A brushless direct current motor open-circuit fault diagnosis method based on phase current detection

Abstract

The application discloses a brushless direct current motor open-circuit fault diagnosis method based on phase current detection, including single-tube open-circuit fault and double-tube open-circuit fault (fault switch tube is in upper bridge arm and lower bridge wall). Firstly, three-phase current values and rotor position angle of the brushless direct current motor are sampled, then, according to the rotor position angle of the brushless direct current motor, the sum of the absolute values of the phase currents of two conducting phases of the brushless direct current motor is calculated, then compared with the absolute value of the phase current of another phase to obtain a fault flag signal, finally, according to the state of the fault flag signal, whether the inverter has an open-circuit fault is judged, and the position information of the fault switch tube is obtained. The method realizes online diagnosis of the open-circuit fault of the inverter of the brushless direct current motor, so that corresponding measures can be taken in time when the open-circuit fault of the inverter occurs, and the loss of the brushless direct current motor system caused by the open-circuit fault of the inverter is reduced.

Description

Technical Field

[0001] This invention relates to a method for diagnosing open-circuit faults in brushless DC motors based on phase current detection, belonging to the field of motor drives and converters. Background Technology

[0002] Brushless DC motors use electronic commutation instead of the brushes and commutator of traditional brushed motors. They have advantages such as simple structure, excellent speed regulation performance, and high power density, making them widely used in household appliances (such as refrigerator compressors and washing machines), commercial, industrial, electric vehicles, aerospace and other fields.

[0003] Due to the fragility of power electronic devices and the complexity of their control, inverters are the most vulnerable link in the entire brushless DC motor control system. To improve system reliability, fault-tolerant control is commonly applied to inverters. Real-time and effective fault detection, location, and isolation are prerequisites for implementing fault-tolerant control. Therefore, researching inverter fault diagnosis methods has significant practical value. Common inverter faults mainly include open-circuit and short-circuit faults. Short-circuit faults are typically handled by hardware circuitry within microseconds; for open-circuit faults, while they usually do not immediately cause system shutdown, they can trigger secondary faults in other components, ultimately leading to system malfunction. Therefore, diagnosing and locating open-circuit faults in inverters lays the foundation for subsequent fault isolation, removal, and even system fault-tolerant control.

[0004] Currently, methods for diagnosing open-circuit faults can be divided into current or voltage detection methods. However, most of these methods require the addition of a large amount of hardware circuitry or the use of complex signal extraction circuits and processing algorithms, resulting in limited practical application value. Summary of the Invention

[0005] Technical Problem: Addressing the shortcomings of existing methods for diagnosing open-circuit faults in brushless DC motors, this paper proposes a new method based on phase current detection for diagnosing open-circuit faults in brushless DC motors, including single-transistor open-circuit faults and double-transistor open-circuit faults (with faulty switching transistors located in the upper and lower bridge arms). First, the three-phase current values ​​and rotor position angle of the brushless DC motor are sampled. Then, based on the rotor position angle, the sum of the absolute values ​​of the phase currents of the two conducting phases is calculated. This sum is then compared with the absolute value of the phase current of the other phase to obtain a fault flag signal. Finally, based on the status of the fault flag signal, it is determined whether an open-circuit fault has occurred in the inverter, and the location information of the faulty switching transistor is obtained. This method enables online diagnosis of open-circuit faults in brushless DC motor inverters, facilitating timely responses when open-circuit faults occur, thereby reducing losses caused by open-circuit faults in the brushless DC motor system. This method does not require extensive hardware circuitry or complex signal extraction circuits, and the signal processing algorithm is simple, enabling rapid detection of single-transistor and double-transistor open-circuit faults in the inverter.

[0006] Technical solution: A method for diagnosing open-circuit faults in brushless DC motors based on phase current detection, comprising the following steps:

[0007] Step 1: In each control cycle, sample the Hall sensor signal H of the brushless DC motor. A H B and H C The working interval signal S is calculated using the working interval determiner. n (n = 1 to 6);

[0008] Step 2: Sample the three-phase current values ​​of the brushless DC motor. Use the fault detector to calculate the sum of the absolute values ​​of the phase currents of the two conducting phases, i1, and the absolute value of the phase current of the other phase, i2. Compare i1 and i2 to obtain the fault flag signal F. n (n = 1 to 6);

[0009] Step 3: Based on the fault indicator signal F n The fault location detector determines the location of the inverter switching transistor fault.

