A Fault Diagnosis Method for Switching Tubes Based on the Per-Unit Average Value of Phase Current
By calculating the average value of the phase current standard unit and combining the motor's back potential self-injection and main power injection methods, a current path injection diagnostic pulse is constructed, which solves the problem of inaccurate single-tube fault diagnosis in traditional methods, and achieves rapid and accurate positioning of switching tube faults, improving the operation safety of the sinusoidal electric excitation double-pole motor.
Patent Information
- Application Number
- CN202411936612.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-07-18
- Estimated Expiration
- 2044-12-26
AI Technical Summary
The traditional open circuit fault diagnosis method based on the average value of the phase current standard unit can only realize single-tube open circuit fault diagnosis, resulting in low accuracy of diagnosis results, affecting the operation safety of the sinusoidal electric excitation double-pole motor.
By calculating the average value of the phase current standard and combining the motor's back potential self-injection and main power injection methods, a current path injection diagnostic pulse is built to accurately locate the switching tube faults, especially the accurate detection of single-tube and double-tube faults.
It improves the robustness and anti-interference of fault diagnosis, can complete fault positioning within one electrical cycle interval, avoids misdiagnosis under light load or no load, and significantly improves fault positioning speed and accuracy.
Smart Images
Figure CN119805302B_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of aviation motor control, and in particular to a switching tube fault diagnosis method based on the per-unit average value of phase current. Background Technique
[0002] The Sinusoidal Doubly Salient Electromagnetic Machine (SDSEM) is a new type of reluctance motor, which has the advantages of simple rotor structure, low manufacturing cost, strong high-temperature and high-speed operation ability, and the ability to demagnetize in time during faults. Moreover, its torque ripple is smaller than that of traditional doubly salient electromagnetic machines, and it has broad application prospects in high-demand fields such as aviation, new energy power generation, and electric vehicles.
[0003] As the core component of the driving system of the sinusoidal doubly salient electromagnetic machine, the stable and reliable operation performance of the main power converter is the key factor to ensure the stable operation of the sinusoidal doubly salient electromagnetic machine. As an important carrier for implementing various control strategies, the main power converter often bears high voltage and large current in the system, and is a weak link prone to faults in the system. Especially the open-circuit fault of the switching tube in the main power converter seriously affects the performance of the motor drive system and even damages the sinusoidal doubly salient electromagnetic machine.
[0004] The traditional method for open-circuit fault diagnosis based on the per-unit average value of phase current can only realize single-tube open-circuit fault diagnosis. The limitation of this method leads to low accuracy of the diagnosis result, thus affecting the operation safety of the sinusoidal doubly salient electromagnetic machine. Summary of the Invention
[0005] In view of the above problems and technical requirements, the present application proposes a switching tube fault diagnosis method based on the per-unit average value of phase current, which is applied to an open-winding SDSEM drive system. The main power converter in the open-winding SDSEM drive system includes two three-arm inverters. One end of the A, B, and C phase armature windings of the open-winding SDSEM is respectively connected to the midpoint of three first arms in one three-arm inverter, and the other end of the A, B, and C phase armature windings is respectively connected to the midpoint of three second arms in the other three-arm inverter. The technical solution of the present application is as follows:
[0006] A switching tube fault diagnosis method based on the per-unit average value of phase current includes the following steps:
[0007] Determine the per-unit average value D of the phase current of the p-phase armature winding within the nearest electrical cycle interval at the current electrical angle position θ p , where p = a, b, c respectively represent the A, B, and C phase armature windings;
[0008] When the per-unit average value D of the phase current is detected p and the absolute value |D p | is within the error range of 1, it is determined that there is an open-circuit fault in the switching tubes in two bridge arms connected to the p-phase armature winding; according to the positive or negative value of the per-unit average value D of the phase current p , the faulty switching tube pair connected to the p-phase armature winding is located. Each switching tube pair includes the upper-bridge switching tube in one bridge arm and the lower-bridge switching tube in the other bridge arm connected to the p-phase armature winding;
[0009] Within the conduction sector of the non-faulty switching tube pair connected to the p-phase armature winding, keep the two switching tubes in the non-faulty switching tube pair turned off, and use the switching tubes in the faulty switching tube pair connected to the p-phase armature winding to construct a current path to inject a diagnostic pulse into the p-phase armature winding, and determine the switching tube with an open-circuit fault in the faulty switching tube pair according to the response current of the p-phase armature winding after the diagnostic pulse is injected.
[0010] A further technical solution thereof is that injecting a diagnostic pulse into the p-phase armature winding includes:
[0011] When the faulty switching tube pair is located within the conduction sector of the faulty switching tube pair connected to the p-phase armature winding, continue to maintain the current operating state until entering the conduction sector of the non-faulty switching tube pair connected to the p-phase armature winding, and use the switching tubes in the faulty switching tube pair of the p-phase armature winding and the anti-parallel diodes of the switching tubes in the non-faulty switching tube pair to construct a current path to inject a diagnostic pulse into the p-phase armature winding through the back electromotive force self-injection method.
[0012] A further technical solution thereof is that injecting a diagnostic pulse into the p-phase armature winding includes:
[0013] When the faulty switching tube pair is located within the conduction sector of the non-faulty switching tube pair connected to the p-phase armature winding, and it is determined according to the fault detection position θ0 that the remaining conduction width of the non-faulty switching tube pair in the current conduction sector meets the diagnostic pulse width requirement, use the switching tubes in the faulty switching tube pair of the p-phase armature winding and the anti-parallel diodes of the switching tubes in the non-faulty switching tube pair to construct a current path to inject a diagnostic pulse into the p-phase armature winding through the back electromotive force self-injection method.
[0014] A further technical solution thereof is that injecting a diagnostic pulse into the p-phase armature winding includes:
[0015] When a faulty switch pair is located within the conduction sector of the non-faulty switch pair connected to the p-phase armature winding, and according to the fault detection position θ0, it is determined that the remaining conduction width of the non-faulty switch pair within the current conduction sector does not meet the diagnostic pulse width requirement, the current operating state is maintained until the next conduction sector of the non-faulty switch pair. Then, a current path is constructed using the switches in the faulty switch pair of the p-phase armature winding and the anti-parallel diodes of the switches in the non-faulty switch pair, and a diagnostic pulse is injected into the p-phase armature winding through the back electromotive force self-injection method.
