Motor drive system with switch fault diagnosis function and diagnosis method

Abstract

This invention discloses a motor drive system and diagnostic method with switch fault diagnosis capabilities. This method calculates the sector width of the SVPWM module and compares it with a set threshold. When the width exceeds the threshold, a corresponding switch fault indication signal is issued. This diagnostic method adjusts the diagnostic threshold in real time based on a given speed, providing good adaptability to variable speeds. It also utilizes an observer to monitor load torque in real time, reducing sensitivity to variable load conditions. The disclosed switch fault diagnosis method ensures rapid and accurate diagnosis without increasing the size and cost of additional testing equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor drive, and in particular relates to a method for diagnosing an open-circuit fault of a motor drive system. Background Art

[0002] Electric energy, thanks to its clean and environmentally friendly nature, is widely replacing primary energy sources such as hydraulic and pneumatic energy in more-electric and all-electric aircraft systems, and the proportion of electrical loads continues to increase. In the past two years, the market share of new energy vehicles has steadily increased, and research on core automotive electric drive technologies has also continued to grow. Therefore, whether in aerospace, new energy vehicles, or intelligent robotics, research on the operational reliability of motors and their drive systems is crucial for ensuring stable and reliable system operation and protecting the lives and property of drivers and passengers.

[0003] In actual operating conditions, power devices are prone to irreversible damage and failure due to frequent switching, overvoltage and overcurrent under transient conditions, limited overload capacity, and increased junction temperature during operation. According to statistics, 38% of power electronic converter failures are caused by damaged power devices. Therefore, quickly and accurately locating the faulty switch tube is crucial to improving the overall safety performance of the drive system operation. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for rapid diagnosis of switching tube faults in motor drive systems. This method utilizes a diagnostic algorithm designed based on mature hardware solutions from industrial applications, improving diagnostic speed while minimizing the size and cost of additional sensors. Improvements are also proposed to enhance adaptability to variable speed and load conditions, ensuring the reliability of the diagnostic algorithm and reducing false alarm rates.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] A motor drive system with a switch fault diagnosis function includes a power conversion circuit and a control circuit. The output end of the power conversion circuit is connected to the winding of the motor. The control circuit outputs a switch signal to control the opening and closing of the switch tube in the power conversion circuit. The control circuit includes a fault diagnosis module. The fault diagnosis module includes a sector width calculator. In the kth control cycle, the current time t is calculated. k Sector number N at the time k , and in the previous control cycle, time t k-1 Sector number N calculated when k-1 Compare, if N k =N k-1 , then the sector does not jump, and the sector number N of the k+1th control cycle is calculated cyclically. k+1 ; If N k ≠N k-1, then the sector jumps in the current control cycle, indicating that the sector number N k-1 End, sector number N k Start by calculating the sector number N k-1 Sector width Width N(k-1) =t k -t k-1 , sector width Width N(k-1) If it is greater than the threshold W, then the sector number N k-1 In response to a power tube failure, the control circuit outputs a drive signal to the power conversion circuit, causing the sector number N in the power conversion circuit to k-1 The corresponding phase switch tube is turned off.

[0007] The control circuit includes a load torque observer, which detects the mechanical angular velocity signal ω m With the quadrature axis current i q , get the current load torque observation value T L(k) and the observed value T at the previous moment L(k-1) If the absolute value of the difference is greater than the tolerance m, it is determined that a sudden change has occurred in the load torque, and the fault diagnosis module stops working.

[0008] The fault diagnosis module stops working and resumes working after a first period of time.

[0009] The control circuit further includes an SVPWM modulator that generates a PWM wave to drive the switch tubes of the power conversion circuit. The power conversion circuit is a three-phase full-bridge inverter, including a first bridge arm consisting of a first switch tube and a second switch tube, a second bridge arm consisting of a third switch tube and a fourth switch tube, and a third bridge arm consisting of a fifth switch tube and a sixth switch tube. The correspondence between the sector number and the diagnosis switch tube number is as follows:

[0010] When the sector number N is 3, the sector width Width N(k-1) Comparing the health status of the first switch tube with the threshold value to diagnose the health status of the first switch tube;

[0011] When the sector number N is 4, the sector width Width N(k-1) Comparing the health status of the second switch tube with the threshold value to diagnose the health status of the second switch tube;

[0012] When the sector number N is 5, the sector width Width N(k-1) comparing the health status of the third switch tube with the threshold value;

[0013] When the sector number N is 2, the sector width Width N(k-1) comparing the health status of the fourth switch tube with the threshold value;

[0014] When the sector number N is 6, the sector width Width N(k-1) comparing the health status of the fifth switch tube with the threshold value;

[0015] When the sector number N is 1, the sector width Width N(k-1) The health condition of the sixth switch tube is diagnosed by comparing the health condition with the threshold.

