Motor driving MOS fault diagnosis method

Abstract

The invention provides a motor driving MOS fault diagnosis method comprising the following steps: setting a three-phase duty ratio to be 0%, waiting for a first preset time, and detecting each phase current; if the absolute value of the current of any phase is greater than a first threshold value, judging that the upper bridge arm MOS corresponding to the corresponding phase is abnormally conducted; the three-phase duty ratio is set to be 100%, and after waiting for a second preset time, the current of each phase is detected; if the absolute value of the current of any phase exceeds a second threshold value, the lower bridge arm MOS corresponding to the corresponding phase is judged to be abnormally conducted; sequentially executing the following operations on the three phases: setting the current phase as a first phase and the other two phases as a second phase and a third phase respectively: setting the duty ratio of the first phase as a first duty ratio, and setting the duty ratios of the second phase and the third phase as 0%; after waiting for a third preset time, respectively detecting the current of the first phase, the second phase and the third phase; and if the absolute value of the current of any phase is smaller than a third threshold value, judging that the MOS has a fault. According to the method, the resource consumption of MOS fault diagnosis can be effectively reduced, and the diagnosis precision is improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of vehicle fault diagnosis, and in particular, to a motor drive MOS fault diagnosis method. BACKGROUND

[0002] As the core power switching device in the motor drive system, the reliability of MOS directly determines the safety and stability of system operation. During the operation of the motor, MOS may have abnormal conduction or open circuit failure due to overvoltage, overcurrent, temperature shock, etc. Lightly, it may cause torque fluctuation and efficiency decline, and heavily, it may cause system short circuit and even equipment damage. Especially in the application scenario of electric vehicles, real-time and accurate MOS fault detection has become a core technical requirement to ensure system functional safety.

[0003] Chinese patent CN116699391A discloses a brushless DC motor MOS fault detection method based on phase current analysis. The scheme collects the phase current and rotor phase, calculates the maximum phase current and compares it with the real-time current, and combines the speed and voltage parameters to perform fault diagnosis under normal operation and locked-rotor conditions. The core is to establish a correlation model between the phase current and the MOS state, and to determine the fault phase and the corresponding MOS through multi-parameter fusion. Although this method improves the detection coverage to some extent, it relies on real-time sampling of phase current and complex calculation, and needs to continuously occupy the MCU operation resources, especially in high-speed dynamic conditions, which is prone to diagnostic delay. More importantly, this scheme can only locate the upper and lower bridge arm MOS pairs of the fault phase, and cannot accurately distinguish whether the upper or lower bridge arm device fails, and cannot predict potential conduction abnormalities of MOS before the motor starts, leaving a diagnostic blind area.

[0004] The above defects expose the contradiction between the traditional scheme in real-time, diagnostic accuracy and implementation cost: the method based on real-time current sampling can capture dynamic fault characteristics, but the calculation load is large and it relies on high-precision sensors, which is difficult to deploy in low-cost controllers; and the fuzzy fault location leads to low maintenance efficiency, which cannot meet the stringent requirements of high-reliability systems for fault isolation. Especially in the context of permanent magnet synchronous motor and other strict driving timing requirements, the existing technology cannot quickly complete the MOS health state screening at the initial power-on stage of the system, which increases the risk of fault incubation. How to achieve fast and accurate MOS tube multi-dimensional fault diagnosis without increasing hardware cost has become a bottleneck problem restricting the development of motor drive technology. SUMMARY

[0005] The first aspect of the present application provides a motor drive MOS fault diagnosis method, comprising:

[0006] Setting the U, V, W three-phase PWM duty ratio to 0%, waiting for a first preset time, detecting the current of each phase; if the absolute value of any one phase current is greater than the first threshold value, it is determined that the corresponding upper bridge arm MOS of the corresponding phase is abnormally turned on;

[0007] Setting the U, V, W three-phase PWM duty ratio to 100%, waiting for a second preset time, detecting the current of each phase; if the absolute value of any one phase current exceeds the second threshold value, it is determined that the corresponding lower bridge arm MOS of the corresponding phase is abnormally turned on;

[0008] In turn, the following operations are performed on the U, V, W three-phase, the current phase is set as the first phase, and the remaining two phases are set as the second phase and the third phase, and the specific steps are as follows:

[0009] The PWM duty ratio of the first phase is set to the first duty ratio, and the PWM duty ratio of the second phase and the third phase is set to 0%;

[0010] After waiting for a third preset time, the currents of the first phase, the second phase and the third phase are detected respectively;

[0011] If the absolute value of the current of any one phase is less than the third threshold value, it is determined that the MOS is faulty.