[0016] A further technical solution thereof is that the midpoint of each first bridge arm in the open-winding SDSEM is connected to the midpoint of a second bridge arm through a bidirectional switch tube, and the switching state of the upper bridge arm switch of the first bridge arm connected by the same bidirectional switch tube is the same as the switching state of the upper bridge arm switch of the second bridge arm it is connected to, and the switching state of the lower bridge arm switch of the first bridge arm connected by the same bidirectional switch tube is the same as the switching state of the lower bridge arm switch of the second bridge arm it is connected to;
[0017] Injecting a diagnostic pulse into the p-phase armature winding includes:
[0018] When a faulty switch pair is located within the conduction sector of the non-faulty switch pair connected to the p-phase armature winding, and according to the fault detection position θ0, it is determined that the remaining conduction width of the non-faulty switch pair within the current conduction sector does not meet the diagnostic pulse width requirement, a current path is constructed using the switches in the faulty switch pair of the p-phase armature winding and the bidirectional switch tubes connected to the p-phase armature winding, and a diagnostic pulse is injected into the p-phase armature winding through the main power supply injection method.
[0019] A further technical solution thereof is that injecting a diagnostic pulse into the p-phase armature winding through the back electromotive force self-injection method includes:
[0020] Controlling the two switches in the faulty switch pair connected to the p-phase armature winding to conduct single-tube conduction in sequence. When the response current of the p-phase armature winding during single-tube conduction reaches the threshold value i th at this time, it is determined that the turned-off switch in the faulty switch pair has an open-circuit fault and the conducting switch is working normally;
[0021] When the response current of the p-phase armature winding during single-tube conduction does not reach the threshold value i th at this time, it is determined that both switches in the faulty switch pair have open-circuit faults.
[0022] A further technical solution thereof is that injecting a diagnostic pulse into the p-phase armature winding through the main power supply injection method includes:
[0023] The two switching tubes in the faulty switching tube pair controlling the connection of the p-phase armature winding are sequentially turned on individually. When one of the switching tubes in the faulty switching tube pair is turned on, the bidirectional switching tube connected to the arm of the other switching tube is turned on, while the other two bidirectional switching tubes are turned off, forming a current path between the main power supply, the turned-on switching tube in the faulty switching tube pair, the p-phase armature winding, the turned-on bidirectional switching tube, and the switching tube in the main power converter with the same switching state as the turned-off switching tube in the faulty switching tube pair, and injecting a diagnostic pulse. When the response current of the p-phase armature winding during the individual turn-on process reaches the threshold i th , it is determined that the turned-off switching tube in the faulty switching tube pair has an open-circuit fault and the turned-on switching tube is operating normally;
[0024] When the response current of the p-phase armature winding during the individual turn-on process does not reach the threshold i th , it is determined that both switching tubes in the faulty switching tube pair have open-circuit faults.
[0025] A further technical solution is that, with the direction from the midpoint of the first arm connected to the p-phase armature winding to the midpoint of the second arm as the positive current direction, according to the per-unit average value D p of the phase current, the faulty switching tube pair connected to the p-phase armature winding is located as follows:
[0026] When the per-unit average value D p of the phase current is within the error range of -1, it is determined that the switching tube pair composed of the upper switching tube of the first arm and the lower switching tube of the second arm connected to the p-phase armature winding belongs to the faulty switching tube pair;
[0027] When the per-unit average value D p of the phase current is within the error range of 1, it is determined that the switching tube pair composed of the lower switching tube of the first arm and the upper switching tube of the second arm connected to the p-phase armature winding belongs to the faulty switching tube pair.
[0028] A further technical solution is that detecting whether the remaining conduction width of the non-faulty switching tube pair in the current conduction sector meets the diagnostic pulse width requirement includes:
[0029] When it is detected that the fault detection position θ0 is not less than the diagnostic pulse injection width θ2 of the back-electromotive force self-injection method from the end position of the current conduction sector of the non-faulty switching tube pair connected to the p-phase armature winding, it is determined that the remaining conduction width of the non-faulty switching tube pair in the current conduction sector meets the diagnostic pulse width requirement; otherwise, it is determined that the remaining conduction width of the non-faulty switching tube pair in the current conduction sector does not meet the diagnostic pulse width requirement.
[0030] Its further technical solution is that, according to the characteristics of instantaneously injecting diagnostic pulses in the main power supply injection mode, the injection width θ4 of the diagnostic pulses in the main power supply injection mode is less than the injection width θ2 of the diagnostic pulses in the back electromotive force self-injection mode. When the remaining conduction width of the non-faulty switch tube pair in the current conduction sector is less than the injection width θ2 of the diagnostic pulses in the back electromotive force self-injection mode, a current path is constructed by using the switch tube in the faulty switch tube pair of the p-phase armature winding and the bidirectional switch tube connected to the p-phase armature winding, and diagnostic pulses are injected into the p-phase armature winding through the main power supply injection mode.
[0031] The beneficial technical effects of this application are as follows:
[0032] A switch tube fault diagnosis method based on the per-unit average value of phase current proposed in this application can achieve open-circuit fault detection, determine the faulty phase and the faulty switch tube pair by calculating the average value of the phase current within an electrical cycle interval and performing per-unit conversion. It can avoid false diagnosis caused by too small load current under light load or no-load conditions, and effectively improve the robustness and anti-interference ability of the fault diagnosis method. The method of constructing a current path by using the switch tube in the faulty switch tube pair to inject diagnostic pulses can accurately locate the switch tube with an open-circuit fault in the faulty switch tube pair. Compared with the traditional per-unit average value fault diagnosis method of phase current, it can not only accurately locate single-tube faults, but also accurately locate double-tube faults.