[0016] The control circuit further includes a position sensor and a current sensor. The position sensor detects the electrical angle of the motor, and the current sensor detects the three-phase current of the motor.

[0017] The control circuit further includes a speed loop and a current loop. The speed loop receives actual speed feedback and speed reference obtained by converting the electrical angle, and outputs a quadrature-axis current reference to the current loop after adjustment by the speed regulator.

[0018] The above-mentioned current loop receives current feedback from the motor winding, outputs a given voltage after being regulated by the quadrature-axis current regulator and the direct-axis regulator, and generates a switch drive signal in the power conversion circuit through the SVPWM modulator.

[0019] The present invention also provides a method for quickly diagnosing a switch failure in a motor drive system, comprising the following steps:

[0020] Step S1: In the k-1th control cycle, calculate the current time t k-1 Sector number N at the time k-1 , in the kth control cycle, calculate the current time t k Sector number N at the time k , if N k =N k-1 , then the sector does not jump, and the sector number N of the k+1th control cycle is calculated cyclically. k+1 , until the sector number jumps, the sector number N of the k+mth control cycle k+m , N k+m ≠N k-1 Calculate sector number N k-1 Sector width Width N(k-1) =t k+m -t k-1 ; If N k ≠N k-1 , then the sector jumps in the current control cycle, indicating that the sector number N k-1 End, sector number N k Start by calculating the sector number N k-1 Sector width Width N(k-1) =t k -t k-1 ;

[0021] Step S2, determining whether the load torque has a sudden change; if the load torque has not a sudden change, executing step S4; if the load torque has a sudden change, executing step S3;

[0022] Step S3: After the load changes suddenly for a first period of time, step S4 is executed;

[0023] Step S4, compare sector width Width N(k-1) The size of the threshold W, the sector width Width N(k-1) If the value is greater than the threshold value W, a fault diagnosis signal F is issued. i(i＝1,2,3,4,5,6) =1, indicating that an open circuit fault occurs in the i-th switch tube of the power converter.

[0024] The above threshold W setting method is:

[0025]

[0026] Among them, n ref Indicates the given speed of the motor, Δn indicates the actual speed pulsation, n p Indicates the number of motor pole pairs.

[0027] In the above step S1, the sector number remains unchanged in the same control cycle.

[0028] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0029] 1. The present invention uses sector width as the basis for diagnosis and utilizes the system's own electrical signals to complete diagnosis. Compared with the solution of adding sensors to detect faults, it greatly reduces the system volume and hardware costs while still ensuring rapid diagnostic performance.

[0030] 2. The present invention introduces a load torque observer and adjusts the diagnosis threshold according to the actual speed, thereby improving the reliability of fault diagnosis and reducing the probability of false alarms. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a block diagram of a permanent magnet motor vector control method using a fast switch tube fault diagnosis method according to the present invention.

[0032] Figure 2 It is a topological diagram of the power converter of the present invention.

[0033] Figure 3 It is a schematic diagram of the corresponding relationship between the sector number and the detected power tube number of the present invention.

[0034] Figure 4 This is a flow chart of the method for quickly diagnosing switch tube faults of the present invention. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be interpreted as limiting the present invention.

[0036] Figure 2 The figure shows a specific embodiment of a power conversion circuit in a motor drive system, specifically a voltage-type three-phase bridge inverter circuit, including a power conversion circuit 21 and a control circuit 23. The output end of the power conversion circuit 21 is connected to the winding of the motor 22. The control circuit 23 outputs a switching signal to control the switching tubes S1-S6 of the power conversion circuit 21 to turn on / off by implementing a control algorithm. The power conversion circuit 21 converts the DC power supply U dc The power is inverted and provided to the motor 22. In the embodiment of the present invention, the power conversion circuit 21 is a three-phase full-bridge inverter circuit, the midpoint of the bridge arm of the three-phase full-bridge inverter circuit is connected to the winding of the motor 22, and the three-phase winding of the motor 22 is star-connected.