[0012] Optionally, if the absolute value of the current of any one phase is less than the third threshold value, the MOS fault determining step further comprises:

[0013] If only the absolute value of the current of the first phase is less than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the first phase is abnormally turned off;

[0014] If the absolute value of the current of the second phase is less than the third threshold value, and the absolute value of the current of the third phase is greater than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the second phase is abnormally turned off;

[0015] If the absolute value of the current of the third phase is less than the third threshold value, and the absolute value of the current of the second phase is greater than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the third phase is abnormally turned off;

[0016] If the absolute values of the currents of the second phase and the third phase are both less than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the second phase and the third phase is abnormally turned off or the upper bridge arm MOS corresponding to the first phase is abnormally turned off.

[0017] Optionally, the method further comprises the following steps:

[0018] Before detection, if no MOS diagnostic fault is recorded at present, the subsequent steps are continued to be executed.

[0019] Optionally, the method further comprises the following steps:

[0020] Before detection, if the current is not a MOS diagnostic incomplete state, continue to execute the subsequent steps.

[0021] Optionally, the first duty cycle is a 3% duty cycle.

[0022] Optionally, the first threshold value, the second threshold value, and the third threshold value are tunable values, and are set to 5A by default.

[0023] Optionally, the time value of the first preset time, the second preset time, and the third preset time is set in a range greater than or equal to 1ms and less than or equal to 20ms.

[0024] Optionally, the time value of the first preset time, the second preset time, and the third preset time is 10ms.

[0025] The second aspect of the present application provides a permanent magnet synchronous motor, which applies any method in the first aspect to diagnose MOS failure.

[0026] The third aspect of the present application provides a vehicle comprising the permanent magnet synchronous motor in the second aspect.

[0027] The present application forcibly sets the PWM duty cycle to 0% (full lower bridge arm off) or 100% (full upper bridge arm on), uses the uniqueness of the current path to achieve fault isolation, thereby directly locking the abnormal conduction MOS, solves the industry problem of "unable to distinguish upper and lower bridge arm failure" in traditional methods, and improves the problem diagnosis accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background art, the drawings needed to be used in the embodiments of the present application or the background art will be described below. Obviously, the drawings described below are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0029] Figure 1 A motor MOS circuit schematic diagram in the embodiments of the present application is shown;

[0030] Figure 2 A flowchart of a motor drive MOS fault diagnosis method in the embodiments of the present application is shown;

[0031] Figure 3 A method flowchart of specific steps for determining MOS failure if the absolute value of the current of any phase is less than the third threshold value in the embodiments of the present application is shown. DETAILED DESCRIPTION

[0032] In the description of the embodiments of the application, those skilled in the art should understand that the embodiments of the application can be implemented as a method, a permanent magnet synchronous motor and a vehicle.

[0033] The embodiments of the application provide the method by means of flow charts and / or block diagrams. It should be understood that each block of the flow chart and / or block diagram and combinations thereof can be implemented by computer readable program instructions. The computer readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate means for implementing the functions / acts specified in the flow chart and / or block diagram block or blocks.

[0034] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer or other programmable data processing apparatus provide processes for implementing the functions / acts specified in the flow chart and / or block diagram block or blocks.

[0035] The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus or other device to produce a computer implemented process such that the instructions which execute on the computer or other programmable data processing apparatus provide processes for implementing the functions / acts specified in the flow chart and / or block diagram block or blocks.