[0033] By using the back electromotive force self-injection diagnostic pulses of the motor, on the basis of realizing single-tube and double-tube fault detection, it can accurately locate the specific switch tube with an open-circuit fault only by using the back electromotive force of the motor in the open-winding SDSEM drive system itself, and effectively improve the speed of fault location. By analyzing the fault detection position to determine the diagnostic pulse injection mode and combining the back electromotive force self-injection mode with the main power supply injection mode, the speed of fault location is further improved, ensuring that the fault location is completed within an electrical cycle interval, and solving the problem of false diagnosis caused by the failure of fault location feature extraction due to the long fault detection time of the traditional per-unit average value fault diagnosis method of phase current. The method of this application is simple to implement and has a low cost, can make full use of the advantages of different diagnostic pulse injection modes, and significantly improve the fault location speed. Description of the Drawings
[0034] Figure 1 It is the topological structure diagram of the open-winding SDSEM drive system.
[0035] Figure 2 It is the flow chart of the switch tube fault diagnosis method.
[0036] Figure 3 It is the forward current loop when the switch tube T1 has an open-circuit fault.
[0037] Figure 4It is a schematic diagram of the switching transistor pair connected to the A-phase armature winding.
[0038] Figure 5 It is a schematic diagram of the fault detection interval and the diagnostic pulse injection interval.
[0039] Figure 6 It is the current flow path after the back electromotive force is self-injected during the open-circuit fault of T1.
[0040] Figure 7 It is the current flow path after the back electromotive force is self-injected during the open-circuit fault of T8.
[0041] Figure 8 It is the motor back electromotive force and the response current after the back electromotive force is self-injected during the open-circuit fault of T1.
[0042] Figure 9 It is the motor back electromotive force and the response current after the back electromotive force is self-injected during the open-circuit fault of T8.
[0043] Figure 10 It is the motor back electromotive force and the response current after the back electromotive force is self-injected during the open-circuit faults of T1 and T8.
[0044] Figure 11 It is the topological structure diagram of the open-winding SDSEM drive system with added bidirectional switching transistors.
[0045] Figure 12 It is the current flow path after the main power supply is injected during the open-circuit fault of T1.
[0046] Figure 13 It is the current flow path after the main power supply is injected during the open-circuit fault of T8. Specific implementation manners
[0047] The following further describes the specific implementation manners of the present application with reference to the accompanying drawings.
[0048] Compared with the star connection topological structure of the traditional sine-type electric-excited doubly salient motor drive system, a switching transistor fault diagnosis method based on the per-unit average value of the phase current proposed by the present application is applied to the open-winding SDSEM drive system. The open-winding SDSEM drive system of the present application opens the neutral points of the three-phase armature windings, and the specific structure is as Figure 1As shown in the figure, the main power converter in the open-winding SDSEM drive system includes two three-leg inverters. One end of each of the A, B, and C phase armature windings of the open-winding SDSEM is respectively connected to the midpoint of three first legs in one three-leg inverter, and the other end of each of the A, B, and C phase armature windings is respectively connected to the midpoint of three second legs in the other three-leg inverter. A total of 4 switching tubes are connected to both ends of each phase armature winding, and each switching tube is anti-parallel with a diode. Compared with the single-inverter structure of the traditional sinusoidal electro-magnetic double salient pole motor drive system, the open-winding SDSEM drive system has better fault tolerance and flexibility. When a switching tube in one inverter fails, the lower legs of each phase of this inverter can be turned on, while the other inverter remains normal. At this time, the dual-inverter system becomes a single-inverter operating state, and constant-torque half-speed operation can be achieved, thus ensuring the safe operation of the system.
[0049] Based on the above open-winding SDSEM drive system structure, a method for diagnosing open-circuit faults of switching tubes in an open-winding SDSEM drive system proposed in this application is as follows. Please refer to Figure 2 the flowchart shown in the figure, and the specific steps are as follows:
[0050] Step 1: Sample the phase current of the p-phase armature winding in the most recent electrical cycle interval at the current electrical angle position θ in a sliding cycle manner and determine the per-unit average value D of the phase current p , where p = a, b, c respectively represent the A, B, and C phase armature windings.
[0051] When an open-circuit fault occurs in the switching tube of the power converter of the open-winding sinusoidal electro-magnetic double salient pole motor, the power converter cannot output all voltage vectors, resulting in distortion of the stator current. Due to the freewheeling effect of the diodes anti-parallel with the switching tubes in the three-leg inverter, the open-circuit fault of the switching tube only affects the current waveform in half of the electrical cycle.
[0052] Taking the open-circuit fault of switching tube T1 as an example for analysis, with the direction from the midpoint of the first leg connected to the p-phase armature winding to the midpoint of the second leg as the positive current direction, and the direction from a1 to a2 connected to the A-phase armature winding as the positive current direction. The forward current loop formed by the switching tubes connected to the A-phase armature winding is as Figure 3 shown in the figure. Among them, the forward current loop with only T1 turned on is as Figure 3 (a) shown. When an open-circuit fault occurs in T1, it only affects the Figure 3 (a) shown forward current of the current loop. Due to the open circuit of T1, the forward current loop changes from Figure 3 (a) to Figure 3 (d), accelerating the decay of the forward current. When T1 and T8 are turned on simultaneously, due to the open circuit of T1, the forward current loop changes from Figure 3 (b) to Figure 3(c) impedes the increase of the positive current. Therefore, when an open - circuit fault occurs in the switching transistor T1, the phase - A current i a will exhibit a relatively obvious negative bias, or even only a negative current. Similarly, when an open - circuit fault occurs in the switching transistor T8, the phase - A current i a will also exhibit a relatively obvious negative bias, or even only a negative current. Similarly, when an open - circuit fault occurs in the switching transistor T7 or T9, the phase - A current i a will exhibit a relatively obvious positive bias, or even only a positive current.