[0037] When the motor 22 runs smoothly, the speed loop closed-loop regulation performance is good, and the speed fluctuation range of the motor 22 is small. Therefore, the stator voltage vector rotates at a uniform speed, and the time it takes to rotate through each sector is the same. Figure 3 Sector number N switches periodically in the order of 3, 1, 5, 4, 6, and 2, with time as the horizontal axis, and each sector has the same width. When an open-circuit fault occurs in a single power device in a phase bridge arm, the current flowing through the device is zero. Therefore, the torque output capacity decreases during that half-cycle, the electromagnetic torque is less than the load torque, the motor decelerates, and the stator voltage vector rotates at a slower speed. The width of the sector participating in voltage vector modulation when the switch is in the on state increases, which serves as the basic principle of the diagnostic algorithm disclosed in this invention. The correspondence between power device damage and sector number increase is shown in Table 1. If the lower switch S2 of phase A is open-circuited, the corresponding sector N = 4 increases in width.

[0038] Table 1 Correspondence between power device damage and width increase sector

[0039]

[0040] The theoretical counting threshold is set to correspond to the theoretical width of the sector. To improve the rapidity of diagnosis, real-time counting starts from the rising edge of the sector number jump, that is, counting starts from N=4. Once the count value is greater than the theoretical counting threshold W, the fault diagnosis flag is 1. In order to achieve self-adjustment of the diagnostic threshold at different speeds, the expression of the theoretical counting threshold W is:

[0041]

[0042] Among them, n ref Indicates the given speed of the motor, Δn indicates the actual speed pulsation, np Indicates the number of motor pole pairs.

[0043] Load torque mutation is another factor that affects the motor speed. In order to distinguish whether the factor causing the speed change is load torque mutation or switch failure, a reduced-order observer is introduced to observe the load torque in real time. The state equation of speed and load torque is:

[0044]

[0045] y=Cx

[0046] Where x = [ω m T L ] T , u=i q , y=ω m , C=[1 0].

[0047] The load torque observer is designed as

[0048]

[0049]

[0050] in, L=[k1 k2] T , ω m Indicates the actual value of mechanical speed. represents the estimated mechanical speed, represents the estimated value of load torque, J represents the moment of inertia, n p Indicates the number of motor pole pairs, ψ f represents the permanent magnet flux, i q represents the motor quadrature axis current, k1, k2 are constants. The actual value of the state variable is subtracted from the estimated value to obtain

[0051]

[0052] in, The two extremes are

[0053]

[0054] Let s1=s2=-l(l>0), then

[0055]

[0056] Therefore, it is necessary to finally balance the estimation error convergence speed and the steady-state control accuracy of the system and design the parameter l to achieve the goal of load torque observation.

[0057] The control algorithm of the control circuit 33 is a permanent magnet motor vector control method for fast diagnosis of switch tube failure, and the block diagram is as follows: Figure 1 As shown. Combined Figure 3 The position sensor 135 obtains the rotor angle of the motor 12, and the speed calculator 136 outputs the angular velocity feedback ω m , the motor speed feedback n and winding current i are obtained by unit conversion 137 a / i b / i c Measured by current sensors CT1 / CT2 / CT3. Mechanical angular velocity signal ω m With the quadrature axis current i q At the same time, the load torque observer 1381 is input to obtain the current load torque observation value T L(k) and the observed value T at the previous moment L(k-1) If the absolute value of the difference is greater than the tolerance m, that is, |T L(k) -T L(k-1) |>m, it is determined that the load torque has a sudden change, and the judgment module 1382 sends a diagnosis enable signal Flag=1, and does not perform fault diagnosis; if the absolute value of the difference is less than or equal to the tolerance m, that is, |T L(k) -T L(k-1) |≤m, the load torque remains unchanged, the judgment module 1382 sends a diagnosis enable signal Flag=0 to perform fault diagnosis.

[0058] If the diagnosis enable signal Flag=1, it is a non-fault detection stage, and the control circuit 13 uses the following specific embodiment to control and output the drive signal of the SVPWM modulator 1341 to the power conversion circuit 11:

[0059] The speed loop 131 receives the speed reference n* and the speed feedback n, and outputs the q-axis current reference i after being regulated by the speed regulator 1311. q *, a preferred embodiment of the speed regulator 1311 is a proportional-integral regulator.

[0060] The current loop 132 is a d, q axis current closed loop, which accepts the quadrature axis current given i q * and the direct axis given current i d *=0, and quadrature axis current feedback i q and direct-axis current feedback i d , winding current i a / i b / i c After being transformed by the coordinate converter 1323, the quadrature axis current feedback i is output. q and direct-axis current feedback i d , given quadrature axis current i q * and quadrature axis current feedback i qAfter being regulated by the quadrature axis current regulator 1321, the output quadrature axis voltage is given as u q *, direct axis given current i d * and direct-axis current feedback i d After being regulated by the direct axis current regulator 1322, the output direct axis voltage is given as u d *, given quadrature axis voltage u q * and the direct axis voltage given by u d *After Park inverse transformation 133, the d, q axes are transformed into the α, β coordinate system and then input into the SVPWM modulator 1341 to generate a PWM wave to drive the switch tube in the power conversion circuit 11.