[0036] Figure 1 A motor MOS circuit schematic diagram in the embodiments of the application is shown, as shown in the figure, the core of the motor drive system is a three-phase full-bridge inverter circuit, and the Mos tube topological structure comprises: each phase (U / V / W) is composed of a pair of complementary MOS to form upper and lower bridge arms (Q1-Q2, Q3-Q4, Q5-Q6), the source electrode of the upper bridge arm MOS (Q1 / Q3 / Q5) is connected with the positive electrode (Vdc+) of the direct current bus, and the drain electrode of the lower bridge arm MOS (Q2 / Q4 / Q6) is connected with the negative electrode (GND) of the direct current bus. When the upper bridge arm MOS of a certain phase is turned on (PWM duty ratio > 0%), the current flows from Vdc+ to the motor winding through the Mos, forming a forward current; when the lower bridge arm MOS of a certain phase is turned on (complementary PWM signal), the current flows from the motor winding to GND through the MOS, forming a freewheeling path.

[0037] Figure 2 A flow chart of a motor drive MOS fault diagnosis method in the embodiments of the application is shown, and the method comprises at least the following steps:

[0038] Setting the U, V, W three-phase PWM duty ratio to 0%, waiting for a first preset time, detecting the current of each phase; if the absolute value of any one phase current is greater than the first threshold value, it is determined that the corresponding upper bridge arm MOS of the corresponding phase is abnormally turned on;

[0039] Setting the U, V, W three-phase PWM duty ratio to 100%, waiting for a second preset time, detecting the current of each phase; if the absolute value of any one phase current exceeds the second threshold value, it is determined that the corresponding lower bridge arm MOS of the corresponding phase is abnormally turned on;

[0040] The following operations are sequentially performed on the U, V, W three phases, setting the current phase as the first phase, and the remaining two phases as the second phase and the third phase, and the specific steps are as follows:

[0041] Setting the PWM duty ratio of the first phase to the first duty ratio, and setting the PWM duty ratio of the second phase and the third phase to 0%;

[0042] After waiting for a third preset time, the currents of the first phase, the second phase and the third phase are detected respectively;

[0043] If the absolute value of the current of any phase is less than the third threshold value, it is determined that the MOS is faulty.

[0044] In combination Figure 1 With Figure 2 , it can be concluded that when the three-phase PWM duty ratio is all set to 0%, the gate drive signal of all lower bridge arm MOS (Q2 / Q4 / Q6) is forced to be closed (low level), at this time the ideal state of each phase current should be zero. If the current absolute value of a certain phase (for example, U phase) is detected to exceed the first threshold value, its current path must be: Vdc+→ abnormally turned on upper bridge arm Q1→ U phase winding→ other turned on lower bridge arm (at least one of Q2 / Q4 / Q6)→ GND. Because when PWM=0%, the lower bridge arm MOS should be completely turned off, only the upper bridge arm may be turned on due to breakdown or abnormal driving; as shown in Figure 1 , the upper and lower bridge arm current paths are physically isolated through the DC bus (Vdc+ / GND), avoiding cross interference.

[0045] The purpose of setting the U, V, W three-phase PWM duty ratio to 0% is to quickly lock the abnormal conduction of the upper bridge arm MOS (such as Q1 breakdown short circuit) before the motor starts or during the intermittent period, avoiding the omission of latent faults due to the dependence on dynamic current model in the traditional method; at the same time, the current sensor (Hall element or sampling resistor) pre-set at the U / V / W output end can be reused, without the need for additional hardware.

[0046] The detection step can directly use the existing three-phase current detection module, the detection cost is effectively reduced, and the first preset time covers the MOS turn-off delay and the parasitic capacitor discharge period, ensuring the detection stability, effectively reducing the false positive rate, and the first preset threshold is a dynamically adapted threshold, which can adapt to different power levels, avoiding misjudgment caused by load fluctuations.

[0047] When the three-phase PWM duty cycle is set to 100%, all upper bridge arm MOS (Q1 / Q3 / Q5) is continuously turned on, and the lower bridge arm MOS should be completely turned off. If the current absolute value of a phase (for example, the V phase) is detected to exceed the second threshold, the current path is: the turned-on upper bridge arm Q3→the V phase winding→the abnormally turned-on lower bridge arm Q4→GND. At this time, the upper bridge arm is forced to be turned on when PWM=100%, and if the lower bridge arm is abnormally turned on, a low-resistance loop is formed; when the lower bridge arm is abnormally turned on, the current direction is opposite to that of normal freewheeling (from the winding to GND), which can be judged through the current polarity.