[0053] Since the two three - leg inverters in the open - winding sinusoidal electro - magnetic - field - excited doubly salient motor drive system have a certain symmetry, the two switching transistors (such as T1 and T8, T2 and T7) that are simultaneously turned on in the positive or negative direction of the current in the same phase have the same open - circuit fault characteristics. Define the upper - leg switching transistor in one leg and the lower - leg switching transistor in the other leg connected to the p - phase armature winding as a switching - transistor pair. The switching - transistor pairs connected to the phase - A armature winding are as Figure 4 shown. T1 and T8 form a switching - transistor pair, and T2 and T7 form a switching - transistor pair; for the phase - B armature winding, T3 and T 10 form a switching - transistor pair, and T4 and T9 form a switching - transistor pair; for the phase - C armature winding, T5 and T 12 form a switching - transistor pair, and T6 and T 11 form a switching - transistor pair.
[0054] According to the above analysis, an open - circuit fault in the switching transistor will cause partial loss of the phase - current waveform, resulting in a bias in the average value of the phase - current period. Therefore, fault detection can be achieved by the average value of the phase current in an electrical - cycle interval, and the faulty phase and the faulty switching - transistor pair can be determined. However, since the magnitude of the average value of the phase current is easily affected by the load current, when the motor is lightly loaded or unloaded, the phase current is small or even close to 0, which may cause misdiagnosis. To improve the robustness and anti - interference ability of the fault - diagnosis method, the average value of the phase current is normalized. Define the ratio of the average value of the phase current in an electrical - cycle interval to the average value of the absolute value of the phase current as the per - unit average value of the phase current where T is the length of an electrical - cycle interval.
[0055] Step 2: When the absolute value |D p | of the per - unit average value D p of the phase current is within the error range of 1, it is determined that there is an open - circuit fault in the switching transistors in the two legs connected to the p - phase armature winding. Locate the faulty switching - transistor pair connected to the p - phase armature winding according to the positive or negative value of the per - unit average value D p of the phase current.
[0056] When no fault occurs, D pThe value is 0; when an open - circuit fault occurs in a switching tube, the D of the faulty phase p takes a value of - 1 or 1. Due to the vector control effect, the three - phase current will have a co - directional DC bias. The D of the non - faulty phase p takes a value of 0 < |D p | < 1. The occurrence of an open - circuit fault can be detected and the faulty phase can be judged through the value of D p . Considering factors such as sampling accuracy and external interference, the fault - detection expression is:
[0057]
[0058] where ε is an infinitesimal positive number, D a is the per - unit average value of the phase current of the A - phase armature winding, D b is the per - unit average value of the phase current of the B - phase armature winding, D c is the per - unit average value of the phase current of the C - phase armature winding.
[0059] In one embodiment, according to the positive or negative value of the per - unit average value D p of the phase current, the faulty switching - tube pair connected to the p - phase armature winding is located as follows: when the per - unit average value D p is within the error range of - 1, it is determined that the switching - tube pair composed of the upper switching tube of the first bridge arm and the lower switching tube of the second bridge arm connected to the p - phase armature winding belongs to the faulty switching - tube pair; when the per - unit average value D p is within the error range of 1, it is determined that the switching - tube pair composed of the lower switching tube of the first bridge arm and the upper switching tube of the second bridge arm connected to the p - phase armature winding belongs to the faulty switching - tube pair.
[0060] Taking the A - phase as an example, when an open - circuit fault occurs in a switching tube of the switching - tube pair T1 and T8, the positive - half - cycle of the current waveform is missing, and D a takes a value near - 1; when an open - circuit fault occurs in a switching tube of the switching - tube pair T2 and T7, the negative - half - cycle of the current waveform is missing, and D a takes a value near 1. The same is true for the B - phase and C - phase. Therefore, the faulty switching - tube pair can be judged according to the positive or negative value of D p of the faulty phase. The relationship between the faulty switching - tube pair and D p is as follows:
[0061]
[0062] When an open - circuit fault occurs in the switching tubes in the same switching - tube pair, there are the same fault - current characteristics, and further precise positioning of the faulty switching tube is required.
[0063] Step 3, within the conduction sector of the non-faulty switch pair connected to the p-phase armature winding, keep the two switches in the non-faulty switch pair off, and use the switches in the faulty switch pair connected to the p-phase armature winding to construct a current path to inject a diagnostic pulse into the p-phase armature winding, and determine the switch with an open-circuit fault in the faulty switch pair according to the response current of the p-phase armature winding after the diagnostic pulse is injected.
[0064] When one of the switches in the switch pair in the positive current loop connected to the p-phase armature winding has an open-circuit fault, the power supply can no longer provide positive energy to the faulty phase, so the positive half-cycle of the phase current is missing. However, thanks to the strong fault-tolerant operation ability of the open-winding SDSEM drive system, the other two non-faulty phases can still maintain the operation of the motor. At this time, the faulty phase changes from the electric mode to the generating mode.
[0065] Within an electrical angle cycle, the conduction sectors of the faulty switch pair and the non-faulty switch pair of the faulty phase each account for half of the electrical angle cycle, and the motor back electromotive force generated by the conduction of the faulty switch pair is opposite to the direction of the motor back electromotive force generated by the conduction of the non-faulty switch pair. Moreover, due to the freewheeling effect of the anti-parallel diodes of the switches, the diagnostic pulse can be self-injected by using the motor back electromotive force generated by the non-faulty switch pair within the conduction sector through the loop formed by the anti-parallel diodes of the non-faulty switches and the faulty switches. For the case where the faulty switch pair is in the positive current loop, only a positive loop that satisfies the independent operation of any one switch needs to be provided, and then the diagnostic pulse can be injected by using the motor back electromotive force generated by the non-faulty switch pair within the conduction sector, and then observe whether a positive response current is generated to locate the faulty switch. On the contrary, for the case where the faulty switch pair is in the negative current loop, only a negative loop that satisfies the independent operation of any one switch needs to be provided, and then the diagnostic pulse can be injected by using the motor back electromotive force generated by the non-faulty switch pair within the conduction sector, and then observe whether a negative response current is generated to locate the faulty switch.