[0061] If the diagnosis enable signal Flag=0, corresponding to the fault detection phase, the fault diagnosis module 138 is executed to obtain the sector width Width calculated by the sector width calculation 1383. N(k-1) , and the size is judged in the threshold comparator 1384. If the sector width Width N(k-1) If the value is greater than the threshold value W, the corresponding power tube fault diagnosis signal F is issued. i =1, the control circuit 13 outputs the driving signal of the switch signal assignment module 1342 to the power conversion circuit 11, so that the control signals of the two switch tubes of the fault phase are both set to low. The corresponding relationship between the sector number N and the switch tube number i is as follows: Figure 3 shown.

[0062] like Figure 4 FIG2 is a flow chart of a method for diagnosing a fault of a switch tube in a motor drive system provided by the present invention. The method for diagnosing a fault of a switch tube in a motor drive system includes the following steps:

[0063] Step S1: In the k-1th control cycle, calculate the current time t k-1 Sector number N at the time k-1 , in the kth control cycle, calculate the current time t k Sector number N at the time k , if N k =N k-1 , then the sector does not jump, and the sector number N of the k+1th control cycle is calculated cyclically. k+1 , until the sector number jumps, the sector number N of the k+mth control cycle k+m , N k+m ≠N k-1 Calculate sector number N k-1 Sector width Width N(k-1) =t k+m -t k-1 ; If N k ≠N k-1 , then the sector jumps in the current control cycle, indicating that the sector number Nk-1 End, sector number N k Start by calculating the sector number N k-1 Sector width Width N(k-1) =t k -t k-1 ;

[0064] Step S2: determine whether the load torque changes suddenly.

[0065] Get the motor quadrature axis current i q and mechanical speed ω m , input the load torque observer to obtain the current load torque observation value T L(k) and the observed value T at the previous moment L(k-1) If the absolute value of the difference is less than or equal to the tolerance m, it is determined that the load torque has not undergone a sudden change, and step S4 is executed. L(k) -T L(k-1) |>m, it is determined that the load torque has suddenly changed, and step S3 is executed;

[0066] Step S3: Delay time t. The method of determining t is related to the dynamic performance of the motor speed loop regulation. The value of t can be slightly greater than the speed regulation time.

[0067] Step S4, perform fault diagnosis, and compare the sector width Width in real time N(k-1) With the size of the threshold W, once the sector width Width N(k-1) If the value is greater than the threshold value W, a fault diagnosis signal F is issued. i(i =1,2,3,4,5,6)=1, indicating that an open circuit fault occurs in the i-th switch tube of the power converter.

[0068] The speed at which the sector number changes is directly related to the current cycle and whether a switch failure has occurred. Therefore, capturing sector jumps under low motor speed conditions is relatively easy. The speed of sector changes increases as the motor speed increases. By dividing a current cycle into extremely short control cycles, the present invention determines whether a sector has jumped within each control cycle. This makes it extremely sensitive to sector jumps and can quickly capture the start and end times of the same sector, thereby improving the accuracy of sector width calculations. Therefore, the present invention is particularly suitable for high-speed motor applications.

[0069] The above embodiments are only for illustrating the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention fall within the protection scope of the present invention.

Claims

1. A motor drive system with a switch fault diagnosis function, comprising a power conversion circuit and a control circuit, wherein the output end of the power conversion circuit is connected to the winding of the motor, and the control circuit outputs a switching signal to control the opening and closing of the switch tube in the power conversion circuit, characterized in that: The control circuit includes a fault diagnosis module, which includes a sector width calculator. In the fault detection phase, the fault diagnosis module is executed, the SVPWM modulator outputs the sector number N to the sector width calculator, and obtains the sector width Width calculated by the sector width calculator. N(k-1) , perform size judgment in the threshold comparator; In the kth control cycle, calculate the current time t k Sector number N at the time k , and in the previous control cycle, time t k-1 Sector number N calculated when k-1 Compare, if N k =N k-1 , then the sector does not jump, and the sector number N of the k+1th control cycle is calculated cyclically. k+1 ; If N k ≠N k-1 , then the sector jumps in the current control cycle, indicating that the sector number N k-1 End, sector number N k Start by calculating the sector number N k-1 Sector width Width N(k-1) =t k -t k-1 , sector width Width N(k-1) If it is greater than the threshold W, then the sector number N k-1 In response to a power tube failure, the control circuit outputs a drive signal to the power conversion circuit, causing the sector number N in the power conversion circuit to k-1 The corresponding phase switch tube is turned off; The control circuit further includes a load torque observer, which detects a mechanical angular velocity signal ω m With the quadrature axis current i q , get the current load torque observation value T L(k) and the observed value T at the previous moment L(k-1) If the absolute value of the difference is greater than the tolerance m, it is determined that a sudden change has occurred in the load torque, and the fault diagnosis module stops working.