[0048] The purpose of setting the U, V, and W three-phase PWM duty cycles to 100% is to accurately identify the short circuit fault (such as Q4 gate breakdown) of the lower bridge arm MOS, solve the positioning ambiguity problem caused by bridge arm cross interference in the traditional method, and cover the blind area of the traditional dynamic detection. The detection is performed after the second preset time, which can ensure that the bridge arm is completely turned on and avoid switch transient noise interference.

[0049] Then the U, V, and W three-phase are detected in turn, the current phase is set as the first phase, the other two phases are set as the second phase and the third phase in clockwise direction, and the PWM duty cycle of the first phase is set as the first duty cycle, and the PWM duty cycles of the other two phases are set as 0. Based on the above settings, in the case of no fault, the current path should be: Vdc+→the first phase upper bridge arm (turned on)→the first phase winding→the first phase lower bridge arm (turned off)→the current needs to pass through the other turned-on lower bridge arm (such as the lower bridge arm of the second phase or the third phase)→GND. If the second phase current is less than the third preset threshold, it indicates that the second phase lower bridge arm is not turned on, causing the current to fail to pass through the second phase lower bridge arm freewheeling (path: first phase→second phase lower bridge arm should be turned on but actually not turned on), that is, an open circuit fault is diagnosed. If the third phase current is greater than the third preset threshold, it indicates that the third phase upper bridge arm is abnormally turned on, forming a first phase→third phase interphase short circuit current, that is, a short circuit fault is diagnosed.

[0050] Synchronous detection of open circuit and short circuit faults can effectively cover the MOS full failure mode and realize cross-phase verification, utilize the three-phase current correlation (such as the U phase activation, the V / W phase current should pass through the complementary bridge arm to form a loop), and improve the diagnosis reliability.

[0051] The method can effectively improve fault identification accuracy by forcibly forming a specific current path through single-phase activation, and can adjust the value of the first duty cycle to adapt to different working conditions of different rotating speeds. The method only needs to detect the absolute value of three-phase current without complex FFT or model calculation, effectively reducing the occupation of MCU resources.

[0052] Figure 3 If the absolute value of the current of any one phase in the application embodiment is less than the third threshold value, the specific steps of the method for determining the MOS fault are shown in the flow chart, which includes the following steps:

[0053] If only the absolute value of the current of the first phase is less than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the first phase is abnormally open;

[0054] If the absolute value of the current of the second phase is less than the third threshold value, and the absolute value of the current of the third phase is greater than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the second phase is abnormally open;

[0055] If the absolute value of the current of the third phase is less than the third threshold value, and the absolute value of the current of the second phase is greater than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the third phase is abnormally open;

[0056] If the absolute values of the currents of the second phase and the third phase are both less than the third threshold value, it is determined that the lower bridge arm MOS corresponding to the second phase and the third phase are both abnormally open or the upper bridge arm MOS corresponding to the first phase is abnormally open.

[0057] First, the current of the first phase is detected. Under normal circumstances, the conduction path is: Vdc+ → the first phase upper bridge arm (conducting) → the first phase winding → the other conducting lower bridge arm (the second phase or the third phase lower bridge arm) → GND. If the absolute value of the current of the first phase is detected to be less than the third threshold value, it indicates that the first phase current loop is blocked, and at this time the first phase lower bridge arm is not normally conducting, resulting in that the current cannot form a freewheeling path through the first phase lower bridge arm (even if the other lower bridge arm is conducting, but because the current flows through the first phase lower bridge arm when the first phase is activated). The first phase lower bridge arm is directly connected to GND, and if the first phase lower bridge arm is open, even if the second phase or the third phase lower bridge arm is conducting, the first phase current cannot form an effective loop through the remote lower bridge arm (because the three-phase winding is connected in star / triangle, the impedance of the remote path is much higher than that of the local path).

[0058] By forcibly making the current flow through the local lower bridge arm through single-phase activation, the traditional method can effectively avoid misjudgment caused by multi-phase current coupling. It can use the electrical isolation characteristics of the three-phase winding to exclude the interference of the remote bridge arm and ensure that only the state of the local lower bridge arm affects the detection result.