[0066] Since the open - circuit fault occurs within the conduction sector of the faulty switch - tube pair, and calculating the per - unit average value of the phase current requires collecting the phase current within an entire electrical - cycle interval, it is impossible to immediately detect the fault when the open - circuit fault occurs. Moreover, due to the use of sliding - period sampling to calculate the average value, according to the value characteristics of the per - unit average value of the phase current, the fault - detection position of the open - circuit fault may appear within the conduction sector of the faulty switch - tube pair in the current period, or within the conduction sector of the non - faulty switch - tube pair, or within the conduction sector of the faulty switch - tube pair in the next period. Among them, the conduction sector of the faulty switch - tube pair refers to the conduction electrical - angle interval of the faulty switch - tube pair within an electrical - cycle interval during normal motor operation, and the conduction sector of the non - faulty switch - tube pair refers to the conduction electrical - angle interval of the non - faulty switch - tube pair within an electrical - cycle interval during normal motor operation. Taking the electrical - cycle interval with a length of \(2\pi\) as an example, when the open - circuit fault occurs in the interval \((-\pi,0)\), since the fault can only be detected after the fault - occurrence position, and the per - unit average value of the phase current needs to calculate the phase current within an electrical - cycle interval, the fault - detection position is within the interval \((-\pi,2\pi)\), as Figure 5 shown. The fault - detection interval is divided into 4 fault - detection sub - intervals. The first sub - interval is the conduction sector of the faulty switch - tube pair connected to the p - phase armature winding. The second and third sub - intervals are the conduction sectors of the non - faulty switch - tube pairs connected to the p - phase armature winding. The fourth sub - interval is the next conduction sector of the non - faulty switch - tube pair connected to the p - phase armature winding.
[0067] \(\theta_2\) is the diagnostic - pulse injection width of the back - electromotive - force self - injection method. According to \(\theta_2\), the second and third sub - intervals can be divided. When the fault - detection position is within the second sub - interval, the remaining conduction width of the non - faulty switch - tube pair within the current conduction sector meets the diagnostic - pulse injection - width requirement of the back - electromotive - force self - injection method. When the fault - detection position is within the third sub - interval, the remaining conduction width of the non - faulty switch - tube pair within the current conduction sector does not meet the diagnostic - pulse injection - width requirement of the back - electromotive - force self - injection method. In one embodiment, detecting whether the remaining conduction width of the non - faulty switch - tube pair within the current conduction sector meets the diagnostic - pulse - width requirement includes: when it is detected that the distance \(\theta_0\) of the fault - detection position from the end position of the current conduction sector of the non - faulty switch - tube pair connected to the p - phase armature winding is not less than the diagnostic - pulse injection width \(\theta_2\) of the back - electromotive - force self - injection method, it is determined that the remaining conduction width of the non - faulty switch - tube pair within the current conduction sector meets the diagnostic - pulse - width requirement; otherwise, it is determined that the remaining conduction width of the non - faulty switch - tube pair within the current conduction sector does not meet the diagnostic - pulse - width requirement.
[0068] For the case where the faulty switch tube is located within each fault detection sub-interval, it is necessary to determine an appropriate diagnostic pulse injection interval. In one embodiment, when the faulty switch tube pair is located within the conduction sector (the first sub-interval) of the switch tube pair connected to the p-phase armature winding, the current operating state is maintained until entering the conduction sector of the non-faulty switch tube pair connected to the p-phase armature winding. At this time, a current path is constructed using the switch tube in the faulty switch tube pair of the p-phase armature winding and the anti-parallel diodes of the switch tubes in the non-faulty switch tube pair, and a diagnostic pulse is injected into the p-phase armature winding through back electromotive force self-injection method.
[0069] When the faulty switch tube pair is located within the conduction sector (the second and third sub-intervals) of the non-faulty switch tube pair connected to the p-phase armature winding, and it is determined according to the fault detection position θ0 that the remaining conduction width of the non-faulty switch tube pair within the current conduction sector meets the diagnostic pulse width requirement, at this time the fault detection position θ0 is in the second sub-interval. A current path is constructed using the switch tube in the faulty switch tube pair of the p-phase armature winding and the anti-parallel diodes of the switch tubes in the non-faulty switch tube pair, and a diagnostic pulse is injected into the p-phase armature winding through back electromotive force self-injection method.
[0070] When the faulty switch tube pair is located within the conduction sector (the second and third sub-intervals) of the non-faulty switch tube pair connected to the p-phase armature winding, and it is determined according to the fault detection position θ0 that the remaining conduction width of the non-faulty switch tube pair within the current conduction sector does not meet the diagnostic pulse width requirement, at this time the fault detection position θ0 is in the third sub-interval. The current operating state is maintained until the next conduction sector of the non-faulty switch tube pair, and a current path is constructed using the switch tube in the faulty switch tube pair of the p-phase armature winding and the anti-parallel diodes of the switch tubes in the non-faulty switch tube pair, and a diagnostic pulse is injected into the p-phase armature winding through back electromotive force self-injection method.
[0071] In one embodiment, injecting a diagnostic pulse into the p-phase armature winding through back electromotive force self-injection method includes:
[0072] Controlling the two switch tubes in the faulty switch tube pair connected to the p-phase armature winding to conduct one by one. When the response current of the p-phase armature winding during the single-tube conduction reaches the threshold i th , it is determined that the turned-off switch tube in the faulty switch tube pair has an open-circuit fault and the conducting switch tube is working properly;
[0073] When the response current of the p-phase armature winding during the single-tube conduction does not reach the threshold i th , it is determined that both switch tubes in the faulty switch tube pair have open-circuit faults.
[0074] Taking the open - circuit fault of the switch - tube pair T1 and T8 connected to the A - phase armature winding as an example for analysis. When an open - circuit fault occurs in one of the switch - tubes in the switch - tube pair T1 and T8, the power supply cannot provide positive energy to the A - phase armature winding, and the positive half - cycle of the A - phase current is missing. However, thanks to the strong fault - tolerant operation ability of the open - winding SDSEM drive system, the motor can still be maintained in operation by phases B and C. At this time, phase A changes from the electric mode to the generating mode. Since the switch - tube pair T1 and T8 is in the positive - current loop, only a positive loop that satisfies the individual operation of T1 or T8 needs to be provided to inject the diagnostic pulse using the back - electromotive force of the motor.
