal through a current sensor.

[0084] Step A-1: ​​Detect the current signal of phase A of the motor using a current sensor and collect the current value of phase A.

[0085] Step A-2: Phase A winding is turned on between 0° and 17°, and the controller performs voltage pulse width modulation single-transistor chopping control. The implementation method is as follows:

[0086] During the conduction range of this phase, a PWM signal with a certain duty cycle obtained from the speed loop is used as the drive signal for the chopper. The position logic signal, current chopper signal, and PWM signal are logically ANDed to obtain the final chopper control signal, which is then sent to the chopper, while the position logic signal is sent to the conducting transistor. When P... s1 =1 and P s2 When P = 1, the current rises rapidly. Since the current flows through the current sensor in the positive direction, the measured value is positive. s1 =0 and P s2 When =1, the phase current decreases. Since the current flows through the current sensor in the negative direction, its measured value is negative. In addition, in this conducting region, the conducting tube S2 always remains conducting.

[0087] Step B: Determine the system's state based on the real-time rotational speed, and preset the difference Δ between the reference speed and the real-time rotational speed. n Greater than the speed threshold n th (Speed ​​threshold n) thIf the speed fluctuation value of the motor is taken as 120% of the value during normal steady-state operation, then the system is judged to be in a dynamic operating state, and the process jumps to step C;

[0088] Step C, proceed to the dynamic diagnostic process, then jump to step D;

[0089] Step D: Obtain the current position angle through the position sensor. If the current position angle is greater than or equal to 0° and less than or equal to 17°, it is determined that the detection phase is in the conducting region, and the process jumps to step E; if the current position angle is greater than 17° and less than 45°, it is determined that the detection phase is in the non-conducting region, and the process jumps to step F.

[0090] Step E, set the current threshold i th2 (current threshold i) th2 (Take 130% of the current chopping limit value during motor operation). If the current i is measured in the conduction range... csa If the absolute value of the current (i.e., the winding current) exceeds the threshold, a chopper tube short-circuit fault is diagnosed. The system ends the diagnosis and jumps to step I; if the current is less than the threshold in the conduction range, the detection phase is diagnosed as not having a short-circuit fault. The system ends the diagnosis and jumps to step I.

[0091] Step F: Obtain the current values ​​at position angles of 22.5° and 25° respectively using the rotor position signal and current signal of phase A, and then proceed to step G;

[0092] Step G: Compare the current values ​​corresponding to these two position angles. If the absolute value of the current value corresponding to the position angle of phase A at 22.5° or 25° is found to be greater than the preset current threshold i, then... th3 (current threshold i) th3 If the current value at a position angle of 22.5° when the motor is running normally is 4A, then it is determined that a short circuit fault has occurred in the switching transistor, and the process jumps to step H.

[0093] Step H, when the current sensor measurement value i csa When the value is less than 0, the system diagnoses a short circuit fault in the conductive tube, terminates the diagnosis, and jumps to step I; when the current sensor measurement value i at this time... csa When the value is greater than 0, the system diagnoses a chopper tube short circuit fault, the system ends the diagnosis, and jumps to step I;

[0094] Step I, the dynamic diagnostic process ends, and the next diagnostic cycle begins.