[0010] Step 4: Output inverter open circuit fault information through the diagnostic result output unit;

[0011] Furthermore, the brushless DC motor operating range signal S n The acquisition method is as follows: acquire the motor position signal H through a Hall sensor. A H B and H C (Or the motor rotor position angle θ), the motor operating range signal S is obtained according to formula (1). n(Or obtain the motor operating range signal S according to formula (2)) n ).

[0012]

[0013]

[0014] In the formula This represents the inverse logic of H, when H = 0. When H = 1,

[0015] Furthermore, the fault flag signal F n The acquisition method is as follows: First, the three-phase current i is collected through a current sensor. A i B and i C Then, i1 is calculated using formula (3), i2 is calculated using formula (4), and finally, the fault flag signal F is calculated using formula (5). n .

[0016] i1=(S1+S2+S4+S5)*|i A |+(S1+S3+S4+S6)*|i B |+(S2+S3+S5+S6)*|i C | (3)

[0017]

[0018]

[0019] In the formula i 1_max This represents the maximum value of i1 within a 360-degree electrical angle of motor rotation. For every 360-degree electrical angle the motor rotates, i... 1_max Updated once; in the formula This represents the inverse logic of S, when S = 0. When S=1, The symbol "|" represents the OR operation.

[0020] Furthermore, the fault location method for the switching tube is as follows: (1) Single tube open circuit fault: If F1F2=1, T1 is open circuit fault; if F4F5=1, T2 is open circuit fault; if F3F4=1, T3 is open circuit fault; if F1F6=1, T4 is open circuit fault; if F5F6=1, T5 is open circuit fault; if F2F3=1, T6 is open circuit fault. (2) Double tube open circuit fault in the same bridge arm: If F1F2F4F5=1, T1 and T2 are open circuit faults; if F1F3F4F6=1, T3 and T4 are open circuit faults; if F2F3F5F6=1, T5 and T6 are open circuit faults. (3) Open circuit faults in the upper and lower arms of different bridge arms: If F1F2F6=1, T1 and T4 are open circuit faults; F1F2F3=1, T1 and T6 are open circuit faults; F3F4F5=1, T2 and T3 are open circuit faults; If F2F3F4=1, T3 and T6 are open circuit faults; F4F5F6=1, T2 and T5 are open circuit faults; F1F5F6=1, T4 and T5 are open circuit faults.

[0021] Beneficial effects: (1) The brushless DC motor open circuit fault diagnosis method based on phase current detection proposed in this invention is simple, fast and accurate. It can not only detect single tube open circuit of inverter, but also detect double tube open circuit fault of inverter, and can quickly locate the faulty switching tube.

[0022] (2) The method of the present invention does not require the addition of a large number of hardware circuits or the use of complex signal extraction circuits, and the signal processing algorithm is simple.

[0023] (3) The open circuit fault diagnosis section and the brushless DC motor control section are integrated together, which simplifies the communication mechanism between chips and enables the rapid output of diagnostic results, providing a foundation for realizing the system fault protection function. Attached Figure Description

[0024] Figure 1 This is a control block diagram for a brushless DC motor open-circuit fault diagnosis method based on phase current detection.

[0025] Figure 2 This is the current waveform corresponding to the normal operation of the inverter;

[0026] Figure 3 The current waveform corresponding to an open-circuit fault in T1;

[0027] Figure 4 The current waveform corresponding to an open-circuit fault in T2;

[0028] Figure 5 The corresponding current waveforms when T1 and T2 are open-circuit faults;

[0029] Figure 6The corresponding current waveforms when T1 and T4 are open-circuit faults. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0031] like Figure 1 As shown, the brushless DC motor system based on phase current detection consists of a brushless DC motor module 2, an inverter 1, and an electric drive system controller. The power input port of the inverter 1 is connected to the power supply, and the power output port of the inverter 1 is connected to the brushless DC motor module 2. The electric drive system controller is directly connected to the control port of the inverter 1. The electric drive system controller consists of a working range judgment module 3, a fault detection module 4, a fault location judgment module 5, and a diagnostic result output module 6. The working range judgment module 3 detects the position signal of the brushless DC motor module 2 through a Hall sensor. After processing, the working range judgment module 3 transmits the data to the fault detection module 4. The fault detection module 4 also detects the stator current signal of the brushless DC motor module 2 through a current sensor. After processing the received data, the fault detection module 4 sends it to the fault location judgment module 5 for judgment. After judgment, the fault location judgment module 5 outputs the working status of the inverter 1 through the diagnostic result output module 6.