[0075] When an open - circuit fault occurs in T1, the positive - current flow path is as Figure 6 shown. At this time, only by turning on T1 can the current path of the antiparallel diode D7 of T1 and T7 be constructed, so as to realize the self - injection of the back - electromotive - force diagnostic pulse and generate a positive response current. Similarly, when an open - circuit fault occurs in T8, the positive - current flow path is as Figure 7 shown. At this time, only by turning on T8 can the current path of the antiparallel diode D2 of T8 and T2 be constructed, so as to realize the self - injection of the back - electromotive - force diagnostic pulse and generate a positive response current. When open - circuit faults occur in T1 and T8, a positive loop that satisfies the individual operation of T1 or T8 cannot be provided, and there is no response current after the diagnostic pulse is self - injected. Therefore, the faulty switch - tube can be accurately located according to the characteristic of generating a response current after the diagnostic pulse is self - injected.
[0076] To prevent the negative current generated by the conduction of the non - faulty switch - tube pair to the main power supply from affecting the flow of the positive current generated by the back - electromotive force, after detecting the faulty switch - tube pair, immediately turn off the non - faulty switch - tube pair. Inject the diagnostic pulse by sequentially turning on the two switch - tubes of the faulty switch - tube one by one within the conduction sector of the non - faulty switch - tube.
[0077] Taking the faulty switch - tube pair T1 and T8 as an example, assuming the fault - detection position θ0 = 0, the specific process of fault - locating the faulty switch - tube pair T1 and T8 is as follows:
[0078] (1) When the electrical angle θ of the motor is in the interval (θ0, θ0+θ1), only turn on T8. θ1 is the width required for self - injection of the back - electromotive - force diagnostic pulse when a single switch - tube conducts. If it is detected that the response current reaches the threshold i th at this time, then immediately turn off T8 and determine that the upper - bridge - arm switch - tube T1 in the faulty switch - tube pair T1 and T8 has an open - circuit fault. The back - electromotive force and the response current of this back - electromotive - force self - injection process are as Figure 8 shown.
[0079] (2) When the electrical angle θ of the motor is in the interval (θ0+θ1, θ0+θ2), only turn on T1. If it is detected that the response current reaches the threshold i thWhen this occurs, T1 is immediately turned off, and it is determined that the lower-bridge arm switch T8 of the faulty switch pair T1 and T8 has an open-circuit fault. The back electromotive force and the response current during this back electromotive force self-injection process are as Figure 9 shown.
[0080] (3) When the electrical angle of the motor θ = θ0 + θ2, both T1 and T8 are turned off. If the response current is detected not to reach the threshold i th within the interval (θ0, θ0 + θ2), it is determined that both T1 and T8 of the faulty switch pair T1 and T8 have open-circuit faults. The back electromotive force and the response current during this back electromotive force self-injection process are as Figure 10 shown.
[0081] It should be noted that it is possible to start with either the upper-bridge arm switch or the lower-bridge arm switch of the faulty switch, as long as it is ensured that the two switches conduct separately in sequence.
[0082] As can be analyzed from the above, when the fault detection position θ0 is in the third sub-interval, the remaining conduction width of the non-faulty switch pair in the current conduction sector does not meet the diagnostic pulse width requirement, and it is necessary to delay until the next conduction sector of the non-faulty switch pair to achieve back electromotive force self-injection. To further improve the fault location speed and avoid being limited by the back electromotive force, when the fault detection position θ0 is in the third sub-interval, a current path can be constructed through the bidirectional switch and a single switch of the faulty switch pair to realize the injection of diagnostic pulses using the main power supply. The topological structure of the open-winding SDSEM drive system with an additional switch is as Figure 11 shown.
[0083] Since in the open-winding SDSEM drive system, the switching state of any arm of the three-arm inverter can always find an arm with the same switching state in another three-arm inverter. Among them, the switching state of T1 of the A-phase arm in different sectors is exactly the same as that of T9, the switching state of T3 of the B-phase arm is the same as that of T 11 in different sectors, and the switching state of T5 of the C-phase arm is the same as that of T7 in different sectors. Since the arms have the same switching combination, then the connection between one arm and the inverter is opened and connected to the arm with the same switching state. And because the switching states of the upper-bridge arm switch and the lower-bridge arm switch of the same arm are opposite, therefore, the switching states of T2 and T 10 are the same in different sectors, the switching states of T4 and T 12 are the same in different sectors, and the switching states of T6 and T8 are the same in different sectors.
[0084] Specifically, the midpoint of each first bridge arm in the open winding SDSEM is cross-connected to the midpoint of a second bridge arm through a bidirectional switch tube, and the switching state of the upper bridge arm switch tube of the first bridge arm cross-connected by the same bidirectional switch tube is the same as the switching state of the upper bridge arm switch tube of the second bridge arm it cross-connects. The switching state of the lower bridge arm switch tube of the first bridge arm cross-connected by the same bidirectional switch tube is the same as the switching state of the lower bridge arm switch tube of the second bridge arm it cross-connects.
[0085] When the fault detection position θ0 is in the third sub-interval, a current path can be constructed through a single switch tube of the bidirectional switch tube and the fault switch tube pair to inject a diagnostic pulse into the main power supply. In one embodiment, injecting a diagnostic pulse into the p-phase armature winding includes: when a fault switch tube pair is located within the conduction sector of the non-fault switch tube pair connected to the p-phase armature winding, and according to the fault detection position θ0, it is determined that the remaining conduction width of the non-fault switch tube pair within the current conduction sector does not meet the diagnostic pulse width requirement, a current path is constructed using the switch tube in the fault switch tube pair of the p-phase armature winding and the bidirectional switch tube connected to the p-phase armature winding, and a diagnostic pulse is injected into the p-phase armature winding through the main power supply injection method.