[0059] After detecting the second phase current, under normal circumstances, the current path is: the first phase current passes through the first phase upper arm → the first phase winding → the second phase or third phase lower arm → GND, at this time the second phase or third phase lower arm should provide a freewheeling path. If the absolute value of the second phase current is less than the third threshold value, and the absolute value of the third phase current is greater than the third threshold value, it indicates that the second phase lower arm is open, causing the second phase to be unable to conduct, and the current is forced to pass through the third phase lower arm, forming a loop. At this time, because the third phase loop impedance is low (only the third phase lower arm needs to be passed through), its current is significantly higher than that of the second phase. The three-phase winding is interconnected to form an electrical network, when the second phase lower arm is open, the second phase freewheeling path is cut off, and the first phase current is forced to detour to the third phase lower arm, causing the third phase current to surge.

[0060] By single detection, the status of the first phase lower arm and the second phase or third phase remote lower arm can be judged synchronously, realizing synchronous detection of multiple faults. When the second phase lower arm is open, the third phase current is significantly higher than the normal value of the reachable current due to the reduced path impedance, which can significantly improve the recognition of fault features.

[0061] After detecting the third phase current, under normal circumstances, the current path is: the first phase current passes through the first phase upper arm → the first phase winding → the third phase lower arm → GND, and the third phase lower arm should normally conduct. If the absolute value of the third phase current is less than the third threshold value, and the absolute value of the second phase current is greater than the third threshold value, it indicates that the third phase lower arm is open, and the first phase current is forced to flow through the second phase lower arm, causing the second phase current to rise. When the third phase lower arm is open, the first phase current needs to detour to the second phase lower arm, causing the second phase current path impedance to decrease, and the current value to rise significantly (because the second phase winding forms a parallel path with the first phase).

[0062] By polling activating each phase, full bridge arm detection can be covered, ensuring that all lower arms are independently verified, and the verification current path can be dynamically switched with different lower arm states. Through full bridge arm fault coverage, the detection range is expanded to all three lower arms, effectively improving fault detection rate, and the fault determination response time is extremely short, which can meet the needs of high dynamic conditions.

[0063] If the absolute values of the currents of the second phase and the third phase are both less than the third threshold value, there are two possibilities, respectively: first, the lower bridge arms of the two phases are open, such as the second phase lower bridge arm and the third phase lower bridge arm are both open, the first phase current cannot form a loop through the second phase or the third phase lower bridge arm, resulting in that the second phase or the third phase current tends to zero; second, the first phase upper bridge arm is open, the first phase upper bridge arm is not conductive, the first phase current cannot be established, indirectly resulting in that the second phase or the third phase phase current is missing. When the first phase upper bridge arm is open, the first phase cannot form an effective driving voltage, and the three-phase winding has no current; when the second phase and the third phase lower bridge arms are simultaneously open, only the first phase lower bridge arm can be used for freewheeling, but the first phase lower bridge arm should be turned off in the non-activated state, resulting in that the loop is completely interrupted.

[0064] The present application deeply combines the topological characteristics of the three-phase inverter shown in the drawings, realizes high-precision positioning of the lower bridge arm MOS open circuit fault through the current path uniqueness design and the dynamic polling activation mechanism, and simultaneously verifies the upper bridge arm fault in a cross manner. The system reliability is effectively improved compared with the traditional scheme, and an optimal detection scheme is provided for a high-reliability motor drive system.

[0065] In some embodiments, optionally, the method further includes the following steps: before detection, if no MOS diagnostic fault is currently recorded, the subsequent steps are continued. Before entering the MOS diagnostic process, the control unit performs the following determination logic: whether there is an unremoved MOS fault record is checked. If there is a fault record, it indicates that the relevant detection has been performed before and the fault prompt has been obtained, and has not been solved. Therefore, in this case, the detection program is directly exited, and the specific reason for interrupting the detection is prompted. By judging whether there is an existing detection fault state, redundant fault detection can be effectively avoided, the intelligence of the system is improved, and the waste of system operation resources is reduced.