2. The motor drive system with switch fault diagnosis function according to claim 1, characterized in that: The fault diagnosis module stops working and resumes working after a first time period.

3. The motor drive system with switch fault diagnosis function as claimed in claim 2, characterized in that: The control circuit further includes an SVPWM modulator, which generates a PWM wave to drive a switch tube of a power conversion circuit. The power conversion circuit is a three-phase full-bridge inverter, including a first bridge arm consisting of a first switch tube and a second switch tube, a second bridge arm consisting of a third switch tube and a fourth switch tube, and a third bridge arm consisting of a fifth switch tube and a sixth switch tube. The corresponding relationship between the sector number and the diagnosis switch tube number is as follows: When the sector number N is 3, the sector width Width N(k-1) Comparing the health status of the first switch tube with the threshold value to diagnose the health status of the first switch tube; When the sector number N is 4, the sector width Width N(k-1) Comparing the health status of the second switch tube with the threshold value to diagnose the health status of the second switch tube; When the sector number N is 5, the sector width Width N(k-1) comparing the health status of the third switch tube with the threshold value; When the sector number N is 2, the sector width Width N(k-1) comparing the health status of the fourth switch tube with the threshold value; When the sector number N is 6, the sector width Width N(k-1) comparing the health status of the fifth switch tube with the threshold value; When the sector number N is 1, the sector width Width N(k-1) The health condition of the sixth switch tube is diagnosed by comparing the health condition with the threshold.

4. The motor drive system with switch fault diagnosis function as claimed in claim 2, characterized in that: The control circuit further includes a position sensor and a current sensor. The position sensor detects the electrical angle of the motor, and the current sensor detects the three-phase current of the motor.

5. The motor drive system with switch fault diagnosis function as claimed in claim 4, characterized in that: The control circuit further includes a speed loop and a current loop. The speed loop receives actual speed feedback and speed reference obtained by converting the electrical angle, and outputs a quadrature-axis current reference to the current loop after adjustment by a speed regulator.

6. The motor drive system with switch fault diagnosis function as claimed in claim 5, characterized in that: The current loop receives current feedback from the motor winding, outputs a given voltage after being regulated by the quadrature-axis current regulator and the direct-axis regulator, and generates a switch drive signal in the power conversion circuit through the SVPWM modulator.

7. A method for rapid diagnosis of switch failure in a motor drive system, characterized in that: The steps include: Step S1, space vector pulse width modulation output voltage vector pulse width signal, obtain sector width Width N(k-1) , compare with the threshold value; in the k-1th control cycle, calculate the current time t k-1 Sector number N at the time k-1 , in the kth control cycle, calculate the current time t k Sector number N at the time k , if N k =N k-1 , then the sector does not jump, and the sector number N of the k+1th control cycle is calculated cyclically. k+1 , until the sector number jumps, the sector number N of the k+mth control cycle k+m , N k+m ≠N k-1 Calculate sector number N k-1 Sector width Width N(k-1) =t k+m -t k-1 ; If N k ≠N k-1 , then the sector jumps in the current control cycle, indicating that the sector number N k-1 End, sector number N k Start by calculating the sector number N k-1 Sector width Width N(k-1) =t k -t k-1 ; Step S2, determining whether the load torque has a sudden change; if the load torque has not a sudden change, executing step S4; if the load torque has a sudden change, executing step S3; Step S3: After the load changes suddenly for a first period of time, step S4 is executed; Step S4, compare sector width Width N(k-1) The size of the threshold W, the sector width Width N(k-1) If the value is greater than the threshold value W, a fault diagnosis signal F is issued. i(i＝1,2,3,4,5,6) =1, indicating that an open circuit fault occurs in the i-th switch tube of the power converter.

8. A method for rapid diagnosis of switch failure in a motor drive system according to claim 7, characterized in that: The threshold W setting method: Among them, n ref Indicates the given speed of the motor, Δn indicates the actual speed pulsation, n p Indicates the number of motor pole pairs.

9. A method for rapid diagnosis of switch failure in a motor drive system according to claim 8, characterized in that: In the step S1, the sector number remains unchanged in the same control cycle.

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