[0086] In one embodiment, injecting a diagnostic pulse into the p-phase armature winding through the main power supply injection method includes:
[0087] Controlling the two switch tubes in the fault switch tube pair connected to the p-phase armature winding to conduct single-tube conduction in sequence, and when one of the switch tubes in the conducting fault switch tube pair is conducting, controlling the bidirectional switch tube connected to the arm of the other switch tube to conduct, and keeping the other two bidirectional switch tubes off, forming a current path between the main power supply, the conducting switch tube in the conducting fault switch tube pair, the p-phase armature winding, the conducting bidirectional switch tube, and the switch tube in the main power converter with the same switching state as the non-conducting switch tube in the conducting fault switch tube pair, and injecting a diagnostic pulse. When the response current of the p-phase armature winding during single-tube conduction reaches the threshold i th When it reaches, it is determined that the non-conducting switch tube in the fault switch tube pair has an open-circuit fault and the conducting switch tube is working normally;
[0088] When the response current of the p-phase armature winding during single-tube conduction does not reach the threshold i th When it reaches, it is determined that both switch tubes in the fault switch tube pair have open-circuit faults.
[0089] Taking the fault switch tube pair T1 and T8 as an example, when the fault detection position θ0 is in the third sub-interval, the specific process of fault location of the fault switch tube pair T1 and T8 is as follows:
[0090] (1) When the electrical angle θ of the motor is in the interval (θ0, θ0 + θ3), only turn on T8 and the bidirectional switch tube VD 17, forming the main power supply, the conducting switch tube T8, the p-phase armature winding, the conducting bidirectional switch tube VD 17 , the forward current path between the switch tube T9 in the main power converter having the same switching state as the switch tube T1 that is turned off in the conduction fault switch tube pair is as follows: Figure 12 θ3 is the width required for a single switch tube to conduct the main power supply to inject a diagnostic pulse. If the response current is detected to reach the threshold i th When the fault occurs, T8 is immediately turned off and it is determined that an open circuit fault occurs in the upper arm switch tube T1 of the faulty switch tube pair T1 and T8.
[0091] (2) When the motor electrical angle θ is in the range of (θ0+θ3,θ0+θ4), only T1 and the bidirectional switch VD are turned on. 19 , forming the main power supply, the conducting switch tube T1, the p-phase armature winding, the conducting bidirectional switch tube VD 19 , the forward current path between the switch tube T6 in the main power converter having the same switching state as the switch tube T8 that is turned off in the on-fault switch tube pair is as follows: Figure 13 As shown. If the response current is detected to reach the threshold value i th When the fault occurs, T1 is immediately turned off and it is determined that an open circuit fault occurs in the lower arm switch tube T8 of the faulty switch tube pair T1 and T8.
[0092] (3) When the motor electrical angle θ = θ0 + θ4, T1 and T8 are all turned off. If the response current is detected to be less than the threshold value i in the interval (θ0, θ0 + θ4), th , it is determined that the faulty switch tube pair T1 and T8 has an open circuit fault.
[0093] Since the voltage of the main power supply is very large, the diagnostic pulse injection by the main power supply injection method has the characteristic of instantaneous injection, so the diagnostic pulse injection width θ4 of the main power supply injection method is much smaller than the diagnostic pulse injection width θ2 of the back-EMF self-injection method. Therefore, when the remaining conduction width of the non-fault switch tube pair in the current conduction sector is less than the diagnostic pulse injection width θ2 of the back-EMF self-injection method, the switch tube in the faulty switch tube pair of the p-phase armature winding and the bidirectional switch tube connected to the p-phase armature winding are used to construct a current path and inject diagnostic pulses into the p-phase armature winding by the main power supply injection method. This allows the fault location to be completed within one electrical cycle interval, solving the problem of slow diagnostic speed due to the fact that the conventional phase current per-unit average fault diagnosis requires at least two electrical cycle intervals.
[0094] The above is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.
Claims
1. A switching tube fault diagnosis method based on the per-unit average value of phase current, characterized in that Applied to an open - winding SDSEM drive system, the main power converter in the open - winding SDSEM drive system includes two three - leg inverters. One end of each of the A, B, and C phase armature windings of the open - winding SDSEM is respectively connected to the mid - point of three first legs in one three - leg inverter, and the other end of each of the A, B, and C phase armature windings is respectively connected to the mid - point of three second legs in the other three - leg inverter. The switch - tube fault diagnosis method includes: Determine the per-unit average value D of the phase current of the p-phase armature winding within the nearest electrical cycle interval at the current electrical angle position θ p , where p = a, b, c respectively represent the armature windings of phases A, B, and C; When the per-unit average value D of the phase current is detected p and the absolute value |D p | is within the error range of 1, it is determined that there is an open-circuit fault in the switching tubes in two bridge arms connected to the p-phase armature winding; based on the per-unit average value D of the phase current p the positive or negative value of D is used to locate the faulty switching tube pair connected to the p-phase armature winding, and each switching tube pair includes the upper-bridge switching tube in one bridge arm and the lower-bridge switching tube in the other bridge arm connected to the p-phase armature winding; In the conduction sector of the non - faulty switch - tube pair connected to the p - phase armature winding, keep the two switch tubes in the non - faulty switch - tube pair off, and use the switch tubes in the faulty switch - tube pair connected to the p - phase armature winding to construct a current path to inject a diagnostic pulse into the p - phase armature winding, and determine the switch tube with an open - circuit fault in the faulty switch - tube pair according to the response current of the p - phase armature winding after the diagnostic pulse is injected.
2. The switching tube fault diagnosis method according to claim 1, wherein Injecting a diagnostic pulse into the p - phase armature winding includes: When locating the faulty switch - tube pair in the conduction sector of the faulty switch - tube pair connected to the p - phase armature winding, continue to maintain the current operating state until entering the conduction sector of the non - faulty switch - tube pair connected to the p - phase armature winding. Then, use the switch tubes in the faulty switch - tube pair of the p - phase armature winding and the anti - parallel diodes of the switch tubes in the non - faulty switch - tube pair to construct a current path to inject a diagnostic pulse into the p - phase armature winding through the back - EMF self - injection method.
3. The switch tube fault diagnosis method according to claim 1, characterized in that Injecting a diagnostic pulse into the p - phase armature winding includes: When locating the faulty switch - tube pair in the conduction sector of the non - faulty switch - tube pair connected to the p - phase armature winding, and when it is determined according to the fault detection position θ0 that the remaining conduction width of the non - faulty switch - tube pair in the current conduction sector meets the diagnostic pulse width requirement, use the switch tubes in the faulty switch - tube pair of the p - phase armature winding and the anti - parallel diodes of the switch tubes in the non - faulty switch - tube pair to construct a current path to inject a diagnostic pulse into the p - phase armature winding through the back - EMF self - injection method.