[0032] The method for diagnosing open-circuit faults in brushless DC motors based on phase current detection includes the following steps:

[0033] Step 1: In each control cycle, sample the Hall sensor signal H of the brushless DC motor. A H B and H C The working interval signal S is calculated using the working interval determiner. n (n = 1 to 6); specifically:

[0034] The Hall sensor signal H A H B and H C (Or the motor rotor position angle θ) is input into the working range detector, and the motor working range signal S is obtained according to formula (1). n (Or obtain the motor operating range signal S according to formula (2)) n );;

[0035]

[0036]

[0037] In the formula This represents the inverse logic of H, when H = 0. When H = 1,

[0038] Step 2: Sample the three-phase current values ​​of the brushless DC motor. Use the fault detector to calculate the sum of the absolute values ​​of the phase currents of the two conducting phases, i1, and the absolute value of the phase current of the other phase, i2. Compare i1 and i2 to obtain the fault flag signal F. n (n = 1 to 6), specifically:

[0039] The three-phase current i of the brushless DC motor A i B and i C Input the fault detector, then calculate i1 using formula (3), calculate i2 using formula (4), and finally calculate the fault flag signal F using formula (5). n ;

[0040] i1=(S1+S2+S4+S5)*|i A |+(S1+S3+S4+S6)*|i B |+(S2+S3+S5+S6)*|i C | (3)

[0041]

[0042]

[0043] In the formula i 1_max This represents the maximum value of i1 within a 360-degree electrical angle of motor rotation. For every 360-degree electrical angle the motor rotates, i... 1_max Updated once; in the formula This represents the inverse logic of S, when S = 0. When S=1, The symbol "|" represents the OR operation.

[0044] Step 3: Based on the fault indicator signal F n The fault location detector determines the location of the inverter switching transistor fault, specifically:

[0045] Fault flag signal F nInput the fault location detector, and then locate the inverter switching transistors according to the following order: First, determine whether the two switching transistors in the same bridge arm have an open circuit fault: if F1F2F4F5=1, T1 and T2 have an open circuit fault; if F1F3F4F6=1, T3 and T4 have an open circuit fault; if F2F3F5F6=1, T5 and T6 have an open circuit fault. If two switches on the same bridge arm have an open circuit fault, the fault location detector exits, and the fault switch location ends; otherwise, it determines whether two switches on different bridge arms have an open circuit fault: if F1F2F6=1, T1 and T4 have an open circuit fault; if F1F2F3=1, T1 and T6 have an open circuit fault; if F3F4F5=1, T2 and T3 have an open circuit fault; if F2F3F4=1, T3 and T6 have an open circuit fault; if F4F5F6=1, T2 and T5 have an open circuit fault; if F1F5F6=1, T4 and T5 have an open circuit fault. If two switches on different bridge arms (upper and lower arms) experience open-circuit faults, the fault location detector exits, and the fault switch location ends. Otherwise, it checks for single-switch open-circuit faults: if F1F2=1, T1 is open-circuit faulted; if F4F5=1, T2 is open-circuit faulted; if F3F4=1, T3 is open-circuit faulted; if F1F6=1, T4 is open-circuit faulted; if F5F6=1, T5 is open-circuit faulted; if F2F3=1, T6 is open-circuit faulted. After the determination is completed, the fault location detector exits. Note that this step is performed once every 360 electrical degrees of motor rotation.

[0046] Step 4: Output the inverter open-circuit fault information through the diagnostic result output unit, specifically:

[0047] Write the inverter open-circuit fault information into the corresponding flag variable or display it on the screen or digital tube. Then F n Clear to zero, and for i 1_max Perform the update. Note that this step is performed once every 360 electrical degrees the motor rotates.

