A method for locating a power tube circuit breaker fault in a motor drive system

Abstract

The present invention discloses a method for locating a power tube circuit breaker fault in a motor drive system. The method is mainly aimed at the motor drive system. When a three-phase bridge arm power tube fails, there is a difference between the actual value and the ideal value of the center point voltage to ground, that is, the center point voltage residual is not zero, and this fault feature is used to detect and locate the three-phase bridge arm power tube fault. The present invention reversely deduce the actual value of the three-phase bridge arm center point voltage to ground by establishing a mathematical model and using known motor parameters, and the fault detection and positioning functions can be realized without adding additional voltage sensors.

Description

Technical Field

[0001] The invention discloses a method for locating a power tube circuit breaker fault in a motor drive system, and belongs to the field of inverter fault diagnosis. Background Art

[0002] Power electronics technology is one of the important branches in the field of energy and electricity, and voltage inverters play an important role in electrical energy conversion. However, in the process of energy conversion, factors such as aging, overheating, overload operation caused by excessive load, and complex external working conditions of key components such as the power tube of the inverter often have a greater impact, and even equipment paralysis. In the draft national power system fault diagnosis standard, failures of sensors, power switch tubes, capacitors, etc. are classified as fatal failures. According to the survey results, 34% of power equipment failures occur in semiconductor devices.

[0003] Therefore, the use of more perfect fault diagnosis technology is an effective means to improve the reliability and safety of systems and equipment, and it is more meaningful to study and apply it. Through additional means to detect and accurately locate the faults of the inverter system, timely maintenance or online remediation can be achieved, the system failure rate can be minimized, the unexpected downtime of the system can be reduced, and the system can be ensured to operate safely and reliably. Taking the three-phase voltage inverter system as the research object, the current or voltage signal characteristics of the power tube open circuit fault of the three-phase inverter are studied, which has certain theoretical significance and engineering application value. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a method for locating a power tube open circuit fault in a motor drive system.

[0005] The method utilizes the difference between the actual value and the ideal value of the center point voltage to ground when a three-phase bridge arm power tube fails, that is, the center point voltage residual is not zero, and uses this fault feature to detect and locate the three-phase bridge arm power tube fault.

[0006] The technical solution is as follows:

[0007] 1) The actual voltage deviation Δu of the X phase center point is derived by the formula X The ideal deviation of the Y-phase center voltage is Δu' Y The relationship between Δu' Y =Δu Y -Δu X .

[0008] Among them, X and Y can be A, B, C and are not equal, Expected midpoint voltage: SX =D X *2-1, when the lower tube is turned on, the value is -1, and when the upper tube is turned on, the value is 1; the power tube switch signal D X , when the lower tube is turned on, the value is 0, and when the upper tube is turned on, the value is 1.

[0009] 2) By studying the actual deviation Δu of the center point voltage under different faults of each phase X , to derive the ideal deviation of the center point voltage Δu' Y , to determine its fault characteristics under different faults.

[0010] 3) When the voltage vector is a zero voltage vector, substitute the collected current and induced electromotive force into the formula:

[0011]

[0012]

[0013]

[0014] When the motor is an asynchronous motor, e a [K] = e b [K] = e c [K]=0

[0015] 4) By changing Δu' A [K], Δu' B [K], Δu' C [K] can be compared and the fault can be located by combining with the fault diagnosis table.

[0016] 5) On this basis, when a double-tube fault occurs, the fault locations of the two tubes will be detected successively. After at most half a current fundamental wave cycle, all the open circuit fault locations of the power tubes of the three-phase three-bridge-leg inverter can be detected.

[0017] Table 1 Fault diagnosis table

[0018]

[0019]

[0020] The beneficial effects are as follows:

[0021] The method of the present invention can locate the faulty power tube even after the inverter fails. In addition, it has the following advantages:

[0022] Advantage I—This diagnostic method does not require the installation of additional voltage sensors. The true value of the center-point voltage to ground can be obtained by using known motor parameters and current.

[0023] Advantage II—This diagnostic method can locate a total of 21 types of faults, including single-tube fault, single-phase double-tube fault, double-tube fault on the same side and double-tube fault on the opposite side. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the ideal deviation simulation waveform of the three-phase center point voltage;

[0025] Figure 2 is the three-phase current waveform;

[0026] Figure 3 It is a circuit diagram of the present invention. DETAILED DESCRIPTION

[0027] The present invention proposes a method for locating a power tube circuit breaker fault in a motor drive system. The method utilizes the fact that when a three-phase bridge arm power tube fails, there is a difference between the actual value and the ideal value of the center point voltage to ground, that is, the center point voltage residual is not zero, and uses this fault feature to detect and locate the three-phase bridge arm power tube fault.

[0028] The technical solution is as follows:

[0029] X phase center point voltage u X is the voltage from the midpoint of the X-phase bridge arm to ground.

[0030] Assume that the power tube switch signal D X , when the lower tube is turned on, the value is 0, when the upper tube is turned on, the value is 1, and X can be A, B, or C.

[0031] Expected value of center point voltage: Among them, V dc is the bus voltage, S X =D X *2-1, the value is -1 when the lower tube is turned on, and the value is 1 when the upper tube is turned on.