[0066] In some embodiments, optionally, the method further includes the following steps: before detection, if the current is a non-MOS diagnostic incomplete state, the subsequent steps are continued. Before the detection process starts, a global detection state identifier is set in the memory or the configuration file. When the detection process is normally started, the detection state identifier is changed to detection in progress. The detection state identifier can include: undetected, detection in progress, detection completed, etc. Before detection, the detection state identifier is determined. If the state is detection in progress, it indicates that the system is currently performing MOS diagnosis, the detection program is directly exited, and the specific reason is informed to the user. By judging whether there is an incomplete detection process, system resources can also be wasted, and the system operation efficiency is improved.

[0067] In some embodiments, optionally, the first duty cycle is 3% duty cycle. The precondition for starting the fault detection is to activate the current path under the condition of avoiding the rotation of the motor, and setting the duty cycle to 3% can generate a minimum effective voltage sufficient to drive the detection, while ensuring that the motor back electromotive force is much larger than the driving voltage, thereby inhibiting the rotation of the rotor. Setting the duty cycle to 3% can fully meet the requirement that the detection process does not interfere with the operating state of the motor, and setting too small will greatly affect the detection result, and setting too large will affect the operating state of the motor to some extent; at the same time, a small amplitude of the duty cycle setting can also reduce the energy consumption in the detection process to some extent, and optimize the energy utilization rate.

[0068] In some embodiments, optionally, the first threshold, the second threshold and the third threshold are calibratable values, and are set to 5A by default. It should be understood that the values of the first threshold, the second threshold and the third threshold in the present application can be the same or different, and can be adjusted according to specific conditions. The above-mentioned threshold needs to cover the detection requirements of the rated current of medium and small power motors, therefore, setting the threshold to 5A can effectively distinguish the noise current from the real fault current, and the noise current is generally less than or equal to 2A, while the fault current is generally greater than or equal to 8A. The above-mentioned threshold can be intelligently adapted according to the specific model of the motor and the vehicle, without the need for users to perform initialization work individually, thereby improving the intelligence level of the detection process, and the setting range of the threshold is less than the maximum short-circuit current allowed by the MOS, which meets the industry safety specifications.

[0069] In some embodiments, optionally, the time value of the first preset time, the second preset time and the third preset time is set to be greater than or equal to 1ms and less than or equal to 20ms, preferably 10ms. It should be understood that the values of the above-mentioned first preset time, the second preset time and the third preset time can be the same or different, and can be set according to specific conditions. The above-mentioned preset time is set to be between 1ms and 20ms, because: when exceeding 1ms, in order to ensure that the current is stable before the related current detection is performed, the error influence of the current initialization on the detection result is effectively reduced; the purpose of being less than 20ms is to reduce the detection error caused by the overheating of the winding. It has been proved through many experimental data that 10ms is the preferred balance point, which can effectively reduce the detection error while ensuring the detection speed, thereby improving the accuracy of the detection.

[0070] Embodiment 1, the present embodiment is a motor driving MOS fault diagnosis method implementation process, which is specifically as follows:

[0071] Step 1: System pre-detection and state determination

[0072] Access the NVM memory of the master chip, check the fault flag register, if there is a non-zero fault code (such as 0x01 indicating Q1 abnormality), trigger the LED alarm (red flashing) and terminate the process; if the diagnosis progress register ≠ 0x00 (0x00 indicates idle), resume the detection stage before the interruption; only when there is no fault record and the state is idle, enter step 2.

[0073] Step 2: Static off detection of upper bridge arm

[0074] Configure the three-phase PWM generator, set U / V / W duty ratio = 0%, dead time = 1 μs (to prevent shoot-through); start the first preset time timer (default 10 ms), wait for the end of the timing, synchronously sample the three-phase current through the ADC module, if the absolute value of any phase current > 5A, determine that the corresponding upper bridge arm MOS is abnormally conducting, and write the corresponding fault code into the NVM memory.

[0075] Step 3: Static conduction detection of lower bridge arm

[0076] Reconfigure the PWM generator, set U / V / W duty ratio = 100%, dead time remains 1 μs, start the second preset time timer (10 ms), sample the three-phase current after the timing ends, if the absolute value of any phase current > 5A, determine that the corresponding lower bridge arm MOS is abnormally conducting, and write the corresponding fault code into the NVM memory.