[0048] To verify the effectiveness of the method described in this invention in diagnosing and locating open-circuit faults in brushless DC motor inverters, simulations were performed on the method described in this invention. For example... Figure 2 The figure shows the current waveform corresponding to the normal operation of the brushless DC motor. From the i1 and i2 waveforms in the figure, we can obtain the current using formula (5): F n =0. Therefore, the inverter has not experienced an open-circuit fault. For example... Figure 3 The image shows the current waveform corresponding to an open-circuit fault in transistor T1. The fault detector outputs: F1 = 1, F2 = 1, F3 = 0, F4 = 0, F5 = 0, F6 = 0. The fault location locator determines that F1F2 = 1. Therefore, an open-circuit fault has occurred in switching transistor T1 of the inverter. Figure 4The image shows the current waveform corresponding to an open-circuit fault in transistor T2. The fault detector outputs: F1 = 0, F2 = 0, F3 = 0, F4 = 1, F5 = 1, F6 = 0. The fault location locator determines that F4F5 = 1. Therefore, an open-circuit fault has occurred in switching transistor T2 of the inverter. Figure 5 The image shows the current waveforms corresponding to an open-circuit fault in transistors T1 and T2. The fault detector outputs: F1 = 1, F2 = 1, F3 = 0, F4 = 1, F5 = 1, F6 = 0. The fault location locator outputs: F1F2F4F5 = 1. Therefore, an open-circuit fault has occurred in switching transistors T1 and T2 of the inverter. Figure 6 The diagram shows the current waveforms corresponding to open-circuit faults in transistors T1 and T4. The fault detector yields the following results: F1 = 1, F2 = 1, F3 = 0, F4 = 0, F5 = 0, F6 = 1. The fault location diagnostic unit determines that F1F2F6 = 1. Therefore, open-circuit faults have occurred in switching transistors T1 and T4 of the inverter. It can be seen that this invention can easily, quickly, and accurately diagnose open-circuit faults in brushless DC motor inverters.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for diagnosing open-circuit faults in a brushless DC motor based on phase current detection, characterized in that, Includes the following steps: Step 1: In each control cycle, sample the Hall sensor signal H of the brushless DC motor (2). A H B and H C The working interval signal S is calculated using the working interval detector (3). n where n = 1 to 6; Step 2: Sample the three-phase current values ​​of the brushless DC motor, and use the fault detector (4) to calculate the sum of the absolute values ​​of the phase currents of the two conducting phases i1 and the absolute value of the phase current of the other phase i2. By comparing i1 and i2, obtain the fault flag signal F. n where n = 1 to 6; Step 3: Based on the fault indicator signal F n The fault location of the inverter (1) switching transistor is determined by the fault location detector (5). Step 4: Output the inverter open circuit fault information through the diagnostic result output device (6).

2. The method for diagnosing open-circuit faults in a brushless DC motor based on phase current detection according to claim 1, characterized in that: In step 1, the brushless DC motor operating range signal S n The acquisition method is as follows: acquire the motor position signal H through a Hall sensor. A H B and H C Alternatively, the motor rotor position angle θ can be used to obtain the motor operating range signal S according to formula (1). n Alternatively, the motor operating range signal S can be obtained according to formula (2). n ; (1) (2) In the formula This represents the inverse logic of H, when H=0. =1, when H=1 =0.

3. The method for diagnosing open-circuit faults in brushless DC motors based on phase current detection according to claim 1, characterized in that: The fault flag signal F in step 2 n The acquisition method is as follows: First, the three-phase current i is collected through a current sensor. A i B and i C Then, i1 is calculated using formula (3), i2 is calculated using formula (4), and finally, the fault flag signal F is calculated using formula (5). n ; (3) (4) (5) In the formula i 1_max This represents the maximum value of i1 within a 360-degree electrical angle of motor rotation. For every 360-degree electrical angle of motor rotation, i... 1_max Updated once; in the formula This represents the inverse logic of S, when S=0. =1, when S=1 =0; "|" represents the OR operation.

4. The method for diagnosing open-circuit faults in a brushless DC motor based on phase current detection according to claim 1, characterized in that: The method for locating the fault location of the switching transistor in step 3 is as follows: (1) Single tube open circuit fault: If F1F2=1, T1 is open circuit fault; if F4F5=1, T2 is open circuit fault; if F3F4=1, T3 is open circuit fault; if F1F6=1, T4 is open circuit fault; if F5F6=1, T5 is open circuit fault; if F2F3=1, T6 is open circuit fault. (2) Open circuit fault in both tubes of the same bridge arm: If F1F2F4F5=1, T1 and T2 are open circuit faults; F1F3F4F6=1, T3 and T4 are open circuit faults; F2F3F5F6=1, T5 and T6 are open circuit faults. (3) Open circuit faults in the upper and lower arms of different bridge arms: If F1F2F6=1, T1 and T4 are open circuit faults; F1F2F3=1, T1 and T6 are open circuit faults; F3F4F5=1, T2 and T3 are open circuit faults; If F2F3F4=1, T3 and T6 are open circuit faults; F4F5F6=1, T2 and T5 are open circuit faults; F1F5F6=1, T4 and T5 are open circuit faults.

5. The method for diagnosing open-circuit faults in a brushless DC motor based on phase current detection according to claim 1, characterized in that: Step 4 outputs inverter open-circuit fault information through the diagnostic result output device, specifically as follows: Write the inverter open-circuit fault information into the corresponding flag variable or display it on the screen or digital tube, then F n Clear to zero, and for i 1_max Update; this step is performed once every 360 electrical degrees the motor rotates.

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