Claims

1. A dynamic diagnostic method for short-circuit faults in SRM switching transistors using current shifting, characterized in that, Using an asymmetrical half-bridge power converter for a switched reluctance motor, when each phase of the switched reluctance motor is in the conduction range, the upper switch of each phase bridge arm of the power converter acts as a chopper and the lower switch acts as a conductor. Combined with the phase current waveform shift, each phase is taken as the target phase, and the following steps are performed to achieve rapid diagnosis of short circuit faults in the target phase switch. Step A: Obtain the position signal from the position sensor and calculate the actual speed of the switched reluctance motor drive system based on the position signal. Determine the state of the switched reluctance motor drive system. If the difference between the preset reference speed and the actual speed is... Less than the preset speed threshold n th If the condition is met, the switched reluctance motor drive system is determined to be in a steady-state operation and the process jumps to step B; otherwise, the switched reluctance motor drive system is determined to be in a dynamic operation and the process jumps to step J. Step B: Enter the steady-state diagnostic process, obtain the current sensor measurement value by measuring the target phase using the current sensor, and then proceed to step C; The current sensor is connected as follows: The other end of the wire of the switch S1 passes through the current sensor CS1 in the forward direction and is connected to one end of the A-phase winding. Then, the wire connected to the cathode of diode D2 passes through the current sensor CS1 in the reverse direction and is connected to the same end of the A-phase winding. The other end of the wire of the switch S3 passes through the current sensor CS2 in the forward direction and is connected to one end of the B-phase winding. Then, the wire connected to the cathode of diode D4 passes through the current sensor CS2 in the reverse direction and is connected to the same end of the B-phase winding. The other end of the wire of the switch S5 passes through the current sensor CS3 in the forward direction and is connected to one end of the C-phase winding. Then, the wire connected to the cathode of diode D6 passes through the current sensor CS3 in the reverse direction and is connected to the same end of the C-phase winding. Step C: After processing the absolute value of the current sensor measurement to obtain the actual phase current value of the target phase, proceed to step D; Step D: Calculate the electrical cycle and shift the current signal of the previous electrical cycle by one electrical cycle to achieve the shifting of the target phase current signal. Use the current waveform after shifting by one electrical cycle as the target phase current reference waveform for the current electrical cycle, and then obtain the reference current value for the current electrical cycle. Proceed to step E. Step E: Calculate the difference between the actual current value of the target phase and the reference current value corresponding to the current electrical cycle. If the difference The absolute value is greater than the preset threshold i th1 If the absolute value of the difference ∆ is less than or equal to the preset threshold i, then proceed to step F; th1 If so, proceed to step I; Step F: Obtain the current position angle of the target phase through the position sensor. If the current position angle is greater than or equal to 0° and less than or equal to 17°, it is determined that the detection phase is in the conducting region and the process jumps to step G; if the current position angle is greater than 17° and less than 45°, it is determined that the detection phase is in the non-conducting region and the process jumps to step H. Step G: When the target phase is detected to be in the conduction region, the difference between the actual phase current value and the reference current value corresponding to the current electrical cycle is detected. The absolute value is greater than the preset threshold i th1 If the test result is positive, the chopper tube is diagnosed as short-circuited. The diagnosis ends, and the process jumps to step I. Step H: When the target phase is detected to be in the non-conducting region, if the difference between the actual phase current value and the reference current value corresponding to the current electrical cycle is detected... The absolute value is greater than the preset threshold i th1 And the current sensor measured value i csa If the sign is positive, the diagnosis is a short circuit in the detection phase chopper; if the difference between the actual phase current value and the reference current value corresponding to the current electrical cycle is detected... The absolute value is greater than the preset threshold i th1 And the current sensor measured value i csa If the sign is negative, the diagnosis is a short circuit in the detection phase conductive tube, the diagnosis ends, and the process jumps to step I; Step I: Proceed to the next diagnostic cycle, then skip to Step A; Step J: Enter the dynamic diagnostic process, then proceed to step K; Step K: Obtain the current position angle through the position sensor. If the current position angle is greater than or equal to 0° and less than or equal to 17°, it is determined that the detection phase is in the conduction region and the process jumps to step M. If the current position angle is greater than 17° and less than 45°, it is determined that the detection phase is in the non-conducting region, and the process jumps to step L. Step M: Set the current threshold i th2 If the current i is measured in the conduction interval csa The absolute value exceeds the current threshold i th2 If the system detects a short circuit in the chopper tube, the system terminates the diagnosis and jumps to step P. If the current is less than the current threshold i during the conduction interval th2 If the system detects that no short circuit fault has occurred in the detected phase, the system will end the diagnosis and jump to step P. Step L: Obtain the current values ​​at position angles of 22.5° and 25° respectively using the rotor position signal and current signal of the target phase, and then proceed to step N; Step N: Compare the current values ​​corresponding to these two position angles. If the absolute value of the current value corresponding to position angle 22.5° or 25° is found to be greater than the preset current threshold i, then... th3 If the circuit is short-circuited, it is determined that a short circuit fault has occurred in the switching transistor, and the process jumps to step O. Step O: When the current sensor measurement value i of the target phase is at this time csa When the value is less than 0, the system diagnoses a short circuit fault in the conductive tube, terminates the diagnosis, and jumps to step P; when the current sensor measurement value i at this time... csa When the value is greater than 0, the system diagnoses a chopper tube short-circuit fault, the system terminates the diagnosis, and jumps to step P; when the current sensor measurement value i at this time... csa When the value is equal to 0, the diagnostic process continues running in step O until the current sensor measurement value i is reached. csa The signs can be positive or negative; Step P: The dynamic diagnostic process ends, and the next diagnostic cycle begins. Proceed to Step A.

2. The dynamic diagnosis method for short-circuit faults of SRM switching transistors using current shifting as described in claim 1, characterized in that, In step A, the rotational speed threshold n th Take 120% of the speed fluctuation value when the motor is running in normal steady state.

3. The dynamic diagnosis method for short-circuit faults of SRM switching transistors using current shifting as described in claim 1, characterized in that, The steps to achieve the phase current shift in step D are as follows: Step A: Measure the rotor position angle of the detection phase using a position sensor, then differentiate the rotor position angle to obtain the angular velocity, and finally convert the angular velocity into the rotational speed n using the quantitative relationship between the angular velocity and the rotational speed. Step B, since the electric cycle T and the rotational speed n have the following numerical relationship, the relationship is as follows: ； Since the motor used is a 12 / 8 switched reluctance motor, N r It is 8; Step C: Based on the calculated rotational speed, the current measurement signal is shifted backward by one electrical cycle. Then, the difference between the real-time current value obtained through the current sensor and the reference current value corresponding to the current electrical cycle is used to obtain the current error value. .

4. The dynamic diagnosis method for short-circuit faults of SRM switching transistors using current shifting as described in claim 1, characterized in that, In step G, the difference between the actual phase current value and the reference current value corresponding to the current electrical cycle is detected. The absolute value is greater than the preset threshold i th1 When the switching transistor is operating normally, the current error calculated by the current shift method is between (-0.2, 0.2). A threshold value i is set. th1 It is 0.

4.

5. The dynamic diagnosis method for short-circuit faults of SRM switching transistors using current shifting as described in claim 1, characterized in that, In step M, the current threshold i th2 Take 130% of the current chopping limit value when the motor is running.

6. The dynamic diagnosis method for short-circuit faults of SRM switching transistors using current shifting as described in claim 1, characterized in that, In step N, the current threshold i th3 Take the current value of 4A when the motor is in normal operation at a position angle of 22.5°.

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