[0077] Step 4: Dynamic cross verification (take U phase as an example)

[0078] First activate the U phase, set U phase PWM duty ratio = 3%, V / W phase duty ratio = 0%, and wait for 10 ms, sample the three-phase current I_U, I_V, I_W, and perform hierarchical diagnosis.

[0079] When I_U is less than 5A and both I_V and I_W are greater than 5A, it is determined that the U phase lower bridge arm is open circuit;

[0080] When I_V is less than 5A and I_W is greater than 5A, it is determined that the V phase lower bridge arm is open circuit;

[0081] When I_W is less than 5A and I_V is greater than 5A, it is determined that the W phase lower bridge arm is open circuit;

[0082] When I_V is less than 5A and I_W is less than 5A, it is determined that the V and W phase lower bridge arms are open circuit or the U phase upper bridge arm is open circuit.

[0083] Repeat the above steps in step 4, set the active phase to V phase and W phase respectively, and complete the full-phase detection.

[0084] Step 5: result output and system protection

[0085] The three detection results are integrated to generate a fault report. If a fault is detected, the PWM output is immediately blocked, hardware protection is triggered, a diagnostic code is sent through the CAN bus, and the user is promptly notified.

Claims

1. A method for diagnosing faults in a motor-driven MOS, characterized in that, Includes the following steps: Set the duty cycle of the three-phase PWM of U, V, and W to 0%, wait for the first preset time, and then detect the current of each phase. If the absolute value of the current of any phase is greater than the first threshold, it is determined that the upper bridge arm MOS of the corresponding phase is abnormally turned on. Set the duty cycle of the three-phase PWM of U, V, and W to 100%, wait for the second preset time, and then detect the current of each phase. If the absolute value of the current of any phase exceeds the second threshold, it is determined that the lower bridge arm MOS of the corresponding phase is abnormally turned on. Perform the following operations sequentially on phases U, V, and W, setting the current phase as phase one and the remaining two phases as phase two and phase three, respectively: The PWM duty cycle of the first phase is set to the first duty cycle, and the PWM duty cycles of the second and third phases are set to 0%. After waiting for the third preset time, the currents of the first phase, the second phase, and the third phase are detected respectively; If the absolute value of the current in any phase is less than the third threshold, then the MOS is determined to be faulty.

2. The method according to claim 1, characterized in that, The step of determining a MOS fault if the absolute value of the current in any phase is less than the third threshold further includes: If the absolute value of the current in only the first phase is less than the third threshold, then the lower bridge arm MOS corresponding to the first phase is determined to be abnormally open-circuited. If the absolute value of the current in the second phase is less than the third threshold, and the absolute value of the current in the third phase is greater than the third threshold, then the lower bridge arm MOS corresponding to the second phase is determined to be abnormally open-circuited. If the absolute value of the current in the third phase is less than the third threshold, and the absolute value of the current in the second phase is greater than the third threshold, then the lower bridge arm MOS corresponding to the third phase is determined to be abnormally open-circuited. If the absolute values ​​of the currents in the second phase and the third phase are both less than the third threshold, then it is determined that the lower bridge arm MOS corresponding to the second phase and the third phase are abnormally open-circuited or the upper bridge arm MOS corresponding to the first phase is abnormally open-circuited.

3. The method according to claim 1 or 2, characterized in that, The method further includes the following steps: Before testing, if no MOS diagnostic faults are currently recorded, proceed with the next steps.

4. The method according to claim 3, characterized in that, The method further includes the following steps: Before testing, if the current state is that the non-MOS diagnosis is incomplete, then proceed with the subsequent steps.

5. The method according to claim 1, characterized in that, The first duty cycle is a 3% duty cycle.

6. The method according to claim 5, characterized in that, The first threshold, the second threshold, and the third threshold are calibrable values.

7. The method according to claim 6, characterized in that, The time values ​​of the first preset time, the second preset time, and the third preset time are set within a range of greater than or equal to 1ms and less than or equal to 20ms.

8. The method according to claim 7, characterized in that, The first preset time, the second preset time, and the third preset time are all 10ms.

9. A permanent magnet synchronous motor, characterized in that, The method described in any one of claims 1-8 is used to diagnose MOS faults.

10. A vehicle, characterized in that, Includes the permanent magnet synchronous motor as described in claim 9.

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