[0032] Δu X The actual deviation of the X-phase center point voltage is:

[0033]

[0034] 1) The actual voltage deviation Δu of the X phase center point is derived by the formula X The ideal deviation of the Y-phase center voltage is Δu' Y The relationship between Δu' Y =Δu Y -Δu X . Among them, X and Y can be A, B, C and X≠Y.

[0035] 2) By studying the actual deviation Δu of the center point voltage under different faults of each phase X, to derive the ideal deviation of the center point voltage Δu' Y , to determine its fault characteristics under different faults.

[0036] 3) When the voltage vector is a zero voltage vector, substitute the collected current and induced electromotive force into the formula:

[0037]

[0038]

[0039]

[0040] Among them, R and L are the equivalent resistance and equivalent inductance of the single-phase winding of the motor, T is the sampling period, i x [K] is the phase current of phase X at time K, e x [K] is the magnitude of the induced electromotive force of phase X at time K. When the motor is an asynchronous motor, e x [K] = 0, is the expected value of the center point voltage of phase X at time K, where X can be A, B or C.

[0041] 4) By changing Δu' A [K], Δu' B [K], Δu' C [K] can be compared and the fault can be located by combining with the fault diagnosis table.

[0042] 5) On this basis, when a double-tube fault occurs, the fault locations of the two tubes will be detected successively. After at most half a current fundamental wave cycle, all the open circuit fault locations of the power tubes of the three-phase three-bridge-leg inverter can be detected.

[0043] Table 1 Fault diagnosis table

[0044]

[0045]

[0046] The technical solution of the present invention is described in detail below:

[0047] When the upper bridge arm power tube of phase A and the lower bridge arm power tube of phase B fail, when the voltage vector is a zero voltage vector, substitute the collected current into the formula:

[0048]

[0049]

[0050]

[0051] When the motor is an asynchronous motor, ea [K] = e b [K] = e c [K]=0.

[0052] When the trigger signal is 1, 1, 1 and i a ≥0

[0053]

[0054] Comply with Δu' A =-Δu' B ≠0; Δu' C =0, it can be inferred that the upper bridge arm of phase A is faulty.

[0055] When the trigger signal is 0, 0, 0; i b ≤0

[0056]

[0057] Comply with Δu' B =-Δu' C ≠0; Δu' A =0, it can be inferred that the lower bridge arm of phase B is faulty.

[0058] Figure 3 is a circuit diagram of the present invention, Figure 1 is the ideal deviation of the three-phase center voltage Δu' A , Δu' B , Δu' C The simulation waveform, Figure 2 It is the three-phase current waveform. It can be seen from the figure that at 0.3 seconds, the power tube of the upper bridge arm of phase A is disconnected, Δu' A =-Δu' B ≠0, Δu' C =0,i a ≥0; at 0.4 seconds, the power tube of the lower bridge arm of phase B is disconnected, Δu' B =-Δu' C ≠0, Δu' A =0,i b ≤0. The method of the present invention can effectively diagnose the power tube fault of the three-phase three-bridge-arm inverter.

[0059] The beneficial effects of the present invention are as follows: the method of the present invention can locate the faulty power tube even after the inverter fails. In addition, it also has the following advantages:

[0060] 1. This diagnostic method does not require the installation of additional voltage sensors. The true value of the center point to ground voltage can be obtained by using known motor parameters and current;

[0061] 2. This diagnostic method can locate a total of 21 types of faults, including single-tube fault, single-phase double-tube fault, double-tube fault on the same side and double-tube fault on the opposite side.

[0062] The specific implementation cases described in the present invention are only preferred implementation cases of the present invention and are not intended to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made according to the content of the patent application scope of the present invention should be regarded as the technical scope of the present invention.

Claims

1. A method for locating a power tube circuit breaker fault in a motor drive system, characterized in that: The fault location method comprises the following steps: 1) The actual deviation of the X-phase center point voltage is derived by the formula u X The ideal deviation from the Y-phase center voltage The relationship between ; Among them, X and Y are A, B, C and are not equal, ; X phase center point voltage u X is the voltage between the midpoint of the X-phase bridge arm and the ground; Expected value of center point voltage: , when the lower tube is turned on, the value is -1, and when the upper tube is turned on, the value is 1; the power tube switch signal D X , when the lower tube is on, the value is 0, and when the upper tube is on, the value is 1; 2) By studying the actual deviation of the center point voltage under different faults of each phase u X , to derive the ideal deviation of the center point voltage , to determine its fault characteristics under different faults; 3) When the voltage vector is a zero voltage vector, substitute the collected current and induced electromotive force into the formula: Among them, R and L are the equivalent resistance and equivalent inductance of the single-phase winding of the motor respectively, T is the sampling period, is the phase current of phase X at time K, is the magnitude of the induced electromotive force of phase X at time K, is the expected value of the center point voltage of phase X at time K, X is A, B, C; 4) By Compare and locate the fault by combining with the fault judgment table; 5) On this basis, when a double-tube fault occurs, the fault locations of the two tubes will be detected successively; after at most half a current fundamental wave cycle, all the circuit-breaking fault locations of the power tubes of the three-phase three-bridge-leg inverter can be detected.

2. A method for locating a power tube circuit breaker fault in a motor drive system according to claim 1, characterized in that: When the motor is an asynchronous motor, .

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