4. The switch tube fault diagnosis method according to claim 1, wherein Injecting a diagnostic pulse into the p - phase armature winding includes: When locating the faulty switch - tube pair in the conduction sector of the non - faulty switch - tube pair connected to the p - phase armature winding, and when it is determined according to the fault detection position θ0 that the remaining conduction width of the non - faulty switch - tube pair in the current conduction sector does not meet the diagnostic pulse width requirement, maintain the current operating state until the next conduction sector of the non - faulty switch - tube pair, and then use the switch tubes in the faulty switch - tube pair of the p - phase armature winding and the anti - parallel diodes of the switch tubes in the non - faulty switch - tube pair to construct a current path to inject a diagnostic pulse into the p - phase armature winding through the back - EMF self - injection method.
5. The switch tube fault diagnosis method according to claim 1, wherein The mid - point of each first leg in the open - winding SDSEM is connected to the mid - point of a second leg through a bidirectional switch tube. And the switching state of the upper - leg switch tube of the first leg bridged by the same bidirectional switch tube is the same as the switching state of the upper - leg switch tube of the second leg it bridges, and the switching state of the lower - leg switch tube of the first leg bridged by the same bidirectional switch tube is the same as the switching state of the lower - leg switch tube of the second leg it bridges; Injecting a diagnostic pulse into the p - phase armature winding includes: When a faulty switch pair is located within the conduction sector of the non-faulty switch pair connected to the p-phase armature winding, and according to the fault detection position θ0, it is determined that the remaining conduction width of the non-faulty switch pair within the current conduction sector does not meet the diagnostic pulse width requirement, a current path is constructed using the switches in the faulty switch pair of the p-phase armature winding and the bidirectional switch connected to the p-phase armature winding, and a diagnostic pulse is injected into the p-phase armature winding through the main power supply injection method.
6. The switch tube fault diagnosis method according to any one of claims 2-4, characterized in that, Injecting a diagnostic pulse into the p-phase armature winding through the back electromotive force self-injection method includes: The two switching tubes in the faulty switching tube pair that controls the connection of the p-phase armature winding are sequentially turned on individually. When the response current of the p-phase armature winding during the individual turn-on process reaches the threshold i th it is determined that the turned-off switching tube in the faulty switching tube pair has an open-circuit fault and the turned-on switching tube is operating normally; When the response currents of the p-phase armature winding during the single-tube conduction process do not reach the threshold i th , it is determined that both switching tubes in the faulty switching tube pair have open-circuit faults.
7. The switch tube fault diagnosis method according to claim 5, wherein Injecting a diagnostic pulse into the p-phase armature winding through the main power supply injection method includes: The two switching transistors in the faulty switching transistor pair controlling the connection of the p-phase armature winding are sequentially turned on individually. When one of the switching transistors in the faulty switching transistor pair is turned on, the bidirectional switching transistor connected to the armature of the other switching transistor is turned on, while the other two bidirectional switching transistors are kept off, forming a current path between the main power supply, the conducting switching transistor in the faulty switching transistor pair, the p-phase armature winding, the conducting bidirectional switching transistor, and the switching transistor in the main power converter with the same switching state as the non-conducting switching transistor in the faulty switching transistor pair, and injecting a diagnostic pulse. When the response current of the p-phase armature winding during the individual turn-on process reaches the threshold i th , it is determined that the non-conducting switching transistor in the faulty switching transistor pair has an open-circuit fault and the conducting switching transistor is operating normally; When the response currents of the p-phase armature winding during the single-tube conduction process do not reach the threshold current i th it is determined that both of the switching tubes in the faulty switching tube pair have open-circuit faults.
8. The switching tube fault diagnosis method according to claim 1, wherein Taking the direction from the midpoint of the first arm to the midpoint of the second arm of the p-phase armature winding connection as the positive current direction, the faulty switch tube pair connected to the p-phase armature winding is located according to the positive or negative value of the per-unit average value D of the phase current p as follows: When the per-unit average value D of the phase current p is within the error range of -1, it is determined that the switching transistor pair formed by the upper switching transistor of the first bridge arm and the lower switching transistor of the second bridge arm connected to the p-phase armature winding belongs to the faulty switching transistor pair; When the per-unit average value D of the phase current p is within the error range of 1, it is determined that the switching transistor pair formed by the lower switching transistor of the first bridge arm and the upper switching transistor of the second bridge arm connected to the p-phase armature winding belongs to the faulty switching transistor pair.
9. The switch tube fault diagnosis method according to any one of claims 3-5, characterized in that, Detecting whether the remaining conduction width of the non-faulty switch pair within the current conduction sector meets the diagnostic pulse width requirement includes: When it is detected that the fault detection position θ0 is not less than the diagnostic pulse injection width θ2 of the back electromotive force self-injection method from the end position of the current conduction sector of the non-faulty switch pair connected to the p-phase armature winding, it is determined that the remaining conduction width of the non-faulty switch pair within the current conduction sector meets the diagnostic pulse width requirement; otherwise, it is determined that the remaining conduction width of the non-faulty switch pair within the current conduction sector does not meet the diagnostic pulse width requirement.
10. The switch tube fault diagnosis method according to claim 9, characterized in that, According to the characteristics of instantaneously injecting a diagnostic pulse by the main power supply injection method, the diagnostic pulse injection width θ4 of the main power supply injection method is less than the diagnostic pulse injection width θ2 of the back electromotive force self-injection method. When the remaining conduction width of the non-faulty switch pair within the current conduction sector is less than the diagnostic pulse injection width θ2 of the back electromotive force self-injection method, a current path is constructed using the switches in the faulty switch pair of the p-phase armature winding and the bidirectional switch connected to the p-phase armature winding, and a diagnostic pulse is injected into the p-phase armature winding through the main power supply injection method.